-------
;CREEN, WEDGEWIRE FACT SHEET 3.1.17
Description - A device onto which wastewater is directed across an inclined stationary screen or a drum screen of
uniform sized openings. Solids are trapped on the screen surface while the wastewater flows through the openings.
The solids are moved either by gravity (stationary) or by mechanical means (rotating drum) to a collecting area
for discharge. Stationary screens introduce the wastewater as a thin film flowing downward with a minimum of
turbulence across the wedgewire screens, which is generally in three sections of progressively flatter slope. The
drum screen employs the same type of wedgewire wound around its periphery. Wastewater is introduced as a thin
film near the top of the drum and flows through the hollow drum and out the bottom. The solids retained by the
peripheral screen follow the drum rotation until removed by a doctor blade located at about 120 from the intro-
duction point.
Common Modifications - Wedgewire spacing can be varied to best suit the application. For municipal wastewater
applications spacings are generally between 0.01 and 0.06 inches (0.25 to 1.5 mm). Inclined screens can be housed
in stainless steel or fiberglass; wedgewires may be curved or straight; the screen face may be a single multi-
angle unit, three separate multi-angle pieces, or a single curved unit. Rotary screens can have a single rotation
speed drive or a variable speed drive.
Technology Status - In use in industry since 1965 and in municipal wastewater treatment since 1967. Over 100
installations to date.
Applications - Stationary and rotary drum screens are ideally suited and usually employed after bar screens and
prior to grit chambers. They have also been employed for primary treatment, scum dewatering, sludge screening,
and digester cleaning and for storm water overflow treatment. Generally, the rotary drum unit is preferred where
grease problems are evident due to the increased frequency of cleaning required for stationary units.
Limitations - Require regular cleaning and prompt residuals disposal.
Typical Equipment/No. Mfrs.(23) - Screen systems/3
Performance - Screenings removed by fine screens (.01 to .06 in.) have amounted to approximately 1 to 2 yd /Mgal
of wastewater treated. Head loss can be 4 to 8 ft. Pollutant removals are:
Pollutant Typical Percent Removal
BOD5 to 20
SS 5 to 25
Residuals Generated - Solids trapped on the screen surface (1 - 2 yd /Mgal)
Design Criteria - Screening of raw wastewater - (0.05 - 36 Mgal/d)
Parameter Stationary Rotary Drum
Screen opening 0.01 - 0.06 in 0.01 - 0.06 in
Head required 4 - 7 ft 2.5 - 4.5 ft
Space required 10 - 750 ft 10 - 100 ft
Motor size - 0.5 - 3 hp
Unit Process Reliability - Very high reliability for process and mechanical areas when maintained.
Environmental Impact - Air: Can create odors if screenings are not disposed of properly. Land: Practically nil.
Screenings are generally disposed of in a landfill or by incineration. Water: None
References - 3, 7, 22, 27, 39, 52, 53, 99
A-116
-------
SCREEN, WEDGEWIRE
FACT SHEET 3.1.17
FLOW DIAGRAM
Feed
Sludge
Water Level
Influent
Effluent
ENERGY NOTES - Energy requirements of the stationary screens are dependent upon the head loss through the screen
system which may amount to 4 to 8 ft TDK. Energy requirements are kWh/yr = 1900 (Mgal/d X TDK) at a wire to water
efficiency of 60 percent. With a representative head of 4.5 ft, 8,550 kWh/yr would be required per Mgal/d.
Operation of rotary drum units requires about 3,300 kWh/yr for up to 1 Mgal/d; 5,000 kWh/yr for 1 to 6 Mgal/d;
10,000 to 20,000 kWh/yr for 6 to 8 Mgal/d; and about 2,000 kWh/yr/Mgal/d for higher flows in addition to
pumping energy for 2.5 to 4.5 ft of static head.
COSTS* - Assumptions: Last quarter 1978 dollars. ENR Index = 2860
Construction cost includes wedgewire stainless steel screen 0.06 inch opening; equipment and installation,
including electrical. Equipment provides suitable weirs for flow control.
Cost does not include flumes or piping for effluent or sludge, or pumping equipment.
Operation cost based on labor costs at $7.50/h; power at $0.02/kWh; pumping head for stationary screen
4.5 Ft.
CONSTRUCTION COST
OPERATION & MAINTENANCE COST
Q
~0
5 001
0001
-- — 1
=
a^
Stati
- = :
onar
!
mi
f
/
Sc:
/
H
---±
1:'
,
--
--'-
>k/
f'l1-
''—?
S
Rotary Screen
/
-/
/
*/5
7 I
t
i
1 0
I
Q 0 1
8
•s 001
0001
Stationary Screen>
Rotary Screen
.1 1.0 10.0 100
Wastewater Flow, Mgal/d
REFERENCES - 3, 99
*To convert construction cost to capital cost see Table A-2.
1.0 10.0
Wastewater Flow. Mgal/d
100
A-117
-------
AMMONIA STRIPPING
FACT SHEET 4.1,1
Description - Ammonia Stripping is a simple desorption process used to lower the ammonia content of a wastewater
stream. In the process, wastewater at elevated pH is pumped to the top of a packed tower with a countercurrent
flow of air drawn through the bottom openings.
into the air stream which is then discharged to the atmosphere.
Free ammonia (NHJ is stripped from the falling water droplets
Lime or caustic soda is added prior to the stripping to raise the pH of the wastewater to the range of 10.8 to
11.5 converting essentially all ammonium ions to ammonia gas which can be stripped by air. Process controls
required for the operation are the proper pH adjustment of the influent wastewater, and maintenance of proper air
and water flows.
Ammonia removal efficiency is highly dependent on air temperature and air/water ratios. As the air temperature
decreases, the efficiency drops significantly. The most common operating problem of this process is the occa-
sional formation of calcium carbonate scale. The influent should always be clarified before stripping.
Common Modifications - Tower packing materials, plastic and wood; operation of the stripping gas in a closed
system with an ammonia absorption unit for removal of the CO from the stripping gas stream to reduce scaling
problems; reclamation of ammonia from the closed cycle absorption unit; use of high pH holding ponds, followed by
a cross flow spray tower and final removal of the residual ammonia by breakpoint chlorination.
Technology Status - The process is considered fully demonstrated but not widely used.
Applications - Good for wastewater with high ammonia content (more than 10 mg/1). For higher ammonia content
(more than 100 mg/1), it may be economical to use alternate ammonia removal techniques. See Fact Sheet No. 4.1.2.
Limitations - Poor efficiency in cold weather locations (0 - 10 C). Cannot operate in freezing conditions 3
(unless sufficient heated air is available). Ammonia is discharged to atmosphere usually at low level (6 mg/m ).
This may be objectionable in certain locations. Nitrite, nitrate and organic nitrogen are not removed. Poor
efficiency when ammonia concentration is low (less than 10 mg/1). Scale formation can be removed hydraulically
in most cases but not in all, resulting in a need to pilot test at most locations.
Typical Equipment - Stripping tower closely resembles a conventional cooling tower, with 24 manufacturers (77).
Performance - The operation is unaffected by toxic compounds which can disrupt the performance of a biological
system.However, volatile toxics will be stripped during the process. Operating efficiency is highly dependent
on air temperature as follows:
Air Temperature
10 C
20°C
NH Removal Efficiency
75 percent
90 to 95 percent
Efficiency may be reduced by severe scaling in the tower.
ammonia concentrations are in the 1 to 3 mg/1 range.
However, under normal operating conditions, residual
Chemicals Required - Lime or caustic soda is needed to raise the pH of the wastewater to the range of 10.8 to
11.5. For wastewater with high calcium content, an inhibiting polymer may be added to ease the scaling problem.
Effluent from the stripping may need pH readjustment to neutral condition with an acid (H2S°4 at 1-75 parts for
one part of lime added) or recarbonation followed by clarification.
Design Criteria -
Wastewater loading: 1 to 2 gal/min/ft 3
Stripping air flow rate: 300 to 500 ft /gal
Packing depth: 20 to 25 ft
pH of wastewater: 10.8 to 11.5
Air pressure drop: 0.015" to 0.019"
of water/ft
Packing material: plastic or wood
packing spacing: approx. 2" horizontal and
vertical
Providing: uniform water distribution
Providing: scale removal and clean-up
Land requirement: small
Reliability - The operation is simple and reliable, and not subject to upset by the wastewater fluctuation, if pH
and air temperature are stable. Occasional clean-up of scale may be required.
Environmental Impact -
Air: Normal operational discharge of less than 6 mg/m does not present an odor problem. NH3 washout to downwind
water bodies; minor noise pollution from motor, fan and water splashing.
References - 3, 4, 23, 28, 31, 39, 44, 47
A-118
-------
AMMONIA STRIPPING
FACT SHEET
FLOW DIAGRAM -
Outlet
Water Inlet
Air Inlet
Outlet
Drift
.Eliminators
'Distribution
System
Air Inlet
Water Collecting
Basin
Countercurrent Tower
ENERGY NOTES (4) - Pumping energy requirements can be approximated by the use of the following equation:
kwh/yr = 1140 (Mgal/d x ft of total head)
Wire to water Efficiency
For a TDK of 50 feet, a wire to water efficiency of 60 percent and a 1 Mgal/d flow would amount to 95,000
kwh/yr. Assuming a fan energy requirement of 0.0765 hp/1,000 gal (400 ft /gal), a 1 Mgal/d facility would
require 500,000 kwh/yr, resulting in a total energy requirement of 600,000 kwh/yr
COSTS* - Assumptions: ENR 2475, Sept 1976
Design Assumptions: Tower, 20 ft high, packed with 1/2 in diameter Schedule 80 Pvc pipe at 3 in centers
horizontally with alternate layers placed at right angles at 2 in centers vertically; Pump, 50 ft TDH; Loading,
1 gal/min/ff1; Air Flow, 400 ftj/gal; Concentration of NH3, influent 18 mg/1, effluent 3 mg/1; pH to 11-11.5
Operation Assumptions: Labor, at $7.50/h, including benefits; Power, at $.02/kwh; Lime, at 530/ton
Note: Total OsM costs have been derived from the power, materials, chemicals and labor costs provided in Ref. 3.
CONSTRUCTION COST
10
OPERATION & MAINTENANCE COST
1 0
0 1
001
0 1
REFERENCES - 3, 4
1 0 10
Wastewater Flow Mgal/d
100
100
0.001
Waitewater Flow, Mgal/d
*To convert construction cost to capital cost see Table A-2.
A-119
-------
ARRP (AMMONIA REMOVAL AND RECOVERY PROCESS) FACT SHEET 4.1.2
Description - ARRP consists of two packed towers for stripping and absorption. In the stripping tower, waste-
water flows downward against an upflow gas stream. Ammonia in the wastewater is stripped into the gas stream.
The gas stream is then directed to the absorption tower, in which an absorption solution is sprayed downward.
With good countercurrent contact, most of the ammonia transferred to the gas stream is absorbed by the solution.
The gas stream is then recycled back to the stripping tower for reuse.
Lime or caustic soda is usually added to the wastewater prior to ARRP to convert the ammonium ion in the waste-
water to free ammonia. Air is used as the stripping gas. Water or a dilute acid (sulfuric acid) is frequently
selected as the absorption solution, so that the process produces an aqueous ammonia solution or an ammonium
sulfate solution.
Common Modifications - For wastewaters with high ammonium ion concentrations (greater than 300 mg/1), steam may
be economically used as the stripping gas. Steam is injected at the bottom of the stripping tower and is con-
densed as it exits. A wastewater feed-effluent heat exchanger is often used to minimize energy consumption.
Technology Status - Steam stripping and absorption operations are commonly used in chemical and fertilizer indus-
tries. In wastewater treatment, air stripping is considered fully demonstrated, but not widely used. ARRP is a
relatively untried process.
Applications - Economically attractive for treatment of wastewater, with a high ammonium ion concentration (greater
than 100 mg/1). This approach is being used for stripping ammonia from selective ion exchange regenerant. May
produce a waste ammonia stream with some value.
Limitations - Less competitive as ammonium ion concentration decreases. Highly susceptible to the ammonia market
to become cost effective.
Typical Equipment/No, of Mfrs. (77) - Stripping towers/28; absorption towers/46
Performance - Ammonia removal efficiency can be expected to be higher than with ambient air stripping towers in
the colder climates, since the stripping gas temperature approximates the wastewater temperature. Removal
efficiencies are projected to range from 90 to 95 percent with water temperatures of 20°C to 75 percent at water
temperatures of 10 C. Scaling problems are reduced when compared to NH air stripping towers.
Chemicals Required -
Sulfuric acid (H SO ): at 2.72 parts per one part of ammonium ion recovered, if an (NH ) SO solution is the
desired product. No sulfuric acid is needed if water is used as the absorption solution.
Lime (CaO): Sufficient lime to raise pH to 10.8 to 11.5 (see Fact Sheet 4.2.2).
Acid for pH readjustment: may be needed for neutralization of the residual alkali.
Design Criteria (28, 47) -
Stripping Operation Absorption Operation
Wastewater loading: 1 to 2 gal/min/ft (air stripping) Product solution: 1 to 30% (aqueous ammonia)
7 gal/min/ft (steam stripping) to 50% ((NH4> SO4 solution)
Gas flow rate: 300 to 500 ft /gal (air stripping) Tower diameter: 50 to 75% flooding velocity
15 lb/1000 gal (steam stripping) Degree of recovery: about 90%
Packing depth: 20 to 25 ft Packing depth: 15 to 20 ft
Wastewater pH: 10.8 to 11.5 Gas pressure drop: 2 to 3" of water
Tower diameter is set to a gas flow of 50 to 75 percent of flooding velocity for both the stripper and
absorber.
Reliability - Can be expected to have a moderately high degree of reliability, as demonstrated in the chemical
industry. Occasional clean-up of scale in the stripping tower and heat exchanger may be required.
Environmental Impact - Air: No impact without leakage.
Water: Effluent would have a slightly higher solids content due to pH adjustment.
References - 3, 28, 47, 77
A-120
-------
ARRP (AMMONIA REMOVAL AND RECOVERY PROCESS)
FACT SHEET 4,1,2
FLOW DIAGRAM -
Wastewater containing
dissolved ammonia (NH )
Gas stream with ammonia increased
Motor
D
Ducting (Typical)
Acid and water makeup
Recycled
Absorbent
Liquid
u
V
Gas stream-ammonia ,
Deduced by absorption^
Wastewater stripped of nearly
all or part of ammonia (NH )
Ammonium salt blowdown
or discharge to stripper
ASSUMPTION - For lack of information on the adsorption unit, it is assumed to be two-thirds the size of the
stripping unit. A further assumption is that the construction cost, operation and maintenance cost, and energy
requirements are also two-thirds of that for the stripping unit.
ENERGY NOTES- 1140 X Mgal/d X TDH
Stripper: Pumping - kWh/yr = wire to %ater ef£iciency 3
Fan - kWh/yr = 76.5 hp/Mgal/d at 400 std. ft air/gal of wastewater
Absorber: Pumping - kWh/yr = 0.67 X Energy Required for Stripper Pumping
Fan - kWh/yr = 0.67 X Energy Required for Stripper Fan
For wastewater flow of 1 Mgal/d, TDH of 50 ft and wire to water efficiency of 60 percent. The total energy
required is: Pumping = 160,000 kWh/yr; Fan = 835,000 kWh/yr; Total = 995,000 kWh/yr
COSTS*- Assumptions: ENR Index = 2475
Construction cost includes ammonia stripping tower (20 ft high packed with 1/2 in. diameter schedule 80 PVC
pipe at 3 in. centers horizontally with alternate layers placed at right angles at 2 in. centers vertically);
pumps (50 ft TDH); lime feed facilities to raise pH to 11 to 11.5 and sulfuric acid facilities to subse-
quently neutralize the treated effluent. No credit for sale of NH .
Hydraulic loading: 1.0 gal/min/ft ; Air/water ratio: 400 ft /gal.
Process performance: Wastewater Characteristics
In Out
NH
3'
mg/1
18
CONSTRUCTION COST
OPERATION S MAINTENANCE COST
10
10
S 1.0
a
•3
a
O.l
REFERENCE - 3
10 100
Wastewater Flow, Mgal/d
10 100
Wastewater Flow, Mgal/d
*To convert construction cost to capital cost see Table A-2.
A-121
-------
BREAKPOINT CHLORINATION FACT SHEET 4.1.3
Description - Breakpoint chlorination is a chemical treatment for ammonium ion removal. In the process, chlorine
is added to a wastewater containing ammonium ion in a mixing tank, where practically all the ammonium ions are
oxidized to nitrogen gas. Amount of chlorine addition is precisely adjusted to a level (the breakpoint) which is
sufficient for the oxidation and results in minimal residual chlorine and by-product formation. Hydrochloric acid
is co-produced during the oxidation and must be neutralized by adding lime or caustic soda. Equipment needs are
relatively simple but control requirements for chlorine dosage and pH adjustment are sophisticated and important.
Common Modifications- A downstream de-chlorination step for the removal of residual chlorine is usually adopted.
This can be a SO addition (see Fact Sheet 4.5.2), or an activated carbon adsorption (see Fact Sheet 4.4.1).
Sodium hypochlonte (NaOCl) may be used for the oxidation, instead of chlorine with no HC1 co-production. In this
case, no lime or caustic soda addition is needed.
Technology Status - Demonstrated on a large scale, but not widely used.
Applications - It is economically attractive for wastewater with low ammonium ion concentrations (less than 5
mg/1) and can be employed as a polishing step following other ammonium ion removal processes. It is especially
attractive in a cold weather location.
Limitations - The process is rated low in capital costs, but high in operating costs, especially at ammonium ion
concentrations above 16 mg/1. Potential for formation of chlorinated hydrocarbons in the effluent.
Typical Equipment/No, of Mfrs. (77) Chlorine analyzers/25; pH controllers/25; Control computers/42; Chemical
feeders/27; Mixers/26.
Performance - Can reduce ammonium ion concentration to 0.1 mg/1 or less, and convert to nitrogen gas and to insig-
nificant amounts of by-products (nitrate at 0.2 to 0.45 mg/1 and NCI at 0 to 0.25 mg/1) under normal operation.
Performance is not affected by temperature fluctuation or toxic compounds. However, pH and chlorine dosage have
significant effects on by-product formations as follows:
pH_ 6_ 1_ £ Cl? dosage Breakpoint 50% excess
NCI , mg/1 0.33 0.05 NCl , mg/1 Trace 0.63
NO , mg/1 0.70 1.0 NO", mg/1 0.15 0.6
Organic nitrogen compound is only slightly reduced.
Chemicals Required-
Chlorine (Cl ): 8 to 13 parts per one part of ammonium ion (or NaOCl at 9 to 14 parts, instead of C12)
Lime (CaO): 0.9 to 1.1 Ib per one Ib of Cl2 or 1.5 Ib of NaOH per one Ib of C12 (No need if NaOCl is used instead
of cl )
SO for dechlonnation: See Fact Sheet 4.5.2.
Design Criteria (28) , (47) -
Chlorination Activated Carbon Dechlorination
pH range: 6 to 7 Loading rate: 1 to 2 gal/min/ft
Contact time: 1-2 min. Carbon charge: 0.3 to 2 ft /Mgal
Cl control: quick response Contact time: 10 min.
Reliability - Process reliability is medium. Computer control for quick and close dosage of chlorine and pH
adjustment may be required to improve reliability and to minimize by-product formation.
Environmental Impact -
Air: Chlorine and by-products such as NCI. and H may escape into the atmosphere, but the amounts are normally
neglibible without process upset. Aeration operation for de-chlorination may not be acceptable in certain
locations if the exit air is discharged directly into atmosphere.
Aqueous: Effluent TDS would increase significantly at 8.5, 12.2 or 14.8 times the amount of the ammonium ion
reduced, depending on whether NaOCl, lime or caustic soda is used in the process.
References - 3, 23, 28, 31, 47
A-122
-------
BREAKPOINT CHLORINATION
FACT SHEET 4.1,3
FLOW DIAGRAM -
T
Effluent
ENERGY NOTES - Mixing energy - Approximately 135,000 kWh/yr/Mgal/d (Mixing power at 0.37 kWh/1000 gal)
COSTS - Assumptions :
Service Life: 15 years
Equipment: Chlorine storage and feed system, lime storage and feed system, mixing tank (30 min)
hemicals: C12 (13 Ib/lb of ammonium ion) at $160/ton
Lime (0.9 Ib/lb of Cl ) at $30/ton
Concentration: Ammonium ion input 23 mg/1, output 2.6 mg/1
Labor Rate: $7.50/h including benefits
Power Cost: $.02/kWh
Index: ENR 2475, Sept. 1976
10
001
CONSTRUCTION COST
-+
u
O.I
REFERENCE - 3
10 10
Wastewater Flow, Mgal/d
100
Wastewater Flow, Mgal/d
*To convert construction cost to capital cost see Table A-2.
A-123
-------
ION EXCHANGE (FOR AMMONIA REMOVAL) FACT SHEET H.l.
Description - The ion exchange process can be utilized to reduce the ammonium ion concentration in wastewater.
The medium is usually clinoptilolite, a natural ion exchange material. Wastewater, following filtration to reduce
suspended solids, is passed downflow through the ion-exchange bed until the bed reaches the point of exhaustion.
The bed is considered exhausted when the ammonia concentration in the effluent reaches a predetermined value. The
exhausted bed can be regenerated with 2 percent NaCl solution. The effluent from the regeneration process is
called spent regenerant, and it amounts to 2.5 to 5 percent of the wastewater stream and may contain more than 300
mg/1 of ammonia. The key to the application of the ion exchange process is the method of handling of the spent
regenerant.
The process for individual beds is batch but, by using multiple beds, continuous operation can be accomplished.
The spent regenerant requires some form of processing for separation of ammonia so that the regenerant can be
reused. The alternative processes available for regenerant recovery are air stripping or steam stripping (Fact
Sheet 4.1.2) at high pH and electrolysis treatment. The stripped ammonia can be vented to the atmosphere or
absorbed in dilute acid solution and sold as fertilizer. Steam stripping produces a 1 percent aqueous ammonia
solution as a waste product. Electrolysis converts chloride in the spent regenerant to chlorine which oxidizes
ammonium to nitrogen gas.
Common Modifications - Any ion exchange material which has high selectivity for ammonium over other cations can be
substituted for clinoptilolite.
Technology Status - The process is considered fully demonstrated, but not widely used.
Applications - The process may be employed for one or more of the following reasons: (1) Where cold weather
limits the application of stripping as the sole process of ammonia removal (Fact Sheet 4.1.2), (2) reduction from
a feed with low concentration of ammonium ion, 10 to 50 mg/1, (3) potential for the reduction of ammonia emission
to atmosphere, (4) where limited increase in TDS is allowable.
Limitations - Relatively high capital cost compared to the other two ammonia removal processes, stripping or
breakpoint chlorination. Nitrite, nitrate and organic nitrogen compounds are not removed.
Typical Equipment/No, of Mfrs. (77) - Ion exchangers/15; mixers/26; cycle controllers/36.
Performance - High ammonium ion removal efficiency, 93 to 97 percent, not significantly impaired by temperature
fluctuation, and unaffected by toxic compounds. Residual ammonium ion concentrations are in the one to three mg/1
range (down to 0.22 mg/1 is possible at higher costs). Wastewater TDS would be increased by about 50 mg/1.
Chemicals Required -
Salt (NaCl): about 0.1 lb/1000 gallons of wastewater as makeup for purge and regenerant loss.
Caustic soda (NaOH): at 1.15 parts per one part of ammonium ion (or lime (CaO) at 1.6 parts per part of
ammonium ion), if air or steam stripping is used for ammonia recovery.
Design Criteria -
Ion Exchange Operation Regeneration
Clinoptilolite size = 20 x 50 mesh Solution = 2% NaCl
Bed height = 4 to 6 ft Solution flow rate =4 to 10 bed volume/h
Wastewater suspended solids = 35 mg/1 max. or 4 to 8 gal/min/ft
Wastewater loading rate = 7.5 to 20 bed volume/h Total solution volume = 2.5 to 5% of treated
Pressure drop = 8.4 in. of water/ft wastewater or 10 bed volumes
Cycle time = 100 to 150 bed volumes for one 6 ft bed; Cycle time = 1 to 3 hour,s
200 to 250 bed volumes for two 6 ft beds in series Backwash = 8 gal/min/ft
Reliability - Moderate. Operation is usually on automatic control, requiring occasional monitoring, inspection
and maintenance. There is a potential scaling problem for wastewater with high magnesium and/or calcium contents.
Environmental Impact -
Air: None, unless regenerant air is stripped for NH removal (see Fact Sheet 4.1.1).
Aqueous: A small purge stream (about 0.3 gal/1000 gal of wastewater), containing two percent NaCl, small amounts
of calcium and magnesium salts and possibly some toxic metal ions (if any in the wastewater) must be disposed of.
When a clarification step is employed, a low volume sludge stream, mainly Mg(OH)2 and CaCO. must be disposed of.
Effluent from the process would have a slightly higher solids content (addition of about 50 mg/1 of salt).
References - 3, 23, 28, 47, 77
A-124
-------
ION EXCHANGE (FOR AMMONIA REMOVAL)
FACT SHEET it.l.
FLOW DIAGRAM -
Neutral pH
Spent
Influent Regenerant
to one of the following:
I -
Air
Stripping
Ammonia Removal
and Recovery
Process (ARRP)
Effluent
Fresh and makeup
Regenerant
Electrolysis
Cells
NH to
Atmosphere
Sludge
Recovered
Ammonia as
Sludge
H and N
Sludge
ENERGY NOTES - From the example below, power for operation of the regenerator amounts to 11,500 kWh/yr/Mgal/d.
COSTS * - Assumptions: ENR index = 2475
1. Construction costs include:
a. Gravity feed clinoptilolite beds with loading rate of 5.25 gal/min/ft at 4 ft depth.
b. Backwash regeneration facilities at 8 gal/min/ft .
c. Sodium chloride regeneration facilities using 2 percent NaCl solution, 40 bed volumes/regeneration, and
1 regeneration/24 h.
d. Closed-loop air stripping tower for regenerant recovery.
e. Clarifier for spent regenerant.
2. Chemical costs include makeup clinoptilolite and makeup regenerant.
3. Ammonium sulfate produced by this system may be sold to offset operation and maintenance costs; however,
it was not included in this cost estimate.
Note: Totals have been derived from the power, labor, materials and chemicals costs provided in reference 3.
01
REFERENCE - 3
10 IO
Wastewater Flow. Mgal/d
I
0.01
Ol
10 10
Wastewater Flow, Mgal/d
*To convert construction cost to capital cost see Table A-2.
A-125
-------
LIME RECALCINATION FACT SHEET 4.2,1
Description - In the recalcination process, lime sludge is subjected to thermal decomposition to produce quick
lime (CaO) and CO . This process is very similar to the calcination process, except for the raw material, which
is sludge. Primary or tertiary sludge where lime is used for coagulation can be recalcined. The application of
the process reduces the volume for sludge disposal and for lime make-up requirements.
In a typical recalcination system, the lime sludges from chemical clarifiers and recarbonation reaction basins are
thickened and centrifugally classified. The thickening process increases the solids concentration to 20 to 40
percent and the centrifugation reduces the inert content. The inert materials are made up largely of magnesium
hydroxide and hydroxyapatite, and their presence will make the lime recovery and reuse more difficult. The cakes
after centrifugation are ready for recalcination in the open hearth or fluidized bed furnace.
The tertiary plant serving South Lake Tahoe provides the most significant experience with open hearth furnace and
the following details pertain to this plant. The cake after passing through solid bowl concurrent flow centri-
fuges is carried by a belt conveyor to a six-hearth furnace. The optimum temperature of operation appears to be
1900 F on the fourth and fifth hearths at 1.5 to 2.0 rabble rate. At this temperature, the available CaO increased
by 5 percent as compared to a temperature of 1800 F. At a lower temperature, 1600 F, the product showed a tendency
to agglomerate into particles of 1/4 to 3/4 inches in diameter with centers of unburned organic sludge in many of
them. The recalcined lime is conveyed out of the furnace by gravity through a crusher to a thermal disc cooler
where the lime temperature is lowered from 700 F to 100 to 150 F. From there it is conveyed to a rotary air lock
and then to the storage bin. The product is in the form of lime dust. A portion of the stack gas is recycled to
the recarbonation system to adjust the pH to about 7. The rest is scrubbed in a multiple tray scrubber before
exhausting to the atmosphere. Although the cost of recalcined lime is slightly higher than new lime, the magnitude
of sludge disposal reduced from 34 tons/d of liquid sludge to 1.5 tons/d of dry solids, thereby effecting a sub-
stantial cost saving.
A fluidized bed furnace may also be used. The filter cake is fed to a mixer along with dry recycled fines and
quench water. From there it goes to a cage mill disintegrator where the pre-cooled calciner stack gas at 1000 F
dries and disintegrates the moist solids. The resultant fine carbonate is conveyed by the exhaust gas to a
cyclone separator. From the cyclone separator, a portion is recycled to the mixer and the other portion is fed to
the calciner bin from where it enters the furnace. The furnace contains two compartments. The upper fluid bed is
used for low temperature calcination (1500 to 1600 F) and the lower third bed to cool the product. The product is
in the form of pelletized particles of 6 to 20 mesh size which is the primary advantage over the dusty product of
open hearth furnace.
Commod Modifications - When large quantities of inert materials are involved, a dry classification device may be
used after the recalcination furnace in addition to the wet centrifugal devices mentioned above.
Technology Status - At least six United States plants have utilized recalcination of lime sludge from treatment of
wastewater.
Applications - Minimize makeup lime requirements and the amount of sludge for disposal.
Limitations - Economic feasibility of the process at a given site is dependent upon such factors as the quantity
of lime used, sludge disposal costs and fuel costs and indirectly the expertise of the personnel available for
satisfactory operation.
Typical Equipment/No, of Mfrs. (10, 23) - Calcination Reactor/12; Stack Gas scrubbers/3; Sludge cake conveyors/7;
Sludge pumps/7; Air fans/42.
Performance - The recalcination of lime sludge reduces by a factor of 20 the amount of water and sludge for
disposal. Seventy-two percent of the plant lime requirements can be obtained from the recovery process; 3.7
percent by weight of the usable calcium entering the furnace is lost as fly ash and captured in the wet scrubber.
Residuals Generated - Inerts from the centrifugal classifier in the form of magnesium hydroxide and hydroxyapatite
and a portion of the lime. Wet scrubber sludge containing recalcined lime and particulates from combustion.
Design Criteria - Hearth loading rate = 5 Ib/ft /h of wet solids (approximately). Dry solids concentra-
tion = 20 to 40 percent. Excess air = 75 to 100 percent. Shaft cooling air flow = 1/3 to 1/2 of combustion air
flow.
Environmental Impact - Particulate collection efficiencies of 96 to 97 percent are required to meet current EPA
standards. Available data indicate that other air and water pollutant emissions are acceptable, however addi-
tional testing is required to confirm this.
References - 3, 8, 10, 23, 43, 77, 208
A-126
-------
,
LIME RECALCINATION FACT SHEET 4.2.1
FLOW DIAGRAM -
ENERGY NOTES - E
Electrical enerc
Mgal/d
1
10
100
Fuel requirement
To determine en
COSTS* - Assumpt
Primary or
Tertiary
Sludge
•" 1
hickener
*
Supernatant
ased on Design Assumptions below.
y -
kWh/yr
150 x 10
650 X 10
4,500 x 10
-s 1.78 x 1010 Btu/Mgal/d/yr
ergy requirements for centrifuge o
.ions: Service Life = 30 years; E!
Classification
I High
inert to CaC°3 Cake
Landfill
peration see Fact Sheet 6.3.
« Index = 2475
1
Gc
Fur
IS
V
nace
1 .
Scrubber
Drain
Lime to
Storage Bin
Design Basis:
1. Quantity of lime sludge: 4,500 lb/Mgal; 30 percent solids (from two-stage tertiary lime treatment).
2. Operations:
Furnace Hearth
Flow Wet Solids Days/Week Hours/Day Loading Area
Mgal/d Ib/h; 24 h/d Operating Operating Ib/h ft
0.1 62.5 1 20 525 112
1.0 625 6 16 1,095 256
10.0 6,250 7 20 7,500 2 at 760
100.0 62,500 7 20 75,000 3 at 5,070
3. Fuel requirements (No. 2 fuel oil): 129,000 gal/yr/Mgal/d - 1.78 x 10 Btu/Mgal/d/yr
4. Construction costs include recalcination furnace, sludge conveyors, storage, hoppers, building.
Fuel cost = S2. 66/10 Btu. Power cost = $0.02/kWh.
CONSTRUCTION COST OPERATION & MAINTENANCE COST
mn 10 1 0
o — i
O
o
2 10-
0 1
REFERENCE - 3
s'
^'
_ . . . — y*
,.•
- - - • c
O
5 if
(0 to "^
1 1 1 1|| < r | | r [>"[
"***!
n m / I I
f / *
n;^==i
••
Labor
/>
/?--
, ' PO>
, .
.'it
' '/
j" f
& ---,, Oil
;3|2-::: |
^ £
wer «
10 10 100 01 10 10 100
Wastewater Flow Mgal d Wastewater Flow, Mgal/d
*To convert construction cost to capital cost see Table A-2.
A-127
-------
TWO-STAGE TERTIARY LIME TREATMENT, WITHOUT RECALCINATION FACT SHEET 4.2,2
Description - Lime treatment of secondary effluent for the removal of phosphorus and suspended solids is essen-
tially the same process as high-lime clarification of raw wastewater. Calcium carbonate and magnesium hydroxide
precipitate at high pH along with phosphorus hydroxyapatite and other suspended solids. In the two stage system,
the first stage precipitation generally is controlled around a pH of 11, which is approximately one pH unit higher
than that used in the single stage process. After precipitation and clarification in the first stage, the waste-
water is recarbonated with carbon dioxide, forming a calcium carbonate precipitate which is removed in the second
clarification stage.
Lime is generally added to a separate rapid-mixing tank or to the mixing zone of a solids contact or sludge
blanket clarifier. After mixing, the wastewater is flocculated to allow for the particles to increase in size to
aid in clarification. The clarified wastewater is recarbonated in a separate tank following the first clarifier,
after which it is re-clarified in a second clarifier. Final pH adjustment may be required to meet allowable
discharge limits.
Common Modifications - Treatment systems can consist of separate units for flash mixing, flocculation, and clari-
fication; or they can consist of specially designed solids contact or sludge blanket units which contain flash
mix, flocculation, and clarification zones in one unit. The calcium carbonate sludge formed in the second stage
can be recalcined (see Fact Sheet No. 4.2.1). Final effluent can be neutralized with sulfuric acid, as well as
other acids.
Technology Status - The use of these systems for water softening have been used for many decades, however their
use for phosphorus removal has been prominent only since the mid-1960'a. There are presently many large scale
systems in operation.
Typical Equipment/No, of Mfrs. (23) - Clarifier equipment/38; chemical feeders/6; flocculators/32,- mixers/26;
ins trumentation/9.
Applications - Used for the removal of phosphorus from wastewaters. Will also remove some BOD5 and suspended
solids as well as hardness present in the wastewater. Will also remove metals.
Limitations - Will generate relatively large amounts of chemical sludge. High operator skill required. In some
cases polymer or coagulant is required to assist second-stage clarification.
Performance -
Influent Effluent
Phosphorus as P Generally 15 to 40 mg/1, but not limiting in 0.01 to 1 mg/1
regard to effluent quality
Chemicals Required - Lime (CaO), C02 or H2S04, sometimes polymer or coagulant
Residuals Generated - First stage - Sludge containing hydroxyapatite, calcium carbonate, magnesium hydroxide, and
organic solids - 1 to 1.5 pounds of dry solids per pound of lime added. Second stage - sludge may contain calcium
carbonate, aluminum or ferric hydroxide, depending upon the coagulant used. The quantities generated are: 2.27
pounds CaCo per pound of CO ; 4 pounds per pound of Al in alum or 2.5 pounds per pound of Fe in ferric chloride.
Design Criteria - Clarifier settling rate - 1,000 to 1,400 gal/d/ft
Secondary Effluent Approximate Lime
Alkalinity Clarifier pH Dose
(mg/1 as CaCO ) (mg/1 of CaO)
300 11.0 400-450
400 11.0 450-500
Carbon Dioxide - Feed tank - 5 to 15 minutes
Feed rate - 1.2 mg/l/mg/1 of Ca to be precipitated
Unit Process Reliability - These systems are reliable from both a unit and process standpoint with skilled oper-
ator attention.
Environmental Impact - Will generate relatively large amounts of sludge which will need to be handled in some
manner. Will have little or no effect on air pollution, noise levels, or odor. In comparison to secondary
systems, little land use is required.
References - 29, 95
A-128
-------
TWO-STAGE TERTIARY LIME TREATMENT, WITHOUT RECALCINATION
FACT SHEET 4.2.2
FLOW DIAGRAM -
Wastewater
Feed
Treated
Rapid Mix
Slaker
Flocculator
Settler
Sludge
Recarbonator
t
Carbon
Dioxide
Settler
1
Sludge
Water •
Lime
ENERGY NOTES -
See design basis under COSTS.
COSTS - Assumptions: ENR - 2475
1. Typical secondary effluent as feed to two-
stage lime treatment.
2. Lime dosage rate = 400 mg/1 or 3,340 Ib/Mgal
as CaO.
3. Clarifier overflow rate = 1,000 gal/d/ft .
4. Construction cost includes: lime storage and
feed facilities, rapid-mix facilities, floc-
culator/clarifiers, flow and pH controls,
and recarbonation facilities.
5. Costs do not include recalcination facilities.
6. Electric power = $.02/kWh
7- Lime costs - $25/ton, quick lime
100
CONSTRUCTION COST
10
o
Q
1 0
01
01
REFERENCE - 3,
1 0 10
Wastewater Flow, Mgal/d
100
Sludge to Recalcinator
or Disposal
10
X
•a
n
s
w
t-i
ID
O
•H
H
4J
O
10"
10
10'
0.1 1.0 10 100
Wastewater Flow, Mgal/d
10
OPERATION & MAINTENANCE COST
of
o E
10
ȣ 01
001
Total
Material
lemicals
.abor
01
001
0001
01
1 0 10
Wastewater Flow, Mgal/d
100
00001
*To convert construction cost to capital cost see Table A-2.
A-129
-------
INDEPENDENT PHYSICAL/CHEMICAL TREATMENT
FACT SHEET 4.3.
Description - Independent Physical-Chemical Treatment (IPC) utilizes methods other than biological treatment to
obtain secondary, or better, removals of BOD , COD and TSS. Typically, these systems use combinations of clari-
fication with chemical addition, filtration, and activated carbon. This Fact Sheet includes nitrate addition to
the activated carbon system to prevent H S formation by biological action in the carbon contactor.
Common Modifications - The following are some typical flow trains that can be used: Clarification, filtration,
activated carbon (downflow); clarification, activated carbon (upflow), filtration. Additional treatment steps can
be added to obtain better than secondary treatment levels, such as ammonia removal and part of phosphate clari-
fication.
Technology Status - A number of full scale systems have been started up.
operation. It has not been used on a wide scale.
Several mechanical problems have plagued
Typical Equipment -
Clarification, filtration, preliminary treatment - See Fact Sheets 3.1.1 through 3.1.5.
Chemical addition - See Fact Sheets in Section 5.
Thickening and dewatering - See Fact Sheets 6.3.1 through 6.3.9.
Activated Carbon - See Fact Sheets 4.4.1, and 4.4.2.
Chlorination - See Fact Sheet 4.5.1.
Transportation and disposal - See Fact Sheets 6.1.1 through 6.1.11.
Applications - IPC can be used in some applications where standard biological treatment applies, namely typical
municipal wastewater. IPC is a very flexible process and can be tailored to specific pollutant problems, such as
high background levels of metals or refractory organic materials. Phosphorus and some toxic chemicals will also
be removed. (See Fact Sheet 4.4.1.)
Limitations - The large quantities of sludge produced by the process may result in disposal problems.
Performance (50) - Application of screened degritted wastewater can result in the following estimated process
effluent quality:
Unit Process
Combinations
C,S
C,S,F
C,S,F,AC
C,S,NS,F,AC
TURB
(JTU)
5-20
1-2
1-2
1-2
P°4
(mg/1)
1-4
0.5-2
0.5-2
0.5-2
SS
(mg/1)
10-30
2-10
2-10
2-10
Color
(Units)
30-60
30-60
5-20
5-20
NH -N
(mg/1)
20-30
20-30
20-30
1-10
C,S = coagulation and sedimentation; F = mixed-media filtration;
AC = activated carbon adsorption; NS = ammonia stripping.
Lower effluent NH value at 18 C; upper value at 13 C.
Chemicals Required - NaNO for H S control.
the first stage clarification process. These include alum (AL (SO ) 14H O) , ferric chloride (Fed ) , polymers,
its.
In addition, chemicals are used to aid in suspended solids removal in
: include alum (A1-.
and lime (CaO). In small plants carbon dominates chemical cosl
Residuals Generated - Sludge will be generated in the preliminary clarification step. This sludge is quite
voluminous (see Fact Sheet 5.1.5 for lime and 4.2.2 for alum and ferric chloride). Filter backwash water (see
Fact Sheets 3.1.7 and 3.1.8) and spent activated carbon and carbon backwash water (see Fact Sheet 4.4.1) will also
be generated. Carbon from regeneration will be recycled within the plant and the ash fines must be disposed of in
an acceptable manner.
Design Criteria - See associated Fact Sheets for individual pieces of equipment. (Refer to listing of processes
under "Typical Equipment" as shown above.)
Unit Process Reliability - Because this process is a combination of many processes, the reliability is a function
of the individual unit process reliabilities. See Individual Fact Sheets as indicated above.
Toxics Management - Removes many, but not all, non-degradable organic compounds.
high molecular weight, slightly soluble compounds.
Most effective for non-polar,
EPA has developed activated carbon adsorption isotherms for 60 toxic organic materials (86). The isotherms
demonstrate removal of 51 of these organic compounds by activated carbon technology. Another study (87) demon-
strated that PCB levels can be reduced from 50 micrograms per liter to less than 1 microgram per liter, and other
work showed that aldrin, dieldrin, endrin, DDE, DDT, ODD, toxaphene, and Aroclors 1242 and 1254 can be renoved to
values less than 1 microgram per liter (88). Toxicity measured by bioassays was also significantly reduced.
Environmental Impact- See Fact Sheets for individual processes. In general, however, this process requires much
less land area than conventional biological secondary treatment systems. Phosphorus removal is inherent in this
system.
References - 50, 86, 87, 88, 95
A-130
-------
INDEPENDENT PHYSICAL/CHEMICAL TREATMENT
FACT SHEET 1.3,1
LOW DIAGRAM -
Sludge Thickening
S Dewatering
Backwash
Sludge to Disposal
i:\ERGY NOTES - Energy (kWh/yr) = 7,500,000 (Mgal/d) .
COSTS -*(ENR Index = 2475) Assumptions:
1. Processes include lift pumps, preliminary treatment, two-stage lime/ gravity filtration, interstage pumping,
carbon adsorption, chlorination, gravity thickener, vacuum filters, miscellaneous structures, support per-
sonnel .
2 Lime dosage at 400 mg/1 as CaO.
3. Carbon adsorption without regeneration at plant sizes less than 3 Mgal/d; carbon adsorption with regeneration
at plant size greater than 3 Mgal/d.
100,-
CONSTRUCTION COST
10
10
0 1
100
OPERATION & MAINTENANCE COST
0 10
15 1 0
0 1
1 0 10
Wastewater Flow, Mgal/d
100
0 1
**
emicals
Total:
s^r
Labo
10
«
I
1 0 g
01 E
3
1 o 10
Wastewater Flow, Mgal/d
100
001
REFERENCE - 3
*To convert constr
uction cost to capital cost see Table A-2.
A-131
-------
TERTIARY GRANULAR ACTIVATED CARBON ADSORPTION FACT SHEET H.U.l
Description - Granular activated carbon is used in wastewater treatment to adsorb soluble organic materials.
Granular carbon systems generally consist of vessels in which the carbon is placed, forming a "filter" bed.
These systems can also include carbon storage vessels and thermal regeneration facilities. Vessels are usually
circular for pressure systems or rectangular for gravity flow systems. Once the carbon adsorptive capacity has
been fully utilized, it must be disposed of or regenerated. Usually multiple carbon vessels are used to allow
continuous operation. Columns can be operated in series or parallel modes. All vessels must be equipped with
carbon removal and loading mechanisms to allow for the removal of spent carbon and the addition of new material.
Flow can be either upward or downward through the carbon bed. Vessels are backwashed periodically. Surface wash
and air scour systems can also be used as part of the backwash cycle.
Small systems usually dispose of spent carbon or regenerate it offsite. Systems above about 3 to 5 Mgal/d us
provide on-site regeneration of carbon for economic reasons. (See Fact Sheet No.4.4.2)
isually
Technology Status - Has been used for municipal wastewater treatment on a limited basis since the mid-1960's.
Applications - Used directly following secondary clarifier, primarily when nitrification obtained in secondary
treatment. Often preceded by chemical clarification of secondary effluent. In either case, a high quality
influent is sought.
Limitations - Wastewater should be filtered prior to treatment to remove suspended solids. Requires more sophis-
ticated operation than standard secondary treatment systems. Under certain conditions, granular carbon beds
provide favorable conditions for the production of hydrogen sulfide, creating odors, and corrosion problems.
More mechanical operations - difficult corrosion control - materials handling. Most applicable to low strength
or toxic wastewaters.
Typical Equipment/No, of Mfrs. (23) - Activated carbon material/5 (90), granular carbon systems/15
Performance
Influent (mg/1) Effluent (mg/1)
BOD 10 to 50 5 to 20
COD 20 to 100 10 to 50
TSS 5 to 10 2 to 10
Side Streams:
Spent Carbon - 3 to 10 Ib/lb of COD removed for Tertiary treatment
Backwash Water - 1 to 5 percent of wastewater throughput, TSS 100 to 250 mg/1
Design Criteria -
Size - Vessels 2 to 12 ft diameter commonly used
Area Loading - 2 to 10 gal/min/ft
Organic Loading - 0.1 to 0.3 Ib BOD or COD/lb carbon
Backwash - 12 to 20 gal/min/ft
Air Scour - 3 to 5 ft /min/ft
Bed Depth - 5 to 30 ft
Contact Time - 10 to 50 min.
Land Area - minimal
Reliability - Moderately reliable both mechanically and operationally depending on design construction and man-
ufactured equipment quality.
Toxics Management - Removes many, but not all, non-degradable organic compounds. Most effective for non-polar.
high molecular weight, slightly soluble compounds.
EPA has developed activated carbon adsorption isotherms for 60 toxic organic materials (86). The isotherms
demonstrate removal of 51 of these organic compounds by activated carbon technology. Another study (87) demon-
strated that PCB levels can be reduced from 50 micrograms per liter to less than 1 microgram per liter, and other
work showed that aldrin, dieldrin, endrin, DDE, DDT, ODD, Toxaphene, and Aroclors 1242 and 1254 can be removed to
values less than 1 microgram per liter(88). Toxicity measured by bioassays was also significantly reduced.
Environmental Impact - Very little use of land. There is air pollution generated as a result of regeneration.
Under certain conditions, granular activated carbon beds may generate hydrogen sulfide which has an unpleasant
odor. NaNO or chlorine may be applied to the influent to inhibit or control these conditions. Spent carbon may
be a land disposal problem, unless regenerated.
Improved Joint Treatment Potential - Will remove pollutants discharged by industrial sources that are generally
not treated by normal secondary systems such as refractory organic materials and some metals.
References - 4, 23, 50, 84, 85, 86, 87, 88, 89, 90
A-132
-------
TERTIARY GRANULAR ACTIVATED CARBON
FLOW DIAGRAM
-
ADSORPTION FACT SHEET 4. 4. 1
Spent Backwash
to Headworks
Secondary
Effluent
Activated
Carbon
*
*
Back-
wash
Tank
O
Backwash Pump
ENERGY NOTES - The energy consumption curve
the energy require
Sheet 4.4.2 for re
Carbon: 8 to 30 me
Downflow Pressure
ft ; terminal head
15 min; backwash f
Downflow Gravity -
d
ge
sh
I2
lo
for
nera
siz
Head
ss =
Dumping onl
tion energy
a .
Loss = 37 f
rkwash rate
20 ft; bac
requency =
Hydraulic
ft"; terminal headless =
18 gal/min/ft ; backwash
frequency = 1/d; backwasl
pump and motor efficiency
COSTS* - Assumptions: El
6 f
tim
i pu
t -
TO I
]
]
t,
e
mi
7C
nc
./d.
oad
back
= 15
head
perc
lex =
y. See
requir
t; hydr
- 18 c
kwash t
3.5 gal
wash ra
min; ba
loss -
ent.
2475
E
en
at
al
in
/n
te
ck
23
gi
ac
len
li
/m
ie
in
—
wa
f
ves
t
t.
c
in/
/
sh
t;
Effluent
io6
Electrical Energy Required, kWh/yr
£ H t-
o5
o4
33
C
/
.1
/,
s
7
/
/ j
^/
7^-r^-
"S^h
i
...../
/
p
7
s
7
. Z
/ 1
1 |
J^fn-
-f
Downflow Pressurized Contac
Downflow Grav
-rttrt— t-
ity Cont
II
actor '
1.0 10
Flow, Mgal/d
' ' r
i {
1
tor
100-
1. Construction cost includes vessels, media, pumps, carbon storage tanks, controls, and operations building ;
loading rate = 30 Ib carbon per Mgal; contact time = 30 min; disposal costs not included.
2. 0/M cost includes pumping ($.02/kWh), labor ($7.50/h, including fringes) and maintenance.
3. No regeneration is included.
CONSTRUCTION COST OPERATION & MAINTENANCE COST
1 pa.- ! r-rt -— -r-r-- — h — t— — — r--r- r" — ' ^ L
10
o
D
"o
VI
C
0
2 1 0
0 1
(
REFERENCES -
*
x
X
'
x
•-^
'
S
— 7 "
s
, *
-J-J4- —
/
S
— 7
(A
nj
o
7 c
o
—
o
::::: <
0 01
^
/
x
T'
:
^/
>•
f|4-|
4~^
./r
M^
~
^
1_ .
,'
x 1
\ .1 ...LJ If
'"]
1
1
3.1 1.0 10 100 o.l 1.0 10 100
Wastewater Flow, Mgal/d Wastewater Flow, Mgal/d
3, 84
*To convert construction cost to capital cost see Table A-2.
A-133
-------
ACTIVATED CARBON THERMAL REGENERATION FACT SHEET H.H.2
Description - To make granular activated carbon economically feasible for wastewater treatment in most applications.
the exhausted carbon must be regenerated and reused. When the plant effluent quality reaches the minimum effluent
quality standards or when a predetermined carbon dosage is achieved, spent carbon is removed from the columns to be
regenerated. The most common method of thermal regeneration of carbon is with the use of multiple hearth furnaces.
Rotary kiln furnaces are also in use. In either case, a typical sequence for thermal regeneration of carbon is as
follows:
The granular carbon is hydraulically transported (pumped) in a water slurry to the regeneration station for de-
watering.
After dewatering, the carbon is fed to a furnace which requires an external source of steam and is heated to 1500
to 1700 F in a controlled atmosphere which volatilizes and oxidizes the adsorbed impurities.
The hot regenerated carbon is quenched in water.
The cooled regenerated carbon is washed to remove carbon fines and hydraulically transported to the adsorption
equipment or to storage.
The furnace off-gases are scrubbed, (the scrubber water is returned to the plant for processing) and may also pass
through an afterburner.
The thermal regeneration grocess itself involves four steps. The first step is drying, which occurs by evaporation
at temperatures up to 300 F. The second step involves volatilization of light organic materials. This occurs at
300 to 600 F. Those organic compounds which are not removed by volatilization are thermally decomposed at tem-
peratures of 600 to 1200 F. The last step involves reactivation, which is the removal of char from the pores of
the carbon. The total regeneration process requires approximately 30 minutes. Regeneration systems usually
require spent carbon holding tanks, regenerated carbon holding tanks, dewatering screws, quench tanks, steam
generators, and air pollution control equipment.
Common Modifications - Multiple hearth furnaces, rotary kiln furnaces.
Technology Status - Thermal regeneration of carbon is a well-established and demonstrated technology.
Typical Equipment/No, of Mfrs. (23, 100) - Carbon regeneration furnaces/3; conveyors/4; air scrubbers/over 50.
Applications - Can be used whenever disposal of carbon is uneconomical or environmentally impractical, generally at
large facilities.
Limitations - Is usually not practical for small activated carbon systems. Should generally be operated on a
24 h/d basis, which requires around-the-clock operator attention.
Performance - The quality of the carbon exiting the regeneration system will not equal that of virgin carbon.
However, the actual amount of degradation is greatly dependent upon the carbon used and the organic materials
removed. In general, there will be a reduction in iodine number, molasses index, with an associated increase in
ash content. In addition, there will be a loss in carbon due to oxidation and crushing. This generally totals 2
to 10 percent of the carbon being regenerated, with 5 percent being the general average value.
Chemicals Required - Acid may be used to strip metals from regenerated carbon, in special cases.
Residuals Generated - Some amount of ash and carbon fines will be generated, which will greatly depend upon the
quality of carbon and the type of wastewater treated. Exhaust air from the furnace will require scrubber treat-
ment, resulting in the recycling of solids to the plant and eventual inclusion in sludges.
Design Criteria - The theoretically required furnace capacity can be determined by multiplying the carbon dosage
(in Ib carbon/Mgal) by the daily flow rate in Mgal/d. This will determine the Ib carbon/d that must be regen-
erated. An allowance of 40 percent downtime should then be included. Multiple hearth furnaces used for regen-
erating carbon generally include a hearth area of about 1 ft /40 Ib carbon/d to be regenerated. A storage tank
should be sized to hold all of the carbon contained in the largest carbon adsorber. This tank would be used to
hold the carbon prior to regeneration. A tank of equal size is needed to hold the regenerated carbon prior to its
use in a previously emptied adsorber. A steam generator (0.4 to 1.0 Ib steam/lb carbon) is also required in con-
junction with the furnace. All ancillary equipment, such as conveyors and quenchers, should be designed for the
maximum throughput of the furnace.
Unit Process Reliability - Carbon regeneration systems are reliable from a process standpoint. However, they are
subject to more mechanical failures than other wastewater treatment processes. Therefore, high maintenance costs,
relative to the unit's construction cost, can be expected.
Environmental Impact - Very little use of land is required. Air emissions from the furnace will be polluted with
volatiles stripped from the carbon and with carbon monoxide formed from incomplete combustion. Therefore, after-
burners and scrubbers are usually required to treat the exhaust gases. The induced draft fan of a MHF could
produce a noise problem, if not controlled. It should be noted that carbon regeneration will eliminate a solids
handling problem caused by the spent carbon (See Fact Sheet 4.4.1).
References 50, 115
A-134
-------
ACTIVATED CARBON THERMAL REGENERATION
FACT SHEET 4,1,2
FLOW DIAGRAM
Make-up Carbon
r-tX-
Spent Carbon
XX
A A
T\TX
\ Regener
^ I art A C f-/>
Water Back
^
to Process
[R
^la
rated Carbon Defining
J
,
Lning
1
Spent Carbon Drain i
Storage Tanks
^
I
I
ind
JI
\
' Cart
o
n
IAir
Poll
Fuel S
<
Steam
Reaener
and Storage Tanks
Furnace
Carbon Fines
ENERGY NOTES (116) -
Electricity = 0.004-0.046 kWh/lb of carbon
regenerated. Rate decreases with increasing
scale.
Fuel = 4300-6800 Btu/lb. Rate decreases with
increasing scale.
Steam = 0.6 Ib/lb
Regenerated Carbon
120,000
•g 30,000 —^^~
1,000 -
9 r-l
10 2U 30 40 50 60 70
Thousand Ib/d of Carbon Regenerated
COSTS* (116) - Assumptions: 1977 dollars; ENR Index = 2577
1. Carbon loss 5 percent per regeneration.
2. Equipment includes dewatering feed screw, quench tank, afterburner, scrubber, furnace and controls, two
storage tanks and steam generator.
3. Operating costs are based on maintenance costs of 15 percent of constructed costs/yr. Carbon
make-up - $.50/lb.
CONSTRUCTION COSTS
OPERATION & MAINTENANCE COSTS
1000
600
200
^_
1000
800
600
400
0 10 20 30 40 50 60 70
Thousand Ib/d of Carbon Regenerated
REFERENCES - 50, 116
*To convert construction cost to capital cost see Table A-2.
A-135
10 20 30 40 50 60 70
Thousand Ib/d of Carbon Regenerated
-------
OZONE OXIDATION (AIR AND OXYGEN) FACT SHEET
Description - Ozone (0 ) is a very strong oxidant. At dosages of 10 to 300 mg/1, ozone may be used to remove
residual dissolved organics in secondary effluent. Ozone has also been experimentally used to treat raw wastewatej
and wastewater after various stages of treatment. The rate of oxidation is both temperature and pH dependent.
Reaction rates increase with increasing temperature. Because there is a wide range of ozone reactivity with the
diverse organic content of wastewater, both the required ozone dose and reaction time are dependent on the quality
of the influent to the ozonation process. Generally, higher doses and longer contact times are required for ozone
oxidation reactions than are required for wastewater disinfection using ozone. Ozone tertiary treatment may
eliminate the need for a final disinfection step. Ozone breaks down to elemental oxygen in a relatively short
period of time (half life about 20 minutes). Consequently, it must be generated on site using either air or oxygei
as the feed gas. Ozone generation utilizes a silent electric arc or corona through which air or oxygen passes, and
yields an ozone in air/oxygen mixture, the percentage of ozone being a function of voltage, frequency, gas flow
rate and moisture. Automatic devices are commonly applied to control and adjust the ozone generation rate.
Common Modifications - Systems have been designed which utilize staged contactors (injection type) with recycle of
the ozone/oxygen off-gas. On these systems, provision must be made for the removal of nitrogen gas from the
influent wastewater stream and for the removal of reaction-produced carbon dioxide from the off-gas stream in thos<
situations that warrant it.
Technology Status - It is a developing technology. Recent developments and cost reduction in ozone generation and
ozone dissolution technology make the process more competitive. A full scale application is currently in the
start-up stage.
Applications - The process is feasible as a tertiary treatment for oxidation of residual dissolved organics,
cyanides, organic N compounds and other toxics susceptible to the highly active oxidation characteristics of
ozone. If oxygen-activated sludge is employed in the system, ozone treatment may be economically attractive, sinc<
a source of pure oxygen is available facilitating ozone production.
Limitations - For poor quality wastewater with high COD, BOD and/or TOC contents (greater than 300 mg/1) , ozone
treatment may be uneconomical due to high ozone consumption. COD removal is generally limited to around 70 per-
cent. May not be effective in oxidizing some halogenated hydrocarbons.
Typical Equipment/No, of Mfrs.(77, 130) - Oxygen generator/5; Columns-towers/60; Ozone auxiliary equipment/8; Ozom
generator/10.
Performance - The following table shows the reduction of overall COD, BOD , and TOC, achieved in laboratory tests
after a 90 minute contact time with ozone (128).
COD, mg/1 BOD , mg/1 TOC, mg/1
Ozone Dosage, mg/1 Influent Effluent Influent Effluent Influent Effluent
50 318 262 142 110 93 80
100 318 245 142 100 93 77
200 318 200 142 95 93 80
325 318 159 142 60 93 50
50 45 27 13 7 20.5 15.5
100 45 11 13 3 20.5 9
200 45 5.5 13 1.5 20.5 5
Beyond the 70 percent COD removal level, the oxidation rate is significantly slowed. In laboratory tests, COD
removal never reaches 100 percent even at a high ozone dose of 300 mg/1.
Chemicals Required - Air or pure oxygen may be used as the feed gas to the ozone generator.
Design Criteria -
Contact time: 1 to 90 min Ozone production 4.5 kWh/lb from oxygen, 7.5 kWh/lb from air
Dosage rate: 10 to 300 mg/1 pH range: 5 to 11 (6 to 8 optimum)
Reliability - Mechanical reliability is good.
Environmental Impact - Ozone in off gases which are not destroyed is an air pollutant in the lower atmosphere whicl
can discolor or kill vegetation coming in contact with it. Inhalation toxicology of ozone is both exposure dura-
tion and concentration dependent.
Toxics Management - Ozone has been found to be a good oxidant for removal of cyanide, phenol and other dissolved
toxic organic materials.
References - 77, 95, 128, 130, 132, 172
A-136
-------
OZONE OXIDATION (AIR AND OXYGEN)
FACT SHEET
FLOW DIAGRAM -
Air
Purge
J, Catalytic
Ozone
Decomp.
ENERGY NOTES - 1,927,200 kWh/yr/Mgal/d are the estimated energy requirements for a 75 mg/1 ozone dosage derived
from an oxygen feed.
COSTS* - Assumptions: 1971 prices; ENR Index = 1581
JT. Construction costs are based on an ozone dosage of 75 mg/1 derived from an oxygen feed.
2. Construction costs include deaerators, process pumps, injector and mixers, reactors and holding tanks, oxygen
compressors, dryers, ozone generators, sumps and draws, ozone decomposer.
3. Total operation and maintenance costs include electricity, oxygen, maintenance and labor.
4. Labor = $5/hr plus 30 percent for overhead and supervision; electricity = $.02/kWh.
CONSTRUCTION COSTS
OPERATION & MAINTENANCE COSTS
100
10
01
10
_ 01
o.i
1.0 10
Wastewater Flow, Mgal/d
001
Total
-Electricity»
rOxygen
100
0.1
1.0 10
Wastewater Flow, Mgal/d
100
REFERENCES - 3, 95, 172
*To convert construction cost to capital cost see Table A-2.
A-137
-------
CHLORINATION (DISINFECTION)
FACT SHEET H.5.1
Description - Chlorination is the most commonly used wastewater disinfection process. This process involves the
addition of elemental chlorine or hypochlorite to the wastewater. When chlorine is used, it combines with water
to form hypochlorous (HOC1) and hydrochloric (HC1) acids. Hydrolysis goes virtually to completion at pH values
and concentrations normally experienced in municipal wastewater applications. Hypochlorous acid will ionize to
hypochlorite (OC1) ion, with the amount greatly affected by pH. However, hypochlorous acid is the primary disin-
fectant in water. In wastewater, the primary disinfectant species is monochloramine. Therefore, the tendency of
hypochlorous acid to dissociate to hypochlorite ion should be discouraged by maintaining a pH below 7.5.
The amount of chlorine added is determined by cylinder weight loss. Chlorine demand is determined by the dif-
ference between the chlorine added and the measured residual concentration after a certain period has passed from
the time of addition. This is usually 15-30 minutes. The chlorine or hypochlorite is rapidly mixed with the
wastewater, after which it passes through a detention tank, which normally contains baffled zones to prevent short
circuiting of wastewater.
Common Modifications - Chlorine or hypochlorite salts can be used. The two most common hypochlorite salts are
calcium and sodium hypochlorite. Dechlorination may be used, which generally involves the addition of sulfur
dioxide (see Fact Sheet 4.5.2), aeration, or even activated carbon, when chlorine residual standards are strict.
Technology Status - Chlorination of water supplies on an emergency basis has been practiced since about 1850.
Presently, Chlorination of both water supplies and wastewaters is an extremely wide-spread practice.
Typical Equipment/No, of Mfrs. (77)- Chlorine analyzers/25; pH controllers/25; Chemical feeders/27; Mixers/26.
Applications - Chlorination for disinfection is used to prevent the spread of waterborne diseases and to control
algae growth and odors.
Limitations - May cause the formation of chlorinated hydrocarbons, some of which are known to be carcinogenic
compounds. The effectiveness of Chlorination is greatly dependent on pH and temperature of the wastewater.
Chlorine gas is a hazardous material, and requires sophisticated handling procedures. Chlorine will react with
certain chemicals in the wastewater, leaving only the residual amounts of chlorine for disinfection. Chlorine
will oxidize ammonia, hydrogen sulfide, as well as metals present in their reduced states.
Performance - It should be noted that disinfection is designed to kill harmful organisms, and generally does not
result in a sterile water (free of all microorganisms). The following tablg presents coliform remaining after 30
minutes of chlorine contact time assuming primary effluent contains 35 x 10 total coliform/100 ml prior to dis-
infection, and secondary effluent contains 1 x 10 total coliform/100 ml prior to disinfection. The values given
are dependent upon good mixing in a highly turbulent regime followed by ideal plug flow conditions in the contact
chamber. If these conditions do not exist, a definitive relation between C12 residual and coliform reduction
cannot be expected. Predictability of results from Chlorination is also affected by wastewater characteristics
and treatment processes used.
Total Coliform MPN/100 ml
Chlorine Residual, mg/1
0.5 - 1.5
1.5 - 2.5
2.5 - 3.5
3.5 - 4.5
Primary Effluent
24,000 - 400,000
6,000 - 24,000
2,000 - 6,000
1,000 - 2,000
Secondary Effluent
1,000 - 12,000
200 - 1,000
60 - 200
30 - 60
In normal low dose disinfection treatment, the COD,
changed.
BOD , and TOC of the treated wastewater are not measurably
Chemicals Required - Chlorine, sodium hypochlorite, or calcium hypochlorite.
Design Criteria - Generally a contact period of 15-30 minutes at peak flow is required. Detention tanks should be
designed to prevent short circuiting. This usually involves the use of baffling. Baffles can either be the over-
and-under or the end-around varieties. Residuals of at least 0.5 mg/1 are generally required. The following
table presents typical dosages for disinfection:
Dosage range,
Effluent From mg/1
Untreated wastewater(prechlorination)
Primary sedimentation
Chemical-precipitation plant
Trickling-filter plant
Activated-sludge plant
Multimedia filter following activated-sludge plant
Unit Process Reliability - Extremely reliable.
6-25
5-20
3-10
3-10
2-8
1-5
Environmental Impact - Can cause the formation of chlorinated hydrocarbons. Chlorine gas may be released to the
atmosphere. Relatively small land requirements.
References - 3, 26, 7, 11, 77, 126, 127, 129, 140, 146.
A-138
-------
CHLORINATION (DISINFECTION)
FACT SHEET 4.5.1
LOW DIAGRAM -
Chlorinator
Chlorine gas
Solution water
Chlorine
Eductor
Influent
Effluent
Contact Tank
Mixing Tank
(Optional)
L.K^Y i4L>'''r_S - energy requirements lor chlorination are derived principally froi.i water used for the vacuum eductors
and the evaporators when used. For the example below, total energy requirements are 10,000 kWh/yr/Mgal/d, 1,200
kWh/yr/Mgal/d and 200 kWh/yr/Mgal/d, respectively, for a 1 Mgal/d, 10 Mgal/d and 100 Mgal/d facility. Eductor
water requirements can vary widely from site to site. Facilities using more than 1,000 Ib chlorine/d generally use
electrically heated evaporators for conversion of the liquid chlorine to gas. The heat of vaporization of chlorine
is 111 Btu/lb @ 60°F. Approximate energy required for the evaporator can be computed by the following equation:
kWh/yr = 11.8 X Ib chlorine/d. Mixing is not included.
COSTS - Assumptions:
Service life: 15 years
Equipment: Including chlorine supply, chlorinator, and contact chamber
Dosage = 10 mg/1; contact time = 30 minutes for average flow
Labor rate = ?7.50/h, including benefits
Power cost = $.02/kWh; chlorine cost = $160/ton
Index: ENR = 2475, September 1976.
10
-4-44.4444—4-1-a-4
CONSTRUCTION COST±±rrt4-
10 10
Wastewater Flow, Mgal/d
i
0001
0
10 10
Wastewater Flow, Mgal/d
REFERENCE - 3
•To convert construction cost to capital cost see Table A-2.
A-139
-------
DECHLORINATION (SULFUR DIOXIDE) FACT SHEET 4,5,2
Description - Since about 1970, much attention has been focused on the toxic effects of chlorinated effluents.
Both free chlorine and chloramine residuals are toxic to fish and other aquatic organisms. Dechlorination
involves the addition of sulfur dioxide to the wastewater, whereby the following reactions occur:
SO2 + HOC1 + H20 = SO4+ + Cl" + 3H+ (For free chlorine)
SO + NH Cl + 2H20 = S04+2 + Cl~ + 2H+ + NH4+ (For combined chlorine)
As can be seen, small amounts of sulfuric and hydrochloric acids are formed; however, they are generally neutral-
ized by the buffering capacity of the wastewater. Dechlorination can also be used in conjunction with super-
chlorination. Since superchlorination involves the addition of excess chlorine, dechlorination is required to
eliminate this residual. Sulfur dioxide is the most common chemical used. It is fed as a gas, using the same
equipment as chlorine systems. Because the reaction of sulfur dioxide with free or combined chlorine is practi-
cally instantaneous, the design of contact systems are less critical than that of chlorine contact systems.
Detention of less than 5 minutes is quite adequate, and in-line feed arrangements may also be acceptable under
certain conditions.
Common Modifications - Metabisulfite, bisulfite, or sulfite salts can be used. Automatic or manually fed systems
can also be used. If chlorine is used at the site, sulfur dioxide is preferred, since identical equipment can be
used for the addition of both chemicals. Alternative dechlorination systems include activated carbon, HO, and
ponds (sunlight and aeration).
Technology Status - The technology of dechlorination with sulfur dixoide is established, but is not in widespread
use. A few plants in California and at least one in New York are known to be practicing effluent dechlorination
with SO on either a continuous or intermittent basis.
Typical Equipment/No, of Mfrs. (23) - Chemical feeders/27; mixers/26; Automatic controls/over 50.
Applications - Can be used whenever a chlorine residual is undesirable. This usually occurs when the receiving
water contains aquatic life sensitive to free chlorine. Is generally required when superchlorination is practiced
or stringent effluent chlorine residuals are dictated.
Limitations - Will not destroy chlorinated hydrocarbons already formed in the wastewater. It has been reported
that about 1 percent of the chlorine ends up in a variety of stable organic compounds when municipal wastes are
chlorinated.
Performance - Available chlorine residuals can be reduced to essentially zero by sulfur dioxide dechlorination.
Chemicals Required - Sulfur dioxide (SO.) and Sulfite salts are the most common chemicals used. Sodium meta-
bisulfite (Na S 0 ) can also be used, but is much less common. In fact, any reducing agent can be considered,
depending on cost and availability.
Residuals Generated - None
Design Criteria - Contact Time: 1-5 minutes: Sulfur Dixoide Feed Bate: 1.1 pounds per pound of residual chlo-
rine; Sodium Sulfite Feed Rate: 0.57 pound per pound of chlorine; Sodium Bisulfite Feed Rate: 0.68 pound per
pound of chlorine; Sodium Thiosulfate Feed Rate: 1.43 pounds per pound of chlorine.
Unit Process Reliability - Sulfur dioxide addition for dechlorination purposes is reasonably reliable from a
mechanical standpoint. The greatest problems are experienced with analytical control which may lower the process
reliability.
Environmental Impact - Requires very little use of land, and no residuals are generated. It is used to eliminate
the environmental impact of chlorine residuals. Overdosing can result in low pH and low DO effluents, however.
References - 7, 48
A-140
-------
DECHLORINATION (SULFUR DIOXIDE)
FACT SHEET 4,5,2
FLOW DIAGRAM -
Sulfonator
ENERGY NOTES - Energy requirements for SO. dechlorination are derived principally from water used for the vacuum
eductors and the evaporators when used. For the example below, total energy requirements are 10,000 kWh/yr/
Mgal/d, 1,200 kWh/yr/Mgal/d and 200 kWh/yr/Mgal/d, respectively, for a 1 Mgal/d, 10 Mgal/d and 100 Mgal/d facil-
ity. Eductor water requirements can vary widely from site to site. Facilities using more than 1,000 Ib SO /d
generally use electrically heated evaporators for conversion of the liquid S02 to gas. The heat of vaporization
of SO is 158 Btu/lb @ 60 F. Approximate energy required for the evaporator can be computed by the following
equation: kWh/yr = 16.8 X Ib SO /d. Mixing is not included
COSTS* - Design Basis: Assumptions: ENR Index - 2475
Y.Construction costs include S02 feed facilities, reaction tank (1 minute detention time), mixer, and storage
facilities; building space not included.
2. S02 costs are based on 20 Ib/Mgal (1.1 rag/1 of SO required per mg/1 of chlorine residual).
3. No control instrumentation included.
SO Costs -
150 Ib cylinder $450/t
2,000 Ib. cylinder 215/t
Tank Car 155/t
1 0
CONSTRUCTION COST
OPERATION & MAINTENANCE COST
01
Q
o
001
0001
1 0
Q 0 1
Si
001
0 1
REFERENCE - 3
1 0 10
Wastewater Flow, Mgal/d
100
0001
Total
Labor7
-Materials
"Power"
0 1
001 £
o
0001 *
1 0 10
Wastewater Flow, Mgal/d
100
00001
*To convert construction cost to capital cost see Table A-2.
A-141
-------
OZONE DISINFECTION (AIR AND OXYGEN) FACT SHEET 4.b.
Description and Common Modifications - Ozone (0 ) may be used for the final disinfection step in a wastewater
treatment process. As a disinfectant (dosages of 3 to 10 mg/1 are common), ozone is an effective agent for
deactivating common forms of bacteria, bacterial spores and vegetative microorganisms found in wastewater, as
well as eliminating harmful viruses. Additionally, ozone acts to chemically oxidize materials found in the
wastewater and can reduce the BOD and COD, forming oxygenated organic intermediates and end products. Further,
ozone treatment reduces wastewater color and odor.
Ozone breaks down to elemental oxygen in a relatively short period of time (half life about twenty minutes).
Consequently, it is generated on site using either air or oxygen as the raw material. The ozone generation
process utilizes a silent electric arc or corona through which air or oxygen passes yielding a certain percentage
of ozone. Automatic devices are commonly applied to control voltage treatment, frequency, gas flow and moisture,
all of which influence the ozone generation rate. Ozone injection into the wastewater flow may be accomplished
via mechanical mixing devices, countercurrent or co-current flow columns, porous diffusers or jet injectors.
Ozone acts quickly and consequently requires a relatively short contact time. Ozonation as a tertiary treatment
process to reduce BOD and COD is covered in Fact Sheet 4.4.3.
Technology Status - Fully demonstrated but not widely used in the united States because of relatively high cost
of ozone. Recent developments in ozone generation have lowered the cost and thus make it more competitive with
other disinfection methods.
Applications - Applicable in cases where chlorine disinfection may produce potentially harmful chlorinated organic
compounds. If oxygen-activated sludge is employed in the system, ozone disinfection is economically attractive,
since a source of pure oxygen is available facilitating ozone production.
Limitations - Ozone disinfection does not form a residual that will persist and can be easily measured to assure
adequate dosage. Ozonation may not be economically competitive with chlorination under non-restrictive local
conditions.
Effluents containing high levels of suspended solids may require filtration to make ozone disinfection more cost-
effective.
