PREPARED FOR THE
TECHNOLOGY TRANSFER DESIGN SEMINAR
DENVER, COLORADO
OCTOBER 31 - NOVEMBER 1.1972
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BROWN AND CALDWELL
CONSULTING ENGINEERS
SAN FRANCISCO, CALIFORNIA
CONTRIBUTORS
D. H. Ca Id well, PhD
G. M. Jones
F. J. Kersnar
P. Kramer
0. Lee
J. Norgaard
D. S. Parker. PhD
R. J. Stenquist
W. R. Uhte
DRAFTING
F. Bolton
REPORT PREPARATION
C. Healy
F. Hicks
W. Martin
A. Morilla
E. Wells
Techni-Graphics. Inc.
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CONTENTS
CHAPTER I. LAGOONS IN WASTE TREATMENT
Types of Lagoons 1
Operating Problems 2
CHAPTER II. TECHNIQUES FOR UPGRADING LAGOONS
Pond Efficiency vs. Pond Loading 5
Pond Recirculation and Configuration 5
Feed nnd Withdrawal 9
Pond Transfer Inlets and Outlets 12
Pond Dike Construction 12
Supplemental Aeration and Mixing 13
Algae Removal 15
CHAPTER III. EXAMPLES OF UPGRADING PONDS
Case 1: Sunnyvale Water Pollution Control Plant 23
Case 2: Los Banos Sewage Treatment Plant 37
Case 3: Stockton Main Water Quality Control Plant 45
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LAGOONS IN W^STE TREATMENT
Types of Ldyoons
Operating ^r >bioms
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CHAPTER I
LAGOONS IN WASTE TREATMENT
Lagoons are one of the most commonly employed secondary waste treatment
systems. In 1968, treatment systems in the general category of stabilization
ponds constituted 34.7 percent of the 9,951 secondary treatment systems operating
in the United States. These "stabilization ponds" served 7.1 percent of the
85,600,000 people served by secondary treatment plants. These stabilization
ponds usually serve small communities; 90 percent were in communities with
10,000 persons or less.
In 1968, Region VIII of the EPA (Montana.Wyoming, Utah, Colorado, North
and South Dakota) contained 756 secondary treatment plants, 74 percent of which
were stabilization ponds. These ponds served 22 percent of the people that were
serviced by secondary treatment plants.
Types of Lagoons
Waste treatment lagoons can be conveniently divided into five general classes
according to the types of biological transformations talcing place in the lagoon.3
Two of those types, high rate aerobic ponds and facultative ponds, are also called
oxidation ponds.
High Rate Aerobic Ponds. In these ponds, algae production is maximized by
allowing mdximum light penetration in a shallow pond. These ponds are generally
only 12 to 18 inches in depth and are intermittently mixed. The main biological
processes are aerobic bacterial oxidation and algal photosynthesis. Organic
loadings range from 60 to 200 Ibs BODs/acre/day. Usually 80-95 percent of the
waste organic matter is converted to algae.
Facultdtive Ponds. Perhaps the most numerous of the pond systems, facul-
tative ponds are deeper than high rate aerobic ponds, having depths of 3 to 8 feet.
The greater depth allows two zones to develop, an aerobic surface zone and an
anaerobic bottom layer. Oxygen for aerobic stabilization in the surface layer is
provided by photosynthesis and surface reaeration while sludge in the bottom
layer is anaerobically digested. Loadings generally range from 15 to 80 Ibs
acre/day, and BOD5 removal from 70 to 95 percent, depending on the concentra-
tion of algae in the effluent. BODs removals as high as 99 percent have been
obtained.
aFor a complete review of the technology and art of this form of treatment,
see 2 and 3.
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Anaerobic Ponds. Organic loads are so high in these ponds that anaerobic
conditions prevail throughout. BODs loadings are generally in the range of 200
to 1000 Ibs BODs/acre/day, and BOD5 removals are limited to about 50 to 80
percent. Anaerobic ponds are usually followed by aerobic or facultative ponds
to reduce the BODg in the effluent.
Maturation or Tertiary Ponds. This type of pond is generally used for
polishing effluents from conventional secondary processes such as trickling
filtration or activated sludge. Settleable solids, BOD5, fecal organisms, and
ammonia aro reduced.. Algae and surface aeration provide the oxygen for stabili-
zation. BODg loadings are generally less than 15 Ibs BOD5/acre/day but may
be higher.
Aerated Lagoons. Aerated lagoons derive most of their oxygen for aerobic
stabilization by mechanical means, either air diffusion or mechanical aeration.
Photosynthetic oxygen generation usually does not play a large role in the process.
Up to 90 to 95 percent BOD^ removals are obtainable depending on detention time
and the degree of solids removal.
Aerated lagoon applications are a relatively new innovation in environmental
engineering technology. The Missouri Basin Health Council reports over 100
aerated lagoon installations 3 in the United States (compared to over three thousand
stabilization ponds in 1968*).
Operating Problems
With increasingly stringent effluent requirements, waste treatment lagoons,
like any other waste treatment process , may require modification to meet all
objectives. The problems that occur with individual ponds, however, may not
be common to all .
Organic Matter in Effluents. An algal-bacteria symbiosis operates in both
aerobic and facultative ponds . Bacteria degrade organic matter according to
the following simplified transformation:
+ H20 (1)
(organics)
Algae, in turn, reuse the carbon (as carbon dioxide) , to form algal bio mass:
C02 + 2H20 + energy algae». CH2O + GZ + HgO (2)
(algae)
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While these equations oversimplify the transformations, they show the
recycling of carbon in ponds. Unless the algae are removed, or the carbon is
removed through methane fermentation in an anaerobic sludge layer, little organic
reduction may occur.^
The fate of algae discharged to receiving waters has received relatively
little attention. This may be because severe problems have not developed in
most instances. Two studies, however, have shown for two differing aquatic
environments that the algae did constitute a BOD load on the receiving waters
and decreased the dissolved oxygen levels.5'6 In these cases, the algae from
the pond effluent were in an unfavorable environment for either their maintenance
or growth, and they decayed (as in equation 1 above).
Aerated lagoon effluents, while not containing large amounts of algae, may
contain biological solids which result from the conversion of a portion of the
BOD5 to biological solids. One aerated lagoon application achieved only 70 per-
cent BOD5 removal; the insertion of a final clarifier in the process allowed 90
percent BOD5 removal because of solids removal.
Odors. That lagoons may occasionally emit odors is shown by the very
common state requirements concerning lagoon location. These require that lagoons
should be located as far from existing or future residential or commercial develop-
ment as is practical or reasonable. Anaerobic ponds particularly tend to have
odor problems due to hydrogen sulfide formation although some methods have
been developed for odor control.
Noxious Vegetative Growths. Without maintenance and good design, aquatic
growths may develop in ponds. Deeper ponds (greater than 3 feet) will discourage
rooted growths, and proper levee maintenance can handle shoreline problems. If
not suitably controlled, noxious plants can choke off hydraulic operation and create
large accumulations of floatable debris. The debris usually becomes septic and
creates odors and conditions detrimental to photosynthetic activity.
Seasonal Performance Variations. In most locales of the United States, there
are seasonal changes in both available light and temperature. Typically, in the
winter algae activity diminishes. Biological activity may also slow; methane
fermentation in facultative ponds may practically cease. Thus, in winter BODs
removals may be low. In Michigan, no discharge is permitted until the spring
thaw when increased biological activity causes a lower effluent BOD5.8
Despite operating problems, which certainly have not occurred with every
lagoon application, lagoons have been providing economical treatment at thousands
of locations for decades. Low capital cost, simplicity of operation and low opera-
tion and maintenance costs have favored lagoon treatment. However, considering
both more stringent water quality criteria and environmental constraints posed by
encroaching suburbanization, many lagoons will have to be upgraded in both treat-
ment efficiency and their mode of operation.
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REFERENCES - CHAPTER I
1. Federal Water Quality Administration, "Municipal Waste Facilities in the
United States", Publication No. CWT-6, 1970.
2. "Second International Symposium for Waste Treatment Lagoons", sponsored by
Missouri Basin Engineering Health Council and Federal Water Quality
Administration, Kansas City, Mo., June 23-25, 1970.
3. Missouri Basin Engineering Health Council, "Waste Treatment Lagoons -
State of the Art11, EPA WOCRS 17090EHX, July, 1971.
4. Oswald, W. J., Meron, A., and Zabat, M.D., "Designing Waste Ponds to
Meet Water Quality Criteria" , pp 186-194 in reference 2.