Typical Equipment/No, of Mfrs. (77, 130) - Oxygen Generator/5; Columns-Towers/60; Ozonation auxiliary equipment/8;
Ozone Generator/10.
Performance - Easily oxidizable wastewater organic materials consume ozone at a faster rate than disinfection;
therefore, effectiveness of disinfection is inversely correlated with effluent quality but directly proportional
to ozone dosage. When sufficient ozone is introduced, ozone is a more complete disinfectant than chlorine.
Results of disinfection by Ozonation have been reported by various sources as follows (11):
Influent Dose, mg/1 Contact Time, minutes Effluent Residual
Secondary effluent 5.5-6.0 Less than or equal to 1 Less than 2 fecal coliforms/100 ml
Secondary effluent 10 3 99% inactivation of fecal coliform
Secondary effluent 1.75-3.5 13.5 Less than 200 fecal coliform/100 ml
Drinking water 4 8 Sterilization of virus
Chemicals Required - Air or pure oxygen may be used as the raw material for the ozone generation.
Design Criteria (131) -
Contact time: 1 to 16 minutes
Dosage: 5 to 10 mg/1
Reliability - Mechanically highly reliable. Highly reliable in deactivating microorganisms.
Toxics Management (132) - Ozone has been found to be a good oxidant for removal of cyanide, phenol and other
dissolved toxic organic materials. Combination of ozonation and activated carbon treatment can achieve 95 percent
chloroform and other trihalomethanes removals.
Environmental Impact - Ozone is an air pollutant which can discolor or kill vegetation coming in contact with it.
Residual ozone in off-gas streams must be processed for ozone decomposition prior to release. Ozone is toxic
when inhaled in sufficient concentration.
References - 3, 10, 11, 39, 77, 126, 128, 129, 130, 131, 132
A-142
-------
OZONATION DISINFECTION (AIR AND OXYGEN)
FACT SHEET 4.5.3
FLOW DIAGRAM -
Secondary Effluent _
tor
i
03 Out Thermal j
Ozone
Contactor
Effluent
Vent
ENERGY NOTES - The energy requirement is 750 kWh/Mgal of wastcwacer i.reatea if ozone is generaujd from air and 550
kWh/Hgal if ozone is generated from oxygen. These requirements are based on the assumption that the energy
required for tue production of ozone is 7.5 kWh/lb of ozone when generated from air and 4.5 kWh/lb when generated
from oxygen.
COSTS* - Assumptions: Service Life = 30 years
Design Basis:
TIEquipment: 0 storage or air supply ozonator, injector, contact chamber, aeration chamber.
2. O requirements: 3 Ib/lb of O , ozone dosage: 8 mg/1.
3. Labor rate: $7.50/h, including benefits, power cost: $.02/kWh.
4. Index: ENR = 2475, September 1976.
Ozonation — Air
10
CONSTRUCTION COST
OPERATION & MAINTENANCE COST
1 0
O
Q
01
001
s
t 001
0001
Tola
Power—
Matena
0 1
Ozonalion — Oxygen
10
1 0 10
Wastewater Flow, Mgal/d
CONSTRUCTION COST
100
01 10 10
Wastewater Flow, Mgal/d
OPERATION & MAINTENANCE COST
100
0.0001
llars
0
01
001
001
:! 0001
01
100
1 0 10
REFERENCE - 3 Wastewater Flow, Mgal/d
*To convert construction cost to capital cost see Table A-2.
0001
00001
01
1 0 10
Wastewater Flow, Mgal/d
100
A-143
-------
ALUM ADDITION FACT SHEET 5,1,1
Description and Common Modifications - Alum or filter alum, Al (SO ) . 14H O, is a coagulant which when added to
wastewater reacts with available alkalinity (carbonate, bicarbonate and hydroxide) and phosphate to form insoluble
aluminum salts. The combination of alum with alkalinity or phosphate are competing reactions which are pH depen-
dent. Alum is an offwhite crystal which when dissolved in water produces acidic conditions. As a solid, alum may
be supplied in lumps, or in ground, rice or powdered form. Shipments may be in small bags (100 Ib), in drums or
in bulk quantities (over 40,000 Ib). In liquid form, alum is commonly supplied as a 50 percent solution delivered
in minimum loads of 4000 gal. The choice between liquid or dry alum use is dependent on factors such as availa-
bility of storage space, method of feeding and economics. In general, purchase of liquid alum is justified only
when the supplier is close enough to make differences in transportation costs negligible. Dry alum is stored in
mild steel or concrete bins with appropriate dust collection equipment. Since dry alum is slightly hydroscopic,
provisions are made to avoid moisture which could cause caking and corrosive conditions. Before addition to
wastewater, dry alum must be dissolved, forming a concentrated solution. Bulk stored or hopper filled alum is
transported by either bucket elevator, screw conveyor or a pneumatic device to a feeder mechanism. Three basic
types of feeders are in common use: volumetric, belt gravimetric and loss-in-weight gravimetric. The feeder
supplies a controlled quantity of dry alum (accuracy ranges from about 1-7%) to a mixed dissolver vessel. The
quantity supplied depends on the concentrate strength desired and the temperature, since alum solubility is
temperature dependent. Because alum solution is corrosive, the dissolving chamber as well as following storage
tanks, pumps, piping and surfaces that may come in contact with the solution or generated fumes must be constructed
of resistant materials such as type 316 stainless steel, fiberglass reinforced plastic (FRP) or plastics. Rubber
or saran lined pipes are commonly used. Liquid alum, which crystallizes at about 30 F and freezes at about 18 F,
is stored and shipped in insulated type 316 stainless steel or rubber-lined vessels. Feeding of liquid alum (pur-
chased or made up on site) to wastewater treatment unit processes may be accomplished by gravity, via pumping or
by using a roto dip-type feeder. Diaphragm pumps and valves are common.
Technology Status - Alum addition has been used for decades for coagulation and turbidity reduction in water
treatment. Application to wastewater treatment is more recent and the technology well demonstrated.
Applications - Alum is used in wastewater treatment (sometimes in conjunction with polymers) for suspended solids
and/or phosphorus removal. Alum coagulation may be incorporated into independent physical-chemical treatment,
tertiary treatment schemes or as an add-on to existing treatment processes. In independent physical-chemical
treatment (or tertiary treatment), alum is added directly to the wastewater, which is intensely mixed, floc-
culated and settled. Solids contact clarifiers may be used. In existing wastewater treatment process, alum may
be added directly to primary clarifiers, secondary clarifiers or aeration vessels to improve performance. It
should not be dosed directly to trickling filters because of possible deposition of chemical precipitates on the
filter media. Alum has also been used as a filter aid in tertiary filtration processes and has been used to
upgrade stabilization pond effluent quality.
Limitations - Alum solution is a corrosive material. Appropriate dosages are not stoichoimetric and must be re-
confirmed frequently. Alkalinity is required for proper coagulation, and where inadequate, supplemental alka-
linity must be provided (usually by lime addition). Alum sludge is voluminous and difficult to dewater.
Typical Equipment/No. Mfrs. (97-100) - Bins/over 50; Hoppers/over 40; Conveyors and Elevators/over 50; Liquid
Storage tanks/over 50; Dry and Wet Feeders/over 50: pH instrumentation/over 50.
Performance - Typical performance for existing treatment plants using alum for upgrading are as follows:
Treatment System Type Trickling Filter Trickling Filter Activated sludge Activated Sludge
Point of Addition Final Clarifier Primary Clarifier Final Clarifier Aeration Tank
Effluent BOD , mg/1 10-25 20-30 10-25 15-25
Effluent SS, mg/1 15-30 20-40 10-30 15-30
Effluent P, mg/1 0.5-2.0 1.0-3.0 0.2-1.5 0.5-1.5
Chemicals Required - The amount of alum required depends on multiple factors such as alkalinity and pH of waste-
water, phosphate level and point of injection. Accurate dosages should be determined by jar tests and confirmed
by field trials.
Residuals Generated - Alum sludges are substantially different in character from biological sludges in that
volumes are greater and dewatering is more difficult. Alum sludge also has a tendency to induce undesirable
stratification in anaerobic digesters.
Design Criteria (99) - Dosage: Determined by jar testing, generally in the range of 5-20 mg/| as Al; Mixing: G =
(approximately) 300/s, t is less than or equal to 30 s; Flocculation: GT = (approximately) 10 or, GCT = (approx-
imately) 100; Sedimentation: Overflow Rate = 500 to 600 gal/d/ft (average), 800 to 900 ga/d/ft (peak).
Unit Process Reliability - Reduces phosphate and suspended solids to low levels, although the effluent quality may
vary unless filtration follows the clarification step.
Toxics Management - Alum is an effective chemical for precipitating and removing many heavy metals in wastewater.
Among the metals reduced in concentration by more than 50 percent by alum coagulation are zinc, copper, barium,
lead, chromium (III) and arsenic.
References - 29, 95, 97, 99, 100
A-144
-------
ALUM ADDITION
FACT SHEET 5,1,1
FLOW DIAGRAM
Dry Alum
Storage
Mixer
r .
Conveyor
Feeder
°£
Dissolver
Holding
Tank
Metering Pump
I
Liquid Alum
ENERGY NOTES - Assumptions:
1. Power consumption based on the operation
of pumps, mixers and feeders.
2. Alum dosage = 200 mg/1 as Al {SO ) .14 H
3. Type of energy: Electrical
COSTS - Assumptions:
T. Alum dosage = 200 mg/1 as A12(SO4)3.14 H2O.
Phosphorus removal for other dosages, see
adjustments below.
2. The rapid mix tank is constructed of concrete,
and multiple basins are used for volumes greater
than 1,500 ft .
3. Costs include liquid alum (8.3% Al 0 ) ,
chemical feed equipment sized for twice the
average feed rate and storage of at least 15 days.
Price of building is included except for plants
with a capacity of less than 1 Mgal/d. Rapid mix
tank includes stainless steel mixer.
4. Service life = 20 years.
5. ENR Index = 2475.
Dry Alum
10
10'
^ 10
10
7
7
Adjustment factor: To adjust cost curves for other alum dosages,
enter cost curve at effective flow (Q ) :
0.1 1.0 10
Uastewater Flow, Mqal/d
100
E ^DESIGN
10
X Alum Dose
200 mg/1
s
o
I
10 10
Wastewater Flow. Mgal/d
!0 10
Wastewater Flow, Mgal/d
REFERENCE - 3
*To convert construction cost to capital cost see Table A-2.
A-145
-------
FERRIC CHLORIDE ADDITION FACT SHEET 5.1.2
Description and Common Modifications- Ferric chloride (Fed ) is a chemical coagulant which when added to waste-
water reacts with alkalinity and phosphates, forming insoluble iron salts. The colloidal particle size of insol-
uble FePO is small, requiring excess dosages of FeCl to produce a well flocculated iron hydroxide precipitate
which carries the phosphate precipitate. Large excesses of ferric chloride, and corresponding quantities of
alkalinity, are required to assure phosphate removal. Exact ferric chloride dosages are usually best determined
by jar tests and full scale evaluations. Ferric chloride is available in either dry (hydrated or anhydrous) or
liquid form. Liquid ferric chloride is a dark brown oily-appearing solution supplied in concentrations ranging
between 35 and 45 percent FeCl . Because higher concentrations of ferric chloride have higher freezing points,
lower concentrations are supplied during winter. Liquid ferric chloride is shipped in 3,000 to 4,000 gallon bulk
truckload lots, in 4,000 to 10,000 gallon carloads and in 5 to 13 gallon carboys. Ferric chloride solution
stains surfaces it comes in contact with and is highly corrosive (a 1 percent solution has a pH of 2.0). Conse-
quently, it must be stored and handled with care. Storage tanks are equipped with vents and vacuum relief valves.
Tanks are constructed of fiberglass reinforced plastic, rubber lined steel and plastic lined steel. Because of
freezing potential, ferric chloride solutions are either stored in heated areas or in heated and insulated vessels
in northern climates. Ferric chloride solution should not be diluted because of possible unwanted hydrolysis.
Consequently, feeding at the concentration of the delivered product is common. The stored solution is transferred
to a day tank using graphite or rubber lined self-priming centrifugal pumps with corrosion resistant Teflon
seals. From the day tank, controlled quantities are fed to the unit process using rotodip feeders or diaphragm
metering pumps. Rotometers are not used for ferric chloride flow measurement because of its tendency to deposit
on and stain the glass tubes. All pipes, valves or surfaces that come in contact with ferric chloride must be
made of corrosion resistant materials such as rubber or Saran lining, Teflon or vinyl. Similar treatment results
are obtainable by substituting ferrous chloride, ferric sulfate, ferrous sulfate or spent pickle liquor for
ferric chloride. Details of storage feeding and control for these materials are similar to those for ferric
chloride. Dry ferric chloride may also be dissolved on site before use in treatment.
Technology Status - Ferric chloride is commonly used in water treatment as a coagulant for turbidity reduction.
Its use in wastewater treatment is more recent and well demonstrated.
Applications - Ferric chloride (sometimes with polymer addition) is used in wastewater treatment for suspended
solids removal and/or phosphate removal. FeCl coagulation may be incorporated into independent physical-chemical
treatment and tertiary treatment schemes. In these applications, solids contact clarifiers or separate floccula-
tion vessels are used for the treatment of either raw wastewater or secondary effluent. Ferric chloride coagu-
lation may also be applied to existing treatment systems. Addition of ferric chloride before primary and second-
ary clarifiers has been practiced in both activated sludge and trickling filter plants.
Limitations - Ferric chloride is an extremely corrosive material which must be stored and transported in special
corrosion resistant equipment. Dosages are not stoichiometric and must be rechecked frequently via jar tests.
Ferric chloride coagulation requires a source of alkalinity, and in soft wastewaters, the pH of the clarified
effluent might be decreased to a point requiring pH adjustment by addition of a supplemental base such as lime or
caustic soda. Iron concentrations in plant effluents may become unacceptably high.
Typical Equipment/No, of Mfrs. (97, 100) - Liquid storage tanks/over 50; Dry and Wet feeders/over 50; pH instru-
mentation/over 50.
Performance (230) - Phosphorus removal studies at Baltimore, Maryland showed the following P (mg/1) levels:
Primary Effluent Prior Secondary Effluent (After Fe Addition)
to Fe Addition Activated Sludge % Removal Trickling Filter % Removal
7762.1 72 7.2 5
8.2 0.85 90 5.8 29
8.0 0.58 93 3.8 53
8.6 0.29 97 3.9 55
7.7 0.32 96 3.3 57
Chemicals Required - The amount of ferric chloride required depends on variable factors including pH and alka-
linity of the wastewater, phosphate level, point of injection and mixing modes. Accurate doses should be deter-
mined by jar tests and confirmed by field evaluations. Base addition may be required when treating soft waste
waters.
Residuals Generated - Used in standard biological processes, ferric chloride addition will increase the volume of
sludge generated. Based on a full-scale study conducted in Baltimore, Maryland, the additional sludge generated
by adding 15 mg/1 Fe was 0.6 wet tons/Mgal. Iron coagulants' produce sludges that are significantly different
from biological sludges, especially in terms of dewatering characteristics.
Design Criteria (99) - Dosage: Determined by jar testing. Dosages of 20-100 mg/1 FeCl are common.
Mixing: G = (approximately) 300/s; t is less than or equal to 30/s.
Reliability - Reduces phosphate and suspended solids to low levels, although the effluent quality may vary unless
filtration follows the clarification step.
Toxics Management - Ferric chloride is an effective chemical for precipitating and removing many heavy metals in
wastewaters. Among the metals reduced in concentration by more than 50 percent by ferric chloride coagulation
are zinc, copper, barium, lead, chromium (III) and arsenic.
References - 29, 95, 97, 99, 100, 230
•~"~~- ~~ A-146
-------
FERRIC CHLORIDE ADDITION
FACT SHEET 5.1.2
FLOW DIAGRAM -
Ferric
Chloride
Solution
Storage
Diaphragm Metering
Pump
Rubber-Lined, Self-Priming
Centrifugal Pump with
Teflon Seals
ENERGY NOTES - Assumptions:
Power consumption based on the operation of
pumps, mixers and feeders. Fed dosage =
100 mg/1. Type of energy: Electrical.
10
10
10
10
z
COSTS - Assumptions:
0 1
1. FeCl dosage = 100 mg/1.
1 0 10
Wastewa'er F i./w Mgal/d
2. The rapid mix tank is constructed of concrete, and multiple basins are used for volumes greater than
1,500 ft .
3. Costs include liquid ferric chloride, chemical feed equipment sized for twice the average feed rate, and
storage of at least 15 days. Price of building is included except for plants with a capacity of less than
1 Mgal/d. Rapid mix tank includes stainless steel mixer.
4. Service life = 20 years.
5. ENR Index = 2475.
Adjustment factor: To adjust cost curves for other FeCl dosages, enter cost curve at effective
flow (QE) :
QE ' ^DESIGN x FeC13 fse
100 mg/1
10
CONSTRUCTION COST
001
0001
OPERATION a MAINTENANCE
Labor
' Power
01
REFERENCE - 3
10 10
Wastewater Flow, Mgal/d
01
10 10
Wastewater Flow, Mgal/d
01
0001
00001
100
*To convert construction cost to capital cost see Table A-2.
A-147
-------
LIME CLARIFICATION OF RAW WASTEWATER FACT SHEET 5.1.5
Description and Common Modifications - Lime clarification of raw wastewater removes suspended solids, while also
removing phosphates. There are two basic processes, the low-lime system and the high-lime system. The low-lime
process consists of the addition of lime to obtain a pH of approximately 9 to 10. Generally, a subsequent bio-
logical treatment system is capable of readjusting the pH through natural recarbonation. The high-lime process
consists of the addition of lime to obtain a pH of approximately 11 or more. In this case, the pH generally
requires readjusting with carbon dioxide or acid to be acceptable to the secondary treatment system.
Lime can be purchased in many forms, with quicklime (CaO) and hydrated lime (Ca(OH) ) being the most prevalent
forms. In either case, lime is usually purchased in the dry state, in bags or in bulk. Bulk lime can be (1)
shipped by trucks that are generally equipped with pneumatic unloading equipment; or (2) shipped by rail cars,
which consist of covered hoppers. The rail cars are emptied by opening a discharge gate which discharges to a
screw conveyor. The bulk lime is then transferred by the screw conveyor to a bucket elevator which empties into
the elevated storage tank. Bulk storage usually consists of steel or concrete bins. Storage vessels should be
water and air tight to prevent the lime from "slaking."
Lime is generally made into a wet suspension or slurry before being introduced into the treatment system. The
precise steps involved in converting from the dry to the wet stage will vary according to the size of operation and
type and form of limes used. In the smallest plants, bagged hydrated lime is often charged manually into a batch
mixing tank with the resulting "milk-of-lime" (or slurry) being fed via a so-called solution feeder to the process.
Where bulk hydrate is used, some type of dry feeder charges the lime continuously to either a batch or continuous
mixer, thence via solution feeder to point of application. With bulk quicklime, a dry feeder is also used which in
turn feeds a slaking device, where the oxides are converted to hydroxides, producing a paste or slurry. The slurry
is then further diluted to milk-of-lime before being piped by gravity or pumped to the process. Dry feeders can be
of the volumetric or gravimetric type.
Technology Status - Established.
Typical Equipment (97, 100) - Bins/over 50; Hoppers/over 40; Conveyors and Elevators/over 50; Liquid Storage
Tanks/ over 50; Dry and Wet Feeders/over 50; Lime Slakers/6; pH Instrumentation/over 50.
Applications - Lime addition to a primary clarifier is used for improved removal of suspended solids and the
removal of phosphates. (The primary use of this process is for the removal of phosphates.) Will also remove toxic
metals.
Limitations - Will generate additional amounts of sludge, over and above that generated by the normal primary
clarification process (approximately twice the volume for low-lime and 5 to 6 times for high lime). Lime feed
systems can require intensive operator attention. Even low-lime could present biological problems to fixed-growth
systems with no pH adjustment. Increases operator safety needs.
Performance (29) - The following table presents data from one POTW-.
Lime Treatment to pH 11 mg/1
Influent Effluent % Removal
BOD, 192 60 69
SS 195 47 76
Total Phosphorus 9.2 2.3 75
Chemicals Required - Lime (CaO or Ca(OH)2>; COj or H2SO4 for high-lime.
Residuals Generated - Sludge, which will contain 1 to 1.5 pounds of dry solids per pound of lime added, plus the
usual amount of solids produced in the primary settling process.
Design Criteria (29) - Lime requirements:
Feed Water Alkalinity Clarifier pH Approximate Lime Dose
(mg/1 as CaCO ) (mg/1 of CaO)
300 9.5 185
300 10.5 270
400 9-5 230
400 10.5 380
Unit Process Reliability - The process is highly reliable from a process standpoint, however increased operator
attention and cleaning requirements are necessary to maintain mechanical reliability of the lime feed system.
Environmental Impact - Will generate relatively large amounts of inorganic sludge that will need disposal.
References - 29, 97, 100, 102
A-148
-------
LIME CLARIFICATION OF RAW WASTEWATER
FACT SHEET 5.1.5
FLOW DIAGRAM -
To Secondary
Treatment
Lime
Feed
Lime
Storage
ENERGY NOTES - Assumptions:
Design Assumptions:
1. Slaked lime used for 0.1 to 10 Mgal/d capacity
plants
2. Quicklime used for 10 to 100 Mgal/d capacity
plants
Operating Parameters:
1. 350 mg/1, low lime as Ca(OH)
2. 600 mg/1, high lime as Ca(OHT2
3. Electrical energy at $.02/kwh
COSTS* - Assumptions: October 1973 dollars; ENR Index = 1933.
Construction costs include:
1. Chemical storage and feeding equipment
2. Hydrated lime for 0.1 to 10 Mgal/d plants
3. Pebble quicklime for 10 to 100 Mgal/d plants
4. Lime feed rates are based on a dosage of
150 mg/1 and allow for peak rates of twice
this capacity
5. Storage was provided for at least 15 days at the
average rate.
6. Piping and buildings to house the feeding equipment
are not included.
CONSTRUCTION COSTS
1 0
0 1
D
"o
5 001
0001
.1
REFERENCES - 3, 4, 29
1.0 10
Wastewater Flow, Mgal/d
100
*To convert construction cost to capital cost see Table A-2.
A-149
-0.1
PLANT CAPACITY, Mgal/d
)..! l.|) 10 HIGH LIME
1.0
10
LOW LIME
10
10
10
10'
10
100 1000
Feed Rate, Ib/hr
10,000
Operating costs include:
1. Lime cost, $27.50/ton
2. Operating costs include only the cost of lime.
They do not include depreciation of equipment.
OPERATION & MAINTENANCE COST
Q 0 1
"o
c
o
2
o
O
w 001
0001
0 1
1 0 10
Wastewater How Mgal/d
100
-------
POLYMER ADDITION FACT SHEET 5.1.6
Description and Common Modifications - Polymers or polyelectrolytes are high molecular weight compounds (usually
synthetic) which, when added to wastewater, can be used as coagulants, coagulant aids, filter aids, or sludge
conditioners. In solution, polymers may carry either a positive, negative or neutral charge and, as such, they are
characterized as cationic, anionic or nonionic. As a coagulant or coagulant aid, polymers act as bridges, reducing
charge repulsion between colloidal and dispersed floe particles, increasing settling velocities. As a filter aid,
polymers strengthen fragile floe particles controlling filter penetration and reducing particle breakthrough.
Filterability and dewatering characteristics of sludges may similarly be improved through the use of polyelectro-
lytes. Polymers are available in predissolved liquid or dry form. Dry polymers are supplied in relatively small
quantities (up to about 100 pound bags or barrels) and must be dissolved on site prior to use. A stock solution,
usually about 0.2 to 2.0 percent concentration, is made up for subsequent feeding to the treatment process.
Preparation involves automatic or batch wetting, mixing and aging. Stock polymer solutions may be very viscous.
Surfaces coining in contact with the polymer stock solution should be constructed of resistant materials such as 316
stainless steel, fiberglass reinforced plastic or other plastic lining materials. Polymers may be supplied as a
prepared stock solution ready for feeding to the treatment process. Many competing polymer formulations with
differing characteristics are available, requiring somewhat differing handling procedures. Manufacturers should be
consulted for optimum practices. Polymer stock solutions are generally fed to unit processes using equipment
similar to that commonly in service for dissolved coagulant addition. (See Fact Sheets 5.1.1 and 5.1.2 on Alum and
Ferric Chloride Addition.) Because of the high viscosity of stock solutions, special attention should be paid to
the diameter and slopes of pipes, as well as the size of orifices used in the feed systems.
Technology Status - Polymer or polyelectrolyte usage in wastewater and water treatment has gained widespread
acceptance. The technology for its use is well demonstrated and is common throughout the wastewater and water
treatment fields.
Applications - Polymers are utilized in a variety of applications in wastewater treatment ranging from flocculation
of suspended or colloidal materials either alone or in conjunction with other coagulants such as lime, alum or
ferric chloride, to use as a filter aid or sludge conditioner. Polyelectrolytes may be added alone or with other
coagulants to raw wastewater prior to primary treatment to effect or aid in suspended solids and BOD removal.
Similarly, polymers may be used to aid coagulation or as a primary coagulant in treatment of secondary effluent.
As a filter aid, polyelectrolytes effectively strengthen fragile chemical floes, facilitating more efficient filter
operations.
Limitations - Frequent jar tests are necessary to assure proper dosages. Overdosages (1.0 to 2.0 mg/1) can some-
times work against the treatment process.
Typical Equipment - Bins/over 50; hoppers/over 40; liquid storage tanks/over 50; dry and wet feeders/over 50.
Performance - Generally, improvement in unit process performance has been achieved using polymer. But the per-
formance varies depending upon its use as coagulant, coagulant aid or filter aid. Actual performance is best
determined on a case by case basis.
Chemicals Required - Accurate dosages should be determined by bench scale evaluation.
Residuals Generated - Sludges generated in conjunction with polymer addition will be somewhat different from, but
not necessarily more difficult to handle than biological sludges or chemical sludges generated without polymers.
Design Criteria - Dosage determined by jar testing. Materials contacting polymer solutions should be of the
type 316 stainless steel, fiberglass reinforced plastic or plastic construction. Storage place must be cool and
dry. Storage periods should be minimized. Viscosity considerations must be made in feeding system design.
Reliability - With proper control, capable of producing consistently high quality effluents.
Environmental Impact - May improve sludge dewaterability; operator safety should be carefully considered.
References - 23, 29, 95, 99
A-150
-------
i
M
U1
ruct
Millions of Dollars
§
w, M
;8|
Annua Cost, Millions of Dollars
(Total- Labor- Chemicals)
Energy Required, kWh/yr
(Power - Matena s)
N
C3
C3
CO
m
-------
POWDERED CARBON ADDITION
FACT SHEET 5,1.7
Description - Powdered activated carbon is used in wastewater facilities to adsorb soluble organic materials and
to aid in the clarification process. Powdered carbon is fed to a treatment system using chemical feed equipment
similar to those used for other chemicals that are purchased in dry form. The spent carbon is removed with the
sludge and can then be discarded or regenerated. Regeneration can be accomplished in a furnace or wet air oxi-
dation system.
Powdered carbon can be fed to primary clarifiers directly, or to a separate sludge recirculation type clarifier
which enhances the contact between the carbon and the wastewater. Powdered carbon can also be fed to tertiary
clarifiers to remove additional amounts of soluble organics. Powdered carbon, when added to a sludge recircu-
lation type clarifier, has been shown to be capable of achieving secondary removal efficiencies.
Powdered carbon can be fed in the dry state using volumetric or gravimetric feeders or can be fed in slurry form.
Modifications - A new technology has been developed over the past several years that consists of the addition of
powdered activated carbon to the aeration basins of biological systems. This application is capable of the
following: high BOD and COD reduction, despite hydraulic and organic overloading; aiding solids settling in the
clarifiers,- a high degree of nitrification due to extended sludge age; a substantial reduction in phosphorus;
adsorbing coloring materials such as dyes and toxic compounds; and adsorbing detergents and reducing foam (211,
212).
Technology Status - Two new municipal plants using powdered carbon addition to activated sludge are currently
under construction. Several more are planned.
Typical Equipment (2, 3, 97,
50; Slurry feeders/over 50.
100) - Powdered carbon - major producers/2; Volumetric and gravimetric feeders/over
applications - Has been used in the clarifiers and has the potential use in aeration basins to adsorb soluble
organic materials, thus removing BOD and COD, as well as some toxic materials.
Limitations - Will increase the amount of sludge generated. Regeneration will be necessary at higher dosages in
order to maintain reasonable costs. Most powdered carbon systems will require post-filtration to capture any
residual carbon particles. Some sort of flocculating agent such as an organic polyelectrolyte is usually required
to maintain efficient solids capture in the clarifier.
Performance - Physical/chemical treatment (two contact type clarifiers in series) (106)
Neutralized
Average Raw Chemical Chemical Plant
Process Treatment Results Wastewater Effluent Effluent Effluent
Turbidity, JTU
Suspended Solids, mg/1
Total P, mg/1 P
Soluble Total P, mg/1 P
Total PO , mg/1 P
Soluble, PO , mg/1 P
COD, mg/1
4'
33
87
4,50
3.16
2.82
2.25
136
4
14
0.29
0.14
0.10
0.04
4
10
0.15
0.06
0.05
55
3
5
0.20
0.11
0.11
0.08
14
Limited pilot and field scale data are available for powdered activated carbon addition to biological treatment
units and its use in municipal treatment systems.
Chemicals Required - Powdered activated carbon, polyelectrolytes.
Residuals Generated - Sludge: 1 pound of dry sludge per pound of carbon added. If regeneration is practiced,
carbon sludge is reactivated and reused with only a small portion removed to prevent buildup of inerts.
Design Criteria - The amount of powdered carbon fed to a system greatly depends on the characteristics of the
wastewater and the desired effluent quality. However, powdered carbon will generally be fed at a rate between 50
and 300 mg/1.
Process Reliability - Powdered activated carbon systems are reasonably reliable from both a unit and process
standpoint. In fact, powdered carbon systems can be used to improve process reliability of existing systems.
Environmental Impact - Land use requirements vary with application. Air pollution may result from regeneration.
Spent carbon may be a land disposal problem unless regenerated.
References - 71, 106, 150
A-152
-------
I
M
t/1
*To convert construction cost to capital cost see Table A-2.
101 10 10 100 0 1 1
Wastewater Flow. Mgal/d Wa
REFERENCE -34
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CD
S
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a
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Millions of Dollars v S „,
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2 ° 0 0 « g^
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Annua Cost, M
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-------
DEWATERED SLUDGE TRANSPORT (RAIL) FACT SHEET 6.1.1
Description - The movement by covered hopper cars, of dewatered sludge having a minimum solids content of 12
percent, from its point of origin, such as the treatment plant, to a distant designated site by common carrier
railroad. The site has been selected for the particular sludge and is proximate to an existing railroad.
Modifications -
1. Open hopper cars (not recommended for other than well digested sludge).
2. Gondola cars (not recommended for other than well digested sludge).
3. Reduced costs are possible if cars are owned by shipper (justifiable for larger plants).
Technology Status (101) -
Not in widespread use even though railroad technology is highly developed for hauling freight in countless in-
dustries.
Limitations (8, 101) - The fixed position of a railroad limits disposal site locations. Generally, a minimum of
40 miles one way for each trip and a total load of 1000 ton/d is needed to compete with truck transportation.
Scheduled deliveries of cars are difficult to predict if non-unit train operation is used.
Design Criteria (3, 101) -
Rail line should be near or next to the site to reduce length of spur or siding.
Sludge should have a density to achieve the approximate payload of the rail car.
Cars should be covered to avoid odor impact.
Cars should be gravity loaded from storage tank above car at POTW, and gravity unloaded into a hopper below
car at site.
Movement of up to 74,000 yd of sludge should be done with 50 yd (approx. 50 ton) cars (unit train concept).
Movement of greater than 75,000 yd of sludge should be done with 100 yd (approx. 100 ton) cars (unit train
concept) .
Typical Equipment/No. Mfrs. (23) - Sludge handling and control/32; conveyors/4 (83); cars, dump/27; cars, hopper/16
Reliability (8, 101) - Delivery by unit train can provide a high level of reliability through good delivery
schedules.
Environmental Impact - None for air and water. Only potential impact would result from use of open hopper or
gondola cars. Moderate impact on land because of rail spur to site, and unloading equipment and storage area at
site.
Comments (8, 101) - By virtue of its existing right of way, the railroad in many instances can provide the oppor-
tunity to use marginal or poor land of the type that can be reclaimed in some way by application of a non-specific
sludge.
Transport to the site should be one element of an integrated design for the production and ultimate disposal of
the sludge. Other important elements of this design are the methods and equipment to be used for unloading,
storage, and distributing the sludge over the site.
References - 3, 8, 83, 101, 104, 142
A-154
-------
DEWATERED SLUDGE TRANSPORT (RAIL)
FACT SHEET 6,1.1
FLOW DIAGRAM -
V.
Loading
Storage
Tank
Loading at Treatment Plant
Unloading at Site
Dewatered Sludge Loading and Unloading
ENERGY NOTES (161) - Rail transport can be considered to require approximately 25 percent of the energy in Btu/ton
mile when compared to truck transport. See Fact Sheet 6.1.2 for truck energy requirements for large vehicles
handling dewatered sludge.
• 2475
construction of loading facilities; loading storage tank sized for one carload
COSTS - Assumptions: ENR Index
1. Construction cost includes:
(cars are gravity loaded).
2. Railroad provides hopper cars.
3. Construction cost does not include any construction work and equipment at site.
4. Operation and maintenance costs include: rail haul charges, labor, electric power, and supplies for the
loading facilities; 50 yd cars for 0 to 74,000 yd of sludge; 100 yd cars for greater than 75,000 yd of sludge.
5. Rail haul charges based on travel distances of 40, 80, 160 mi one way in the central and north central areas
of the country. Adjustments for other areas of the country:
Area Approximate RR Rate Variation, (adjust accordingly)
25% higher than average
25% lower than average
10% lower than average
10% higher than average
Northeast
Southeast
Southwest
West Coast
Costs based on eight hours operation per day.
Unloading costs not included.
CONSTRUCTION COST
10
1 0
0 1
001
10
OPERATION & MAINTENANCE COST
Q 1 0
O
B 0 1
"10 10 100 1000
Annual Sludge Volume, 1000 cu yd
REFERENCES - 3, 142, 161
*To convert construction cost to capital cost see Table A-2.
A-155
0 01
80 Mile
160 M
4 M le
1 0
10 100 1000
Annual Sludge Volume, 1000 cu yd
-------
DEWATERED SLUDGE TRANSPORT (TRUCK) FACT SHEET 6.1.2
Description - The movement over highways and roads by canvas covered, hydraulic lift, dump vehicles, of dewatered
sludge having a minimum total solids content of 12 percent, from its point of origin, such as the treatment plant,
to a distant designated site. The site has been selected for the particular sludge and is accessible to a road or
highway.
Common Modifications (22, 96) -
1. Depending on state road laws, the type of vehicle would vary:
Two axle and three axle trucks.
Two axle tractor with one axle semi-trailer.
Two axle tractor with two-axle semi-trailer.
Three axle tractor with two axle semi-trailer.
Two or three axle truck with a two or three axle trailer.
2. Gasoline or diesel engine power. Diesel engine power preferred because of cheaper fuel and lower maintenance
costs.
Technology Status - Highly developed and in widespread use.
Limitations (7, 8, 96) -
State road laws which limit load of vehicle. In Ohio, for example, the maximum payloads would be:
Vehicle Payload, tons
3-axle tractor, 2 axle semi-trailer 22
3-axle truck 10
2-axle truck 7-1/2
Generally, highway and road loadings are in accordance with American Association of State Highway Officials Class
Standards H10, HIS, and H20.
Load limits may be restricted by practical on-site road conditions.
While truck transport generally has a lower initial investment cost, it will have higher operating cost relative
to rail for most levels of design volume.
Vehicles carrying sludge should be able to reach the site without passing through heavily populated areas or
business districts.
Design criteria (3, 22, 73) -
Dewatered sludge should have a minimum of 12 percent total solids.
Vehicle should be loaded by gravity from a storage tank and gravity unloaded at site.
Loading equipment should be sized to fill vehicle in 20 minutes maximum.
Size of vehicle should be selected so that density and solid content^ of sludge3achieves approximate payload of
the vehicle. For a 25 percent solid content, vehicle sizes of 10 yd and 30 yd are most cost-effective.
Loading tank should be sized to fill at least one vehicle.
Typical Equipment - Trucks and trailer equipment widely available.
Reliability - Very reliable, but dependent upon disposal site road conditions.
Environmental Impact - Small for land if temporary roads are built from highway to unloading area in site.
Potential for air pollution due to traffic of heavy trucks, especially from large plants.
Comments - Highway vehicles offer flexibility of movement to various sites when compared to rail. Transport to
the site should be one element of an integrated design for the production and ultimate disposal of the sludge.
Other important elements of this design are the methods and equipment to be used for unloading, storage, and
distributing the sludge over the site.
References - 3, 7, 8, 22, 73, 96, 142
A-156
-------
Ul
REFERENCE
Millions Of Dollors
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-------
LAND APPLICATION OF SLUDGE FACT SHEET 6.1,3
Description - Techniques for applying liquid sludge, dried sludge and sludge cake to the land include tank truck,
injection, ridge and furrow spreading, spray irrigation. Sludge can be incorporated into the soil by plowing,
discing, or other similar methods. Ridge and furrow methods involve spreading sludge in the furrows and planting
crops on the ridges, utilization of this technique is generally best suited to relatively flat land and is well
suited to certain row crops. Spray irrigation systems are more flexible, require less soil preparation and can be
used with a wider variety of crops. High application rates are commonly used to reclaim strip mine spoils or
other low quality land. Sludge spreading in forests has been limited, but offers opportunities for improved soil
fertility and increased tree growth.
Applications - Is popular as a disposal method because it is simple. Also serves as a utilization measure since
it is beneficial as a soil conditioner for agricultural, marginal, or drastically disturbed land. It contains
considerable quantities of organic matter, all of the essential plant nutrients, and a capacity to produce water
retaining humus.
Limitations - Constituents of sludge may limit the acceptable rate of application, the crop that can be grown, or
the management or location of the site. Trace elements added to soil may accumulate in a concentration that is
toxic to plants or is taken up and concentrated in edible portions of plants in a concentration that is harmful to
animals or man. Trace elements problem can be prevented by limiting the amount of sludge to be applied, indus-
trial pretreatment, selection of tolerant or non-accumulating crops, selection of crops not used in the human food
chain, and adapting appropriate agronomic practices such as liming of the soil. Where population is concentrated,
and agricultural land limited, sufficient land for sludge application may not be available. Terrain must be
carefully selected; steep slopes and low lying fields are less suitable and require more careful management.
Equipment with standard tires can cause ruts, compacted soil and crop damage or get stuck in muddy terrain.
Typical Equipment/No. Mfrs. (21) - Farm equipment or tank trucks with standard tires can be adapted for sludge
application. However, specially designed sludge application equipment with high flotation tires and apparatus for
applying liquid or dry sludge, or for subsurface injection is now available. This equipment has a 15 Ib/in
compaction factor with an 8-ton payload and does minimize rutting, compaction or crop damage when sludge applica-
tions are made under proper soil moisture conditions.
Performance - Municipal sludge contains all of the essential plant nutrients. It can be applied at rates which
will supply all the nitrogen and phosphorus needed by most crops. It may also increase the concentration in
plants of certain elements which are at or near deficiency levels for animals. For instance, animal diets are
often deficient in trace elements such as zinc, copper, nickel, chromium, and selenium. Thus sludge application
may improve the quality of feeds and forages used for animal consumption. Sludge as fertilizer can provide the
following agricultural needs:
Sludge Nitrogen Phosphate Potash
1 ton dry sludge provides 60 Ibs (50% avail) 40 Ibs 5 Ibs
Typical corn fertilizer provides (Ib/acre) 180 50 60
If 6 tons dry sludge/acre
were applied, would provide (Ib/acre) 180 (avail) 240 (avail) 30 (avail)
Design Criteria -
Application rates depend on sludge composition, soil characteristics (usually 3%N; 2%P; 0.25%K), climate,
vegetation, and cropping practices. Annual application rates have varied from 0.5 to more than 100 tons per acre.
Applying sludge at a rate to support the nitrogen needs of a crop of about 5 to 10 tons of digested solids in
the liquid form, avoids problems associated with overloading the soil. Rates based on phosphorus needs are lower.
A pH of 6.5 or greater will minimize heavy metal uptake by most crops.
Unit Process Reliability - As a disposal process, very reliable; as a utilization process, careful control should
be exercised.
Toxics Management - Soil has a variable capacity to filter, buffer, absorb, and chemically and biologically react
with a sludge's constituents. Toxics may pass through the soil unchanged, be degraded by microorganisms, react
with organic or inorganic compounds to form soluble or insoluble compounds, be adsorbed on soil colloids, or be
volatilized from the soil. Factors influencing these pathways include the physical and chemical state of the
material and of soil constituents, microbial population, solubility, pH, the cation exchange capacity, soil
aeration, moisture and temperature. Generally, most heavy metals applied to the surface are bound in the soil.
Environmental Impact - Potential for toxics and pathogens to contaminate soil, water, air, vegetation, and animal
life, and ultimately to be hazardous to humans. Accumulation of toxics in the soil may cause phytotoxic effects,
the degree of which varies with the tolerance level of the particular plant specie and variety. Toxic substances
such as cadmium that accumulate in plant tissues can subsequently enter the food chain, reaching human beings
directly by ingestion or indirectly through animals. If available nitrogen exceeds plant requirements, it can be
expected to reach groundwater in the nitrate form. Toxic materials and pathogens can contaminate groundwater
supplies or can be transported by runoff or erosion to surface waters if improper loading occurs. Aerosols which
contain pathogenic organisms may be present in the air over a landspreading site, particularly where spray irri-
gation is the means of sludge application. Some pathogens remain viable in the soil and on plants for periods of
several months; some parasitic ova can survive for a number of years. Other potential impacts include public
acceptance and odor.
References - 8, 11, 20, 21, 25, 33, 34, 66, 98
A-158
-------
LAND APPLICATION OF SLUDGE
FACT SHEET 6.1.3
ENERGY NOTES (98) - Energy required to apply sludge to land is approximately 1.2 million Btu/dry ton sludge or
58,000 Btu/wet ton sludge @ 5 percent solids, excluding transport of sludge to the site.
it
COSTS - (3) Assumptions:
Service Life 30 years; ENR = 2476
1. Construction costs include: storage lagoon (6 weeks); land preparation, monitoring wells (3 at 0.1 Mgal/d, 5
at 1 Mgal/d, 8 at 10 Mgal/d, 25 at 100 Mgal/d) and service roads.
2. Costs are for application of digested biological sludge - 900 Ib/Mgal at 4 percent solids.
3. Transport of sludge to site is not included.
4. Sludge application rate - 10 ton (dry)/acre/yr.
5. Land costs are not included.
6. Sludge application is by subsurface injection - unit attached to haul truck.
7. Operation and maintenance costs include: labor costs for sludge operation, preventive maintenance, and minor
repairs; material costs to include replacement of parts and repair performance by outside contractors.
8. If costs are desired for different application rates, enter curve at effective flow (Qg).
CE = C^CTr.M X 10 ton (dry)/acre/yr
"DESIGN
Note: Total costs
New Design Application Rate
have been derive,', from the material and labor costs given in reference 3.
CONSTRUCTION COST
OPERATION & MAINTENANCE COST
0 1
o
5 0 01
0001
Total.
. Land Preparation Cost
1 0
0 1
2 V
001
0 1
1 0 10 100
Wastewater Flow, Mgal/d
0001
Materials.
Labor-
001
0001
0 1
1 0 10
Wastewater Flow, Mgal/d
100
00001
An example of the costs for one project that utilizes high flotation equipment is provided (98).
Assumptions and Equipment Characterics
1. Equipment operates 50 wk/yr, 40 h/wk or 2000 hr/yr
2. Application rate 8000 gal/h, 5 percent dry solids
= 400 gal dry solids/h X 8.34 Ib/gal = 3336 Ib/h
= 3336 dry ton/yr.
3. Eight ton payload has 15 Ib/in compaction factor.
4. Haul distance from sludge source to spreading site
= 1/4 mile
5. Fuel consumption: diesel - 6 gal/h; gas - 9 gal/h
6. Service life - 10 yr.
7. Prices as of November 1977. ENR Index = 2659
REFERENCES - 3, 8, 98
*To convert construction cost to capital cost see Table A-2.
Operating Estimates of High Flotation Equipment
Maintenance S Repair 2,000
Fuel Cost
Diesel @ 60-?/gal 7,200
Gas @ 65/gal 11,700
Depreciation 5,000
Labor 13,800
Total Diesel 29,000
Gas 32,500
$/ton dry solids
.60
2.16
3.50
1.49
4.14
8.39
9.73
A-159
-------
SLUDGE LANDFILLING - AREA FILL
FACT SHEET 6.1.4
Description - A sludge disposal operation in which sludge is placed above the original earth cover and subsequently
:overed with soil. To achieve stability and soil bearing capacity, sludge is mixed with a bulking agent, usually
loll. The soil absorbs excess moisture from the sludge and increases its workability. The large quantities of
loil required may require hauling from elsewhere. Provisions must be made to keep the stockpiled soil dry.
installation of a liner is generally required for groundwater control and provisions made for surface drainage
:ontrol, gas migration, dust, vectors and/or aesthetics. Area fills are more specifically categorized as follows:
Area Fill Mound - Sludge is mixed with a bulking agent, usually soil, and the mixture is hauled to the filling
area, where it is stacked in mounds approximately 6 ft high. Cover material is then applied in a 3 ft thickness.
This cover thickness may be increased to 5 ft if additional mounds are applied atop the first lift. The appropriate
sludge/soil bulking ratio and soil cover thickness depend upon the solids content of the sludge as received, the
leed for mound stability and bearing capacity as dictated by the number of lifts and equipment weight. Lightweight
equipment with swamp pad tracks is appropriate for area fill mound operations; heavier wheel equipment is appro-
iriate in transporting bulking material to and from stockpiles. Construction of earthen containments is useful to
minimize mound slumping; and for sloping sites.
Area Fill Layer - Sludge is mixed with soil on or off site and spread evenly in consecutive layers 0.5 to 3 ft
thick. Interim cover between layers may be applied in 0.5 to 1 ft thick applications. Layering may continue to an
ndefinite height before final cover is applied. Lightweight equipment with swamp pad tracks is appropriate for
,rea fill layer operations; heavier wheel equipment is appropriate for hauling soil. Slopes should be relatively
:lat to prevent sludge from flowing downhill. However, if sludge solids content is high and/or sufficient bulking
soil is used, the effect can be prevented and layering performed on mildly sloping terrain.
Diked Containment - Dikes are constructed on level ground around all four sides of a containment area.
Alternatively, the containment area may be placed at the toe of the hill so that the steep slope can be utilized as
ontainment on one or two sides. Dikes would then be constructed around the remaining sides. Access is provided
to the top of the dikes so that haul vehicles can dump sludge directly into the containment. A 1-3 ft interim cover
may be applied at certain points during the filling; a 3-5 ft final cover should be applied when filling is dis-
continued. Cover material is applied either by a dragline based on solid ground atop the dikes or by track dozers
directly on top of the sludge, depending upon sludge bearing capacity. Usually, operations are conducted without
the addition of soil bulking agents, but occasionally soil bulking is added. Typical dimensions: 50-100 ft wide,
100-200 ft long, 10-30 ft deep.
Modifications - Codisposal: sludge/refuse
Technology Status - Relatively new, not in widespread use.
Applications - Suitable when subsurface placement is impossible due to shallow groundwater or bedrock.
Area Fill Mound - Suitable for stabilized sludge; good land utilization; higher manpower and equipment
requirements due to the constant need to push and stack slumping mounds. Area Fill Layer - Suitable for stabi-
lized sludge; poor land utilization; less manpower and equipment requirements. Diked Containment - Efficient land
use; suitable for stabilized or unstabilized sludge; less soil requirement.
imitations - Rainfall causes mounds to slump. Operating difficulties in wet and freezing weather.
Typical Equipment/No. of Hfrs. - Front-end loader/7; bulldozer/19; scraper/25; backhoe/45; dragline/13; grader/25.
Chemicals Required - Lime and masking agents to control odors.
Residuals Generated - None
Design Criteria -
Sludge solids content
Sludge characteristics
Ground slopes
Bulking required
Bulking ratio soil: sludge
Sludge application rate
Equipment
Area Fill Mound
Greater than 20%.
Area Fill Layer
Greater than 15%.
Stabilized.
No limitation if
suitably prepared.
Yes.
0.5 to 2 soil:l sludge.
3000 to 14000 yd /acre.
Track loader, backhoe
with loader, track dozer.
Stabilized.
Level ground preferred.
Yes.
0.25 to 1 soil:l sludge.
2000 to 9000 yd /acre.
Track dozer, grader,
Diked Containment
20 to 28% for land-based
equipment; more than
28% for sludge-based
equipment.
Stabilized or unstabilized.
Level ground or steep terrain
if suitably prepared.
Occasionally.
0 to 0.5 soil:l sludge.
4800 to 15000 yd /acre.
Dragline, track dozer, scraper.
track loader.
Process Reliability - Very reliable sludge disposal method.
Environmental Impact - Potential soil erosion, dust, vectors, noise and odor problems. Leachate and gas continue
to be produced for many years after the fill is completed; leachate must be properly controlled to avoid ground-
water and surface water contamination; gas is explosive and can migrate to nearby structures, or can stunt or kill
vegetation if not properly controlled. Mud can be transferred to local roads by transport vehicles, can be allevi-
ated by a wash pad located near the exit gate. Area fill layer relatively land intensive.
References - 148, 168
A-160
-------
SLUDGE LANDFILLING - AREA FILL
FAC1 SHEET
FLOW DIAGRAM
GAS , LEACHATE TO TREATMENT
ENERGY NOTES (171) - Actual fuel consumption varies considerably with specific sludge, site and operating con-
ditions. Fuel consumption rates for some typical construction equipment performing light to medium work is given
1~ -. 1 A. .
Equipment
Caterpillar D-6
Caterpillar D-8
Excavator - !
Hi to IS
l»s to 2
Wheel Loader IS
2
3
4
5
7
yd,
^3
^3
Y^3
yd..
yd
Average Diesel
Fuel, gal/hr
5.2
10.8
3.4
5.0
8.8
11.1
3.0
3.7
4.6
6.2
9.0
13.2
Equipment
Grader - 25,000 Ob
28,000 Ib
30,000 Ib
40,000 Ib
54,000 Ib
Track Loader - 1 yd
2 yd
2.5 Xd
3
4
Tractor-Scraper,
yd
Y3
yd
small
medium
large
Average Diesel
Fuel, gal/hr
4.4
4.8
5.2
6.0
7.9
2.4
3.4
4.2
5.7
7.4
11.3
4.9
11.4
15.8
One case study that used a sludge landfill operation was estimated to consume 700,000 Btu/dry ton sludge (1 gal
diesel fuel = 140,000 Btu).
COSTS* (168) - Assumptions: First quarter 1978 dollars; ENR Index = 2681.
3.
Site and equipment costs include land ($2500/acre), site preparation (clearing, grubbing, surface water
control ditches and ponds, monitoring wells, soil stockpiles, roads and facilities), equipment purchase,
engineering (6%). Actual fill area consumes 50 percent of total site area.
Operating costs include labor ($8/hr, including fringe, overhead, administration), equipment fuel, main-
tenance and parts; utilities; laboratory analysis of water samples; supplies and materials.
Actual costs vary considerably with specific sludge and site conditions.
SITE AND EQUIPMENT COSTS
OPERATION s MAINTENANCE COSTS
20 30 40 50
200 300 400 500
20 30 40 50
200 300 400 500
Sludge Quantity Received
(Wet Tons/Day)
REFERENCES - 168, 171
*To convert construction cost to capital cost see Table A-2.
A-161
Sludge Quantity Received
(Wet Tons/Day)
-------
LIQUID SLUDGE TRANSPORT (PIPELINE)
FACT SHEET 6.1.5
Description (8, 22) - The movement of liquid sludge having a maximum total solids content of 5 percent, by centri-
fugal pumps through a pipeline of two miles, minimum length, from the point of origin, such as a wastewater treat-
ment plant, to a designated site selected for the particular sludge. Depending on the terrain and length of the
line, intermediate dry well pumping stations (factory packaged or field constructed) may be required to maintain
the flow to the site.
Common Modifications (3, 8, 72, 105) -
Carbon steel pipe unlined and cement lined.
Cast iron pipe, unlined, and cement and glass lined. Ductile iron pipe, unlined and cement lined.
Cement-asbestos.
Fiberglass-reinforced epoxy pipe. Plastic pipe.
Depending on the length and pressure drop of the line, intermediate lift stations are provided.
Depending on the sludge utilization procedure to be followed at the site, dewatering at the site may be necessary.
Technology Status - Highly developed and in relatively widespread use.
Limitations (26, 73) - Relatively high capital cost; long construction period; site must be available for a long
period of time; flushing or "pigging" of entire line may become necessary requiring shut-down of line.
Design Criteria (22, 105) - Sludges are thixotropic. The most economical sludge pumping occurs at the critical
velocity where turbulent flow begins, and where the mixing and agitation reduce the viscosity (and head loss).
Some critical velocities at 4 percent solids for various pipe diameters are:
Critical Velocity (ft/s)
Dia. Lower Upper Maintaining the operating velocity in the lower
8 3.58 4.52 portion of the turbulent flow zone results in
10 3.55 4.42 maximum economy. Critical velocity is a function
14 3.45 4.31 of solids content as well as pipe size.
20 3.40 4.23
Increasing the velocity is one method for causing turbulence, viscosity reduction, and self-cleaning. However
velocities much above the critical will involve an excessive head loss because of friction. Head losses attribu-
table to the sludge characteristics increase when: the solids concentration increases; size of the coarse sludge
particles increase; the volatile content increases; the temperature decreases; the velocities are too high or too
low. Effective grit removal is necessary for economical pumping. Grit increases viscosity and settles out during
periods of little or no flow causing a temporary increase in pipe roughness and head loss. Pumping anaerobically
digested sludge results in lower head loss as a result of friction than pumping raw primary sludge of the same
solids content (dry basis) and flow condition. Turbulent flow tends to prevent deposition of grease. Pipeline
materials and linings influence head losses as a result of differing friction flow factors. Mechanical and chemi-
cal aids such as macerators, in-line mixers, and polymers are sometimes used to reduce viscosity and head loss.
Operating controls usually are float control, density gauges, flow meters, pressure switches and pressure gauges.
The literature indicates that the hydraulic characteristics of wastewater sludges have not been well defined
because of their indefinite nature and that finite predictions of head losses are impossible to make. The
approach has been to provide an adequate safety factor when designing sludge pump and piping systems.
Brief characteristics of Pipeline and Pumping
Description
Pipe
Pipe
Pipe
Pipe
Pipe
Pipe
Pipe
Pipe
Pumping Station
Packaged
Pumping Station
Field Const.
Material
Cast or ductile iron,
unlined
Cast or ductile iron,
cement-lined
C.I. glass lined
Steel, unlined
Steel, cement-lined
Cement-asbestos
Fiberglass-reinforced
epoxy pipe
Plastic
Various
Various
Stations (105) -
Application
General use; high
pressures
General use; high
pressures
Not in general use.
General use; high
pressures
General use; high
pressures
General use; moderate
pressures
Not in general use;
moderate pressures
Not in general use;
lower pressures
In general use
In general use
Advantages
Less expensive than
most
No corrosion, slow
grease build-up
No corrosion, slow
grease build-up
Less expensive than
most
No corrosion, slow
grease build-up
No corrosion, slow
grease build-up
No corrosion, slow
grease build-up
No corrosion, slow
grease build-up
Less costly than
field constructed
High capacity, high
heads
Disadvantages
Undergoes corrosior
grease build-up
More expensive thar
unlined
Most expensive
Undergoes corrosior
More expensive thar
unlined steel
Relatively brittle
As expensive as
glass-lined pipe
Expensive
10,000 gal/min max.
200 ft head max.
Field constructed
more expensive
Reliability - Very reliable if properly installed.
Environmental Impact - None for air and water; considerable impact on land during installation. Potential for
ground water pollution if leak develops.
References - 3, 8, 22, 26, 72, 105
A-162
-------
LIQUID SLUDGE TRANSPORT (PIPELINE)
FACT SHEET 6.1.5
FLOW DIAGRAM -
Pump
Station
Pipeline
Booster
Pump
Station
(Optional)
Pipeline __
Disposal
Site
ENERGY NOTES - Each pipeline is highly site specific due to static head and the dynamic head requirements dictated
by the pipe material and size and the characteristics of the sludge being pumped. Approximate energy requirements
for a pipeline can be computed from the equation kWh/yr = 1900 (Mgal/d/yr X ft of total head) after actual con-
ditions have been determined, when assuming a wire to water efficiency of 60 percent for the pump station.
COSTS (3) - Assumptions: ENR Index = 2475
1. Construction cost includes: pipeline and pumping stations, one major highway crossing per mile, one single
rail crossing per 5 miles, nominal number of driveways and minor road crossings.
Pipeline is buried 3 to 6 ft. (add 15 percent for 6 to 10 ft.), no elevation change in pipeline.
3. Pipeline is cement-lined cast or ductile iron, 4 inch minimum pipe size.
4. Pumps are dry-pit, horizontal or vertical, non-clog centrifugal (1780 r/min).
Construction cost does not include: rock excavation or major unusual problems (add 70 percent to cost for
hard rock).
Operation cost includes: labor, supplies, and electrical power for pump stations; 12 hours pumping per day;
flow velocity of 4 ft/s.
CONSTRUCTION COST
OPERATION & MAINTENANCE COST
10
0 1
20 miles
10 miles
5 miles
001
10
REFERENCE - 3
100 1000 10000
Sludge Pumping Rale, gal/mm
10
100 1000
Sludge Pumping Rate, gal/mm
10000
*To convert construction cost to capital cost see Table A-2.
A-163
-------
LIQUID SLUDGE TRANSPORT (RAIL) FACT SHEET 6.1.6
Description - Liquid sludge having a maximum total solids content of six percent may be transported by railroad
tank cars from point of Origin, such as a wastewater treatment plant or pipeline terminus, to a designated site.
The site may be adjacent to the railroad or joined by pipeline to the unloading site. The cars used may be owned
or rented by the operator depending upon the economics of the location.
By virtue of its existing right-of-way, the railroad in many instances can provide the opportunity for use of
selected land for sludge disposal. Transport to the site from the railroad terminus may be a major element in the
development of an integrated disposal system. Other important considerations include the methods and equipment to
be used for unloading, storage, and distributing the sludge at the site.
Technology Status - Not in widespread use even though railroad technology is highly developed.
Limitations - Fixed position of railroad limits site selection. Relative transportation costs ($/ton dry solids
basis) indicate that railroad tank cars are the most expensive method of transporting sludge for distances up to
approximately 150 miles when compared to a tank truck and up to approximately 200 miles when compared to a pipe-
line. For greater distances, rail tank car transportation is least expensive. May not be applicable for small
operation.
Design Criteria - Rail line should be near or next to the site to reduce length of spur, siding, or pipeline.
Sludge storage at wastewater treatment plant should equal one day's production.
Cars should be 20,000 gallon capacity, and pumping station filling rate should be 1.5, 2, 3, and 15 hours, respect'
ively, for 1, 10, 20, and 100 car groups.
Cars should be gravity unloaded at the terminus for pumping to storage and/or disposal.
Typical Equipment/ No. of Mfrs. (23) - Sludge handling and control/32; cars, dump/14.
Reliability - With respect to scheduled deliveries to the site: very reliable for unit train; not reliable for
single or few cars, since railroads would tend to preferentially select equipment for use in heavy tonnage hauls
of other commodities.
Environmental Impact - None for air and water unless leak in car.
References - 3, 7, 8, 23, 72, 83, 101, 104, 142
A-164
-------
LIQUID SLUDGE TRANSPORT (RAIL)
FACT SHEET 6.1.6
FLOW DIAGRAM -
Treatment Plant
Site
ENERGY NOTES (161) - Rail transport can be considered to require approximately 25 percent of the energy in Btu/ton
mile when compared to truck transport. See Fact Sheet 6.1.7 for truck energy requirements for large vehicles.
Pumping energy for loading is insignificant compared to the transport energy.
COSTS - Construction cost includes loading facilities: storage for one day's production; pump and piping system
sized to fill 1, 10, 20 and 100 tank cars each with 20,000 gal capacity to be filled in 1.5, 2, 3, and 15 h,
respectively. Solids content at 4 percent. Construction cost does not include storage at unloading area.
Operation cost includes 8 h/d operation; car lease, labor, electrical energy, supplies maintenance (Full car
maintenance annual lease rate is assumed at $525/car); travel distances of 40, 80 and 160 miles one way; rail haul
charges based on the following:
Area
North Central and Central
Northeast
Southeast
Southwest
West Coast
Approximate R.R. Rate Variation (adjust Accordingly)
Average Rate - Approximately $0.06/ton mile
25 percent higher than average
25 percent lower than average
10 percent lower than average
10 percent higher than average
ENR Index = 2475.
10
CONSTRUCTION COST
1 0
0 1
001
100
OPERATION & MAINTENANCE COST
10
15 1 0
1 0
10 100
Annual Sludge Volume. Mgal
1000
0 1
160 Mile
80 Mile
<-• -40 Mile
10 100
Annual Sludge Volume. Mgal
1000
REFERENCES - 3, 161, 142
'To convert construction cost to capital cost see Table A-2.
A-165
-------
LIQUID SLUDGE TRANSPORT (TRUCK) FACT SHEET 6.1.7
lescription - The movement over highways and roads by tank trucks, of liquid sludge having a maximum total solids
:ontent of 6 percent, from its point of origin, such as a wastewater treatment plant, to a distant designated
lite selected for the particular sludge. The site is next to a road or highway.
Common Modifications (96) -
spending upon state road laws, the type of vehicle would vary between the following:
.Two axle and three axle tank trucks.
.Two axle tractor with one axle semi-tank trailer.
.Two axle tractor with two axle semi-tank trailer.
.Three axle tractor with two axle semi-tank trailer.
.Two or three axle tank truck with a two or three axle tank trailer.
Gasoline or diesel engine power. Diesel engine power preferred because of cheaper fuel and lower maintenance
costs.
'echnology Status - Highly developed and in widespread use.
.imitations (7, 8, 21, 73, 96) -
tate road laws which limit load of vehicle. In Ohio, for example, the maximum payloads would be:
Vehicle Payload, Gal (Tons)
2 axle tank truck (Note a.) 1200 ( 5)
3 axle tank truck (Note b.) 2500 (10)
5 axle tractor semi-trailer tank (Note c.) 5800 (24)
Note a. Most commonly used vehicle for hauling and, if the site surface is suitable, for spreading as
well. Normally, special off-road tank vehicles are used for spreading.
Note b. Some wastewater treatment plants use vehicles of this type, with only a fraction of the legal
loads, to provide better flotation over soft ground.
Note c. Montgomery County, Ohio uses this vehicle with about a 5000 gal (21 ton) capacity to haul and
spread.
Generally, highway and road loadings are in accordance with American Association of State Highway Officials Class
Standards H10, H15, H20, HS15, and HS20.
'ransportation of sludge by pipeline is generally more economical and more convenient than tank truck handling,
although it does have higher capital costs and is inflexible. Relative transportation costs (S/ton dry solids
iasis) indicate that tank trucks are the most expensive method for transporting sludge for distances of approx-
imately 150 miles and over when compared to pipeline and railroad tank car. For less than 150 miles it is less
expensive than railroad tank car, assuming that both require unloading at the disposal site.
Truck transport generally has a lower initial investment cost but will have higher operating costs relative to
rail or pipeline transport for most levels of design volume. Trucks are very flexible.
Design Criteria (3) -
Liquid sludge should have a maximum solids content of 6 percent.
Vehicle should be loaded by gravity from a storage tank and gravity unloaded at the site.
Loading equipment should be sized to fill vehicle in 20 minutes maximum.
Typical Equipment/No, of Mfrs.- See Society of Automotive Engineers (SAE) roster of truck and trailer manufac-
turers.
Reliability - Very reliable.
Environmental Impact - None for air and water unless a leak develops in the tank. Small for land if temporary
roads are built from highway to unloading area within disposal site. Noise and general disruption due to truck
traffic may constitute a nuisance.
Comments (8) - Highway vehicles offer some flexibility of movement to various sites when compared to rail.
Transport to the site should be one element of an integrated design for the production and ultimate disposal of
the sludge. Other important elements of this design are the methods and equipment to be used for unloading,
storage, and distributing the sludge at the site.
References - 3, 7, 8, 21, 73, 96
A-166
-------
LIQUID SLUDGE TRANSPORT (TRUCK)
FACT SHEET 6.1.7
FLOW DIAGRAM -
Site
ENERGY NOTES (142) - Approximate average annualgBtu used per Mgal sludge per one-way tripmile for 1,200, 2,500,
and 5,500 gal trucks are, respectively, 51 x 10 ; 22 x 10 ; 14 x 10 Btu. Electrical energy required for pumping
is insignificant with respect to transportation energy needs.
*
COSTS - Assumptions: ENR Index = 2475
1. Construction cost includes load/unload facilities and purchase of the most cost effective size trucks per
volume of sludge transported; i.e., 1200 gal, 2500 gal, and 5500 gal. Does not include storage at unloading
site.
2. Equipment is sized to fill truck in 20 rain, maximum.
3. Sludge = 4 percent solids.
4. Operation and maintenance costs include truck maintenance and operation and supplies for the loading
facility.
5. Fuel cost (Gasoline) = $0.60/gal; electrical power @ $.02/kWh.
6. Labor @ $7.50/h.
7. Most cost effective size trucks per volume of sludge transported; i.e., 1200 gal, 2500 gal, 5500 gal.
8. 8 h/d operation; 360 d/yr.
9. Travel distances of 10, 20, or 40 miles one way to disposal site.
10
CONSTRUCTION COST
1 0
Q
~O
£
O
s
0 1
001
40 Miles ;
20 Miles
7*
'?
• 10 Miles
10
OPERATION & MAINTENANCE COST
1 0
1 0
REFERENCES - 3, 142
10 100 1000
Sludge Volume, Mgal/yr
001
40 Miles :;_
20 Miles.
z
10
1 0
10 100 1000
Sludge Volume, Mgal/yr
*To convert construction cost to capital cost see Table A-2.
A-167
-------
SLUDGE PUMPING
FACT SHEET 6.1,8
Description (22) - Sludges, scum, screenings, and sludge cakes have different viscosities and solids content at
different locations. Pumps are employed to move these materials where gravity flow is not possible or where the
receiving location requires a specific flow and pressure of the pumped fluid. Capacities up to 80,000 gal/min and
210 ft head with fluids having up to 20 percent solids content are required.
Common Modifications (22) - Electric motor or internal combustion engine power. Variable speed belt, chain, and
fluid drives. Materials of pump internal parts construction vary according to the properties of the fluids pumped.
Technology Status - Highly developed.
Applications (22, 52) - Stormwater treatment facilities where gravity return of residuals to the dry weather sewer
is not possible. Wastewater treatment plants to convey residuals from process to process. Wastewater treatment
plants to convey sludge from plant to disposal site by pipeline.
Typical Equipment/No, of Mfrs. (23) - Pump units/34.
Design Criteria (7, 22, 52) - Sludge pumping equipment is selected on the basis of sludge concentration and the
operation intended:
Max.Solids Max.Suction Capacity Max.Head Typ.Eff.
Pump Type
Centrifugal,
2 port,
non-clog
Centrifugal,
vortex flow
Mixed flow
Air lift
Screw lift
Positive Displ.
progressing cavity,
plunger, and
diaphragm
Handled, %
2
6
6
20
Lift, ft
15
15
15
NA
0
28
gal/min
50-20,000
20-5,000
1000-80,000
30-150
100-70,000
30-700
ft
200
210
60
60
40
500+
60-85
55-65
80-88
low
70-80
30-80
Typical Applications
Raw wastewater, primary and
secondary settled sludges, land
application, chem. treated sludge,
incinerator slurries.
Sludge recirculation, effluents with
stringy material.
Sludge recirculation, land appli-
cation.
Raw wastewater, return sludge, scum.
Raw wastewater, return sludge.
Primary settled, thickened, digested,
incinerated, heat conditioned, and
chemically treated sludges, scum.
Viscosity limit for efficiently operated centrifugal type pumps is 3000 to 3500 sSu
Non-clog, low r/min, low head centrifugal pumps are used for pumping return activated sludge because the sludge is
dilute, contains only fine solids, and the sludge's flocculent solids would not be significantly sheared by the
pump.
Plunger and progressing-cavity pumps are best for concentrated sludges to overcome high friction-head losses in
discharge lines. However solids should be reduced to small aize (max. 1.5" for progressing cavity).
Screw lift pumps are good for variable capacity operation because the rate of discharge is controlled by the fluid
level at the inlet to the screw. Variable speed drive not required.
In general, the centrifugal and screw lift pumps are used to handle larger sludge flows with lower solids content
and where precise control of flow is not required.
Air lift pumps, though of simple design and construction and not susceptible to clogging, are difficult to throttle
and control and require large amounts of air.
Flow conditions can be improved by adding certain types of polymers to reduce viscosity of the fluid.
Reliability - Ten to 20 year expectancy provided manufacturer's maintenance procedures are followed. Reliability
highly dependent on power source.
Environmental Impact - Low impact on air and water. Small impact on land for pumps which are in process lines.
Potential for pollution under failure conditions.
References - 7, 22, 52
A-168
-------
SLUDGE PUMPING
FACT SHEET 6.1.3
FLOW DIAGRAM - Possible locations for major sludge pumps in a wastewater treatment plant:
Bar Screen
or Disposal
Pump
ENERGY NOTES - Each pump application is highly site specific due to static head and the dynamic head requirements
dictated by the piping configuration and the characteristics of the sludge being pumped. Approximate energy
requirements for a pump installation can be computed by the following equation:
1140 (Mgal/d X ft of total head)
kWh/yr « Wire to Water Pump Efficiency
Wire to water efficiencies may vary from 75 percent to less than 40 percent, depending upon the type pump used and
its size. Use of variable speed drives at speeds other than 100 percent speed generally lowers the wire to water
efficiency.
COSTS - ENR INDEX = 2475 *
1. Costs are based on a sludge loading of 1900 Ib/Mgal at 4% solids, i.e., 5700 gal of sludge/Mgal for combined
primary and secondary sludge after thickening.
2. Non-clog centrifugal pumps. Service life: 10 years.
3. To adjust costs for alternative sludge quantities and characteristics, enter curves at effective flow (Q£)=
Q = QnFt;TrN X NEW DESIGN SLUDGE MASS. LB/MGAL X 4%
1,900 Ib/Mgal NEW DESIGN CONCENTRATION (%)
Note: New Design concentration should not exceed 5%.
4. Power at 2C/kWh.
CONSTRUCTION COST
OPERATION & MAINTENANCE COST
2
^
i
B
tn
c
O
5 0 01
0001
0 1
001
Q 5
o £
•s -f 0001
31
01
1 0 10
Wastewater Flow Mgal/d
100
00001
Matenals-
Tola ,
001
0001
00001
000001
01
1 0 10
Wastewater Flow, Mgal/d
100
REFERENCES - 3, 22
*To convert construction cost to capital cost see Table A-2.
A-169
-------
iLUDGE STORAGE FACT SHEET 6.1,9
Ascription (7,8) - For the purposes of this fact sheet, sludge storage is the retention and blending of thickened
trimary and secondary sludges in an open tank. The purposes of sludge storage are to reduce the pathogen popu-
ation by aeration and mixing, to further stabilize the sludge, to equalize short-term peak loads, and to either
repare the sludge for further processing or provide the means for loading the sludge into a disposal system. (The
letention afforded by sludge storage can be used to further thicken the sludge.)
Common Modifications (22) - Rectangular or cylindrical tanks can be used, and agitators can be used for mixing.
Sludge can also be mixed by the use of recycle. Air or pure oxygen can be used for aeration and mixing.
Sludge storage can also be used for chemical, tertiary, as well as other sludges. Sludge scraper mechanisms with
icket arms would then be required.
'echnology Status - In widespread use.
Typical Equipment/No, of Mfrs. (23) -
,gitators/10; air compressors/8; blowers/7; mixers/26.
ipplications - Can be applicable where separate thickening processes for primary and activated sludges are used.
It is also used between multiple sludge treatment processes so that each unit can b« batch operated.
Limitations - Potential for odor problems.
Chemicals Required - None.
Residuals Generated - None.
Design Criteria (8,22) - Tank floor slope is generally 1:12. This increased depth near the center of the tank can
serve to compact the sludge. Sludge concentration increases as a function of the depth of the sludge blanket.
Effluent line should draw compressed solids out of the bottom of the tank. Mixing by air diffusion requires at
least 25 ft /min/1000 ft . Mixing by agitators (mixers) requires approximately 1.0 hp/1000 ft .
'rocess and Mechanical Reliability - High degree of reliability provided regular maintenance procedures for the air
and mixing equipment are followed.
Environmental Impact - Can create odor problems if breakdown of air system occurs. Land: Moderate—depends on
size of tank. No residuals are generated.
References - 7, 8, 22, 23
A-170
-------
SLUDGE STORAGE
FACT SHEET 6.1.9
I'LOW DIAGRAM
Decant Line-*-.
Sludge Inlet->
I ^Sludge Ou
tlet
.Blower
Air Sparger
Drain Line
Sludge Storage Tank
ENERGY NOTES -
Based upon the "Cost" assumptions shown below, kWh/yr = 4242 x million gallons per day of plant throughput
assuming that all conventional activated sludge plant sludges pass through the storage tank.
COSTS -Assumptions: ENR Index = 2475
1. Construction cost includes storage tank and air-supply system.
2. Operation cost includes storage of thickened primary and secondary sludge (1900 Ib/Mgal; at 4% solids);
mixing by diffused air (25 CFM/1000 ft3 or approximately 130 hp/Mgal of sludge.
3. To adjust costs for other sludge quantities and concentrations, enter the curves at effective flow (QE).
10
1 0
o
0
"6
c
o
J 01
001
REFERENCES
CONSTRUCTION COST
—^
,*-
»*• '
— '
1
- 3, 4, 22
^*
^
-^
^^ ,
_,
S
1900 Ib/Mgal
s
S
_ ^
(0
"o
: B ro
» ' W CD
: §1
5 5
„ a
o-J
°i
ro o
<
10 10 100
Wastewater Flow Mgal/d
New Design Sludge Concentrations
OPERATION & MAINTENANCE COST
01
tf)
0^ 001
tn cp
II
2 5
„ a
ay ro
o-J
75 00,001
i1-
<
0.0001
0
/
s
-*1
/
s*
s
«••
/
^
* .
'
r
s
s
? ^ ~
^
7
1
• >'
/
.-
4
s
p
'
T
1 —
s
/
owe
h*1
^,
ote
'
\Kz
1 ,'
/
-f
lera
1 0
S
•' ,'^
-------
SLUDGE LANDFILLING - SLUDGE TRENCHING FACT SHEET 6,1.10
Description - Stabilized or unstabilized sludge is placed within a subsurface excavation and covered with soil.
Trench operations are more specifically categorized as follows: narrow trench and wide trench. Narrow trenches are
defined as having widths less than 10 ft; wide trenches are defined as having widths greater than 10 ft. The width
of the trench is determined by the solids content of the receiving sludge and its capability of supporting cover
material and equipment. Distances between trenches should be large enough to provide sidewall stability, as well
as space for soil stockpiles, operating equipment and haul vehicles. Design considerations should include pro-
visions to control leachate and gas migration, dust, vectors, and/or aesthetics. Leachate control measures include
the maintenance of 2 to 5 ft of soil thickness between trench bottom and highest groundwater level or bedrock (2 ft
for clay to 5 ft for sand), or membrane liners and leachate collection and treatment system. Installation of gas
control facilities may be necessary if inhabited structures are nearby.
Narrow trench - Sludge is disposed in a single application and a single layer of cover soil is applied atop this
sludge. Trenches are usually excavated by equipment based on solid ground adjacent to the trench, and equipment
does not enter the excavation. Backhoes, excavators and trenching machines are particularly useful. Excavated
material is usually immediately applied as cover over an adjacent sludge-filled trench. Sludge is placed in
trenches either directly from haul vehicles, through a chute extension, or by pumping. The main advantage of a 2
to 3 ft narrow trench is its ability to handle sludge with a relatively low solids content (15 to 20 percent).
Instead of sinking to the bottom of the sludge, the cover soil bridges over the trench and receives support from
undisturbed soils along each side of the trench. A 3 to 10 ft width is more appropriate for sludge with solids
content of 20 to 28 percent, which is high enough to support cover soil.
Wide trench - Usually excavated by equipment operating inside the trench. Track loaders, draglines, scrapers and
track dozers are suitable. Excavated material is stockpiled on solid ground adjacent to the trench for subsequent
application as cover material. If sludge is incapable of supporting equipment, cover is applied by equipment
based on solid undisturbed ground adjacent to the trench. A front-end loader is suitable for trenches up to
10 ft wide; a dragline is suitable for trench widths up to 50 ft. If sludge can support equipment, a track dozer
applies cover from within the trench. Sludge is placed in trenches by one of the following methods: from haul
vehicles directly entering the trench and haul vehicles dumping from the top of the trench. Dikes can be used to
confine sludge to a specific area in a continuous trench.
After maximum settlement has occurred in approximately one year, the area should be regraded to ensure proper
drainage.
Common Modifications - Codisposal: Sludge/refuse
Technology Status - Fully demonstrated.
Applications - A relatively simple sludge disposal method suitable for stabilized or unstabilized sludge. Does
not require special expertise beyond the skills necessary to operate the above-mentioned equipment, plus adminis-
trative skills. Narrow trench system particularly well suited for smaller communities.
Limitations - Frozen soil conditions and precipitation cause operating difficulties.
Typical Equipment/Ho, of Mfrs. (83) - Front-end loader/7; bulldozer/19; scraper/25; backhoe/45; dragline/13;
trencher/4; grader/25.
Chemicals Required - Lime and masking agents to control odors.
Residuals Generated - None
Design Criteria -
Narrow Trench (less than 10 ft) Wide Trench (more than 10 ft)
Sludge Solids Content 15 to 20 percent for 2 to 3 ft 20 to 28 percent for land-based equipment;
widths; 20 to 28 percent for more than 28 percent for sludge based
3 to 10 ft widths. equipment.
Ground Slopes Less than 20 percent. Less than 10 percent.
Cover Soil Thickness 2 to 3 ft for 2 to 3 ft widths; 3 to 4 ft for land based equipment; 4 to
3 to 4 ft for 3 to 10 ft widths. 5 ft for sludge based equipment.
Sludge Application Rate 1,200 to 5,600 yd /acre. 3,200 to 14,500 yd /acre.
Equipment Backhoe with loader, excavator. Track loader, dragline, scraper, track
trenching machine. dozer.
Process Reliability - Very reliable sludge disposal method.
Environmental Impact - Potential soil erosion and odor problems. Leachate and gas continue to be produced for
many years after the fill is completed; leachate must be properly controlled to avoid groundwater and surface
water contamination; gas is explosive or can stunt or kill vegetation if not properly controlled. The narrow
trench method is relatively more land intensive.
References - 148, 168
A-172
-------
SLUDGE LANDFILLING - SLUDGE TRENCHING
FLOW DIAGRAM
FACT SHEET 6.1.10
GAS AND LEACHATE MAY BE
COLLECTED AND TREATED
ENERGY NOTL'S (171) - Actual iuol coiuiuiiipuiun varies considerably with specific sludge, site and operating con-
ditions. Fuel consumption rates for some typical construction equipment performing light to medium work is given
below.
Average Diesel Average Diesel
Equipment Fuel , gal/hr Equipment Fuel , gal/hr
Caterpillar D-6 5.2 Grader - 25,000 Ib 4.4
Caterpillar D-8 10.8 28,000 Ib 4.8
Excavator - >s yd 3.4 30,000 Ib 5.2
1 yd 5.0 40,000 Ib 6.0
1-1/4 to 1-1/2 yd 8.8 54,000 Ib 7.9
1-1/2 to 2 yd 11.1 Track Loader - 1 yd 2.4
Wheel Loader 1-1/2 yd 3.0 1-1/2 yd 3.4
2 yd 3.7 2 yd 4.2
3 yd 4.6 2.5 yd 5.7
4 yd 6.2 3 yd 7.4
5 yd3 9.0 4 yd 11.3
7 yd 13.2 Tractor-Scraper, small 4.9
medium 11.4
large 15.8
*
COSTS, 1978 dollars (168) - ENR Index = ?77fi
1. Site and equipment costs include land ($2500/acre) , site preparati
control ditches and ponds, monitoring wells, soil stockpiles, roac
engineering (6%). Actual fill area consumes 50 percent of total E
2. Operating costs include labor ($8/hr, including fringe, overhead,
and parts; utilities; laboratory analysis of water samples; suppl:
3. Actual costs varv considerably with specific sludge and site condi
SITE s EQLIFKENT CCSTS
50.00 | 50.00 •
40.00 T 40.00
30.00 •' 30.00
o 20.00 -f co 20.00
r~ f-
" 15.00 i " 15.00 •
a S
~ 10.30 ~ 10.00
1 , J>
j 4.00 T ^^^~~^-^^^^ w 4.00
° 3.30 N^ " . 3 3.00
wide Trer.cn
2.00 * 2.00
1 - on 1111 1 i i i i ' ""
10 20 30 40 50 100 200 300 400 500 j
(Wee Tons/Day)
REFERENCES - 168, 171
*To convert construction cost to capital cost see Table A-2.
on (clearing, grubbing, surface water
s and facilities), equipment purchase,
ite area.
administration), equipment fuel, maintenance
es and materials.
tions.
OPERATION & MAINTENANCE COSTS
\~" ~^^ ^.Narrow Trench
'Wide Trench ^
0 20 30 40 50 100 200 300 400 500
Sludge Quantity Received
(Wet Tons/Day)
A-173
-------
SLUDGE LAGOONS FACT SHEET 6,1,11
Process Description (8, 56) - Digested sludge has often been applied to sludge lagoons adjacent to or in the proxi-
mity of treatment facilities. These sludge lagoons are primarily designed to accomplish long-term drying of the
digested sludge through the physical processes of percolation and evaporation, primarily the latter. This method
of sludge processing has been extremely popular in the U.S. due to its relatively low cost (when inexpensive land
is plentiful) and minimal O&M requirements, especially at smaller wastewater treatment facilities. The process i:
relatively simple, requiring periodic decanting of supernatant back to the head of the plant and occasional mechan-
ical excavation of dewatered or dried sludge for transportation to its ultimate disposal location. Lagoons can be
a very useful process step. Supernatant is far better (low SS) than supernatant from a secondary digester or even
a thickener. Ultimate disposal of the product solids often is as a soil conditioner or for landfilling.
Sludge lagoons may also be used as contingency units at treatment plants to store and/or process sludges when
normal processing units are either overloaded or out of service.
The drying time to 30 percent solids is generally quite lengthy and may require years. Climatic conditions and
pre-lagoon sludge processing greatly influence lagoon performance. In warmer, drier climates well-digested sludges
are economically and satisfactorily treated by sludge-drying lagoons because of their inherent simplicity of
operation and flexibility. Complete freezing causes sludge to agglomerate so when it thaws supernatant decants or
drains away easily. Well-digested sludges minimize potential odor problems which are inherent in this type of
system. Multiple-cells are required for efficient operation.
Common Modifications (56) - Methods and patterns of loading, supernatant recycling techniques and mechanical
cleaning techniques vary with location, climate, and type of sludge to be processed.
Technology Status - This technology is widely used for industrial and municipal sludge processing throughout the
world.
Limitations - There is a high potential for odors and nuisance insect breeding if feed sludges are not well-di-
gested. Odor and nuisance control chemicals are not entirely satisfactory. Also, definitive data on performance
and design parameters are lacking despite the popularity of this approach.
Typical Equipment/No. Mfrs (23) - Front-end loaders/7,- bulldozers/19; dragline/13.
Applications - A simple sludge drying method for digested sludge in smaller communities by virtue of the fact that
large inexpensive land areas are required.
Chemicals Required - Lime or other odor control chemicals may be required if digestion is incomplete.
Residuals Generated - Generally, the residuals resulting from a well-operated lagoon will be in the range of 30
percent solids and are suitable for use as a soil conditioner or for landfilling.
Design Criteria (8, 56) -
Dikes: Slopes of 1:2 exterior and 1:3 interior to permit maintenance and mowing and to prevent eros-
ion; width sufficient to allow vehicle transport during cleaning.
Depth: 1.5 to 4.0 feet of sludge depth (depending upon climate)
Bottom: Separation from groundwater is dependent upon application depths and soil characteristics, but
should not be less than 4 feet to prevent groundwater contamination.
Cells: A minimum of two cells is required. 2
Loading Rates: 2.2 to 2.4 Ib sglids/yr/ft of capacity. 1.7 to 3.3 Ib solids/ft of surface/30 days of bed
use. 1 to 4 ft /capita (depending on climate).
Decant: Single or multiple level decant forAperiodic returning supernatant to head of plant.
Sludge Removal: Approximately 1.5 to 3 yr intervals.
Process Reliability - Where properly designed, process reliability is function of reliability of upstream proc-
essing (digestion).
Environmental Impact - Odor and vector potential high unless properly designed and operated; land-use requirement
high,- groundwater pollution potential high unless proper site characterization incorporated into design.
References - 8, 56, 83
A-174
-------
SLUDGE LAGOONS
FACT SHEET 6,1.11
FLOW DIAGRAM -
•Supernatant to Wet Well
ENERGY NOTES - No external energy required other than possible sludge pumping from digester
Sheet 6.1.8) and supernatant pumping (see Fact Sheet 3.1.13).
COSTS -
(see Fact
1. Costs = 2nd quarter, 1977 dollars-ENR Index = 2515
2. Construction costs includes process piping, equipment, concrete, steel and excavation.
3. Sizing = 4 acres/Mgal/d, 1.5 ft depth of sludge
4. Operation and maintenance includes materials, supplies, maintenance, operation and residuals removal.
5. Labor = $7.50/h
CONSTRUCTION COSTS
OPERATION AND MAINTENANCE
10
1 0
0 1
0 01
1 0
o
o
10 100
LAGOON AREA, ACRES
1,000
0001
100 1,000 10,000
DRIED SOLIDS APPLIED, TONS/YR
100,000
REFERENCES - 5, 56, 201
*To convert construction cost to capital cost see Table A-2.
A-175
-------
CO-INCINERATION OF SLUDGE - SLUDGE INCINERATOR FACT SHEET 6.2.1
Description - Co-incineration is incineration using a combination of wastewater sludge and a combustible material,
other than natural gas or fuel oil, in a single furnace. By combining sludge with other materials, a combined
furnace feed can be formed which has both a low water content and a heating value high enough to eliminate the
need for supplemental furnace fuel. Some (of the combustible) materials are: municipal solid waste, coal, wood
wastes, textile wastes, bagasse, and farm wastes, such as corn stalks, rice husks, etc.
Co-incineration was first demonstrated in this country in Franklin, Ohio, utilizing a fluidized bed furnace. The
fuel consisted of the rejected organic waste stream from the solid waste fiber recovery operation and wastewater
sludge. Organic residue from the fiber recovery system, a 20 percent solids slurry, is mixed with 5 percent
solids sludge, dewatered to 45 percent solids in a. cone press, and combusted in the fluidized bed incinerator.
The incinerator requires about 3000 Btu per pound of as-received material to sustain combustion and as the combi-
nation of solid waste and sludge contain about 3600 Btu per pound, autogenous conditions are maintained. However,
with only 600 Btu per pound available as excess energy, the potential for energy recovery is low.
Co-incineration using a multiple hearth sludge incinerator has been tested both in the United States and in
Europe. Early testing in Europe using raw solid waste proved less than successful. However, converting the
organic portion of solid waste into a fluff to fuel the multiple hearth proved technically viable. This technique
was demonstrated at a wastewater treatment plant in Concord (central Contra Costa County), California, in an EPA-
supported demonstration. In the demonstration, an existing multiple hearth sludge incinerator (16 ft dia., 6
hearth) was modified to accept refuse-derived fuel (RDF) as a fuel. (The RDF mixed with the sludge having a
solids content of 16 percent was introduced into the top hearth, or fed directly into the third hearth. The latter
method proved more efficient. Approximately 70 to 100 percent excess air was used. The system was operated eight
hours per day for two months with a combined wet feed rate of up to 10 ton/hr. Autogenous combustion could be
maintained with an RDF/sludge ratio of 1:2 using a sludge solids content of 16 percent. The unit operated either
in the incineration mode (all excess air added to furnace proper) or the starved air combustion mode (oxygen
deficient in the furnace, excess air added at afterburner). The latter mode was preferred.
In a bench-scale study recently completed, the addition of pulverized coal to liquid sludge showed that the coal
improves filtration efficiency slightly and results in a higher solids content in the filter cake than if the coal
is added directly to the sludge cake. Addition of the coal to the liquid sludge prior to filtration results in a
furnace feed which has a higher solids content and heat value than pure sludge. This reduces or eliminates the
supplemental fuel demand. This approach solves the problem of solids content versus fuel value in one step.
Coal, of course, is not a waste material of little value. However, it substitutes a fossil fuel of great abun-
dance for scarce fuel oil and gas.
Technology Status - Technical feasibility of co-incineration in sludge incinerators with solid waste has been
demonstrated; however, there were only three municipal plants in operation in United States as of December, 1976
(91).
Applications - To provide a new low cost fuel source for existing sludge disposal facilities; derivation of
wastewater treatment plant power from a new energy source; use of same device to dispose of two waste products
thereby realizing capital and operating cost benefits, as well as reduced land requirement for disposal.
Limitations - Shredders are required to produce a nominal 1 inch refuse size. More excess air is required with
co-incineration versus separate sludge incineration. In addition, institutional constraints may have to be
resolved such as: existing long term refuse disposal contracts, jurisdictional disputes between currently separate
wastewater treatment and solid waste disposal government agencies.
Typical Equipment/No, of Mfrs. (10, 25, 77) -
Multiple Hearth Furnace System - Multiple Hearth Furnaces/10, Sludge Dewatering Devices/15, Flapgate Valves/6,
Cooling and Combustion Air Fans/42, Sludge Conveyors/7, Gas Scrubbers/3, Ash Handling System/1, Fluid Bed
Furnace System - Screw Feeders (Sludge)/7, Combustion Air Fans/42, Recuperative Air Heaters/29, Exhaust Gas
Scrubbers/3, Ash Handling System/1, Combustible Material Preparation and Feed Systems.
Environmental Impact - The impact is a strong function of feed material and sludge composition. The probable
uncontrolled particulate emissions from a co-incineration MHF furnace are about 10 percent greater than those from
sludge incineration alone. Available data indicate that toxic organics can be destroyed during incineration and
that the bulk of metals, except Hg, can be removed by particulate collectors (91). Hg emissions appear to be
acceptable but must be compared to allowable ambient concentrations at time of design.
References - 8, 25, 43, 65, 10, 77, 91
A-176
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CO-INCINERATION OF SLUDGE - SLUDGE INCINERATOR
FACT SHEET 6.2.1
FLOW DIAGRAM -
Gas Exhaust
To Atmosphere
Multiple Hearth Furnace
iiuid Bed Furnace
Feed System
Water In
Feed
System
Blender & 1
Flapgate
Valve
Waste
._ Combustion
*TjAir Fan
Pooling Air
Fan
Feed System
Sludge
Feed System
Waste
RDF
L-H
Blender
Furnace
Exhaus t
FBF
1
<
>
i.
_^ Recuper
t'
1A
»•
f
Exhaust Gas t(
Atmosphere
Ash Out
Air Scrubber
Co-incineration in Fluid Bed Furnace (FBF)
Ce-incineration in Multiple Hearth Furnace (MHF)
ENERGY NOTES (91) - Using the power and fuel cost/ton cited below, the electrical energy usage is 100 kwh/ton, and
the auxiliary fuel requirement is approximately 59,000 Btu/ton.
COSTS (91) - Co-incineration/Multiple Hearth Furnace (Capacity 600 ton/d refuse; 224 ton/d sludge at 20 percent
solids)- Costs, Mid 1975. Assumptions for the cost estimate: Capital costs include equipment, labor and ma-
terials for installation, construction overhead and contingency (15 percent of equipment modules only). Manpower
includes four shifts/d, seven d/wk operation with supervision and maintenance. Salary/overhead ranges from
$10,000 to S20,000/yr ($17,000 for operators and senior maintenance people). Twenty percent is added to total
manpower cost for overtime, vacations, holidays, etc. Power costs = $.027/kWh. Fuels costs = $2.73/(10 ) Btu.
Water and sewer costs = $0.37/1,000 gal. Residue disposal cost = $4.00/ton.ENR Index = 2205
CAPITAL COST
Item Cost
Shredder:
Two Primary Shredders $ 562,000
Two Screen & Mag. Separators 746,000
Two Secondary Shredders 628,000
Conveyors 930,000
Subtotal $ 2,866,000
Pneumatic Conveying System 366,000
Storage Silo (166,000 ft ) 1,541,000
Four Feed Conveyors (Storage to Furnace) 648,000
Four Multiple-Hearth Furnaces 13,800,000
(22 ft diameter X 11 ft hearth)
Building 4,314,000
Direct Construction Cost (DCC) $23,535,000
Design, Construction Management, 3,530,000
Start-Up (15% DCC)
Land ($50,000/acre) 350,000
Legal Fees (3% DCC) 706,000
Bond Discount (3% Total Cost) 844,000
Total Facility Cost $28,965,000
Facility Cost Per ton/d 5 35,200
(Design Cap.)
REFERENCE - 91
OPERATING COST
Item
Manpower
(45 employees)
Power
(2885 kWh/h)
Water/Sewer
(1310 gal/min)
Auxiliary Fuel
(85,300 gal/yr)
Maintenance
Cost per Ton* Total Ann. Cost
$ 3.40
2.72
1.02
0.16
3.20
(2.5% Incinerator DCC)
(5% Shredder DCC)
Overhead 1•14
(1% DCC)
Residue 0-94
(161 ton/d)
Total Operating Cost $12.58
699,000
561,200
209,400
32,300
660,000
235,400
193,200
$2
"Costs based on 824 ton/d facility with a
refuse:sludge at approximately 3:2.
591,100
ratio of
A-177
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CO-INCINERATION OF SLUDGE - SOLID WASTE INCINERATOR FACT SHEET 6.2.2
Description - Co-incineration is incineration using a combination of wastewater sludge and another combustible
material, other than natural gas or oil, in a single furnace. Some other combustible materials include: munic-
ipal solid waste, coal, wood wastes, textile wastes, and farm wastes.
One approach to co-disposal, that of using a solid waste incinerator as the volume reduction unit, was tried many
times. In the past 50 years, many municipal incinerators were used for rudimentary co-disposal. The problems of
material handling, feeding, and firing were never successfully addressed, and as a result the concept was gen-
erally abandoned. As the technology of municipal solid waste incineration matured into efficient, sophisticated
devices, co-incineration was again considered and great strides were made. A number of incinerators and waterwall
combustion units have been tested as co-incineration devices, and some plants are operating on a day-to-day basis.
These plants use the heat released from the solid waste combustion to dewater or dry the sludge to its autogenous
point. The form of the heat is either hot flue gas, steam from the waterwall combustion unit or waste heat
boiler, or heat from the fire itself. Mechanical dewatering devices in the co-disposal plants can be driven by
steam or electricity generated within the plant itself. The drying can take place in the furnace or in a separate
vessel.
Two plants in this country use flue gas to dry the sludge and then burn the sludge solids in the furnace.
Ansonia, Connecticut has a 200 ton/d (design) refractory incinerator. About 55 ton/d of refuse are disposed of in
an eight-hour shift. Sludge from the integrated wastewater treatment plant at about four percent solids is dried
in a high speed disk co-current spray dryer. Hot flue gases from the secondary combustion chamber at 1200 F are
introduced into the spray dryer. Vapors and dry solids are blown into the furnace above the second grate where
the solids burn in suspension. However, the dried sludge is presently not burned but used for fertilizer by local
residents.
Another small refractory incinerator, 50 ton/d average throughput, in Holyoke, Massachusetts, uses the same gen-
eral technique but the sludge, after mechanical dewatering to 28 percent solids, is dried in a rotary dryer. Hot
flue gas from the incinerator is used to directly heat the sludge in the dryer. The dried solids are then burned
in suspension above the refuse grates. No exportable energy is recovered in either of these plants.
A different technique was tested in Norwalk, Connecticut. The tests proved the viability of the idea and it is
being replicated in Glen Cove, New York. In this approach, the heat of the burning solid waste directly dries the
sludge and the dried solids burn along with the waste. This is accomplished by spraying the sludge at about five
percent solids into the charging chute forming a layer of sludge on the solid waste. As the solid waste flows
into the furnace from the charging chute, the sludge layer remains on top of the solid waste. In the furnace, the
heat from the burning solid waste first drives off the moisture from the sludge, and then the dry sludge solids
burn along with the solid waste on the grates. The plant at Glen Cove will have waste heat boilers installed and
the steam will be used to generate electricity.
Two co-incineration plants are currently operating in Europe. One is at Dieppe, France, the other at Krefeld,
West Germany. Both utilize a waterwall combustion unit to burn the solid waste and wastewater sludge.
Technology Status - At least five co-incineration plants are operating worldwide (three in the United States)
utilizing solid waste incinerators. Thus, the technical viability of this approach has been demonstrated on a
full scale basis, but, it is not widely used.
Applications - Use of a single device to dispose of both sludge and another solid waste material, thus reducing
capital and operating costs; derivation of wastewater treatment plant power and fuel requirements from a more
economical waste energy source; reduction of land requirements for disposal.
Limitations - A number of institutional constraints have to be resolved such as the existence of contracts with
private firms which define ownership of the solid refuse. Also, wastewater treatment and solid waste disposal are
often controlled by different government agencies. The co-incineration plant site must be within pumping distance
of the wastewater treatment plant. The minimum excess air rate for co-incineration in refuse incinerators is 150
percent (91). The minimum flue gas temperature suitable for odor destruction is 1400 F.
Typical Equipment/No. of Mfrs. (10, 77) -
Incinerator/10, Stokers/5, Air Supply Fans/40, Exhaust Gas Scrubbers/3, Ash Handling System/1, Refuse Handling and
Feed System/9.
Performance - Volume and weight reductions for co-incineration will be about the same as for separate incineration
of both materials.
Environmental Impact - Data is required to establish impact with various feed combinations; however, uncontrolled
particulate emission from a refuse incinerator would roughly double with co-incineration. Emission of SO^, NO^,
HC1 and CO is usually insignificant but must be evaluated in terms of the feed composition and the emission inven-
tory of the region (91). Available data indicate that toxic organics (PCB's, pesticides, etc.) will either be
destroyed by the thermal condition or will be retained in the particulate collection equipment and ash (91).
Volatile Hg emissions are usually low, but must be evaluated in relation to the ambient concentrations at the time
of design.
References - 8, 43, 65, 10, 77, 91
A-178
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CO-INCINERATION OF SLUDGE - SOLID WASTE INCINERATOR
FACT SHEET 6.2,2
FLOW DIAGRAM -
To Atmosphere
Combustion
Air Fan
Scrubber
Water
ENERGY NOTES (91) - Using the power and fuel cost/ton cited below, the electrical energy usage is 44 kWh/ton, and
the auxiliary fuel requirement is approximately 73,000 Btu/ton.
COSTS (91) - Based on mid-1975 costs for an incinerator with design capacity of 600 ton/d refuse, 224 tons/d
sludge. ENR Index = 2205
1. Capital costs include equipment, labor and material for installation, construction overhead and contingency
(15 percent on equipment modules only).
2. Manpower includes four shifts, seven d/wk operation with supervision and maintenance. Salary/overhead ranges
from $10,000 to $20,000/yr ($17,000 for operators and senior maintenance people). Twenty percent is added to
total manpower cost for overtime, vacations, holidays, etc.
3. Power costs: $.027/kWh. Fuel costs: $2.73/(10 Btu). Water and Sewer costs: $0.37/1000 gal. Residue
disposal cost: $4.00/ton.
CAPITAL COST
OPERATING COST
Item
Cost
Item
Cost Per* Total Annual
Ton Cost
Incinerator DCC $15,291,000
Drier Circuit:
Rotary Drier, Fan, Cyclone $ 1,477,000
Ductwork 138,000
Conveyors & Pug Mill 278,000
Subtotal 1,893,000
Additional Building 1,370,000
Direct Construction Cost $18,554,000
Design, Construction Management,
Start-up (15% of DCC) 2,783,000
Land {50,000 per acre) 500,000
Legal Fees (3% DCC) 557,000
Bond Discount (3% Total Cost) 672,000
Total Facility Cost $23,066,000
Facility Cost per ton/d $28,000
(Design Capacity)
REFERENCE - 91
Manpower
(46 employees)
Power
(1265 kWh/h)
Water/Sewer
(435 gal/min)
Auxiliary Fuel S Heating
(128,800 gal/yr)
Maintenance
(2.5% DCC)
Overhead
(1% DCC)
Residue Disposal
(161 ton/d)
Total Operating Cost
$3.61
1.20
0.29
0.20
2.25
0.90
0.94
$9.39
$ 744,000
247,700
59,700
41,200
463,800
185,500
193,200
$1,935,100
*Based on 824 tons of combined refuse/sludge
feed in a ratio of approximately 3:2.
A-179
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COMPOSTING SLUDGE, STATIC PILE FACT SHEET 6.2.3
Description - Wastewater sludge is converted to compost in approximately eight weeks in a four-step process:
Preparation - sludge is mixed with a bulking material such as wood chips or leaves, in order to facilitate
handling, to provide the necessary structure and porosity for aeration, and to lower the moisture content of the
biomass to 60 percent or less. Following mixing, the aerated pile is constructed and positioned over porous pipe
through which air is drawn. The pile is covered for insulation.
Digestion - The aerated pile undergoes decomposition by thermophilic organisms, whose activity generates a
concomitant elevation in temperature to 60 C (140 F) or more. Aerobic composting conditions are maintained by
drawing air through the pile at a predetermined rate. The effluent air stream is conducted into a small pile of
screened, cured compost where odorous gases are effectively absorbed. After about 21 days the composting rates
and temperatures decline, and the pile is taken down, the plastic pipe is discarded, and the compost is either
dried or cured depending upon weather conditions.
Drying and Screening - Drying to 40 to 45 percent moisture facilitates clean separation of compost from wood
chips. The unscreened compost is spread out with a front end loader to a depth of 12 inches. Periodically a
tractor-drawn harrow is employed to facilitate drying. Screening is performed with a rotary screen. The chips
are recycled.
Curing - The compost is stored in piles for about 30 days to assure no offensive odors remain and to com-
plete stabilization. The compost is then ready for utilization as a low grade fertilizer, a soil amendment, or
for land reclamation.
Modifications - 1. Extended high pile - pile height is extended to 18 ft using a crane (still experimental). Can
result in savings of space and materials. 2. Aerated Extended Pile - each day's pile is constructed against the
shoulder of the previous day's pile, forming a continuous or extended pile. Can result in savings of space and
materials.
Technology Status - Successfully demonstrated at four locations and projected to be capable of serving large
cities. Experiments are ongoing on various operating parameters.
Applications - Suitable for converting digested and undigested sludge cake to an end product of some economic
value. Insulation of the pile and a controlled aeration rate enable better odor and quality control than the
windrow process from which it evolved.
Limitations - The drying process is weather-dependent and requires at least two rainless days. The use of compost
on land is limited by the extent to which sludge is contaminated by heavy metals and industrial chemicals. In-
dustrial pretreatment of wastewater treatment plant influent should increase the availability of good quality
sludges for composting.
Typical Equipment/No, of Mfrs. (83) - Front-end loader/16 or crane/more than 100; four inch perforated plastic
pipe/more than 100; blower/more than 100; timer/more than 100; tractor-drawn/23; harrow/42; rotary screen/55.
Performance - Sludge is generally stabilized after 21 days at elevated temperatures. Maximum temperatures of
between 60° to 80°C are produced during the first three to five days, during which time odors, pathogens and weed
seeds are destroyed. Temperatures above 55 C (131 F) for sufficient periods can effectively destroy most human
pathogens. The finished compost is a humus-like material, free of malodors, and useful as a soil conditioner
containing low levels of essential plant macronutrients such as nitrogen and phosphorus and often adequate levels
of micronutrients such as copper and zinc.
Chemicals Required - None
Residuals Generated - Final product is compost.
Design criteria (79) - Construction of the pile for a 10 dry ton/d (43 wet tons) operation: 1. A 6-in. layer of
unscreened compost for base. 2. A. 94 ft loop of 4-in. dia. perforated plastic pipe is placed on top (hole dia.
0.25 in.). 3. Pipe is covered with 6-in. layer of unscreened compost or wood chips. 4. Loop is connected to a
1/3 hp blower by 14 ft of solid pipe fitted with water trap to collect condensate. 5-3 Timer is set for cycle of
4 minutes on and 16 minutes off. 6. Blower is connected to conical scrubber pile (2yd wood chips covered with
10yd screened compost) by 16 ft of solid pipe. 7. Sludge (wet) - wood chip mixture in a volumetric ratio of
1:2.5 is placed on prepared base. 8. A 12-in. layer of screened compost is placed on top for insulation.
Air Flow: 100 ft /h/ton of sludge; land area requirement for 10 dry tons processed daily: 3.5 acres, including
runoff collection pond, bituminous surface for roads, mixing, composting, drying, storage, and administration
area. Pile dimension: 53 ft X 12 ft X 8 ft high. Population equivalent, 100,000.
Process Reliability - High degree of process reliability through simplicity of operation. Thoroughness (percent
stabilization) is a function of recycle scheme, porosity distribution in pile, and manifold design.
Toxics Management - Heavy metals entering the process remain in the final product. The degree of removal of
organic toxic substances is not defined.
Environmental Impact - Potential odor problems can occur for a brief period between the time a malodorous sludge
arrives at site, is mixed and is covered by the insulating layer. Human pathogen generation and aerosol distribu-
tion potential dictates careful attention to downwind land use.
References - 78, 79, 80, 81, 82
A-180
-------
COMPOSTING SLUDGE, STATIC PILE
FACT SHEET 6.2,3
FLOW DIAGRAM
SCREENED
COMPOST
WOOOCHIPS
AND SLUDGE
PERFORATED
PIPE
FILTER PILE
SCREENED COMPOST
ENERGY NOTES -
Electricity consumed for a 10 dry ton/d operation = 75,000 kWh/yr or 7500 kwh/yr/dry ton sludge.
Fuel consumed for a 10 dry ton/d operation =2.29 billion kWh/yr or 229 MkWh/yr/dry ton sludge.
COSTS (1976 dollars) ENR Index = 2401
1. Quantity processed, 10 dry tons/d; compost distribution will realize no net revenues or costs to the
municipality.
2. Blower is 1/3 hp; front-end loader is equipped with 3.5 yd bucket.
3. Sewer line installation - 400 ft of 8 inch sewer line @ $35/ft.
4. Asphalt composting pad costs include grading, 12 inch crushed stone, 4 inches of asphalt.
5. Site is operated 8 h/d, 7 d/wk; staff includes 1 Superintendent, 4 equipment operators; labor costs include:
5 wks off for paid sick leave, vacations, holidays; $400/person for health insurance; 6% FICA; 0.3 man yr of
overtime. Superintendent receives $7.50/h; operators receive $6/h.
6. Equipment maintenance 6 percent purchase price; insurance estimated 1 percent purchase price.
7. Gasoline 57/gal, 1.1 gal/dry ton loading; diesel 41t/gal, 3.5 gal/dry ton loading;
electricity 2C/kWh, 17.3 kWh/dry ton loading; woodchips, $3.50/yd .
CONSTRUCTION COST
Item
Site development:
Asphalt pad (1.5 acre)
Roads, administration
Electrical work
Sewer
Pond, drainage
Equipment:
Office trailer
Storage
Front end loaders (2 pieces)
Screen
Tractor
Pickup
Blowers (33 pieces)
Construction Cost
REFERENCES - 79, 82
Dollars
83,800
13,000
20,000
14,000
28,000
5,000
1,500
106,000
16,300
4,700
4,700
2,500
$299,500
OPERATION AND MAINTENANCE COST
Operating Costs:
Woodchips
Plastic pipe
Gasoline
Diesel
Electricity
Equipment maintenance
Equipment insurance
Pad, road maintenance
Water/sewer
Labor
Miscellaneous supplies
Total
35,000
12,200
2,300
5,300
1,500
8,400
1,400
1,200
500
77,500
4,400
$/dry ton
9.60
3.34
.63
1.45
.41
2.30
.44
.33
.14
21.23
1.20
149,700 41.01*
* O&M costs for a 50 dry ton/d operation have been
estimated to amount to $28/dry ton.
**To convert construction cost to capital cost see Table A-2.
A-181
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COMPOSTING SLUDGE, WINDROW FACT SHEET 6.2.4
Description - Composting is the microbial degradation of sludge and other putrescible organic solid material by
aerobic metabolism in piles or windrows on a surfaced outdoor area. The piles are turned periodically to provide
oxygen for the microorganisms to carry out the stabilization and to carry off the excess heat that is generated by
the process. When masses of solids are assembled, and conditions of moisture, aeration and nutrition are favor-
able for microbial activity and growth, the temperature rises spontaneously. As a result of biological self-
heating, composting masses easily reach 60°C (140°F) and commonly exceed 70°C (150°F). Peak composting tempera-
tures approaching 90 C (194 F) have been recorded. Temperatures of 140 to 160 F serve to kill pathogens, insect
larvae and weed seeds. Nuisances such as odors, insect breeding and vermin harborage are controlled through rapid
destruction of putrescible materials. Sequential steps involved in composting are preparation, composting, curing
and finishing.
Preparation - To be compostable, a waste must have at least a minimally porous structure and a moisture content of
45 to 65 percent. Therefore, sludge cake, which is usually about 20 percent solids, cannot be composted by itself
but must be combined with a bulking agent, such as soil, sawdust, wood chips, refuse, or previously manufactured
compost. Sludge and refuse make an ideal process combination. Refuse brings porosity to the mix, while sludge
provides needed moisture and nitrogen, and both are converted synergistically to an end product amenable to
resource recovery. The sludge is suitably prepared and placed in piles or windrows.
Composting - The composting period is characterized by rapid decomposition. Air is supplied by periodic turnings.
The reaction is exothermic, and wastes reach temperatures of 140°F to 160°F or higher. Pathogen kill and the
inactivation of insect larvae and weed seeds are possible at these temperatures. The period of digestion is
normally about six weeks.
Curing - This is characterized by a slowing of the decomposition rate. The temperature drops back to ambient, and
the process is brought to completion. The period takes about two more windrow weeks.
Finishing - If municipal solid waste fractions containing non-digestible debris have been included, or if the
bulking agent such as wood chips is to be separated and recycled, some sort of screening or other removal pro-
cedure is necessary. The compost may be pulverized with a shredder, if desired.
Common Modifications - Composting by the static pile method is discussed in Fact Sheet 6.2.3. Composting within
a vessel is an emerging technology.
Technology Status - Successfully demonstrated.
applications - A sludge treatment method that successfully kills pathogens, larvae and weed seeds. Is suitable
for converting undigested primary and/or secondary sludge to an end product amenable to resource recovery with a
minimum capital investment and relatively small operating commitment.
Limitations - A small porous windrow may permit such rapid air movement that temperatures remain too low for
effective composting. The outside of the pile may not reach temperatures sufficiently high for pathogen des-
truction. Pathogens may survive and regrow. Sale of product may be difficult.
Typical Equipment/No, of Mfrs. (83) - Commonly available equipment can be used, including front-end loaders/16;
traotor-drawn/23; harrow/42; rotary screen/55. Equipment is currently being developed specifically for sludge
composting.
Performance - Sludge is converted to a relatively stable organic residue, reduced in volume by 20 to 50 percent.
The residue loses its original identity with respect to appearance, odor and structure. The end product is
humified, has earthy characteristics; pathogens, weed seeds and insect larvae are destroyed.
Chemical Requirements - None
Residuals Generated - None
Design Criteria - Approximate land requirement: 1/3 acre/dry ton sludge daily production, which is roughly equiv-
alent to a population of 10,000 with primary and secondary treatment. Windrows can be 4 to 8 ft high, 12 to 25 ft
wide at the base, and variable length. Sludge cannot be composted by itself but must be combined with a bulking
agent to provide the biomass with the necessary porosity and moisture content. Biomass criteria: moisture con-
tent, 45 to 65 percent; C/N ratio between 30 to 35:1; C/P, 75 to 150:1; air flow 10 to 30 ft air/d/lb VS.
Detention time, six weeks to 1 year.
Process Reliability - Highly reliable. Ambient temperatures and moderate rainfall do not affect the process.
Environmental Impact - Is relatively land intensive; potential for odors; may be aesthetically unacceptable. The
compost product represents an environmental benefit when used as a soil amendment. Other uses include wallboard
production, livestock feed, litter for the chicken industry, and adsorbent for oil spill cleanup. Human pathogen
generation and aerosol distribution potential dictates careful attention to downwind land use.
References - 8, 20, 33, 202, 203, 205
A-182
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COMPOSTING SLUDGE, WINDROW
FACT SHEET 6.2.4
FLOW DIAGRAM -
Air
Sludge
Mixing
Composting
Curing
T
| (if woodchips are recycled)
Screening
Compost _
non-digestible
ENERGY NOTES - Actual fuel consumption varies with specific site and operating conditions. Fuel consumption for
some typical construction equipment that can be utilized for sludge composting is presented in Fact Sheet 6.1.10
A mixer-separator has been developed that mixes sludge and bulking agent and also separates compost from the
bulking agent. The 125 yd /h mixer-separator consumes approximately 3 gal/h of diesel fuel.
COSTS - Assumptions: ENR Index = 2475
1. Service life, 17 years
2. Construction costs include asphalt pads, roads, sewer, drainage pond, electrical work, engineering.
3. Sludge production rate = 900 Ib/Mgal (dry solids), digested.
4. Land requirement, 0.35 acres/(ton/day). Assumed land cost = $10,500/acre.
5. Costs apply to composting of digested er raw bi9logical sludge.
6. Adjustment factor: To adjust for sludge composting rates different from 900 Ib/Mgal, enter cost curves at
effective flow (QE>.
^DESIGN X (New Design Sludge Mass)
900 Ib/Mgal
Note: Costs other than labor are not given in Reference 3 but are assumed to include materials, fuel, etc.
CONSTRUCTION COST
10
1 0
001
1 0
OPERATION & MAINTENANCE COST
Q
o
0 1
01
1 0 10
Wastewater Flow. Mgal/d
100
0001
Total
0 1
1 0 10
Wastewater Flow, Mgal/d
100
REFERENCES - 3, 205
To convert construction cost to capital cost see Table A-2.
A-183
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INCINERATION OF SLUDGE, FLUIDIZED BED FURNACE (FBF) FACT SHEET 6.2.5
Description - Sludge incineration is a two-step process involving drying and combustion after preliminary dewater-
ing. A typical sludge contains 75 percent water and 75 percent volatiles in dry solids. Self-sustained combus-
tion without supplementary fuel is often possible with dewatered raw sludges having a solids concentration greater
than 30 percent.
The FBF is a vertically oriented, cylindrically shaped, refractory lined, steel shell which contains a sand bed
and fluidizing air distributor. The FBF is normally available in diameters of 9 to 25 feet and heights of 20 to
60 feet. There is one industrial unit operating with a diameter of 53 feet. The sand bed is approximately 2.5
feet thick and rests on a refractory lined air distribution grid containing tuyeres through which air is injected
at a pressure of 3 to 5 Ib/in to fluidize the bed. Bed expansion is approximately 80 to 100 percent. Tempera-
ture of the bed is controlled between 1400 F and 1500 F by auxiliary burners and/or a water spray or heat
removal system above the bed. Ash is carried out the top of the furnace and is removed by air pollution control
devices, usually wet venturi scrubbers. Sand is lost by attrition at an approximate rate of five percent of the
bed volume every 300 hours of operation. Furnace feed can be introduced either above or directly into the bed
depending on the type of feed. Generally, sludge is fed directly into the bed.
Excess air requirements for the FBF vary from 20 to 40 percent. It requires less supplementary fuel than a multiple
hearth furnace. An oxygen analyzer in the stack controls the air flow into the reactor and the auxiliary fuel
feed rate is controlled by a bed temperature controller.
Start-up fuel requirements are very low, and no fuel is required for start-up following an overnight shutdown.
The FBF is very attractive for intermittent operation. Afterburners are not required to comply with air pollution
regulations.
Common Modifications - An air preheater is used in conjunction with a fluidized bed to reduce fuel costs. Also,
cooling tubes may be submerged in the bed for purposes of energy recovery.
Technology Status - The first fluidized bed wastewater sludge incinerator was installed in 1962. There are now
many units operating in the United States with capacities of 200 to 1000 Ib/h of dry solids.
Applications - Reduction of sludge volume, thereby reducing land requirements for disposal. Energy recovery
potential. Most suitable where hauling distances to disposal sites are long, or where regulations concerning
alternative methods are prohibitive.
Limitations - Since a minimum amount of air is always required for bed fluidization, fan energy savings during
load turndown (i.e. sludge feed reduction) are minor. Generally not cost effective for small plants.
Typical Equipment/No, of Mfrs. - FBF/6, Screw Pumps/4, Air Fans/42, Gas Scrubbers/3, Ash Handling Systems/I
Performance - The mass of dry solids is reduced to 25 to 35 percent of the amount entering the unit.
Design Criteria - Bed loading rate = 50 to 60 Ib wet solids/ft /hr. Superficial bed velocity = 0.4 to 0.6 ft/s.
Sand effective size = 0.2 to 0.3 mm (uniformity coeff = 1.8), Operating temperature = 1400 to 1500 F (normal) -
2200°F+ (maximum), bed expansion = 80 to 100 percent, sand loss = 5 percent of bed volume per 300 hours of oper-
ation.
Unit Process Reliability - Some extensive maintenance problems have occurred with air preheaters. Scaling of the
venturi scrubbers has also been a problem. Screw feeds and screw pump feeds are both subject to jamming because
of either overdrying of the sludge feed at the incinerator or because of silt carried into the feed system with
the sludge. Another frequent problem has been the burnout of spray nozzles or thermocouples in the bed.
Environmental Impact - Particulate collection efficiencies of 96 to 97 percent are required to meet current
emission standards. There are very few data on the amount of toxic metals which are volatilized and discharged.
Limited test data (8) indicate that 4 to 35 percent of the mercury entering an incinerator with emission controls
will volatilize and be emitted to the atmosphere (excluding particulate forms). Gaseous emissions of CO, HC1,
SO and NO may be appreciable; additional air pollution control measures may be necessary. Pesticides and PCB's
are found in the sludge, but tests indicate that they can be destroyed during incineration and should not be a
problem.
References: - 3, 8, 10, 25, 43, 56, 77
A-184
-------
INCINERATION OF SLUDGE, FLUIDIZED BED FURNACE (FBF)
FACT SHEET 6.2.5
FLOW DIAGRAM -
Furnace Exhaust
Gas Exhaust
Bed Coils for
Heat Recovery
(not used in
this analysis
Radiation
Supplemental
Fuel
Sludge Feed
Fluid
Bed
Furnace
rv
/Wenturi
Recycle Water
X
« Sc
* Wa
sh
Makeup Water
Wet Scrubber
Scrubber
Drain
ENERGY NOTES - Using the design basis below, electrical energy requirements are approximately 90,000 kWh/yr/dry &
ton/d or 85,000 kWh/yr/Mgal/d plant flow; fuel requirements are approximately 90 gal/dry ton of sludge or 13 x 10
Btu/dry ton. Fuel requirements are very sensitive to the moisture content of the sludge and other factors. As a
result, adjustments should only be made after detailed study for each case.
COSTS -Assumptions: ENR Index = 2475
Design Basis:
Construction costs include reactor, air blowers, and accessories, preheaters, scrubbers, fuel pumps, and building.
Costs are for undigested dewatered primary and secondary sludge (1,900 Ib/Mgal at 20 percent solids; 75 percent
volatile) .
Operations:
Fuel cost
100
Plant flow, Mgal/d
0.1
1.0
10.0
100.0
$2.66/MBtu. Power cost = $0.02/kWh.
CONSTRUCTION COST
Operating, d/wk
1
7
7
7
Operating, h/d
20
20
20
20
OPERATION & MAINTENANCE COST
10
1 0
1 0
0 1
1-001
1 0 10
Wastewater Flow, Mgal/d
100
0001
Total
,Labor_
0,1
001
0.001
0 1
1 0 10
Wastewater Flow, Mgal/d
100
0.0001
REFERENCE - 3
*To convert construction cost to capital cost see Table A-2.
A-185
-------
INCINERATION OF SLUDGE, HULTIPLE HEARTH FURNACE (NHF) FACT SHEET 6.2.6
Description - Sludge incineration is a. two-step process involving drying and combustion after preliminary dewater-
ing. A typical sludge is 80 percent water and has a dry solids volatility of 75 percent. Self-sustained combus-
tion without supplementary fuel is often possible with dewatered raw primary sludges which can frequently be
dewatered to 30 percent solids.
The MHF is a vertically oriented, cylindrically shaped, refractory lined, steel shell {diameter = 4 to 25 ft)
containing 4 to 13 horizontal hearths positioned one above the other. The hearths are constructed of high heat
duty fire brick and special fire brick shapes. Sludge is raked radially across the hearths by rabble arms which
are supported by a central rotating shaft that runs the height of the furnace. The cast iron shaft is motor
driven with provision for speed adjustment from 1/2 to 1-1/2 r/min. Sludge is fed to the top hearth and proceeds
downward through the furnace from hearth to hearth. Inflow hearths have a central port through which sludge
passes to the next lower hearth. Outflow hearths have ports on their periphery. These ports tend to regulate
gas velocities also. The central shaft contains internal concentric flow passages through which air is routed to
cool the shaft and rabble arms. The flow of combustion air is countercurrent to that of the sludge. Gas or oil
burners are provided on some hearths for start-up and/or supplemental use as required.
The rabble arms provide mixing action as well as movement to the sludge so that a maximum sludge surface is
exposed to the hot furnace gases. Because of the irregular surface left by the rabbling action, the surface area
of sludge exposed to the hot gases is as much as 130 percent of the hearth area. While there is significant
solids-gas contact time on the hearths, the overall contact time is actually still greater, due to the fall of
the sludge from hearth to hearth through the countercurrent flow of hot gases.
The various phases of the incineration process occur in three zones of the MHF. The drying zone consists of the
upper hearths, the combustion zone consists of the central hearths, and the lower hearths comprise the cooling
zone. Temperatures in each zone are:
Drying zone - sludge about 100 F; air about 800 F
Burning zone - sludge and air about 1500 F
Cooling zone - sludge about 400 F, air about 350 F.
Common Modifications - An after burner fired with oil or gas is provided where required by local air pollution
regulations to eliminate unburned hydrocarbons and other combustibles.
Technology Status - The MHF is the most widely used wastewater sludge incinerator in the United States today. As
of 1970, 120 units have been installed.
Applications - Reduction of sludge volume thereby reducing land requirements for disposal. Energy recovery
potential. Used in plants that have long hauling distances to land or ocean disposal sites or where regulations
prohibit these alternate disposal methods.
Limitations - capacities of MHF's vary from 200 to 8,000 Ib/h of dry sludge. Maximum operating temperatures are
limited to 1700°F. With high energy feeds there may be operational problems. The MHF requires 24 - 30 hours for
furnace warm-up or cool-down to avoid refractory problems. Failure of rabble arms and hearths have also been
encountered. Nuisance shutdowns have also occurred due to ultraviolet flame scanner malfunctions. Thickening
and dewatering pretreatment is required.
Typical Equipment/No, of Mfrs. (10, 77) - MHF/6; flapgate valves/6; cooling and combustion air fans/42,- sludge
conveyors/7; gas scrubber/3.
Performance - Dry solids are reduced to 20 to 25 percent of the mass entering the unit. The recoverable heat
ranges from 18 percent of the total heat input (sludge and supplementary fuel) at 20 percent solids concentration
to 45 percent of the total heat input at 40 percent solids concentration.
Design Criteria - Maximum operating temperature = 1700°F. Hearth Loading Rate = 6 to 10 Ib wet solids/ft /h
with a dry solids concentration of 20 to 40 percent. Combustion air flow = 12 to 13 Ib/lb dry solids. Shaft
cooling air flow = 1/3 to 1/2 of combustion air flow. Excess Air = 75 percent to 100 percent (43).
Environmental Impact - Particulate collection efficiencies of 96 to 97 percent are required to meet current
emission standard. There are very few data on the amount of toxic metals which are volatilized and discharged.
Limited test data (8) indicate that 4 to 35 percent of the mercury entering an incinerator with emission controls
will volatilize and be emitted to the atmosphere (excluding particulate forms). Gaseous emissions of CO, HC1,
SO and NO are expected to be acceptable. Pesticides and PCB's are found in the sludge, but tests indicate that
they can be destroyed during incineration and should not be a problem.
References - 3, 8, 10, 25, 43, 77
A-186
-------
INCINERATION OF SLUDGE, MULTIPLE HEARTH FURNACE (MHF)
FACT SHEET 6,2,6
FLOW DIAGRAM -
Gas Exhaust
Shaft Cooling Air Not Returned
Shaft Cooling
Air
Cooling Air
ENERGY NOTES - Using the design assumptions below, electrical energy requirements are approximately 31,000,
135,000 and 1,250,000 kwh/yr for 1, 10 and 100 Mgal/d plant flow. Fuel requirements for startup and incineration
amount to approximately 4,500 x 10 Btu/yr/Mgal/d. Fuel requirements are very sensitive to the moisture content
of the sludge and other factors. As a result, adjustments should only be made after detailed study of the case.
COSTS - Assumptions: ENR Index = 2475
Design Basis:
Construction costs include incinerator, building, sludge conveyor, ash handling equipment, gas scrubbers. Costs
are for undigested dewatered primary and secondary sludge (1,900 Ib/Mgal at 20 percent solids; 75 percent volatile).
Operations:
Plant flow, Mgal/d
0.1
1.0
10.0
100.0
Operating, d/wk
1
7
7
7
Operating, h/d
20
20
20
20
Fuel requirements for warm-up and incineration are 4,500 x 10 Btu/yr/Mgal/d.
Fuel cost = $2.66/MBtu. Power cost = $0.02/kWh.
100
CONSTRUCTION COST
OPERATION & MAINTENANCE COST
10
1 0
0 1
01
1 0 10
Waslewater Flow, Mgal/d
100
0 1
001
0001
0001
1 0 10
Wastewater Flow, Mgal/d
100
00001
BEFE HENCE - 3
*To convert construction cost to capital cost see Table A-2.
A-187
-------
CO-DISPOSAL BY STARVED AIR COMBUSTION FACT SHEET 6.2.7
Description - Co-disposal of sludge by starved air combustion (SAC) is an extension of the process described in
Fact Sheet 6.2.8 using waste materials such as municipal solid waste, wood wastes, farm wastes, etc. as fuel
additives to allow operation of the unit without auxiliary fossil fuel in the case of high moisture content sludge
or sludges with low solids heating value.
At a test run at the Central Contra Costa Sanitary District operated wastewater treatment plant in Concord, Cali-
fornia, a 16-ft diameter, 6-hearth, multiple hearth furnace (MHF) processed a combination of sludge and refuse
derived fuel (RDF). Mixed municipal refuse was shredded, classified, and screened prior to addition to the MHF
where the RDF was the light fraction from the air classifier. The sludge had a solids content of 16 percent, a
volatile solids content of 75 percent, and a heating value of 9,000 Btu/lb dry solids, whereas the RDF had a
solids content of 75 percent, very few inerts, and a heating value of 7,500 Btu/lb of dry solids. The furnace
feed rate was varied from pure sludge to pure RDF. A combustible gas was produced with a heating value of 130
Btu/sdft . This combustible gas could be fired in a waste heat boiler for steam production, used as the fuel for
a lime recalcination furnace, or used for space heating.
During the test, the RDF could be fed to hearths 3 or 1. Sludge was always fed to hearth 1. Temperatures were
maintained by controlling the amount of air fed to the furnace. The off-gases from the furnace were allowed to
burn in an afterburner with the introduction of combustion air. Afterburner temperatures were approximately
2200°F, although the gas could be combusted to produce a temperature as high as 2500 F with no supplemental fuel
addition.
The major shaft furnace systems available, the Purox (oxygen enrichment) and Torrax (regenerative heat recovery)
units by Union Carbide Co. and The Carborundum Co., respectively, have similar basic operating principles. Refuse
is charged at the top of the refractory lined shaft, providing a seal, and, as it descends through the furnace,
hot pyrolytic gases from the slagging and combustion zones move in a countercurrent direction, thus providing pre-
ignition and drying of the sludge and refuse. Preheated air or oxygen-enriched air is injected into the com-
bustion zone at the base of the shaft furnace, where combustion of the pyrolyzed char occurs.
Preheating and oxygen enrichment serve essentially the same purpose: maintaining a furnace temperature high enough
(2500-3000°F) to form a slag and to produce a pyrolysis gas with as high a heating value as possible. The slag
formed is virtually free of combustibles. The cooled gases (low heating value), after preliminary cleaning, can
be burned in a secondary combustion chamber with energy recovery in the form of a waste-heat boiler.
Technology Status - Technical feasibility has been demonstrated, however, there are no plants in commercial use.
Applications - Reduction in volume of two solid waste streams and energy conservation; use a single device to
dispose of two waste products, thereby realizing capital and operating cost benefits.
Limitations - Institutional constraints may hamper implementation; for instance, in many localities, wastewater
treatment and solid waste disposal are controlled by different governmental agencies. Many communities have long-
term (15 to 20 years) contracts with private firms for refuse handling and disposal which define ownership of the
refuse. See Fact Sheets on Multiple Hearth Furnaces and Fluid Bed Furnaces for other limitations. In shaft
furnaces, proper temperatures in the slag tap area must be maintained to prevent slag freezing. The Purox system
and the MHF require a shredded refuse feed.
Typical Eguipment/No. of Mfrs. (10, 77, 97) - SAC reactors/10; scrubbers/3; ash disposal system/1; fans/42; waste
heat boiler/27; sludge dewatering device/15; sludge conveyors/7; combustible material preparation and feed sys-
tem/25.
Performance - Quantity of dry solids (combined sludge and PDF) is reduced to 19 to 26 percent of amount entering
reactor (43).
Design Parameters - For Multiple Hearth Furnaces (43):
Hearth Sludge Loading Rate = 11 to 13 Ib wet solids/(h)(ft )
Unit Process Reliability - No data available. MHF units have experienced failures of rabble arms and hearths
along with nuisance trips due to flame scanner malfunction. Fluid bed units have experienced scaling of scrubbers
with bed media and plugging of sludge feed systems. Freezing of slag bed and contamination of slag bed with
refuse have been experienced on shaft furnace systems.
Environmental Impact - Data required to evaluate is not available for this process. However, the impact will
depend on compositions of feed material and operating conditions. Hydrocarbons and CO emissions are not of
concern since product fuel gas is sought. SO- and NO emission from reactor may be reduced relative to co-
incineration due to deficiency of oxygen; however, higher temperatures in the afterburner could cause a N0x
problem.
References - 43, 10, 77, 91, 97, 148, 221, 222, 223, 224, 226
A-188
-------
CO-DISPOSAL BY STARVED AIR COMBUSTION
FACT SHEET 6.2.7
FLOW DIAGRAM
«<
e
r~
Waste
Heat
Raibci
*1
Dust
Collector
To AUacsph
Preheated Air
or Oxygen
Water to
Treatment Plant
Solids to Disposal
ENERGY NOTES - From the estimate below, electrical power requirements are 51 kWh/t of refuse and sludge.
Auxiliary fuel requirements are 6.2 gal of fuel oil or 780,000 btu/t of refuse and sludge.
COSTS - Mid-1975 dollars; ENR Index = 2212, Co-incineration/SAC (sludge and refuse). Design capacity
600 ton/d refuse; 224 ton/d sludge, annual capacity 206,000 tons.
Capital Costs Include: Equipment, labor and materials for installation, construction overhead and contingency at
15 percent of each equipment module.
Manpower Costs Include: Four shifts, seven days per week operation; supervision and maintenance. Salary and
overhead ranged from $10,000 to $20,000 ((operators and senior maintenance people at $17,000 per year). Twenty
percent is added for overtime, vacations, holidays, etc.
Power Costs: $0.027/kwh
Water and Sewer Costs: $0.37/1000 gal
Fuel Costs: $2.73/10 Btu
Residue Disposal Cost: $4/ton
Item
Capital Cost
Item
Cost
Operating Cost
Cost Per
Ton*
Total Annual
Cost
Two Shaft Furnaces $18,125,000
Additional Building 1,541,000
Direct Construction Cost $19,666,000
Design, Construction Management 2,950,000
Start-Up (15% DCC)
Land ($50,000/acre) 250,000
Legal Fees (3% DCC) 590,000
Bond Discount (3% Total Cost) 704,000
Total Facility Cost $24,160,000
Facility Cost Per ton/d $29,300
(Design Cap.)
Manpower $ 3.15 $648,000
(42 employees)
Power 1.37 282,000
(1450 kWh/h)
Water/Sewer 0.23 48,000
(300 gal/min)
Auxiliary Fuel & Heating 2.14 440,700
(1,057, 400 gal/yr)
Maintenance 2.37 491,600
(2.5% DCC)
Overhead .95 196,700
(1% DCC)
Residue 0.71 146,500
(488 ton/d
Total Operating Cost
$10.92 $2,253,600
* Based on Annual Throughput.
REFERENCE - 91
A-189
-------
STARVED AIR COMBUSTION OF SLUDGE FACT SHEET 6.2.8
Description - The process utilizes equipment and process flows similar to incineration except that less than the
theoretical amount of air for complete combustion is supplied. Autogenous starved air combustion (SAC) can be
achieved with a sludge solids concentration greater than 25 percent. For lower concentrations, an auxiliary fuel
may be required, depending on the percent volatiles in the solids. High temperatures decompose or vaporize the
solid components of this sludge. The gas phase reactions are pyrolytic or oxidative, depending on the concen-
tration of oxygen remaining in the stream. Under proper control, the gas leaving the vessel is a low Btu fuel gas
that can be burned in an afterburner to produce power and/or thermal energy. Some processes utilize pure oxygen
instead of air and thus produce a higher Btu fuel gas. The solid residue is a char with more or less residual
carbon, depending on how much combustion air had to be supplied to reach the proper operating temperatures. Since
the process is neither purely pyrolytic nor purely oxidative, it is called starved-air combustion or thermal gasi-
fication, rather than pyrolysis, other processes still in the development stage use indirect heating, rather than
the partial combustion. These are true pyrolysis processes. SAC reduces the sludge volumes and sterilizes the
end product. Unlike incineration, it offers the potential advantages of producing useful by-products and of
reducing the volume of sludge without large amounts of supplementary fuels. The gas which is produced has a heat
value up to 130 Btu/standard dry cubic foot using air for combustion and is suitable for use in local applications,
such as combustion in an afterburner or boiler or for fuel in another furnace. SAC has a higher thermal efficiency
than incineration due to the lower quantity of air required for the process. In addition, capital economies can
be realized due to the smaller gas handling requirements.
Furnaces may be operated in one of three modes resulting in substantially different heat generation and residue
characteristics. The Low Temperature Char (LTC) mode only pyrolyzes the volatile material thereby producing a
charcoal-like residue with a high ash content, the High Temperature Char (HTC) mode produces a charcoal-like
material converted to fixed carbon and ash, and the Char Burned (CB) mode reacts away all carbon and produces ash
as a residue. Heat recovered is maximum for the CB mode, less for the HTC mode, and substantially less for the
LTC mode of operation.
SAC operation has shown the following advantages in addition to those discussed above: easier to control than a
standard incinerator; more stable operation with little response to changes in feed; more feed capacity as com-
pared to an equal area for incineration; all equipment used is currently being manufactured; less air pollutants
and easier air pollution control management; lower sludge solids content required for autogenous operation.
Technology Status - Autogenous SAC of sludge has been demonstrated at a full scale Multiple Hearth Furnaces (MHF)
project at the Central Contra Costa Sanitary District in California. One SAC unit for disposal of sludge from a
40 Mgal/d industrial wastewater treatment plant is reported to have gone on stream in 1978 and other units are out
for bid.
Applications - Reduction of sludge volume and production of fuel gas for a nearby combustor or furnace. Most
existing MHF's can easily be retrofitted to operate in the SAC mode.
Limitations - There are significant disadvantages, such as:
Need for afterburner may limit use in existing installations due to space problems.
Relatively large amount of instrumentation is required.
Must be very careful of bypass stack exhaust since furnace exhaust is high in hydrocarbons and may be com-
bustible in air. This may result in bypassing only after afterburning with appropriate emergency controls in
some areas.
Corrosivity of furnace exhaust gases.
Combustibles in ash may create ultimate disposal problems.
Sludge volume reduction lower than with incineration.
Requires recovery of the energy in the product gas to fully realize the improved efficiency.
Typical Equipment/No, of Mfrs. (10, 77, 97) - SAC Reactor/10, Waste Heat Boiler/27, Exhaust Gas Scrubbers/3,
Sludge Dewatering Devices/15, Afterburner/10.
Performance - Unit can operate without auxiliary fuel, including afterburner, with sludge dewatered to the range
of 29 to 39 percent solids. Based on a limited number of pilot scale tesljS, the off-gas from an MHF unit oper-
ating in the SAC mode, with sludge alone, ranges from 18 to 73 Btu/std ft .
Design Criteria - MHF systems - Hearth loadings of 9 to 15 Ib wet (22 percent) solids/ft /h; for autogenous com-
bustion, sludge solids content 25 to 39 percent depending upon volatility. Off-gas heating value dependent upon
operating mode.
Unit Process Reliability - Mechanical function of MHF units under the SAC mode is expected to be similar to the
conventional operating modes. Increased operating stability is expected to result in higher process reliability.
Environmental Impact - Air pollution can be expected to be less of a problem due to the lower air flows and the
potential for particulate carryover. Data to date indicate conventional equipment can achieve acceptable con-
trols. Depending upon the mode of operation, heavy metals in the sludge can be retained in the residue.
References - 8, 43, 10, 77, 97, 148, 220, 221, 222, 223, 224.
A-190
-------
STARVED AIR COMBUSTION OF SLUDGE
FLOW DIAGRAM -
C
t ,
Shaft Cooling Air
Returned to Furnace
Sludge Dewatering
and
Feed System
Sludge
r Feed
H
Shaft
Multiple
Hearth
Pyrolytic
Reactor
^
i
Cooling Air
ENERGY NOTES - Using assumptions below, the electric*
startup fuel requirements are 3.1 gal fuel oil or 0.
COSTS - Third quarter 1978 dollars. ENR Index = 2829
FACT SHEET 6.2.8
Gas Exhaust
t ,
Shaft Cooling Air Not Returned ^
Shaft Cooling Air
l 'Returned to After -
ombustion__
"Air *"
Furnace Afterburner
Exhaust /V
Boiler
ArLeLLuiauy rSi^u'st" 1
Exhaust. 1.. __^.I.. Wut f-crubbor
Waste V
Heat A
„ . , / \ Scrubber
Boiler / \ ,<______
Mv
Recoverable Heat I
Supplemental | Draitl >
Fuel
Radiation ~~ Precooler and
Combustion Venturi Water
Air Connected Power
Ash
al energy requirements are 23 kWh/ton, and the auxiliary or
13 X 10 Btu/ton of sludge.
1. 324 ton/d design capacity at 40 percent dry solids. Annual throughput 80,000 tons.
2. Direct construction cost includes Multiple Hearth Furnace installed, with drives, fans, motor controls, gas
scrubber, external afterburner, ash handling system, auxiliary fuel system, instrumentation, piping, paint-
ing, initial operation and test. .
3. Manpower costs = $17,500/yr average; power cost = $0.02AWh; fuel cost = $2.73/10 Btu; water and sewer costs
= $0.37/1,000 gal; residue disposal = $5/ton.
Capital Cost Operating Cost
Direct Construction Cost (DCC) $2,325,000
Design, Construction Manage-
ment (20% DCC) 465,000
Land ($50,000/acre) 250,000
Legal fee (3% DCC) 69,750
Bond discount (3% Total Cost) 99,000
Total Cost $3,325,000
REFERENCES - 91, 225
Cost/ton* Annual Cost
Manpower, 20 employees $4.37 $350,000
Power, 210 kWh/h .46 36,800
Water/sewer @ 385 gal/min) .89 70,800
Auxiliary fuel (250,000 gal/yr) 1.19 95,500
Maintenance (2.5% DCC) 1.03 83,100
Overhead (1% DCC) .42 33,250
Residual disposal .94 75,000
Total Cost $9.30 $744,450
*Based on 80,000 ton/yr throughput
A-191
-------
SLUDGE DRYING FACT SHEET 6.2.9
Description - In this process the moisture in the sludge is reduced by evaporation to 8 to 10 percent by the
application of hot air, without combusting the solid materials. For economic reasons, the moisture content of the
sludge must be reduced as much as possible through mechanical means prior to heat drying. The five available heat
treating techniques are flash, rotary, toroidal, multiple hearth and atomizing spray.
Flash drying is the instantaneous vaporization of moisture from solids by introducing the sludge into a hot gas
stream. The system is based on several distinct cycles which can be adjusted for different drying arrangements.
The wet sludge cake is first blended with some previously dried sludge in a mixer to improve pneumatic conveyance.
The blended sludge and hot gases from the furnace at about 1200°F to 1400°F (650 to 760 C) are mixed and fed into
a cage mill in which the mixture is agitated and the water vapor flashed. The residence time in the cage mill is
only a matter of seconds. The dry sludge with eight to ten percent moisture is separated from the spent drying
gases in a cyclone, with part of it being recycled with incoming wet sludge cake and another part being screened
and sent to storage.
A rotary dryer consists of a cylinder which is slightly inclined from the horizontal and revolves at about five to
eight r/min. The inside of the dryer usually is equipped with flights or baffles throughout its length to break
up the sludge. Wet cake is mixed with previously heat dried sludge in a pug mill. The system may include cyclones
for sludge and gas separation, dust collection scrubbers, and a gas incineration step.
The toroidal dryer uses the jet mill principle, which has no moving parts, dries and classifies sludge solids
simultaneously. Dewatered sludge is pumped into a mixer where it is blended with previously dried sludge. The
blended material is fed into a doughnut-shaped dryer, where it comes into contact with heated air at a temperature
of 800 F to 1100 F. The particles are dried and broken up into fine pieces and are carried out of the dryer by
the air stream. The dried, powdered sludge is supplemented with nitrogen and phosphorus and formed into bri-
quettes which are crushed and screened to produce final products.
The multiple hearth furnace is adapted for heat drying of sludge by incorporating fuel burners at the top and
bottom hearths, plus down draft of the gases. The dewatered sludge cake is mixed in a pug mill with previously
dried sludges before entering the furnace. QAt the point of exit from the furnace, the solids temperature is about
100 F, and the gas temperature is about 325 F.
Atomizing drying involves spraying liquid sludge in a vertical tower through which hot gases pass downward. Dust
carried with hot gases is removed by a wet scrubber or dry dust collector. A high-speed centrifugal bowl can also
be used to atomize the liquid sludge into fine particles and to spray them into the top of the drying chamber
where moisture is transferred to the hot gases.
Technology Status - Heat drying of sludge was developed more than 50 years ago; however, it is not widely used.
Application - It is an effective way for ultimate sludge disposal and resource conservation when the end products
are applied on land for agricultural and horticultural uses. Although it is an expensive process, it can become a
viable alternative, if the product can be successfully marketed.
Limitations - Cost and high operator skill.
Typical Equipment/Ho, of Mfrs. - Complete heat drying systems are generally proprietory. The major equipment
includes mixers, furnaces, cyclones, screens, dryers, wet scrubbers, dust collectors, air blowers, heaters,
spraying devices, sludge feed pumps and handling equipment.
Performance - Heat drying destroys most of the bacteria in the sludge. However, undigested heat dried sludge is
susceptible to putrefaction if it is allowed to get wet in thick layers on the ground. Heat drying does not cause
any significant decrease of the heavy metals concentration in the sludge. In general, heat dried sludge contains
nutrients which are only about one-fifth of those contained in chemical fertilizers. Heat dried sludge is there-
fore useful only as a fertilizer supplement and a soil conditioner.
Physical, Chemical and Biological Aids - Heat; nitrogen and phosphorus may be added to increase nutrient values of
the dried sludge.
Residuals generated - All the solids captured in the wet scrubbers and dry solids collectors are recycled and
incorporated in the end products.
Design Criteria - Approximately 1,400 Btu are needed to vaporize one pound of water, based on a thermal efficiency
of 72 percent. Less fuel would be required with additional heat recovery. Chemical scrubbers are used, or chem-
icals are added prior to heat drying. Excessive drying tends to produce a sludge that is dusty or contains many
fine particles, which is less acceptable for marketing, and should be avoided. Het scrubbers and/or solids
collectors are needed. Standby heat drying equipment is needed for continuous operation.
Environmental Impact - Potential for explosion and air pollution if the system is not properly operated and
maintained.
Reference - 213
A-192
-------
SLUDGE DRYING
FACT SHEET 6.2.9
FLOW DIAGRAM -
watered
Sludge
!
Mix
er
*
Dryer
*~
Collector
Screen
Dried
Sludge "~
ENERGY NOTES (4) - Assumptions: Dryer efficiency - 72 percent; product moisture content « 10 percent; power
includes blowers, fans, conveyors; continuous operation.
100,000,000
1,000.000
100,000
7
6
9
4
S
2
PERCENT INPUT SOLIDS CONCENTRATION •
Z2
^
//
W-?£^
5l3£
xy^sssr
/ f 7 v
ELECT I ITY
FUEL
] i B •» I i 4 9 4799 i 349 6799 •
100 1,000 10,000 100,000
ANNUAL DRY SOLIDS PRODUCT - ton/rr
COSTS -
1. City of Houston, production cost unknown, $21/dry ton revenue (1972 F.O.B. Houston).
2. City of Milwaukee, $90/dry ton production, $54/dry ton revenue, $36/dry ton net cost (1975).
3. City of Chicago, $60/dry ton production, $15/dry ton revenue, $45/dry ton net cost (1968).
REFERENCES - 3, 4, 7, 22, 23, 30, 201
A-193
-------
CENTRIFUGAL DEWATERING FACT SHEET 6.3.1.
Description (8) - Centrifuges are used to dewater municipal sludges. They use centrifugal force to increase the
sedimentation rate of sludge solids. The three most common types of units are the solid bowl type, the disc type,
and the basket type.
The solid bowl continuous centrifuge assembly consists of a. bowl and conveyor joined through a planetary gear
system, designed to rotate the bowl and the conveyor at slightly different speeds. The solid cylindrical bowl, or
shell, is supported between two sets of bearings and includes a conical section at one end. This section forms
the dewatering beach over which the helical conveyor screw pushes the sludge solids to outlet ports and then to a
sludge cake discharge hopper. The opposite end of the bowl is fitted with an adjustable outlet weir plate to
regulate the level of the sludge pool in the bowl. The centrate flows through outlet ports either by gravity or
by a centrate pump attached to the shaft at one end of the bowl. Sludge slurry enters the unit through a sta-
tionary feed pipe extending into the hollow shaft of the rotating bowl and passes to a baffled, abrasion-protected
chamber for acceleration before discharge through the feed ports in the rotating conveyor hub into the sludge
pool. Due to the centrifugal forces, the sludge pool takes the form of a concentric annular ring on the inside of
the bowl. Solids settle through this ring to the wall of the bowl where they are picked up by the conveyor scroll.
Separate motor sheaves or a variable speed drive can be used for adjusting the bowl speed for optimum performance.
Bowls and conveyors can be constructed from a large variety of metals and alloys to suit special applications.
For dewatering of wastewater sludges, mild steel or stainless steel normally has been used. Because of the
abrasive nature of many sludges, hardfacing materials are applied to the leading edges and tips of the conveyor
blades, the discharge ports, and other wearing surfaces. Such wearing surfaces may be replaced by welding when
required.
In the continuous concurrent solid bowl centrifuge, incoming sludge is carried by the feed pipe to the end of the
bowl opposite the discharge. Centrate is skimmed off and cake proceeds up beach for removal. As a result,
settled solids are not disturbed by incoming feed.
In the disc centrifuge the incoming stream is distributed between a multitude of narrow channels formed by stacked
conical discs. Suspended particles have only a short distance to settle, so that small and low density particles
are readily collected and discharged continuously through fairly small orifices in the bowl wall. The clarifi-
cation capability and throughput range are high, but sludge concentration is limited by the necessity of dis-
charging through orifices of 0.050 inches to 0.100 inches in diameter. Therefore, it is generally considered a
thickener rather than a dewatering device.
In the basket centrifuge, flow enters the machine at the bottom and is directed toward the outer wall of the
basket. Cake continually builds up within the basket until the centrate, which overflows a weir at the top of the
unit, begins to increase in solids. At that point, feed to the unit is shut off, the machine decelerates, and a
skimmer enters the bowl to remove the liquid layer remaining in the unit. A knife is then moved into the bowl to
cut out the cake which falls out the open bottom of the machine. The unit is a batch device with alternate
charging of feed sludge and discharging of dewatered cake.