5. Bain, R. C., McCarty, P. L., Robertson, J. A., and Pierce, W. H., "Effects
of an Oxidation Pond Effluent on Receiving Water in San Joaquin River Estuary,
pp 168-180 in reference 2.
6. King, D. L. , Tolmsoff, A. J., Atherton, M. J., "Effect of Lagoon Effluent on
a Receiving Stream", pp 159-167 in reference 2.
7. Esvelt, L. A., and Hart, H. H., "Treatment of Fruit Processing Waste by
Aeration, Journal of the Water Pollution Control Federation. 42, 7,
pp 1300-1326, 1970.
8. Richmond, Maurice M., "Quality Performance of Waste Stabilization Lagoons
in Michigan", pp 54-62 in reference 2.
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CHAPTER II
TECHNIQUES FOR UPGRADING LAGOONS
Pond Efficiency vs. Pond Loading
Pond Recirculation and Configuration
Feed and Withdrawal
Pond Transfer Inlets and Outlets
Pond Dike Construction
Supplemental Aeration and Mixing
Algae Removal
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CHAPTER II
Ti:cHNiQur:s FOR UPGRADING LAGOONS
Miiny of the techniques dvoilablc [or upgrading lagoons treating primary and
secondary effluents have already been incorporated in designs at one or more
locations—often in the original construction and not as a modification. A well-
designed pond will incorporate physical features which minimize upsets, main-
tenance and nuisances, and maximize operational flexibility, stability and BOD
removal. Physical design features which should be considered include configu-
ration, recirculation, feed and withdrawal variations, pond transfer inlets and
outlets, dike construction, supplementation of oxidation capacity, and algae
removal. These will be discussed in this chapter.
Most of Brown and Caldwell's experience in lagoons concerns those treating
primary or secondary effluents. This discussion will center on those applications.
Many of the waste treatment lagoons in the United States, particularly in the
Midwest, treat raw sewage. One of the ways to upgrade such lagoons is to add
primary or primary plus secondary treatment ahead of the ponds.
Pond Efficiency vs. Pond Loading
It is fairly well established that pond process performance is affected by both
areal BOD loading3 and detention time. 6' 7 Typical data for canning wastes are
shown in Fig. 1. A similar, but not necessarily identical, empirical relationship
would apply to domestic wastes. Fig. 1 shows that pond performance can be im-
proved by three techniques:
1. Increasing pond detention time. Increased detention time will increase
BOD removal and can be accomplished by deepening the pond. The most probable
cause of improvement would be increased algae sedimentation.
2. Decreasing areal BOD loading. Decreased areal BOD loading will increase
the BOD removal by decreasing the carbon to be processed (and recycled to algae).
This can be accomplished by pretreatment; e.g. , placing a primary sedimentation
unit before the pond in a system formerly using only raw sewage ponds.
3. Decreasing areal BOD loading and increase detention time. This can be
done by increasing the number of ponds in the system (e.g., case 2 in Chapter III).
Pond Recirculation and Configuration
Pond recirculation involves interpond and intrapond recirculation as opposed
to mechanical mixing in the pond cell. The effluent(s) from pond cell(s) are mixed
aExcept for aerated lagoons, where areal BOD loading is not an appropriate
design criterion.
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to
Q
Ui
5:
o
Ul
k.
UJ
Q
2OO
100
8O
60
SO
4O
30
2O
I I I I l I I l
95
Q
°96
= 0.859(Y)-°-082e
2O
4O 6O 100 2OO 4OO IOOO
X, LB. BOD/ACRE-DAY
3OOO IO.OOO
Fig. 1 BOD Removal Relationship for Ponds
Treating Cannery Wastes.
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with the influent to the cell. In intrapond recirculation, effluent from a single cell
is returned to the influent to that cell. In interpond recirculation, effluent from
another pond is returned and mixed with influent to the pond (Fig. 2) .
Both methods return active algal cells to the feed area to provide photosyn-
thetic oxygen for satisfaction of the organic load. Intrapond recirculation allows
the pond to gain some of the advantages that a completely mixed environment
would provide if it were possible in a pond. It helps prevent odors and anaerobic
conditions in the feed zone of the pond .
Both interpond and intrapond recirculation can affect stratification in ponds
and thus gain some benefits ascribed to pond mixing which is discussed later.
Pond recirculation is generally not as efficient as mechanical systems in mixing
facultative ponds . Both pond mixing and pond recirculation are incorporated in
the Sunnyvale case example (Chapter III) .
Three common types of interpond recirculation systems (series, parallel, and
parallel-series) are shown in Fig. 2. Others have been suggested but seldom used.
One objective of recirculation in the series arrangement is to decrease the
organic loading in the first cell of the series . While the loading per unit surface
is not reduced by this configuration, the retention time of the liquid is_ reduced.
The method attempts to flush the influent through the pond faster than it would
travel without recirculation. The hydraulic retention time of the influent and re-
cycled liquid in the first, most heavily loaded pond in the series system is:
where V is the volume of pond cell, F is the influent flow rate, r or R/F is the
recycle ratio, and R is the recycle flow rate.
Another advantage of recirculation in the series configuration is that the BOD
in the mixture entering the pond is reduced, and is given by the expression:
S = S. + ( r ) S, (2)
3
where Sm is the BOD of the mixture, S3 is the effluent BOD from the third cell
and Sin is the influent BOD. Thus , Sm would be only 20 percent of Sin with a
4:1 recycle ratio, as So would be negligible in almost all cases. Thus, the
application of organic load in the pond is spread more evenly throughout the ponds,
and organic loading and odor generation near the feed points are less. Recircu-
lation in the series mode has been used to reduce odors in those cases where the
first pond is anaerobic. ^
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RECYCLE
PUMP STATION
(TYP.)
INTRAPOND RECIRCULATION
RECYCLE
-HIHZH
Series
la
Ib
Parallel - Series
Parallel
INTERPOND RECIRCULATION
Fig. 2 Common Pond Configurations and
Recirculation Systems.
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The parallel configuration more effectively reduces pond loadings than does
the series configuration because the mixture of influent is spread evenly across
all ponds instead of the first pond in a series. Recirculation has the same bene-
fits in both configurations.
For example, consider three ponds, either in series or parallel. In the
parallel configuration, the surface loading (Ibs BOD5/acre/day) on the three ponds
is one-third that of the first pond in the series configuration. The parallel con-
figuration, therefore, is less likely to produce odors than the series configuration.
Recirculation is usually accomplished with high volume, low head, propeller
pumps. Fig. 3 presents a simplified cross-section of such an installation. In
this design, the cost and maintenance problems associated with large discharge
flap gates are eliminated by the siphon discharge. An auxiliary pump with an
air eductor maintains the siphon. Siphon breaks are provided to insure positive
backflow protection.
Pumping stations of this type can be designed to maintain full capacity with
minimal increase in horsepower even when the inlet and discharge surface levels
fluctuate over a 3 to 4-foot range. Multiple and/or variable speed pumps are used
to adjust the recirculation rate to seasonal load changes.
Pond configuration should allow full use of the wetted pond area. Transfer
inlets and outlets should be located to eliminate dead spots and short-circuiting
which may be detrimental to photosynthetic processes. Wind directions should be
studied, and transfer outlets located to prevent dead pockets where scum will tend
to accumulate. Pond size need not be limited, as long as proper distribution is
maintained.
Feed and Withdrawal
There is a near unanimity of opinion in the literature that ponds should be fed
by a single pipe, usually towards the center of the pond. This design should be
used for raw sewage treatment by ponds. We have found that with primary or secon-
dary effluent, a single point of entry into a pond tends to overload the pond in the
feed zone, allowing odors to develop. Brown and Caldwell often employs a multiple
entry and single exit approach to evenly distribute the organic load throughout the
pond cell (Fig. 4). One form of multiple inlet, used for ponds as large as 20 acres,
uses inlet head loss to induce internal pond circulation and initial mixing. The
inlet pipe, laid on the pond bottom, has multiple ports or nozzles all pointing in
one direction and at a slight angle above the horizontal. Port head loss is designed
for about one foot at average flow, resulting in a velocity of 8 feet per second.
This induces sufficient mass pond movement to permit the pond outlet to be located
near the inlet. A second outlet, with low head loss and controlled by an overflow
weir, accommodates peak wet weather flow.
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4" AIR t VACUUM
RELEASE VALVE
2"EDUCTOR
POND
SUPPLY
CHANNEL
BAR SCREEN
POND
RETURN
CHANNEL
Fig. 3 Cross-section of a Typical Recirculation
Pumping Station.