Technology Status - Solid bowl and disc centrifuges are in widespread use. Basket centrifuges are fully demon-
strated for small plants, but not widely used.
Applications - Solid bowl and disc types are generally used for dewatering sludge in larger facilities where space
is limited or where sludge incineration is required. Basket type is used primarily for partial dewatering at
small plants. Disc centrifuges are more useful for thickening and clarification than dewatering.
Limitations (7) - Centrifugation requires sturdy foundations because of the vibration and noise that result from
centrifuge operation. Adequate electric power must also be provided since large motors are required. The major
difficulty encountered in the operation of centrifuges has been the disposal of the centrate, which is relatively
high in suspended, nonsettling solids. With disc type units, the feed must be degritted and screened to prevent
pluggage of discharge orifices.
Typical Equipment/Ko. of Mfrs. (10) - Centrifuge/Si Sludge feed pump/7; Solids conveyor/7; Centrate pumps/40.
Performance (8) - Solid bowl centrifuge solids recovery = 50 to 75 percent without chemical addition and 80 to 95
percent with chemical addition. Solids concentration = 15 to 40 percent depending on type of sludge. For basket
centrifuges solids capture = 90 to 97 percent without chemical addition and cake solids concentrations = 9 to 14
percent. Disc centrifuges can dewater a 1 percent sludge to six percent solids concentration.
Design Criteria - Each installation is site specific and dependent upon a manufacturers' product line. Maximum
capacities of about 100 tons/h of dry solids are available in solid bowl units with diameters up to 54 inches and
power requirements up to 175 hp. Disc units are available with capacities up to 400 gal/min of concentrate.
Unit Reliability - Pluggage of discharge orifices is a problem on disc type units if feed to the centrifuge is
stopped, interrupted, or reduced below a minimum value. Wear is a serious problem with solid bowl centrifuges.
Environmental Impact - Centrate is relatively high in suspended, non-settling solids which, if returned to treat-
ment units, could reduce effluent quality from primary settling system. Noise may require some control measures.
References - 3, 7, 8, 10
A-194
-------
CENTRIFUGAL DEWATERING
FACT SHEET 6.3.1
FLOW DIAGRAM -
Differential p=
Speed Gear Box
— -.
~ -
Main Drive Sheave
Chemicals
•for Conditioning
Shutdown
Flush
Centrate
Discharge
ENERGY NOTES - Energy requirements in the form
of electricity can be highly site specific due
to the sizing and type of centrifuges used. For
the cost examples below, an energy usage of
approximately 18,000 kwh/yr/ton of dry solids/d
for lime sludges and 31,500 for biological sludges
are noted.
COSTS - ENR = 2475
Sludge Cake
Discharge
Sludge
Sludge Pump
CONSTRUCTION COST
10
1.0
Design Basis: Construction costs include centrifuges
(solid bowl), with minimum of one spare; sludge pumps
and piping; cake conveyors; internal electrical and
building cost.
Sludge quantity = 4,500 Ib/Mgal at 10 percent solids
for lime sludge and 900 Ib/Mgal at 4 percent for
digested biological sludge.
Operation = 8 h/d
Costs do not include centrate handling.
For biological sludge, cationic polymer cost is based
On 10 Ib/ton dry basis.
Power cost = $0.02/kwh.
- 0.1
0.01
1
„
"
-f'
j me
**""
,--
1 y>ij
S
f
;e
lu<
'
s"
itC
lg
*"
d
EX
rm
tf '
Bic
\\[A
logi
/
a
s
1
31
,. '
^
udge
0.1
1.0
10
Lime Sludge
OPERATION & MAINTENANCE COST
Wastewater Flow, Mgal/d
Digested Biological Sludge
OPERATION & MAINTENANCE COST
°S
VI *-
0001
Total
Pow
enals
Labo
0 1
1 0
001
Q 0 1
I
0001
0 1
REFERENCE - 3
1 0 10
Wastewater Flow, Mgal/d
00001
100
0001
Mate
las
.. -'Labor
-To al
Chem
ca
100
01
0001
0 1
1 0 10
Wastewater Flow, Mgal/d
100
00001
*To convert construction cost to capital cost see Table A-2.
A-195
-------
DRYING BEDS, SLUDGE FACT SHEET 6.3.2
Description - Drying beds are used to dewater sludge both by drainage through the sludge mass and by evaporation
from the surface exposed to the air. Collected filtrate is usually returned to the treatment plant. Drying beds
usually consist of 4 to 9 inches of sand which is placed over 8 to 18 inches of graded gravel or stone. The sand
typically has an effective size of 0.3 to 1.2 mm and a uniformity coefficient of less than 5.0. Gravel is nor-
mally graded from 1/8 to 1.0 inch. Drying beds have underdrains that are spaced from 8 to 20 feet apart. Under-
drain piping is often vitrified clay laid with open joints, has a minimum diameter of 4 inches, and has a minimum
slope of about 1 percent.
Sludge is placed on the beds in an 8 to 12 inch layer. The drying area is partitioned into individual beds,
approximately 20 ft wide by 20 to 100 ft long, of a convenient size so that one or two beds will be filled by a
normal withdrawal of sludge from the digesters. The interior partitions commonly consist of two or three creo-
soted planks, one on top of the other, to a height of 15 to 18 inches, stretching between slots in precast con-
crete posts. The outer boundaries may be of similar construction or earthen embankments for open beds, but
concrete foundation walls are required if the beds are to be covered.
Piping to the sludge beds is generally made of cast iron and designed for a minimum velocity of 2.5 ft/s. It is
arranged to drain into the beds and provisions are made to flush the lines and to prevent freezing in cold cli-
mates. Distribution boxes are provided to divert sludge flow to the selected bed. Splash plates are used at the
sludge inlets to distribute the sludge over the bed and to prevent erosion of the sand.
Sludge can be removed from the drying bed after it has drained and dried sufficiently to be spadable. Sludge
removal is accomplished by manual shoveling into wheelbarrows or trucks or by a scraper or front-end loader.
Provisions should be made for driving a truck onto or along the bed to facilitate loading. Mechanical devices can
remove sludges of 20 to 30 percent solids while cakes of 30 to 40 percent generally require hand removal.
Paved drying beds with limited drainage systems permit the use of mechanical equipment for cleaning. Field
experience indicates that the use of paved drying beds results in shorter drying times as well as more economical
operation when compared with conventional sandbeds because, as indicated above, the use of mechanical equipment
for cleaning permits the removal of sludge with a higher moisture content than in the case of hand cleaning.
Paved beds have worked successfully with anaerobically digested sludges but are less desirable than sandbeds for
aerobically digested activated sludge.
Common Modifications - Sandbeds can be enclosed by glass. Glass enclosures protect the drying sludge from rain,
control odors and insects, reduce the drying periods during cold weather, and can improve the appearance of a
wastewater treatment plant.
Wedge wire drying beds have been used successfully in England. This approach prevents the rising of water by
capillary action through the media and the construction lends itself well to mechanical cleaning. The first
United States installations have been made at Rollinsford, New Hampshire, and in Florida. It is possible, in
small plants, to place the entire dewatering bed in a tiltable unit from which sludge may be removed merely by
tilting the entire unit mechanically.
Technology Status - Over 6,000 plants use open or covered sandbeds.
Applications - Sandbeds are generally used to dewater sludges in small plants. They require little operator
attention or skill.
Limitations - Air drying is normally restricted to well digested or stabilized sludge, because raw sludge is
odorous, attracts insects, and does not dry satisfactorily when applied at reasonable depths. Oil and grease clog
sandbed pores and thereby seriously retard drainage. The design and use of drying beds are affected by weather
conditions, sludge characteristics, land values and proximity of residences. Operation is severely restricted
during periods of prolonged freezing and rain.
Typical Equipment/No- of Mfrs.(83) - Front-end loader/16; Scraper/42.
Performance - A cake of 40 to 45 percent solids may be achieved in two to six weeks in good weather and with a
well digested waste activated, primary or mixed sludge. With chemical conditioning, dewatering time may be
reduced by 50 percent or more. Solids contents of 85 to 90 percent have been achieved on sand beds, but normally
the times required are impractical.
Design Criteria- Open bed area = 1.0 to 1.5 ft /capita (primary digested sludge); 1.75 to 2.5 ft /capita (pri-
mary and activated sludge); 2.0 to 2.5 ft /capita (alum or iron precipitated sludge). Experience has shown that
enclosed beds require 60 to 75 percent of the open bed area. Solids loading rates vary from 10 to 28 Ib/ft /yr
for open beds and 12 to 40 Ib/ft /yr for closed beds. Sludge beds should be located at least 200 ft from dwell-
ings to avoid odor complaints due to poorly digested sludges.
Environmental Impact - Land requirements are large. Odors can be a problem with poorly digested sludges and in-
adequate buffer zone areas.
References - 3, 7, 8, 22, 83
A-196
-------
DRYING BEDS, SLUDGE
FACT SHEET 6.3.2
FLOW DIAGRAM -
sludge
3-m coarse sand
3-in fine gravel
3-in medium grave!
3 to 6 irt coarse gravel
- Pipe column foi
glass-over
2 in coarse sand
n underdram laid
vith open joints
ENERGY NOTES (4) - Em = E , . . . + E , , + E . (when required)
T mechanical scraping sand replacement pumping
E is estimated to be 3.2 X 10 Btu/yr/Mgal/d plant flow @ 900 Ib dry splids/Mgal plant flow.
E is estimated to be 10 percent of the mechanical scraping or .32 X 10 Btu/Mgal/d plant flow.
_ 1140 (Mgal/d X TDK)
pumping Wire to Water Efficiency
With a sludge flow of 0.5 X 10 gal/d, a TDK of 40 ft and a wire-to-water efficiency of 60 percent, the pumping
energy requirement would be 38,000 kwh/yr.
COSTS - Service Life: 20 years. ENR = 2475
1. Construction costs include: sand beds, sludge inlets, underdrains, cell dividers, sludge piping, underdrain
return, and other structural elements of the beds. All costs are in mid-1976 dollars.
2. Bed loading: 900 Ib of sludge/Mgal; 20 Ib/ft /yr.
Adjustment Factor - To adjust costs for bed loading rates, sludge quantities, or characteristics, enter curve at
effective flow (Q ).
_ New Design Sludge Mass 20 Ib/ft /yr
QE ~ ^DESIGN 900 Ib/Mgal New Design Bed Loading
CONSTRUCTION COST
10
OPERATION & MAINTENANCE COST
1 0
0 1
001
1 0
D 0 1
1 0 10
Wastewaler Flow Mgal/d
0001
Labo
,M
rials
Total, f
0 1
001
0001
01
1 0 10
Wastewater how, Mgal/d
100
00001
REFERENCES -3,4
*To convert construction cost to capital cost see Table A-2.
A-197
-------
FILTER, BELT FACT SHEET 6.3.:
Description (8) - Belt filters consist of an endless filter belt that runs over a drive and guide roller at each
end like a conveyor belt. The upper side of the filter belt is supported by several rollers. Above the filter
belt is a press belt that runs in the same direction and at the same speed; its drive roller is coupled with the
drive roller of the filter belt. The press belt can be pressed on the filter belt by means of a pressure roller
system whose rollers can be individually adjusted horizontally and vertically. The sludge to be dewatered is fed
on the upper face of the filter belt and is continuously dewatered between the filter and press belts. After
having passed the pressure zone, further dewatering in a reasonable time cannot be achieved by only applying
static pressures. However, a superimposition of shear forces can effect this further dewatering. The supporting
rollers of the filter belt and the pressure rollers of the pressure belt are adjusted in such a way that the belts
and the sludge between them describe an S-shaped curve. Thus, there is a parallel displacement of the belts
relative to each other due to the differences in the radii. After further dewatering in the shear zone, the sludge
is removed by a scraper.
Some units consist of two stages where the initial draining zone is on the top level followed by an additional
lower section wherein pressing and shearing occur. A significant feature of the belt filter press is that it
employs a coarse mesh, relatively open weave, metal medium fabric. This is feasible because of the rapid and
complete cake formation obtainable when proper flocculation is achieved. Belt filters do not need vacuum systems
and do not have the sludge pickup problem occasionally experienced with rotary vacuum filters. The belt filter
press system includes auxiliaries such as polymer solution preparation equipment and automatic process controls.
Common Modifications - Some belt filters include the added feature of vacuum boxes in the free drainage zone.
About 6 inches Hg vacuum are applied to obtain higher cake solids. A "second generation" of belt filters have
extended shearing or pressure stages that produce substantial increases in cake solids, but are more costly.
Technology Status (8, 118) - 67 units were installed in Europe as of 1971. At that time, several units were also
being installed in the United States. In 1975 a belt filter press was installed in a 0.9 Mgal/d (average) plant in
Medford Township, NJ.
Applications - Hard-to-dewater sludges can be handled more readily. Low cake moisture permits incineration of
primary/secondary sludge combinations without auxiliary fuel. A large filtration area can be installed in a
minimum of floor area.
Limitations - To avoid penetration of the filter belt by sludge, it is usually necessary to coagulate the sludge
(generally with synthetic, high polymeric flocculants).
Typical Equipment/No, of Mfrs.dO, 23) - Belt filter/7; Chemical feed equipment/25; Cake conveyors/7; Sludge
Pumps/7
Performance (206) - The following table shows performance achieved in pilot studies:
Feed Solids Secondary:Primary Polymer Pressure Cake Solids Solids Capacity
% Ratio dosage (1) Ib/in g(2) % Recovery % (3)
9.5 100% primary 1.6 100 41 97-99 2706
8.5 1:5 2.4 100 38 97-99 2706
7.5 1:2 2.7 25-100 33-38 95-97 1485
6.8 1:1 2.9 25 31 95 898
6.5 2:1 3.1 25 31 95 858
6.1 3:1 4.1 25 28 90-95 605
5.5 100% secondary 5.5 25 25 95 546
(1) pounds per ton dry solids
(2) pounds per square inch, gauge
(3) pound dry solids per hour per meter
In addition, reports from the Medford, NJ plant indicate that belt filter solids capture of 98 percent or more can
be achieved with filtrate TSS under 100 p/m. Sludge is dewatered from 96 to 97 percent moisture to 81 to 83 per-
cent moisture. Polymer addition has been 5 to 6 gal/ton. (118)
Design Criteria (117) - The following loadings are based on active belt area:
Sludge Loading Dry Solids Loading
Sludge Type gal/ft /h Ib/ft /h
Raw Primary 27-34 13.5-17
Digested Primary 20-24 20.5-24
Digested Mixed/Secondary 13-17 6.7-8.4
Environmental Impact - Relatively high chemical and energy requirements.
Unit Reliability (118) - Almost one year of trouble-free operation had been achieved on the Medford, NJ plant as of
October, 1977. The two meter wide filter belt showed only slight discoloration and remained clean and free from
blinding or other'signs of wear.
References - 8, 10, 23, 117, 118, 125, 206
A-198
-------
FILTER, BELT
FACT SHEET 6,3.3
FLOW DIAGRAM -
Sludge Inlet Press Belt
Press Rolls Drive Roll
Cake Discharge
Drive Roll
Filtrate
ENERGY NOTES (125) -
Plant Loading
(lb dry solids/d)
16,000
40,000
66,000
Machine Capacity
(lb dry solids/d)
24,000
60,000
99,000
Energy Usage
kwh/ton dry solids
13
COSTS - 1977 dollars; ENR Index = 2577
Type of sludge: Primary and secondary (anaerobically digested) - 5 percent solids concentration.
Sludge production: 7 d/wk
Dewatering operation: 7 d/wk; 16 h/d
Construction costs include belt filter press, sludge feed pumps, polymer pumps, and control panels.
Labor cost: $15/manhour. Power cost: $0.02/kWh.
Plant Sludge Loading
(lb dry solids/d)
16,000
40,000
66,000
Construction
Cost
$ 97,000
120,000
165,000
Power
Cost
$ 800/yr
1200/yr
1700/yr
Labor
Cost
$ll,000/yr
11,000/yr
11,000/yr
Maintenance
Cost
$1400/yr
1700/yr
2300/yr
REFERENCES - 8, 125
*To convert construction cost to capital cost see Table A-2.
A-199
-------
FILTER PRESS, DIAPHRAGM FACT SHEET 6.3.4
Description - The diaphragm filter press is a recent extension of filter press technology to increase the through-
put of a press and provide a higher solids content in wastewater filter cake. (See Fact Sheet 6.3.5 for dis-
cussion of conventional filter presses.) The press makes use of a rubber diaphragm with pressurized water to
provide a high pressure on the partially dewatered sludge cake in the press after conventional dewatering methods
have been used.
This diaphragm provides the support for the filter cloth on one side of the press cavity. Filtration of the
sludge is accomplished by charging the chambers of the press with sludge under pump pressure in the conventional
manner, but at a generally lower pressure, and allowing a cake to develop. The time alloted to this cycle is
dependent upon the characteristics of the sludge, but is scheduled to continue only as long as high filtration
rates are in progress. This cycle usually is in the 10 to 30 minute range. The pump pressurizing system is then
turned off, and water pressure is applied inside the diaphragm. This pressure, in the 200 psi range, applies a
uniform pressure over the cake and further reduces the water content. The squeezing cycle has been shown to
substantially reduce the overall cycle time for the press, yet produces a low moisture content cake. The filter
cake produced is thinner than in the conventional press but has a uniform moisture content in contrast to the
conventional press. The reduction in operating time for the sludge pumps is reported to substantially reduce wear
and the required maintenance. The pressurized water for the diaphragm actuation is a closed recycle system;
therefore, components operate under predictable conditions and no effluent is produced. Diaphragm presses are
designed to make use of a number of automation features to reduce labor and recycle time.
Common Modifications - Opening of the filter press to allow simultaneous discharge of filter cake from all cav-
ities. Rejection of the sludge cake by physical movement of the filter cloth by vibration or actual movement of
the cloth in a forced rejection mode by partial withdrawal of the filter cloth loop. Automatic washing of filter
cloths at each cycle or as conditions dictate. Air purging of feed and filtrate lines between cycles. Full
automation of press operation.
Technology Status - The diaphragm filter press originates as Japanese or European technology. Several hundred
presses were reported to be in operation in Japan's wastewater industry. The press is new to the United States
and is being demonstrated by the use of portable pilot units. Fourteen full-scale units are to be scheduled for
installation in 1979.
Applications - Dewatering of a wide variety of wastewater sludges to a high level of solids content. Production
of an auto-combustible filter cake. Used where a large filtration area is required in a minimum of floor area.
Limitations - Relatively high operator skill is required. Life of filter cloths and diaphragms is limited.
Moisture content of sludge highly dependent upon proper sludge conditioning.
Typical Equipment/No- of Mfrs. (148) - Diaphragm filter presses/2. (10) - Sludge pumps/7; cake conveyors/7;
sludge conditioning tanks/3.
Performance (210) - Pilot test runs on full scale diaphragm presses using a 2:1 mix of secondary to primary sludge
has shown cake solids in the 34 to 42 percent range. Lime addition at 12 to 25 percent and Fed at 4 to 8.5
percent were used as a chemical sludge conditioner. Cycle times ranged from 5 to 20 minutes pumping and 8 to 30
minutes squeeze.
Chemicals Required - For sludge conditioning, when necessary, lime, FeCl and other materials found by test to be
suitable for the sludge being processed.
2
Design Criteria - Filter areas = 5 to 40 ft /chamber, cake thickness 1/2 to 3/4 inch, sludge yield 0.4 to 0.8
Ib/ft of filter area, total cycle time 20 to 50 minutes.
Process Reliability - Reliability is expected to be high and similar to that of conventional filter presses.
Process expected to show greater tolerance to impact of hard-to-dewater sludges.
Environmental Impact - Consistent production of a high solids cake, even with hard-to-dewater sludge, can be
expected to aid in an environmentally optimum disposal of sludge.
References - 10, 148, 210
A-200
-------
FILTER PRESS, DIAPHRAGM
FACT SHEET 6.3.4
FLOW DIAGRAM -
Cake
Drain
-Conditioning Tank
ENERGY NOTES (210) - Energy requirements per dry ton for the process based on the assumptions below are: 37
cWh/ton for press operation + 29.7 kWh/ton for operation of the lime and Fed systems, sludge pumping, sludge
conditioning equipment and the cake conveyors, resulting in a total power requirement of 66.7 kWh/ton.
COSTS (210) - A cost estimate has been derived for use of a diaphragm filter press in a large multiple press
installation with a sludge cake production of 250 dry ton/d. Sludge was assumed to be a mix of 2:1 secondary to
primary with a feed solids of 5 percent. Sludge conditioning was assumed to be lime at 20 percent and FeCl at 7
percent dry sludge solids. Lime cost was assumed at $44/ton and FeCl at $130/ton. Pricing is based on the
largest size presses available. The total number includes one spare. The capital cost (1978 dollars) includes
the chemical feed system, sludge feed pumps, dewatering unit with all necessary accessories and a conveyor system
to transport cake to the next process. The total installation cost was obtained by utilizing a multiplication
factor of 3 which includes installation, piping, utilities, building and engineering. Labor is assumed at
$21,000/manyear. ENR Index = 2577
Cost Summary
Capital Cost
Lime System
FeCl3 System
Conveyors
Total
Annual Costs
Amortization at 9%
Chemicals
Power at 66.7 kWh/ton and $0.04/kWh
Water 12 x 10 gallons
Labor - Operation
Maintenance -
Cloth and diaphragm replacement-materials
Labor replacement
Equipment maintenance at 2% of purchase cost
$19,500,000
1,000,000
500,000
2,000,000
$23,000,000
2,070,000
1,633,000
243,000
6,400
504,000
312,000
31,500
153,000
Total annual costs $ 4,953,000
Unit cost/dry ton of sludge cake $ 54.28
REFERENCE - 210
To convert construction cost to capital cost see Table A-2.
A-201
-------
CONVENTIONAL FILTER PRESS FACT SHEET 6.3.5
Description - The conventional filter press for dewatering wastewater sludges is the recessed plate press. This
press consists of vertical recessed plates up to 5 ft in diameter (or 5 ft on a side, if square) which are held
rigidly in a frame and which are pressed together between a fixed and moving end. On the face of each individual
plate is mounted a filter cloth. The sludge is fed into the press at pressures up to 225 Ib/in g and passes
through feed holes in the trays along the length of the press. The water passes through the cloth, while the
solids are retained and form a cake on the surface of the cloth. Sludge feeding is stopped when the cavities or
chambers between the plates are completely filled. Drainage ports are provided at the bottom of each press
chamber. The filtrate is collected in these, taken to the end of the press, and discharged to a common drain. At
the commencement of a processing cycle, the drainage from a large press can be in the order of 2,000 to 3,000
gallons per hour. This rate falls rapidly to about 500 gallons per hour as the cake begins formation and, when the
cake completely fills the chamber, the rate is virtually nothing. The dewatering step is completed when the
filtrate is near zero. At this point, the pump feeding sludge to the press is stopped, and any back pressure in
the piping is released through the bypass valve. The electrical closing gear is then operated to open the press.
The individual plates are next moved in turn over the gap between the plates and the moving end. This allows the
filter cakes to fall out. The plate moving step can be either manual or automatic. When all the plates have been
moved and the cakes released, the complete pack of plates is then pushed back by the moving end and closed by the
electrical closing gear. The valve to the press is than opened, the sludge feed pump started, and the next
dewatering cycle commences. Thus, a cycle includes the time required for filling, pressing, cake removal, media
washing, and press closing.
A monofilament filter media is now used which, unlike multifilament filter cloth, resists blinding in service.
Many systems utilize an efficient precoat system which deposits a protective layer of porous material (fly ash,
cement kiln dust, buffing dust) on the filter media to prevent blinding and to facilitate cake release.
2
Whilj in; Sludge Feed Rate = approximately 2 Ib/cycle/ft (dry solids basis).
Unit Reliability - Pressure filter plate warpage has been a major problem. Plate gasket deterioration (sometimes
caused by plate warpage) has also been a problem requiring maintenance.
References - 8, 10, 64
A-202
-------
CONVENTIONAL FILTER PRESS
FACT SHEET 6.3.5
LOW DIAGRAM -
Cake
SNERGY NOTES (4) - Power consumption based on con-
tinuous operation, 225 Ib/in operating pressure.
Curve includes feed pump (hydraulically driven,
positive displacement piston pump), opening and
closing mechanism.
in7
in6
105
1
T
I
'iltei
Preys
?
nfluent Solids <
(
i
t'
.
ii;2
^
s
Filtrate
'*>
3%;
7
s
/
Drai
j^i
n
, ^
W\
S
/
s .
10
100
COSTS (3) - ENR Index = 2475; Service life = 15 years.
Filter Press Volume, ft
1000 10,000
3
1. Construction cost for biological sludge includes filter presses, pressure pumps, conveyor equipment, chenical
feed and storage facilities, conditioning tanks, sludge storage tanks, and building.
2. Sludge loading: digested primary + secondary = 900 Ib/Mgal @ 2.5%
3. Cake characteristics: density = 68 Ib/ft ; solids content = 40%.
4. Operations: For 0.1 to 1 Mgal/d plant = 20 cycles/wk
For 1 to 10 Mgal/d plant = 48 cycles/wk
For 10 to 100 Mgal/d plant = 84 cycles/wk
5. Conditioning chemicals: FeCl = 35 Ib/Mgal; CaO = 90 Ib/Mgal
6. For filter press costs for lime sludge, please refer to reference 3.
Adjustment Factor - To develop cost for sludge quantities, concentration, characteristics or cycles per week dif-
ferent than those used to develop these curves, enter curve at effective flow (Q ).
Q = Q ~Tr New Design New Design New Design Cycle
Sludge Mass X Cycles Per Week X Time
900 Ib/Mgal Or.ig.inal Desinn
Cycles Per Week
2 hours
100
10
1
0
10
0.1
CONSTRUCTION COST:
DigMted
Biological Sludgt
f I
i i
X u
! i
01
10 10
Wastewater Flow. Mgal/d
OOOI
0.01
001
0.001
0.0001
01
10 10
Wastewater Flow, Mgal/d
REFERENCES - Curves derived from references 3 and 4.
*To convert construction cost to capital cost see Table A-2.
A-203
-------
THICKENING, DISSOLVED AIR FLOTATION
FACT SHEET 6.3.6
Description and Common Modifications - In a Dissolved Air Flotation (DAF) system, a recycled subnatant flow is
pressurized from 30 to 70 Ib/in g and then saturated with air in a pressure tank. The pressurized effluent is
then mixed with the influent sludge and subsequently released into the flotation tank. The excess dissolved air
then separates from solution, which is now under atmospheric pressure, and the minute {average diameter 80 microns)
rising gas bubbles attach themselves to particles which form the floating sludge blanket. The thickened blanket is
skimmed off and pumped to the downstream sludge handling facilities while the subnatant is returned to the plant.
Polyelectrolytes are frequently used as flotation aids, to enhance performance and create a thicker sludge blanket.
A description of the DAF process in general is presented in Fact Sheet 3.1.6.
Technology Status - DAF is the most common form of flotation thickening in use in the United States and has been
used for many years to thicken waste activated sludges, and to a lesser degree to thicken combined sludges. DAF
has widespread industrial wastewater applications.
Applications - The use of air flotation is limited primarily to thickening of sludges prior to dewatering or
digestion. Used in this way, the efficiency of the subsequent dewatering units can be increased and the volume of
supernatant from the subsequent digestion units can be decreased. Existing air flotation thickening units can be
upgraded by the optimization of process variables, and by the utilization of polyelectrolytes. Air flotation
thickening is best applied to waste activated sludge. With this process, it is possible to thicken the sludge to
6 percent solids, while the maximum concentration attainable by gravity thickening without chemical addition is 2
to 3 percent solids. The DAF process can also be applied to mixtures of primary and waste activated sludge. DAF
also maintains the sludge in aerobic condition and potentially has a better solids capture than gravity thick-
ening. There is some evidence that activated sludges from pure oxygen systems are more amenable to flotation
thickening than sludges from conventional systems.
Limitations - DAF has high operating costs (primarily for power for aeration and chemicals) and is therefore
generally limited to waste activated sludges. The variability of sludge characteristics requires that some pilot
work be done prior to design of a DAF system.
Typical Equipment/No, of Mfrs. (23) - Dissolved air flotation units/24; Air compressors/8.
Performance (26) - A summary of data from various air flotation units indicates that solids recovery ranges from
83 to 99 percent at solids loading rates of 7 to 48 Ib/ft /d.
A summary of operating data from 14 sewage treatment plants (8) is as follows: Influent suspended solids 3,000 to
20,000 mg/1 (median 7,300), supernatant suspended solids 31 to 460 mg/1 (median 144), suspended solids removal 94
to 99+ percent (median 98.7), flfiat solids 2.8 to 12.4 percent (median 5.0), loading 1.3 to 7.7 Ib/h/ft (median
3.1), flow 0.4 to 1.8 gal/min/ft (median 1.0).
Chemicals Required - Flotation aids (generally polyelectrolytes) are usually used to enhance performance.
Residuals Generated - Supernatant (effluent) quality:
treatment plant.
Approximately 150 mg/1 SS, returned to mainstream of the
Design Criteria - Pressure 30 to 70 Ib/in g; effluent recycle ratio 30 to 150 percent of influent flow; air to
solids ratio 0.02 Ib air/lb solids; solids loading 5 to 55 Ib/ft /d (depending on sludge type and whether flota-
tion aids are used); polyelectrolyte addition (when used) 5 to 10 Ib/ton of dry solids; solids capture 70 to 98+
percent; total solids* unthickened sludge 0.3 to 2.0 percent, thickened solids 3 to 12 percent; hydraulic loading
0.4 to 2.0 gal/min/ft .
Sludge Type
Primary + WAS
Primary + (WAS + Fed )
(Primary + FeCl ) + WAS
WAS
WAS + FeCl3
Digested Primary + WAS
Digested Primary +
Tertiary, Alum
(WAS + FeCl )
Feed Solids
Concentration
(Percent)
2.0
1.5
1.8
1.0
1.0
4.0
4.0
1.0
Typical Loading Rate
Without Polymer
(Ib/sq ft/day)
20
15
15
10
10
20
15
8
Typical Loading Rate
with Polymer
(Ib/sq ft/day)
60
45
45
30
30
60
45
24
Float Solids
Concentration
(Percent)
5.5
3.5
4.0
3.0
2.5
10.0
8.0
2.0
Reliability - DAF systems are reliable from a mechanical standpoint. Variations in sludge characteristics can
affect process (treatment) reliability, and may require operator attention.
Environmental Impact - Requires less land than gravity thickeners. A subnatant stream is returned to the head of
the treatment plant, although it should be compatible with other wastewater. The air released to the atmosphere
may strip volatile organic material from the sludge. The volume of sludge requiring ultimate disposal may be
reduced, although its composition will be altered if chemical flotation aids are used. The air compressors will
require shielding to control the noise generated.
References - 3, 7, 8, 23, 26, 95, 111
A-204
-------
THICKENING, DISSOLVED AIR FLOTATION
FACT SHEET 6.3.6
FLOW DIAGRAM -
SKIMMER MECHANISM
PRESSURE TANK
AIR
SUBNATANT
ENERGY NOTES (4) - See table in design section
of 6.3.6 for typical loading rates.
10
o 10-
10
10
COSTS (3) -Assumptions:
100 1,000
Surface Area, sq ft
in ooo
T. Construction costs include: flotation chamber (2-h detention based on sludge flow); pressure tanks
(60 Ib/in g); recycle pumps (100% recycle).
2. Costs for thickening of, secondary sludge only: 820 Ib/Mgal.
3. Loading rate = 2 Ib/ft /h
4. Operating hours: 0.1 and 1 Mgal/d = 40 h/wk; 10 Mgal/d = 100 h/wk; 100 Mgal/d = 168 h/wk.
Adjustment Factor: To determine costs at loading rates or sludge quantities other than above, enter curve effec-
tive flow Q. 2
g _ Q E x 2 Ib/ft /h X New Design Sludge Mass
E DESIGN New Design Mass Loading Rate 820 Ib/d/Mgal
CONSTRUCTION COST
10 l-L^UU 01
OPERATION & MAINTENANCE COST
01
001
0 1
REFERENCES - 3, 4, 26
D 0 01
0001
1 0 10
Wastewater Flow Mgal/d
100
00001
Total
Labor.
Materials
01
1 0 10
Wastewater Flow, Mgal/d
100
*To convert construction cost to capital cost see Table A-2.
A-205
-------
THICKENING, GRAVITY FACT SHEET 6.3.7
Description - Thickening of sludge consists of the removal of supernatant, thereby reducing the volume of sludge
that requires disposal or further treatment. Gravity thickening takes advantage of the difference in specific
gravity between the solids and water.
A gravity thickener normally consists of two truss-type steel scraper arms mounted on a hollow pipe shaft keyed to
a motorized hoist mechanism. A truss-type bridge is fastened to the tank walls or to steel or concrete columns.
The bridge spans the tank, and supports the entire mechanism. The thickener resembles a conventional circular
clarifier with the exception of having a greater bottom slope. Sludge enters at the middle of the thickener and
the solids settle into a sludge blanket at the bottom. The concentrated sludge is very gently agitated by the
moving rake which dislodges gas bubbles and prevents bridging of the sludge solids. It also keeps the sludge
moving toward the center well from which it is removed. Supernatant liquor passes over an effluent weir around
the circumference of the thickener. It has been shown that in the operation of gravity thickeners it is desirable
to keep a sufficiently high flow of fresh liquid entering the concentrator to prevent septic conditions and
resulting odors from developing.
Gravity thickening is characterized by zone settling. The four basic settling zones in a thickener are:
.The clarification zone at the top containing the relatively clear supernatant.
.The hindered settling zone where the suspension moves downward at a constant rate and a layer of settled solids
begins building from the bottom of the zone.
.The transition zone characterized by a decreasing solids settling rate.
-The compression zone where consolidation of sludge results solely from liquid being forced upward around the
solids.
Common Modifications - Tanks can be square or round, with the round variety being much more prevalent. Tanks can
be manufactured of concrete or steel. Chemicals can be added to aid in the sludge dewatering.
Technology Status - Has been in wide use for many years.
Typical Equipment/No, of Mfrs. (23) - Sedimentation Equipment/28; Chemical feed equipment/25.
Applications - Used to thicken primary, secondary, and digested sludges.
Limitations - Does not perform satisfactorily on most waste activated, mixed primary-waste activated, and alum or
iron sludges. Is highly dependent on the dewaterability of the sludges being treated.
Performance - (No chemical conditioning)
Solids Surface Thickened Sludge
Loading Solids
Type of Sludge (Ib/d/ft ) Concentration (%)
Primary 20 to 30 8 to 10
Waste Activated 5 to 6 2.5 to 3
Trickling filter 8 to 10 7 to 9
Limed tertiary 60 12 to 15
Primary and activated 6 to 10 4 to 7
Primary and trickling filter 10 to 12 7 to 9
Limed primary 20 to 25 7 to 12
Chemicals Required - Lime (CaO) and/or polymers may be added to aid in the dewatering and settling of the sludge.
Chlorine can be added to prevent septicity.
Residuals Generated - Supernatant volume is directly related to the increase in solids concentration in the
thickener. The supernatant will contain varying amounts of solids, ranging from tens to hundreds of milligrams
per liter.
Design Criteria - See "Performance." Detentions of one to three days are usually used. Sludge blankets of at
least three feet are common. Side water depths of at least ten feet are general practice.
Unit Process Reliability - Gravity thickeners are mechanically reliable, but are greatly affected by the quality
of sludge received. Therefore, they may be upset due to a radical change in the raw wastewater or digested sludge
quality.
Environmental Impact - Requires relatively little use of land. The supernatant will need disposal. This can be
accomplished by recycling it to the head end of the plant for further treatment. Odor problems frequently result
from septic conditions.
References - 8, 26, 34
A-206
-------
THICKENING, GRAVITY
FACT SHEET 6.3.7
FLOW
Influent
Hopper Plow
Under- Scraper Blades
flow
ENERGY NOTES - Assumptions:
Design basis included in "Performance".
COSTS -Assumptions: ENR Index = 2475
1. Construction costs include thickener and
all related mechanical equipment. Pumps
are not included.
2. Costs are based on thickening of secondary
sludge (820 Ib/Mgal; loading = 6 Ib/ft /d).
See adjustment factors for other sludge
loadings.
3. O&M costs do not include polymer addition.
Adjustment Factor: To adjust costs for alter-
native sludge quantities, concentrations, and
thickening properties, enter curves at effective
flow
-------
CENTRIFUGAL THICKENING
FACT SHEET 6.3.3
Description (8) - Centrifuges may be used to thicken municipal sludges. They use centrifugal force to increase the
sedimentation rate of sludge solids. The three most common types of units are the continuous solid bowl type, the
disc type, and the basket type. Refer to Fact Sheet No. 6.3.1 for unit descriptions.
Technology Status (8) - There has been limited use of centrifuges for thickening excess activated sludges (EAS).
Field trials have been conducted at two facilities. Disc type units have been selected for three treatment plants.
Applications (8) - Centrifuges may be used for thickening of excess activated sludge where space limitations or
sludge characteristics make other methods unsuitable. Further, if a particular sludge can be effectively thickened
by gravity or by flotation thickening without chemicals, centrifuge thickening is not economically feasible.
Limitations (8) - Centrifugal thickening processes can have significant maintenance and power costs. Adequate
chemical conditioning may be required in order to achieve 90 percent solids capture and 4 percent solids concen-
tration with activated sludge in a bowl type unit. Disc type units require prescreening to prevent pluggage of
discharge nozzles, especially if flow is interrupted or reduced. Rotating parts of disc units must be manually
cleaned every two weeks. (144)
Typical Equipment/No, of Mfrs. - See Fact Sheet No. 6.3.1.
Performance (8) - Typical performance data for the disc, basket, and solid bowl centrifuges when they are employed
in the thickening of EAS, are presented in the following table. Note that chemical addition is not always required.
In general, underflow solids concentration from disc units is lower than from solid bowl units (3 to 5 percent
versus 5 to 7 percent). (144).
Type of Sludge
Centrifuge
Type
Capacity
(gal/min)
Feed Solids
Underflow
Solids
Solids
Recovery
Polymer
Requirement
(Ib/ton)
EAS
EAS
EAS (after Roughing
Filter)
EAS (after Roughing
Filter)
EAS
EAS
EAS
EAS
Disc
Disc
Disc
Disc
Basket
Solid Bowl
Solid Bowl
Solid Bowl
150
400
50-80
60-270
33-70
10-12
75-100
110-160
0.75-1.0
0.7
0.7
0.7
1.5
0.44-0.78
0.5-0.7
5-5.5
4.0
5-7
6.1
9-10
9-13
5-7
5-8
90+
80
93-87
97-80
90-70
90
90-80
65
85
90
95
None
None
None
None
None
None
None
Less than
5-10
10-15
Design Criteria - See Fact Sheet No. 6.3.1. Maximum available capacity per unit is 500 to 600 gal/min for disc
units and 400 gal/min for solid bowl units. (144,145)
Unit Reliability - Pluggage of discharge orifices is a problem on disc type units if feed to the centrifuge is
stopped, interrupted, or reduced below a minimum value.
Environmental Impact - For some sludges, odor controls may be required. Noise control is always required.
References - 8, 144, 145
A-208
-------
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udge
AC
EET 6.3.8
-------
VACUUM FILTRATION, SLUDGE FACT SHEET 6.3,9
Description (8) - Vacuum filters are used to dewater sludges so as to produce a cake having the physical handling
characteristics and moisture contents required for subsequent processing. A rotary vacuum filter consists of a
cylindrical drum rotating partially submerged in a vat or pan of conditioned sludge. The drum is divided radially
into a number of sections, which are connected through internal piping to ports in a valve body (plate) at the
hub. This plate rotates in contact with a fixed valve plate with similar ports, which are connected to a vacuum
supply, a compressed air supply, and an atmospheric vent. As the drum rotates each section is thus connected to
the appropriate service. Various operating zones are encountered during a complete revolution of the drum. In
the pickup or form section, vacuum is applied to draw liquid through the filter covering (media) and form a cake
of partially dewatered sludge. As the drum rotates the cake emerges from the liquid sludge pool, while suction is
still maintained to promote further dewatering. A lower level of vacuum often exists in the cake drying zone. If
the cake tends to adhere to the media, a scraper blade may be provided to assist removal.
The three principal types of rotary vacuum filters are the drum type, coil type, and the belt type. The
filters differ primarily in the type of covering used and the cake discharge mechanism employed. Cloth media are
used on drum and belt types while stainless steel springs are used on the coil type. Infrequently, a metal media
is used on belt types. The drum filter also differs from the other two in that the cloth covering does not leave
the drum but is washed in place, when necessary. The design of the drum filter provides considerable latitude in
the amount of cycle time devoted to cake formation, washing, and dewatering; while it minimizes inactive time.
A variation of the conventional drum filter is the top feed drum filter. In this case, sludge is fed to the
vacuum filter through a hopper located above the filter. The potential advantages are that gravity aids in cake
formation; capital costs may be lower since the feed hopper is smaller and no sludge agitator and related drive
equipment are required; and "blinding" of the media may be reduced.
The coil type vacuum filter uses two layers of stainless steel coils arranged in corduroy fashion around the
drum. After a dewatering cycle, the two layers of springs leave the drum and are separated from each other so
that the cake is lifted off the lower layer of springs and discharged from the upper layer. Cake release is
essentially free of problems. The coils are then washed and reapplied to the drum. The coil filter has been and
is widely used for all types of sludge. However, sludge with particles that are both extremely fine and resistant
to flocculation dewater poorly on coil filters.
Media on the belt type filter leaves the drum surface at the end of the drying zone and passes over a small
diameter discharge roll to facilitate cake discharge. Washing of the media next occurs before it returns to the
drum and to the vat for another cycle. This type filter normally has a small diameter curved bar between the
point where the belt leaves the drum and the discharge roll which aids in maintaining belt dimensional stability.
In practice it is frequently used to insure adequate cake discharge.
A great many types of filter media are available for the belt and drum filters. There is some question
whether increases in yield due to operating vacuums greater than 15 inches of mercury are justifiable. The cost
of a greater filter area must be balanced against the higher power costs for higher vacuums. An increase from 15
to 20 inches of vacuum is reported to have provided about 10 percent greater yield in three full-scale installa-
tions.
Common Modifications - Chemical conditioning is often employed to agglomerate a large number of small particles.
It is almost universally applied with mixed sludges.
Technology Status - Is the most common method of mechanical sludge dewatering utilized in the United States.
Applications - Generally used in larger facilities where space is limited, or when incineration is necessary for
maximum volume reduction.
Limitations - Relatively high operating skill required. Operation is sensitive to type of sludge and conditioning
procedures. As raw sludge ages (3 to 4 hours) after thickening, vacuum filter performance decreases. Poor
release of the filter cake from the belt is occasionally encountered. Chemical conditioning costs can sometimes
be extremely large if a sludge is hard to dewater.
Typical Equipment/Mo, of Mfrs. (10, 77) - Rotary vacuum filter/11; Vacuum pump/27; Filtrate receiver/10; Filtrate
pump/40; Sludge conditioning apparatus/3; Sludge conveyors/7.
Performance (8, 10) - Solids capture ranges from 85 to 99.5 percent and cake moisture is usually 60 to 90 percent
depending on feed type, solids concentration, chemical conditioning, machine operation and management. Dewatered
cake is suitable for landfill, heat drying, incineration or land spreading.
Chemicals Required (10) - Fed and/or lime, or polymer dosing is a function of type of sludge and vacuum filter
characteristics.
Design Criteria (8) - Typical loadings in pounds dry solids/h/ft are 7 to 15 for raw primary sludges, 4 to 7 for
digested primary sludges, and 3.5 to 5 for mixed digested sludges. The loading is a function of feed solids
concentrations, subsequent processing requirements and chemical preconditioning.
Environmental Impact - Relatively high chemical and energy requirements.
Unit Process Reliability - Large doses of lime may require frequent washings of drum filter media. Remedial
measures are frequently required to obtain operable cake releases from belt filters. High operating skill re-
quired to maintain high level of reliability.
References - 3, 8, 10, 77
A-210
-------
VACUUM FILTRATION, SLUDGE
FACT SHEET 6.3.9
FLOW DIAGRAM -
Tank Sludge Cake Filtrate CONSTRUCTION COST (3)
10
ENERGY NOTES - Assumptions:
Electrical energy for operation of the vacuum
pumps, filtrate and other pumps and mechanical
equipment can be estimated on the basis of
11,000 kWh/yr/Mgal/d for biological sludge and
42,000 kWh/yr/Mgal/d for lime sludge.
1 0
01
Lime Sludge
Biological Sludge
linn ii i i mi
COSTS - ENR-2475 Assumptions:
0-1
1.0
10
100
Design Basis: Wastewater Flow, Mgal/d
Construction costs include: pumps, internal piping and electrical controls, mechanical equipment, conveyors,
and sludge cake storage hopper, building, chemical handling and storage facilities. Costs are for dewatering
of combined primary and secondary digested sludge consisting of 900 Ib dry solids/Mgal plant flow or lime
sludge consisting of 4.500 Ib dry solids/Mgal plant flow.
Filter yield = 5 Ib/ft for biological sludge and 8 Ib/ft for lime sludge.
Operation time (excluding downtime for maintenance): 6 h/d for 1 Mgal/d plant or less; 12 h/d for 10 Mgal/d
plant; 18 h/d for a 100 Mgal/d plant.
Chemical dosage: FeCl, = 35 Ib/Mgal; CaO = 90 Ib/Mgal.
Power Cost: $0.02/kWh.
10
0001
REFERENCES - 3
ooi
001
0001
OPERATION 8 MAINTENANCE COST:
ffi
Lime Sludge
/Po«»r
Mat
01
OOOOI
IOO
Wastewater Flow, Mgal/d
Wastewater Flow, Mgal/d
To convert construction cost to capital cost see Table A-2.
A-211
-------
DIGESTION, AEROBIC
FACT SHEET 6.4.1
Description - Aerobic digestion is a method of sludge stabilization in an open tank that can be regarded as a
modification of the activated sludge process. Microbiological activity beyond cell synthesis is stimulated by
aeration, oxidizing both the biodegradable organic matter and some cellular material into CO , HO and NO . The
oxidation of cellular matter is called endogenous respiration and is normally the predominant reaction occurring
in aerobic digestion. Stabilization is not complete until there has been an extended period of primarily endoge-
nous respiration (typically 15 to 20 days). Major objectives of aerobic digestion include odor reduction, reduc-
tion of biodegradable solids and improved sludge dewaterability. Aerobic bacteria stabilize the sludge more
rapidly than anaerobic bacteria, although a less complete breakdown of cells is usually achieved. Oxygen can be
supplied by surface aerators or by diffusers. Other equipment may include sludge recirculation pumps and piping,
mixers and scum collection baffles. Aerobic digesters are designed similarly to rectangular aeration tanks and
use conventional aeration systems, or employ circular tanks and use an eductor tube for deep tank aeration.
Common Modifications - Both one and two tank systems are used. Small plants often use a one tank batch system
with a complete mix cycle followed by settling and decanting (to help thicken the sludge). Larger plants may
consider a separate sedimentation tank to allow continuous flow and facilitate decanting and thickening. Air may
be replaced with oxygen (see Fact Sheet 6.4.3).
Technology Status - Primarily used in small plants and rural plants, especially where extended aeration or con-
tact stabilization are practiced.
Applications - Suitable for waste primary sludge, waste biological sludges (activated sludge or trickling filter
sludge) or a combination of any of these. Advantages of aerobic digestion over anaerobic digestion include, sim-
plicity of operation, lower capital cost, lower BOD concentrations in supernatant liquid, recovery of more of the
fertilizer value of sludge, fewer effects from interfering substances (such as heavy metals), and no danger of
methane explosions. The process also reduces grease content and reduces the level of pathogenic organisms,
reduces the volume of the sludge and sometimes produces a more easily dewatered sludge (although it may have poor
characteristics for vacuum filters). Volatile solids reduction is generally not as good as anaerobic digestion.
Limitations - High operating costs (primarily to supply oxygen) make the process less competitive at large plants.
The required stabilization time is highly temperature sensitive, and aerobic stabilization may require excessive
periods in cold areas or will require sludge heating, further increasing its cost. No useful by-products, such
as methane, are produced. The process efficiency also varies according to sludge age, and sludge characteristics,
and pilot work should be conducted prior to design. Improvement in dewaterability frequently does not occur.
Typical Equipment/No, of Mfrs. (23) - Sludge handling and control/32; Pumps/34; Mixers/26; Aeration equipment/30.
Performance
Total solids
Volatile solids
Pathogens
Influent
2-7%
50 - 80% of above
Effluent
3 - 12%
Reduction
30 - 70% (typical 35 - 45%)
Up to 85%
Physical Chemical and Biological Aids- pH adjustment may be necessary. Depending on the buffering capacity of
the system, the pH may drop below 6 at long detention times, and although this may not inhibit the process over
long periods, alkaline additions may be made to raise the pH to neutral.
Residuals Generated - Supernatant Typical Quality: SS 100 to 12,000 mg/1, BOD 50 to 1700 mg/1, soluble BOD 4
to 200 mg/1, COD 200 to 8000 mg/1, Kjeldahl N 10 to 400 mg/1,
5.5 to 7.7, Digested sludge.
Total P 20 to
25B
mg/1. Soluble P 2 to 60 mg/1, pH
Design Criteria - Solids retention time (SRT) required for 40% VSS reduction: 18 to 20 days at 20 C for mixed
sludges from AS or TF plant, 10 to 16 days for waste activated sludge only, 16 to 18 days average for activated
sludge from plants without primary settling; volume allowance: 3 to 4 ft /capita; VSS loading: 0.02 to 0.4
Ib/ft /d; air requirements, 20 to 60 ft /min/1000 ft ; minimum DO: 1 to 2 mg/1; energy for mechanical mixing:
0.75 to 1.25 hp/1000 ft ; oxygen requirements: 2 Ib/lb of cell tissue destroyed (includes nitrification demand),
1.6 to 1.9 Ib/lb of BOD removed in primary sludge.
Reliability - Less sensitive to environmental factors than anaerobic digestion. Requires less laboratory con-
trol and daily maintenance. Relatively resistant to variations in loading, pH and metals interference. Lower
temperatures require much longer detention times to achieve a fixed level of VSS reduction. However, performance
loss does not necessarily cause an odorous product. Maintenance of the DO at 1 to 2 mg/1 with adequate detention
results in a sludge that is often easier to dewater (except on vacuum filters).
Environmental Impact - The supernatant stream is returned to head of plant with high organic loadings. Sludge
stabilization reduces the adverse impact of land disposal of sludge. Process has high power requirements. Odor
controls may be required.
References - 3, 5, 7, 8, 10, 23, 26, 111, 119
A-212
-------
DIGESTION, AEROBIC
FACT SHEET 6.4.1
FLOW DIAGRAM
Primary Sludge
Excess Activated or
Trickling Filter Slu
I
11
w
'l '' ?*,«
r
-
-T~-=~ . * ~ ~
—^*\' •''."•"C"1 *\ •/ >J~»%v" CV*^*""1. ^ \ ^
\- -• ' *i • \ /• /T T V*j-V ' 1
TJ ' C
Clea
r 1
1
\
Clear Oxidized Overflow
to Plant
Settled Sludge Returned tc Digester -7
10
-^- Waste Sludge
ENERGY NOTES - Assumptions:
1. Energy based on oxygen supply requirements;
mixing assumed to be satisfied.
2. Mechanical aeration based on 1.5 pounds O
transfer/hph.
3. Diffused aeration based on 0.9 pounds
transfer/hph.
4. Sludge temperature 20 C.
5. Oxygen requirements for nitrification not
included.
2
10,OCO
* Dnn _ 1K /A
COSTS -Assumptions: ENR Index = 2475
1. Construction costs include basins (20 d detention time), sludge flow = 5,700 gal/Mgal (1900 Ib/Mgal at 4
percent), and floating mechanical aerators.
2. Mixing requirement: 134 hp/Mgal sludge; oxygen requirements: 1.6 lb O2/lb VSS destroyed (nitrification not
included).
3. Adjustment Factor: To adjust costs for design factors different from those above, enter curves at effective
flow (QE) .
2E
^DESIGN
X New Design Retention Time X New Design Sludge Mass X
4 percent
20 days
CONSTRUCTION COST
1,900 Ib/Mgal New Design Sludge Concentration
OPERATION & MAINTENANCE COST
001
c i_
O dj
= i
01 10 10
REFERENCES - 3, 4, 8 Wastewater Flow, Mgal/d
0001
''Labor
Powe
Ma
//
01
1 0 10
Wastewater F.OW, Mgal/d
100
00001
*To convert construction cost to capital cost see Table A-2.
A-213
-------
DIGESTION, AUTOTHERMAL THERMOPHILIC AEROBIC (AIR) FACT SHEET 6.4.2
Description - Autothermal thermophlic aerobic digestion using air is a form of aerobic digestion (See Fact Sheets
6.4.1 and 6.4.3) that operates in the thermophilic temperature range (greater than 45°C) using air as the source
of oxygen to aerate the sludge. The operation is autothermal; that is, the heat required for the increase in tem-
perature is supplied completely from the exothermic breakdown of organic and cellular material occurring during
aerobic digestion. The increased temperature, in turn, reduces the required retention time for a given amount of
solids reduction. The digester tanks are covered and insulated to minimize heat losses from the system.
Common Modifications - Use of oxygen in place of air (See Fact Sheet 6.4.3).
Technology Status - In development stage with essentially no commercial use. One full-scale unit has been
operated since May 18, 1977 at the Binghamton-Johnson City, New York wastewater treatment plant, supplemented by
laboratory scale batch and continuous reactor experiments. Preliminary results indicate the feasibility of this
process from a technical standpoint. Additional operating experience will be required to optimize design con-
ditions and determine the process' competitiveness with other sludge treatment processes. These studies have
provided the data presented below.
Applications - Autothermal aerobic digestion can be applied to sludges with solids concentrations of 1.5 percent
or greater. More dilute sludges will not reach thermophilic temperatures without supplemental heat. The high
temperatures reached in the digester may result in virtually complete destruction of pathogens and eliminate the
need for further disinfection. Thermophilic conditions can be reached in most climates and will require a much
shorter retention time than unheated aerobic digestion or anaerobic digestion. At temperatures above 50°C, a high
degree of digestion and of solids removal can be achieved with less than 8 days' retention. The high temperatures
also decrease oxygen requirements because of the inhibition of nitrification. In general, aerobic digestion
produces a supernatant with lower organic loadings than anaerobic digestion. The process may improve the settle-
ability and dewatering characteristics of sludge. The simplicity of operation may be suitable for use by small
treatment plants. May have application in cold climates where conventional aerobic digestion is ineffective or
requires excessively long detention times.
Limitations - The process is not applicable to conventional waste activated sludges (WAS) because of the large
amount of heat required to raise WAS (at 0.5 percent solids) to thermophilic temperatures. The process has high
operating costs, primarily to supply oxygen. The oxygen transfer efficiencies required to maintain thermophilic
conditions with air may be as high as 15 percent, to avoid losing too much heat through the exhaust air. No
useful by-products such as methane are produced. The economic data for this process is not well developed, and it
is not clear whether the process is competitive with other digestion processes.
Typical Equipment/No, of Mfrs. (23) - Sludge handling and control/32; pumps/34, mixers/26; aeration equipment/30.
To achieve the high oxygen transfer efficiencies required, the system used was proprietary in nature; the "Liacom
System" by DeLaval, Inc., which utilized a self-aspirating aerator. The digestion tanks will require covers and
jacketing to contain the heat.
Performance (143) - Based on full scale system-steady state performance. Selected parameters. 1000 ft reactor.
Retention Time
7.7d 5.4d
TVS loading rate (Ib/ft /d) O.17 0.26
Treatment efficiency (percent TVS removed) 37.2 22,1
pH Feed sludge 5.4 6.05
pH reactor 7.6 7.9
pH effluent 7.6 7.6
Ambient temperature 25 C 15 C
Sludge feed temperature 20°C 20°C
Reactor temperature 48 C 52 C
Oxygen transfer efficiency 8.7% 15.1%
Airflow 3 0.91 ft /s 0.78 ft /s Maximum
Maximum oxidation rate of sludge (Ib/ft /day) 0.43 (laboratory scale data)
Physical, Chemical and Biological Aids - Air, pH adjustment, if required, mechanical foam cutting.
Residuals Generated - Supernatant. Quality data not provided. See Fact Sheet 6.4.1 for quality of supernatant
from mesophilic aerobic digestion with air, which may be similar.
Design Criteria - Temperature: 45 to 70 C; Retention Time: 2 to 10 d. Sufficient data is not available for
determination of detailed design criteria.
Reliability - The full-scale demonstration project indicated few problems with process or equipment reliability.
During winter conditions (ambient: -20 C) the digester remained in the thermophilic range. There were no opera-
tional problems with the self-aspirating aerator system. There are indications that the aerobic digestion process
is generally more stable than anaerobic digestion and more easily able to recover from extreme conditions.
Environmental Impact - The process requires less space than conventional digestion and, by stabilizing and dis-
infecting sludge, reduces the adverse impact of land disposal.
References - 23, 143
A-214
-------
DIGESTION, AUTOTHERMAL THERMOPHILIC AEROBIC (AIR)
FACT SHEET 6.4.2
FLOW DIAGRAM - Single Stage unit is shown.
in a batch mode.
Two or more stages may be preferable with one or more stages operating
Sludge
Digester
Digested Sludge
ENERGY NOTES - Energy requirements for O supply and mixing were approximately 3.5 kWh/h for 1000 ft reactor,
loaded at 130 to 210 ft /d. Ongoing experiments with self-aspirating aerators will provide additional information
for determining the energy requirements for air supply and mixing.
COSTS - No cost data for the existing demonstration unit have been developed. However, a single stage digester
utilizing thermophilic aerobic digestion will require approximately 60 percent less volume than a mesophilic
aerobic digester, but will require insulation and a cover. Other equipment will be similar to that of aerobic
digestion (See Fact Sheet 6.4.1). No information on other operating costs is available.
REFERENCES - 143, 147
A-215
-------
DIGESTION, AUTOTHERMAL THERMOPHILIC (OXYGEN) FACT SHEET 6,1,3
Description - Autothermal thermophilic oxygen digestion using oxygen is a form of aerobic digestion (see Fact
Sheet 6.4.1) that operates in the thermophilic (more than 45 C) temperature range and utilizes pure oxygen instead
of air to aerate the sludge. The operation is autothermal; that is, the heat required for the increase in tempera-
ture is supplied completely from the exothermic breakdown of organic and cellular material occurring during aerobic
digestion. The increased temperatures, in turn, reduce the required retention times in the digesters to achieve a
given amount of SS reduction. The digester tanks are covered to minimize heat losses from the system. Heat Ios3es
are also reduced in pure oxygen systems because there is little exhaust gas to remove the heat generated by the
process. The equipment for pure oxygen thermophilic aerobic digestion is similar to that of aerobic digestion
(Fact Sheet 6.4.1} with the addition of digester covers and an oxygen generator.
Technology Status - Still in development stage with essentially no commercial use. Pilot plant tests have been
completed. Two preliminary full scale studies (Denver, Colorado and Speedway, Indiana) have been conducted using
pure oxygen aerobic digestion. Both achieved a significant temperature increase in the digester, but both
operated in the mesophilic temperature range. Data presented on this process for thermophilic conditions are
largely from pilot studies by Union Carbide (138). Several units are in design or construction phase, and addi-
tional data will be forthcoming.
Applications - May have greatest applications where pure oxygen activated sludge processes are used. The high
temperatures used by the process may result in virtually complete destruction of pathogens, and eliminate the need
for further disinfection. In colder climates the process will have much shorter retention times than other di-
gestion processes. At temperatures above 45 C a high degree of digestion can be obtained with less than five days
retention. The high temperatures decrease oxygen requirements because of the inhibition of nitrification. In
general, aerobic digestion produces a supernatant with lower organic loadings than anaerobic digestion. The danger
of methane explosions is also reduced.
Limitations - May not be applicable to conventional unthickened waste activated sludges because of the large amount
of heat required to raise WAS (at 0.5 percent solids) to thermophilic temperatures. The process has high operating
costs (primarily to supply oxygen). No useful by-products such as methane are produced. Oxygen aerobic digestion
in the mesophilic temperature range does not appear to be cost effective, but in the thermophilic range the reduced
O requirements and smaller reactor volume may enable the process to be competitive with other forms of digestion,
particularly when a pathogen-free sludge is desired.
Typical Equipment/No. of Mfrs. (23) - Sludge handling and control/32; pumps/34, mixers/26; aeration equipment/30;
oxygen generators/1.
Performance (138) - Pilot plant results:
Single Stage System Phase I Phase IA Phase II Phase III
Sludge Description O step feed O- step feed O activated sludge primary + O AS
Temperature (°C) 13-18 17-19 17.4 - 22 16 - 22
pH 6.0 - 6.3 5.9 - 6.4 5.9 - 6.4 5.5 - 6.1
TSS (mg/1) 25,000 - 33,000 30,000 - 34,000 25,000 - 40,000
VSS (mg/1) 21,000 - 27,000 22,000 - 27,000 20,000 - 30,000
TS (mg/1) - - - 30,000 - 49,000
TVS (mg/1) - - - 22,000 - 35,000
Retention time (days) 4.2 4.2 4.2 4.0
Digester temperature ( C) 47.3 46.4 50.4 50.2
VSS loading rate (Ib/ft /d) 0.36 0.38 0.37 0.45
VSS reduction (percent) 37 30 40 30
Two Stage System - (multiple test runs combined)
o Waste Activated Sludge Primary plus Secondary Sludge
Temperature (°C) 12 - 2412 - 30
pH 5.9 - 6.9 6.0 - 6.(i
TS (mg/1) 26,000 - 50,000 23,000 - 60,000
TVS (mg/1) 18,000 - 38,000 18,000 - 41,000
Retention time (days) 3.7 - 5.0 3-5
Digester temperature (°C) 48.7 - 57.8 45.3 - 52.0
VS loading rate (Ib/ft /d) 0.32-0.46 0.38-0.53
Overall VSS reduction (percent) 29 - 42 30 - 45
Physical, Chemical and Biological Aids - pH adjustment if necessary
Residuals Generated - Supernatant. Quality similar to that of aerobic digestion with air (Fact Sheet 6.4.1).
Design Criteria - Single or two stage systems: Retention time - five days or less, temperature 45 to 60 C.
Additional operating results are necessary to develop firm design criteria.
Reliability - Process appears stable and more easily able to recover from extremes than anaerobic digestion.
Environmental Impact - Process requires less space than conventional digestion, and by stabilizing and disinfecting
sludge reduces adverse impact of land disposal.
References - 23, 119, 138
A-216
-------
i
to
*To convert construction cost to capital cost see Table A-2.
3
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ENERGY NOTES - Assumptions: ^ W
1. Mixing requirements: 1.5 hp/1000 ft
H
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COSTS* - Assumptions: 1973 dollars; ENR = 1895.
o
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-------
DIGESTION, TWO STAGE ANAEROBIC FACT SHEET 6.4.4
Description - A two vessel system of sludge stabilization, where the first tank is used for digestion and is
equipped with one or more of the following: heater, sludge recirculation pumps, methane gas recirculation,
mixers and scum breaking mechanisms. The second tank is used for storage and concentration of digested
sludge and for formation of a supernatant. Anaerobic digestion results in the breakdown of the sludge into
methane, carbon dioxide, unusable intermediate organics and a relatively small amount of cellular protoplasm.
This process consists of two distinct simultaneous stages of conversion of organic material by acid forming
bacteria and gasification of the organic acids by methane forming bacteria. The methane producing bacteria
are very sensitive to conditions of their environment and require careful control of temperature, pH, excess
concentrations of soluble salts, metal cations, oxidizing compounds and volatile acids. They also show an
extreme substrate specificity. Can operate at various loading rates and is therefore not always clearly
defined as either standard or high rate. Digester requires periodic cleanout (from 1 to 2 years) due to
buildup of sand and gravel on digester bottom.
Technology Status - Widespread use (60 to 70 percent) for primary or primary and secondary sludge in plants having
a capacity of 1 Mgal/d or more.
Applications - Suitable for primary sludge or combinations of primary sludge and limited amounts of secondary
sludges. Digested sludge is reduced in volume and pathogenic organism content, is less odorous and easily de-
watered, and is suitable for ultimate disposal. Advantages over single stage digestion include increased gas
production, a clearer supernatant liquor, necessity for heating a smaller primary tank thus economizing in heat,
and more complete digestion. Process also lends itself to modification changes, such as to high-rate digestion.
Limitations - Is relatively expensive, about twice the capital cost of single-stage digestion. It is the most
sensitive operation in the POTW and is subject to upsets by interfering substances, e.g., excessive quantities of
heavy metals, sulfides, chlorinated hydrocarbons. The addition of activated and advanced waste treatment sludges
can cause high operating costs and poor plant efficiencies. The additional solids do not readily settle after
digestion. Digester requires periodic cleanout due to buildup of sand and gravel on digester bottom.
Typical Equipment/No, of Mfrs. - Sludge handling and control/32, pumps/34, heating equipment/7 , digestion tank
equipment/18, gas holders/6.
Performance - Influent Effluent Reduction
Total Solids 2 to 7% 2.5 to 12% 33 to 58%
Volatile Solids 35 to 50%
Pathogen 85 to less than 100%
Odor Reduction
Sidestream - Gas Production
Quantity - 8 to 12 ft /lb volatile solids added, or 12 to 18 ft /lb volatile solids destroyed or 0.6 to 1.25
ft /cap, or 11 to 12 ft /lb total solids digested.
Quality - 65 to 70% methane N , H_, H_S, NH , et al - trace 25 to 30% CO 550 to 600 Btu/ft
- £ £ £ J f.
Physical, Chemical and Biological Aids - Heat; maintain pH with lime, also ammonia, soda ash, bicarbonate of
soda, and lye are used; addition of powder activated carbon may improve stability of overstressed digesters;
precipitate heavy metals with ferrous or ferric sulfate; control odors with hydrogen peroxide.
Residuals Generated -
Supernatant - Quality: SS 200-15,000 mg/1, BOD,. 500-10,000 mg/1, COD 1,000-30,000 tag/1, TKN 300-1,000 rag/1, Total
P (50-1,000 mg/1) , scum, sludge, gas.
Design Criteria - Solids Retention Times (SRT) required at various temperatures (22)
Mesophilic Range
Temperature, °F 50 67 75 85 95
SRT, days 55 40 30 25 20
Volume Criteria, (ft /capita): Primary sludge 1.3-3, Primary and Trickling Filter Sludges 2.6-5, Primary and Waste
Activated Sludges 2.6-6. Tank Size (ft) : diameter, 20-115; depth 25-45; bottom slope 1 vertical/4 horizontal.
Solids Loading (lb vss/ft /d) : 0.04-0.40. Volumetric Loading (ft /cap/d) : 0.038-0.1. Wet Sludge Loading (lb
/cap/d) : 0.12-0.19. pH 6.7-7.6.
Overall Reliability - Successful operation subject to a variety of physical, chemical and biological phenomena,
e.g., pH, alkalinity, temperature, concentrations of toxic substances of digester contents. Sludge digester bio-
mass is relatively intolerant to changing environmental conditions. Under one set of conditions particular con-
centrations of a substance can cause upsets, while under another set of conditions higher concentrations of the
same substance are harmless. Requires careful monitoring of pH, gas production, and volatile acids.
Environmental Impact - Return of supernatant to head of plant, may cause plant upsets. The adverse environmental
impact of sludge disposal on land is reduced as a result of the process.
Miscellaneous Information - Digester gas can be used for on-site generation of electricity and/or for any in-plant
purpose requiring fuel. Can also be used off-site in a natural gas supply system. Off-site use usually requires
treatment to remove impurities such as hydrogen sulfide and moisture. Removal of CO2 further increases the heat
value of the gas. Utilization is more successful when a gas holder is provided.
References - 7, 8, 10, 20, 22, 94
A-218
-------
DIGESTION
j
TWO
FLOW DIAGRAM
ENERGY NOTES (4) -
to heat incc
Btu = (-
C = specifi
mi
Lb
: r
nc
o
e
for 1-10% solid
Energy is requi
losses during t
Btu/1000 ft
Correction fact<
Northern U.S. 1
U.S. 0.3.
Energy is genera
plant flow):
Gas Produced, s
Heat Available,
Electrical ener
assuming contim
release of gas,
COSTS* (3) (1976
1. Service life
2. Includes die
3. Feed to dige
(75% volati]
operating tt
4. Power costs
5. To adjust cc
QE = Q
10
«
ra
o
Q
"o
in
c
o
* 10
01
0
REFERE1TCES-
*To convert
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DE
STAGE ANAEROBIC
FACT SHEET 6A4
GAS I I GAS . ,
RELEASE 1 . RELEASE II _^^
/ GAS N^ / GAS ^^\
SLUDGE
INLET _
As sump
ludge t
nfluent
of slue
ludge .
to con
digest:
f cont«
for gee
Middle
d from
Mgal
tu/Mga]
is reqi
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tor ef
liars)
s 50 ye
ter, he
ers is
; efflu
erature
$.02/kh
s for 1
SIGN *
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ZONE OF
f"
(MIXING 1
V_^
ACTIVELY
DIGESTING .S.
S. SLUDGE //2?
<&^^*~
E RETURN
Energy is
ter tempei
) (C) (T(°F
Btu/lb/°
for heat
od:
,600/hr
al locati
.5, South
duct ion (t
5,175
3.1
ed for mixing
on, 20 ft. subi
lency 85-93%.
ssumptions :
-exchanger , gas
nbined primary
t from digestei
85 to 110°F; c
3ing rates difi
=w Design Sludc
1,
TRUCT
~"
900 lb/Mgt
ION COST
S
^
required
-ature :
)
Dn :
srn
ased on
WAS
MIXED
. UQUOR _ .^-v.'.'.-'ji.'-y 'A-i.-.-Mi.-,,'
= *^
SUPERNATANT
!-"^.-,y> -^••V-^Vvi'^'^.-il*':-1 r
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DRAWOFF ->r- ^*^. ./^
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SUPERNATANT
T, REMOVAL
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w Gas rlow SCFM/1000 cu f t: : i
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mergence :
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je Mass
s
7
*£-
6.5 o ^
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w ^
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103
on equipment, control bull
dary and is thickened to 1
Ib/Mgal at 2.5% solids; lo
as is utilized for heating
in those presented here, en
OPERATI
1 0| 1— | [ | | | |||
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£— — £-C.'t-..
12 v< 2
jF r- f
^
00 cu ft
104 105 106
DIGESTER VOLUME, ftj
ding.
,900 Ib/Mgal at 4% solids
ading rate - 0.16 Ib/ft /d;
, excess is not utilized.
ter curve at effective flow (QE> .
ON & MAINTENANCE COST
i — n — n 1 1 1 1 IL i i i i 1 1 1 LH °01
^
/
' - «
/ ^*
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o
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1 10 10 100 01 10 10 100
3,4,8 Wastewater Flow Mgal/d Wastewater Flow, Mgal/d
construction cost to capital cost see Table A-2.
A-219
-------
DIGESTION, TWO STAGE THERMOPHILIC ANAEROBIC FACT SHEET 6,1.5
Description - Digestion is a fermentation process in which several groups of anaerobic and facultative organisms
assimilate and break down organic matter into primarily CO and methane. The process takes place in two tanks in
series; the first for digestion and the second for storage and concentration of sludge and formation of a super-
natant. Thermophilic digestion operates at a temperature of approximately 46 to 57 C (115 to 135 F). The methane-
producing bacteria essentially control the process and are very sensitive to pH, excess concentrations of soluble
salts, metal cations, temperature, and substrate concentration. For additional details on anaerobic digestion
see Fact Sheet 6.4.4.
Technology Status - Full-scale studies of thermophilic digestion are in progress at the Hyperion plant (Los
Angeles, California) and serve as the basis for the data presented.
Applications - Thermophilic digestion may be a viable alternative to mesophilic anaerobic digestion for primary
or combined primary and waste activated sludges (WAS). The high cost of heating the sludge may rule out its use
on WAS alone. Thermophilic digestion enhances sludge dewaterability and methane production and achieves a greater
reduction of volatile solids, and reduces polymer dosage and pathogens.
Limitations - The higher temperatures require additional heat input; however, this may be offset by higher methane
production. Thermophilic bacteria are more sensitive to loading and temperature changes than mesophilic bacteria
and more severe temperature limitations. Thermophilic digestion may solubilize some heavy metals, and the result-
ing recycle supernatant streams are higher in certain metals and in organic loadings than those from mesophilic
operations. The digestion process itself is relatively expensive, and is highly sensitive to interferences such
as heavy metals, sulfides and chlorinated hydrocarbons. There is some new data on thermophilic digestion as
applied to WAS or a combination of WAS and primary sludge, but analysis is not complete. Thermophilic digestion
requires additional operator expertise and attention because of process sensitivities.
Typical Equipment/No, of Mfrs. (23) - Physically similar to conventional anaerobic digestion. Sludge handling
and control/32; pumps/34; heating equipment for digestors/7; digestion tank equipment/18; gas holders/6.
Performance (124) -
Influent Effluent Reduction Notes
Total Solids (percent) 6.1 2.1 66% Includes reductions from dilution
Volatile Solids (Percent) 78 65 70% with steam used to heat sludge.
pH 5.1 7.6
Alkalinity (mg/1) 1600 4100
Temperature, F 77° 120°
Other: Gas production 12.7 ft /lb VS added; gas quality 63 percent methane; volatile solids in sludge 600 mg/1;
detention time 18.2 days. Salmonella and virus removals are greatly increased over mesophilic digesters, but
ascaris removals were negligible in both cases.
Effect of thermophilic digestion on dewatering (124):
Chemical Solids Cake Centrate
Dosage Capture (Percent)
Dewatering Method Feed Rate (Ib/ton) (Percent) Solids)
Solid bowl centrifuge 25 gal/min 8 92 32
Basket bowl centrifuge 40 gal/min 6 38 31
Physical, Chemical and Biological Aids - Heat, lime for maintaining pH, sodium bicarbonate, ammonia, soda ash,
caustic, etc., nutrients to aid digestion if required, inorganic salts for metal precipitation, hydrogen peroxide
for odor control, polyelectrolytes for subsequent thickening.
Residuals Generated - Data on separate supernatant stream is not available (see Fact Sheet 6.4.4 for supernatant
from mesophilic range). Filtrate quality (in mg/1) SS 1000, TDS 1500, COD 2700, N(total) 1400, PO 700, grease
1400, copper, cadmium, zinc, nickel, chromium, all measurable at less than 1 mg/1.
Design Criteria - Solids retention times required at various temperatures (22) - 20 d at 100 F, 15 d at 110 to
130 F. Loading rate 0.1 to 0.2 lb VS/ft /d, pH 6.6 to 7.4, tank diameter 20 to 115 ft, center depth 25 to 45 ft,
minimum bottom slope 1 vertical to 4 horizontal. Process design criteria are not fully developed and require
more operating experience with various sludges and under different environmental conditions.
Overall Reliability - Limited operating data indicates a great deal of complexity of operation. The process
requires a long time to achieve steady state conditions, and maintenance of these conditions is subject to a
variety of physical, chemical, and biological phenomena such as pH, alkalinity, temperature, interfering sub-
stances, loadings, etc. High operator attention and monitoring required.
Environmental Impact - Recycle streams sent to head of plant may cause upsets. Reduced sludge generation reduces
the adverse impact on the environment. Boiler blowdown and air pollutants from boiler fuel may result.
References - 7, 8, 10, 22, 23, 26, 124, 136
A-220
-------
DIGESTION, TWO STAGE THERMOPHILIC ANAEROBIC
FACT SHEET 6.4.5
FLOW DIAGRAM -
Release 1
Sludge
Inlet
Fuel
»
Sludge
Heater
Zone of
r^
1 Mixing
Actively
Digesting .s
Mixed
Liquor
Supernatant
Digested
^Sludge .
Supe
Remo
Sludge Drawoff
To further processing
ENERGY NOTES - Fuel requirements shown are for northern states. For central locations, multiply by 0.5; for
southern locations, multiply by 0.3; digester temperature = 130 F; energy credits for anaerobic digester gas
production (124) = 18,000 ft /Mgal; 63 percent methane; 6.8 MBtu/Mgal.
io6
io
o* 4
10
10
1 Primary
2 Primary + FeCl
3 Primary + Low Lime
4 Primary + High Lime
5 Primary + W A S
6 Primary + (W A S + FeCl )
7 (Primary + FeCl ) + W A S
•8W A S
III Mil II I I III
io
io
10
IO 3 IO
Digester Volume ft
10 10
COSTS'- Solids, Ib/day
1. Costs include: digester, heat-exchanger, gas-collection equipment, control building (ENR Index = 2475).
2. Feed to digesters is combined primary and is thickened feed = 1,900 Ib/Mgal at 4 percent solids (75 percent
volatile) . 3
3. Effluent from digesters is 900 Ib/gal; at 2.5% solids; loading rate = 0.16 Ib VSS/ft /d; operating tempera-
ture = 130°F.
4. Adjustment Factor; To adjust costs for loading rates different than those presented here, enter curve at
effective, flow (P-E)-NPW Deslqn sludge Mass
CE ^DESIGN " 1,900 Ib/Mgal
CONSTRUCTION COST
OPERATION S MAINTENANCE COSTS
10
1-0
0.1
to id
O -H
•H - a
r-t rH +J
fH flj O
ST!"
1 10
Wastewater Flow, Mgal/d
.001
.1
Total
Material
Labor
8
1 10
Wastewater Flow, Mgal/d
0001
100
REFERENCES - 3, 4, 8, 124 Costs adjusted from mesophilic operation to thermophilic operation from references.
*To convert construction cost to capital cost see Table A-2.
A-221
-------
DISINFECTION (HEAT) FACT SHEET 6.4.6
Description - Heating to pasteurization temperatures is a well known method of destroying pathogenic organisms
that has been applied successfully to disinfecting sludge. Pasteurization implies heating to a specific tem-
perature for a time period sufficient to destroy undesirable organisms in sludge and to make sludge suitable for
land disposal on cropland. Usually heat is applied at 70 to 75 C for a period of 20 to 60 minutes. Treatment can
be applied to raw liquid sludge (thickened or unthickened), or stabilized or digested sludge.
Pasteurization is usually a batch process, consisting of a reactor to hold sludge, a heat source, and heat exchange
equipment, pumping and piping and instrumentation for automated operation. Pasteurization has little effect on
sludge composition or structure because the sludge is only heated to a relatively moderate temperature.
Technology Status - Not widely used. More common in Europe than in the United States. In West Germany and Swit-
zerland, there are regulations (actually seldom followed) that require pasteurization when sludge is spread on
pastures during summer growth periods. May find increased application with the renewed interest of land disposal
of sludges.
Applications (119) - Can be applied to a wide variety of sludges in various forms. Pasteurization may be redun-
dant where sludges are treated by other processes which destroy pathogenic matter. Largest potential application
is to otherwise untreated sludges which are disposed of on land. Studies show that liquid sludge need only be
cooled to 60 C for application to land with no adverse effects from temperature. Small treatment plants can
pasteurize liquid digested sludge in a tank truck with steam injection.
Limitations - Pasteurization has little or no effect on metals or other toxic materials. Pasteurized but undi-
gested sludges still have considerable risk of foul smelling fermentation after land applications. Limited data
is available on interferences and other process controls required for optimizing the process. Heating unthickened
sludge requires excessive amounts of heat. Because of the low temperatures involved, heat recovery is not cost
effective unless the sludge flow is at least 50,000 gal/d. At this level, one-stage heat recuperation may be cost
effective. Two stage recuperation is not cost effective until a flow of over 100,000 gal/d of sludge is reached.
Typical Equipment/No, of Mfrs. (23) - Sludge handling and control/32; Heating equipment/7; Instrumentation/9.
Performance (111,119) - Seventy-five degrees Centigrade for 60 minutes will reduce coliform indicators below 1,000
counts per 100 ml. Seventy degrees Centigrade for 30 to 60 minutes is effective for destroying pathogens in di-
gested sludge. Seventy degrees Centigrade for 20 minutes is effective for destroying pathogens in raw sludge.
Heat treatment also appears to destroy viruses. The table below indicates the time required for 100 percent elim-
ination of various typical pathogenic organisms found in sludge at various temperatures:
o
Temperature C
Organism 50 55 60 65 70
Time Required for 100% Reduction (minutes)
Cysts of Entamoeba histolytica 5
Eggs of Ascaris lumbricoides 60 7
Brucella abortus 60 3
Corynebacterium diphtheriae 45 4
Salmonella typhosa 30 4
Escherichia coli 60 5
Micrococcus pyrogene var. aureus 20
Mycobacterium tuberculosis var. 20
Viruses 25
See Reference 119 for detailed experimental data on destruction of pathogens as a function of time and temperature.
Physical, Chemical and Biological Aids - Heat, typical boiler feedwater pretreatment chemicals (scale and/or cor-
rosion) .
Residuals Generated - Boiler blowdown, air pollution from the boiler.
Design Criteria - Temperature 70 to 75 C; time 20 to 60 minutes; heat required 4-6 x 10 Btu/ton of sludge solids.
Two units or more are usually designed in parallel so one unit can be filling while the other is holding sludge
for the required length of time. Units can share a common boiler.
Unit Process Reliability - Mechanical and process reliability high. Pasteurization can be fully automated and
requires minimum operator attention. There is little operating experience in the United States.
Environmental Impact - Reduces the adverse impact of sludge disposal to cropland. If steam injection is used to
heat the sludge, chemicals used for feedwater pretreatment must be acceptable for land spreading of sludge.
Miscellaneous Information - Digested sludge heat can reduce the need for supplemental energy. Methane from
anaerobic digestion can provide the required fuel for pasteurization.
References - 8, 23, 111, 119
A-222
-------
DISINFECTION (HEAT)
FACT SHEET 6,4,6
FLOW DIAGRAM -
feed Water
Boiler
Sludge
Holding Tank
Pasteurized Sludge
ENERGY NOTES - Fuel requirements for heating (119); 4.6 X 10 Btu/ton of sludge (assuming 5 percent solids and 53
temperature rise requirement). At 250 tons/d or more, heat recovery may reduce the fuel requirement; anaerobic
digesters could provide this energy. Electrical requirements. Approximately 14 kwh/ton of sludge for pumps and
mixing.
COSTS (1978) -Assumptions: ENR Index = 2776
2.
1. Design Basis: Sludge temperature, 17 C; sludge solids, 5 percent; pasteurization temperature, 70 C; pas-
teurization time, 1 h.
Construction cost includes: steam boiler, pasteurization tanks, sludge pumping and automatic controls.
3. Single tank up to 10 tons of sludge solids per day; two tanks above.
4. Labor was estimated at $6/ton of sludge solids for small plants, decreasing to 52/ton of sludge solids for
very large plants.
5. Fuel, $2.80/MBtu.
CONSTRUCTION COSTS
OPERATION AND MAINTENANCE
1 0
0 1
5 001
0001
1 0
Q 0 1
o
0001
s
1 Operating Costs.
1
•Labor
ruel,
10 100
Tons of Sludge/Day
1000
10 100
Tons of Sludge/Day
1000
REFERENCES - 111, 119
*To convert construction cost to capital cost see Table A-2.
A-223
-------
HEAT TREATMENT OF SLUDGE FACT SHEET 6.4.7
Description and Common Modifications - The heat treatment process involves heating sludge to 144 to 210°C for
short periods of time under pressure of 150 to 400 Ib/in g. It is essentially a conditioning process which pre-
pares sludge for dewatering on vacuum filters or filter presses without the use of chemicals. In addition, the
sludge is sterilized and generally stabilized and rendered inoffensive. Heat treatment results in coagulation of
solids, a breakclowr, in the cell structure of sludge and a reduction of the water affinity of sludge solids.
Several proprietary variations exist for heat treatment. In these systems, sludge is passed through a heat ex-
changer into a reactor vessel, where steam is injected directly into the sludge to bring the temperature and
pressure into the necessary ranges. In one variation air is also injected into the reactor vessel with the
sludge. The detention time in the reactor is approximately 30 minutes. After heat treatment, the sludge passes
back through the heat exchanger to recover heat, and then is discharged to a thickener-decant tank. The thickened
sludge may be dewatered by filtration or centrifugation to a solids content of 30 to 50 percent. The sludge may
be ground prior to heat treatment.
Technology Status - The process of heat treating sludge was first introduced in 1935, but has only become common
during the last decade. About 100 units are currently in operation in the United States.
Applications - Heat treatment is practiced as a sludge conditioning method to reduce the costs of sludge dewater-
ing and ultimate disposal. The benefits of heat treatment include: (1) Improved dewatering characteristics of
treated sludge without chemical conditioning; (2) Generally innocuous and sterilized sludge suitable for ultimate
disposal by a variety of methods including land application in some cases; (3) few nuisance problems, (4) suitable
for many types of sludge which cannot be stabilized biologically; (5) reduction in subsequent incineration energy
requirements; and (6) reduction in size of subsequent vacuum filters and incinerators.
Limitations - The process has very high capital and operating costs, and may not be economical at small treatment
plants. Specialized supervision and maintenance are required due to the high temperatures and pressures involved.
Expensive material costs are necessary to prevent corrosion and withstand the operating conditions. Heavy metal
concentrations in sludges are not reduced by heat treatment and further treatment of sludges with high metals
concentrations may be required if the sludge is to be applied to crop land. The sludge supernatant and filtrate
recycle liquor are strongly colored and contain a very high concentration of soluble organic compounds and ammonia
nitrogen, and in some cases must be pretreated prior to return to the head of the treatment plant.
Typical Equipment/No, of Mfrs. - Complete heat treatment systems are generally proprietary, and the most common
systems are supplied by five manufacturers. The major equipment common to these processes are grinders, sludge
feed pumps and handling equipment, heat exchangers, reactors, boilers, and separators.
Performance - Heat treatment is a conditioning process, and is intended to enhance the performance of subsequent
operations. Within the process itself pathogens are destroyed and 30 to 40 percent of the VSS are solubilized.
Dewatering efficiency can be increased to a solids capture of over 95 percent and a solids content of up to 50
percent.
Physical, Chemical and Biological Aids - Heat; Chemicals for dewatering are not normally required. Corrosion
control aids may be required for the boiler and/or the process.
Residuals Generated - Sidestream (recycle liquor) 50 percent of sludge flow (by volume); quality - BOD, 5,000 to
15,000 mg/1; COD, 10,000 to 30,000 mg/1; NH -N, 500 to 800 mg/1; P, 140 to 250 mg/1; TSS, 9,000 to 12,000 mg/1;
VSS, 8,000 to 10,000 mg/lj pH, 4 to 6.
This stream is generally amenable to biological treatment but can contribute up to 30 to 50 percent of the organic
loading to a treatment plant. If the plant has not been designed for this additional load, pretreatment prior to
return may be necessary. Some non-condensable gases may be generated which will require combustion or disposal.
Boiler blowdown and/or water treatment residuals (for boiler feedwater) may result.
Design Criteria - Temperature 140 to 210 C, pressure 150 to 400 Ib/in g, detention time 30 to 90 minutes, steam
consumption 600 lb/1000 gal of sludge.
Overall Reliability - Limited operating data is available. Mechanical and process reliability appear adequate
after some initial operational problems. Careful operator attention is required.
Environmental Impact - Recycle liquor sent to head of plant can cause plant upsets due to very high organic load-
ings. The process can result in offensive odor production if proper odor control is not practiced. A colored
effluent may also result, requiring additional processing where discharge standards prohibit this condition.
Miscellaneous Information - The composition of the recycle liquor can vary among the various processes. Some
liquors may contain a high proportion of non-biodegradable matter. This matter is largely humic acids, which can
give rise to unpleasant odors and taste if present in water which has been chlorinated prior to use for domestic
supply. If industrial wastes of various types are included in the wastewater to be treated, the actual chemical
composition of the liquor resulting from heat treatment of the sludge should be determined by a detailed chemical
analysis. A possible treatment process for a highly polluted liquor can consist of filtration, aeration and
activated carbon adsorption for non-biodegradable organics.
References - 3, 7, 8, 26, 31, 95, 111, 199
A-224
-------
HEAT TREATMENT OF SLUDGE
FACT SHEET 6.4.7
ENERGY NOTES - Assumptions: Reactor Conditions; 300 Ib/in g at 350°F; Heat exchangers T = 50°F; continuous
operation; electrical includes all pumping, grinding, air compressing artd post thickening drives; fuel is to
produce steam to bring reactor to operating temperature.
5
io
10
_i
Vl
— —
^
it
11
il
— -T
L Sludg<
Jiout Ai
;h Air
^i Air
ft I — H —
1
-strr
1 T-W
maximu
minimu
^
! ' /
'
•/
m)
m)
•^
r~\
*
-^
^
LUJ
^ ^
.
7 7
' '
'
— .
Trr^
,»
;• /
,'
-p
s
^
k
^ ! •
y'' ,
' '
X
0.1 1.0
Thermal Treatment
10
10
10"
Lc
.•••
>w
—
ft*
Ox
^
0^
1C
iati
^
on (
s
•;;=?
Ai
'
<
r L
/
'
\&
/
s
diti
^
Thermal Condi
on)>^
itH
t '
,ioni
S.
^
nc
*?
^
<
1
/
t
Nc
/
f
2
/
Air
10 10° iu 1.0 10 100 1,000
' gal/min Thermal Treatment Capacity, gal/min
:OSTS ' Construction costs include: sludge feed pumps, grinders, heat exchangers, reactors, boilers, gas separators
and buildings. Costs are related to average wastewater flow by the following: Sludge quantity = 1900 lb/ Mgal (un-'
digested, combined thickened primary plus secondary sludge); solids concentration = 4.5 percent; sludge flow = 3.8
gal/min/Mgal/d based on 8,000 operating h/yr. Fuel costs are for steam generation. ENR Index = 2475
Adjustment Factor: To adjust costs for design factors different than for those above, enter curve at effective flow
E '
QE = QDESIGN X (New Desl8n Sludge Mass)/(1,900 lb/Mgal)
100
CONSTRUCTION COST
OPERATION & MAINTENANCE COST
10
10
01
Q
B
O
0 1
10 10
Wastewater Flow Mgal/d
100
0001
Fuel
Tot \
01
REFE^NCES-3 ,4,8
*To convert construction cost to capital cost see Table A-2.
10 10 100
Wastewa er Flow, Mgal/d
A-225
-------
LIME STABILIZATION FACT SHEET 6.4.8
Description - The addition of lime, in sufficient quantities to maintain a high pH stabilizes sludge and destroys
pathogenic bacteria. Lime stabilized sludges dewater well on sandbeds without odor problems. Sludge filterability
can also be improved with the use of lime. Lime is also used prior to land application of sludges. Mixing of lime
with liquid sludges is best accomplished with air mixing. For a detailed description of lime handling and feeding
systems, see Fact Sheet No. 5.1.5.
Applications - Lime addition to raw or digested sludges to a stable (several hours) pH of over 12 or greater
effectively stabilizes sludge for land application. Pathogens viruses and bacteria are destroyed, but worm eggs
are resistant. Disinfection is superior to that obtained by mesophilic anaerobic digestion. Hydrated lime is
often used in conjunction with metal salts to improve dewaterability. Though lime has some slight dehydration
effect on colloids, its use in conditioning is mainly for pH control, odor reduction, disinfection and filter aid
effect.
Limitations - Lime treatment produces essentially no organic destruction. Therefore caution is required when
sludge cake disposal to land is practiced. Disposal in thick layers could create a situation where the pH could
fall to near 7 prior to the sludge drying out, causing regrowth of organisms and resulting noxious odors. Main-
tenance of a pH of 11 for two weeks or more can minimize these problems. Lime handling and feed systems can
require a high degree of operator attention.
Technology Status - Lime has been in widespread use for over 100 years, and the shipping, handling and feeding of
lime is a well proven technology. Polymers recently have been replacing lime in some sludge conditioning appli-
cations prior to mechanical dewatering. Lime may have an increasing role as land application of sludges becomes
more common.
Typical Equipment/No, of Mfrs. (23, 97) - Bins/over 50; Hoppers/over 40; Conveyors and elevators/over 50; Lime
slakers/6; Chemical feed equipment/25; pH instrumentation/over 50; Sludge handling and control/32.
Performance (8) - A full scale study indicated the following effects of lime treatment on pathogenic bacteria
(initial pH = 12.5, maintained above pH = 11.5 for 24 hours). Units - organisms/100 ml of sample.
Sludge Salmonella Fecal Strep. Fecal Coli
Raw primary 62 39 x 10 8.3 x 10
Limed raw primary Less than 3 6 x 10 5.9 x 10
Waste activated sludge 6 1x10 2.7x 10
Limed waste activated Less than 3 6.7 x 10 1.6 x 10
Septage 6 6.7 x 102 1.5 x 10^
Limed septage Less than 3 6.7x10 2.6x10
The effect of lime stabilization on vacuum filterability of sludge from a laboratory test is presented below
(Filter leaf test yield: Ib/h/ft ).
Sludge Al Dose (mg/1) Fe Dose (mg/1)
Before lime addition .98 .94 .95 1.06 1.57
After lime addition 1.97 2.10 2.58 1.57 2.40
Note: Cake moisture (before and after) in all cases was essentially unchanged at 4.0 Ib water/lb dry solids - 10
percent.
Chemicals Required - Lime (CaO or Ca(OH) )
Residuals Generated - None
Design Criteria (73) - Lime requirements to raise pH in sludges are as follows:
Sludge - Percent Solids 1% 2% 3% 3.5% 4.4%
pH=ll Ca(OH) dosage, mg/1 1400 2500 3700 6000 8200
pH=12 CafOH)^ dosage, mg/1 2600 4300 5000 9000 9500
Lime dosage required to maintain sludge at pH greater than or equal 11.0 for at least 14 days.
Sludge Type Dosej Ib Ca (OH) ,,/ton
Primary 200 - 300
Septage 200 - 600
Biological 600 - 1000
Al(Secondary) Precipitation 800 - 1200
Fe(Secondary) Precipitation 700 - 1200
Al(Primary & Secondary) Precipitation 500 - 800
Unit Process Reliability - Highly reliable from a process standpoint. However, above average operator attention
and cleaning requirements are necessary to maintain the mechanical reliability of the lime feed.
Environmental Impact - The volume of sludge generated may be increased, although lime can reduce the pathogenic
bacteria and odor of sludge rendering it more suitable for land disposal. Improved dewaterability can result in
less land use demand through smaller sized sand bed requirements. Disposal of sludge with high pH.
References - 3, 7, 8, 23, 26, 73
A-226
-------
LIME STABILIZATION
FACT SHEET 6,4,8
FLOW DIAGRAM -
Sludge
pH control
Lime
1
/ "
^T
Lime sluzry pot
Lime slurry
- 1 /
^
/
Stabilized sludge
10
INERGY NOTES - Assumptions: Pump feed of slaked lime; mix lime
and sludge for 60 seconds at G = 600/s; sludge pumping not
included.
TJ
01 5
.Jj 10
3
O1
10
ID'
LI
M
D
OS
AGE
= 1
::ar
4C
000 Ib/to
0 Ib/tonJ
0
It
/
200 lb/
s
/
/
/
^
^
f
^r
•^
/
'
Con
ton
- • •
^ '
n as
MIX
.:s_
%
'5*^
c
^
^
f>
>
a(C
-^
(^
*y
VX
)H);
^h
x ,,
/
^ ^
> . . ,
/
^ ( '
•* 1 '
100
1,000
10,000
100,000
COSTS* - January 1978 dollars; ENR Index = 2672 Sludge Quantity, Ib/d
T. Construction cost includes: bulk lime storage bin (hydrated lime for 1 Kqal/d,-pebble quicklime for 4 and 40
Mgal/d), augers, volumetric feeder, slurry tank, line slaker, sludge mixing S thickening tank, sludge grinder,
transfer pumps, all weather treatment building, and sludge holding lagoon with 60 day detention time.
Operation and .Maintenance Costs; labor rates are $6.50 per hour; lime costs are $44.50 per ton for 46.8 per-
cent CaO hydrated lirae and $40 per ton for 85 percent CaO quicklime.
Lime dosage required per unit dry solids as 100 rc-c^-- Ca(OH)? is 0.20 Ib/lb.
CONSTRUCTION COST
OPERATION & MAINTENANCE COST
01
001
Q o 1
o|
To l~001
0 1
1 0 10
Wastewater Flow, Mgal/d
-LU 0001
100 0 1
-Labor
Total /
Maten
0 1
0 01
0001
1 0 10
Wastewater How, Mgal/d
00001
100
REFERENCED-4,73,232
*To convert construction cost to capital cost see Table A-2.
A-227
-------
AEROBIC TREATMENT AND ABSORPTION BED FACT SHEET 7,1,1
Description - An aerobic treatment unit followed by a soil absorption bed is an on-site system for the treatment
and disposal of domestic wastewater. Various aerobic suspended and fixed growth processes are available alterna-
tives to the conventional septic tank (see Fact Sheet 7.1.6). The activated sludge process employs high concen-
trations of microorganisms under aerobic conditions in a batch or flow-through/ extended aeration operation.
Forced air diffusion or mechanical aeration is followed by clarification, whereby the biomass is separated from
the treated wastewater. A portion of the separated biomass is recycled back to the aeration chamber in the flow-
through mode. Fixed film treatment processes employ a large surface area upon which microorganisms will grow and
over which wastewater is distributed so that the biomass may contact and metabolize pollutants within the waste
streams. Aeration may be provided by natural convection, mechanical aeration, or forced air ventilation. A
solid-liquid separation step normally follows, along with recycling of treated wastewater back to the fixed media.
Examples of fixed film systems include the packed tower, rotating contactor, and submerged media system. Treated
effluent can then be discharged to a soil absorption field for disposal. Distribution piping surrounded by gravel
is buried in a seepage bed or a series of absorption trenches, designed on the basis of site and soil charac-
teristics. Wastewater is spread throughout the field and conducted into the subsoil. (See Fact Sheet 7.1.6)
Modifications - The aerobic unit may be preceded by a septic tank or trash trap to remove grease, floating solids,
and large debris or a surge tank to equalize flow. Clarifiers, tube and plate settlers, or surface filtration are
alternatives for solids separation following aeration. Solids return in flow-through operations can be provided
by either gravity, air lift pumps, or draft tubes.
Technology Status - Aerobic units are used extensively in package plants for institutional and commercial on-site
treatment, but their share of the individual home treatment market is quite small.
Typical Equipment/No, of Mfrs. - Package aerobic unit, including tank, aeration equipment, and controls/more than
20; distribution piping/locally supplied.
Applications - Used as alternative to the conventional septic tank for on-site treatment of household wastewater.
Aerobic units, when properly operated and maintained can result in a higher effluent quality than septic tanks and
can reduce clogging in coarse (sandy) soils. Although pretreatment can potentially be improved, subsurface
drainage beds should be limited to sites with recommended soil depths and permeability, as with septic tanks.
Limitations - On-site aerobic processes potentially produce a higher degree of treatment than septic tanks, but
periodic carryover of solids due to sludge bulking, toxic chemical addition, or excessive sludge buildup can
result in substantial variability in effluent quality. Regular, semi-skilled operation and maintenance is
required to ensure proper functioning of moderately complex equipment, and inspections every two months are
recommended. Power is required to operate aeration equipment and pumps. Absorption beds are dependent upon site
and soil conditions, and are generally limited to sites with percolation rates less than 60 min/in, depth to water
table or bedrock of 2 to 4 ft, and level or slightly sloping topography. (See Fact Sheet 7.1.6).
Performance - Aerobic units can achieve higher BOD removals than septic tanks, but SS removals, which are highly
dependent on the solids separation methods utilized, are similar. Nitrification is normally achieved, but little
reduction in phosphorus is effected. Field studies indicate that suspended growth units can provide from 70 to 90
percent BOD and SS reductions for combined household wastewater, yielding effluent BOD and SS concentrations in
the range or 30 to 70 mg/1 and 40 to 100 mg/1, respectively. Limited data for fixed growth units tested with
municipal or synthetic wastewater show effluent BOD and SS concentrations of 30 to 50 mg/1 and 40 to 60 mg/1,
respectively (149). A properly designed and constructed soil absorption bed will effectively remove pollutants,
including bacteria, viruses, and heavy metals, by natural adsorption in the soil zone adjacent to the field.
However, nitrate movement through many soils to groundwater may be substantial.
Chemicals Required - None.
Residuals Generated - Excess sludge containing organics, grease, hair, grit, and pathogens must be removed from
aerobic units and disposed of every 8 to 12 months. If a septic tank is used for pretreatment, sludge may be
wasted to the tank, reducing offsite pumping frequency.
Design Criteria - Design peak flow: 75 gal/d/person. Commercial designs must be evaluated in light of site
specific requirements. The absorption area requirements shown on Fact Sheet 7.1.6 apply for finer textured soils;
some size reduction is possible for coarser soil types with aerobic treatment.
Reliability - Aerobic processes are sensitive to microbial upsets and effluent quality is dependent upon super-
vised operation. Proper design and maintenance of mechanical equipment is necessary for effective treatment.
Environmental Impact - Sludge is generated, requiring approved treatment and disposal. Effluent can contaminate
groundwaters when pollutants are not effectively removed by the aerobic unit or the soil system. Aeration equip-
ment can be noisy. Poorly maintained units may produce odors.
References - 14, 149, 152, 160
A-228
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AEROBIC TREATMENT AND ABSORPTION BED
FACT SHEET 7.1.1
FLOW DIAGRAM -
Q
Wastewater
///SCUM
TRASH
TRAP
/', SLUDGE''
cfc
AERATION
ABSORPTION FIELD
(PLAN)
EXTENDED AERATION UNIT
(PROFILE)
ENERGY NOTES - 700 to 3,600 kWh/yr for aeration and pumping.
COSTS* - 1978 dollars; ENR Index = 2776. The following are cost estimates for a household aerobic unit and soil
absorption system:
Aerobic treatment unit, including design, permit and installation with $1,000 to $3,500
20 year service life for shell and 10 years for equipment
Soil absorption system (300 to 750 ft ) with 20 to 30 year service life
($1 to $2.10/ft )
Construction costs
Maintenance of aerobic unit, including sludge removal (routine and
unscheduled)
375 to 2,100
$1,375 to $5,600
$ 50 to $ 150
Power ($0.02/kWh)
15 to
75
Annual operating costs
65 to $ 225
Soil absorption system construction cost includes excavation, gravel, pipe, backfill, and miscellaneous labor.
This cost can vary significantly, depending upon site and soil characteristics, size and type of bed, and local
material and labor costs.
REFERENCES - 103, 152
To convert construction cost to capital cost see Table A-2.
A-229
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AEROBIC TREATMENT AND SURFACE DISCHARGE FACT SHEET 7.1.2
Description - Surface discharge of aerobically treated domestic wastewater is an alternative on-site disposal
method that can be used when the conventional soil absorption system would be inadequate as a treatment and dis-
posal medium. If an appropriate receiving water is available, the level of treatment required may vary depending
on local regulations, stream water quality requirements, and other site-specific conditions. Numerous field
studies have shown that well-maintained aerobic units produce effluents containing concentrations somewhat in
excess of secondary treatment requirements of 30 mg/1 of BOD and SS. To attain this standard, some form of
additional treatment is necessary. Granular filtration, with its simplicity and low operation and maintenance
requirements, has proven effective for this purpose. Various aerobic suspended and fixed growth processes are
available as alternatives to the conventional septic tank. The activated sludge process in batch or flow-through
extended aeration designs and fixed film processes, which distribute wastewater over large surface areas of micro-
organisms, can produce higher quality effluents than septic tanks if properly maintained and operated (see Fact
Sheet 7.1.1). The intermittent sand filter, successfully tested in the field, consists of a 2 to 3 ft deep sand
bed which remains aerobic and removes SS and dissolved organics. The filter surface is flooded intermittently
with pretreated wastewater at intervals which permit the surface to drain between applications. Filtrate is
collected by underdrains for final discharge. A sand filter preceded by aerobic treatment does not normally
require alternating units, as is necessary for a filter following septic tank pretreatment. However, the filter
surface with accumulated solids should be removed and replaced with clean sand every 6 months. Alternative
filters are described in Fact Sheet 7.1.8.
Modifications - A septic tank to remove grease, floating solids, and large debris or a surge tank to equalize flow
may precede an aerobic unit. A dosing pump and chamber can be used to distribute effluent over the filter surface,
Covered, insulated filters are used in areas with extended periods of sub-freezing weather. Disinfection of
filtrate or nutrient removal may be required to comply with direct discharge standards (see Fact Sheet 7.1.3).
Technology Status - Many aerobic treatment units followed by filtration for surface discharge are in operation in
the u. S. today. The available field data on performance are meager, however.
Typical Equipment/No, of Mfrs. - Package aerobic unit, including tank, aeration equipment, and controls/more
than 20; dosing tank and pump/more than 5; distribution and underdrain piping/locally supplied.
Applications - Direct discharge of effluent from an aerobic unit-sand filter system is an on-site option that can
be utilized where unfavorable site or soil conditions render subsurface disposal impractical or infeasible and
where a receiving water is available.
Limitations - Studies under household conditions have shown that aerobic units are not as stable as conventional
septic tanks and periodic biological and hydraulic upsets can result in substantial variability in quality of fil-
ter influent. Although the effluent qualities of aerobic unit-sand filter and septic tank-sand filter systems
have shown to be similar for comparable loading conditions, the difference in influent organic strength can affect
filter operation in terms of required surface area, length of loading and resting periods, and maintenance. The
higher level of organic removal is obtainable with regular maintenance of aeration equipment and pumps. Filter
surfaces need to be restored or replaced when clogging occurs to avoid serious ponding conditions. Discharge
permits, with sampling and inspection, may be required by regulatory authorities.
Performance (14) - Effluent quality data from field studies of an extended aeration unit-intermittent sand filter
system with 3.8 gal/d/ft average loading rate, 0.19 mm effective size, and 3.31 uniformity coefficient:
Parameter Aerobic Unit Effluent Sand Filter Effluent
BOD_, mg/1 31.0 3.5
TSS, mg/1 41.0 9.4
Total nitrogen (N), mg/1 37.8 34.8
Ammonia-nitrogen, mg/1 1.4 0.3
Nitrate-nitrogen, mg/1 32.3 33.8
Total phosphorus (P), mg/1 29.5 20.3
Fecal coliforms, log #/l 5.3 4.0
Fecal streptococci, log #/l 4.4 3.2
Chemicals Required - None, unless chemical disinfection is required.
Residuals Generated - Sand with putrescible organic matter must be removed from filter surface when clogging
occurs. Excess sludge from aerobic unit should be wasted every 8 to 12 months. (see Fact Sheet 7.1.1)
Design Criteria - General: Design peak flow = 75 gal/d/person. Aerobic unit: Available commercial designs must
be evaluated with site specific requirements. Intermittent sand filter: design loading rate = 5 gal/d/ft ;
effective size = 0.2 to 0.6 mm; uniformity coefficient less than 4.0.
Reliability - Aerobic units are subject to biological upsets due to toxic chemical addition, surge flows, or cold
climates. Semi-skilled OSM is necessary to ensure proper functioning of modarately complex equipment. Sand
filtration is a relatively reliable process which is not greatly affected by normal pretreatment variations.
Environmental Impact - Potential for nutrient or pathogen addition to surface waters. Poorly maintained aerobic
units may produce odors. Disposal of excess sludge and sand residuals is required.
References - 14, 103, 152, 162
A-230
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AEROBIC TREATMENT AND SURFACE DISCHARGE
FACT SHEET 7.1.2
FLOW DIAGRAM -
Wastewater
Cover
Sump
Pump'
_£_
*— «•£
i
Open
W7r^/77>
•• •Orav^T~^r>
Un
^ r
— — i
.Underdrains
' I Discharge
Aerobic
Treatment Unit
Pumoing
Chamber
Intermittent
Sand
niter
I I
Disinfection
Unit
(if required)
Receivj ng
Water
ENERGY NOTES - 70u to 3600 kWh/yr for operation of aerobic unit. 50 to 250 kWh/yr for sump pump.
COSTS* - 1978 dollars; ENR Index » 2776. The following are cost estimates for an on-site surface discharge system
consisting of an aerobic treatment unit, pumping chamber, and intermittent sand filter with gravity discharge:
Construction cost:
Aerobic treatment unit, including installation $1,000 to $3,500
Pumping chamber with 1/2 hp sump pump and controls to dose filter 600 to 1,000
{optional, often included in design)
Intermittent sand filter, 50 ft surface area, with 25 ft gravity 500 to 750
discharge line (See Fact Sheet 7.1.8)
Total
Annual operation and maintenance cost:
Maintenance of aerobic unit (including sludge removal) and pumping
chamber (routine and unscheduled repairs)
Periodic raking and replacement rof sand surface to restore
hydraulic capacity of filter (every 6 months)
Power for aeration and pumping ($0.02/kWh)
Total
$2,100 to $5,250
$ 50 to $ 150
75 to 100
15 to 80
$ 140 to $ 330
Critical factors determining the cost of a sand filter include the type of filter, the amount of required surface
area, and the availability of quality filter sand, which is sensitive to location. Also, available package
filter units may significantly reduce the construction cost cited above, as can the type of aerobic unit. How-
ever, the performance of such units will not be comparable to the performance cited in this fact sheet. The
cost of surface discharge depends on site specific factors such as distance to the receiving water, ease of
excavation, and local material and labor costs. This cost increases if further pumping is required and effluent
monitoring is included.
REFERENCES - 103, 162
*To convert construction cost to capital cost see Table A-2.
A-231
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DISINFECTION FOR ON-SITE SURFACE DISCHARGE FACT SHEET 7,1,3
Description - Direct discharge to an available receiving water is an on-site alternative for the disposal of
lomestic wastewater, as discussed in Fact Sheet 7.1.8. The required level of treatment depends upon stream water
juality requirements, local regulations, and other site-specific conditions. A properly maintained aerobic treat-
ment unit or septic tank followed by a polishing sand filter is capable of producing an effluent that complies
*ith secondary treatment standards of 30 mg/1 BOD and SS. However, disinfection may be required to reduce total
and fecal coliform levels below the maximums of 1000/100 ml and 200/100 ml, respectively, recommended for recre-
ational waters.(14) Disinfection methods that have proven effective against bacterial and viral pathogens for on-
site application include tablet chlorination, iodine crystals, and ultraviolet irradiation.
rhe stacked-solid tablet feeder, with a hypochlorite storage chamber and flow-through mixing provision, followed
by a contact chamber is a typical chlorination system for small waste flows. Iodine, which is only slightly
soluble in water, is normally used in the crystalline form. A saturator holding crystals serves as the feed
ievice. The appropriate dosage to be added to the effluent can be controlled by pumping a designated sidestream
through the iodinator and reblending it with the main flow. An ultraviolet disinfection unit for on-site applica-
tion consists of a high intensity lamp in a radiation chamber, through which a thin layer of wastewater is injected
for treatment. Ultraviolet light is germicidal in the wave length range of 230 to 300 nm, with optimum efficiency
at 257 nm. The dosage of UV irradiation required depends on lamp intensity, wastewater transmissivity, exposure
time and flow pattern through the unit.
todifications - A dry feed chlorination system can be improved with the use of a surge tank and siphon or pump for
nore accurate dosage control. Ultraviolet units can be equipped with automatic cleansing devices for lamp sleeves
to maintain radiation transmission and with meters to measure intensity.
technology Status - Chlorination of wastewater has been practiced for many years. Iodine and ultraviolet irradi-
ation, which have been shown to be effective water supply disinfectants, are relatively new for on-site wastewater
treatment applications.
typical Equipment/Ho. Mfrs. - Dry feed chlorinator/approx. 10; iodine saturator/more than 2; UV disinfection unit
*ith controls/approx. 6.
applications - These on-site disinfection methods are used to destroy disease-causing organisms in the effluents
from household treatment units prior to disposal by direct discharge to meet environmental and public health
requirements.
Limitations - Dry feed chlorinators with gravity flow-through provisions lack sufficient dosage control, which can
cause excessive levels of residual chlorine to be present in final effluents. Field evaluations found the actual
dosage to be an inverse function of flow rate with an average dosage of 20 mg/1.(103) Overdosing may result from
the variability of influent flows, causing a wide range in chlorine residuals. The presence of chlorinated organic
compounds could render disinfected effluents environmentally undesirable for surface discharge. More expensive
iodine is less subject to excessive overdosing, but the environmental effect of residuals is uncertain. Power is
required by UV units for lamp operation and pumping, but residual toxicity potential is eliminated when this
disinfection method is compared to the other options. Both iodination and chlorination units must be periodically
inspected and recharged to insure sufficient protection against public health risks caused by insufficient dosing.
Homeowner performance of these tasks has been shown to be unacceptable.
Performance - Currently available, well maintained (by central authority) dry feed chlorinators, iodine saturators.
and UV units have been shown to provide consistently high levels of disinfection (greater than 97 percent reduction
of indicator organisms) of domestic wastewaters following aerobic or septic tank treatment and slow sand filtration,
Bacteria are readily killed, while viruses, spores, and cysts are somewhat more resistant. With proper halogen
dosage and contact time or sufficient ultraviolet exposure, water quality objectives (less than 200 fecal coli/100
ml) are achievable.
Chemicals Required - Calcium hypochlorite tablets, iodine crystals.
Design Criteria - Typical halogen dosage requirements for sand filtered effluents range from 1 to 5 mg/1 for
chlorine and 5 to 10 mg/1 for iodine. Contact chambers for small flow systems should be designed to provide 30
minutes of contact time at peak flow (reasonable chamber sizes are 30 to 40 gal). Disinfection requirements for
UV irradiation are based on total exposure of the liquid to the UV light energy. USPHS minimum exposure require-
ments for drinking water are 16,000 mW sec/cm . All disinfection units should be housed for protection from the
elements and vandals.
Reliability - Proper maintenance of on-site units by central authorities is necessary for effective disinfection.
Tablet chlorinators require chemical refills two to four times per year, but more frequent feed chamber cleaning may
be necessary to prevent tablet caking. UV units require periodic lamp replacement (every 7,500 hours of contin-
uous operation) and cleaning of accumulated materials Cat least 3 times per year) to restore transmissivity of the
UV lamp and sleeve. Iodination units require yearly inspection and crystal replenishment.
Environmental Impact - Chlorine disinfection can result in the production of toxic chlorinated organics in final
effluents being discharged to surface waters.
References - 14, 103, 149, 152, 162
A-232
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DISINFECTION FOR ON-SITE SURFACE DISCHARGE
FACT SHEET 7.1.3
FLOW DIAGRAM -
L'f fluent from Aerome
Unit/Septic 'T "ik a'iu
San 1 r'i li-er
Pump
Dry Feud
Chlorinator
Contact
Chamber
Pump
Iodine
Saturator
Tank
Discharge
to
Rere iv ing
Water
Ultraviolet Irradiation Unit
DISINFECTION METHODS
ENERGY NOTES - Dry feed chlorinators normally employ gravity flow-through mixing. Minimum power (50 to 250 kWh/yr)
required for small pump used with iodine saturator. Field studies indicate that power requirements for a UV unit
(2 to 4 gal/nun with 15 W lamp) range from 25 kWh/yr for intermittent operation (70 min/d) to 550 kWh/yr for con-
tinuous operation.
C°STS - 1978 dollars; i;NR Index - 2776. The following cost estimates are presented to illustrate the major com-
ponents of three on-site disinfection methods for the individual household. (Labor cost S7.50/h, including fringe
benefits):
I. Dry feed chlorination system with gravity flow-through mixing:
Construction cost: Annual operation and maintenance cost:
Chlorination unit with tablet feed chamber $200-$800 Chlorine tablets ($1.98/lb) $15-35
housing, piping, and contact chamber (The Routine maintenance require- 15-30
high end of the cost range reflects pumping.) ments (2 to 4 h/yr)
Total
$200-$800
II. lodination system with pump to maintain flow and pressure through the iodine saturator:
Total
$30-65
Construction cost:
Iodine saturator with pump and holding
tank
Total
$600-1,000
$600-1,000
Annual operation and maintenance cost:
Iodine crystals (3-5 Ib/yr @ $35-60
$11.95/lb)
Routine maintenance requirements 9-20
1-3 h/yr)
Power for pumping ($0.02/kWh) 1-5
Total
$45-85
III. Ultraviolet disinfection unit with 15W lamp and 3 gal/min operation;
Construction cost:
UV disinfection unit with controls,
surge tank, and pump
Total
Annual operation and maintenance cost:
$800-1,500 Maintenance requirements, in- $69-120
eluding lamp replacement and
radiation chamber cleaning
Power for pumping and UV 1-10
operation ($0.02/kWh)
$800-1,500 Total $70-130
NOTE - See Fact Sheet 7.1.2 and 7.1.8 for cost and energy data on aerobic and septic tank treatment followed by
sand filtration.
REFERENCES - 103, 149, 152
*To convert construction cost to capital cost see Table A-2.
A-2 3 3
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EVAPORATION LAGOONS FACT SHEET 7,1.4
Description - The evaporation lagoon may be described as an open holding facility which depends solely on climatic
conditions such as evaporation, precipitation, temperature, humidity, and wind velocity to effect dissipation
(evaporation) of on-site wastewater. Individual lagoons may be considered as an alternate means of wastewater
disposal on individual pieces of property. The basic impetus to consider this system is to allow building and
other land uses on properties which have soil conditions not conducive to the workability and acceptability of the
conventional on-site drainfield or leachbed disposal systems.
Generally, if the annual evaporation rate exceeds the annual precipitation, this method of disposal may at least
be considered. The deciding factor then becomes the required land area and holding volume. It should be noted
that for unlined on-site installations such as homes and small industrial applications, there may also be a
certain amount of infiltration or percolation in the initial period of operation. However, after a time, it may
be expected that solids deposition will eventually clog the surface to the point where infiltration is eliminated.
The potential impact of wastewater infiltration to the groundwater, and particularly on-site water supplies,
should be evaluated in any event and, if necessary, lagoon lining may be utilized to alleviate the problem.
Often preceded by septic tanks or aerobic units in order to provide a more acceptable influent to and minimize
sludge removal from the lagoon.
Technology Status - The "technology" of evaporation is well developed in terms of our scientific understanding and
application of climatological and meteorologic data.
Applications - The on-site utilization of evaporation lagoons for the disposal of domestic wastewater, from homes
and smaller industrial or commercial facilities may be applicable where access to a municipal sanitary sewer is
not available; where subsurface methods are not feasible (see Fact Sheets 7.1.5, 7.1.6, and 7.1.7); and where
effluent polishing for surface discharge is not practical (see Fact Sheet 7.1.8).
Limitations - Local health ordinances; potential for odors and health hazard when not properly designed; land area
requirements; dependence on meteorologic and climatological conditions. May require provision to add makeup water
to maintain a minimum depth during dry, hot seasons. Public access restrictions are necessary.
Performance - The performance of evaporation lagoons is necessarily site-specific; therefore, the following data
are presented on the basis of net annual evaporation rate which may exist in a certain area:
Net Annual Evaporation (inches) Lagoon Performance
(true annual evaporation - annual precipitation) (gal of water evaporated/ft /yr)
5 3.1
10 6.2
15 9.4
20 12.5
40 24.9
60 37.4
Residuals Generated - Periodic pump out of accumulated sludge is required from pretreatment unit and/or lagoon.
Design Criteria (170) - The hydraulic loading is the primary sizing criteria for an individual home total reten-
tion lagoon. In order to size the system properly the following information is needed:
a. Anticipated flow of wastewater;
b. Evaporation rates (10-yr minimum of monthly data)
c. Precipitation rates " " " "
The rate of wastewater flow may be anticipated to be in the range of 50 gallons par person per day, depending on
individual site location. Precipitation and evaporation data for most areas can be readily found in weather
bureau records. A 12-month mass balance should be utilized to properly determine design sizing. Design criteria
include: depth 2 to 4 ft; level bottom; banks more than 2 feet higher than maximum water level.
The following tables are taken from an individual retention system design for Spokane County, Washington, and are
presented here to illustrate the procedure utilized in the design of a 60.5 foot diameter lagoon.
Water Mass Balance Analysis
Month
April
May
June
Gallons
Wastewater
Flow
5400
5580
5400
Average
Evap (in.)
5.54
7.79
9.26
Average
Precip.
1.0
1.0
1.2
Net Evaporation
Gal/
Inches ft
4.54
6.79
8.06
2.83
4.23
5.02
ft to Excess
Evap Evap
Wastewater Gals
1908
1319
1076
2694
5757
8052
Process Reliability - Good, however should be closely controlled to prevent health hazard.
Environmental Impact - Potential odors; potential health hazard; land area requirements may be large; may adverse-
ly affect surrounding property values.
Reference - 170
A-234
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EVAPORATION LAGOONS
FACT SHEET 7.1.4
FLOW DIAGRAM -
Wastewater
w/^c^^^
ENERGY NOTES _ Lagoon is gravity fed from source. where pumping is required, energy requirements may be approx-
imated by using the following equation: kwh/yr = .0019 x gal/d x discharge head ft, assuming a wire to water
efficiency of 60 percent.
COSTS - 1978 dollars; ENR Index = 2776. Land costs associated with the individual total retention lagoon are
site specific and not listed here. Typical excavation and liner (plastic) costs associated with a two-bedroom
residence may be estimated as follows:
Construction cost
Excavation and hauling (750 yd )
Liner (10 mil PVC) (21,000 ft2)
Supervision and hand labor
Subtotal
Unit Price
S0.76/yd2
$0.11/ft
Cost
$ 570
2,310
620
$3,700
(To the above must be added fencing, septic tank and ancillary costs)
Operating Costs- Septic Tank Pumpout
Pumping of septic tank
Maintenance costs of lagoons not included.
REFERENCE - 170
To convert construction cost to capital cost, see Table A-2.
$10/yr
A-235
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EVAPOTRANSPI RATION SYSTEMS FACT SHEET 7.1.5
Description - Evapotranspiration (ET) is a means of on-site wastewater disposal that may be utilized in some
localities where site conditions preclude soil absorption. Evaporation of moisture from the soil surface and/or
transpiration by plants is the mechanism of ultimate disposal. Thus, in areas where the annual evaporation rate
equals or exceeds the rate of annual added moisture from rainfall and wastewater application, ET systems can
provide a means of liquid disposal without danger of surface or groundwater contamination.
If evaporation is to be continuous, three conditions must be met. First, there must be a continuous supply of
heat to meet the latent heat requirement (approximately 590 cal/g of water evaporated at 15°C). Second, a vapor
pressure gradient must exist between the evaporative surface and the atmosphere to remove vapor by diffusion,
convection, or both. Meteorological factors, such as air temperature, humidity, wind velocity, and radiation
influence both energy supply and vapor removal. Third, there must be a continuous supply of water to the evapo-
rative surface. The soil material must be fine textured enough to draw up the water from the saturated zone to
the surface by capillary action but not so fine as to restrict the rate of flow to the surface. Evapotranspira-
tion is also influenced by vegetation on the disposal field and can theoretically remove significant volumes of
effluent in late spring, summer, and early fall, particularly if large silhouette, good transpiring bushes and
trees are present.
A typical ET bed system consists of a Vt to 3 foot depth of selected sand over an impermeable plastic liner. A
perforated plastic piping system with rock cover is often used to distribute pretreated effluent in the bed. The
bed may be square-shaped on relatively flat land, or a series of trenches on slopes. The surface area of the bed
must be large enough for sufficient ET to occur to prevent the water level in the bed from rising to the surface.
Beds are preceded by septic tanks or aerobic units to provide the necessary pretreatment.
Common Modifications - Given the proper subsurface conditions, systems can be designed to perform as both evapo-
transpiration and absorption beds (See Fact Sheet 7.1.6). Nearly 3/4 of all the ET beds in operation were designed
to use both disposal methods. Mechanical evaporators have been developed, but not used at full scale.
Technology Status - There are estimated to be 4,000 to 5,000 year-round evapotranspiration beds in operation in
the United States, particularly in the semi-arid regions of the Southwest.
Typical Equipment/No, of Mfrs. (100) - Liner/24; septic tank and distribution piping/locally supplied; aerobic
unit/more than 20.
Applications - Used as an alternative to subsurface disposal in areas where these methods are either undesirable
due to groundwater pollution potential or not feasible due to certain geological or physical constraints of land.
The ET system can also be designed to supplement soil absorption for sites with slowly permeable soils. The use
of ET systems for summer homes extends the range of application, which is otherwise limited by annual ET rates.
Since summer evaporation rates are generally higher and plants with high transpiration rates are in an active
growing state, many areas of the country can utilize ET beds for this seasonal application.
Limitations - The use of an evapotranspiration system is limited by climate and its effect on the local ET rate.
In practice, lined ET bed systems are generally limited to areas of the country where pan evaporation exceeds
annual rainfall by at least 24 inches. The decrease of ET in winter at middle and high latitudes greatly limits
its use. Snow cover reflects solar radiation, which reduces ET. In addition, when temperatures are below freezing
more heat is required to change frozen water to vapor. When vegetation is dormant, both transpiration and evap-
oration are reduced. An ET system requires a large amount of land in most areas. Salt accumulation may eventually
eliminate vegetation and thus, transpiration. Bed liner (where needed) must be kept water-tight to prevent the
possibility of groundwater contamination. Therefore, proper construction methods should be employed to keep the
liner from being punctured during installation.
Performance - Performance is a function of climate conditions, volume of wastewater, and physical design of the
system. Evapotranspiration is an effective means of domestic wastewater disposal.
Chemicals Required - None
Residuals Generated - See Fact Sheet 7.1.6.
Design Criteria - Design of an evapotranspiration bed is based on the local annual weather cycle. The total
expected inflow based on household wastewater generation rate and on rainfall (use a 10 year expectancy year to
provide sufficient surface area) is compared with an average design evaporation value established from the annual
pattern. A mass balance is used to establish the storage requirements of the bed. Vegetative cover can substan-
tially increase the ET rate during the summer growing season; but may reduce evaporation during the non-growing
season. Uniform sand in the size range of D of approximately 0.10 mm is capable of raising water about 3 ft.
Liner (polyethylene) thickness typically greater than or equal to 10 mil. Surface runoff must be excluded from
the bed proximity by proper lot grading.
Reliability - An ET system that has been properly designed and constructed is an efficient method for the disposal
of pretreated wastewater and requires a minimum of maintenance.
Environmental Impact - Healthy vegetative covers aesthetically pleasing. Large land requirement conserves open
space, but limits use of land.
References - 14, 36, 103
A-236
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EVAPOTRANSPIRATIOfi SYSTEMS
FACT SHEET 7.1.5
FLOW DIAGRAM
4-inch plastic
perforated
pipe .
T
^-^<^^F&^v^rq^^u-&^oc>v»crZf^^C^c]Q
-------
SEPTIC TANK ABSORPTION BED FACT SHEET 7.1.6
Description - A septic tank followed by a soil absorption bed is the traditional on-site system for the treatment
and disposal of domestic wastewater from individual households or establishments. The system consists of a buried
tank where wastewater is collected and scum, grease, and settleable solids are removed by gravity separation, and
a sub-surface drainage system where clarified effluent percolates into the soil. Precast concrete tanks with a
capacity of 1000 gallons are commonly used for household systems. Solids are collected and stored in the tank,
forming sludge and scum layers. Anaerobic digestion occurs in these layers, reducing the overall volume. Efflu-
ent is discharged from the tank to one of three basic types of subsurface systems, adsorption trenches, seepage
bed, or seepage pits. Sizes are usually determined by percolation rates, soil characteristics, and site size and
location. Distribution pipes are laid in a field of absorption trenches to leach tank effluent over a large area.
Required absorption areas are dictated by state and local codes. Trench depth is commonly about 24 inches to
provide minimum gravel depth and earth cover. Clean, graded gravel or similar aggregate, varying in size from h
to 2S inches, should surround the distribution pipe and extend at least two inches above and six inches below the
pipe. The maintenance of at least a 2 ft separation between the bottom of the trench and the high water table is
required to minimize groundwater contamination. Piping typically consists of agricultural drain tile, vitrified
clay sewer pipe, or perforated, non-metallic pipe. Absorption systems having trenches wider than 3 ft are
referred to as seepage beds. Given the appropriate soil conditions (sandy soils), a wide bed makes more efficient
use of available land than a series of long, narrow trenches.
Common Modifications - Many different designs may be used in laying out a subsurface disposal field. In sloping
areas, serial distribution can be employed with absorption trenches by arranging the system so that each trench is
utilized to its capacity before liquid flows into the succeeding trench. A dosing tank can be used to obtain
proper wastewater distribution throughout the disposal area and give the absorption bed a chance to rest or dry
out between dosings. Providing two separate alternating beds is another method used to restore the infiltrative
capacity of a system. Aerobic units may be substituted for septic tanks with no changes in soil absorption system
requirements (see Fact Sheet 7.1.1).
Technology Status - Septic tank-soil absorption systems are the most widely used method of on-site domestic waste
disposal. Almost one-third of the United States population depends on such systems.
Typical Equipment/No, of Mfrs. - Septic tanks and distribution piping are locally supplied.
Applications - Used primarily in rural and suburban areas where economics are favorable. Properly designed and
installed systems require a minimum of maintenance and can operate in all climates.
Limitations - Dependent on soil and site conditions, the ability of the soil to absorb liquid, depth to ground-
water, nature of and depth to bedrock, seasonal flooding, and distance to well or surface water. A percolation
rate of 60 min/in is often used as the lower limit of permeability. The limiting value for seasonal high ground-
water should be 2 ft below the bottom of the drainfield. When a soil system loses its capacity to absorb septic
tank effluent, there is a potential for effluent surfacing, which often results in odors and, possibly, health
hazards.
Performance - Performance is a function of the design of the system components, construction techniques employed,
rate of hydraulic loading, areal geology and topography, physical and chemical composition of the soil mantle, and
care given to periodic maintenance. Pollutants are removed from the effluent by natural adsorption and biological
processes in the soil zone adjacent to the field. BOD, SS, bacteria, and viruses, along with heavy metals and
complex organic compounds, are adsorbed by soil under proper conditions. However, chlorides and nitrates may
readily penetrate coarser, aerated soils to groundwater.
Residuals Generated - The sludge and scum layers accumulated in a septic tank must be removed every 3 to 5 years.
(See Fact Sheet 7.1.9)
Design criteria (134) - Absorption area requirements for individual residences:
2 2
Percolation Rate (min/in) Reg. Area/Bedroom (ft ) Percolation Bate (min/in) Reg. Area/Bedroom (ft )
1 or less 70 15 190
3 100 30 250
5 125 45 300
10 165 60 330
Process Reliability - Properly designed, constructed, and operated septic tank systems have demonstrated an
efficient and economical alternative to public sewer systems, particularly in rural and sparsely developed areas.
System life for properly sited, designed, installed and maintained systems may equal ot exceed 20 years.
Environmental Impact - Leachate can contaminate groundwaters when pollutants are not effectively removed by the
soil system. In many well aerated soils, significant densities of homes with septic tank - soil absorption
systems have resulted in increasing nitrate content of the ground water. Soil clogging may result in surface
ponding with potential aesthetic and public health problems.
References - 12, 14, 36, 134, 135
A-238
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SEPTIC TANK ABSORPTION BED
FACT SHEET 7,1.6
FLOW DIAGRAM - (typical)
INLET
OUTLET
SEPTIC TANK
(PROFILE)
' TILE DRAINAGE
LINES
V ABSORPTION
TRENCHES
ABSORPTION FIELD
(PLAN)
Tar paper joint covering
Marsh hay, fabric or untreated
building paper
Gravel
fil, „<„ &8gS
-------
SEPTIC TANK MOUND SYSTEMS FACT SHEET 7.1.7
Description - A septic tank and mound system is a method of on-site treatment and disposal of domestic wastewater
that can be used as an alternative to the conventional septic tank-soil absorption system. (See Fact Sheet
7.1.6.) In areas where problem soil conditions preclude the use of subsurface trenches or seepage beds, mounds can
be installed to raise the absorption field above ground, provide treatment, and distribute the wastewater to the
underlying soil over a wide area in a uniform manner.
The three main elements of the system are the septic tank, dosing chamber, and the mound. The relative dimensions
and location of the septic tank, the type of control structures, the size and loading of inspection ports, and the
materials of construction are dictated by State and local codes. A pressure distribution network should be used
for uniform application of clarified tank effluent to the mound. A subsurface chamber can be installed with a
pump and high water alarm to dose the mound through a series of perforated pipes. Where sufficient head is
available, a dosing siphon may be used.
The design of a mound is based on the expected daily wastewater volume it will receive and the natural soil
characteristics. As with the conventional subsurface disposal system, pollutants are removed by natural adsorp-
tion and biological processes in the soil zone adjacent to the seepage bed. The mound must provide an adequate
amount of unsaturated soil and spread septic tank effluent over a wide enough area so that distribution and
purification can be effected before the water table is reached.
A clean, medium sand is normally used as fill in which gravel trenches or beds are excavated consisting of 1 to 1*5
inch stones to surround distribution pipes. As in any seepage system, a clogging mat will develop at the gravel-
sand interface. The equilibrium flow rate through this zone has been shown to be 1.25 gpd/ft . Sufficient inter-
facial area must therefore be available for the design flow. The total effective basal area of the mound must be
sized to permit the effluent to percolate into the native soil. Infiltration rates into the natural soil are
based on the hydraulic conductivity characteristics of the least permeable soil horizon below the proposed site.
Common Modifications - Different types and arrangements of seepage systems may be installed within a mound,
depending upon the characteristics of the underlying soil. One or more trenches may be used above wet, slowly
permeable subsoil to spread percolating liquid over a large area and to prevent ponding. When the permeability of
the natural soil is not a limiting factor, rectangular seepage beds are usually more suitable than trenches.
Although some mound designs do not employ dosing systems, these designs are not normally suitable for proper
performance of a mound.
Technology Status - Septic tank mound systems have proven to be successful alternatives for difficult soil condi-
tions. They have been in use for more than twenty years in various forms and for nearly ten years with the design
described herein.
Typical Equipment/No, of Mfrs. - Pump chamber with controls/more than 50; Septic tank and piping/locally supplied.
Applications - Used as alternative to septic tank-soil absorption system in problem soil conditions. Spreads
percolating liquid over wide area to slowly permeable (60-120 min/in percolation rate) subsoil. Increases amount
of soil over shallow, permeable subsoil on creviced bedrock or high water table to provide sufficient contact time
for purification before effluent reaches groundwater.
Limitations - Requires more space and periodic maintenance than conventional subsurface disposal system, along
with higher construction costs. System cannot be installed on steep slopes, nor over highly ( 120 min/in.)
impermeable subsurface. Seasonal high groundwater must be deeper than two feet to prevent surfacing at the edge of
the mound. Pumping is usually required to distribute tank effluent throughout mound, necessitating O/M require-
ments.
Performance - As with other soil absorption systems, performance is a function of several factors, including
design, construction, maintenance, waste characteristics, and soil conditions. BOD, SS, heavy metals, complex
organic compounds, bacteria, and viruses are effectively removed by soil under proper conditions. However,
nitrates are unaffected and often discharged to groundwaters.
Chemicals Required - None.
Residuals Generated - Septage is generated, requiring treatment and disposal. See Fact Sheet 7.1.9. Volume equal
to septic tank capacity every 3 to 5 years.
Design Criteria - Design flow basis: 75 gal/person/d; 150 gal/bedroom/d. Basal area based on percolation rates
up to 120 min/in. Mound height at center approximately 3.5 to 5 ft. Pump (centrifugal) must accommodate appro-
ximately 30 gal/min at required TDK. Pump controls: level or timer.
Process Reliability - Septic tank-mound systems that are properly designed and constructed are viable alter-
natives to centralized treatment facilities. Dosing equipment should be routinely maintained, and septic tanks
must be periodically pumped out for systems to operate effectively. Long term service life data is not available
as yet, but projections suggest mound life to be about the same as that of properly designed soil system.
Environmental Impact - Visual impact can raise major aesthetic issues, particularly in suburban areas/ due to the
shape, size and proximity of mound systems. Drainage patterns and land use flexibility may also be affected.
References - 14, 36, 134, 135
A-240
-------
SEPTIC TANK MOUND SYS1EMS
FACT SHEET 7.1.7
Sand fill
Topsoi1
I I' ll \\Stom-fill ' X .
('lowed surface
"Hiqh water
alarm switch
Pump with controls
SEPTIC TANK
PIlMrlNI, CHAMBER
MOUND
ENERGY NOTES - Minimum power
(50 to 250 kWh/yr) required
to operate small sump pump for
cosing mound.
i T ^
. SEEPAGE TRENC
5/8 to 1 inch stone\
I 1 inch perforated
1 PVC pipev """
-\-, -,
— i ppe
— I cvrzi.~ir~.rz.~ir.
I i
l>j to 2 inch PVC pipe
PLAN VIFW
COSTS* - 1978 dollars; ENR Index = 2776. The following site specific costs serve to illustrate the major com-
ponents of a 300 gal/d household mound with two level trenches 3 x 41 ft, 65 x 42 ft basal area, and a peak
mcund height of 3.5 ft.
Construction Cost
Building sewer and 1000 gal septic tank, design and permit
Pumping chamber with 1/2 hp sump pump and controls ($600 to $1000)
Mound system
Total
Annual Operating and Maintenance Cost
Operation and maintenance of pumping chamber ($20 to $50 per year)
Pumping septage from septic tank (every 3 to 5 years)
Total
$ 700
800
2,400
$3,900
30
15
45
The construction cost for this mound system includes 12 tons gravel, 265 tons sand, 110 tons clay fill/topsoil, 48
ft of 2-in PVC pipe, 82 ft of 1-in perforated PVC pipe, hay to cover trenches, and labor. This cost can vary
significantly depending upon site characteristics and local material and labor costs. Mound systems of this type
are quoted to cost anywhere from $2,500 to $5,000. The range of mound costs has also been expressed as $0.75 to
$3.0C/ft of basal area.
REFERENCES - 14, 103
*Tr convert construction cost to capital cost see Table A-2.
A-241
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SEPTIC TANK POLISHING, SURFACE DISCHARGE FACT SHEET 7.1.8
Description - Surface discharge of septic tank effluent is a method of on-site disposal of domestic wastewater
that can be used as an alternative to the conventional soil absorption system (See Fact Sheet 7.1.6). Where
permitted by code, surface discharge units can be employed in areas where subsurface disposal systems are not
feasible. Since septic tank effluent quality is clearly unacceptable for direct discharge, additional processing
is required which should be consistent with the principles of on-site treatment, i.e., simplicity and low O/M.
Filtration, with its positive removal mechanisms, is particularly well suited for this purpose. Sand filter
trenches are similar to absorption trenches, but contain an intermediate layer of sand as filtering material and
underdrains for carrying off the filtered sewage. Buried sand filters, which require less area than trenches, are
typically installed with underdrains in 1 ft of coarse gravel, covered with 2 ft of sand (0.4 to 0.6mm effective
size with uniformity coefficient less than 4.0), followed by influent drain tile or perforated pipe in another
foot of gravel, and covered with at least 6 in of topsoil. Intermittent slow sand filters are divided into two or
more units, which are alternately loaded and rested. Wastewater is applied over a bed of sand (0.2 to 0.6 mm
effective size with uniformity coefficient less than 4.0) 2 to 3 ft deep and the filtrate is collected by under-
drains contained in a layer of gravel. The sand remains aerobic and serves as a biological filter, removing SS
and dissolved organics. Because of smaller sand size and higher loading rates, these units require accessibility
for periodic servicing. The recirculating filter system consists of a septic tank and a recirculation tank,
containing a timer-controlled sump pump for dosing onto a sand filter. The filter bed contains 3 ft of coarse
sand (0.6 to 1.5mm effective size with less than 2.5 uniformity coefficient) and 1 ft of gravel surrounding the
underdrain system. A recirculation ratio of 4:1 (recycled filter effluent to forward flow) is recommended. If
the tank effluent requires disinfection, alternatives that are likely with on-site systems include tablet chlor-
ination, iodine crystals, and ultraviolet irradiation. (See Fact Sheet 7.1.3.)
Common Modifications - Buried sand filters should be constructed in two sections, which are dosed separately by a
tank with alternating siphons. Above ground sand filters (intermittent or recirculating) can be installed in
areas where subsurface construction is impossible. Dosing tanks and pumps feed these filters, which may be open
or covered, but must be accessible for cleaning. Covering and insulation are recommended for intermittent and
recirculating filters to minimize freezing in cold weather and potential health risks and nuisances in warm
weather.
Technology Status - Sand filtration has traditionally been employed to treat septic tank effluent. The recircu-
lating and sand filter is a relatively new type of on-site filter, but has enjoyed success in Illinois and Oregon.
Typical Equipment/No, of Mfrs. - Septic tank and distribution piping/locally supplied; dosing tank and pump/more
than 5; dry chlorine feeder/approx. 10; iodination unit/more than 2; UV water purification unit/approx. 6.
Applications - Surface discharge systems are alternative designs to be used where site conditions, including
geology, hydrology, and lot size, preclude the use of the soil as a treatment and disposal medium. Centralized
management, rather than homeowners, are normally required for successful operation.
Limitations - Because of additional processing involved, these systems are more expensive than conventional on-
site systems. Filter surfaces and disinfection equipment require periodic maintenance. Buried sand beds are
inaccessible. Power is required for pumping and some disinfection units. State or Federal discharge permits
along with sampling and monitoring are required.
Performance (14)- Effluent quality data from experimental septic tank-intermittent sand filter systems with 5
gal/d/ft average loading rate, 0.45mm effective size, and 3.0 uniformity coefficient:
Parameter Septic Tank Effluent Sand Filter Effluent Chlorinated Effluent
BOD, mg/1 123 9 3
TSS, mg/1 48 6 6
Total nitrogen (N), mg/1 23.9 24.5 19.9
Ammonia-nitrogen, mg/1 19.2 1.0 1.6
Nitrate-nitrogen, mg/1 .3 20.0 18.9
Total phosphorus (P), mg/1 10.g 9.0 8.4
Fecal coliforms (number per 100 ml) 5.9 x 105 1.1.x 10* 2
Total coliforms (number per 100 ml) 9.0 x 10 6.5 x 10 3
Residuals Generated - See Fact Sheet 7.1.9 for septic tank residuals. .Sand with putrescible organic matter must
be removed from intermittent and recirculating filter surfaces when clogging occurs and may be buried on-site or
require off-site disposal.
Design Criteria - Recommended loading rates in gal/d/ft : Buried sand filter 0.75 to 1.5, intermittent sand
filter 5, recirculating sand filter 3 (based on forward flow alone).
Reliability - Sand filters perform well, unless overloaded. Periodic inspection is required to obtain proper
functioning of chlorination, UV, and iodination units. (See Fact Sheet 7.1.3).
Environmental Impact - Treated effluents are discharged to surface waters. Processing and disposal of septage is
required. Odors may emanate from open filters, and potential health risks increase without proper fencing or
other access control.
References - 14, 36, 103, 134
A-242
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SEPTIC TANK POLISHING, SURFACE DISCHARGE
FACT SHEET 7.1.8
FLOW DIAGRAM -
I r
•s
Pimping Chamber
Intermittent
Sand Filter
_^J)ischarge
T
I with or without
» Recirculation Tank
Recirculating
Sand Filter
is infection
ENERGY NOTES - Minimum power (50 to 250 kWh/yr) required for operation of small sump pump for dosing intermittent
slow sand filter and recirculating sand filter. Dosing siphons are often used with buried sand filters.
COSTS* - 1978 dollars; ENR Index = 2776. The following site specific costs serve to illustrate the major com-
ponents of three types of filters normally employed to treat septic tank effluent for on-site, surface discharge.
I. Buried sand filter: 300 gal/d; 17 ft x 17 ft filter; vertical profile of 12 in. gravel, 2 ft sand and 12 in.
gravel;2 ft soil cover for depth necessary to operate dosing siphon; 25 ft from discharge.
Construction cost: , Annual operation and maintenance cost:
Excavation, backf ill, hauling (^60 yd ) $ 400 None
Sand (22 yd ) and gravel (22 yd ) 200
Filter pipe (100 ft) and ancillary pipe (25 ft) 100
Siphon 500
Supervision and labor 300
Total $1,500
The construction cost for the buried sand filter above lies at the low end of a reported range of $1,500 to
$3,000 for these units. However, dual systems are recommended because of their permanence and inaccessibility.
cessibility.
Annual operation and maintenance cost:
Pumping chamber maintenance and
restoration of filter capacity $100-150
II. Intermittent slow sand filter: 250 gal/d; two 50 ft covered filters; vertical profile of 30 in. sand and
16 in. gravel; pump dosing system; 25 ft from discharge.
Construction cost:
Excavation 140 yd ) $ 30
Sand (10 yd ) and gravel (5 yd ) 70
Filter pipe (100 ft) and ancillary pipe (25 ft) 80
Two 1500 gal tanks for filter housing 600
Insulated covers, splash plates, etc. 220
Pump chamber with 1/2 hp sump pump and controls 800
Supervision and labor 200
Total $2,000
The construction cost of the above sand filter, without the pump chamber, is $12/ft , which is consistent
with a reported range of $10 to $15/ft . In mild climates, it is possible that an excavated, plastic-
lined housing could be substituted for the tanks included above.
2
III. Recirculating sand filter: 300 gal/d; 100 ft open filter; vertical profile 3 ft sand and 1 ft gravel;
25 ft from discharge.
Construction cost: Annual operation and maintenance cost:
Pump maintenance and
restoration of filter capacity $50 - $100
Excavation 122 yd ) $ 20
Sand (12 yd ) and gravel (4 yd ) 80
Internal (100 ft) and external (25 ft) piping 100
Recirculation tank (1000 gal) 250
Filter housing 600
Pump, controls, fittings 450
Supervision and labor 200
Total $1,700
The construction cost for the above recirculating sand filter does not include the cost of covers and
insulation, which will be required for cold weather application.
NOTE - See Fact Sheets 7.1.3 and 7.1.6 for disinfection and septic tank cost and energy data.
REFERENCES - 14, 103
'*To convert construction cost to capital cost see Table A-2.
A-243
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SEPTAGE TREATMENT AND DISPOSAL FACT SHEET 7.1.9
Description - Common methods of septage treatment and disposal include land application, disposal at wastewater
treatment plants, and disposal at separate septage treatment facilities. Septage is a highly variable, high
strength organic slurry characterized by an obnoxious odor, resistance to settling and dewatering, potential to
foam, and often significant contents of grease, grit and hair. The concentration of metals is considerably lower
than that of domestic sludge; consequently, heavy metals in septage do not constitute a serious problem. Signifi-
cant numbers of indicator organisms and pathogens may be found in septage. Several parasites have also been
identified in septage. Proper handling, treatment, and disposal of septage is necessary to eliminate a potential
threat to public health.
Land Disposal - Septage is applied to land by the same methods used for disposal of municipal treatment plant
sludge. Fact Sheets which are most applicable to land disposal of septage are: Land Application of Sludge
(6.1.3) and Sludge Lagoons (6.1.11). Septage is also disposed of at landfills by a variety of techniques. How-
ever, the low solids content of septage often makes this practice undesirable.
Disposal at Sewage Treatment Plants - Septage treatment and disposal is achieved by addition to the plant liquid
or sludge streams at various points in the process train. For plants with primary clarification, addition upstream
of the clarifier is preferable, as it effectively achieves septage solids concentration and incorporation into the
sludge stream without upsetting effluent quality. Other plant configurations may require direct addition to the
biological treatment process or to sludge handling processes such as thickening, digestion, dewatering, etc.
Addition of septage to the liquid stream of a wastewater treatment plant may cause upsets in plant performance due
to temporary hydraulic or organic overloads, clogging or fouling of plant equipment, or by exceeding the solids
handling capacity of the plant. For this reason, a septage receiving station may be added to allow easy and safe
transfer of septage from the hauler truck, to provide some form of pretreatment (e.g., screening) to protect
equipment, and to allow controlled addition from a holding tank into the desired process. Most wastewater treat-
ment processes are able to treat septage; however, some are more effective than others. Conventional activated
sludge, preceded by a buffering primary clarifier, can effectively treat septage. Extended aeration plants of
sufficient capacity are able to handle septage relatively well. Trickling filter plants are potential acceptors
of septage; however, odor generation, filter fly proliferation, and media clogging may be a problem at increased
organic loading. Contact stabilization processes without primary clarification appear to be least amenable to
septage treatment due to short contact time. Septage addition to the reaeration zone or digester would be the
preferred approach for such plants. Addition of septage to the sludge stream of a wastewater treatment plant
avoids possible problems with pumping, biological overloading, and greater sludge volumes for final disposal.
Fact Sheets applicable to disposal of septage at wastewater treatment plants are: Clarifier, Primary, Circular
with Pump (3.1.1); Clarifier, Primary, Rectangular with Pump (3.1.2); Activated Sludge, Conventional, Diffused
Aeration (2.1.1); Activated Sludge, Conventional, Mechanical Aeration (2.1.2); Activated Sludge with Nitrification
(2.1.6); Contact Stabilization, Diffused Aeration (2.1.8); Extended Aeration, Mechanical and Diffused Aeration
(2.1.10); Lagoons, Aerated (2.1.11); Oxidation Ditch (2.1.15); Trickling Filter, Plastic Media (2.2.6); Trickling
Filter, High Rate, Rock Media (2.2.7); Trickling Filter, Low Rate, Rock Media (2.2.8).