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SINGLE ENTRY AND SINGLE EXIT
MULTIPLE ENTRY AND SINGLE EXIT
MULTIPLE ENTRY AND MULTIPLE EXIT
Fig. 4 Methods for Feed and Withdrawal
from Ponds.
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12
The multiple-entry, multiple-exit approach has been used in the Stockton,
California ponds (case 3 in Chapter III). This system was developed to dis-
courage the development of stagnant surface areas within the pond which can
cause development of blue-green algae mats. Such mats can emit odors.
Pond Transfer Inlets and Outlets
Pond transfer inlets and outlets should be constructed to minimize head loss
at peak recirculation rates; assure uniform distribution to all pond areas at all
recirculation rates; and maintain water surface continuity between the supply
channel, the ponds and the return channel.
Transfer pipes should be numerous and large enough to limit peak head loss
to about 3 to 4 inches with the pipes flowing about two-thirds to three-quarters
full. Supply and return channel sizing should assure that the total channel loss
is no more than one-tenth of the transfer pipe losses. When such a ratio is
maintained, uniform distribution is assured.
By operating with the transfer pipes less than full, unobstructed water surface
is maintained between the channels and ponds. This controls scum build-up in
any one area.
Transfer inlets and outlets are usually made of bitumastic-coated corrugated
metal pipe, with seepage collars located near the mid-point. This type of pipe
is inexpensive, strong enough to withstand rough handling and rapid back-
filling, and flexible enough to allow for the differential settlement often en-
countered in pond dike construction.
Specially-made fiberglass plugs can be provided to close the pipes. The plugs
may be installed from a boat. Pond recirculation must be shut down to remove the
plugs. Such plugs permit any pipe to be closed without requiring the expensive
construction of sluice gates and access platforms at each transfer point. Concrete
launching ramps are provided into each pond and channel to assure easy boat
access for sampling, aquatic plant control, and pond maintenance.
Pond Dike Construction
Pond and channel dikes can usually be constructed with side slopes between
6 horizontal to 1 vertical and 2 horizontal to 1 vertical. The final slope selected
will depend on the dike material and the water erosion protection to be provided.
All soils, regardless of slope, will require some type of protection in zones
subject to wave action, hydraulic turbulence or aerator agitation. Some examples
of turbulent zones are areas around the discharge areas at the recirculation pumping
station, and areas around the influent and effluent connections.
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13
If the wind is always in one direction, wave action erosion protection can
usually be limited to only those areas which receive the full force of the wind-
driven waves. Protection should always extend from at least one foot below the
minimum water surface to at least one foot above the maximum water surface.
Protection against hydraulic turbulence should extend several feet beyond
the area subject to such turbulence. Protection material should not impede the
control of aquatic plant growth.
Pond and channel dikes must be kept completely free from grass and aquatic
plants if the ponds are to achieve peak efficiency and operate without odor and
insect nuisance. Weeds and aquatic growths are usually controlled by periodic
spraying, although cutting and actual physical removal are sometimes necessary.
Ponds with luxuriant shoreline growths of cattails and other aquatic plants may
seem healthy and beautiful. Closer inspection, however, reveals that such
growths haibor heavy accumulation of septic scum, which causes odors and loss
of treatment capability.
The tops of the dikes should be at least wide enough for a 10-foot wide, all-
weather gravel road. Such a road is essential for pond inspection, and for the
control of insects, erosion, and plant growth on the dike surfaces.
Fig. 5 shows some details of dike design.
Supplemental Aeration and Mixing
While intermittent mixing has been applied to shallow, high-rate aerobic
ponds, greater attention has been given to mechanical mixing and to aeration
within the cells of facultative ponds. Sometimes, when ponds must treat high,
seasonal BOD loading, under winter conditions, or when there is no more room
for expansion, supplementation of the ponds' photosynthetic oxidation capacity
is required. (When no oxygen is supplied by photosynthesis, the system is
called an aerated lagoon.)
The supplementation is usually achieved by installing compressed air dif-
fusers or mechanical aerators. When the ponds' extra needs are relatively minor
and uniform throughout the year, compressed air aeration may be best. Indeed,
if the ponds are located in a cold climate, year-round aeration may be necessary
to maintain whatever photosynthetic activity is possible during freezing weather.
Preventing surface freezing also allows direct oxygen transfer. When supplemental
oxygen requirements are high or when the requirements are either seasonal or
intermittent, mechanical aerators are used.
In addition to transferring oxygen to the liquid, aeration breaks up the thermal
stratification that normally develops in oxidation ponds. Marais^ reports that the
persistent stratification in ponds diminishes the nonmotile algae population
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THANSIER PIPE INVCRT
MUST Fit TEND AT LFAST
J" UEYONU SLOPE
POND
SUPPLY
O WIDE ACCESS ROADWAY WITH f THICK
AGGREGATT nASE CilUKSF
-TOP OF I THICK RIPRAP EL IO5 OO
BOTTOM OF I" THICK RIPRA
EL IOOOO
OXIDATION
POND
3O" CMP TRANSFER PIPE
CORRUGATED METAL SEEPAGE COLLARS
SEE DETAIL
PROVIDE lO'-O WIDE * II" THICK LAYER OF
RIPRAP SYMMETRICALLY AROUND EACH END
Or TRANSFER PIPE BETWEEN EL IO3 OO
AND IOO 00
TYPICAL DIKE CROSS-SECT ION AT TRANSFER PIPE
NO SCALE
'/«" FIBERGLASS REINF
PLASTIC PLUG
12 GA CORRUGATED METAL
2-0 WIDE BAND (TYP)
PROVIDE OVERLAP
AT ALL JOINTS
WELD SEEPAGE COLLAR
TO BANDS
TYP.SEEPAGE COLLAR DETAIL
NO SCALE
CLAMPS AND SLOTS, SEE SECTION I
-30"CMP
SIDE ELEVATION
END ELEVATION
'/t' • i' FIBERGLASS
REINF PLASTIC CLAMP-
•*li sV
X
i
,5"
*•
'
[5
^Sss
f- PROVIDE Z1/*"*3/** SLOTS AT INTAKE
ENDS OF ALL TRANSFER
PIPES
SECTION0
TYPICAL PLUG DETAIL
NO SCALE
rig. 5 Detaii* cf Oike Design.
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15
because the algae settle below the photic zone and die from lack of light.
Mixing tends to increase algae numbers and to maintain aerobic conditions
deeper in the pond. By increasing algae numbers, the pond can produce more
oxygen, thus increasing its capacity for organic loading.
Surface agitation also breaks up the thin surface layer of slick or scum which
forms on calm days. If not destroyed, the scum layer can diminish performance
both by decreasing the photosynthetic rates and by decreasing surface aeration.
Mechanical aerators are generally divided into two types: cage aerators
(Fig. 6) and the more common turbine and vertical-shaft propeller aerators (Fig. 7).
Cage aerators are relatively new in the United States (see Chapter III, case 1} and
work particularly well in shallow ponds (less than five feet deep). Propeller
aerators require a minimum depth depending on the horsepower of the unit. For
shallow ponds a large number of low horsepower units are required, and the cost
per horsepower rises.
The cage aerator appears to have an area of influence of as much as 1200 feet
(as determined by photographs). While no precise comparison has been made,
this device appears to have a much greater pumping capacity than the propeller
aerator. The latter device tends to recycle much of the volume pumped, especially
in shallow ponds.
Floating propeller aerators are always mounted out in the pond, far enough
apart to minimize interference with each other or other pond features. When used
for shallow ponds, they require minimum depth pits lined with erosion-resistant
surfaces. These surfaces are usually some form of paving, often concrete. Power
access is usually via underwater cable while maintenance access is almost always
by boat.
Floating cage aerators may be mounted either in the pond or directly off
the dike slopes (as at Sunnyvale in Chapter III). When mounted off the dike
slopes, they can be close to the pond transfer inlets. The entire dike slope in
the immediate area is provided with erosion protection. Units mounted on the
slope offer easy access for maintenance and repair, and the extra reliability of
above-water power supply.
Most previous pond aeration systems seem to have utilized diffused aeration.
For best efficiency these require that the ponds be deepened to 10 feet.2
Pond aeration and mixing systems serve mainly to increase the oxidation
capacity of the pond. They are useful in overloaded ponds that generate odors.
Algae Removal
Physical removal of the solids in pond effluents will ensure that virtually all
of the carbonaceous BOD and most of the nitrogenous BOD in the pond effluent will
be removed.
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*1
s—GONCffTC
~( NOT MtfT
, fCXTPT UMPf SKWV
r i
r
HTOUGHT
ElfCW/C COHOUIT HITH
"PLGS JWD PLUGS BOTH £HOS
PL A N - TYPICAL. POND AERATOR
Offflf EQUIPMENT COV£*
UKCTIOt OF
ROTATION
FUMT
2PCT BLMfD
ffOTOf
SECTIONA
SECTION
fiffo ^cmecT-cn
SECTION
Fig. 6 Floating Cage Aerator.
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30'
LABYRINTH SEAL GUARD •
FASTENERS, SAFETY WIRED IN PLACE -
MOTOR SHAFT
17-4 PM STN. STL
ONE PIECE
BOLT AND NUT
IB-B STN. STL
SO HP TEFC MOTOR
4SO V, 3 PHASE, SO HERTZ ,
CLASS V INSULATION
l.li SERVICE FACTOR
NON HYGROSCOPIC WINDINCSt
HEAVY DUTY MOTOR BEARINf !
CORROSION RESISTANT
PAINT
NOTE - STAINLESS STEEL LOCKNUTS
USED BELOW WATER LINE
EXPLOSION PROOF CONDUIT BOX
COMPRESSION LOCK SEAL
PVC DBL JACKET COPPER STRAND ELECT. CABLE
U.L APPROVED FOR UNDER WATER SERVICE
DIFFUSION HEAD. 3O4 STN. STL CAST/NO
ANTI-DEFLECTION INSERT
FLUID DEFLECTOR
y TOP SKIN, 3O4 STN. STL , 14 GAGE
.--ANCHOR CABLE
f BRACKET
\
VOLUTE, 304 STN. STL
PROPELLER. SIS STN. STL
INTAKE CONE
INTAKE CONE CLIP
ANTI-EROSION PLATE ASSEMBLY
>
OUTER SKIN.
3O4 STN. STL., 14 BASE
-POLYURETHANE
FOAM FILLED FLOAT
Fig. 7 Floating Propeller Aerator.
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18
Fig. 8 shows the 30-day effluent BOD from the Stockton, California, ponds
during the canning season in 1970 (Chapter III, case 3). Physical removal of
the algae removed virtually all of the long-term BOD. Very few plant effluents
are regulated on the basis of ultimate oxygen demand. If pond effluents are
subject to such a rigorous investigation, why look only at lagoon treatment?
Fig. 9 shows the 30-day BOD for the effluent of an activated sludge plant in
California also receiving a heavy canning load during the summer of 1970. That
effluent also has a high 30-day BOD. Much less can be removed by solids
separation, presumably because more of the nitrogenous BOD was in the ammonia
form and not removable by physical separation.
With proper design and operation of the pond treatment system, the insertion
of an algae removal step can produce an effluent which is low in both oxygen
demanding materials and nutrients. Table 1 shows recent data obtained by the
Napa County Sanitation District4 from an algae removal pilot plant treating a
tertiary pond effluent.3 The treatment system included lime coagulation, sedi-
mentation, rapid sand filtration, and carbon adsorption. The data shown are for
operation in the summer of 1972. As algae activity diminishes in the winter,
ammonia levels may rise. However, ammonia discharged to the receiving waters
might not stimulate algae growth in the river for the same reasons that pond algae
efficiency drops in the winter. Mechanical removal of algae is described further
in case 3 in Chapter III.
Nitrogen levels in facultative pond effluents may be quite low for several
reasons. Much of the nitrogen in the pond influent may be incorporated into
the algae cell. There also appears to be another distinct nitrogen removal
mechanism. Nitrification appears to take place in the ponds followed by de-
nitrification in the anaerobic bottom zone.
Recovery of algae for animal feed has been investigated over the years;
principal problems lie in developing a market for the product and in finding a
means of separating algae in a manner consistent with purpose of obtaining a
feed. The use of coagulants such as alum generally diminishes the utility of
the product. Dodd, an investigator at the University of California at Davis, has
developed a mechanical system in which paper pulp is precoated on a belt filter,
and algae are removed on the filter as the belt winds around a micro-strainer drum.
The paper-pulp product is vacuum- and heated air-dried to produce an algae-paper
that can be shredded to make feed.^ The algae can provide the protein and the
paper can provide roughage for feeding cattle and sheep. Cost data have not been
developed yet.
The pond system itself can provide for algae removal. Series ponds (Fig. 2)
are recommended by some state regulatory agencies for encouraging algae sedi-
mentation within the pond cells. A parallel-series arrangement (Fig. 2) can also
Preceded by primary sedimentation and trickling filtration.
-------
Q>
lu
Q
U)
X
o
290
20O
ISO
too
o
C
\
/
/
/I— o- — -
/
UNFILTERED
Y
,
, V°~
•} 2
DAYS
/
•
r-FILTEREO
17 3(
'
J tO
Fig. 8 Oxygen Demand Found in Filtered
and Unfiltered Samples of Oxidation
Pond Effluent September 1970
Fig. 9 Oxygen Demand Found in Filtered and
Unfiltered Samples of Activated Sludge
Effluent, September 1970
-------
20
Table 1. Treatment of Pond Effluent for Algae Removal
Constituent
PH
BOD
COD
SS
Turbidityb
P
Org.N
N03
N02
NH3
Total N
Chlorophyll Ac
Pond
effluent,
mg/1
9.4
30
158
102
42
1.7
8.3
0.16
0.18
0.21
9.0
437
Sedimentation
tank,3
mg/1
10.8
3.6
55
23
9
-
1.7
0.18
0.11
0.35
2.2
59
Multi-media
rapid sand
filter,
mg/1
8.0
4.3
37
6
6
-
1.1
0.27
0.11
0.26
-
-
Activated
carbon ,
mg/1
8.5
0.8
13
5.0
3
-
0.46
0.18
0.11
0.17
0.7
19
aPond effluent treated with 200 mg/1 lime as CaO and 50 mg/1 alum as
A12(S04)3 • 18H2O.
bJTU's.
'ug/1.
-------
21
encourage such sedimentation. Sedimentation ponds, however, are limited in
efficiency by such factors as wind mixing and species type. Wind prevents
sedimentation by mixing the water. The smaller the pond, the less influence
wind has on mixing. Sedimentation pond efficiency also depends on species type.
Motile algae and crustaceans are not efficiently removed in such ponds.
McKinney, et al,2 after an extensive review of available data, concluded
that, for small ponds (which are used most often), the best method for algae
separation was the series arrangement, with the final pond used for algae sedi-
mentation. Oswald, et al,10 report a series application of ponds where algae
sedimentation follows a high rate-aerobic pond;3 algae settle out in the sedi-
mentation pond which has a detention time of 13 days and a depth of 8 feet.
Oswald further reports that while the sedimentation pond initially yielded high
algae removals, there has been some deterioration, as blue-green algae grew in
the summer of 1972 from nutrients released from anaerobic fermentation of the
sludge layer. Oswald recommends removal of the bottom sludges in the sedimen-
tation pond every two years to prevent this problem. The Los Banos case example
(Chapter III, case 2) demonstrates a series arrangement to encourage algae removal.
An algae sedimentation pond, unlike a mechanical system, is subject to
variable performance caused by wind mixing, nutrient recycle from the sludge layer,
and changes in algae removal efficiencies resulting from shifts in algae species.
An algae sedimentation pond cannot be expected to operate as efficiently as a
mechanical system; however, such sedimentation ponds do have a place in up-
grading technology since they are far simpler and more economical than mechanical
systems.
aThe entire series treatment system consisted of a facultative pond, a high rate
aerobic pond, an algae sedimentation pond and two maturation ponds in series.
-------
22
REFERENCES - CHAPTER II
1. Oswald, W. J., Ch. 17 in Water Quality Management by P. H. McGavhey,
Sanitary Engineering Research Laboratory, U.C., Berkeley, 1966.
2. McKinney, R. E., Dornbush, J. N., Vennes, J. W., "Waste Treatment
Lagoons - State of the Art", Missouri Basin Engineering Health Council,
EPAWPCRS, 17090EHX, July, 1971.
3. G.V.R. Marais, "Dynamic Behavior of Oxidation Ponds", in "2nd Inter-
national Symposium for Waste Treatment Lagoons", report by Missouri Basin
Health Council and FWQA, edited by R. E. McKinney, pp 15-46, June, 1970.