Disposal at Separate Facilities - In rural areas where land disposal is not feasible and no wastewater treatment
plant is available, septage may be collected and treated at separate septage treatment facilities. Several con-
ventional processes for treating sludge can be used to stabilize and dispose of septage. Supernatant from sepa-
ration processes must be treated prior to disposal. Applicable processes and Fact Sheets are: Sludge Lagoons
(6.1.11); Lime Stabilization (6.4.8); Composting (6.2.3, 6.2.4); Chemical Treatment (4.3.1); Dewatering (6.3.1,
6.3.2, 6.3.3, 6.3.4, 6.3.5, 6.3.9). In addition, chlorine oxidation for stabilization of septage has also been
used.
Technology Status - Land disposal practice for septage is generally uncontrolled surface application on remote
land with little or no stabilization. Land application of septage is by far the most widely used means of septage
disposal. Estimates regarding fraction of septage disposed of on land range from 60-90 percent of total septage
generated. Septage disposal at the treatment plant is limited to plants which have excess capacity to handle the
additional solids and BOD load due to septage. Disposal at treatment plants is estimated to account for up to 25
percent of the total septage slated for disposal. Septage treatment and disposal at separate facilities is prac-
ticed in areas where high densities of septic tank systems exist and large volumes of septage are handled. Chem-
ical treatment, composting, and lagoons are in full-scale use. Some septage treatment methods have not gained
economic acceptance. Septage has also been improperly disposed of by surreptitious disposal into sewers, receiv-
ing streams, or by dumping on land.
Limitations - Refer to individual fact sheets referenced above.
Design Criteria - Septage generation rates for a particular area may be estimated by several methods. Accurate
records kept by septage haulers may provide reasonable estimates of annual septage production rate. Alterna-
tively, assuming the number of dwellings using septic tanks is known, a tank volume (e.g., 1000 gal) and pumping
frequency (e.g., every 4 years) can be assumed, allowing a simple calculation of generation rates (e.g., 500 homes
x 1000 gal/4 years = 125,000 gal/yr). A crude estimate of septage generation rate may be made by assuming a per
capita septage production of 60-80 gal/cap/year.
Typical characteristics of domestic septage are: TS - 3,600-106,000 mg/1; SS - 1,770-22,600 mg/1; BOD^ - 1,460-
18,600 mg/1; COD - 2,200-190,000 mg/1; TKN - 66-1,560 mg/1; NH -N 6-385 mg/1; Total P - 24-760 mg/1; Grease -
604-23,468 mg/1. As indicated, septage characteristics are highly variable.
Environmental Impact - Refer to individual fact sheets referenced above.
References - 12, 14, 135, 234, 235, 236-258
A-244
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SEPTAGE TREATMENT AND DISPOSAL
FACT SHEET 7.1.9
FLOW DIAGRAMS - Refer to individual fact sheets referenced in text for flow diagrams of pertinent processes.
ENERGY NOTES - Refer to individual fact sheets referenced in text for energy requirements for various methods of
septage treatment and disposal.
COSTS* (1st quarter 1978 dollars); ENR = 2681
Septage Treatment and/or Cost per 1000 gal
Disposal Method
Land Application
Surface Spreading
Subsurface Disposal
Trench Disposal
of Septage
$1.25-$17.00
$20-$35
$20-$30
Sanitary Landfill Disposal $5-$10
Disposal at Wastewater
Treatment Plants
$20-$30
Separate Septage Facilities
Lagoon Disposal $5-$20
Lime Stabilization
Chlorine Oxidation
Composting
Chemical Treatment/
Dewatering
REFERENCE - 234
$10-$20
$30-$35
$30-$60
530-$60
$30-$50
Transportation costs incurred by septage hauler to and
from the disposal site not included.
Transportation costs not included.
Transportation costs not included. Site life is assumed
to be 10 years. Facility capacity varies from 100,000
gal/yr to 250,000 gal/yr.
Accurate cost data not available. Septage often not
accepted at landfills due to low solids content.
Costs shown are total treatment costs, including
amortization of capital expenditure for a receiving
station.
Costs may vary considerably depending upon land
costs and costs of solids removal from lagoon.
Includes land spreading of limed liquid sludge.
Includes sand drying bed dewatering.
Process has high chlorine requirement and the
operating costs are dependent on fluctuations in the
price of chlorine.
Revenues from sale of compost product not included. Unit
cost of bulking materials may be critical. Dewatering prior
to composting may be desirable.
Includes costs of chemical clarification, solids condition-
ing/dewatering, and effluent polishing/disposal.
*To convert construction cost to capital cost see Table A-2.
A-245
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IN-THE-HOME TREATMENT AND RECYCLE FACT SHEET 7,2.1
Description - The waste stream from one or more household fixtures can be treated to provide the water supply for
water uses, such as laundry, toilet, lawn sprinkling, car washing, etc. The primary purpose of the in-the-home-
treatment and recycle system is to reduce the quantity of water used and/or wastewater generated. Numerous waste-
water reuse options are available. Recycle systems are presently marketed which involve the treatment of various
fractions of the waste stream to satisfy a variety of uses. One purports to have a complete recycle-closed loop
process. However, little reliability and cost data are available. A system can be assembled from existing
components.
Treatment methods for recycle include ion exchange, aeration, adsorption, clarification, filtration and disin-
fection. One of the major options involves the recycling of bathing and laundry water for flushing of water
carriage toilets (BL/T). This system may consist of a holding tank, filtration device (paper cartridge, sand,
diatomaceous earth, etc.), a disinfection process (chlorine or iodine), and a pump-pressure tank combination for
supplying the treated water. Makeup water (tap water) is brought in as required when demand exceeds supply. In
general, pressurized media filtration systems are of moderate hardware complexity and require maintenance per-
formed by semi-skilled servicemen. Routine adjustment of filtration equipment generally is required two to four
times per year. Unscheduled maintenance is required infrequently. Disinfection is necessary to control odors and
bacterial growth. The most common type of disinfection feeder for small waste flows has been the stacked-solid
tablet feeder employing Ca(OCl)2- Dosage is controlled by flow control weirs or by diversion of a portion of the
waste through the unit. See Fact sheet 7.1.3. Maintenance also includes cleaning of storage reservoirs, mainten-
ance of mechanical equipment, including pumps and residual disposal.
Modifications - Numerous options for recycle and reuse are possible. Most systems which recycle to the toilet are
dyed in some manner for aesthetic reasons.
Technology Status - Many complete systems are currently being tested. Most systems are assembled from existing
components.
Typical Equipment/No. Mfrs. (23) - Filters/20; tanks/2; pumps/34; automatic feeders/4; controls/310; disinfection
units/more than 15; ion exchange equipment/15.
Applications - A flow reduction measure, which is suitable for increasing the life or improving the performance of
on-site soil disposal systems. It occasionally permits the use of subsurface disposal systems where available
land area is very limited but soils have acceptable percolation characteristics or where land is available with a
limited ability to accept wastewater. Involves semi-skilled to skilled labor, depending on system.
Limitations - Operation and maintenance requirements are substantial and should be performed by centralized man-
agement personnel to prevent potential health risks.
Performance - Variable levels of flow reduction and treatment are achieved depending upon system developed.
Recycling bath and laundry wastes to toilet (BL/T) reduces flow about 30 to 35 percent. Analysis of bath and
laundry wastewaters after filtration through three units is summarized below: (159)
Filter System Average Effluent Turbidity, ppm Average Effluent Suspended Solids, mg/1
Diatomite 23 21
Cartridge, Surface Type 60 31
Cartridge, Depth Type 62 43
Chemicals Required - Disinfectants; may require coagulants, polymers for solids and scale control.
Residuals Generated - Sludge, scum.
Design Criteria - The following reuse water quality objectives are suggested to determine the level of wastewater
treatment necessary prior to on-site reuse. (152)
Suggested Reuse Water Quality Criteria
Grade BOD (mg/1) SS (mg/1) Turbidity (TU)
Toilet Flushing 20 20 25
Utility (lawn watering, irrigation, car 15 15 20
and house washing, toilet flushing)
Body Contact (laundry, shower, fire 10 10 1
fighting, plus all of the above)
There should be no disagreeable colors, odors or visible oil and grease; pH 6.5-8.5; and caution should be used in
lawn watering, irrigation, etc., owing to certain constituents, e.g., boron which adversely affects plant growth.
Process Reliability - Reliability data on recycle systems not available, but significant maintenance can be anti-
cipated as a direct function of system complexity.
Environmental Impact - Odors may be generated and water quality may be aesthetically objectionable when systems
malfunction or are overstressed. User acceptance may be difficult. Potential health risks exist but may be kept
at an acceptable level by proper centralized arrangements.
References - 149, 152, 159
A-246
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IN-THE-HOME TREATMENT AND RECYCLE
FACT SHEET 7,2.1
FLOW DIAGRAM
Numerous recycling options are possible. One example is given below:
Disinfectant
Feeder
Bath and
aundrv Wastes
Storage
Tank
Filter
Pressure
Tank
Makeup Water
» To toilet or lawn
* Overflow to disposal
ENERGY NOTES - Minimum power (60 to 600 kWh/yr) required for operation of small pump.
COSTS* - 1974 dollars; ENR = 2020.
Prototype Recycle Systems Projection for Mass Produced Recycle System
Diatomite Filter Cartridge Filter Diatomite Filter
Installed Cost
Storage system $175 $175 $ 70
Filter 135 60 100
Pressurization system 115 115 85
Disinfectant feeder 20 20 20
Valves, pipe, fittings 95 80 75
Total Material Cost 540 450 350
Labor Cost 100 90 50_
Total $640 $540 $400
Costs of system housing and major retrofitting requirements are not included.
Annual Operating Cost
Filter Media 3.50 38.80 3.50
Electric Power 12.00 1.20 7.00
Disinfectant 5.50 5.50 5.50
Total $21.00 $45.50 $16.00
Electric Costs = $.02 kWh. Calculations based on a 16-h "on", 8-h "off" cycle for the recirculation pump.
Total Annual Cost
15
Expected life, yrs
Total Cost/yr
15
$63.50
15
$81.50
$43.00
Installation of a recycle system for toilet flushwater can result in a cost saving in the installation of on-site
disposal systems since there are reduced capacity requirements. Assuming a 1/3 reduction in flow, the following
savings can be realized: (103)
Disposal Method
Costs without Recycling minus Costs with Recycling equals Saving
Septic Tank-Soil Adsorption System $2275 (1000 ft )
Septic Tank-Evapotranspiration 5000 (5000 ft )
Septic Tank-Intermittent Sand 2800 (100 ft )
Filter
$1775 (667 ft 1
3600 (3333 ft )
2500 (67 ft )
$ 500
1400
300
Water costs would generally be reduced, but exact figures are site specific.
REFERENCES - 103, 149, 159
*To convert construction cost to capital cost see Table A-2.
A-247
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NON-WATER CARRIAGE TOILETS FACT SHEET 7.2.2
Description - Non-water carriage toilets serve to eliminate the toilet contribution (black wastes) to the house-
hold wastewater. Methods include: thermal (incineration, evaporation-condensation), freezing, oil recirculating,
composting (small, large), holding (packaging). Descriptions of those systems for which there is available on-
site hardware and performance information follow:
Incinerating Toilets - Small self-contained units which utilize the process of incineration to volatilize the
organic components of solid wastes and evaporate the liquid. Wastes are deposited into a combustion chamber and
are incinerated upon a signal. The process is fueled by gas, fuel oil or electricity. Units are equipped with
appropriate exhaust gas vent and blower. Ash residue should be removed using a vacuum cleaner or dustpan and
brush once/wk. Routine cleaning of toilet bowl or replacement of toilet bowl liner is required.
Composting Toilets - Organic matter from feces, urine and sometimes garbage undergoes aerobic composting and
is converted to humus which may be dispersed on the soil. Two basic varieties of toilet systems are available,
those in which the point of use is removed from the decomposition chamber (separated) and those in which the point
of use is directly attached to the chamber (non-separated). Separated units are generally larger and rely on low
rate, generally aerobic biological action. The non-separated units are equipped with an electric heating element
and a mechanical stirring mechanism. These smaller units depend upon both thermal dehydration and high rate
aerobic biological activity. Operation and maintenance requirements: Separate units - removal of compost residue
approximately once/yr; periodic addition of organic solids to prevent compost mass compaction may be required, and
infrequent maintenance of mechanical parts. Non-separated units - removal of compost residue at least 4 times/yr;
mixing of compost daily; periodic maintenance of mechanical parts including fan, heater and stirrers.
Oil Recirculating Toilets - Toilet wastes are carried by a recirculating petroleum base flushing liquid,
separated, and stored for subsequent removal and disposal. System requirements include toilet bowl, waste sepa-
ration and purification system, pump and controls. Removal and disposal of residuals is required annually.
Maintenance includes the replacement of exhausted adsorbent, disinfection and filtration media and lost flushing
oil. With all non-water carriage toilets, the remaining household wastewater (65 to 70 percent of combined
volume) must be treated and disposed of in an environmentally acceptable manner.
Technology Status - Relatively new. Evaluation of performance in households is inadequate in United States.
applications - Non-water carriage toilets, as part of total household wastewater alternative, may be economically
viable in areas where water supplies are limited and other wastewater alternatives are environmentally limited.
Limitations - Incinerating toilets, gas and oil fired require more frequent maintenance than electric; electric
have higher energy costs. Toilet capacity less than or equal to 3 uses/h. Composting - non-separated unit is
subject to hydraulic overloads and has a unit capacity less than or equal to 3 persons. Larger, separated units
have a capacity less than or equal to 5 persons. Continuous nature of both process types provides potential for
short circuiting and contamination of stabilized compost by "fresh" waste materials. Oil recirculating - large
space requirements. Incomplete separation of aqueous base liquids from flushing oil due to the formation of oil-
water emulsions. Flushing oil deteriorates. Costs are quite high. All units are limited to toilet wastes (1/3
total waste flow), and graywater treatment and disposal must be provided. Also, user acceptance is an important
factor. All systems require commitment of the user to sustain the process.
Typical Equipment/No. Mfrs. - Incinerating/more than 8; small composting/more than 12, large composting/more than
3, oil recirculating/more than 3.
Performance (14) - The effect of eliminating blackwater from household wastewater discharges (% reduction): Flow
30 to 35; BOD, 10 to 35; SS, 20 to 60; Total P, 15 to 40; TKN, 40 to 90; Pathogenic organisms, considerable.
Chemicals Required - Incinerating - none. Composting - peat "starters" are normally required to maintain good
moisture distribution, prevent compaction and facilitate aeration; fibrous dry organic materials are added per-
moisture distribution, prevent compaction ana racumane aeration; iicrous ary urganxc materxcixs aie auueu pei-
iodically with separated type. Oil recirculation - Makeup oil (up to 8 gal/yr) may be required; filter, coa-
lescer, adsorbent and disinfectant cartridges.
Residuals - Incinerating - an inert sterile ash; Composting - a humus suitable as a soil conditioner; Oil recircu-
lating - oil coated residue, exhausted filtration media.
Design Criteria (149) - Typical toilet waste loadings (g/cap/d): BOD, 16.7; SS, 27; TKN, 8.7; Total P, 1.2;
Incinerating - gas fired requires propane or natural gas, combustion/cooling cycle 20-25 minutes; electric unit
requires 115 or 220 volts AC or 12 volts DC, combustion/cooling cycle 45 minutes; Composting - separated unit
space requirement 30 to 70 ft ; non-separated unit requires 2 to 5 ft ; Oil recirculation - 53 ft holding tank
space requirement.
Environmental Impact - Commitment of water resources to toilet is eliminated; volume and pollutant ioadings to on-
site disposal systems are reduced. Incinerating - potential odor or air pollution problems, potential fire or
explosion hazard, high energy use; Composting - nutrient elements in sewage are conserved, potential odor problems
and health hazards due to vectors and incompletely composted residue contacts; Oil recirculating - potential odor
and discoloration problems; disposal of residuals may be a problem due to their oily character.
References - 14, 149, 152
A-248
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-WATER CARRIAGE TOILETS
FACT SHEET 7.2.2
FLOW DIAGRAM
i let WasLes
Toilet Wastes
Toilet Wastes
J
Toilet
Compos t _
Ol 1
Recirculating
Treatment
Wastes
Storage
To disposal
oil
ENERGY NOTES (149) -
Incinerating Toilets - Gas (propane)
Incinerating Toilets - Electricity
Composting - Small
Composting - Large
Oil Recirculating Toilet
4,000 to 6,000 Btu/use (17.5 to 26.2 X 10 Btu/yr)
0.06 to 1.2 kWh/use (262 to 5,250 kWh/yr)
1-7 kWh/d (365 to 2,555 kWh/yr)
1-8 kWh/d (365 to 2,920 kWh/yr)
0.657 kWh/d (240 kWh/yr)
COSTS (103) (149) -
1. Labor rates @ S10/hr 6 6
2. Energy consumption estimates based on: Gas (propane) @ $8/10 Btu; Oil @ $3.42/10 Btu;
Electricity @ $.02/kWh.
3. Cost estimates based on 1978 dollars; ENR Index - 2776.
Incinerating
Gas/Oil Electric
800 to 1200 600 to 1000
Installed Costs ($)
Composting
Small Large
700 to 1200 1500 to 3200
Operation and Maintenance ($/yr)
80 80 40
5 to 110 7 to 51 7 to 5Q
85 to 190
87 to 131
Maintenance 80
Energy 55 to 230
Total 135 to 310
REFERENCES - 103, 149, 152
*To convert construction cost to capital cost see Table A-2.
47 to 98
Oil Recirculating
4500 to 6000
180
5_
185
A-249
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A-250
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BIBLIOGRAPHY (CONTINUED)
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A-251
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BIBLIOGRAPHY (CONTINUED)
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A-253
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BIBLIOGRAPHY (CONTINUED)
107. Conference Notes, Sam Perri, from Robinson Pipe Cleaning Co., Newark, NJ, (June 20, 1978).
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123. Communication with (via letter) Dennis M. Howard, Passavant Corp., Birmingham, AL, Subject: Equipment Lists
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126. U.S. EPA, " Microstraining and Disinfection of Combined Sewer Overflows - Phase III," Report No. 670/2-75-021,
April 1975.
127. U.S. EPA, "Bench-Scale High-Rate Disinfection of Combined Sewer Overflows with Chlorine and Chlorine Dioxide,"
Report No. 670/2-75-021, April 1975.
128. U.S. EPA, "Laboratory Ozonation of Municipal Wastewaters," Report No. 670/2-73-075, September 1973.
129. Cochrane Division, Crane Co., "Microstraining and Disinfection of Combined Sewer Overflows," U.S. Department
of the Interior, Federal Water Quality Administration, Contract No. 14-12-136.
130. "Ozone Gives Wastewater the Treatment," Chemical Week, June 21, 1978, p. 49.
131. "Ozone Use Grows as Effluent Disinfectant," ENR, May 11, 1978, p. 18.
132. Stopka, Karel, "Ozone-Activated Carbon Can Remove Organics," Water and Sewage Works, May 1978, p. 88.
133. Fair, G.M., J.C. Geyer, and D.A. Okun, "Water and Wastewater Engineering, John Wiley and Sons, 1968.
134. U.S. Department of Health, Education and Welfare, "Manual of Septic Tank Practice," PHS Publication No. 526,
1972.
A-254
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BIBLIOGRAPHY (CONTINUED)
135. U.S. EPA, "Environmental Effects of Septic Tank Systems," Report No. 600.3-77-096 (August 1977).
136. Garber, W.F, et.al, "Thermophilic Digestion at the Hyperion Treatment Plant," Journal Water Pollution Control
Federation, Vol. 47, No. 5, May 1975, p. 950.
137. Harris, S.E., et.al, "Intermittent Sand Filtration for Upgrading Waste Stabilization Pond Effluents," Journal
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138. Matsch, L.C., R. F. Dmevich, "Autothermal Aerobic Digestion," Journal Water Pollution Control Federation, Vol.
49, No. 2, February 1977, p. 286.
139. Communication (via telephone) with Steven Caliento, Passavant Corporatiop, Connecticut, Subject: Belt Filter
Press Costs, September 15, 1978.
140. Solio, F.N., et. al,"Disinfection of Sewage Effluents," Illinois State Water Survey, PB-222 355, July 1973.
141. Clow Waste Treatment Division "Engineering Manual, Wastewater Handling and Treatment Systems," Clow Corpo-
ration, Florence, Kentucky.
142. U.S. EPA, "Transport of Sewage Sludge," EPA-600/2-77-216, EPA Technology Series, December 1977.
143. Jewell, William T., and Randolph M. Kabrick, "Autoheated Aerobic Thermophilic Digestion with Air Aeration,"
Department of Agricultural Engineering, Cornell University, Ithaca, New York.
144. Communication (via telephone) with Dick Sobel, Sharpies-Stokes, New York, September 26, 1978, Subject: Cost
Data for Thickening; Solid Bowl and Disc Centrifugal.
145. Communication (via telephone) with Bob Honeychurch, Dorr-Oliver, Stanford, CT, September 26, 1978, Subject:
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146. Sawyer, Clair N., and Perry L. McCarty, Chemistry for Sanitary Engineers, McGraw-Hill Company, 1967.
147. Communication (via telephone) with Dr. William Jewell, September 27, 1978. Subject: Thermophilic Aerobic
Digestion With Air.
148. Walsh, James J., Coppel, Wayne, "Seminar Sludge Treatment and Disposal, Part II, Sludge Disposal," U. S.
EPA, March 1978.
149. Otis, Richard J. , W. C. Boyle, "U.S. EPA Training Seminar for Wastewater Alternatives For Small Communities,
OnSite Alternatives," August 14-1 8, 1978; August 28 - September 1, 1978.
150. U. S. EPA "Appraisal of Powdered Activated Carbon Processes For Municipal Wastewater Treatment," Report No.
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151. Communication (Via Telephone) with G. Burde, Burde Associates, Paramus, N. J. Subject: Package Plant Treat-
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152. Bauer, David H. et. al., "Identification, Evaluation and Comparison of On-Site Wastewater Alternatives,"
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153. Rand Development Corporation, "Rapid Flow Filters For Sewer Overflows," August, 1969.
154. U. S. EPA, "Urban Stormwater Management and Technology, An Assessment," Report No. 670/2-74-040 (December
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155. U. S. EPA, "Cost Estimating Manual-Combined Sewer Overflow Storage and Treatment," Report No. 600/2-76-286,
(December 1976).
156. Kalinske, A. A., "Comparison of Air and Oxygen Activated Sludge Systems," Journal Water Pollution Control
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157. Chamman, T. D., L. G. Matsch, and E. H. Zander, "Effect of High Dissolved Oxygen Concentration in Activated
Sludge Systems, " Journal Water Pollution Control Federation, Vol. 48, No. 11, November 1976, pp. 2486-2510.
158. Parker, D. S., M. S. Merrill, "Oxygen and Air Activated Sludge: Another View," Journal Hater Pollution
Control Federation, Vol. 48, No. 11, November 1976, pp. 2511-2528.
159. U. S. EPA, "Demonstration of Wasteflow Reduction From Households," Report No. 670/2-74-071, September 1974.
A-255
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BIBLIOGRAPHY (CONTINUED)
160. Otis, R. J., W. C. Boyle, "Performance of Single Household Treatment Units," Journal Environmental
Engineering Division, American Society of Civil Engineers, Vol. 102, No. EE1, February 1976, pp. 175-189.
161. "Exploring Energy Choices," Ford Foundation Report-1974.
162. Saver, O.K. et. al, "Intermittent Sand Filtration of Household Wastewater," Journal Environmental Engineering
Division, American Society of Civil Engineers, Vol. 102, No. EE4, August 1976, pp. 789-803.
163. Drewhing, Frank J., et. al., "Disinfection/Treatment of Combined Sewer Overflows," Municipal Environmental
Research Laboratory, Office of Research and Development, U. S. EPA, Cincinnati, Ohio, Project No. 5802400.
164. "Combined Sewer Overflow Abatement Program, Vol. I," Monroe County Division of Pure Waters, Rochester, New
York, March 1978.
165. Cochrane Division, Crane Co., "Microstraining and Disinfection of Combined Sewer Overflows," Federal Water
Quality Administration, U. S. Dept. of the Interior, Program No. 11023 EVO, June 1970.
166. Glover, George E., George R. Herbert, "Microstraining and Disinfection of Combined Sewer Overflows-Phase
II," Office of Research and Monitoring, U. S. EPA and Philadelphia Water Department, Philadelphia, P.A. EPA-
R2-73-124, January, 1973.
167. Lager, John A., et. al, "Urban Water Management and Technology: Update and Users Guide," Office of
Research and Development, U.S. EPA-600/8-77-014 (September 1977).
168. U. S. EPA, "Process Design Manual—Municipal Sludge Landfills," Technology Transfer, Report No. 625/1-78-010
SW-705 (October 1978).
169. Spray Irrigation Manual, Pennsylvania Department of Environmental Resources, Bureau of Water Quality Manage-
ment, Publication No. 31, 1972 Edition.
170. Pickett, Edward M., "Evapotranspiration and Individual Lagoons," Proceedings of the Northwest On-Site Waste
Water Disposal Short Course," University of Washington, December 8-9, 1976.
171. Communication (via telephone) with Walter Kuntz, Foley Machinery, Piscataway, New Jersey, Subject: Sludge
Trenching.
172. U.S. EPA, "Pilot Plant for Tertiary Treatment of Wastewater with Ozone," Report No. EPA-R2-73-146, January
1973.
173. Williamson, K.J., G. R. Swanson, "Field Evaluation of Rock Filters for Removal of Algae from Lagoon Effluents,
Dr. R. Lewis of U.S. EPA, Cincinnati, Ohio, October 16, 1978.
174. Duffer, W.R., J. E. Moyer, "Municipal Wastewater Aquaculture," U.S. EPA-600/2-78-110, June 1978.
175. "Advanced Wastewater Treatment Nature's Way," Environmental Science and Technology, Vol. 12, No. 9, September
1978.
176. Fairfield Service Co., Vendor Literature, Fairfield Engineering Co., P.O. Box 354, Marion, OH 43302.
177. Communication (via telephone) with R. Walters; Schandt, Siemm, Walters, Inc., Eugene, Oregon, Subject: Veneta
Rock Filter.
178. Neptune Microfloc, "ABF Biomedia, Superior Fixed Growth Media for Biological Treatment," Equipment Manufact-
urers Literature on ABF Systems, Copyright 1975.
179. Williams, Charles, R., et. al., "Results of Pilot Studies on Biological Treatment of Combined Food Processing/
Domestic Wastewater at Tracy, California," YTO S Associates, Walnut Creek, California.
180. Slechta, A., G. Mattli, "Activated Bio-Filter Process for Biological Wastewater Treatment," Nepture Microfloc,
Inc.
181. Mattli, G., A. Slechta, " Final Report, City of Turlock, California, 1975 Pilot Plant Study, ABF System," CH
2M-Hill, Inc.
182. City of Helena, Montana, Application for Federal Assistance, "Evaluation of Activated Bio-Filter Wastewater
Treatment Process at Helena, Montana," EPA Project Control No. R806047 01, March 31, 1978.
183. Slechta, Alfred, "Final Report, City of Rochester, Minnesota, 1974 Pilot Plant Study, ABF Nitrification
System," Kirkham-Michael S Assoc., Wallace, Holland, Kastler, Schmitz S Co., Copyright, 1974.
A-256
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BIBLIOGRAPHY (CONTINUED)
184. Neptune Microfloc, "ABF," Bulletin No. KD 7400-1 Secondary Biological Wastewater Treatment Systems.
185. Stetzer, R.H., "FMC Pure Oxygen, An Effective Solution to Wastewater Treatment and Process Applications,"
paper presented at 70th Annual AICHE Meeting, November 15, 1977, New York, NY.
186. Pearlman, S.R. , and D. G. Fullerton, "Full Scale Demonstration of Open Tank Oxygen Activated Sludge Treat-
ment," U.S. EPA Grant No. S803910, draft report to Municipal Environmental Research Laboratory, Office of
Research and Development, U.S. EPA, Cincinnati, OH.
187. Gulp, Wessler and Gulp, Suspended Growth Biological Wastewater Treatment - Construction, Operating and Main-
tenance Cost Estimates, Vol. 2, unpublished EPA Document, El Dorea HiJ.ls, CA.
188. Buck, B.J., L.M. LaClair, and M.R. Morlino, "Recent Advances in the Biological Removal of Phosphorus," paper
presented at meeting of Water Pollution Control Association of PA, Hershey, PA, June 15-17, 1977.
189. Sheridan, D.L. and R. W. Regan, "Phosphorus Release by PhoStrip Activated Sludge, paper presented at the
National Conference on Environmental Engineering sponsored by the American Society of Civil Engineers,
Environmental Engineering Division, Kansas City, MO, July 10-12, 1978.
190. Communication with (via letter) Louis M. LaClair, Product Manager, Union Carbide Corp., Tonawanda, NY, Sub-
ject: PhoStrip Process.
191. Peirano, L.E., "Low Cost Phosphorus Removal at Seno/Sparks, Nevada," Journal Water Pollution Control Fed-
eration, Vol. 49, No. 4, April 1977, pp. 568 - 574.
192. Drnevich, R.F., and L. M. LaClair, "New System Cuts Phosphorus for Less Cost," Water s Water Engineering,
Vol. 13, No. 9, September 1976, pp. 104-108.
193. Levin, G.V., G. J. Topol, and A.G. Tarnay, "Operation of Full-Scale Biological Phosphorus Removal Plant,"
Journal Water Pollution Control Federation, Vol. 47, No. 3, March 1975, pp. 577-590.
194. Vendor literature, "Metro-Waste Composting System," Resource Conversion Systems, Inc., 9039 Katy Freeway,
Suite No. 300, Houston, TX 77024.
195. Vendor literature, Smith s Loveless, Lenexa, KS 66215
196. Vendor literature. Clow Corp., Florence, KY 41042.
197. Vendor literature, Chicago Pump, Chicago, IL 60647.
198. Vendor literature, Carlgen, Inc., Walden NY 12586.
199. Ewing, Lewis, et.al., "Effects of Thermal Treatment of Sludge on Municipal Wastewater Treatment Costs," U.S.
EPA-600/2-78-073 (June 1978).
200. "Compiled Data on Vascular Aquatic Plant Program 1975-1977, NASA-NSTL Station Mississippi, 39529".
201. U.S. EPA, "Estimating Costs and Manpower Requirements for Conventional Wastewater Treatment Facilities,"
Report 17090 DAN, October 1971.
202. Finstein, M.S. and M. Morris, "Composting," New Jersey Effluents. Vol. 11, No. 1, April 1978.
203. Gray, K.R., et al., "Review of Composting, Part 2 - The Practical Process," Process Biochemistry, p. 22,
October 1971.
204. B.W. Ryan, E.F. Earth, "Nutrient Control by Plant Modification at El Lago, Texas," Wastewater Research Divi-
sion, MERL, Cincinnati, Ohio.
205. Via telephone, Frank Carlson, Royer Foundry & Machine Co., 158 Pringle Street, Kingston, PA 18704.
206. Villiers and Farrell, "A Look at Newer Methods for Dewatering Sewage Sludges," Civil Engineering ASCE, p 66,
December 1977.
207. Gulp, Wesner and Gulp, Attached Growth Biological Wastewater Treatment - Construction, Operating and Main-
tenance Cost Estimates, Vol. 1, unpublished EPA Document, El Dorado Hills, CA.
208. U.S. EPA, "Lime Use in Wastewater Treatment Design and Cost Data", U.S. EPA-600/2-75-038, October 1975.
209. "Compiled Data on Vascular Aquatic Plant Program 1975 - 1977," NASA - NSTL Station, MI 39529.
A-257
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BIBLIOGRAPHY (CONTINUED)
210. U.S. EPA, "Evaluation of Dewatering Devices for Producing High Sludge Solids Cake", Draft Report, Contract
No. 68-03-2455, MERL 1978.
211. Burant, W., and T.J. Vollstandt, "Full-scale Wastewater Treatment with Powdered Activated Carbon," Water and
Sewage Works, November 1973.
212. Adams, A.D., "Powdered Carbon: Is It Really That Good?", Water and Waste Eng., March 1974.
213. Stern, G., "Processing, Economics and Sale of Heat Dried Sludge," Proceedings of the 1975 National Conference
on Municipal Sludge Management and Disposal, Anaheim, California, August 18-20, 1975.
214. National Academy of Sciences, 1975, "Making Aquatic Weeds Useful: Some Perspectives for Developing Countries.'
Commission on International Relations (JH215), National Academy of Sciences - National Research Council, 2101
Constitution Ave., Washington, D.C. 20418.
215. Tourbier, J., and R.W. Pierson, Jr. (eds). 1976. Biological Control of Water Pollution. University of
Pennsylvania Press.
216. NASA. "Compiled Data on the Vascular Aquatic Plant Program: 1975 - 1977." National Aeronautics and Space
Administration, National Space Technology Laboratories, NSTL Station, Mississippi 39529.
217. Tilton, D.L., R.H. Kadlec and C.J. Richardson (eds). 1976. "Proceedings of a National Symposium on Fresh-
water Wetlands and Sewage Effluent Disposal." Wetlands Ecosystem Research Group, The University of Michigan,
Ann Arbor, MI.
218. Spangler, F.L., W.E. Sloey and C.W. Fetter, Jr. 1976. "Wastewater Treatment by Natural and Artificial
Marshes." EPA 600/2-76-207.
219. Henderson, U.B. and F.S. Wert. 1976. "Economic Assessment of Wastewater Aquaculture Treatment Systems." EPA
600/2-76-293.
220. Duffer, W.R. and J.E. Moyer. 1978. "Municipal Wastewater Aquaculture." EPA 600/2-78-110.
221. Von Dreusche and Negra, 1978. "Pyrolyzer Design Alternatives and Economic Factors for Pyrolyzing Sewage
Sludge in Multiple Hearth Furnaces," Nichols Engineering & Research Corporation, Belle Meade, NJ.
222. Nichols Engineering & Research Corporation, Belle Meade, NJ, September 1977. "Pyrolysis of Sewage Sludge -
The Choice is Yours."
223. Nichols Engineering s Research Corporation, Belle Meade, NJ, 1978. Excerpt from "Phase I Report of Pyrolysis
of Sewage Sludges in the N.Y.-N.J. Metropolitan Area." Interstate Sanitation Commission.
224. Jones and Radding (eds). "Solid Wastes and Residues, Conversion by Advanced Thermal Processes," ACS Sympo-
sium, Series 76.
225. Letter, Nichols Engineering to Mr. Leo Pinczuk, Burns and Roe Industrial Services Corp., August 15, 1978.
226. "The Co-Disposal of Sewage Sludge and Refuse in the Purox System". EPA 600/2-78-198, December 1978.
227. Correspondence with Neptune Microfloc, 1965 Airport Road, P.O. Box 612, Corvallis, OR 97330.
228. "Construction Costs for Municipal Wastewater Conveyance Systems: 1973-1977," 430/9-77-015, MCD-38, U.S.
EPA, May 1978.
229. Telephone communication with L. Moody and D. Triestran, Clow Corporation.
230. "Analysis of the Use of Waste Pickle Liquor for Phosphorus Removal" by Whitman, Requardt and Associates
Engineers, Baltimore, MD, September 1978.
231. "Progress in Wastewater Disinfection Technology", Proceedings of the National Symposium, Cincinnati,
OH, September 18-20, 1978, EPA-600/9-79-018, June 1979.
232. "Sludge Treatment and Disposal", Vol. 1, U.S. EPA Technology Transfer, Report No. 625/4-78-012, October
1978.
233. Via Correspondence - Ronald L. Antonie, Autotrol Corporation, Bio-Systems Division, June 13, 1979.
234. Bowker, R.P.G. et al, "Alternatives for the Treatment and Disposal of Residuals from On-Site Wastewater
Systems", Technology Transfer Handout for EPA Seminar - Wastewater Alternatives for Small Communities,
August 1978.
235. Bennett, S. A., et al, "Feasibility of Treating Septic Tank Waste by Activated Sludge," EPA 600/2-77-
141, August 1977.
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BIBLIOGRAPHY (CONTINUED)
236. Cooper, I. A. et al, "Septage Management". Draft ORD report, Contract No. 68-03-2231.
237. Kolega, et al, "Treatment and Disposal of Wastes Pumped from Septic Tanks", EPA 600/2-77-198, September 1977.
238. "Maine Guidelines for Septic Tank Sludge Disposal on the Land", Life Sciences and Agriculture Experiment
Station, University of Maine (Orono), and Maine Soil and Water Conservation Commission, Miscellaneous
Report 155, April 1974.
239. "Guidelines for Septage Handling and Disposal", New England Interstate Water Pollution Control Commission,
TGM-1, August 1976.
240. Barlow and Cassell, "Septage Management Strategies for Vermont", Vermont Water Resources Research Center,
University of Vermont, Project Report No. 2, April 1978.
241. Carrol, Robert G. "Planning Guidelines for Sanitary Waste Facilities", CH2M Hill for U.S.D.A. Forest Service,
California Region.
242. Segall, B., and C. Ott, "Monitoring Septage Addition to Wastewater Treatment Plants", Vol. 1, University of
Lowell, Prepublication Grant No. 805406.
243. Feige, W. A. et al, "An Alternative Septage Treatment Method: Lime Stabilization/Sand Bed Dewatering", EPA
600/2-75-036, September 1975.
244. Noland, R.F. et al, "Full Scale Demonstration of Lime Stabilization", EPA 600/2-78-171, September 1978.
245. "Septic Tank Sludge Treatment by the Purifax Process of Rapid Chemical Oxidation", BIF, A Unit of General
Signal, 1600 Division Road, W. Warwick, RI 02893.
246. "Evaluation of the Purifax Process for the Treatment of Septic Tank Sludges", U.S. EPA Lebanon Pilot Plant,
Unpublished Report, June 1975.
247. "Partial Characterization of Chlorinated Organics in Superchlorinated Septages and Mixed Sludges", EPA
600/2-78-20, March 1978.
248. "Operations Manual - Sludge Handling and Conditioning", Chapter VII - Chlorine Treatment, EPA 430/9-78-002,
February 1978.
249. Epstein, E. et al, "A Forced Aeration System for Composting Wastewater Sludge", JWPCF Vol. 48, No. 4, April
1976.
250. Colacicco, et al, "Costs of Sludge Composting", ARS-NE-79, February 1977.
251. Bowker, R.R.G., "Static Pile Composting: A Potential Septage Handling Alternative for Small Communities",
EPA-MERL, Draft Report, 1978.
252. Jewell, et al, "Design Guidelines for Septic Tank Sludge Treatment and Disposal", Progress in Water
Technology, T_, 2, 1975.
253. Howley, J.B., "Biological Treatment of Septic Tank Sludge", MS-Thesis, University of Vermont, October 1973.
254. "The Feasibility of Accepting Privy Vault Wastes at the Bend Waste Treatment Plant", prepared for City of
Bend, Oregon, CSG Engineers, Salem, OR, June 1973.
255. Mignone, N.H., "Aerobic Digestion of Municipal Wastewater Sludges", Envirex, Inc., EPA Seminar Handout,
Sludge Treatment and Disposal, March 1978.
256. Cosulich, W.F., "Stop Dumping Cesspool Wastes", The American City, Vol. 83, February 1968, pp. 78-79.
257. Condren, A.J., "Pilot Scale Evaluations of Septage Treatment Alternatives", EPA 600/2-78-164, September 1978.
258. Medbo, F., "Operational Problems at Sewage Treatment Plants", Nordforsk (Nordic Research), Environmental
Protection Secretariat Publication, No. 9, 1975, pp. 259-274.
259. Benjes, Henry H., Jr. et al, "Capital and O&M Cost Estimates for Biological Wastewater Treatment Processes",
unpublished report by Gulp, Wesner and Gulp, El Dorado Hills, CA for Municipal Environmental Research Lab-
oratory, U.S. EPA, Cincinnati, OH.
260. "Oxygen Aeration at Newtown Creek", U.S. EPA 600/2-79-013, June 1979.
261. Steel, Ernest, W., Water Supply and Sewage, McGraw Hill.
262. Wang, L.K., et al, "Chemistry of Nitrification-Denitrification Process", Journal of Environmental Science,
Vol. 21, P. 23-28, December 1978.
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BIBLIOGRAPHY (CONTINUED)
263. Nash, N., et al, "Oxygen Aeration at Newtown Creek", EPA-600/2-79-013, Cincinnati, OH, June 1979.
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APPENDIX B
LEGISLATION, REGULATIONS, AND PROGRAM GUIDANCE
INFORMATION PERTAINING TO INNOVATIVE AND
ALTERNATIVE TECHNOLOGY UNDER PL 95-217
B-i
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APPENDIX B
Contents Page
Legislation B-l
201(d) B-l
201(g)(5) B-l
201 (i) B-l
201(e) B-l
201 (j) B-2
202(a)(2) B-2
202(a)(3) B-2
202(a)(4) B-2
304(d)(3) B-3
205( i) B-3
Regulations
35.908 B-3
35.915(a)(l) B-5
35.915(e) B-5
35.917-1(d)(8)(9) B-6
35.915-1 (b) B-6
35.930-5(b) B-6
35.935.20 B-7
35.936-13 B-7
Program Requirements Memoranda
PRM 79-3, Revision of Agency Guidance for Evaluation of Land ... B-10
Treatment Alternatives Employing Surface Application
PRM 79-8, Small Wastewater Systems B-29
B-ii
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LEGISLATION
The following sections of the Clean Water Act Amendments of 1977
(PL 95-217) contain specific provisions relating to innovative and
alternative technology. A one sentence synopsis as well as the com-
plete text of the applicable sections of the law has been provided in
this first section of the appendix. This is followed by all pertinent
agency (EPA) regulations that have been promulgated as required by the
law, along with additional program guidance information.
Section 201(d) Encourages revenue producing waste management facilities.
Section 201(g)(5) Requires all applicants to fully study innovative and
alternative treatment options.
The administrator shall not make grants from funds authorized
for any fiscal year beginning after September 30, 1978, to any State,
municipality, or intermunicipal or interstate agency for the erection,
building, acquisition, alteration, remodeling, improvement or exten-
sion of treatment works unless the grant applicant has satisfactorily
demonstrated to the Administrator that innovative and alternative
wastewater treatment processes and techniques which provide for the
reclaiming and reuse of water, otherwise eliminate the discharge of
pollutants, and utilizing recycling techniques, land treatment, new
or improved methods of waste treatment management for municipal and
industrial waste (discharged into municipal systems) and the confined
disposal of pollutants will not migrate to cause water or other
environmental pollution, have been fully studied and evaluated by the
applicant taking into account Section 201(d) of this Act and taking
into account and allowing to the extent practicable the more efficient
use of energy and resources.
Section 201(i) Encourages energy conservation.
The Administrator shall encourage waste treatment management
methods, processes, and techniques which will reduce total energy
requirements.
Section 201(e) Requires EPA to encourage treatment techniques which will
reduce total energy requirements.
The Administrator shall encourage waste treatment management
which results in integrating facilities for sewage treatment and
recycling with facilities to treat, dispose of, or utilize other
industrial and municipal wastes, including but not limited to solid
waste and waste heat and thermal discharges. Such integrated
facilities shall be designed and operated to produce revenues in
excess of capital and operation and maintenance costs and such
revenues shall be used by the designated regional management agency
to aid financing other environmental improvement programs.
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Section 201(j) Allows EPA to select the innovative and alternative process
option if costs are as high as 115% of least costly option.
The Administrator is authorized to make a grant for any treat-
ment works utilizing processes and techniques meeting the guidelines
promulgated under Section 304(d)(3) of this Act, if the Administrator
determines it is in the public interest and if in the cost effectiveness
study made of the construction grant application for the purpose of
evaluating alternative treatment works, the life cycle cost of the
treatment works for which the grant is to be made does not exceed the
life cycle cost of the most effective alternative by more than 15
per centum.
Section 202(a)(2) Increases Federal grant to 85% for treatment works
utilizing innovative or alternative processes.
The amount of any grant made after September 30, 1978, and
before October 1, 1981, for any eligible treatment works or sig-
nificant portion thereof utilizing innovative or alternative
wastewater treatment processes and techniques referred to in
section 201(g)(5) shall be 85 per centum of the cost of con-
struction thereof. No grant shall be made under this paragraph
for construction of a treatment works in any State unless the
proportion of the State contribution to the non-Federal share of
construction costs for all treatment works in such State receiving
a grant under this paragraph is the same as or greater than the
proportion of the State contribution (if any) to the non-Federal
share of construction costs for all treatment works receiving
grants in such State under paragraph (1) of this subsection.
Section_202(a)(3) Authorizes EPA to pay 100% of all costs to replace
innovative or alternative treatment facilities that failed.
In addition to any grant made pursuant to paragraph (2) of
subsection 202(a) the Administrator is authorized to make a grant
to fund all of the costs of the modification or replacement of any
facilities constructed with a grant made pursuant to paragraph (2)
if the Administrator finds that such facilities have not met design
performance specifications unless such failure is attributed to
negligence on the part of any person and if such failure has sig-
nificantly increased capital or operating and maintenance expenditures.
Section 202(a)(4) Limits the treatment works eligible for bonus grant
increases for innovative and alternative processes to treatment plant-
related works only.
For the purposes of this section, the term "eligible treatment
works" means those treatment works in each State which meet the
requirements of section 201(g)(5) of this Act and which can be
fully funded from funds available for such purpose in such State in
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the fiscal years ending September 30, 1979, September 30, 1980, and
September 30, 1981. Such term does not include collector sewers,
interceptors, storm or sanitary sewers or the separation thereof,
or major sewer rehabilitation.
Section 304(d)(3) Mandates that EPA promulgate guidelines for identifying
and evaluating innovative and alternative processes during FY 1978.
The Administrator, after consultation with appropriate Federal
and State agencies and other interested persons, shall promulgate
within one hundred and eighty days after the date of enactment of
this subsection guidelines for identifying and evaluating innovative
and alternative wastewater treatment processes and techniques referred
to in section 201(g)(5) of this Act.
Section 205(i) Authorizes EPA to set aside a reserve of 2% for each
allotment to use only to increase federal share of grants for innovative
and alternative processes to 85%.
Not less than one-half of one per centum of funds allotted to
a State for each of the fiscal years ending September 30, 1979.
September 30, 1980, and September 30, 1981, under subsection (a) of
this section shall be expended only for increasing the Federal share
of grants for construction of treatment works utilizing innovative
processes and techniques from 75 per centum to 85 per centum pursuant
to section 202(a)(2) of this Act. Including the expenditures authorized
by the preceding sentence, a total of two per centum of the funds alloted
to a State for each of the fiscal years ending September 30, 1979, and
September 30, 1980, and 3 per centum of the funds allotted to a State
for the fiscal year ending September 30, 1981, under subsection (a)
of this section shall be expended only for increasing grants for
construction of treatment works from 75 per centum to 85 per centum
pursuant to section 202(a)(2) of this Act.
REGULATIONS
The following regulations describe the Environmental Protection Agency's
requirements for Innovative and Alternative Technolgoy. The basic Innovative
Alternative Technology regulation is 35.908 and is presented in its entirety.
Applicable portions of other regulations are presented.
35.908 Describes basic agency requirements and policy for funding,
priority, and replacement costs for innovative and alternative technology.
(a) Policy. EPA's policy is to encourage, and, where possible,
to assist in the development of innovative and alternative technologies
for the construction of wastewater treatment works. Such technologies
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may be used in the construction of wastewater treatment works under
this subpart as §35.915-1, §35.930-5, Appendix E, and this section
provide. New technology or processes may also be developed or demon-
strated with the assistance of EPA research or demonstration grants
awarded under Title I of the Act (see Part 40 of this subchapter).
(b) Funding for innovative and alternative technologies.
(1) Projects or portions of projects which meet criteria
for innovative or alternative technologies in Appendix E
may receive 85 percent grants (see §35.930-5).
(i) Only funds from the reserve in §35.915-1 (b) shall
be used to increase these grants from 75 to 85 percent.
(ii) Funds for the grant increase shall be distributed
according to the chronological approval of grants, unless
the State and the Regional Administrator agree otherwise.
(iii) The project must be on the fundable portion of
the State project priority list.
(iv) If the project is an alternative to conventional
treatment works for a small community (a municipality
with a population of 3,500 or less or highly dispersed
section of a larger municipality, as defined by the
Regional Administrator), funds from the reserve in
§35.915(e) may be used for the 75 percent portion of the
Federal grant.
(v) Only if sewer related costs qualify as alternatives
to conventional treatment works for small communities are
they entitled to the grant increase from 75 to 85 percent,
either as part of the entire treatment of works or as
components.
(2) A project or portions of a project may be designated
innovative or alternative on the basis of a facilities plan
or on the basis of plans and specifications. A project that
has been designated innovative on the basis of the facilities
plan may lose that designation if plans and specifications
indicate that it does not meet the appropriate criteria stated
in section 6 of Appendix E.
(3) Projects or portions of projects that receive Step 2,
Step 3, or Step 2+3 grant awards after December 27, 1977,
from funds allotted or real lotted in fiscal year 1978 may also
receive the grant increase from funds allotted for fiscal year
1979 for eligible portions that meet the criteria for alter-
native technologies in Appendix E, if funds are available for
such purposes under §35.915-1(b).
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(c) Modification or replacement of innovative and alternative
projects.
The Regional Administrator may award grant assistance to fund
100 percent of the eligible costs of the modification or replacement
of any treatment works constructed with 85 percent grant assistance if:
(1) He determines that:
(i) The facilities have not met design performance
specifications (unless such failure is due to any
person's negligence); and
(ii) Correction of the failure requires significantly
increased capital or operating and maintenance expenditures;
and
(iii) Such failure has occurred within the two year
period following final inspection; and
(2) The replacement or modification project is on the fundable
portion of the State's priority list.
35.915(a)(1)_. Part of the State priority system and project priority list
that permits raising priority of innovative alternative projects or inno-
vative alternative 100% replacement grants.
(iii) Step 2, Step 3 and Step 2+3 projects utilizing
processes and techniques meeting the innovative and alternative
guidelines in Appendix E of this part may receive higher priority.
Also 100 percent grants for projects that modify or replace
malfunctioning treatment works constructed with an 85 percent grant
may receive a higher priority.
(iv) Other criteria, consistent with these, may be considered
(including the special needs of small and rural communities); how-
ever, the State shall not consider the project area's development
needs not related to pollution abatement, the geographical region
within the State, or future population growth projections
35.915(e). Submission and review of project priority list.
The State shall submit the priority list as part of the annual
state program plan under Subpart G of this part. A summary of State
agency response to public comment and hearing testimony shall be
prepared and submitted with the priority list. The Regional Adminis-
trator will not consider a priority list to be final until the public
participation requirements are met and all information required for
each project has been received. The Regional Administrator will review
the final priority list within thirty days to ensure compliance with
the approved State priority system. No project may be funded until
this review is complete.
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35.917-1(d)(8)(9). Energy analysis content of Facilities plan prepared
after September 30, 1978, for innovative technology.
(8) For facilities planning begun after September 30, 1978,
whether or not prepared under a Step 1 grant, an analysis of inno-
vative and alternative treatment processes and techniques that
reclaim and reuse water, productively recycle wastewater constituents,
eliminate the discharge of pollutants, recover energy or otherwise
achieve the benefits described in Appendix E
(9) For facilities planning begun after September 30, 1978,
whether or not prepared under a Step 1 grant, an analysis of the
primary energy requirements (operational energy inputs) for each
system considered. The alternative selected shall propose adoption
of measures to reduce energy consumption or to increase recovery as
long as such measures are cost-effective. Where processes or tech-
niques are claimed to be innovative technology on the basis of energy
reduction criterion contained in paragraph 6e(2) of Appendix E to
this subpart, a detailed energy analysis shall be included to sub-
stantiate the claim to the satisfaction of the Regional Administrator.
35.915-1(b). Reserve funding for innovative alternative technology.
(b) Reserve for innovative and alternative technology project
grant increase.
Each State shall set aside from its annual allotment a specific
percentage in order to increase the Federal share of grant awards from
75 percent to 85 percent of the eligible cost of construction (under
§35.908(b)(l)) for construction projects which use innovative or al-
ternative wastewater treatment processes and techniques. The set-aside
amount shall be 2 percent of the State's allotment for each of the
fiscal years 1979 and 1980, and 3 percent for fiscal year 1981. Of this
amount not less than one-half of one percent of the State's allotment
shall be set aside in order to increase the Federal grant share for
projects utilizing innovative processes and techniques. Funds reserved
under this section may be expended on projects for which facilities
plans were initiated before fiscal year 1979. These funds shall be
reallotted if not used for this purpose during the allotment period.
35.930-5(b). Federal and State funding of Step 2 or 3 grants and Step 2+3
increased (85%) grants.
(b) Innovative and alternative technology.
In accordance with §35.908(b), the amount of any Step 2, Step 3,
or Step 2+3 grant made from funds allotted for fiscal years 1979, 1980,
and 1981 shall be 85 percent of the estimated cost of construction for
those eligible treatment works or significant portions of them that
the Regional Administrator determines meet the criteria for innovative
or alternative technology in Appendix E. These grants depend on the
availability of funds from the reserve under § 35.915-1(b). The
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proportional State contribution to the non-Federal share of construction
costs for 85 percent grants must be the same as or greater than the pro-
portional State contribution (if any) to the non-Federal share of eligible
construction costs for all treatment works which receive 75 percent grants
in the State.
(c) Modification and replacement of innovative and alternative
projects.
In accordance with §35.908(c) and procedures published by EPA,
the Regional Administrator may award grant assistance to fund 100 percent
of the eligible costs of the modification or replacement of any treatment
works constructed with grant assistance based upon a Federal share of 85
percent under paragraph (b) of this section.
35.935.20. Post award innovative grant requirements
If the grantee receives an 85 percent grant for innovative processes
and techniques, the following conditions apply during the 5 year period
following completion of construction:
(a) The grantee shall permit EPA personnel and EPA designated
contractors to visit and inspect the treatment works at any
reasonable time in order to review the operation of the inno-
vative processes or techniques.
(b) If the Regional Administrator requests, the grantee will
provide EPA with a brief written report on the construction,
operation, and costs of operation of the innovative processes
or techniques.
35.936-13. Application of nonrestrictive specifications to innovative
alternative technology.
(1) No specification for bids or statement of work in connection
with such work shall be written in such a manner as to contain propri-
etary, exclusionary, or discriminatory requirements other than those
based upon performance, unless such requirements are necessary to test
or demonstrate a specific thing or to provide for necessary inter-
changeability of parts and equipment, or at least two brand names or
trade names of comparable quality or utility are listed and are fol-
lowed by the words "or equal." The single base bid method of solici-
tation for equipment and parts for determination of a low, responsive
bidder may not be utilized. With regard to materials, if a single
material is specified, the grantee must be prepared to substantiate
the basis for the selection of the material.
(2) Project specifications shall, to the extent practicable,
provide for maximum use of structures, machines, products, materials,
construction methods, and equipment which are readily available through
competitive procurement, or through standard or proven production tech-
niques, methods, and processes, except to the extent that innovative
technologies may be used under §35.908 of this subpart.
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(b) Sole source restriction.
A specification shall not require the use of structures,
materials, equipment, or processes which are known to be available
only from a sole source, unless the grantee's engineer has adequately
justified in writing that the proposed use meets the particular
project's minimum needs.
(c) Experience clause restriction.
The general use of experience clauses requiring equipment
manufacturers to have a record of satisfactory operation for a
specified period of time or of bonds or deposits to guarantee
replacement in the event of failure is restricted to special
cases where the grantee's engineer adequately justifies any
such requirement in writing. Where such justification has been
made, submission of a bond or deposit shall be permitted instead
of a specified experience period. The period of time for which
the bond or deposit is required should not exceed the experience
period specified.
(d) Buy American.
(1) Definitions. As used in this subpart, the following
definitions apply:
(i) "Construction material" means any article,
material, or supply brought to the construction
site for incorporation in the building or work.
(ii) "Component" means any article, material,
or supply directly incorporated in construction
material.
(iii) "Domestic construction material1^ means an
unmanufactured construction material which has
been mined or produced in the United States, or
a manufactured construction material which has
been manufactured in the United States if the
cost of its components which are mined, produced,
or manufactured in the United States exceeds
50 percent of the cost of all its components.
(iv) "Nondomestic construction material" means
a construction material other than a domestic
construction material.
(2) Domestic Preference. Domestic construction material
may be used in preference to nondomestic materials if it
is priced no more than 6 percent higher than the bid or
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offered price of the nondomestic materials including
all costs of delivery to the construction site, and
any applicable duty, whether or not assessed. Compu-
tations will normally be based on costs on the date
of opening of bids or proposals.
(3) Waiver. The Regional Administrator may waive
the Buy American provision based upon those factors
that he considers relevant, including:
(i) Such use is not in the public interest;
(ii) The cost is unreasonable;
(iii) The Agency's available resources are not
sufficient to implement the provision, subject to
the Deputy Administrator's concurrence;
(iv) The articles, materials or supplies of the
class or kind to be used or the articles, materials,
or supplies from which they are manufactured are not
mined, producted, or manufactured in the United
States in sufficient and reasonably available com-
mercial quantities or satisfactory quality for the
particular project; or
(v) Application of this provision is contrary to
multilateral government procurement agreements,
subject to the Deputy Administrator's concurrence.
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WOV 1 5 1373
CONSTRUCTION GRANTS
PROGRAM REQUIREMENTS MEMORANDUM
PRM 79-3
SUBJECT: Revision of Agency Guidance for Evaluation of Land
Treatment Alternatives Employing Surface Application
/An t!>^
JCMottfTng,
FROM: ThomasJCMottfTng, Assistant Administrator
Water and Wasp Management (WH-556)
M I
TO: Regional Administrators (Regions I thru X)
I. PURPOSE
This memorandum consolidates and updates Agency policy and guidance
for evaluation of land treatment alternatives using slow rate, rapid
infiltration, or overland flow processes in the Construction Grants
Program. It provides guidance on the extent and nature of material to
be included in facility plans to ensure that these land treatment alter-
natives have been given thorough evaluation.
II. DISCUSSION
Evaluation of land treatment in facilities planning has been
mandatory under PL 92-500 (the Act) since July 1, 1974. The EPA con-
struction grants regulations as published in the Federal Register
vol. 39, no. 29, February 11, 1974, provided for coverage of land
application techniques in facility planning [35.917-1 (d)(5)(iii)].
Three land application (land treatment) techniques were included in the
description of alternative techniques for best practicable treatment
published in October 1975. Many other technical information bulletins,
PGM's, and PRM's have been issued as guidance for the evaluation of land
treatment alternatives in the Construction Grants Program.
This approach was used to provide the latest information available
to the Regional Offices with a minimum of delay. While the objective of
timely distribution of technical information and guidance has been
achieved, this piecemeal distribution has also resulted in some disparities
in the interpretation and implementation of policy.
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Distribution of the Process Design Manual for Lanfl Treatment of
Municipal. Wastewater (EPA 625/1-77-008) consolidates most of the technical
information on surface application approaches into a single reference
source. This consolidation of technical information provides a sound
basis from which to establish more consistent and effective implementation
of Agency policy on land treatment alternatives using the slow rate,
rapid infiltration, or overland flow processes.
In the process of coordinating with the Regions on specific projects
involving land treatment, OWPO staff has had the opportunity to review a
number of selected facility plans with respect to their handling of land
treatment alternatives. In addition to providing information pertinent
to the specific projects being evaluated, this review has been used to
determine what, if any, changes in guidance are needed to achieve more
consistent and complete evaluation of land treatment alternatives.
Areas being considered include technical assistance and staff training
as well as revision of guidance documents.
The results of this review to date show that land treatment technologies
have had and continue to have inadequate assessment in many instances.
In addition and for substantially more cases, detailed coverage of land
treatment has missed the mark for a variety of reasons. Three of the
frequently encountered reasons are: (1) overly conservative and,
consequently, costly design of slow rate (irrigation) systems, (2)
failure to consider rapid infiltration as a proven and implementable
land treatment alternative, and (3) provision for a substantially higher
and more costly level of preapplication treatment than is needed to
protect public health and ensure design performance.
Such inadequate assessment of land treatment alternatives has led
to rejection of land treatment in cases where it appears that a thorough
assessment would identify less costly alternatives utilizing the recycling
and reclamation advantages of land treatment. Consistent with the
revised construction grants regulations resulting from enactment of
PL 95-217, award of Step 1 grants and subsequent approval of facility
plans must ensure that the selected alternative is cost-effective and
emphasizes energy conservation and recycling of resources. This is
important both to meet the statutory requirements of the law and to
provide the maximum pollution control benefits attainable with the funds
allocated to the Construction Grants Program.
The Administrator's memorandum of October 3, 1977, emphasizes that
the Agency grants program will include thorough consideration of land
treatment as compared to conventional treatment and discharge to surface waters,
This program requirements memorandum is designed to consolidate the
existing base of guidance into a uniform but still flexible set of
guidelines for slow rate, rapid infiltration, and overland flow systems.
This should improve our capability to effectively and consistently
implement the Agency policy on recycling and reclamation through land
treatment alternatives.
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III. POLICY
The Administrator's memorandum of October 3, 1977 (Attachment A)
spells out three major points of policy emphasis on land treatment of
municipal wastewater as follows:
1. The Agency will press vigorously for implementation of land
treatment alternatives to reclaim and recycle municipal
wastewaters.
2. Rejection of land treatment alternatives shall be supported by
a complete justification (reason for rejection shall be well
documented in the facilities .plan).
3. If the Agency deems the level of preapplication treatment to
be unnecessarily stringent, the costs of achieving the excessive
level of preapplication treatment will not be considered as
eligible for EPA cost sharing when determining the total cost
of a project.
These points highlight the Agency's role in implementing the legislative
mandates of PL 92-500 and PL 95-217. PL 92-500 required EPA to encourage
waste treatment management that recycles nutrients through production of
agriculture, silviculture, or aquaculture products. PL 95-217 re-
emphasizes the intent to encourage innovative/alternative systems including
land treatment with many tangible incentives including (1) the "115%"
cost preference, (2) 85% Federal grants with the specific set asides,
(3) the eligibility of land for storage, and (4) 100% grants for modification
or replacement if project fails to meet design .criteria. It is imperative
that the Agency moves positively and uniformly to implement land treatment
which is clearly identified as an innovative/alternative technology
which recycles nutrients and conserves energy in conjunction with wastewater
management.
IV. IMPLEMENTATION
The guidance detailed in this PRM will apply to all facility
planning grants (Step 1) awarded 30 days after the date of this PRM. In
addition it should be applied on a case-by-case basis to those unapproved
facility plans for which it appears that further assessment of land
treatment alternatives could result in: (1) the timely and effective
implementation of a reclamation and recycling alternative; and (2)
benefits to the applicant while making better use of EPA construction
grant funds.
A. Action Required
Facility plans in which land treatment alternatives are eliminated
with only cursory coverage will be rejected as not fulfilling Agency
requirements. A facility plan should not be approved until the coverage
of these land treatment alternatives satisfies the guidance detailed
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below. As a minimum, the coverage of these land treatment processes
will include assessment of at least one slow rate (irrigation) alternative
and one rapid infiltration alternative. Coverage of an overland flow
alternative will be optional (case-by-case) until additional information
which is presently being developed furnishes design information for
routine construction grant implementation. The technical design basis
of these land treatment alternatives will be in accordance with the "EPA
Design Manual on Land Treatment" (EPA 625/1-77-008), and "Costs of
Wastewater Treatment by Land Application" (EPA 430/9-75-003). To be
adequate, coverage of these land treatment alternatives shall include
enough detail to support development of costs, except in those cases
where thorough screening for available sites shows no suitable sites
within economic transport distances. Designs for slow rate systems and
rapid infiltration systems will include preapplication treatment which
is in accord with the discussion of preapplication in the Design Manual
(pages 5-26 thru 5-30) and summarized in Attachment B.
A universal requirement to reduce biochemical oxygen demand and
suspended solids to 30 mg/1 and to disinfect to an average fecal coliform
count of 200/100 ml will be considered as excessively stringent preappli-
cation treatment if specified for all land treatment alternatives.
States shall be requested to reconsider use of such universal and
stringent preapplication treatment requirements when it is established
that a lesser level of preapplication treatment will protect the public
health, protect the quality of surface waters and groundwater, and will
ensure achievement of design performance for the wastewater management
system.
States should be encouraged to adopt standards which avoid the use
of uniform treatment requirements for land treatment systems, including
a minimum of secondary treatment prior to application to the land. The
EPA guidance on land treatment systems specifies ranges of values and
flexible criteria .for evaluating factors such as preapplication treatment,
wastewater application rates and buffer zones. For example, simple
screening or comminution may be appropriate for overland flow systems in
isolated areas with no public access, while extensive biochemical oxygen
demand and suspended solids control with disinfection may be called for
in the case of slow rate systems in public access areas such as parks or
golf courses.
B. Specific Guidance
The scope of work for preparation of a facility plan will provide
for thorough evaluation of land treatment alternatives. This evaluation
of land treatment alternatives may be accomplished in a two-phase approach.
Such a two-phase approach would provide flexibility for establishing
general site suitability and cost competitiveness before requiring
extensive on-site investigations. The first phase of the two-phase
approach would include adequate detail to establish whether or not sites
are available, wastewater quality is suitable, and land treatment is
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cost competitive. The second phase would include in-depth investigation
of sites and the refinement of system design factors to complete all of
the requirements for preparing a facility plan. Approval of a facility
plan will ensure that the following details for evaluation of land
treatment are clearly delineated in the plan.
1. Site Selection. A regional map shall be included to show the
tracts of land evaluated as probable land treatment sites. The
narrative discussion of site evaluation should detail the reasons
for rejection of tracts as well as the availability of tracts used
in the preliminary design for land treatment alternatives.
Table 2-2 of the Design Manual (Attachment C) delineates general
site characteristics for land treatment alternatives which the
narrative should cover in detail.
Categorical elimination of land treatment for lack of a
suitable site (during phase one of a two-phase evaluation) should
be documented with support materials showing how the applicant made
the determination. For example, elimination for lack of suitable
soils should be documented with soils information from the area
Soil Conservation Service representatives or other soil scientists
who may be available. Any categorical elimination of land treatment
should demonstrate that additional engineering necessary to overcome
site constraints would make the .alternative too costly to fund in
accordance with the cost-effectiveness requirements of the Taw.
2. Loading Rates and Land Area. The values for these parameters
evaluated in the facility plan should concur with the technically
established ranges for application rates and land area needed for
a system. The cost of land treatment is sensitive to these factors
and overly conservative design unduly inflates the cost of technically
sound alternatives. Designs in a facility plan should fall within
the general ranges given in Table 2-1 and Figure 3-3 of the Design
Manual. Designs falling outside of these ranges should do so only
because of extenuating circumstances peculiar to the site. These
extenuating circumstances should be discussed in detail. Table 2-1
(Attachment B) is recommended as a quick reference for determining
that designs are reasonable.
3. Estimated Costs. The estimated costs of land treatment
alternatives should be comparable to those obtained by using
EPA 430/9-75-003 pages 59-127, updated using local construction
cost indices. Cost estimates generated by using this source are
being compared to actual costs for recently constructed facilities.
If this comparison shows that the curves in EPA 430/9-75-003 need
adjustment, corrected curves will be made available as necessary.
Elimination of land treatment in the cost-effective analysis
because of land costs or transport costs should be documented by
means of an actual evaluation for the cost of land or cost of
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transport. This evaluation should show clearly that the cost of
land or the cost of transport does rule out land treatment using
the approach shown in "Cost-Effective Comparison of Land Application
and Advanced Wastewater Treatment" (EPA 430/9-75-016). Examples
on pages 23-24 (Attachment D) of that source show how to make these
comparisons.
4. Preapplication Treatment. The level of preapplication treatment
prior to storage or actual application to the land should be in
accordance with the guidance given for screening wastewaters to be
applied to the land in the Design Manual. A universal minimum of
secondary treatment for direct surface discharge as published in
the August 17, 1973 Federal Register and later modified (Federal
Register July 26, 1976 and October 7, 1977) will not be accepted
because it is inconsistent with the basic concepts of land treatment.
Imposition of a defined discharge criteria at an intermediate point
in a treatment train is, in most instances, an unnecessarily
stringent preapplication treatment requirement as stated in the
Administrator's memorandum dated October 3, 1977. Criteria imposed
at an intermediate point should be for the purpose of ensuring
overall system performance in the same context that primary sedi-
mentation precedes biological secondary treatment by trickling
filter or activated sludge processes.
Assessment of the level of preapplication treatment proposed
should be in accord with the discussion in Section 5.2 (pages 5-26
to 5-30) of the Design Manual. Guidelines for evaluating the level
of preapplication for slow-rate, rapid infiltration, and overland
flow systems in relation to existing state regulations, criteria
and guidelines are included in Attachment E. Preapplication
treatment criteria more restrictive than the ranges of treatment
levels described in Appendix E will be considered unnecessarily
stringent unless justified on a case-by-case basis. When the more
stringent preapplication treatment criteria cannot be justified,
the EPA will consider that portion of the project to meet EPA
guidance as eligible for Agency funding. The costs 'Of the additional
preapplication increment needed to meet more stringent preapplication
treatment requirements imposed at the state or local level would be
ineligible for Agency funding and thus would be paid for from state
or local funds.
5. Environmental Effects. Assessing the environmental effects of
land treatment alternatives involves a somewhat different concept
than for conventional treatment and discharge to surface waters.
The assessment for land treatment should include emphasis on the
quality and quantity of both surface and groundwater resources; on
energy conservation as well as energy demands; on pollutant (resource)
recycling as well as chemical needs, and on land use in the overall
coverage of environmental effects.
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The assessment should determine that the proposed land treatment
system is in accord with Agency policy on groundwater protection.
The Agency policy for groundwater resulting from land treatment
systems is set forth in the criteria for Best Practicable Waste
Treatment Technology (BPWTT). These criteria specify that the
groundwater resulting from a land treatment system must meet different
requirements depending on current use and quality of the existing
groundwater. The basic thrust of these criteria is to protect
groundwater for drinking water purposes by specifying adherence to
the appropriate National Primary Drinking Water Standards. The
BPWTT criteria further require land treament systems which are
underdrained or otherwise designed to have a surface discharge to
meet the standards applicable to any treatment and discharge
alternative. The criteria are fully described in 41 FR 6190
(February 11, 1976) which is attached as Appendix F.
An overall Agency policy statement on groundwater protection
is scheduled for issuance in the near future. The draft Agency
groundwater policy is generally consistent with present criteria
for land treatment systems. However, any revisions to the present
guidance on site evaluation and system monitoring as a result of
this statement will have to be accounted for as they are developed.
In the meantime, existing guidance should be used to evaluate
groundwater influences.
Attachments
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V. REFERENCES
Process Design Manual for Land Treatment of Municipal Wastewater
EPA 625/1-77-008 October, 1977.
October 3, 1977 memorandum from Administrator:"EPA Policy on
Land Treatment of Municipal Wastewater".
"Cost of Wastewater Treatment by Land Application" Technical Report
EPA-430/9-75-003 June, 1975.
"Cost-Effective Comparison of Land Application and Advanced
Wastewater Treatment" Technical Report EPA-430/9-75-016,
November, 1975.
Secondary Treatment Information Federal Register 38(129),
August 17,, 1973, pgs 22298-22299.
Secondary Treatment Information Federal Register 41(1440,
July 26, 1976, pp. 30786-30789.
Suspended Solids Limitations Federal Register 42(195),
October 7, 1977, pp. 54664-54666.
Water Quality Criteria 1972 EPA-R3-73-033, March 1973, pp. 323-366.
Quality Criteria for Water, USEPA, July, 1976.
Alternative Waste Management Techniques for Best Practicable
Waste Treatment EPA 430/9-75-013, October, 1975.
Final Construction Grants Regulations Federal Register 39, No. 29
February 11, 1974.
VI. ATTACHMENTS
Attachment A Administrator's Oct. 3, 1977 memo "EPA Policy on
Land Treatment of Municipal Wastewater"
Attachment B Table 2-1 from Design Manual
Attachment .C Table 2-2 from Design Manual
Attachment D Pages 23-24 from EPA 430/9-75-016
Attachment E Guidance for assessing level of preapplication
Attachment F Alternative Waste Management Techniques (BPWTT)
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ATTACHMENT A
UN! 1 ED STATES ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON. D C. JO-l'iO
OCT 3 1977
THE ADMINISTRATOR
SUBJECT:
FROM:
TO:
EPA Policy on Lan
Wastewater
The Administr
r I /) ^
earjnent of/lyrmtfpal
Assistant Administrates and
Regional Administrators (Regions [-X]
President Carter's recent Environmental Message to the Congress
emohasized the design and construction of cost-effective publicly owned
wastewater treatment facilities that encourage water conservation as
well as adequately treat wastewater. This serves to strengthen the
encouragement under the Federal Water Pollution Control Act Amendments
of 1972 (P.L. 92-500} to consider wastewater reclamation and recycling by
land treatment processes.
At the time P.L. 92-500 was enacted, it was the intent of Congress
to encourage to the extent possible the development of wastewater manage-
ment policies that are consistent with the fundamental ecological principle
that all materials should be returned to'the cycles from which they were
generated. Particular attention should be given to wastewater treatment
processes which renovate and reuse wastewatsr as well as recycle the
organic matter'and nutrients in a beneficial manner. Therefore, the
Agency will press vigorously for publicly owned treatment works to
utilize land treatment processes to reclaim and recycle municipal wastewater,
RATIONALE
Land treatment systems involve the use of plants and the soil to
remove previously unwanted contaminants from wastewaters. Land treatment
is capable of achieving removal levels comparable to the best available
advanced wastewater treatment technologies while achieving additional
benefits. The recovery and beneficial reuse of wastewater and its
nutrient resources through crop production, as well as wastewater
treatment and reclamation, allow land treatment systems to accomplish
far more than most conventional treatment and discharge alternatives.
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The application of wastewater on land is d practice that has been
used for many decades; however, recycling and reclaiming wastewater that
may involve the planned recovery of nutrient resources as part of a
designed wastewater treatment facility is a relatively new technique.
One of the first such projects was the large scale Muskegon, Michigan,
land treatment demonstration project funded under tne Federal Water
Pollution Control Act Amendments of 1966 (P.L. 84-560), whicn began
operations in May 1974.
Reliaole wastewater treatment processes that utilize land treatment
concepts to recycle resources through agriculture, silviculture and
aquaculture practices are available. The technology for planning,
designing, constructing and operating land treatment facilities is
adequate to meet both 1983 and 1985 requirements and goals of P.L. 92-
500.
Land treatment is also presently in extensive use for treatment of
•nany industrial wastewaters, particularly those .vi th easily degraded
•irqanics such as food processing. Adoption of suitable in-plant pretreatnent
for the rsnoval of excessive metals and toxic substances would expand
f>e potential for land treatment of industrial wastewater and further
enhance the potential for utilization of municipal wastswater and sludges
fqr agricultural purposes.
APPROACH
Because land treatment processes contribute to the reclamation and
recycling requirements of P.L. 92-500, they should be preferentially-j
considered as an alternative wastewater management technology. Sucn
consideration is particularly critical for smaller ccmmunities. While
it is recognized that acceptance, is not universal, the utilization ofj
land treatment systems has the potential for saving billions of dollars.
This will benefit not only the nationwide water pollution control program,
but will also provide an additional mechanism for the recovery and ^
recycling of wastewater as a resource.
EPA currently requires each applicant for construction grant funds
to make a conscientious analysis of wastewater management alternatives
with the burden upon the applicant to examine all available alternative
technologies. Therefore, if a method that encourages water conservation,
wastewater reclamation and reuse is not recommended, the applicant should
be required to provide complete justification for tne rejection of
land treatment.
Imposition of stringent wastewater treatment requirements prior to
land application nas quite often nullified the cost-effectiveness of
land treatment processes in the past. We must ensure that appropriate
Federal, State and local requirements and regulations are imposed at the
B-19
-------
proper point in the treatment system .imj are not 'ised in a manner that
may arbitrarily block land treatment projects VJhi-never States insist
upor placing unnecessari1y strinnent preapplicat~on treatment require-
ments upon land treatment, such as requiring EPA secondary effluent
quality in all cases prTpr to application on the land, tne unnecessary
wastewater treatment faci1ities wi11 not be funded by EPA. This should
encourage the States to re-examine -and revise their criteria, and so
reduce the cost burden, especially to small communities, for construction
and operation of unnecessary or too costly facilities. The reduction of
potentially toxic metals and organics in industrial discharges to municipal
systems often is critical to the success of land treatment. The develooment
and enforcement at the local level of pretreatment standards that are
consistent with nati'onal pretreatment standards should be required as an
integral part of any consideration or final selection of land treatment
alternatives. In addition, land treatment alternatives must be fully
coordinated with on-going areawide planning under section 208 of the
Act. Section 208 agencies should be involved in the review and development
of land treatment options.
Research will be continued to further improve criteria for preappli-
cation treatment and other aspects of land treatment processes. This
will add to our knowledge and reduce uncertainties .about health and
environmental factors. I am confident, however, that land treatment of
municipal wastewaters can be accomplished without adverse effects on
human health if proper consideration is given to design and management
of the system.
INTER-OFFICE COORDINATION
The implementation of more recent mandates from the Safe Drinking
Water Act (P.L. 93-532), the Toxic Substances Control Act (P.L. 94-469),
and the Resource Conservation and Recovery Act of 1976 (P.L. 94-580)
must1be closely coordinated with the earlier mandate to recycle wastes
and fully evaluate land treatment in P.L. 92-500. Agencywide coordination
is especially important to the proper management of section 201 of P.L.
92-500, because the construction and operation of thousands of POTW's
involve such a broad spectrum of environmental issues. A concerted
ef-fort must be made to avoid unilateral actions, or even the appearance
of unilateral actions, which satisfy a particular mandate of one Act
while inadvertently conflicting with a major Agency policy based upon
another Act. The intention of P.L. 92-500, as it concerns land treatment,
is compatible with the pertinent aspects of more recent environmental
legislation.
ACTION REQUIRED
Each of you must exert maximum effort to ensure that the actions of
your staffs reflect clearly visible encouragement of wastewater reclamation
and recycling of pollutants through land treatment processes in order to
move toward the national goals of conserving water and eliminating the
discharge of pollutants in navigable waters by 1985.
B-20
-------
This policy will apply to all future municipal construction grant
activities, as well as all current grant applications in the Step 1
category that have not been approved as of this date. Detailed information
and guidance for implementation of this policy is under preparation and will
be issued in the near future.
B-21
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B-22
-------
TABLE 2-2
COMPARISON OF SITE CHARACTERISTICS FOR LAND TREATMENT PROCESSES
CO
I
Principal
Other processes
Characteristics
Slow rate
Hap id infiltration
Overland flow Wetlands
Subsurface
Slope
Less than 20t un culti-
vated land,.less than
401 on nuiicul I i vated
land
(lot critical; excessive Finish slopes Usually less Hot critical
slopes renuiie much 2 to UX than 51
earthwoi k
Soil pcnneabll 1 ty
Depth to
ground. /a ter
Cluiuttc
restrictions
Moderately slow to
moderately rapid
2 to 3 ft (minimum)
Storage often needed
for cold weather and
prec ipl tat ion
Rapid (sands, loau^y
Sands)
10 ft (lesser depths
me acceptable where
underdi ainaye is
provided)
(lone (possibly modify
operation In cold
Weather)
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silts, aiid
sol Is with
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Not critical
Sturaije often
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cold weather
Slow to
moderate
Not critical
Storage may
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for cold
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Slow to rapid
Not critical
None
1 ft " 0.305 m
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-------
Example No. 2
ATTACHMENT D
Requirements. An existing 20-mgd activated sludge plant is
required to upgrade its effluent quality to meet the following
criteria:
BCD - 10 mg/1
SS - 10 mg/1
N - 3 mg/1
P - 0.5 mg/1
Alternatives. It is evident from a review of Table 2 that
the only methods of treatment capable of providing the neces-
sary degree of treatment are AWT-4 and irrigation. In this
example, the cost of AWT-4 is compared with that of irrigation
under varying conditions of conveyance distance (Case A) and
land costs (Case B). Sines secondary treatment is existing,
activated sludge or aerated lagoon will not be necessary.
Case A - Consider a moderately favorable site for
irrigation, a distance of S miles away from
the existing treatment plant site. How
much can be paid for land and have the
irrigation system competitive with the
AWT-4 system?
Table 12. COST COMPARISON FOR CASE A
Troaeatanc •
.retnod Cast component
AhT-4 AWT-'l
Existing activated
sludqe adjustment
Total
Irrigation Irrigation system
Aerated lagoon
adjustment
Land cost
Subtota I
Amount available
Jor land - i28. 0-13.0)
Total icei, .ictus
AllowubL'i Tost/ion.'
20 .Tiqd USC/l.OOO aaL.IUO-1)
Cose
•5/1,000 gal. Source
44.
-(16.
2B.
H.
-(•>.
-(C.
U.
15.
*,300
4 son
0
01
0
0
J)
22.
0
0
Figure 1
Figure 1
Figure 1
Figure 1
Table 7
Table 7
B-24
-------
Conclusions. Under the assumed site conditions for the
irrigation system, as much as $4,500 per acre could be paid
for land and have the irrigation system competitive with
AWT-4.
Case B - Consider a moderately favorable irrigation site
at a cost of $2,000 per acre. How far away from
the existing treatment plant could the site be
and have the irrigation system competitive with
AWT-4?
Table 13. COST COMPARISON FOR CASE B
Treatment
nethoc
Cost component
Cost
C/1,OOC gal. Source
AWT-4- From Case A 28.C Figure 1
Irrigation Irrigation system 24.0 Figure 1
Aerated lagoon adjustment -(4.3) Figure 1
Conveyance cost -(1.7) Table 7
Subtotal 18.0
Anount available for
conveyance = (28.C - 18.0) 10.0
Allowable distance, miles 33 Table 4
Conclusions. Under the assumed site conditions for the
irrigation system, wastewater could be conveyed as far as
33 miles and have irrigation be competitive with AWT-4.
Special conditions such as river or highway crossings and
easements may add substantial costs and reduce this distanc
somewhat.
B-25
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ATTACHMENT E
Guidance for Assessing Level of Preapplication Treatment
I. Slow-rate Systems (reference sources include Water Quality Criteria
1972, EPA-R3-73-003, Water Quality Criteria EPA 1976, and various
state guidelines).
A. Primary treatment - acceptable for isolated locations with
restricted public access and when limited to crops not for
direct human consumption.
B. Biological treatment by lagoons or inplant processes plus
control of fecal coliform count to less than 1,000 MPN/100 ml
acceptable for controlled agricultural irrigation except for
human food crops to be eaten raw.
C. Biological treatment by lagoons or inplant processes with
additional BOD or SS control as needed for aesthetics plus
disinfection to log mean of 200/100 ml (EPA fecal coliform
criteria for bathing waters) - acceptable for application in
public access areas such as parks and golf courses.
II. Rapid-infiltration Systems
A. Primary treatment - acceptable for isolated locations with
restricted public access.
B. Biological treatment by lagoons or inplant processes - acceptable
for urban locations with controlled public access.
III. Overland-flow Systems
A. Screening or comminution - acceptable for isolated sites with
no public access.
B. Screening or comminution plus aeration to control odors during
storage or application - acceptable for urban locations with
no public access.
B-26
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ENVIRONMENTAL PROTECTION
AGENCY
482-oj
ALTERNATIVE WASTE MANAGEMENT
TECHNIQUES FOR 3EST PRACTICABLE
WASTE TREATMENT
Supplement
Pursuant to Section 304(cl) (2) of the
Federal Water Pollution Control Act
Amendments of 1972 (Pub. L. 92-500) ,
the Environmental Protection Agency
(EPA), gave notice on October 23, 1975
(40 PR 49598) that Alternative Waste
Management Techniques for Best Prac-
ticable Waste Treatment has been pub-
lished in final form. The final report
contains the criteria for best practicable
waste treatment technology and infor-
mation on alternative waste manage-
ment techniques.
The criteria for Best Practicable Waste
Treatment for Alternatives employing
land application techniques and land
utilization practices required that the
ground water resulting from land appli-
cation of wastewater meet the standards
for chemical quality [inorganic chemi-
cals] and pesticides [organic chemicals}
specified in the EPA Manual for Evalu-
ating Public Drinking Water Supplies in
the case of groundwater which poten-
tially can be used for drinking water
supply. In addition to the standards for
chemical quality and pesticides, the
bacteriological standards [microbiologi-
cal contaminants] specified in the EPA
Manual for Evaluating Drinking Water
Supplies were required in the case of
srroundwater which is presently being
used as a drinking water supply. The
pertinent section of the EPA Manual for
Evaluating Public Drinking Water Sup-
plies was included as Appendix D of the
Alternative Waste Management Tech-
niques for Best Practicable Waste Treat-
ment report.
Also specified in the Criteria for Best
Practicable Waste Treatment is that
"any chemical, pesticides, or bacterio-
logical standards for drinking water sup-
ply sources hereafter issued by EPA shall
automatically apply in lieu of the stand-
ards in the EPA Manual for Evaluating
Public Drinking Water Supplies. The
National Interim Primary Drinking
Water Regulations were published in
final form on December 24, 1975.
In consideration of the foregoing,
Chapter II and Appendix D of Alterna-
tive Waste Management Techniques for
Best Practicable Waste Treatment shall
read as follows.
Dated: February 4, 1976.
RUSSELL E. TRAIN,
Administrator.
CHAPTER II
CRITERIA FOR BEST PRACTICABLE WASTE
TREATMENT
Applicants for construction prant funds
authorized by Section 201 of the Act must
have evaluated alternative waste treatment
management techniques and selected the
technique which will provide for the appli-
cation of beat prncUciiblc wnslo treatment
technology. Alternatives must bo considered
lu three brond broiul categories: treatment
find discharges into imvlgnblo waters, Innd
application mid utilization practices, and
rouso of treated wastev/ater. An alternative
Is "best practicable" If it Is determined
to bo cost-oflectlvo In accordance with the
procedures set forth in 40 CFB Part 35
(Appendix B to this document) and if it
will meet the criteria set forth below.
(A) Alternatives Employing Treatment
and Discharge into Navigable Waters. Pub-
licly-owned treatment works employing
treatment and discharge into navigable wa-
ters shall, as a minimum, achieve the degree
of treatment attainable by the application
of secondary treatment as defined in 40 CFB
133 (Appendix C). Requirements for addi-
tional treatment, or alternate management
techniques, will depend on several factors,
including availability of cost-effective tech-
nology, cost and the specific characteristics
of the affected receiving water body.
(B) Alternatives Employing Land Appli-
cation" Techniques and Land Utilization
Practices. Publicly-owned treatment works
employing land application techniques and
land utilization practices which result In a
discharge to navigable waters shall meet the
criteria for treatment and discharge under
Paragraph (A) above.
The ground water resulting from the land
application of wastewater, Including the af-
fected native ground water, shall meet the
following criteria:
Case 1: The ground water can potentially
be used for drinking water supply.
(1) The maximum contaminant levels for
inorganic chemicals and organic chemicals
specified in the National Interim Primary
Drinking Water Regulations (40 CFB 141)
(Appendix D) for drinking water supply sys-
tems should not be exceeded except as Indi-
cated below (see Note 1).
(2) If the existing concentration of a
parameter exceeds the maximum contami-
nant levels for Inorganic chemicals or organic
chemicals, there should not be an Increase
in the concentration of that parameter due
to land application of wastewater.
Case II: The ground water is used for
drinking water supply.
(1) The criteria for Case I should be met.
(2) The maximum microbiological con-
taminant levels for drinking water supply
systems specified in the National Interim
Primary Drinking Water Regulations (40
CFR 141) (Appendix D) should not be ex-
ceeded In cases where the ground water la
used without disinfection (see Note 1):
Case III: Uses other than drinking water
supply.
(1) Ground water criteria should be estab-
lished by the Regional Administrator based
on the present or potential use of the ground
water.
The Regional Administrator In conjunction
with the appropriate State officials and the
grantee shall determine on a slte-by-gite
basis the nreas in the vicinity of a specific
land application site where the criteria In
Case I, It, and III shall apply. Specifically
determined shall be the monitoring require-
ments appropriate for the project site. This
determination shall be made with the objec-
tive of protecting the ground water for use
ns a drinking water supply and/or other
designated uses as appropriate and prevent-
ing irrevocable damage to ground water. Re-
quirements shall include provisions for mon-
itoring the effect on the native ground water.
(C) Alternatives Employing Reuse. The
total quantity of any pollutant in the effluent
from a reuse project which 13 directly at-
tributable to the effluent from a publicly-
B-27
-------
owned treatment works shall not exceed that
which would have been allowed under Par-
ixpruplis (A) and (B) above.
NOTE 1.—Any amendments of the National
Interim Primary Drinking Water Regulations
and any National Revised Primary Drinking
Water l(ep;iiliitlons hereafter Irutucd by EPA
prescribing standards for public water sys-
tem relating to Inorganic chemicals, organic
chemicals or microbiological contamination
shall automatically apply In tho same man-
ner as the National Interim Primary Drink-
ing Water Regulations.
APPENDIX D
GROUND WATER REQUIREMENTS
The following maximum contaminant
levels contained In the National Interim Pri-
mary Drinking Water Regulations (40 CFR
141) are reprinted for convenience and clar-
ity. The National Interim Primary Drinking
Water Regulations were published in final
form In the FEDERAL REGISTER on Decem-
ber 24, 1975. In accordance with the criteria
for best practicable waste treatment, 40 CFR
141 should he consulted in Its entirety when
applying the standards contained therein to
wastewater treatment systems employing
land appplication techniques and land uti-
lization practices.
maximum contaminant levels for inoi-
ganic chemicals. The following are the max-
imum levels of Inorganic chemicals other
than fluoride:
Level
(milligrams
Contaminant: per liter)
Arsenic 0.05
Barium 1.
Cadmium 0. 010
Chromium 0.05
Lead - 0.05
Mercury 0.002
Nitrate (as N) - 10.
Selenium 0. 01
Silver _ - 0.05
The maximum contaminant levels .for
fluoride are:
Temperature
decrees
Fahrenheit *
Degrees Celsius
Level
(milligram*
- per liter)
53 8 to W 3
58.41063.8
63.0 to 70.0
70 7 to 79 2
121 to 14.0. -.
14.7 to 17.6
17.7 to 21.4
21.5 to 26.2.
28.3 to 32.5
2.4
2.2
2.0
1.8
1.6
1.4
i Annual average of tho maximum dally air tem-
perature.
Maximum contaminant levels for organic
chemicals. The following are the maximum
contaminant levels for organic chemicals:
Level
(•milligram
(a) Chlorinated hydrocarbons: per liter)
Endrin (1,2,3,4,10,10-Hexachloro-
6,7 - epoxy - l,4,4a,5,6,7,8,8a-oc-
tahydro-l,4-endo,endo - 6,8-dl-
methano naphthalene) 0.0002
Llndane (1,2,3,4,5,8 - Hexachloro-
cycloh'exane, gamma Isomer)— 0.004
Methoxychlor (l,l,l-Trlchloro-2,
2-bis [p-methoxyphenyl] eth-
ane) — 0.1
Toxaphene (OlnH10Cl, - Technical
chlorinated camphene, 67 to 89
percent chlorine) 0.005
(b) Chlorophenoxys:
2,4-D (2,4-Dlchlorophenoxyacetic
acid) - — 0.1
2,4,5-TP Silvex (2,4,5-Trlchloro-
phenoxyproplonlc acid) 0. 01
Maximum microbiological contaminant
levels. The maximum contaminant levels' for '
coliform bacteria, applicable to community
water systems and non-community water
systems, are as follows:
(a) When the membrane filter technique
pursuant to § 141.21 (a) Is used, the number
of coliform bacteria shall not exceed any of
the following:
(1) One per 100 mllllllters as the arith-
metic mean of all samples examined per
month pursuant to § 141.21 (b) or (c);
(2) Four per 100 mllllllters In more than
one sample when less than 20 are examined
per month; or
(3) Four per 100 mllltllters In more than
five percent of the samples when 20 or more
are examined per month.
(b) (1) When the fermentation tube
method and 10 mlllllltbr standard portions
pursuant to § 141.21 (a) are used, colllorm
bacteria shall not be present in any of tho
following:
(1) More than 10 percent of tho portions In
any month pursuant to § 141.21 (b) or (c);
(11) Three- or more portions In more than
one sample when less than 20 samples are
examined per month; or
(lit) Three or more portions in more than
five percent of the samples when 20 or more
samples are examined per month.
(2) When the fermentation tube method
and 100 mllllliter standard portions pursuant
to § 141.21 (a) are used, coliform bacteria
shall not be present In'any of the following:
(1) Moro than GO percent of the portions
in any month pursuant to § 141.21 (b) or
(o);
(11) Five portions In more than one sample
when less than flve samples are examined
per month; or
(111) Five portions In moro than 20 percent
of the samples when flve or more samples
are examined per month.
(c) For community or non-community
systems that are required to sample at a rate
of less than 4 per month, compliance with
Paragraphs (a), (b) (1), or (2) shall be based
upon, sampling during a 3 month period, ex-
cept that, at the discretion of the State,
compliance may be based upon sampling
during a one-month period.
[PR Doc.76-3932 Filed 2-10-76;8:45 am]
B-28
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OFFICE OF WA I ER AND
HAZARDOUS MATERIALS
PROGRAM REQUIREMENTS MEMORANDUM
PRM# 79-8
SUBJECT: Small Wastewater Systems
FROM: John T. Rhett, Deputy Assistant Administrator
-------
limited conveyance systems serving clusters of households and small
commercial establishments and pressure and vacuum sewers. These
alternative sewers are specifically exempted from the collection sewer-
interceptor designations when planned for small communities and are not
subject to the collection system policy. These systems also include
other treatment works which employ alternative technologies listed in
Appendix E, 40'CFR 35, and serve communities of 3,500 population or- less
or the sparsely populated areas of larger communities.
A conventional system is a collection and treatment system consisting of
minimum-size (6 or 3 inches) or larger gravity collector sewers, normally with
manholes, force mains, pumping and lift stations and interceptors leading to
a central treatment plant employing conventional concepts of treatment as
defined in Section 5, Appendix E, 40 CFR 35.
Small alternative wastewater systems may be publicly or privately owned.
Privately owned systems (called "individual systems" in the Act and 40 CFR 35)
may serve only one or more principal residences or small commercial establish-
ments. Publicly owned systems may serve one or more users. Perpetual or
1ife-of-project easements or other binding convenant running with the land
affording complete access to and control of wastewater treatment works on
private property are tantamount to ownership of such works.
High wastewater user costs exceeding $200, $300, and even $500 annually
for households in some communities under 10,000 in population have resulted
from debt retirement costs for new collection systems or from high operation
and maintenance costs of new sophisticated plants. Extremely high cost
projects have culminated in political upheaval, refusal to connect into or
to pay after connecting into central sewers, violence at public meetings,
requests for injunctions, and filing suits against several parties, including
EPA. In most cases, all of the feasible alternatives were not considered in
the cost-effectiveness analysis and some systems were overdesigned by using
inflated population projections and excessive water usage data. In the past,
it has been difficult during facility plan review to pinpoint those projects
that have severe financial impacts.
Previous policy and facility planning guidance have called for verification
by the grantee that that community is able to raise the local share. PRM 76-3
requires the estimated operation and maintenance and debt retirement costs to
each user to be presented in clear, understandable terms at the facility
planning public meeting. In his letter of December 30, 1976, the Administrator
asked the Regional Administrators to pay careful attention to facility plans
where average local debt retirement costs per household exceed 1 percent of
annual median income and for which local debt retirement costs plus operation
and maintenance costs exceed 2 percent.
Guidelines modifying the 1 percent to 2 percent guide have been included
below to assist in identification of expensive projects for further analysis.
We are preparing a format with instructions for municipal officials and State
and Federal reviewers to use to determine the size of project the jnunicipality
can afford using readily available local financial data.
B-30
-------
Loan and grant programs of several Federal agencies for construction of
wastewater treatment works in the past usually have been handled individually
with little coordination among the agencies. This has resulted in unnecessary
paperwork, duplication, federally imposed administrative burdens, construction
of inappropriate or too sophisticated, costly facilities, fostering of
development on rural land, and poor structuring of local share debt .financing.
Under the Interagency Agreement for Rural Water and Sewer Projects,
Environmental Protection Agency (EPA), Farmers Home Administration (FmHA),
Economic Development Administration (EDA), Housing and Urban Development (HUD),
and Community Services Administration (CSA) will coordinate their efforts to
improve the delivery of Federal water and sewer programs to rural and semi-rural
communities. Major features include:
"Emphasis on alternatives that may have lower per capita capital and
operating costs and require less sophisticated technology and skill
to operate than conventional collection and treatment facilities;
o
A regular exchange of information among the agencies involved in
funding the project, including meeting periodically and using the
Federal Regional Councils;
°The facilitating of application and disbursement of funds for rural
water and sewer projects and informing communities of the range of
funding and other assistance available to them;
°The establishment of a universal data base for national wastewater
disposal and treatment needs;
"The more efficient use of the A-95 process of review by clearinghouse
agencies;
°Use of the same criteria to evaluate the financial impact of the pro-
posed system upon the community;
°Coordination of the review of facility plans between EPA and FmHA and
use of the plans by FmHA as their feasibility report to the extent
possible;
°The demonstration of compliance with Federal requirements under specific
statutes only once when communities are using funds from more than one
program with identical compliance requirements. Where agency regulations
differ in compliance requirements, agencies will work together to ensure
individual or coordinated review as appropriate.
Facility planning in some small communities with unusual or inconsistent
geologic features or other unusual conditions may require house-to-house
investigations to provide basic information vital to an accurate cost-effectiveness
analysis for each particular problem area. One uniform solution to all
the water pollution problems in a planning area is not likely and may not be
desirable. This extensive and time-consuming engineering work will normally
B-31
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result in higher planning costs which are expected to be justified by the
considerable construction and operation and maintenance cost savings of small
systems over conventional collection and' treatment works.'
Though house-to-house visits are necessary in some areas*, sufficient
augmenting information may be available from the local sanitarian, geologist,
Soil Conservation Service representative or other source to permit .preparation
of the cost-effective analysis. Other sources include aerial photography and
boat-carried leachate-sensing equipment which can be helpful in locating
failing systems. Detailed engineering investigation, including soil profile
examination, percolation tests, etc., on each and every occupied lot should
rarely be necessary during facility planning.
III. Policy
A. Funding of Publicly and Privately Owned Small Alternative Wastewater
Systems
1. Minimum Standards and Conditions
The Clean Water Act and the regulations implementing the Act
impose no restrictions on types of sewage treatment systems. These
alternative systems-are eligible for funding for State approved
certified projects when the following minimum standards and
conditions are met:
a. For both publicly and privately owned systems, the
public body must meet the requirements of 40 CFR 35.918-1
(b), (c), (e) through (j); 35.918-2 and 35.918-3.
A comprehensive program for regulation and inspection
of these systems must be established prior to EPA approval
of the plans and specifications. Planning for this compre-
hensive program shall be completed as part of the facility
plan. The program shall include, at a minimum, the
physical inspection of all on-site systems in the facility
planning area every three years with pumpouts and systems
renovation or replacement as required. The program shall also
include, at a minimum, testing of selected existing potable
water wells on an annual basis. Where a substantial number
of on-site systems exist, if necessary, appropriate
additional monitoring of the aquifer(s) in the facility
planning area shall be provided.
For privately owned systems the applicant must demonstrate
in the facility plan that the solution chosen is cost-effective
and selected in accordance with the cost-effectiveness
guidelines for the Construction Program, (Appendix A,
40 CFR Part 35). These systems are not eligible for a
15 percent cost preference for the alternative and innovative
processes and techniques in the cost-effectiveness analysis.
Publicly owned systems, however, are eligible for the 15 percent
cost preference.
B-32
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b. In addition to the conditions in paragraph A.I, privately
owned systems must meet the requirements of 40 CFR 35.918-1(a)
and (d) and the following:
(1) Provide facilities only for principal residences,
(see 40 CFR 35.918(a)(2)) and small commercial
establishments (i.e., those with annual or seasonal,
if not operated throughout the year, dry weather flows
of less than 25,000 gpd and more than one user
equivalent per day; e.g. 300 gpd). Not included
are second homes, vacation or recreation residences;
(2) Require commercial users to pay back the Federal
share of the cost of construction with no moratorium
during the industrial cost recovery study. The
25,000 gpd exemption does not apply for those
commercial establishments;
(3) Treat nonprofit and non-governmental institutional
entities such as churches, schools, hospitals and
charitable organizations, for purposes of this special
authority, generally the same as small commercial
establishments.
2. Other Eligible and Ineligible Costs
In addition to the costs identified in the Construction Grants
Regulations, 40 CFR 35.918-2, the following costs are also grant
eligible:
(a) Vehicles and associated capital equipment required for
servicing of the systems such as septage pumping trucks
and/or dewatered residue haul vehicles.
(1) Vehicles purchased under the grant must have as
their sole purpose, the transportation of liquid or
dewatered wastes from the collection point
(e.g., holding tanks, sludge-drying beds) to the
treatment or disposal facility. (Other mobile
equipment is allowable for grant participation as
provided for on pages VII-12 and 13, "Handbook of
Procedures, Construction Grants Program for Municipal
Uastewater Treatment Works.")
(2) If vehicles or equipment are purchased the
grantee must maintain property accountability in
accordance with OMB Circular A-102 and 40 CFR 30.810.
B-33
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(b) Septage treatment plants (eligible for 85 percent
grant funding as part.of an alternative system).
(c) Planning for establishment of small alternative
wastewater systems management districts, including public
hearings to discuss district formation. The "mechanics" of
establishing the districts such as legal and other costs for
drafting of ordinances and regulations, elections, etc., are
a normal function of government and are not grant eligible,
(Construction Grants Program Handbook of Procedures, VII-6).
(d) Rehabilitation, repair or replacement of small alternative
wastewater systems as provided for by 40 CFR 35.908(c).
3. Grant Funding of Small Alternative Wastewater Systems
Small alternative wastewater systems are eligible for 85 percent
grants; 75 percent of the Federal grant may be funded from the
4 percent set-aside. The 10 percent grant increase must be funded
from the 2 percent set-aside (3 percent in FY 1981). The 10 percent
grant increase can also be applied to small alternative wastewater
systems where 4 percent set-aside funds are not available (i.e.,
in States where there is no 4 percent set aside or States where
4 percent set-aside funds have been depleted).
4. Use of Prefabricated or Preconstructed Treatment Components
The use of prefabricated or preconstructed treatment components
such as septic tanks, grinder pump/tank units, etc., normally is
more economical than construction in place and should be carefully
considered. In the case of very small systems, prefabricated or
preconstructed units should in most instances be the most cost-
effective. Por somewhat larger systems of standard design,
prefabricated or preconstructed units may also be cost-effective and
should be carefully considered in the facility plan.
5. Useful Life of Small Alternative Hastewater Systems
Whenever conditions permit, these alternative treatment works
including soil absorption systems, shall be designed to ensure a
minimum useful life of twenty years.
6. Comparison of Small Alternative Wastewater Systems with
Collection Systems jn Cost-Effective Analysis
The present worth of small alternative wastewater systems for
future development permitted by the cost-effectiveness guidelines,
(40 CFR 35, Appendix A) may be compared with the costs of alternative
and conventional collection systems for the same planning area. In
each instance both eligible and ineligible costs shall be considered
including service line costs from residence to collector, connection
fees and service to the on-site units.
B-34
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IV. Determination of the Economic Impact of the Project
When total user charges for wastewater treatment services, including
debt service and operation and maintenance, for the average user in the
service area, exceed the following percentages of annual household
median incomes:
•-- 1.50 percent when the median income is under $6,000;
2.00 percent when the median income is between $6,000-$10,000;
2.50 percent when the median income is over $10,000.
the projects shall be considered expensive and shall receive further intensive
review to determine, at a minimum:
1. the adequacy and accuracy of the cost-effective analysis,
particularly noting whether all the feasible alternatives
have been considered and if the cost estimates are reasonable;
2. the soundness of financing of the local share, and
3. whether the grant applicant has sought out all the sources of
supplemental funding.
(Costs of an expensive project can sometimes be reduced by additional facility
planning effort, including reduction in scope.)
A format, instructions and criteria for determination of the financial
capability of the public body to carry the debt load of a new project are being
prepared and will be promulgated at an early date. This process will be
tailored for the use of municipal authorities and State and EPA reviewing
officials.
V. Interagency Coordination and Streamlining the Review and Approval of Grants
or Loans for Construction of Wastewater Treatment Works in Sparsely Populated
Communities
A. Coordination with Farmers Home Administration (FmHA)
Communities should be encouraged to contact FmHA during the development
of their facility plans to receive informal comments before the plans are
finalized and submitted for review.
Upon receipt of State certified facility plans for communities under
10,000 population, the Region shall send a copy of each plan to State
FmHA officials for their review concurrently with regional review. FmHA
will provide comments normally within 30 days to the Region on the
financial capability of the community to carry the project, the structuring
of the local share debt, the viability of the selected alternative and
other matters in which FmHA is interested. The comments are for each
Regional Administrator's information and appropriate action, if received
within the 30-day period. They are not FmHA's official comments to the
community on its plan. Close cooperation between FmHA and regional
reviewers is encouraged-. For States which are delegated final facility
plan review, the above coordination shall be between the State and State
FmHA officials.
B-35
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B. Exchange of Information Among FmHA, HUD, EDA, CSA and EPA Through
Joint Meetings
The agencies shall meet periodically during the year using the Federal
Regional Councils. Meetings shall be initiated by any of these organizations
and one of,.these meetings will take place at least 120 days before the
beginning'of each new fiscal year. These meetings may include:
1. Review of status of projects being jointly or concurrently
funded;
2. Discussion of future projects in common;
3. Exchange of information on current and new administrative
or substantive procedures or requirements; and
4. Review of action items such as:
a. One year priority or project lists to identify
combined funding possibilities;
b. Existing project lists to identify overlapping
projects or funding; and
c. Construction and inspection schedules to identify
areas of coordination.
Regular meetings between respective state-level agencies
are encouraged for similar purposes of coordination.
C. Encouragement of Alternatives to Conventional Collection and
Treatment of Wastewater
Alternatives to conventional wastewater collection and treatment
facilities that may have lower per capita capital, operating and main-
tenance costs and require less sophisticated technology and skill to
operate shall be encouraged.
D. Provision of Funding and Other Assistance Information to Small Communities
Regional offices and other sources will provide, on request, information
on the range of funding and other assistance for rural sewer projects.
Technical information may be obtained from the Environmental Research
Information Center (ERIC), Cincinnati, Ohio 45268, telephone number
(513) 684-7394, or the Small Wastewater Flows Clearinghouse, West
Virginia University, Morgantown, West Virginia 26506, telephone number
(800) 624-8301.
B-36
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E. Establishment of a Universal Data Base for National Wastewater Disposal
and Treatment Needs
The EPA biennial Needs Survey will be used as the initial data base for
all agencies involved in funding rural facilities.
F. More-Efficient Use of the A-95 Process of Review
Notification of intent to apply for grant funds submitted to A-95
clearinghouses should indicate the intention to apply for joint or combined
funding and identify the prospective assisting agencies.
The A-95 agency needs to conduct only one review of the actual project
for each plan of study and Step 1 grant (except for special circumstances)
which will meet the requirements for all agencies involved.
The use of the A-95 process and Water Quality Management Planning
process under section 208 to identify projects that may be eligible for
funding should be promoted.
Regions should encourage the clearinghouses to use the A-95 process
to evaluate the rural and urban impact of jointly funded projects.
G. Acceptance of One-Time Demonstration or Assurance of Compliance with
Federal Requirements for Jointly Funded Projects
The Regions and States where responsibility has been delegated should
accept evidence of compliance with requirements of the following when they
apply in an identical manner to the programs of each agency:
1. Uniform Relocation and Real Property Acquisition Policies
Act of 1970;
2. Civil Rights Act of 1964; Civil Rights Act of 1968;
Executive Order No. 11246;
3. Davis-Bacon Fair Labor Standards Act;
4. The Contract Work Hours Standards Act;
5. The Copeland (Anti-Kickback) Act;
6. The Hatch Act;
7. The Coastal Zone Management Act of 1972;
8. The Archaeological and Historic Preservation Act of 1974;
9. The National Flood Insurance Act of 1968, as amended by the
Flood Disaster Protection Act of 1973, and regulations and
guidelines issued thereunder;
B-37
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10. The Wild and Scenic Rivers Act of 1968;
11. The Endangered Species Act of 1973;
12.. The Clean Air Act;
13. Executive Order No. 11988 on floodplains management;
14. Executive Order No. 11990 on wetlands protection;
15. The National Historic Preservation Act of 1966, and
Executive Order No. 11593;
16. The Safe Drinking Water Act of 1974.
Further guidance in this area will be issued after detailed review
and discussion by all agencies of regulations and requirements imple-
menting each of the above statutes.
VI. Implementation
This policy should be emphasized through Step 1 preapplication conferences,
contacts through municipalities and'the States and reviews of Steps-! and.2
grant applications. This PRM is effective for facility plans started after
May 31, 1979, except as follows:
a. The determination of economic impact is applicable to facility
plans review commencing 90 days after issuance of this guidance.
b. Review of facility plans by FmHA should commence on facility
plans received for review 60 days after issuance of this guidance.
c. Joint meetings to exchange information using the Federal Regional
Councils should commence prior to May 31, 1979. At least one of the
future meetings should take place at least 120 days before the
beginning of each new fiscal year that follows.
d. The more efficient use of the A-95 review above shall commence
as soon as practicable, but not later than May 31, 1979.
B-38
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APPENDIX C
COST INDEXING
C.I General
Cost data for construction and operation and maintenance (O&M) have origi-
nated from a variety of reference sources and reflect differing time periods
and geographic locations. Values presented in this manual have been con-
verted to a September, 1976 (constant dollar) base except where noted.
C.2 Indexes
Among the indexes commonly used are the EPA Sewage Treatment Plant Construc-
tion Cost Indexes and the EPA Operation and Maintenance Cost Index. The
Construction Cost Index for a 1 mgd trickling filter plant (originally
designated the PHS-STP index and later designated as the WPC-STP index for
treatment plant construction costs) was developed through an analysis of
733 contract awards during the period 1956 through 1962. The econometric
model for a hypothetical 1 mgd trickling filter plant is based on grouping
of input costs and weighted averages of detailed labor and material costs
from each of 20 cities' commercial marketing areas throughout the country.
For construction materials and equipment, area prices for common brick,
concrete, crushed stone, sand, foundry pig iron, structural steel, cast
iron, reinforcing bars, and exterior plyforms are incorporated by weightings
developed for construction conditions of 1957-1962. The input to labor for
construction includes wage rates for electrical workers, hoisting engineers,
structural workers, bricklayers, carpenters, and common labor. Table C-l
shows the EPA Sewage Treatment Plant Construction Cost Index for a 1 mgd
plant for the period 1957 through September, 1979.
The EPA Municipal Wastewater Treatment Plant Operation and Maintenance (O&M)
Cost Index was developed to overcome the shortcomings of applying a single
Wholesale Price Index (WPI) to escalate operation and maintenance costs.
The O&M Cost Index was developed through regression analyses of actual 1967
O&M cost data for a composite 5 mgd conventional activated sludge plant.
The average index is comprised of six sub-indexes which are averaged to form
the single O&M Index. The six sub-indexes are Labor, Chemicals, Power,
Maintenance, Other Costs, and a "quality-added factor" called Added Input.
Each of these categories is escalated individually on a quarterly basis
(annually before 1974) by using commodity group indexes, productivity data
indexes, chemical prices, and a specialized maintenance index. Table C-2
gives the parameters that represent each cost category, the weight of each
parameter within the category, and the source of the escalating factors.
Table C-3 summarizes the average O&M Index and the sub-indexes for the
years 1967 through the third quarter of 1979. A breakdown of the Chemical
Cost sub-index into component chemicals is shown in Table C-4, and details of
the Other Costs sub-index are shown in Table C-5.
C-l
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In addition to adjusting to a constant dollar base, cost indexes, such as
those previously described, are used to perform economic analyses, adjust to
current dollars, and make cost comparisons. However, such indexes, when ap-
plied to the several components of construction or operation and maintenance
costs, will only adjust the data on a national average basis.
In order to arrive at a more accurate cost figure than one which results
from the use of the national average indexes alone, Locality Factors can be
applied to an estimated cost or cost index. The use of Locality Factors,
which have been calculated from generally available statistics, permit the
localizing of national average cost data for construction labor, construction
materials, total construction cost, operation and maintenance labor costs,
and power costs. The factors for labor and materials are given in Table C-6
and those for power costs are given in Table C-7.
In order to obtain current cost and price indexes, contact Robert L. Michel,
Priority Needs and Assessment Branch (WH-595), Office of Program Operations,
U.S. Environmental Protection Agency, Washington, D.C. 20460 (202) 426-4443.
C-2
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TABLE C-l
EPA SEWAGE TREATMENT PLANT CONSTRUCTION COST INDEX
U.S. CITY AVERAGE (1957-1959 = 100) (1)(2)
Year Jan. Feb. March April May June July Aug. Sept. Oct. Nov. Dec.
1957
1958
1959
1960
1961
1962
1963
1964
1965
1966
1967
o 1968
c!o 1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
106.8
109.6
110.8
114.1
117.8
121.1
128.7
137.6
150.6
167.7
176.1
188.1
107.1
109.5
111.0
114.6
118.1
121.2
129.5
137.9
150.9
168.7
177.5
190.2
107.1
109.5
111.1
114.8
118.1
121.2
129.8
138.2
153.3
169.2
180.7
191.0
247.4
256.7
270.9
290.1
322.0
107.1
109.6
111.1
115.1
118.2
121.6
130.0
138.5
155.4
169.9
181.6
196.1
107.2
109.7
111.2
115.3
118.3
121.7
130.0
141.2
157.3
171.4
182.6
197.8
107.8
110.0
111.8
116.1
119.1
122.5
131.1
143.0
158.6
172.2
182.9
208.9
245.9
259.6
273.8
303.1
334.1
108.1
110.2
112.3
116.8
119.6
123.4
132.4
146.3
160.6
172.3
183.7
108.5
110.5
112.6
116.9
120.3
123.7
135.3
146.7
165.1
173.1
183.9
107.2
108.6
110.6
112.7
117.1
120.6
124.5
135.5
147.5
166.3
173.8-
184.5
230.1
251.3
262.5
281.0
311.0
337.8
107.2
109.5
110.7
112.8
117.5
120.9
126.8
135.9
148.1
166.3
174.5
185.0
107.0
109.5
110.7
112.9
117.5
120.9
127.2
136.6
149.3
166.4
175.5
185.8
106.8
109.6
110.7
113.1
117.5
121.0
127.7
136.9
149.6
167.2
175.7
187.5
238.8
255.4
270.3
287.6
314.1
98.0
101.5
103.7
105.0
105.9
107.0
108.5
110.1
112.0
116.1
119.4
123.6
132.7
143.6
159.8
172.0
182.6
217.2
250.0
262.2
278.3
304.6
(1) Based on 1.0 MGD high rate trickling filter with aeration.
(2) Note: The input to the two indexes include wage rates (for each of 20 cities) for electrical
workers, hoisting engineers, structural workers, bricklayers, carpenters, and common labor. For
materials and equipment, area prices for common brick, concrete, crushed stone, sand, foundry pig
iron, structural steel, cast iron, reinforcing bars, and exterior plyform are incorporated by
weightings developed for construction conditions of 1957-1962.
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TABLE C-2
PARAMETERS USED TO ESCALATE O&M COST CATEGORIES (1)
o
CATEGORY
Salaries and Wages
Electricity
Chemicals
Maintenance
PARAMETER
Average Hourly Earnings
Water, Steam and Sanitary
Systems
Industrial Power, 500 Kw
Demand, Price Index
Chlorine Liquid
L1me
Methanol
Ferric Chloride
Chemical Freight
Alum
Factory Maintenance
Transformers and
Power Regulators Index
Valves & Fjttlngs
Pumps, Compressors and
Equipment
Centrifugal Blowers
t
Gasoline
Unit Non-Labor Payments
* WEIGHT I/
100
100
70
10
5
5
5
5 '
60
10
10
10
10
7(\
30
SERIES
SIC 4947
PPI 0543
PPI 0613 0101
PPI 0613 0213
$/gal FOB Gulf Coas
$/100 Ib. Sewage Gr
Code 28 - Railroad
$/Bulk Ton
1968 Base Year
PPI 1174
PPI 114901
PPI 1141
PPI 11470101
PPI 0571
SOURCE
y
U
3/
! 1
Freight 3/
4/
I
$
3/
7/
1
5/
J7 Percent of Base Year (1967) Category Cost
2/ Employment and Earnings, BLS DOL
3/ Producer Price Indexes, BLS DOL
4/ Chemical Marketing Reporter
5/ Factory Vol. 8, No. 11, November 1975
6/ Monthly Labor Review, May 1976
TJ EPA Sewage Treatment Plant Cost Index
with MD Rate Adjustments
(1) Reference: Development of a Cost Index for Operation- and Maintenance of Municipal Wastewater Treatment Plants,
Robert L. Michel, July 1976.
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TABLE C-3
EPA MUNICIPAL WASTEWATER TREATMENT OPERATION
AND MAINTENANCE COST INDEX (1)(2)(3)
Year
1967
1968
1969
1970
1971
1972
1973
1974
1974
1974
1974
1975
1975
1975
1975
1976
1976
1976
1976
1977
1977
1977
1977
1978
1978
1978
1978
1979
1979
1979
Qtr
A
A
A
A
A
A
A
1
2
3
4
1
2
3
4
1
2
3
4
1
2
3
4
1
2
3
4
1
2
3
Labor
Index
1.00
1.06
1.14
1.24
1.32
1.41
1.48
1.54
1.57
1.63
1.67
1.70
1.72
1.76
1.79
1.84
1.86
1.91
1.96
1.96
1.97
2.04
2.09
2.13
2.15
2.24
2.24
2.29
2.35
2.37
Chemical
Cost
Index
1.00
1.03
1.08
1.10
1.12
1.13
1.18
1.34
1.54
1.83
2.05
2.37
2.39
2.39
2.39
2.50
2.49
2.55
2.58
2.54
2.56
2.58
2.54
2.54
2.52
2.51
2.58
2.57
2.63
2.75
Power
Index
1.000
1.009
1.022
1.066
1.155
1.239
1.326
1.543
1.741
1.852
1.951
2.080
2.060
2.137
2.152
2.207
2.255
2.341
2.327
2.486
2.562
2.662
2.627
2.797
2.869
2.800
2.830
2.921
3.024
3.144
Main-
tenance
Index
1.000
1.037
1.081
1.133
1.189
1.218
1.321
1.408
1.550
1.660
1.718
1.746
1.767
1.790
1.812
1.835
1.865
1.896
1.919
1.953
1.986
2.041
2.071
2.112
2.182
2.229
2.289
2.334
2.411
2.478
Other
Cost
Index
1.00
1.01
1.03
1.06
1.14
1.19
1.27
1.46
1.60
1.68
1.67
1.73
1.80
1.92
1.93
1.92
1.96
2.03
2.05
2.08
2.13
2.16
2.19
2.19
2.25
2.35
2.41
2.50
2.66
2.91
Added
Input
Index
1.00
1.04
1.11
1.21
1.31
1.40
1.52
1.68
1.80
1.92
1.99
2.08
2.11
2.17
2.19
2.29
2.32
2.39
2.43
2.47
2.53
2.63
2.65
2.73
2.82
2.88
2.91
2.98
3.10
3.23
Average
O&M
Index
1.00
1.03
1.09
1.16
1.23
1.30
1.38
1.50
1.60
1.69
1.76
1.83
1.85
1.90
1.93
1.97
2.00
2.06
2.09
2.12
2.15
2.22
2.24
2.30
2.33
2.38
2.40
2.46
2.54
2.62
1) 1967 = 1.000
2) Based on 5 MGD conventional activated sludge
(3) Reference: EPA Operations and Maintenance Cost Index,
September 1979, Robert L. Michel, EPA, Washington, D.C.
C-5
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TABLE C-4
EPA MUNICIPAL WASTEWATER TREATMENT PLANT
OPERATION AND MAINTENANCE COST INDEX
CHEMICAL COST COMPONENT (1)(2)(3)
Yr
67
68
69
70
71
72
73
74
74
74
74
75
75
75
75
76
76
76
76
77
77
77
77
78
78
78
78
79
79
79
Q
T
R
A
A
A
A
A
A
A
1
2
3
4
1
2
3
4
1
2
3
4
1
2
3
4
1
2
3
4
1
2
3
Chlorine
Index
1.000
1.037
1.089
1.111
1.111
1.111
1.111
1.201
1.338
1.645
1.843
2.228
2.265
2.256
2.241
2.347
2.316
2.328
2.370
2.382
2.338
2.334
2.258
2.220
2.201
2.173
2.256
2.214
2.195
2.245
Alum
Index
1.00
1.08
1.08
1.16
1.16
1.26
1.26
1.26
1.60
1.60
1.60
1.98
1.98
2.22
2.22
2.22
2.22
2.42
2.42
2.42
2.59
2.59
E.59
2.75
2.75
2.75
2.75
2.93
2.93
2.95
Ferric
Chloride
Index
1.00
1.00
1.00
1.00
1.14
1.14
1.14
1.28
1.28
1.28
1.42
1.42
1.42
1.42
1.42
1.42
1.42
1.42
1.42
1.42
1.42
1.42
1.57
1.57
1.57
1.57
1.57
1.67
1.69
1.69
Methanol
Index
1.00
1.00
1.11
1.11
1.11
1.11
1.55
2.22
3.00
3.55
4.33
4.33
4.33
4.22
4.22
4.44
4.44
4.77
4.77
4.22
4.66
4.88
4.88
4.88
4.88
4.88
4.88
4.88
5.55
6.22
Lime
Index
1.000
1.000
1.013
1.045
1.113
1.137
1.174
1.482
1.483
1.619
1.705
1.964
1.919
1.932
1.963
2.133
2.207
2.249
2.273
2.313
2.311
2.317
2.371
2.531
2.550
2.604
2.629
2.711
2.762
2.847
R.R. Index
Chemical
Freight
1.000
1.031
1.061
1.146
1.292
1.324
1.350
1.501
1.519
1.656
1.663
1.663
1.763
1.857
1.905
1.907
1.949
1.950
2.003
2.083
2.083
2.085
2.181
2.170
2.163
2.237
2.394
2.397
2.430
2.518
Overall
Chemical
Index
1.00
1.03
1.08
1.10
1.12
1.13
1.18
1.34
1.54
1.83
2.05
2.37
2.39
2.39
2.39
2.50
2.49
2.55
2.58
2.54
2.56
2.58
2.54
2.54
2.52
2.51
2.58
2.57
2.63
2.75
(1) 1967 = 1.000
(2) Chlorine estimated at 70% of 1967 plant chemical cost.
Lime 10%, others 5% each.
(3) Reference: EPA Operation and Maintenance Cost Index, September 1979,
Robert L. Michel, EPA, Washington, D.C.
C-6
-------
TABLE C-5
EPA MUNICIPAL WASTEWATER TREATMENT PLANT
OPERATION AND MAINTENANCE COST INDEX
OTHER COST COMPONENTS (1)(2)(3)
Year
Quarter
1967
1968
1969
1970
1971
1972
1973
1974
1974
1974
1974
1975
1975
1975
1975
1976
1976
1976
1976
1977
1977
1977
1977
1978
1978
1978
1978
1979
1979
1979
A
A
A
A
A
A
A
1
2
3
4
1
2
3
4
1
2
3
4
1
2
3
4
1
2
3
4
1
2
3
Insurance
Index
1.000
.035
.111
1.202
1.338
1.440
1.529
1.599
1.749
1.927
000
072
059
104
139
151
174
198
263
268
293
353
,408
,429
,538
.604
.630
.696
.798
2.
2,
2,
2.
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
Administration
Index
1.000
1.032
1.040
1.069
1.148
1.190
1.208
1.229
1.269
1.303
1.336
1.384
1.'427
1.493
1.520
1.550
1.573
1.590
1.629
1.668
1.658
1.697
1.750
769
775
1.857
2.829
1.907
1.957
1.920
1.943
Fuel
Index
1.000
.959
.978
.961
1.013
1.040
1.220
1.775
2.059
2.158
2.032
2.094
2.258
2.541
2.499
2.413
2.487
2.658
2.631
2.674
2.821
2.828
2.795
2.759
2.854
3.011
3.103
3.290
3.817
Overall
Other
Index
1.00
1.01
1.03
1.06
1.14
1.19
1.27
1.46
1.60
1.68
1.67
1.73
1.80
1.92
1.93
1.92
1.96
2.03
2.05
2.08
2.13
2.16
2.19
2.19
2.25
2.35
2.41
2.50
2.66
4.598
2.91
(1) 1967 = 1.000
(2) Insurance Index combines rate changes and property valuation increases,
(3) Reference: EPA Operation and Maintenance Cost Index, September 1979;
Robert L. Michel; EPA, Washington, D.C.
C-7
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TABLE C-6
COST LOCALITY FACTORS
Atlanta
Baltimore
Birmingham
Boston
Chicago
Cincinnati
Cleveland
Dallas
Denver
Detroit
Kansas City
Los Angeles
Minneapolis
New Orleans
New York
Philadelphia
Pittsburgh
St. Louis
San Francisco
Seattle
NATIONAL INDEX VALUES
Labor
0.66
0.90
0.66
1.12
1.25
1.10
1.19
0.63
0.76
1.17
0.97
1.17
0.93
0.88
1.43
1.23
1.05
1.29
1.23
1.16
1.00
Construction ( | )
Materials
1.03
0.95
1.02
0.90
1.10
1.05
1.01
0.83
1.07
0.98
1.25
1.16
1.03
1.05
0.91
1.00
0.96
0.99
0.96
0.91
1.00
Total
0.79
0.92
0.79
1.04
1.20
1.08
1.13
0.70
0.87
1.10
1.07
1.17
0.97
0.94
1.24
1.15
1.02
1.18
1.13
1.07
1.00
O&M (2)
Labor
0.77
0.79
0.79
0.97
1.02
0.98
1.05
0.92
1.00
1.32
0.88
1.32
1.21
0.66
1.14
1.05
0.87
0.83
1.13
1.21
1.00
(1) Calculated from EPA Sewage Treatment Plant and Sewer Construction Cost
Index Third Quarter 1979.
(2) Reference: U.S. Department of Commerce Bureau of Census, City
Employment in 1976, GE76 No. 2 July 1977. Based on average earnings
by city of non-education employees.
C-8
-------
TABLE C-7
POWER COST LOCALITY FACTOR (1)(2)
New England 1.31
Mid-Atlantic 1.18
East North Central 1.10
West North Central 0.98
South Atlantic 0.94
East South Central 0.98
West South Central 0.87
Mountain 0.79
Pacific 0.86
U.S. Average 1.00
(1) Basis: BLS, September, 1979
Producers Price Index
(2) Source: "Construction Cost
Indexes," EPA, Municipal
Construction Division;
R.L. Michel; September, 1979
C-9
-------
APPENDIX D - LIST OF TABLES
No. Page
D-l Energy Requirements and Transfer Efficiency of Selected D-15
Aeration Devices
D-2 Design Criteria for Vacuum Filtration D-16
D-3 Design Criteria for Filter Pressing D-17
D-4 Energy Conversion and Representative Heat Values D-18
D-5 Conversion Factors D-19
D-6 Present Worth Factors D-20
APPENDIX D - LIST OF FIGURES
D-l Hydraulic Efficiency of Centrifugal Pumps D-29
D-2 Power Requirements for Raw Sewage Pumping D-30
D-3 Anaerobic Digester Heating Requirements D-31
D-4 Anaerobic Digester Heat Loss D-32
D-5 Anaerobic Digester Heat Production D-33
D-6 High Rate Anaerobic Digester Mixing Requirements D-34
D-7 Sludge Pumping Energy for Heat Exchange D-35
D-7(a) Anaerobic Digester Heat Requirements for Primary Sludge D-36
D-7(b) Anaerobic Digester Heat Requirements for Primary Plus D-37
Waste Activated Sludge
D-8 Fraction of Solids VS Water Content D-38
D-9 Flue Gas Temperature Attainable at Different Water Content D-39
D-10 Supplemental Fuel Requirement at 50% Excess Air D-40
D-ll Supplemental Fuel Requirement at 100% Excess Air D-41
D-12 Excess Air Requirement D-42
D-13 Heat Recovery from Waste Heat Boiler D-43
D-14 Energy Requirements for Vacuum Filtration D-44
D-15 Energy Requirements for Filter Pressing D-45
D-16 Energy Requirements for Centrifuging D-46
D-i
-------
APPENDIX D
ENERGY UTILIZATION CURVES AND CONVERSION FACTORS
D.I General
The information in this appendix supplements the energy utilization data
presented in Appendix A for the individual municipal treatment unit pro-
cesses. Emphasis here is placed on the presentation of energy utilization
curves for the more energy intensive municipal treatment processes of
pumping and aeration along with the specifically identified alternative
technology processes of anaerobic digestion, incineration, and dewatering.
Also included are commonly used energy conversion tables, conversion fac-
tors, and a table of fuel and energy equivalents.
D.2 Energy Intensive Processes
In conventional municipal wastewater treatment plants, about 60% of the
electrical energy is consumed in aeration, and about 20% in pumping. Thus,
about 80% of the total electrical energy consumption is associated with
these two processes which offer the greatest potential for electrical
energy conservation. The major energy requirement for many land treatment
systems is also for aeration (prior to application to the land) and pumping
(when applying the effluent to the land for treatment). For this reason,
the following principles can be readily applied to those systems.
D.2.1 Aeration
The two basic methods of aeration of suspended growth systems are mechanical
aeration and air bubble diffusion. Turbine spargers which are a combination
of the above two devices have also been used.
The oxygen transfer effiencies and energy requirements of selected aeration
devices are shown in Table D-l. Aeration systems are rated in terms of their
aeration efficiencies as pounds of 0? per horsepower-hour (hp-hr) at
standard conditions. Standard conditions exist when the temperature is
20°C, pressure is 760mm Hg, the D.O. is 0.0 mg/1 and the test liquid is
clean water. These ideal efficiencies and transfer rates vary from those
found for wastewater under field conditions. Efficiency claims should be
accepted only when supported by actual test data for the actual model and
size of aerator under consideration; and for design purposes, the standard
performance data must be adjusted to reflect anticipated field conditions.
This is accomplished by converting Ib 02/hp-hr transferred under standard
conditions to Ib 02/hp-hr transferred under field conditions. This can be
done by using the following formula:
D-l
-------
N = N [ ./C*walt - CL)e
-------
Elevation (Feet) Correction Factor, F
Sea Level 1.00
2,000 0.93
4,000 0.87
6,000 0.80
8,000 0.73
Since aeration devices may operate under submerged conditions, and exposure
to more than atmospheric pressure at the point of oxygen transfer, a further
adjustment to C*wait may be needed. Also, if a value of C*st is given at a
condition of atmospheric pressure, adjustment to this value may also be needed.
These further adjustments are beyond the scope of this manual, but can be ob-
tained from the equipment manufacturer. As an example, at a ten-foot depth,
these saturation values may increase as much as 9% according to one manufac-
turer.
The value for a can vary widely according to wastewater characteristics, type
of equipment, geometry of the basin, etc. In fact, the outside range for a
is reported to be from 0.3 to 1.2 whereas a more normal range for a is re-
ported from 0.5 to 1.0. Since a is part of the numerator, this means that
resultant field 02 transfer efficiencies can be affected as much as two times
(normal range) to four times (outside range). Therefore, it is critical that
the value for a is selected carefully. The following example is provided to
demonstrate use of the conversion equation.
Standard test conditions are 20°C, 760mm Hg, 0.0 mg/1 D.O. and the Nr, is
given as 3.0 Ib 02/hp-hr for a surface aerator, a is 0.75, 3 is 0.9. The
field conditions are to be a 30°C average temperature at 2,000 feet elevation
and design D.O. concentration is 2.0 mg/1.
c*walt = 9.17 x 0.93 = 8.53 (no change for depth required)
C*st = 9.17
CL = 2.0 mg/1
Tc = 30°C
By applying the aforementioned equation., the conversion factor becomes 0.59,
and the efficiency of the aerator under field conditions (N) becomes
0.59 x 3.0 = 1.77 or 1.8 Ib 02/hp-hr.
This conversion to actual operating conditions can significantly affect energy
usage in a system. Therefore, it is important to realize that comparison of
two kinds of aeration devices can be made under standard conditions but when
calculating actual energy use, actual anticipated field conditions must be
used.
The oxygen transfer efficiencies and energy requirements of selected aeration
devices are shown in Table D-l. The values given are for standard con-
ditions rather than field conditions. In the fact sheets (Appendix A)
values for efficiencies for aeration devices in terms of Ib 02/hp-hr are
given which do reflect anticipated field conditions. The energy and power
D-3
-------
cost curves in the fact sheets are based on these field values;and if
another value is to be used,the curves would have to be modified accordingly
by the user.
Example Calculations:
A 1.0 mgd wastewater flow with a BOD of 200 mg/1 is to be
treated in an aeration basin equipped with low speed mechanical
aerators. Calculate the electrical energy required.
Assume 1.0 Ib 02/lb BOD required
1,000,000 Sil x 200 M x
Ib
___
1,000,000 mg
day
= 1,668 Ib 02/day
x 0.26 KwH s 433.68 KwH/day
D.2.2 Pumping
Pumping devices commonly used in municipal wastewater application include
centrifugal, axial-flow, mixed flow, reciprocating, air lift pumps, and
pneumatic ejectors. The radial, or so-called "non-clog" centrifugal pumps
with specially designed impellers are widely used in raw wastewater pumping.
The axial-flow pumps, such as screw pumps, are applicable to well settled
sewage only, and are used for recirculation or effluent pumping. The mixed-
flow pumps which are intermediate between centrifugal and axial-flow pumps
are suitable for moderate head pumping. Reciprocating pumps such as dia-
phragm pumps have their greatest use in pumping sludges. Air lift pumps
are generally used in smaller treatment plants and are also useful as
sludge pumps. Pneumatic ejectors are suitable for pumping wastewater of
small flows from an isolated area to a main sewer line or treatment facility.
Since centrifugal pumps are the most widely used pumping equipment, their
hydraulic efficiencies and electrical energy requirements are shown in
Figures D-l and D-2, respectively. Calculations of energy requirements are
illustrated in the following example.
Example Calculations:
A 1 mgd flow is to be pumped against a total dynamic head of 30 ft.
The pump motor is 95% efficient and the efficiency of the pump is
75%. Calculate the electrical energy required.
1 mgd6 x 106 x 8.34 Ib/gal
1440 min/day x 60 sec/min
on ... 00_c ,. 1k/
x 30 ft' = 28% ft 1b/sec
2896ft Ib/sec x
= 5.27 HP
D-4
-------
5.27 x 0.7457 x 24 hours/day _ ,„ .
- 0.95 x o.75 - - I3<£'
If the wire to water efficiency is not given, it can be estimated from
Figure D-l. For the above example, the overall efficiency given in the
figure is approximately 63%. Using this estimate, the required power in
the above example is:
5'27 x °;™57 x 24 = 149.7 KwH/day
Estimates of the annual power requirements for raw sewage pumping against
different values of the total dynamic head are provided in Figure D-2.
D.3 Alternative Sludge Handling Processes
The specifically identified energy recovery technology in the Innovative and
Alternative Guidelines includes co-disposal of sludge and refuse, anaerobic
digestion with more than 90% methane recovery, and self-sustaining inciner-
ation. The energy utilization for anaerobic digestion and incineration is
presented in the following discussion.
D.3.1 Anaerobic Digestion
Heat energy is required to raise the temperature of the influent sludge
solids and associated water and to compensate for heat losses through the
digester walls, bottom, and cover. Electrical energy is required for mixed
digesters to operate the mixing equipment and to pump the digester contents
through the heat exchangers. The digester gas can be collected and burned
to provide needed energy. The influent heat requirement per ton of sus-
pended solids fed to the digester can be determined from Figure D-3. The
temperature difference is that between the influent sludge stream and the
digester operating temperature. Heat losses per ton of solids fed to the
digester are shown in Figure D-4 for varying reactor detention times and
solids feed concentrations. Figure D-5 shows the heating value of the
digester gas per ton of solids fed to the digester as a function of volatile
solids destruction for different volatile solids percentages in the feed
sludge. The following example illustrates the use of Figures D-3 thru
D-5 to calculate heat balances around a digester.
Example Calculations:
Example No. 1
A sludge stream at 3% solids which are 70% volatile is fed to
an anaerobic digester in the northern U.S. The digester detention
time is 20 days and the volatile solids destruction is 60%. The
digester operates at 95°F and the average annual influent sludge
temperature is 55°F. The heating equipment has an efficiency of
75%.
D-5
-------
From Figure D-3 2.67 x 106 BTU/ton required for 3% solids
and A Temp of 40°F.
Correct for heating equipment efficiency:
2.67 x 106/0.75 = 3.56 x 106 BTU/ton input
to heater needed.
From Figure D-4 1.33 x 106 BTU/ton required.
Correct for heating equipment efficiency:
1.33 x 106/0.75 = 1.77 x 106 BTU/ton input
to heater needed.
From Figure D-5 7.55 x 106 BTU/ton generated.
Overall Net Heat Generation Potential:
7.55 x 106 - 3.56 x 106 - 1.77 x 106 = 2.22 x 106 BTU/ton solids fed.
Example No. 2
A sludge stream at 5% solids which are 75% volatile is fed to an
anaerobic digester in the southern U.S. The digester detention
time is 15 days and the volatile solids destruction is 50%. The
digester operates at 95°F and the influent sludge feed averages
70°F. The heating equipment has an efficiency of 75%.
From Figure D-3 1.0 x 106 BTU/ton required for 5% solids and
A Temp of 25°F.
Correct for heating equipment efficiency:
1.0 x 106/0.75 = 1.33 x 106 BTU/ton input to
heater needed.
From Figure D-4 0.6 x 106 BTU/ton required in northern U.S.
0.6 x 106 x 0.3 = 0.18 x 106 needed for southern U.S.
Correct for heating equipment efficiency:
0.18 x 106/0.75 = 0.24 x 106 BTU/ton input to
heater needed.
From Figure D-5 6.75 x 106 BTU/ton generated.
Overall Net Heat Generation Potential:
6.75 x 106 - 1.33 x 106 - 0.24 x 106 = 5.18 x 106 BTU/ton solids fed.
Electrical Energy
The electrical energy requirement in KwH/yr to mix the digester(s) can be
D-6
-------
estimated from Figure D-6. The required digester total volume in ft3 is
given by the following equation as:
Sludge Flow, gpd x Digester Detention Time, days
7.48 gal/ft3
The electrical energy required in KwH/yr to pump the sludge through the heat
exchangers can be estimated by finding the sum of the heating requirement
from Figures D-3 and D-4 in million of BTU's per dry ton of solids and
multiplying this value by the tons per day of solids fed to the digester.
This computed value in million BTU/day can be used in Figure D-7 to estimate
the electrical energy requirements for pumping the sludge through the digester.
The total heat requirements of anaerobic digestion can also be estimated by
using Figures D-7(a) and D-7(b). These heat requirements are based on a
digestion temperature of 95°F. Typical loading in Ib VS/day/cu ft is 0.05
for standard rate, and 0.15 for high rate digestion. Typical detention time
is 30 days for standard rate, and 15 to 20 days for high rate digestion.
The amount of sludge produced in a wastewater treatment plant, and the VS
content of the sludge varies with the influent suspended solids concentration,
the BOD, and type and efficiency of the biological treatment process. The
following sludge quantities are representative of typical primary and
activated sludge plants:
Sludge Solids
(Ib/mil gal)
Sludge Type Total _ Volatile
Primary 1,151 690 (60%)
waste Activated 945 756 (80%)
TOTAL ~Tjm T7W6"
Generally, about 50% of the volatile solids are destroyed by anaerobic
digestion and the gas produced has a heat value of about 600 BTU/scf.
These criteria give the following estimates for gas and heat available
from anaerobic digestion:
Waste
Primary Activated
Sludge Sludge Total
Gas Produced, scf/mil/gal 5,175 5,670 10,845
Heat Available, BTU/mil/gal 3,105,000 3,402,000 6,507,000
For planning purposes, and in the absence of more specific information, it
may be assumed that about 6.5 mil BTU are available from gas produced by
anaerobic digestion of primary and conventional activated sludge treatment
of one million gallons of wastewater.
D.3.2 Incineration
Energy requirements for incineration and the potential for energy recovery
D-7
-------
have been described by Smith (1). When the sludge is 70% volatile, the
minimum solid concentrations needed to operate a self-sustaining incineration
without auxiliary fuel at different flue gas temperatures were calculated to
be 25.9% at 800°F, 30% at 1,000°F, 34.7% at 1,200°F, and 40.4% at 1,400°F.
The attached figures provide a brief summary of some of the design parameters.
Further details are available in the above reference.
Figure D-8: This figure shows the pounds of water (Ws) per Ib of dry volatile
solids (DVS) as a function of the solids content of the sludge (Fs) for dif-
ferent volatile solids fractions. For example, a sludge containing 25%
solids which are 70% volatile, has 4.29 Ib of water per Ib of DVS.
Figure D-9: This figure shows the flue gas temperature (Ts) attained with
50% excess air and 100% excess air for various values of Ws. For example,
if Ws is 3.0, the flue gas temperature will be 1100°F with 50% excess air
and 920°F with 100% excess air. If one desires a flue gas temperature of
1000°F, Ws would have to be less than 3.35 to avoid using supplemental fuel.
Figure D-10: The gallons of fuel oil per ton of DVS (Rf) that must be used
to incinerate sludge with different values of Ws using 50% excess air are
shown in Figure D-10. For example, to achieve a 1000°F flue gas temperature
with Ws = 6, the supplemental fuel requirement is 77.5 gal/ton DVS. This
fuel requirement does not include an estimate for start-up requirements.
Figure D-ll: The gallons of fuel oil per ton of DVS (Rf) that must be used
to incinerate sludge with different values of Ws using 100% excess air are
shown in Figure D-ll.
Figure D-12: When the sludge is sufficiently dry to sustain combustion,
the excess air requirement varies to hold the desired flue gas temperature.
the excess air requirement (Ex) for different values of Ws is shown as a
function of flue gas temperature in Figure D-12.
Figure D-13: The heat that can be recovered across a waste heat boiler
operated with an exit temperature of 500°F is shown for different inlet
gas temperatures and values of Ws in Figure D-13. For a sludge with a
value of Ws of 2.0 and the excess air controlled to provide a flue gas
temperature of 1200°F, the heat recovered across the boiler would be
3920 BTU/lb DVS.
When supplemental fuel is burned in the sludge incineration process, the
total heat that can be recovered from a waste heat boiler is given by:
BTU/lb DVS = (0.505 x Ws + 2.55 + 2.09 x Ex + 0.0152 x Rf) x AT
where AT is the temperature drop across the waste heat boiler. For
Ex = 0.5 or 1.0 the values of Rf are presented in Figures D-10 and
D-ll respectively. This information can be used in conjunction with
Figure D-8 to calculate the recoverable heat.
D-8
-------
For example, consider a sludge with Ws = 6.0 combusted with 50% excess air at
a flue.gas temperature of 1200°F and a waste heat boiler operating with a
boiler exit temperature of 500°F. Here Rf = 116 gal/ton DVS (From Figure D-10)
and the heat recovered is:
(0.505 x 6. + 2.55 + 2.09 x 0.5 + 0.0152 x 116) x (1200 - 500) = 5872 BTU/lb DVS
D.4 Dewatering Processes
As previously mentioned, self-sustaining incineration can be achieved if the
sludge is adequately dewatered. The energy requirements for the three
commonly used sludge dewatering processes, i.e., vacuum filtration, filter
press, and centrifuge, are presented as follows to assist the overall eval-
uations of the energy utilization.
D.4.1 Vacuum Filtration
The electrical energy requirement in KwH/yr to continuously operate a vacuum
filter of various sizes is given in Figure D-14.
Variables which affect the performance of the vacuum filter include feed
sludge type, feed sludge concentration, feed sludge loading, type and amount
of conditioning chemicals, type and operation of filter, etc. Alternative
sludge types, typical loading rates, and the corresponding cake solids are
presented in Table D-2.
Example Calculations
A 100,000 gpd sludge stream at 5%'solids (after addition of conditioning
chemicals) will be fed at 4 Ib/ft2/hr for 16 hrs/day. Solids capture
is 96% and cake solids are 25%.
100,000 Ml x 8.34 1b x 0.05 = 41,700 lb solids fed
day gal day
41,700 Ib/day ,
16 hrs x 4 ID/ft? = 651 ft ^quired
day hr
From Figure D-14:
651 ft2: 490,000 KwH/yr
490,000 x (16/24) _
355 days/yr ' 895
895 KwH/day x2000 Ib/ton .. 7 ....
41,700 x 0.96 = 44'7 KwH
ton DS captured
D-9
-------
Water Remaining in Cake:
41,700 x 0.96 x 1-0 - °-25 = 120,096 To
0.25
D.4.2 Filter Press
The electrical power requirement in KwH/yr to continuously operate a filter
press of various volumes is given in Figure D-15. Typical conditioning
requirements, cycle times and cake solids for various sludge types are pre-
sented in Table D-3.
Example Calculations:
A 100,000 gpd sludge stream at 5% solids (after addition of
conditioning chemicals) will be fed to a filter press with a
two hour cycle time. Solids capture is 96% and cake solids
are 45%. Operation is 16 hrs/day.
100,000 gal/day ,
- ! - a - r-^ = 13,369 ft3/day
7.48 gal/ft3
13,369 ft3/day ,
8 cycles/day = M70 ft-5 required
From Attached Figure (For 835 ft3 Press)
2 x 600,000 = 1,200,000 KwH/yr
100,000 4|1 x 8.34 -lif x 0.05 = 41,700 lb solids fed
day gai
2,192 KwH/day x 2,000 Ib/ton _ 1no , KwH
- 41,700 x 0.96 ' iuy'b ton DS captured
Water Remaining in Cake:
41,700 x 0.96 x 1-00"4°5'45 = 48,928 lb
D.4.3 Centrifuge
The electrical energy requirement in KwH/yr to continuously operate a cen-
trifuge at various flow rates can be estimated from Figure D-16.
Example Calculations:
A 100,000 gpd sludge stream at 5% solids (after addition of
conditioning chemicals) will be fed to a centrifuge for
16 hrs/day. Solids capture is 90% and cake solids are 25%.
D-10
-------
= 104 gpm t0 centrifLJ9e
From Figure D-16:
104 gpm: 220,000 KwH/yr
' «*
100,000 x 8.34 -IS-
day 9al
402 KwH/day x 2,000 Ib/ton
- 41,700 x 0.90 -
Water Remaining in Cake:
41,700 x 0.90 x 1 - °-25
.25
x 0.05
41,700 1b solids fed
day
91/1 _ ^KwH _ ,
^'4 ton DS captured
= 112,590 15
D.5 Energy Conversion Methods
Whenever various forms of energy are interconverted there will be some loss
due to inefficiencies. For example, whenever electrical energy is converted
to mechanical energy, some of the energy is lost as heat energy in the motor.
Similarly, if an engine operating on a Carnot cycle has a source temperature
of 1100°F (1560°R) and a receiver temperature of 500°F (960°R) the efficiency
is only (1.0 - 960/1560) or 38.5%. Since no heat engine can be more efficient
than a Carnot engine, it is clear that this is the maximum possible efficiency
for these source and receiver temperatures.
The efficiency of pumps and blowers is usually in the range of 70-80% so
that mechanical energy can be converted to hydraulic energy with no more
than about 30% loss. Similarly, mechanical and electrical energy can be
converted from one form to the other with a loss of less than 10%. On the
other hand, the conversion of heat energy to mechanical energy necessitates
the wasting of roughly 2/3 of the heat energy. For example, if electrical
energy is converted to heat energy, one KwH will generate about 3,413 BTU
of heat. However, if heat energy is used to generate electrical energy
in a modern coal fired power plant, about 10,500 BTU of heat energy is
needed to generate one KwH; this is a conversion efficiency of only 32.5%.
D.6 Present-Worth Methodology
The purpose of this methodology is to determine the present-worth cost of
an alternative. The costs identified include construction cost, constant
and variable operation and maintenance (O&M) costs, existing facility phase
out costs, facility replacement costs, and facility salvage value. This
procedure converts these costs over the project life into an equivalent cost
D-ll
-------
that represents the current investment that would be required to satisfy all
of the identified project costs for the planning period. For a more detailed
discussion, the user may consult any standard engineering economy text.
The construction costs incurred by the project represent single-payment
costs that occur at certain times throughout the planning period. The
single-payment present-worth factor (sppwf) is used to determine the
present-worth cost, and is determined by the following formula and shown
in the first column of Table D-6:
1
sppwf = (i + i)n
where: i is the interest
n is the number of interest periods
The operation and maintenance (O&M) cost includes both constant and variable
costs. The constant O&M cost is based on the flow rate at the beginning of
the planning period. The variable O&M cost represents the difference between
the O&M cost at the flow rate in the final year of the planning period and
the constant O&M cost identified by the flow rate at the beginning of the
planning period. The uniform-series present-worth factor (uspwf) is used
to convert the constant annual O&M cost to a present-worth cost by the
following formula and shown in the second column of Table D-6.
uspwf = (1 + i)n - *
i (1 + i)n
where: i is the interest rate
n is the number of interest periods
For cases where the constant payment is for a period that does not start at
the beginning of the planning period (Phase 2 constant O&M costs), the
uniform-series factor must be adjusted by multiplying it by the single-
payment present-worth factor for the number of years from the beginning
of the planning period to the time that the constant payment begins, as
in the following:
( uspwf tl) x ( sppwf t2)
where: tl is the number of years that the constant payment will be made
t2 is the number of years from the beginning of the planning
period to the time that the constant payment begins
The variable operation and maintenance costs are assumed to vary linearly
through the planning period and are multiplied by the gradient series
present-worth factor for the same number of years that the corresponding
constant operation and maintenance is paid. This value is computed as:
(1 + Dn-l , 1
gspwf = i d+ i)n U+ i)n
D-12
-------
where: i is the interest rate
n is the number of interest periods that the series is in effect
Gradient series present-worth factors are shown in the third column of
Table D-6. When using this term for computing the present worth of a
variable O&M cost, care must be exercised to insure that the gradient O&M
is used (i.e., the annual average increase in O&M costs during the phase).