4. Brown and Caldwell, "Contract for Pond Aerators", document prepared for
City of Sunnyvale, December, 1969.
5. McKinney, R. E. and Benjes, H. H., Jr., "Evaluation of Two Aerated Lagoons",
TSED. ASCE. 91, SA6, 43-55 (1965).
6. Parker, D. S., Monser, J. R., and Spicher, R. G. , "Unit Process Performance
Modeling and Economics for Cannery Waste Treatment", presented at the 23rd
Purdue Industrial Waste Conference, May 7, 8, 9, 1968.
7. McGarry, M. G. and Pescod, M. B., "Stabilization Pond Criteria for Tropical
Asia", in "2nd International Symposium for Waste Treatment Lagoons",
report by Missouri Basin Health Council and FWQA edited by R. E. McKinney,
pp 114-132 (June, 1970).
8. Personal communication, Earl Goodwin to D. S. Parker, July, 1972.
9. Personal communication, Joe Dodd to D. S. Parker, September 27, 1972.
10. Oswald, W. J., Meron, A. A., and Zabat, M. D., "Designing Waste Ponds
to Meet Water Quality Criteria", "Second International Symposium for Waste
Treatment Lagoons", sponsored by Missouri Basin Engineering Health
Council and Federal Water Quality Administration, pp 186-194 (June 19, 1970).
11. Personal communication, W. J. Oswald to D. S. Parker, September, 1972.
12. Richmond, Maurice, M., "Quality Performance of Waste Stabilization Lagoons
in Michigan", in "Second Internationl Symposium for Waste Treatment Lagoons",
sponsored by Missouri Basin Engineering Health Council and Federal Water
Quality Administration, pp 54-62 (June, 1970).
-------
CHAPTER III
EXAMPLES OF UPGRADING PONDS
Case 1: Sunnyvale Water Pollution Control Plant
Case 2: Los Banos Sewage Treatment Plant
Case 3: Stockton Main Water Quality Control Plant
-------
CASE 1:
SUNNYVALE WATER POLLUTION CONTROL PLANT
-------
24
CASE 1:
SUNNYVALE WATER POLLUTION CONTROL PLANT
Sewage treatment facilities for the City of Sunnyvale, California, were first
placed in operation in September 1956. They included: a primary treatment plant
having an average daily capacity of 7.5 million gallons of domestic sewage and
nonseasonnl industrial wastes, and a holding pond with a capacity of 200 million
gallons, for seasonal wastes from two large canneries which processed fruit and
vegetables. Effluents from the primary plant and the holding pond were dis-
charged diiectly to Guadalupe Slough (which is a tributary to south San Francisco
Bay).
By 1960 the domestic sewage flow had reached the capacity of the primary
plant, and conditions in Guadalupe Slough, because more effluents were discharged
from the treatment facilities, had deteriorated so much that they failed, at times,
to comply with the minimum requirements established by the Regional Water Quality
Control Board. In a study authorized by the city. Brown and Caldwell recommended
doubling the capacity of the primary plant and adding an oxidation pond. The fa-
cilities were not completed until 1967.
Growth of both domestic and industrial wastes since I960, and the more
stringent requirements of the Regional Water Quality Control Board required further
improvement of the plant. This was completed by the canning season of 1971; three
more primary settling basins were added (for a total of 9), and aerators were added to the
two ponds. The addition of aerators is the primary concern of this discussion.
Originally, the large pond (325 acres) had been used as an oxidation pond for
secondary treatment of the domestic wastewaters. The wastewater from the
canneries was put directly in the smaller holding pond (100 acres). This pond was
designed to operate anaerobically, with odors controlled by calcium or sodium
nitrate additives. A considerable quantity of nitrate was required and resulted in
high operating costs during the food processing season. Attempted close control
of nitrate addition resulted in insufficient amounts being added at times so that
hydrogen sulfide odors did occur.
Design provided for the effluent from the holding pond to be discharged to the
oxidation pond at a rate which would maintain aerobic conditions in the oxidation
pond. Seasonal wastes increased in quantity and strength beyond expectations
and the holding pond did not have sufficient capacity to contain the waste for the
entire canning season. Since 1960 it was necessary to discharge some of the
holding pond contents to Guadalupe Slough during the canning season.
-------
25
During the past few years, attempts were made to improve the situation by
putting the cannery waste through the primary plant and operating the two lagoons
in parallel. The small pond received heavier loadings, however, and continued
to produce odors. Also, hydrogen sulfide odors continued to develop in Guadalupe
Slough.
In an upgrading step, floating cage aerators were placed near the inlets to
the ponds to increase their oxidation capacity. The aerators are used only during
the canning season when supplemental oxygenation capacity is required. Fig. 6
shows a drawing of the aerator and Fig. 10 a diagram of the ponds. The influent
and the recirculation flows are mixed in the channel. The flow is then discharged
to the ponds through a series of pipes along their edges. The aerators are generally
near the transfer pipes (however, no pipes are located near the last two aerators
of the large pond). Near the last two aerators the discharge line leads from the
pond to the chlorine contact chamber, and then to Guadalupe Slough. These two
aerators prevent short-circuiting of wastewater.
Operating the ponds in this manner has substantially improved effluent quality.
The ponds and Guadalupe Slough contain dissolved oxygen at all times and are odor-
free; fish have returned to the slough. Tables 2 and 3 give design data for before
and after upgrading (1967 and 1971). Table 4 shows operating data for 1970 and
1971. Capital costs for pond upgrading is given in Table 5. Table 6 shows the
operating cost changes caused by plant expansion.
-------
PRIMARY EFFLUENT
EFFLUENT
DISCHARGE
TO GUAOALUPE
SLOUGH
CHLORINE
CONTACT
CHAMBER
OX IDATION
POND t
POND
CIRCULATING
PUMP STATION
AERATORS
OXIDATION
POND 2
Fig. 10 Diagram of Sunnyvale Ponds.
-------
Sunnyvale Sewage Treatment Works. 1969 Enlargment
-------
Cage Aerator
Cage Aerator in Operation
-------
28
Table 2. Sunnyvale Water Pollution
Control Plant Design Data, 1967
Design loadings
Domestic
Daily average flow, mgd 15
BOD, mg/1 270
BOD, Ibs/day 33,600
Suspended solids, mg/1 300
Suspended solids, Ibs/day 37,400
Industrial waste (seasonal)
Daily average flow, mgd 8.0
BOD, mg/1 1,800
BOD, Ibs/day 120,000
Suspended solids, mg/1 500
Suspended solids, Ibs/day 33,000
Preaeration tanks (domestic sewage only)
Number 6
Width, ft 19
Length, ft 35
Average water depth, ft 10.5
Detention time, hrs 0.5
Air supplied per tank, cfm 300
Air supplied per tank, cf/gpm 0.17
Maximum hydraulic capacity per tank, mgd 6.75
Maximum hydraulic capacity bypass channel, mgd 50
Sedimentation tanks (domestic sewage only)
Number 6
Width, ft 19
Length, ft 110
Average water depth, ft 10
Effluent weir per tank, ft L64
Detention time, hrs i.5
Mean velocity, fpm 1.2
Overflow rate, gal/sf/day @ daily avg flow 1,200
Maximum hydraulic capacity, mgd 6.75
Maximum hydraulic bypass channel, mgd 50
-------
29
Table 2 (cont'd)
Primary treatment {domestic sewage only)
Assumed BOD reduction, percent
BOD reduction, mg/1
BOD reduction, Ibs/day
Assumed suspended solids reduction, percent
Suspended solids reduction, mg/1
Suspended solids reduction, Ibs/day
Primary effluent (domestic sewage only)
BOD, mrj/1
BOD, Ibs/day
Suspended solids, mg/1
Suspended solids, Ibs/day
Oxidation pond (domestic sewage only)
Number
Area, acres
Loading, 5-day BOD, Ib/acre/day
Detention, days