If the gradient series does not start at the beginning of the planning period,
it must be adjusted by multiplying it by the single payment present-worth
factor as follows:
(gspwftl) x (sppwft2)
where: tl is the period in which the gradient series is in effect
t2 is the number of years from the beginning of the planning
period to the time the variable payment is started
The new cost effectiveness guidelines require that natural gas prices be
escalated at a compound rate of 4% annually over the planning period unless
the regional administrator determines that a lesser or greater rate can be
used based on regional differentials between historical natural gas price
escalation and construction cost escalation. The inflation factor results
in a geometric increase in the value of natural gas and the geometric series
present-worth factor (gespwf) can be calculated by the following formula:
gespwf -
where: i is the interest rate
n is the number of interest periods that the series
is in effect
a is the appreciation factor
The formula contains three variables. For an appreciation factor of 4% for
natural gas, the present-worth factor for varying interest rates (6 1/4-8%)
and time periods (1-20 years) can be found from column four of Table D-6. The
factor in the table is multiplied by the initial first-year value of the
natural gas. For example, to determine the present worth of natural gas
used over 20 years and which is worth $1,000 at the beginning of the first
year, at an interest rate of 6 1/4% per annum; multiply 15.47730 times $1,000
to get $15,477.30. At this time, the only energy cost which is appreciated
is for natural gas and any present worth analysis which does so must break
out the cost of the natural gas from the rest of the O&M costs. If the geo-
metric series does not start at the beginning of a planning period, it must
be adjusted by multiplying it by the single payment present-worth factor as
follows:
(gespwftl) x (sppwft^)
D-13
-------
where: tl is the period in which the geometric series is in effect
t2 is the number of years from the beginning of the planning
period to the time the variable payment is started
The facility replacement cost identifies the cost required to extend the
useful life of equipment to the end of the planning period. This is com-
puted when a capital item has a service life of less than the remaining
years in the planning period, and is computed by:
Replacement Cost = Planning Period - Remaining Service Life
Service Life
x Capital Value
where: Capital Value represents the capital that would be required
today to completely replace the facility. This is a single-
payment cost, with present worth computed using the factor
sppwf.
Finally, the salvage value represents the value remaining for all capital
at the end of the planning period, and is computed by:
Salvage Value = Service Life - Years to Planning End
Service Life
x Capital
where: Capital (or Capital Value) represents the initial investment
(or cost to replace today). This is a negative cost, with
the present-worth value computed using the factor sppwf.
D.7 References
1. Smith, R., Total Energy Consumption for Municipal Wastewater Treatment,
EPA-600/2-78-149, August 1978"
2. Wesner, G.M.; Gulp, G.L.; Lineck, T.S.; and Hinrichs, D.J.; Energy
Conservation in Municipal Wastewater Treatment, EPA 430/9-77-011,
MCD-32, March 1978
D-14
-------
TABLE D-l
COMPARATIVE CLEAN WATER OXYGEN TRANSFER INFORMATION
FOR AIR AERATION SYSTEMS UNDER STANDARD CONDITIONS (1)
Type of Aeration Device
Range of
Clean Water
Transfer
Range of
Clean Water
Efficiencies
#02/wire HP-Hr
Energy
Requirement
KwH/#02
Mechanical Aerator
Low Speed Surface
High Speed Surface
Turbine Sparger (2) 14 - 18
Fine Bubble Aerators (3)
Fine Bubble Diffuser
(a) Total Floor Coverage 20 - 32
(b) Side Wall Mounted 15 - 20
Jet Aerator (2) 15-26
Coarse Bubble Diffuser (3)
Static Aerator 10 - 16
Coarse Bubble Dual Aeration 10 - 13
Coarse Bubble Single Side
Aeration 8-10
2.5 - 3.5
2.0 - 3.0
2.0 - 3.0
5.0 - 7.5
3.0 - 5.5
2.7 - 3.8
2.3 - 3.2
2.3 - 2.7
2.0 - 2.5
0.21 - 0.30
0.25 - 0.37
0.25 - 0.37
0.10 - 0.15
0.14 - 0.25
0.20 - 0.28
0.23 - 0.32
0.28 - 0.32
0.30 - 0.32
(1) Compiled using a combination of manufacturers' company bulletins,
technical reports, and historically accepted data ranges. See text
on aeration, Section D.2.1, starting on Page D-l for proper use of
table
(2) Includes energy requirements for two prime movers
(3) Based on clean water test at 15" water depth; submergence varies
depending on device.
D-15
-------
TABLE D-2
DESIGN CRITERIA FOR VACUUM FILTRATION
Sludge Type
Primary
Primary ^ Fed,
Primary +
Low Lime
Primary +
High Lime
Primary + WAS
Primary '+
(WAS + Fed3)
(Primary + Fed.,)
+ WAS
Design Assumptions
Thickened to 1C3J solids
polymer conditioned
85 mg/1 Fed., dose
Lime conditioning
Thickening to 2.5% solids
300 mg/1 1ime dose
Polymer conditioned
Thickened to 15% solids
600 mg/1 1ime dose
Polymer conditioned
Thickened to 15% solids
Thickened to 8% solids
Polymer conditioned
Thickened to 8% solids
Fed, & lime conditioned
Thickened primary sludge
to 2.5%
Flotation thickened WAS
to 5*
Dewater blended sludges
Percent
Solids
To VF
10
2.5
15
15
3.5
Typical
Loading
Rates,
fpsf/hr)
8-10
1.0-2.0
10
Percent
Solids
VF Cake
25-38
15-20
32-35
28-32
4-5
3
1.5
16-25
20
15-20
Waste Activated
Sludge (WAS)
WAS + Fed,
Digested Primary
Digested Primary
+ WAS
Thickened to 5% solids
Polymer conditioned
Thickened to 5% solids
Lime +• Fed. conditioned
Thickened to 8-10% solids
Polymer conditioned
Thickened to 6-8% solids
Polymer conditioned
(WAS + Fed.
Tertiary Alum
Fed
lime conditoned
Diatomaceous earth
precoat
8-10
6-8
Digested Primary Thickened to 6-8% solids 6-8
0.6-0.8
2.5-3.5
1.5-2.0
7-8
3.5-6
2.5-3
0.4
15
15
25-38
14-22
16-18
15-20
Source: Wesner, G.M., et al, Energy Conservation in Municipal Wastewater.
MCD-32, EPA-430/9-77-011, March 1978.
D-16
-------
TABLE D-3
DESIGN CRITERIA FOR FILTER PRESSING
Sludge Type
Primary
Primary + Fed,
Primary + 2 stage
high lime
Primary +• WAS
Primary + (WAS + FeClJ
(Primary + FeClj) •»- WAS
WAS
WAS + FeCl3
Digested Primary
Digested Primary + WAS
Digested Primary +
(WAS + FeCl3)
Tertiary Alum
Tertiary Low Lime
Percent
Solids Typical Cycle
Conditioning To Pressure Filter Length
5% FeC13, 10% Lime
10% Lime
None
5% FeCl3, 10% Lime
5% FeCK, 10% Lime
10% Lime
7.5% FeCK, 15% Lime
5S FeCl-j. 10% Lime
5% FeCl3, 10% Lime
7.5% FeCl3, 15% Line
5% FeCl3, 10% Lime
10% Lime
None
5
4*
7.5
8*
8*
3.5*
5*
5*
8
6-8*
6-8*
4*
8*
2 hours
4
1.5
2.5
3
4
2.5
3'. 5
2
2.5
3
6
1.5
Percent
Solids
Filter Cake
45
40
50
45
45
40
45
45
45
45
40
35
55
*Thickening used to achieve this solids concentration
Source: Wesner, G.M. , et
al, Energy^ Conservation in
Municipal Wastewater,
MCD-32, EPA-430/9-77-011, March 1978.
D-17
-------
TABLE D-4
ENERGY CONVERSION* AND
REPRESENTATIVE HEAT VALUES
ENERGY CONVERSION
Type of Conversion
Heat to Mechanical
Heat to Electrical
Mechanical to Electrical
Mechanical to Hydraulic
Electrical to Mechanical
Electrical to Heat
Electric to Hydraulic
Efficiency (%)
s= 38.5
^ 32.5
70-80
> 90
=5100
65-80
REPRESENTATIVE HEAT VALUES OF COMMON FUELS
Anthracite Coal 14,200
Digester Gas 600
Fuel Oil 140,000
Lignite Coal 7,400
Liquified Natural Gas (LNG) 86,000
Municipal Refuse (25% Moisture)
Natural Gas
Propane Gas
Waste Paper (10% Moisture)
Wastewater Sludge 10,000
4,
1,
2,
7,
200
000
500
600
BTU/# Coal
BTU/ft^
BTU/gal
BTU/# Coal
BTU/gal
BTU/lb
BTU/ft3
BTU/ft3
BTU/lb
BTU/lb dry VS
*Refer to References 1 and 2 for further information on energy conversion
in municipal wastewater treatment.
D-18
-------
Multiply
Acres
Atmospheres
Atmospheres
Atmospheres
BTU
BTU
BTU
BTU
BTU/lb
cu ft
cu ft
cu ft
cu ft/second
cu ft/second
cu yd
°F
ft
gal
gal, water
gpd/sp ft
gpm
gpm/sq ft
hp
hp
hp
hp-hr
in
Ib (mass)
mil gal
mgd
ppm (by weight)
psi
sq ft
tons (short)
TABLE D-5
CONVERSION FACTORS
43,560
29.92
33.90
14.70
1.055
777.5
3.927 x ID"4
2.928 x ID'4
2.326
28.32
0.03704
7.481
0.6463
448.8
0.765
0.555 (op - 32)
0.3048
3.785
8.345
0.04074
0.06308
0.06790
0.7457
42.44
33.00
2.685
25.4
0.4536
,785
,785
.000
.895
3
3,
1
6.
0.0929
907.2
To Obtain
in of mercury
ft of water
psi
KJ
ft-lb
hp-hr
Kw-hr
KJ/kg
1
cu yd
gal
mgd
gpm
m
1
Ib, water
m^/m2 • d
1/s
1/m2 • s
Kw
BTU/min
ft-lb/min
MJ
mm
m
3/d
KN/m2
m2
kg
Notes: Energy conversion in practice should take into account the efficiences
shown in Table D-4, e.g. to produce an electrical power of 1 Kwh from
heat energy, the BTU required is 17(2.928 x 1Q-4)(0.325) = 10,508,
but not l/(2.928 x 10~4) = 3.415 which does not include the actual
heat to electrical energy conversion efficiency.
D-19
-------
TABLE D-6
PRESENT WORTH FACTORS
D-20
-------
1/4 PERCENT COMPOUND INTEREST
P R E S E N T W 0 R T H F A C T 0 R S
N
1
••j
3
4
5
6
7
8
9
.10
11
12
1 3
14
15
16
17
18
19
20
SINGLE
PAYMENT
0,94118
0,88581
0,83371
0*78466
0,73851
0,69507
0,65418
0,61570
0,57948
0,54539
0,51331
0,48312
0,45470
0,42795
0,40278
0,37909
0,35679
0,33580
0, 31605
0,29745
UNIFORM
SERIES
0,94118
1,82699
2,66070
3 , 44536
4,18387
4,87894
5,53312
6,14881
6,72830
7,27369
7,78700
8,27012
8,72482
9,15277
9,55555
9,93463
10,29142
10,62722
10,94327
11,24072
GRADIENT
SERIES
0,00000
0,88581
2,55322
4,90722
7. 86 12ft
11. ,33659
15,26167
19,5715*
24,20741
29,1.1596
34 ,24908
39,5*338
45,01975
50,5831.5
56,22204
ft 1,90830
67,61689
73,32546
79,01430
84 , 66594
GEOMETRIC
SERIES 4%
0,94118
1,86242
2,76416
3,64680
4,51075
5,35640
6.18415
6,99436
7,78743
8,56369
9,32352
10,06725
10,79524
11,50781
12,20529
12,88800
13,55625
14,21035
14,85061
15,47730
6 3/8 PERCENT COMPOUND INTEREST - PRESENT WORTH FACTORS
N
1
-.>
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
1.9
20
SINGLE
PAlr'MENT
0,94007
0,88373
0,83077
0,78098
0,73418
0,ft9018
0,64882
0,60993
0.57338
0,53902
0,50672
0,47635
0,44780
0,42096
0,39574
0,37202
0,34973
0, 328/7
0,30906
0,29054
UNIFORM
SERIES
0,94007
1 ,82380
2,65458
3,43556
4,16974
4,85992
5,50874
6,11.867
6,69205
7,23107
7.73779
8,21414
8,66194
9,08290
9,47864
9,85066
.;.
-------
6 1/2 PERCENT COMPOUND INTEREST - PRESENT WORTH FACTORS
N
1
•7
3
4
5
6
7
8
9
10
1 .1.
12
13
14
15
16
17
18
19
20
6 5/8
N
1
•~i
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
SINGLE
PAYMENT
0,93897
0,881 6ft
0,82785
0,77732
0,72988
0,68533
0.64351
0,60423
0,56735
0,53273
0,50021
0 , 46968
0,44102
0,41410
0,38883
0,36510
0,34281
0,32189
0,30224
0,28380
UNIFORM
SERIES
0,93897
1,82063
2,64848
3 , 42580
4,15568
4,84102
5,48452
6,08875
6,65611
7, 18883
7,68905
8,15873
8,59975
9,01385
9,40267
9,76777
10,11058
10,43247
10,73472
11,01851
P E R C E M T C 0 M P 0 U N DIN T E R E S T
SINGLE
PAYMENT
0,93787
0,87959
0,82494
0,77368
0,72561
0,68053
0,63824
0 . 59859
0,56140
0,52651
0,49380
0,46312
0,43434
0,40736
0,38205
0,35831
0,33604
0,31516
0,29558
0,27722
UNIFORM
SERIES
0,93787
1,81746
2,64240
3,41608
4,14170
4,82222
5,46047
6,05905
6,62045
7,14696
7,64076
8.10388
8,53822
8,94558
9,32762
9 . 68593
10,02197
10,33714
10,63272
10,90994
GRADIENT-
SERIES
0,00000
0,88169
2,53741
4,86937
7,78892
11,21560
15,07664
19,30626
23,84509
28,63964
33,64178
38,80829
44,10050
49,48382
54,92739
60,40382
65,88882
71,36095
76.80136
82.19347
GEOMETRIC
SERIES 4X
0.93897
1.85589
2,75129
3,62568
4,47953
5,31335
6.12759
6.92271
7,69917
8,45741
9,19784
9.92090
10,62698
11,31649
11,98981
12,64732
13,28940
13,91641
14,52870
15,12662
PRESENT WURTH FACTORS
GRADIENT-
SERIES
0,00000
0,87958
2,52944
4,85051
7,75295
.1.1 , 15557
14,98503
19,17515
23,66630
28,40491
33,34291
38,43719
43,64930
48,94492
54,29354
59,66814
65,04485
70,40265
75,72314
80.99026
GEOMETRIC
SERIES 4%
0,93787
1.85264
2,74490
3.61519
4,46405
5,29202
6,09960
6,88730
7,65561
8,40500
9,13594
9,84889
10,54429
11,22257
11,88414
12,52944
13,15884
13,77275
14,37.1.54
14,95560
D-22
-------
6 3/4 PERCENT COMPOUND INTEREST
P R E S £ N T W 0 R T H F A C T 0 R S
N
.1.
'P
3
4
5
o
7
8
9
10
11
12
13
14
15
16
17
.1.8
19
20
SINGLE
PAYMENT
0*93677
0,87753
0,82205
0,77007
0.72137
0,67576
0,63303
0,59300
0,55551
0,52038
0,48748
0,45665
0,42778
0,40073
0,37539
0,35165
0,32942
0,30859
0,28907
0,27080
UNIFORM
SERIES
0.93677
1,81430
2.63635
3,40642
4,12779
4,80355
5.43658
t>,02958
6,58509
7,10547
7,59295
8,04960
8,47738
8,87811
9,25349
9,60515
9,93456
10,24315
10,53223
10,80302
o 7/8 PERCENT COMPOUND INTEREST
N
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
•~i r.
SINGLE
PAYMENT
0,93567
0,87548
0,81917
0-76647
0,71717
0,67103
Q.&2787
0,58748
0,54969
0,51433
0,48124
0,45028
0,42132
0,39422
0,36886
0,34513
0.32293
0,30215
0,28272
0.26453
UNIFORM
SERIES
0.93567
1.81116
2.63032
3.39679
4,11396
4.78499
5,41286
6,00033
6,55002
7,06434
7,54559
7,99587
8,41719
8,81140
9,18026
9,52539
9.84832
10,15047
10,4331.9
10,69/?2
GRADIENT
SERIES
0,00000
0,87754
2,52163
4,83184
7,71733
11,09613
14,89432
19,04535
23,48941
28,17282
33, 04758
38,07076
43,20408
48,41355
53,66900
58,94379
64,21445
69,46043
74,66379
79,80891
PRESENT
GRADIENT
SERIES
0,00000
0.87549
2.51381
4.81323
7,68189
11,03704
14,80424
18,91660
23,31408
27.94302
32.75544
37.70856
42.76437
47.88918
53.05318
58,23012
63,39697
08 , 533oO
73,62253
78,64863
GEOMETRIC
SERIES 4%
0,93677
1 .84940
2,73853
3,60475
4,44866
5,27082
6,07181
6,85216
7,01241
8,35307
9.074&5
9.77765
10,46253
11,12977
11,77983
12,41313
13,03013
13,63122
14,21684
14,78736
WORTH FACTORS
GEOMETRIC
SERIES 4%
0,93567
1 ,84617
2.73218
3.59436
4, 43334
5,24975
6,04420
6,81728
7,56957
8,30161
9,01397
9.70716
10.38170
11 .03810
11 .67684
12,29840
12,90323
13,49180
14.0*454
14 ,6218o
D-23
-------
7 PERCENT CONFOUND INTEREST
N
PRESENT WORTH FACTORS
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
SINGLE
PAYMENT
0*93458
0*87344
0,81630
0,76290
0,71299
0,66634
0,62275
0,58201
0,54393
0,50835
0,47509
0,44401
0,41496
0,38782
0,36245
0,33873
0,31657
0,29586
0,27651
0,25842
UNIFORM
SERIES
0,93458
1,80802
2,62432
3,38721
4,10020
4,76654
5,38929
5,97130
6,51524
7,02358
7,49868
7,94269
8.35765
8,74547
9.10792
9,44665
9.76323
10,05909
10,33560
10.59402
7 1/8 PERCENT COMPOUND INTEREST -
N
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
SINGLE
PATHENT
0,93349
0,87.1.40
0.81344
0,75934
0,70884
0,66169
0,61768
0.57660
0,53825
0,50245
0,46903
0,43783
0,40871
0,38153
0,35615
0,33247
0,31035
0,2897.1
0,27044
0,25245
UNIFORM
SERIES
0,93349
1.80489
2,61833
3.37767
4,08651
4.74820
5,36588
5.94248
6,48073
6,98317
7,45220
7.89004
8,29875
8.68028
9,03644
9,36890
9,67925
9,96897
10,23941
10,49186
GRADIENT
SERIES
0 , 00000
0,87345
2.50606
4,79476
7,64671
10,97843
14,7.1494
18,78901
23,14049
27,71562
32 , 46658
37,35071
42.33029
47,37190
52,44617
57,52719
62,59238
67,62207
72.59923
77.50919
PRESENT
GRADIENT
SERIES
0.00000
0,87138
2.49827
4, 77628
7,61161
10,92006
14,62614
18,66232
22,96830
27.49032
32.18063
36.99680
41,90136
46,86125
51.84739
56,83438
61 ,80002
66,72511
71 ,59306
76,38969
GEOMETRIC-
SERIES 4%
0,93458
1,84295
2,72586
3,58401
4,41811
5,22881
6,01679
6.78267
7,52708
8,25062
8,95387
9,63741
10,30178
10,94752
11,57516
12,18520
12,77813
13,35445
13,91460
14,45905
WORTH FACTORS
GEOMETRIC
SERIES 4X
0,93349
1,83975
2.71957
3.57372
4,40296
5,20801
5,98957
6, 74834
7,48497
8,20011
8,89439
9,56841
10,22278
10,85805
11,47480
12,07355
.12,65483
1 3 , 2 1 9 1 6
13,76703
14,29891.
D-24
-------
7 1/4 PERCENT COMPOUND INTEREST - PRESENT WORTH FACTORS
N
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
SINGLE
PAYMENT
0,93240
0,86937
0,81060
0,75581
0,70471
0,65708
0, «>1266
0,57124
0.53263
0,49662
0,46305
0,43175
0,40256
0,37535
0,34998
0,32632
0,30426
0,28369
0,26452
0,24663
UNIFORM
SERIES
0,93240
1,80177
2,61238
3,36818
4,07290
4,72997
5,34263
5,91388
6,44651
to. 943 13
7,40618
7,83793
8,24050
8,61585
8,96582
9,29214
9 , 59640
9,88010
10, 14461
10,39125
GRADIENT
SERIES
0,00000
0,86938
2,49058
4, 75800
7,57687
10,86225
14.53820
18,53691
22,79795
27,26755
31 ,89807
3ft. 64732
41,47811
46 , 3576ft
51,25735
56,15215
61 ,02031
65,84309
70,60438
75,29044
GEOMETRIC-
SERIES 4%
0,93240
1 , 83655
2,71330
3.56348
4,38789
5,18733
5.96254
6,71425
7,44319
8,15004
8,83547
9,50013
10, 14465
10,76964
11,37569
11,96337
12,53324
1 3 , 08585
13,62171.
14,14133
7 3/8 PERCENT COMPOUND INTEREST
PRESENT WORTH FACTORS
N
1
•->
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
SINGLE
PAYMENT
0,93132
0.86735
0,80778
0, 75229
0, 7 00 ft 2
0,65250
0,60768
0,56595
0.52707
0,49087
0,45716
0 , 42576
0.39*51
0 , 36928
0,34392
0 , 32029
0 , 29829
0,27781
0,25873
0,24096
UNIFORM
SERIES
0,93132
1 , 79866
2 . 60644
3,35873
4,05936
4,71186
5,31954
5,88549
ft, 4 125ft
6,90343
7,36059
7,78635
8,18286
8,55214
8,89ft06
9,21635
*,51465
9, 792"»5
10, 05 118
.1.0,29213
GRADIENT
SERIES
0 , 00000
0,86735
2,48290
4,73979
7,54229
10,80479
14,45090
18.41252
22,62910
27,04696
31 ,61852
36.30186
41 .06002
45,86065
50.67550
55.47991
60,25264
64,97534
6*, 632 40
74,21057
GEOMETRfC
SERIES 4X
0,93132
1,83336
2,70705
3,55328
4,37290
5 , 1 6 6 7 7
5.93568
ft. ft 804. 3
7,40177
8.10043
8 . 7 7 7 1 3
9.43257
10.06740
10,68228
1 1,27785
11 ,8546ft
1.2,41336
12,95450
13, 4 78 ft 3
13,98ft28
D-25
-------
7 1/2 PERCENT COMPOUND INTEREST - PRESENT WORTH FACTORS
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
SINGLE
PAYMENT
0.93023
0,86533
0*80496
0*74880
0,69656
0,64796
0*60275
0*56070
0*52158
0*48519
0.45134
0*41985
0*39056
0*36331
0*33797
0,31439
0,29245
0.27205
0,25307
0,23541
UNIFORM
SERIES
0,93023
1.79557
2*60053
3*34933
4,04589
4,69385
5.29660
5.85731
6,37889
6.86408
7.31543
7.73528
8*12584
8*48916
8,82712
9*14151
9,43396
9*70601
9,95908
10,19449
7 5/8 PERCENT COMPOUND INTEREST
N
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
SINGLE
PAYMENT
0,92915
0,86332
0*80216
0,74533
0,69252
0,64346
0*59787
0*55551
0,51616
0.47959
0,44561
0,41404
0,38471
0,35745
0,33213
0*30860
0*28673
0,26642
0,24754
0,23000
UNIFORM
SERIES
0,92915
1,79247
2,59463
3,33996
4.03248
4.67594
5.27381
5,82933
6,34548
6,82507
7.27068
7,68472
8,06943
8*42688
8*75900
9*06760
9.35433
9.62075
9,86829
10.09830
GRADIENT
SERIES
0 . 00000
0*86535
2,47528
4,72168
7 , 50792
10,74774
14,36427
18.28918
22,46185
26,82860
31,34205
35.96044
40,64718
45,37028
50*10181
54,81760
59,49685
64, 12168
68,67695
73,14979
PRESENT
GRADIENT
SERIES
0 , 00000
0,86331
2,46763
4. 70360
7,47368
10,69098
14,27821
18,16678
22,29603
26,61232
31.06842
35.62286
40.23932
44,88617
49,53593
54,16485
58,75256
63.28167
67,73743
72,10752
GEOMETRIC
SERIES 4%
0,93023
1,83018
2.70082
3,54312
4 , 35800
5.14634
5,90902
6,64687
7 , 36069
8,05127
8,71937
9,36571
9,99102
10,59596
11 ,18121
11,74740
12,29516
12,82508
13,33775
13,83373
WORTH FACTORS
GEOMETRIC
SERIES 4%
0,92915
1,82701
2,69462
3.53302
4.34317
5,12604
5.88254
6.61355
7.31995
8.00255
8,66217
9,29956
9,91549
10,51067
11 ,08580
11,64157
12,17861
12,69757
13,19904
13,68363
D-26
-------
7 3/4 PERCENT COMPOUND INTEREST -- PRESENT WORTH FACTORS
N
1
2
3
4
5
6
7
8
9
.1.0
11
12
13
14
15
16
17
18
19
20
7 7/8
N
1
•"}
A*.
3
4
5
6
7
8
9
10
11
.1.2
13
14
15
16
17
18
19
20
SINGLE
PAYMENT
0,92807
0.86132
0.79937
0.74188
0 , 68852
0.63899
0.59303
0,55038
0.51079
0,47405
0,43996
0,40831
0,37894
0,35169
0,32639
0,30292
0,28113
0,26091
0,24214
0,22473
UNIFORM
SERIES
0.92807
1.78940
2.58877
3,33064
4,01916
4,65815
5,25118
5,80156
6,31235
6,78641
7.22636
7.63468
8.01362
8.36531
8,69170
8,99462
9,27575
9,53666
9,77880
10,00353
PERCENT COMPOUND INTEREST
SINGLE
PAYMENT
0,92700
0,85933
0,79659
0,73844
0,68454
0, 03456
0,58824
0,54530
0,50549
0,46859
0,43438
0,40267
0.37328
0.34603
0,32077
0,29735
0,27564
0,25552
0,23o87
0,21958
UNIFORM
SERIES
0,92700
1 , 78633
2,58292
3,32136
4,00590
4,64046
5,22870
5,77400
6,27949
6.74808
7.18246
7.58513
7.95841
8.30443
8,62520
8,92255
9,19819
9,45371
9,69058
9.91015
GRADIENT
SERIES
0,00000
0,86132
2.46006
4,68568
7,43974
10,63470
14,19290
18,04555
22.13J.88
26,39838
30,79794
35,28938
39,83670
44.40865
48,97816
53,52191
58.01997
62,45543
66.81399
71,08381
GEOMETRIC
SERIES 4%
0.92807
1.82385
2.68845
3.52296
4.32842
5,10586
5,85623
6,58049
7,27955
7,95427
8,60552
9,23410
9.84080
10,42638
10,99159
11,53713
12,06368
12,57190
13,06244
13,53591
PRESENT WORTH FACTORS
GRADIENT
SERIES
0.00000
0,85932
2,45252
4.66784
7.40598
10.57879
14,10825
17,92533
21.96925
26.18654
30.53036
34.95974
39.43904
43.93739
48.42811
52,88836
57,29864
61 ,04248
65,90608
70.07800
GEOMETRIC
SERIES 4%
0,92700
1.82070
2,68230
3.51294
4.31375
Si 08580
5,83011
0.54768
7,23948
7,90643
8,54942
9,16931
9,76694
10.34309
10,89855
11,43406
11,95034
12,44806
1.2,92791
13,39052
D-27
-------
8 PERCENT COMPOUND INTEREST - PRESENT WORTH FACTORS
N
1
7
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
SINGLE
PAYMENT
0*92593
0,85734
0*79383
0*73503
0,68058
0*63017
0*58349
0*54027
0.50025
0*46319
0*42888
0*39711
0,36770
0*34046
0*31524
0*29189
0.27027
0.25025
0.23171
0,21455
UNIFORM
SERIES
0,92593
1 . 78327
2.57710
3.31213
3*99271
4.62288
5.20637
5.74664
6.24689
6.71008
7,13897
7,53608
7.90378
8.24424
8.55948
8.85137
9. 12164
9,37189
9,60360
9,81815
GRADIENT
SERIES
0 . 00000
0.85735
2.44502
4,65011
7,37245
10,52330
14,02425
17,80614
21.80813
25*97688
30,26571
34*63395
39,04t>33
43*47233
47*88572
52,26407
56 , 58838
60,84262
65,01342
69,08986
GEOMETRIC
SERIES 4%
0,92593
1*81756
2.67617
3*50297
4*29916
5*06586
5*80416
6*51512
7,19974
7,85901
8*49386
9*10520
9*69389
10,26078
10*80668
11,33236
11,83857
12,32603
12,79543
13,24745
8 1/8 PERCENT COMPOUND INTEREST - PRESENT WORTH FACTORS
N
4
5
6
7
8
9
10
1.1.
12
13
14
15
16
17
18
.1.9
20
SINGLE
PAYhENT
0,92486
0,85536
0,79108
0.73164
0,67666
0*62581
0.57879
0.53529
0,49507
0,45787
0,42346
0,39164
0,36221
0,33499
0.30982
0.28654
0.26501
0,2450'?
,
UNIFORM
SERIES
0.92486
1.78021
2,57129
3.30293
3,97959
4,60540
5,18418
5.71948
6,21455
6,67241
7,09587
7,48751
7,84972
8,18471
8,49453
8,78107
9,0'1-608
9,29117
9,51784
9,72749
GRADIENT
SERIES
0,00000
0,85535
2.43750
4,63241
7.33904
10.46810
13,94079
17,08785
21*64838
25,76918
30.00378
34,31183
38,65834
43*01323
47.35068
51,64877
55.88887
60,05543
64. 1.3557
68,118/6
GEOMETRIC
SERIES 4%
0,92486
1,81443
2,67006
3,49305
4,28465
5,04604
5,77839
6,48280
7,16033
7,81202
8.43885
9.04176
9,62167
10,17945
10,71596
11,23200
11,72835
12,2057o
.1.2,66497
13, 1.0665
D-28
-------
o
i
N5
Control Facilities, EPA-600/2-77-214, November 1977
CO
o
c:
-s
O C
n> _ c
0
0
s:
fD
to
3
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3
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to o
,000
APACITY, gpm
y Requirements for f*'
c
5. o
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C
c+
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3
WIRE TO WATER EFFICIENCY, percent
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\
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y
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\
\
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^
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FIGURE D-1
HYDRAULIC EFFICIENCY OF CENTRIFUGAL PUMPS
-------
FIGURE D-2
POWER REQUIREMENTS FOR RAW SEWAGE PUMPING
a
7
8
9
4
3
2
1,000,000
8
6
s
4
1
o
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tt
a 100,000
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Ul
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10
: 5
umptions
ical constant speed centrifugal
iable level wet well
--
T_.
—
• i
ft
ft
u
t
i
pumps
-
.. .
--
2 34 9(789 2 34 9(789 2 34 96789 2 34 9(789
0.1 1.0 10 100 1,000
FLOW, mgd
Source:
RAW SEWAGE PUMPING (CONSTANT SPEED)
Wesner, G.M., et al, Energy Conservation in Municipal Wastewater,
MCD-32, EPA-430/9-77-011, March 1978
D-30
-------
FIGURE D-3
ANAEROBIC DIGESTER HEATING REQUIREMENTS
10
-a
0)
a-
ai
(U
3
!fl
15
Temp. Difference = Digester Temp. - Influent Sludge Temp.
]% Solids Feed
4%
5%
20 25 30 35
Temperature Difference, °F
40
45
D-31
-------
-a
a;
to
-a
o
GO
c:
o
CQ
c
o
c:
cu
o;
to
CO
o
ro
O)
Q.
^
CL)
4.5
4
3.5
3
2.5
2
1.5
1
0.5
0
FIGURE D-4
ANAEROBIC DIGESTER HEAT LOSS
r
Values shown are for the Northern U.S. For the
r (- Middle U.S., multiply indicated heat requirements
f" by 0.5. For the Southern U.S. multiply heat
requirements by 0.3.
soi-
2%
4%
5%
6/0
10
15
20
25
30
Reactor Hydraulic Detention Time, Days
D-32
-------
FIGURE D-5
ANAEROBIC DIGESTER HEAT PRODUCTION
10 ,
30
Feed Volatile
Solids = 50%
15 ft gas produced/1b of VSS destroyed
1 ft of gas produces 600 BTU
40 50 60
Volatile Solids Destruction, %
70
D-33
-------
10,000,000
FIGURE D-6
HIGH RATE ANAEROBIC DIGESTER MIXING REQUIREMENTS
9
7
6
5
4
3
2
1,000,000
9
8
7
6
K 9
1 «
3
Q
UJ
5
0
UJ
" 100,000
o 9
S '
z 6
UJ S
i :
U 2
UJ Z
UJ
10,000
1
5
4
3
Z
1,000
10
-
Assumptions:
-Continuous operation
-20' submergence for gas
release
-85-93% motor efficiency
/
/
•«
>
.
•
'
^
^
s*
**"
/
^^ —
s
/
f
/
s
/
^
^
/
f
f
J
/
f
s
/
/
~/
f
s
•*
**
/
~/
f
'
f
— i
/
^
/
/
f
s
'
/
'
/
M
''
'
/
r. k i
//*
X X
"tT~jr —
S /
&
/
> FLOW
/
jf :
V
/
/\x
/
x
/
/*
s
sc
^
^
1
FM/
7
^
y
'
, '
/
',
1
/
f
/
'
'<
)0
(f
'
/
* s
s f
S /
f /
/ s
V /
f f
f ^^^
C MIX!
M
^Ml
^
\
/
/,
/
jf
jr
/
/ ,
y
**
:R H
_^
^/
-?
0
'/
kir.10
/
f
f A
f
IT
»/l
XING
1 • •;•
MEt
GAS
:HA
r
f
S
DO
Nl
/
,'-
t
.
)
C
^
• \
\
s
:u
-------
FIGURE D-7
SLUDGE PUMPING ENERGY
FOR HEAT EXCHANGE
25000
20000
1
c
a.
i.
o
o>
O)
(0
o
4J
O
O)
15000
10000
5000
10 20 30 40
Heat Required, Million BTU/day
50
D-35
-------
FIGURE D-7 (a)
ANAEROBIC DIGESTER HEAT REQUIREMENTS
FOR PRIMARY SLUDGE
3.5
T3
e
\
3
m
c —-
o «-
3.0
2.5
UJ &
sc. —
I- «
< O
2.0
cc
UJ
1-
t/)
1.5
DIGESTION
TEMPERATURE:
95°F
30
40 50 60
SLUDGE TEMPERATURE TO DIGESTER,
70
D-36
-------
FIGURE D-7 (b)
ANAEROBIC DIGESTER HEAT REQUIREMENTS FOR
PRIMARY PLUS WASTE ACTIVATED SLUDGE
DIGESTER LOADING'
0.05 Ib VS/doy/cu ft
0. 15
40 50 60 70
SLUDGE TEMPERATURE TO DIGESTER, °F
60
D-37
-------
11.0
10.0
9.0
8.0
7.0
5.0
o
Od
n:
£ 4.0
3.0
FIGURE D-8
FRACTION OF SOLIDS VS WATER CONTENT
0.5 = Volatile Solids Fraction
0.6
(O
1.0
0.1
0.2
0.3 0.4
Fraction of Solids
0.5
D-.ls
-------
FIGURE D-9
FLUE GAS TEMPERATURE
ATTAINABLE AT DIFFERENT WATER CONTENT
Excess
1000 1200 1400
Flue Gas Temperature , °F
D-39
-------
FIGURE D-10
SUPPLEMENTAL FUEL REQUIREMENT
AT 50% EXCESS AIR
50% Excess Air
GO
>
O
C
O
(13
cn
-O
01
01
O)
0)
O-
O-
3
oo
250
Water Content
£ 200
150
100
50
600
800
1000
1200
1400
Flue Gas Temperature, °F
D-40
-------
FIGURE D-ll
SUPPLEMENTAL FUEL REQUIREMENT
AT 100% EXCESS AIR
Q
C
O
IB
CT>
-a
CD
CL
Q.
oo
250 -
200 .
50 -
600
100% Excess
Water Content
WS = 9
800
1000 1200 1400
Flue Gas Temperature, °F
D-41
-------
FIGURE D-12
EXCESS AIR REQUIREMENT
3.0
2.5
c 2 0
o> c"u
01
5 1.5
in
O)
O
X
1.0
0.5
Water Content
W =1.5
800
1000 1200 1400
Flue Gas Temperature, °F
D-42
-------
FIGURE D-13
HEAT RECOVERY FROM WASTE HEAT BOILER
6000
5000
oo
g 4000
ja
H-
CO
-o
-------
10,000,000
X
i 1,000,000
*
JC
Q
UJ
e
5
o
UJ
or
a
oc
UJ
UJ
100,000
o
UJ
_J
UJ
10,000
10
FIGURE D-14
ENERGY REQUIREMENTS FOR VACUUM FILTRATION
9
8
7
6
5
4
3
2
1
9
8
7
6
3
4
3
2
0
§
7
6
5
4
3
2
1
^x
/
^
s^
s
s
/
s
/
/
s
/
/
/
/
/
s
/
/
/
/
/
/
See Table D-2 for design assumptions
Operating Parameters:
2 scfm/sq ft
20-22 inches Hg vacuum
Filtrate pump, 50 ft TDH
Curve includes: drum drive, discharge
roller, vat agitator, vacuum pump,
filtrate pump.
1 1 1 1 1 II 1 1 1 I
•-
-
3 4
56789
100
3 4
56789
1,000
5 6 789
10,000
VACUUM FILTRATION AREA, sq ft
Source: Wesner, G.M., et al, Energy Conservation in Municipal
Wastewater, MCD-32, EPA-430/9-77-011, March 1978
D-44
-------
FIGURE D-15
ENERGY REQUIREMENTS FOR FILTER PRESSING
10,000,000
•f 1,000,000
*
s
-------
FIGURE D-16
ENERGY REQUIREMENTS FORCENTRIFUGING
10,
Operating Conditions:
1
UJ
a
UJ
IT
O
cr
UJ
z
UJ
_J
<
o
o
111
UJ
3
8
7
6
5
4
3
2
,000,000
9
8
7
6
5
4
3
2
100,000
9
8
7
6
5
4
3
2
m nnn
• Dewatering accomplished with low speed centrifuge, G 700'
- Sludge Type Conditions
U Primary + Low Lime
Tertiary + Low Lime
Primary + 2 Stage High Lime
Terti
ary
+
I Stage High Lime
LIME
Cl
/
/
/
/
/
.A SSI
/
/
/
^o Classification
^o Classification
Classification followed b
Dewatering
Classification followed b
Dewatering
A
SLU
FIC/
/
/
/
DG
XTI
/
j
E
ON
/
/
-
/
/
/
/
/
/
/
V
/
/
/
/ ,
/
/
— DEWAl
/
f
/
/
/
"ERir
G
-|
y
y
3 456789
3 4
10
56789
100
56 789
1,000
FLOW, gpm
Source: Wesner, G.M., et al, Energy Conservation in Municipal Wastewater,
MCD-32, EPA-430/9-77-OH, March 1978
D-46
-------
APPENDIX E
INNOVATIVE AND ALTERNATIVE TECHNOLOGY GUIDELINES
L Purpaje. These guidelines provide the
criteria for identifying and evaluating Inno-
vative and alternative waste water treat-
ment processes and techniques. The Admin-
istrator may publish additional information.
2. Authority. These guidelines axe pro-
vided under section 304(d)(3) of the Clean
Water Act.
3. Airplica.lrU.ity. These guidelines apply to:
a. The analysis oi innovative and alterna-
tive treatment processes and techniques
under § 35.91T-l(dX8>:
b. Increased, grants for eligible treatment
works under §§35.330-6 (b) and (c) and
33J308(bXl);
c. The funding, available for Innovative
and alternative processes and techniques
under ?3S.315-Ub):
d. The funding available for alternatives
to. conventional treatment works for small
communities under § 35.915-Ue);
e. The cost-effectiveness preference given
Innovative and alternative processes and
techniques in section 7 of appendix A to this
subpart;
f. The treatment works, that may be given
higher priority on State project priority
lists under 5 35.315(IXUi):
f. Alternative and innovative treatment
systems in connection with Federal facul-
ties:
h. Individual systems , authorized by
J35.918, as modified in that section to in-
clude unconventional or innovative sewers;
L The access and reports conditions in
f 35.935-20.
+. Alternative processes and techniques.
Alternative waste wate%treatment processes
and techniques are proven methods which
provide for the- reclaiming and reuse of
water, productively recycle waste water con-
jtitnents or otherwise eliminate the dis-
charge of pollutants, or recover energy.
«. la Use case of processes and techniques
for the treatment of effluents, these include
land treatment, aquifer recharge, aquacul-
ture, sUvtculture. and: direct nose for indus-
trial, and other nonpotable purposes, horti-
cultore and revegetation oi disturbed- land.
Total containment .ponds and ponds, for the
treatment and storage of waste water pnor
to- land application- and other processes nec-
essary to provide minimum levels of preap-
plirarion treatment are considered to be
pan of alternative technology systems for
the purpose of this section.
ts. For sludges, these include land applica-
tion for norucultural. sUvtcultural. or agri-
cultural purposes (including supplemental
processing by means such as composting or
drying>, and reregetation of disturbed lands.
c. Energy recovery facilities Include codls-
posal measures for sludge and refuse which
produce energy: anaerobic digestion facili-
ties (Provided, That more than 90 percent
of the methane gas is- recovered and used as
fuel): and equipment which provides for the
use of digester gas within the treatment
works. Self-sustaining Incineration may also
be included provided that the energy recov-
ered and productively used Is greater than
the energy consumed to dewater the sludge
to an autogenous state.
d. Also Included are individual and other
onsite treatment systems with subsurface or
other means of effluent disposal and facili-
ties constructed for the specific purpose of
septage treatment.
e. The term "alternative" as used in these
guidelines includes the terms "unconven-
tional" and "alternative to conventional" as
used In the Act.
f. The term "alternative" does not Include
collector sewers, interceptors, storm or sani-
tary sewers or the separation thereof; or
major sewer rehabilitation, except insofar
as they are alternatives to conventional
treatment works for small communities
under § 35.915-Ue) or part of individual sys-
tems under § 35.913.
5. fnnovative processes and tech-nitrites.
Innovative waste water treatment processes
and techniques are developed methods
which have not been fully proven under the
circumstances of their contemplated use
and which represent a significant advance-
ment over the state of the art in terms of
meeting the national goals of cost reduc-
tion, increased energy conservation or recov-
ery, greater recycling and conservation of
water resources (including preventing the
mixing of pollutants with water), reclama-
tion or reuse-of effluents and resources (In-
cluding increased productivity of arid
lands), improved efficiency and/or reliabil-
ity, che beneficial use of sludges or effluent
constituents, better management of toxic
materials or increased environmental bene-
fits. For the purpose-of these guidelines, in-
novative waste water treatment processes
and techniques are generally limited to new
and improved applications of those alterna-
tive processes and techniques Identified in
accordance with paragraph 4 of these guide-
lines, including both treatment at central-
ized facilities and individual and other
onsite treatment. Treatment processes
based on the conventional concept of treat-
ment (by means of biological or physical/
chemical unit processes) and discharge to
surface waters shall not be considered inno-
vative waste water treatment processes and
techniques except where it la demonstrated
that these processes and techniques, as a
E-l
-------
minimum, meet either the cost-reduction or
energy-reduction criterion described in sec-
tion 8 of these" guidelines. .Treatment and
discharge systems Include primary treat-
ment, suspended-growth or fixed-growth
biological systems for secondary or advance
waste water treatment, physical/chemical
treatment, disinfection. 2nd sludge process-
ing. The term "innovative" does not include
collector sewers, interceptors, storm or sani-
tary sewers or the separation of them, or
major sewer rehabilitation, except insofar
u they meet the criteria in paragraph S of
these guidelines and are alternatives to con-
ventional treatment works for small commu-
nities under § 35.915-l(e) or part of individu-
al systems under § 35.918.
6. Cntena for determining innovative
processes and techniques, a. The Regional
Administrator will use the following criteria
in determining, whether a waste water treat-
ment process or technique is innovative.
The criteria should be .read in the context
of paragraph 5. These criteria do not neces-
sarily preclude a determination by the Re-
gional Administrator that a treatment
system is innovative because of local vari-
ations in geographic or climatic conditions
which affect treatment plant design and op-
eration or because it achieves significant
public benefits through the advancement of
technology which would otherwise not be
possible. The Regional Administrator
should consult with EPA headquarters
about determinations made in other EPA re-
gions on similar processes and techniques.
b. New or improved applications of alter-
native waste water treatment processes and
techniques may be innovative' for the pur-
poses of this regulation if they meet one or
more of the criteria in paragraphs eU)
through eiSt of this paragraph. Treatment
and discharge systems (i.e.. systems which
are not new or improved applications of al-
ternative waste water treatment processes
and techniques in accordance with para-
graph 4 of these guidelines) must meet the
criteria, of either paragraph SeU) or 5e<2),
aa a mjnimiim, m order to be innovative for
the purposes of these guidelines.
c. These six criteria are essentially the
same as those used to evaluate any project
proposed for grant assistance. The principal
difference is that some newly developed
processes and techniques may have the po-
tential to provide significant advancements
in the state of the art with respect to one or
more of these criteria. Inherent in the con-
cept of advancement of technology is a
degree of risk which Is necessary to initially
demonstrate a method on a full, operational
scale under the circumstances of its contem-
plated use. This nsfc. while recognized to be
a necessary element in the implementation
of innovative technology, must be mini-
mized by limiting the projects funded to
those which have been fully developed and
shown to be feasible through operation on a
smaller scale. The risk must also be com-
mensurate with the potential benefits (i.e.,
greater potential benefits must be possible
in the case of innovative technology pro-
jects where greater risk is involved).
d. Increased Federal funding .under
35.908(b) may be made only from the re-
serve in § 35.915-Ub). The Regional Admin-
istrator may fund a number of projects
using the-same type of innovative technol-
ogy if he desires to encourage certain inno-
vative processes and techniques because the
potential benefits are great in comparison
to the risks, or if operation under differing
conditions of climatic, geology, etc.. is desir-
able to demonstrate the technology.
e. The Regional Administrator will use
the following criteria to determine whether
waste water treatment processes and tech-
niques are innovative:
(1) The life cycle cost of the treatment
worts is at least 15 percent less than that
for the most cost-effective alternative which
does not incorporate innovative waste water
treatment processes and techniques (I.e.. is
no more than 35 percent of the life cycle
cost of the most cost-effective nonmnova-
tive alternative).
(2) The net primary energy requirements
for the operation of the treatment works
are at least 20 percent less than the net
energy requirements of the least net energy
alternative which does not incorporate inno-
vative waste water treatment processes and
techniques (Is., the net energy require-
ments are no more than 80 percent of those
for the least net energy noninnovaiive alter-
native). The least net energy noninnovative
alternative must be one of the alternatives.
selected for analysis under section S of ap-
pendix A.
(3) The operational reliability of the treat-
ment works is improved in terms of de-
creased susceptibility to upsets or interfer-
ence, reduced occurrence of inadequately
treated discharges and decreased levels of
operator attention and skills required.
(4) The treatment works provides for
better management of toxic materials which
would otherwise result in greater environ-
mental hazards.
(5) The treatment works results in in-
creased environmental benefits such as
water conservation, more effective land use,
improved air quality, improved ground
water quality, and reduced resource require-
ments for the construction and operation of
the works.
(W The treatment works provide for new
or improved methods of joint treatment and
management of municipal and industrial
wastes that are discharged into- municipal
systems.
Cm Doc. 78-27241 Filed 9-28-T3; 8:45 am]
FEDERAL HEG1STW, VOL 43, MO. 1M—WEDNESDAY, SHTEM8E* 27, 1978
E-2
-------
APPENDIX F
THE COST EFFECTIVENESS ANALYSIS GUIDELINES
L Purpose. These guidelines represent
Agency policies and procedures for deter-
mining the most cost-effective waste treat-
ment rrmr-'igemeat system or component
part.
2.-Authority. These guidelines axe pro-
vided under sections 212C2XC) and 217 of
the Clean Water Act.
3. Applicability. These guidelines, except
as otherwise noted, apply to all facilities
planning under step 1 grant assistance
awarded after September 30, 1978. The
guidelines also apply to State or locally fi-
nanced facilities planning on which subse-
quent step 2 or step 3 Federal grant assist-
ance is based.
4. Definitions. Terms-used In these guide-
lines are defined as follows:
a. Was is treatment management system*
Used svno: .ymously with "complete waste
treatment system" as defined in {35.905 of
this subpare.
b. Cost-effectiveness analysis. An analysis
performed c,o determine which waste treat-
ment management system or component
part will r»sult In the minimum total re-
sources c- its over time to meet Federal.
State, or. cal requirements.
c. Planr no period. The period over which,
a waste treatment management system Is
evaluated for cost-effectiveness. The plan-
ning period begins with the system's initial
operation.
d. Useful life. The estimated period of
•time during which a treatment works or a
component of » waste treatment manage-
ment system will be operated.
e. Di3a.gyrtga.tion. The process or result of
breaking down a sum total of population or
economic activity for a State or other juris-
diction (i.e., designated 208 area or SMSA)
into smaller areas or Jurisdictions.
5. Identification, selection, and screening
of alternatives, a. Identification of alterna-
tives. All -'-asible alternative waste manage-
ment sysi-ms snail be initially identified.
These alternatives should Include systems
discharging to receiving waters, land appli-
cation systems, on-site and other non-cen-
tralized systems. Including revenue generat-
ing applicr .ions, and systems employing the
reuse of wastewater and reeycyling of pol-
lutants. In identifying alternatives, the- ap-
plicant shall consider-the possibility of no
action and staged development of the
system.
b. Screening of alternatives. The identi-
fied alternatives shall be systematically
screer.ed to determine those capable of
meeucg the applicable Federal, State and
local criteria.
c. 3-elfction of alternatives. The identified
alternatives shall tw Initially analyzed to de-
termine which systems have cost-effective
potential and which should be fully evaluat-
ed according to the cost-effectiveness analy-
sis procedures established in the guidelines.
d. Extent of effort The extent of effort
and the level of sophistication used in the
cost-effectiveness analysis should reflect the
project's size and Importance. Where proc-
esses or techniques are claimed to be inno-
vative technology on the basis of the cost
reduction criterion contained in paragraph
8eU) of appendix E to this subpart. a suffi-
ciently detailed cost analysis shall be includ-
ed to substantiate the claim to the satisfac-
tion of the Regional Administrator.
6. Cost-effectiveness analysis procedures.
a. Method of analysis. The resources costs
shall-be determined by evaluating opportu-
nity costs. For resources that can be ex-
pressed in monetary terms, the analysis will
use the-Interest (discount) rate established
in paragraph 6e. Monetary- costs shall be
calculated in terms of present worth values
or equivalent annual values over the plan-
ning period defined in section 8b. The anal-
ysis shall descriptively present nonmone-
tary factors (e.g.. social and environmental)
in order to determine their significance and
Impact. Nonmonetary factors include prima-
ry and secondary environmental effects, im-
plementation capability, operability. per-
formance reliability and flexibility. Al-
though such factors as use and recovery of
energy and scarce resources and recycling of
nutrients are to be included in the monetary
cost analysis, the non-monetary evaluation
shall also include them. The most cost-effec-
tive alternative .shall be the waste treatment
management system which the analysis- de-
termines to have the lowest present worth
or equivalent annual value unless nonmone-
tary costs are overriding. The most cost-ef-
fective alternative must also meet the mini-
mum requirements of applicable effluent
limitations, ground-water protection, or
other applicable standards- established
under the Act.
b. Planning period. The planning period
for the cost-effectiveness analysis shall be
20 years.
c. Elements- of monetary costs. The mone-
tary costs to be considered shall include the
total value of the resources- which are at-
tributable to the waste treatment manage-
ment system or to one of its component
parts. To determine these values, all monies
necessary for capital construction costs and
operation and maintenance costs shall be
identified.
(1) Capital construction costs used in a
cost-effective analysis shall Include all con-
tractors' cost* of construction Including
overhead and profit, costs of land, reloca-
tion, and right-of-way and easement acquisi-
F-l
-------
tton; costs of design engineering, field explo-
ration and engineering services during con-
struction; costs of administrative and. legal
services including costs of bond «'T star-
tup costs such as operator training; and in-
terest during construction. Capital construc-
tion costs shall also include contingency
allowances consistent with the cost esti-
mate's level of precision'and detail.
(2) The cost-effectiveness- analysis «h»"
include annual costs for operation and
maintenance (including routine replacement
of equipment and equipment parts). These
costs shall be adequate to ensure effective
and dependable operation during the sys-
tem's planning period. Annual cost* shall be
divided between fixed annual costs and costs
which would depend OQ the *"*"«' quantity
of- .waste water- collected and. treated.
Annual revenues generated by the waste
treatment management system through
energy recovery, crop production, or other
outputs shall be deducted from the annual
costs for operation and maintenance- In ac-
cordance with guidance Issued by the Ad-
ministrator.
d. Prices. The applicant shall calculate the
various components of costs on the basis of
market prices prevailing at the time of the
cost-effectiveness analysis. The analysis
shall not allow for inflation of wages and
prices, except those for land, as described in
paragraph 6h and for natural gas. This
stipulation is based on the implied assump-
tion that prices, other than the exceptions,
for resources involved in treatment worlcs
construction and operation, will tend to
change over time by approximately the
same percentage. Changes in the general
level of prices will not affect the results of
the cost-effectiveness analysis. Natural gas
prices shall be escalated at a compound rate
of 4 percent annually over the planning
period, unless the Regional Administrator
determines that the grantee has Justified
use of a greater or lesser percentage based
upon regional differentials between histori-
cal natural gas price escalation and con-
struction cost escalation. Land prices shall
be appreciated as provided in paragraph
6h(l). Both historical data and future pro-
jections support the gas and land price esca-
lations relative to those for other goods and
services related to waste water treatment.
Price escalation rates may, be updated peri-
odically in accordance with Agency guide-
lines.
e. Interest (.discount} rate. The rate which
the Water Resources Council establishes an-
nually for evaluation of water resource pro-
jects shall be used.
f. Interest during construction. (1) Where
capital expenditures can be expected to be
fairly uniform during the construction
period.'interest during construction may be
calculated at I-1/2PC1 where:
I-the interest accrued during the construc-
tion period.
P-the construction period in years,
C-the total capital expenditures,
I-the Interest rate (discount rate in section
Se).
(2) Where expenditures will not be uni-
form, or when the construction period will
be greater than 4 years, interest during con-
struction shall be calculated on a year-by-
year basis.
g. Useful life. (1) The treatment works'
useful life for a cost-effectiveness analysis
shall be as follows:
Land—permanent.
Waste water conveyance structures (in-
cludes collection systems, outfall pipes,
interceptors, force mains, tunnels,
etc.)—50 years.
Other structures (includes plant building,
concrete process tankage, basins, lift sta-
tions structures, etc.)—30-50'years.
Process equipment—15-20 years.
Auxiliary equipment—10-15 years.
(2) Other useful life periods will be accept-
able when sufficient justification can be
provided. Where a system or a component is
for interim service, the anticipated useful
life shall be reduced to the- penod for inter-
im service.
h. Salvage value. (1) Land purchased for
treatment works. Including land used as.
pan of the treatment process or for ulti-
mate disposal of residues, may be assumed
to have a salvage value at the end of the
planning period a least eqoal to its prevail-
ing market value a th* time of the analyst*.
IB ftaJmtating the salvage value of land, the
land value shall be appreciated at a com-
pound rate of 3 pern nt annually over the
planning period, unles the Regional Ad-
ministrator determines t hat the grantee has
justified the use of a gnater or lesser per-
centage based upon historical differences
between local land cost escalation and con-
struction cost escalation. Thi Vt~j cost esca-
lation rate say be updated periodically In
accordance with Agency guidelines. Right-
of-way easements shall be considered to
hawe a salvage value not greater than t&g
prevailing market value- at the ttme of the
analysis.
(2) Structures will be assumed to have, *
salvage value U there is a me for tiiem. at
the end of the planning period. In this case,
salvage value shall be estimated using
straight line depreciation during the useful
life of the treatment works.
(3) The method used in paragraph 5h(23
may be used ta estimate salvage value at the
«nd of the planning period for phased addi-
tions of. process equipment and auxiliary
equipment.
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(4) When the anticipated useful life of a
facility Is less than 20 years (for analysis of
Interim facilities), salvage value can be
claimed for equipment if it can be clearly
demonstrated that a specific market or
reuse opportunity win exist.
7. Innov&tivt snd alternative vastmter
tmtfnfnt jmcssszs find tevA"ii(ji*w.
a. Beginning October I. 1978, the capital
costs ol publicly owned" treatment -works
which use processes and techniques meeting-
the criteria of appendix E to- this snbpart
and which have only a water pollution con-
trol function, may be eligible tf the present
worth cost of the treatment works is not
more than 115 percent of the present worth
cost of the most cost-effective pollution con-
trol system, exclusive of collection sewers
and Interceptors common to the two sys-
tems being compared, by US percent,
except for the following situation.
b. Where mnoratwe or alternative unit
luuce&aes would serve in Hen of csBrentianal
unit processes in a conventional waste water
treatment plant, and the present worth
costs of the nonconventiooal unit processes
are less than 50 percent of the- present
worth costs of the treatment plant, multiply
the present worth costs of the replaced con-
ventional processes by 115 percent, and add.
ffa^ /.rt.^ gj nonreplaced ""^ processes.
e. The eligibility of multipurpose project*
which combine a water 'pollution control
function with another function, and wfflcft
•use processes- and techniques- meeting the
criteria of appendix S t* this sobpart, shall
be determined ia accordance wrth gaMtnce
issued by the Administrator.
"a1. The above provisions exclude tadlvWnal
system -under § 38.51*. The regional Admin-
istrator may allow a grantee to apply the 15V
percent preference authorised by ttts sec-
tion. to facility plans, prepared under step 1
grast assistance- awarded before Cccobcc 1,
Cest-cffeettve
end aetn«r of
a. PvpuUtitm jwwjeettesa, (1) The dtsag-
gregatlon of State projections of pntinftTto*
shall be the baste for the pncnfttfian fare-
casts presented ta tndftrtdaal Jactttty P*EB.
except a* noted. Ties* Stsoe projection*
sisall 1»e those dereloprt in iSTT 3»y tta
Bureau of Economic Analysis The State grujeettan totals aod the
•dfeaggregatioos wdl be xubmttbed as an
ovtput of the statewide vater qvaiity maa>
«iside & -Hss of designated. 2S8 areas, 'all
•SiMSA*a. and counties or ^
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IJiovtUe rwhrlr aoCo of toe mrrtlin eonsza
wtBi pan 2S of. this rfumnr (See
rii When, the Stase. mujuOJon totals and
used thereafter for area-wide water quality
management planning a* well as for fatality
pj mining md the needs surveys under sec-
tion 516(o) of the Act. Within area wide 208
planning areas, the designated agencies, tn
consultation with the States, shall disaggre-
gate the 208 area projections among the
STM73A and non-SMSA areas and then disag-
gregate these SMSA and nooxSMSA projec-
tions among the facility planning areas and
the remaining areas. For those SMSA's not
included within designated 208 planning
areas, each State, with assistance from ap-
propriate regional planning agencies, shall
disaggregate the S2JSA projection among
the facility 'planning areas and the remain-
Ing areas within the SMSA. The State shall
check the facility planning area .forecasts to
ensure reasonableness and consistency with
the SMSA- projections.
(3) For non-SMSA faefltty planning areas
not Inducted la designated areawide 308
areas, the State may disaggregate popula-
tion projections for non-SMSA counties
among facility planning areas and remain-
ing areas. Otherwise, the grantee is to fore-
cast future population growth for the facili-
ty planning area by linear extrapolation of
the recent past (I960 to present) population
trends for the planning area, use of correla-
tions of planning area growth with popula-
tion growth for the township, county or
other larger parent ares population, or an-
other* appropriate method. A population
forecast may be raised above that indicated
by the e-vteuMuii of past trends -where likely
impacts (e.g.. significant new- energy drrel-
targe new Lutlu&ifiiej* Federal in-
stallations; or institutions) justify the dif-
ference. The facilities plan must document
the justification. These population fiuecaaia
should be based on estimates of new em-
ployment to be generated. The State shall
check individual population forecasts to
Insure consistency with overall projections
for non-SMSA counties and justification for
any difference from past trends.
(55 Facilities plans prepared tinder step 1
grant assistance awarded later than 5
months after Agency approval of the State
disaggregaclons shall follow population fore-
casts developed in accordance with these
guidelines.
b. Waatewi ttr Jlato estimates^ CD In deter-
mining total average daily flow for the
design of treatment works, the flows to be
considered include the average da-fly base
Sows (ADBF) expected from f*****rf\?]
sources; commercial sources, institutional
sources, and industries the works will serve
plus allowances for future Industries and
aooexcesaive infiltration/ inflow. The
amount of nonexcessive Lnfiltraiion/ inflow
not included in the base flow estimates pre-
aemed herein, a to be determined according
to the A«eacy guidance far sewer system
evaluation <« Agency policy "aa treatment
and control of combined sewer overflows
<2> The estimatioe of
ADBF. exclusive of flow
combined residentia
and future
reduction from
eraai and iasu-
tatioaal sources. jh»U be based -upon ooe <*
the following- methods:
(*> Pi*ffm* attVtod. Sxistin* AOBy is es-
timated b*aed upon , a. fuily documented
analysis' of water use records adjusted for
eoasomptioa and looses or oa records «/
wastewater Hows for extended dry periods
less, estimated dry weather infUtraU«n.
Future Qowa for the treaocent worts desjga
stoMid1 b* esciaaated to determiner to* ex-
isting per capita flows based on existing
sewered resident population and multiply-
ing this figure by the future projected popu-
lation to be served. Seasonal population can
be converted to equivalent full time resi-
dents using the following multipliers:
———— 0.1 to 0.3
.... OJ to O.S
The preferred method shall be used wherev-
er water supply records or wastewater flow
data exist. Allowances for future increases
of per capita- flow over time will not be ap-
proved.
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less than 70 sped, or the current population
of the applicant municipality ia under
10,000, or the Regional Administrator
exempts the-area, for having an effective ex-
isting flow reduction program.. Flow reduc-
tion measures Include public education, pric-
ing and regulatory approaches or a- combi-
nation of these. In preparing the facilities
plan and Included .cost effectiveness analy-
sis, the grantee shall, as a minimum:
(1). Estimate the flow reductions Impte-
mentable and cost effective when the treat-
ment works become operational and after 10
and 20 yean of operation. The measures to
be evaluated shall Include a public informa-
tion program; pricing and regulatory ap-
proaches; Installation of, water meters, and
retrofit of toilet dams and low-flow shower-
heads for existing homes and other habita-
tions: and specific changes In local ordin-
ances, building codes or plumbing codes re-
quiring Installations of water saving devices
such as water meters; water conserving toi-
lets, showerheads. lavatory faucets, and ap-
pliances in new homes, motels, hotels, insti-
tutions, and other establishments.
(2) Estimate the costs of the proposed
flow reduction measures over the 20-year
planning period. Including costs of public in-
formation, administration, retrofit of exist-
ing buildings and the incremental costs. If
any, of tn«tjJHng water conserving devices
In new homes and establishments.
(3) Estimate the energy reductions; total
cost savings- for wastewater treatment.
water supply and energy use;- and the net
cost savings (total savings minus total costs)
attributable to the proposed flow reduction
measures over the planning period. The esti-
mated cost savings shall reflect reduced
sizes of proposed wastewater treatment
works plus reduced costs^ of future water
supply facility expansions.
(4) Develop and provide for implementing
a recommended flow reduction .program.
This shall Include a public Information pro-
gram highlighting effective flow reduction
measures, their costs, and the savings of
water and costs for a typical household and
for the community. In addition, the recom-
mended program shall comprise those flow
reduction measures which are cost effective,
supported by the public and within the im-
plementation authority of the grantee or
another entity willing to cooperate with the
grantee.
(5) Take into account tn the design of the
treatment works the flow reduction estimat-
ed for the recommended program.
d. Industrial /lows. (1) The treatment
works' total design flow capacity may in-
clude allowances for Industrial flows. The
allowances may include capacity needed for
Industrial flows which the existing treat-
ment works presently serves. However,
these flows shall be carefully reviewed and
means of reducing them shall be considered.
Letters of intent to the grantee are required
to document capacity needs for existing
flows from significant Industrial users and
for future flows from all Industries Intend-
ing to Increase their flows-or relocate In the
area. Requirements for letters of Intent
from significant industrial dischargers are
set forth In § 35.925-lKc).
(2) While many uncertainties accompany
forecasting future industrial, flows, there Is
still a need to allow for some unplanned
future industrial growth. Thus, the cost-ef-
fective (grant eligible) design capacity and
flow of the treatment works may Include (in
addition to the existing industrial flows and
future Industrial flows, documented by let-
ters of Intent) a nominal flow allowance for
future nonidentifiable -industries or for un-
planned industrial expansions, provided
that 208 plans, land use plans and zoning
provide for such Industrial growth. This ad-
ditional allowance for future unplanned in-
dustrial flow shall not exceed 5 percent (or
10 percent for towns with less than 10,000
population) of the total design flow of the
treatment works exclusive of the allowance
or 25 percent of the total Industrial flow
(existing plus documented future), which-
ever Is-greater.
e. Staffing of treatment plants. (1) The ca-
pacity of treatment plants (Le., new plants,
upgraded plants, or expanded, plants) to be
funded under the construction- grants pro-
gram shall not exceed- that necessary for
wastewater flows projected during an initial
staging period determined by one of the fol-
lowing methods:
(a) First method. The grantee shall ana-
lyze li least three alternative staging peri-
ods (10 years^-45 years, and 20 years). He
shall select-the least costly (Le., total pres-
ent worth or average annual cost) staging
period.
(b) Second method. The staging period-
shall not exceed the period which is appro-
priate according to the following table.
STACZRO Pnioos rox Tmxncnrr PLAJTTS
Flow growth factors (20 yean)*
Staging
period'
(yeara)
Lea* than 1.3-
1.3 to 1.8.
Greater tnan 1.3.
20
15
10
•Ratio of wastewater How expected at end of 20
year planning period to initial flow at the time the
plant Is expected to become operational.
> vr«rimimi initial ata0nc period.
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(2) A municipality may stage the construc-
tion of a treatment plant lor a shorter
period than the maximum allowed under
this policy. A shorter staging period might
be based upon environmental factors (sec-
ondary Impacts) compliance with other envi-
ronmental laws under §35.925-14. energy
conservation, water supply), an objective
concerning planned modular construction.
the utilisation of temporary treatment
plants, or attainment of consistency with lo-
cally adopted plans including comprehen-
sive and capital improvement plans. Howev-
er, the staging period in no case may be less
than 10 years, because of associated cost
penalties and the time necessary to plan.
apply for and receive funding, and construct
later stages.
(3) The facilities plan shall present the
design parameters for the proposed treat-
ment plant. Whenever the proposed treat-
ment plant components' size or capacity
would exceed the minimum reliability re-
quirements suggested in the EPA technical
bulletin, "Design Criteria for Mechanical.
Electric, and Fluid System and Component
Reliability," a complete justification, includ-
ing supporting data, shall be provided to the
Regional Administrator for his approval.
f. Staying-of interceptors. Since the loca-
tion and length of interceptors will influ-
ence growth, interceptor routes and staging
of construction shall be planned carefully.
They shall be consistent with approved 208
plans, growth management plans and other
environmental laws under } 35.925-14 and
shall also be consistent with Executive
orders for flood plains and wetlands.
(1) Interceptors may be allowable for con-
struction grant funding if they eliminate ex-
isting point source discharges and accommo-
date flows from existing habitations that
violate an enforceable requirement of the
Act. Unless necessary to meet those objec-
tives, interceptors should not be extended
Into environmentally sensitive areas, prune
agricultural lands and other undeveloped
areas (density less than one household per 2
acres). Where extension of an interceptor
through such areas would be necessary to
Interconnect two or more communities, the
grantee shall reassess the need for the inter-
ceptor by further consideration of alterna-
tive wastewater treatment systems. If the
reassessment demonstrates a need for the
interceptor, the grantee shall evaluate the
Interceptor's primary and secondary envi-
ronmental impacts, and provide for appro-
priate mitigating measures such as rerout-
ing the pipe to minimize adverse impacts or
restricting future connections to the pipe.
Appropriate and effective grant conditions
(e.g.. restricting sewer hookups) should be
used where necessary to protect environ-
mentally sensitive areas or prime agricultur-
al lands from new development. NFDES
permits shall include the conditions to
insure Implementation of the mitigating
measures *hen new permits are issued to
the affected Ueaiuieiit facilities in those
eases where the measures are required to
protect the treatment facilities against over-
loading.
(2) Interceptor pipe sizes (diameters for
cylindrical pipes) allowable for construction
grant funding shall be based on a staging
period of 20 years. A larger pipe size corre-
sponding to a longer staging period not to
exceed 40 years may be allowed if the grant-
ee can demonstrate, wherever water quality
management plant or other plans developed
for compliance with laws under J"33.925-14
hare been approved, that tt» larger pipe
would be consistent with projected land use
patterns in such plans and that the larger
pipe would reduce overall (primary pica sec-
ondary) environmental Impacts. These envi-
ronmental Impacts include:
(a) Primary impact* (1) Short-term dis-
ruption of traffic, business and ot&er daily
activities.
(11) Destruction of flora and fuma. nois*.
erosion, and sedimentation.
(b) Secondary impacts, (i) Pressure to
rezone or otherwise facilitate unplanned de-
velopment
(U) Pressure to accelerate growth for
quicker recovery of the non-Federal stare
of the interceptor tnvesoneno.
(ill) Effects on air quality and environ-
mentally sensitive areas by cultural
changes.
f3> Th« estimation of peak flows in inter-
ceptors shall be based upon the following
considerations;
(a) Daily and seasonal variations of pipe
flows, the timing of flows from the various
parts of the tributary area, and pipe storage
effects.
(b) The feasibility of off-pipe storage to
reduce peak flows.
(c) The uae of an appropriate peak flow
factor that decreases as the average daily
flow to be -conveyed increases.
9. State yuideiinea. If a State has devel-
oped or chooses to develop comprehensive
guidelines on cost-effective sizing and stag-
ing of treatment works, the Regional Ad'
ministrator may approve- all or portion* of
the State guidance for application to step 1
faculty plans. Approved State guidance may
be used instead of corresponding portions of
these guidelines, tf the following conditions
are met:
a. The State guidance must be at least as
stringent as the provisions of these guide-
lines.
S. The State must have heM at least one-
public hearing on proposed State guidance.
under regulations in part 25 of this chapter.
before submitting tne guidance for Agency
approval.
10. Additional capacity beyond tfie coat-ef-
fective capacilv. Treatment works which
propose to Include additional capacity
F-6
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beyond the cost-effective capacity deter-
mined in accordance with these guidelines
may receive Federal groat assistance if the
following requirements are race
a. The faculties plan shall determine the
most cost-effective treatment Tories and its
associated capacity in accordance with these
guidelines. The facilities plan shall also de-
termine the actual characteristics and total.
capacity of the treatment worfcs to be built.
6. Only a portion of the cost of the entire
proposed treatment Dorics including th« ad-
ditional capacity shall Se eligible for Feder-
al funding. The portion of the cost of con-
struction which snail be eiisibte for Federal
funding under sections 203U) and 30tta> of
the Act shall be equivalent to the estimated
construction costs of the most cost-effective
treatment worts. For the eligibility determi-
nation, the costs of construction of th«
actual treatment worts and the most cost-
effective treatment works must be estimat-
ed on a consistent basis. Up-to-date cost
curves published by ERA'S Office of Water
Program Operations or other cost estimat-
ing guidance shaft be used to determine the
cost ratios between cost-effective project
components and those of the actual project.
These cost ratios shall be multiplied by the
step 3 cost and step 3 contract costs of
actual components to determine the eligible
step 2 and step 3 costs.
c. The actual treatment •works-to be built
shall be assessed. It must be determined
that the actual treatment worts' meets the
requirements of the National Envtronmeo-
tal Policy Act and all applicable laws, regu-
lations, sod guidance, as required of all
treatment works by H3SJ25-8 and 35.923-
14. Particular attention should be given to
assessing the project's potential secondary
environmental effects and to ensuring that
air quality standards will not be violated.
The actual treatment works' discharge must
not cause violations of water quality stand-
ards.
d. The Regional Administrator shall ap-
prove the plans, specifications, and esti-
mates for the actual treatment works under
section 203*3) of the An, even though EPA
will be funding only a portion of its de-
signed capacity.
e. The grantee snail satisfactorily assure
the Agency that the funds for the construc-
tion costs doe to the addtionxl- capacity
beyond the eost-effective treatment works'
capacity as determined by EPA Ci-e_ the in-
eligible portion of the treatment works), as
well as the local share of the grant eligible
portion of the -construction costs will be
available.
f. The grantee shafl execute appropriate
grant conditions or releases providing that
the federal Government is protected from
any further claim by the grantee, the State.
or any other party for any of the coats of
construction due to the additional capacity.
g. Industrial cost recovery shall be baaed
upon the portion of the Federal grant alia-
cable to the treatment of Industrial wastes.
h. The grantee must implement a user
charge system which applies to the entire
service area.of the grantee, including any
area served by the additional capacity.
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*U.S. Government Printing Office: 1 980-O-67 7-094/1112
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