Circulation pumps
Number -
Capacity each, gal/min
Head, ft
rngmc-generators
Number
Rated output, kw
Speed, rpm
Frequency, cycles per second
Industrial wastes holding pond
Net water area, acres
Maximum water depth, ft
Maximum capacity, mg
35
95
11,800
60
180
22,400
175
21,800
120
15,000
1
325
67
36
4
44,000
3.5
223/167
1,000/750
66/50
100
6
200
-------
30
Table 3. Sunnyvale Water Pollution
Control Plant Design Data, 1971
Design loadings
Domestic
Average daily flow, mgd
BOD, mg/1
BOD, Ibs/day
Suspended solids, mg/1
Suspended solids, Ibs/day
Industrial waste (seasonal)
Average daily flow, mgd
BOD, mg/1
BOD, Ibs/day
Suspended solids, mg/1
Suspended solids, Ibs/day
Preaeration tanks
Number
Width, ft
Six at
One at
Length, ft
Six at
One at
Average water depth, ft
Six at
One at
Average daily flow, mgd
Six at
One at
Detention time, hrs
Six at
One at
Air supplied per tank, cfm
Six at
One at
Air supplied per tank, cf/gal
Six at
One at
Max hydraulic capacity per tank, mgd
Six at
One at
Max hydraulic capacity bypass channel, mgd
22.5
270
50,000
300
56,000
8.0
1,800
120,000
500
33,000
19.0
20.7
20.5
58.7
10.5
11.0
2.5
7.5
.29
.32
130
250
.074
.048
6.75
20
50
-------
31
Table 3 (cont'd)
Sedimentation tanks:
Number
Width, ft
Length, ft
Average water depth, ft
Effluent weir per tank, ft
Detention time, hrs
Mean velocity, fpm
Overflow rate, gal/sq ft/day
Max hydraulic capacity per tank, mgd
Max hydraulic capacity bypass channel, mgd
Primary treatment efficiency (domestic only)
Assumed BOD reduction, percent
BOD reduction, mg/1
BOD reduction, Ibs/day
Assumed suspended solids reduction, percent
Suspended solids reduction, mg/1
Suspended solids reduction, Ibs/day
Primary effluent (domestic only)
BOD, m.j/1
BOD, Ibs/day
Suspended solids, mg/1
Suspende,d solids, Ibs/day
Oxidation ponds
Number
Area, acres
Average depth, ft
Mechanical aerators
Number
Maximum power, input to rotors, hp
Efficiency, Ibs ©2 input/hp hr
Oxygen input, Ibs/day
Loading, 5-day BOD
Total, Ibs/day
Noncanning season
Canning season
5-BOD reduction capacity
Noncanning season (winter months)
Photosynthetic
Unit, Ibs/acre/day
Total, Ibs/day
9
19
110
10
164
1.5
1.2
1,200
6.75
50
35
95
17,000
60
180
34,000
175
33,000
120
22,000
2
425
4.25
24
1,800
1.86
76,500
33,000
141,000
80
35,000
-------
32
Table 3 (cont'd)
Canning season (summer months)
Photos ynthetic
Unit, Ibs/acre/day
Total, Ibs/day
Mechanical aeration,
Ibs/day
Photosynthetic plus mechanical aeration,
Ibs/day
Detention, days
Noncanning season
Canning season
Circulation pumps
Number
Capacity each, mgd
Head, ft
175
77,000
59,000
136,000
27
20
4
63.5
3.5
-------
33
1. 0005 Removals During Canning Season by Ponds
Before and After Installation of Aerators
July 8 - Oct.l, 1970
(before aerators)
June 30-Oct.2, 1971
(after aerators)
Pond influent
BOD
mg/1
347.2
405.5
103 Ibs/day
67b
64d
Pond effluent
BOD
mg/1
64
29
10 3 Ibs/day
7C
4
Percent
removal3
89
94
Based on mass emission, Ibs/day.
Maximum value 102,000 Ibs/day; effluent value is fairly consistent.
'Does not include BOD in effluent from industrial holding pond.
Maximum value 121,000 Ibs/day.
-------
34
Table 5. Summary of Capital Costs for Sunnyvale Aerators
Aerators (24)
Levee riprap
Aerator anchor blocks
(4.5 cu yd per aerator)
Pond transfer pipes
(6 installed; more may be needed
at other installations)
Pond power load centers (5)
Direct burial cable
Main switch gear
Unload, position, and hook up aerators
$ 587,000
40,000
28,950
32,000
138.710
140,000
24,000
31.900
$1,022,510
-------
35
Table 6. Operating Costs Associated with Pond Upgrading
Gas find electricity
Chemicals
Labor
Total
1970
(before aerators)
$15,000
54,000
0
$69,000
1971
(after aerators)
$58,000
0
10.000
$68,000
Includes power for remainder of plant which was also expanded in 1971
Calcium and sodium nitrate, phosphoric acid, and anhydrous ammonia.
'One employee added in 1971.
-------
CASE 2:
LOS BANGS SEWAGE TREATMENT PLANT
-------
38
CASE 2:
LOS BANGS SEWAGE TREATMENT PLANT
The Los Banos Sewage Treatment Plant, in Los Banos, California, was con-
structed in 1961 for two reasons: the treatment system was too small and in
disrepair; and the system could not meet recent discharge requirements set by
the California Water Quality Control Board. Treatment then consisted of a two-
compartment, 125,000-gallon capacity septic tank originally designed to serve
700 people. Population at that time was 6,800, and the average daily flow was
2.5 mgd. Hydrogen sulfide gas had deteriorated the concrete so much that the
system was inoperative.
In 1960 the Regional Water Quality Control Board established effluent require-
ments for discharge to Mud Slough, the receiving water for the plant effluent.
The pertinent portions of the requirements were:
1. DO in the receiving waters was not to be reduced to less than
5.0 mg/1 for 16 hours in a 24-hour day.
2. Settleable solids were not to exceed 0.5 ml/l/hr.
The treatment facility was constructed to meet these requirements. A con-
current plan was effected to reduce stormwater infiltration, and divert cooling
water from the milk processing industry that was tributary to the plant, thus
reducing the plant influent flow to 0.5 mgd (ADWF). The facility included a pump
station, a comminutor, and two 85-acre raw sewage lagoons (Fig. 12). BOD5
removal was 85 percent on filtered effluent samples.
In 1972 the Regional Board added more constituent requirements:
1. Median BODs must be less than 40 mg/1
2. Median settleable solids must be less than 0.2 ml/1
3. Median MPN must be less than 50/100 ml
4. Chlorine residual must be less than 0.5 mg/1
5. pH must be between 6.5 and 8.5
Since 1969, shock loads of organics had periodically turned the first pond
anaerobic, causing it to give off odors. The Regional Board's requirements stipu-
lated that DO in the ponds must not be less than 1.0 mg/1. Additionally, it
required that discharges should not lower the DO concentration in the receiving
waters below 5.0 mg/1 for 16 hours, and never less than 3.0 mg/1.
-------
39
The proposed two-stage plan expands and alters the existing facility.
Stage I calls for addition of a third pond of 170 acres which will double the pond
area (see Pig. 13). Mechanical aerators will be installed in the first pond cull
and recirculation will be increased to alleviate initial septicity. The long deten-
tion time of 250 dnys and the good climate should promote crustacean growth.
The crustaceans devour the algae, encouraging clarification and sedimentation.
Disinfection will be accomplished by chlorination. The plant effluent now contains
between 20 and 90 mg/l BODg, and little or no settleable solids. If algae removal
is effective the BOD5 of the effluent should be quite low. DO levels in the re-
ceiving waters is presently adequate and should remain so. Settleable solids
should decrease.
If operating experience indicates inadequate algae removal, the construction
of an algal removal facility is proposed (as Stage II). Tables 7 and 8 show design
criteria and operating costs for Stage I.
-------
EFFLUENT TO
MUD SLOUGH
(1-0)
BYPASS
WEIR IN
DIVERSION
MANHOLE
POND 2
(85 AC)
INFLUENT
(1.0)
POND I
(85 AC)
(1.2)
(1.2).
-CROSSOVER
CHANNEL
LEGEND
(3.6) FLOW, mgd (2 INFLUENT PUMPS OPERATING)
— ARROWS INDICATE NORMAL FLOW DIRECTION
O NORMALLY OPEN GATE
• NORMALLY CLOSED GATE
1=1 NORMALLY OPEN CONTROL WEIR
— NORMALLY CLOSED WEIR
Fig. 12 Flow Diagram for Existing Conditions
(at 1.0 mgd-Summer, ADWF).
-------
EFFLUENT TO
MUD SLOUGH
(2.0)
BYPASS
WEIR IN
DIVERSION I
MANHOLE
(2-0)
30 INCH
INTERCEPTOR
POND BYPASS
CONTROL WEIRS-
r-POND 3 SUPPLY
\ CHANNEL
RETURN PIPELINE
RAW SEWAGE
PUMPS
CROSSOVER
CHANNEL
-RECIRC.
CONTROL
VALVE
POND
CIRCULATION
PUMPS
LEGEND
(7.2) FLOW, mgd (2 INFLUENT PUMPS OPERATING)
•*— ARROWS INDICATE NORMAL FLOW DIRECTION
O NORMALLY OPEN GATE
• NORMALLY CLOSED GATE
en NORMALLY OPEN CONTROL WEIR
M NORMALLY CLOSED WEIR
POND 3 RETURN
CHANNEL
Fig. 13 Flow Diagram for Stage I Design
(at 2.0 mgd-ADWF).
-------
42
Table 7. Los Banos Design Data
Component
Basic loading data
Flow, nigd, average
During summer season
During winter season
Wet weather flow, mgd
BOD5.1000 Ibs/day
During summer season
During winter season
Influent pumps
Number
Capacity, each, mgd
Capacity, one unit out of service, mgd
Oxidation pond system
Ponds
Number
Area, net water surface, acres
Volume, mg
Allowable loading during summer season
BOD, Ib/surface acre/day
BOD total, 1000 Ibs/day
Allowable loading during winter season
BOD, Ib/surface acre/day
BOD total, 1000 Ibs/day
Mechanical aerators
Number
Total horsepower
Total capacity, 1000 lba of BOD/day
Pond circulating pumping units
Number
Total capacity, mgd
Chlorination
Chlorination rate, Ibs/day
Chlorination capacity, Ibs/day
1959
2.5
1.8
4.8
6.7
4.1
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
1972
1.0
0.7
4.0
4.6
2.8
2
3.6
3.6
2
170
280
40
6.8
20
3.4
-
—
-
-
-
84
400
Design
2.0
1.4
6.9
9.0
5.6
3
3.6
7.2
3
340
560
40
13.6
20
6.8
3
60
2.2
2
9.0
167
400
Based on motor shaft horsepower of 0.27 for each pound of BOD stabilized per day,
Based on summer flow and dosage of 10 mg/1.
-------
43
Table 8. Operation and Construction Costs
Component
Existing
Stage I
(1)
Construction cost
(incl. Cont., Eng., Legal, Admin.)
Annual costs
O & M
Capital cost
Total annual cost
885,000
4,000
20.000
24,000
490,000
16,300
50.400
66,700
(1)
Estimated.
-------
CASE 3:
STOCKTON MAIN WATER QUALITY CONTROL PLANT
-------
IMPROVING POND EFFLUENT BY ALGAL REMOVAL
What do you do when.you have 630 acres .of recently expanded ponds in your
treatment system and a regulatory, agency tells.you to meet tough new requirements?
The answer: Incorporate them into an advanced waste treatment system and accomplish
the objective.
The City of Stockton, California, is located near the confluence of the San
Joaquin and Sacramento Rivers and:has an unusual-water.-quality problem that
requires a unique solution. The cities of the San Joaquin Valley, and Stockton
in particular, have historically been agriculturally oriented. This has resulted in
industries which produce unusually heavy loadings at the city's main water quality
control plant during peak canning periods.
Stockton faces the problem of serving six canners and six.other major wet
industries, including food processors, in its municipal system. These industries
caused a peak monthly flow to the City's main w.ater,quality control plant,in the
summer of 1970 of 35 million gallons per day (mgd); biochemical oxygen demand (BOD)
loading during that same time-reached a. high of .3,200,000 Ibs/month. Flows during
the remainder of the year are 15 mgd with 945,000 Ibs/month of BOD. Unfortunately.
these peaks occur afthe period.of critical water quality and low flow in the San-
Joaquin River, a tidal estuary of San Francisco Bay into which the plant's effluent ,
is discharged.
The Central Valley. Regional Water Quality Control Board has-established dis-
charge requirements, which include the following provisions: ,
1.. The waste discharge shall "not cause the dissolved oxygen of .the
receiving waters to fall below 5.0 mg/l at any time" .
2 .. The .waste discharge shall "not cause the total nitrogen content of
receiving waters to exceed 3.0 mg/l" .
A study of the dissolved oxygen dynamics of the Stockton Ship Channel, which
provides a deep water link to San Francisco Bay, established the assimilative
capacity of the channel for oxygen demanding materials discharged from the Stockton
main plant. The long-term oxygen demand was found to be principally associated
with algae; therefore, physical removal of the algae from the pond effluent eliminated
most of the long-term BOD. A projection of long-term BOD loads compared to the
assimilative capacity of the water indicated that algal removal would permit the
dissolved oxygen (DO) criterion to be met/ At the same time, algal removal would
also accomplish nitrogen removal, since most of the nitrogen is in the organic form
and associated with algae.
By: Denny S. Parker, Project Engineer, Brown and Caldwell-James B. Tyler,
Supervising Chemist, Environmental Quality Analysts-and Thomas J. Dosh,
Public Works Director, City of Stockton.
-------
To meet the new requirements, Stockton is currently undertaking enlargements
und modifications to its main water quality control plant. A phased design and
construction program has been prepared which will enable the city to be in com-
pliance with waste discharge requirements by February 1974. This program involves
improvements to the entire plant including the following elements: (1) preliminary
treatment, (2) primary sedimentation, (3) secondary treatment (trickling filtration),
(4) tertiary treatment (oxidation ponds and algal removal facilities), (5) disinfection,
and (6) solids treatment.
As a part of this program, pilot algal removal studies were conducted during
the summer of 1971 to provide design and operating criteria.
Alternative Means for Removal
Algal removal can be accomplished in two stages: a first stage consisting of
chemical coagulation and gravity separation and a second stage of multimedia,
rapid sand filtration. The first removal stage accomplishes separation of the
bulk of the algae (60-90 percent) and produces an effluent that can be applied
to filters without excessive backwashing. The first stage can utilize either
flotation (in several modes) or sedimentation. In either case, the well coagulated
and flocculated solids are removed, leaving only dispersed solids in the first
stage effluent. The second stage separation process then removes residual
materials and usually involves the use of a polymer coagulant aid to enhance removals
Sedimentation is widely used to clarify many suspensions. When used for
the removal of algae, it is first necessary to chemically coagulate the algae in
order to remove the repelling charges which stabilize the individual particles.
The treated particles are then aggregated to form particles large enough to settle
out in the sedimentation tank. Sedimentation thus involves three stages: chemical
coagulation, flocculation, and sedimentation, as shown in Fig. 1.
When flotation is used, separation depends on the formation of fine bubbles
which are physically attached to the algae causing them to float to the tank water
surface where they are collected and removed. Chemical coagulation enhances the
effect in the same manner as in sedimentation. It is the algae-bubble-chemical
matrix that is desired for good flotation, rather than large aggregates of chemically
bound algae needed for rapid sedimentation. No separate mechanical flocculation
step is provided in flotation.
Two modes are available for the formation of the fine bubbles: dissolved air
flotation and autoflotation. In dissolved air flotation, a portion of the effluent or
influent is pumped to a pressure tank where the liquid is agitated in contact with
high pressure air to supersaturate the liquid. When this pressurized stream is
released into the influent, fine air bubbles are formed. These bubbles are then
coagulated with the algal cells by the rapid addition of chemicals. The algae-
chemical-bubble "float" is then removed at the surface of the tank. Autoflotation
differs only in that no pressurization is required for the formation of the fine bubbles.
-------
CHEMICALS
FLOCCULATION
COAGULATION
INFLUENT
SEDIMENTATION
EFFLUENT
SEDIMENTATION
REGULATING
VALVE
ALGAE-ALUM FLOAT
INFLUENT
PRESSURE Jt
LMtM
It ALS
J
— i COAGULATION
-|J
SKIMMER
/ V
x >^xxv^
-/ ^Li / V
1 . ^-— ^"1— -
lir
, — '
EFFLUENT
1 *
1
1
SETTLEABLE
SOLIDS
I
I
| RECYCLE (Dissolved Air Mode only)
COMPRESSOR
h— AIR
PRESSURIZATION
FLOTATION
Fig. 1. Alternatives for First Stage Algal Removal
-------
Flotdtion with alum coagulation and rapid sand filtration has proved successful
in Windhoek, South Africa.2,3 ,4,5 The flotation stage produced a reduction in
the five-day BOD from 27.3 to 9..5 milligrams per liter (mg/1) using an alum dose
of 350 mg/1. In another test, the suspended solids were reduced from 280 mg/1
to 94 mg/1. Float solids ranged from 1.4 to 3.7 percent total solids.
• In the Windhoek studies. it was found that flotation could be obtained without
pressurization, a process termed "autoflotation" . In order for this to be effective,
the dissolved oxygen content of the pond effluent must be at a supersaturated level
and exceed 14 mg/1. The supersaturation is released by providing aeration or
carbon dioxide addition and turbulence. The presence of the suspended algae or
alum-algae floe catalyzes the formation of small oxygen bubbles which results from
the change in oxygen partial pressure. The bubbles then attach themselves to the
floe and rise to the surface. When insufficient dissolved oxygen was present, it
was found that flotation could be achieved by aeration of the water under pressure
followed by pressure release. Carbon dioxide was used in conjunction with alum
for two purposes: (1) to promote a change in the partial pressure of oxygen and
encourage gas release, and (2) lower pH to the 7.0 to 6.5 range which is optimum
when alum is used as a flocculant.
The advantages of flotation cited by the Windhoek investigators are: the
separation can be accomplished in shallow flotation tanks with residence times as
low as 6 to 20 minutes as opposed to 3.5 hours in sedimentation, the sludge is
more concentrated than from a sedimentation unit, and higher tank overflow rates
can be used.
The other alternative first stage separation technique, sedimentation, has been
thoroughly evaluated by Dryden and Stern.6 In jar tests, alum proved to be a more
effective coagulant than either lime or ferric sulfate. Jar tests showed that a pH of
6 and an alum dose of 300 mg/1 was necessary to attain turbidities less than 10
Jackson units and total phosphate less than 0.1 mg/1. A pilot plant of sedimentation-
rapid sand filtration produced an effluent equivalent to that of a parallel pilot facility
incorporating a pressurized dissolved air flotation and filtration sequence. Auto-
flotation was not observed. At the Interagency Agricultural Waste Water Treatment
Center at Firebaugh, California, laboratory tests have shown that the flocculation-
sedimentation process could remove 90 percent of the algae. However, sludge could
be concentrated in the sedimentation tanks to only one percent.
Golueke and Oswald8 found in field scale studies of algal removal by sedimen-
tation that a pH of 6.5 and an alum dose of 105 to 120 mg/1 were required. Algal
removals of 94 to 100 percent were obtained in a sedimentation tank with 2 to 3
hours residence time. Underflow solids concentration averaged 1.5 percent.
Incentive for Pilot Study
Both flotation and sedimentation have been established as workable, dependable
processes for the first stage removal of algae by both pilot-scale and field-scale
-------
tests. Itoth processes have been tested successfully on a long-term basis. A
review of past work indicates that flotation may bo economically superior to
sedimentation, because higher overflow rates and lower residence times can be
used, equivalent removals can be obtained for approximately the same chemical dose,
and greater sludge concentration is attained.
Given the projected advantages of flotation in the first stage, it was deemed
desirable to operate a pilot-scale process to determine if flotation was applicable
to Stockton's waste and to develop design concepts and criteria for a full-scale
unit. Of special interest was the comparison of pressurized dissolved air flotation
to the Windhoek mode of oxygen release under supersaturated conditions (auto-
flotation) .
Pilot Plant
A circular pilot flotation unit was rented for the study and located next to the
final pond at the main plant. The pilot plant was modified to allow transfer from
recycle stream pressurization for dissolved air flotation operation to autoflotation
by simple valve changes.
Normal values for the various operating criteria are indicated in Table 1. As
can be seen, the pilot unit was operated at fairly high overflow rates (2 to 2.7
gpm/sq ft) and fairly low residence times (17 to 22 minutes). These rates can be
compared to values for the alternative sedimentation tank design of 0.9 gpm/sq ft for
overflow rate and a detention time of 165 minutes.
Table 1. Operating Criteria for Pilot Study
Autoflotation
without
pressurized recycle
Dissolved air flotation
with
pressurized recycle
Influent flow rate, gpm
Recycle, percent
Recycle flow rate, gpm
Area for clarification, sq ft
Area for thickening, sq ft
Volume, gallons
Recycle pressurization, psig
Air rate, scfm
Surface loading rate, gpm/sq ft
Hydraulic residence time, minutes
29
0
0
14.5
9.5
650
2.0
22
29
33
10
14.5
9.5
650
35-60
0.36
2.7a
Including recycle
-------
Test Period
Flotation was studied from July 9 through September 24, 1971. Pond condi-
tions during the test period were affected by canning operations and are illustrated
in Figs. 2 and 3. It was observed that suspended solids in the pond effluent in-
creased when wind stirred up the pond. Alkalinity, after fluctuating in July, rose
steadily in August and September. The pH varied both daily and hourly.
Pond solids during initial operations were lower than desired for meaningful
test work so the first 9 runs prior to July 22 were used for equipment checkout, and
modification and establishment of procedure. Between July 22 and August 25, the
autoflotation mode was evaluated exclusively and from August 26 to September 25,
operation was in the dissolved air flotation mode.
Autoflotation
The principal concern in the study of autoflotation was to establish whether it
could be used to dependably accomplish algal removal in the face of fluctuating
pond conditions at Stockton.
Successful autoflotation is related to dissolved oxygen concentrations in
excess of dissolved oxygen saturation levels (the saturation level is approximately
9 mg/1 and depends on liquid temperature). It was found on two occasions that the
autoflotation process would not function at all when the dissolved oxygen concen-
tration fell below 8 mg/1. Once the dissolved oxygen concentration was above
13-15 mg/1, the autoflotation process functioned. Since dissolved oxygen levels
drop below saturation levels in the night and early morning, autoflotation was
inoperative for portions of each day.
The jar test work indicated that pH adjustment is essential for optimum auto-
flotation performance. The reasons for this appear to be two-fold: (1) alum
flocculation is optimum in the pH 6 to 7 range, and (2) a drop in pH increases the
level of carbon dioxide (CC^) in solution. An increase of the CC>2 level in solution
will increase the partial pressure of CO2 and, therefore, increase the probability of
bubble formation due to combination of dissolved oxygen and CO£ to form a bubble.
Adjusting the pH with CC>2 in autoflotation proved to be more effective than pH
adjustment with acid. Suspended solids removals with CC^ for pH adjustment
averaged 79 percent; with acid, the suspended solids removal averaged 44 percent
(runs 12 to 19). Alum dose ranged from 75 to 200 mg/1, acid, when used, ranged
from 1.5 to 2.3 meq/1.
In summary, autoflotation exhibited a potential for algal solids removal, but
performance was erratic. Autoflotation depends on the algal system to produce
sufficient supersaturation of dissolved oxygen to allow the release, under proper
conditions, of fine bubbles. However, this process is not continuous and, therefore,
autoflotation could not be relied upon as the only means of algal solids removal. The
field evaluation of autoflotation will allow the positive aspects of the phenomenon
-------
Ill
14 20
AUGUST
8 14 20 26
SEPTEMBER
Fig. 2. Suspended Solids in Pond Effluent
-------
400
EJ Alkalinity
IOO
8
12 16 2O 24 28
JULY
13 17 21 25 29
AUGUST
6 10 /4 18 22 26 3O
SEPTEMBER
Fig. 3. Pond Alkalinity and pH
-------
to be utilized in the plant design and the negative aspects to be avoided. For
instance, autoflotation can be used to assist dissolved air flotation. However, if
flocculation-sedimentation is chosen to be the first stage separation process,
special efforts would have to be undertaken to avoid the formation of fine bubbles
prior to sedimentation and thus avoid flotation in the sedimentation unit.
Dissolved Air Flotation
After the period of somewhat erratic algal separation performance with auto-
flotation, attention was turned to the evaluation of dissolved air flotation. This
involves the mechanical saturation of dissolved air in a portion of the liquid stream
(influent or effluent recycle). The release of the dissolved gases to form fine
bubbles in the influent stream while adding alum or other coagulants allows the
separation of suspended materials to take place by flotation.
Five runs involved the use of alum alone without pH control or coagulant
aids. The alum doses ranged from 75 to 225 mg/1 and suspended solids removal
averaged 72 percent. The highest alum doses were generally associated with
high suspended solids concentrations in the pond. Solids levels ranged from 53
to 142 mg/1.
Four runs involved pH control with acid and higher alum doses to demonstrate
the ability of flotation to achieve higher removals than were attained when no pH
control was used. Suspended solids removal averaged 87 percent for an alum dose
of 200 to 250 mg/1 and acid addition of 2.0 to 2.7 milliequivalents per liter (meq/1).
The acid level was adjusted to yield the optimum pH of 6.4 to 6.5. Suspended solids
in the influent during this period ranged from 94 to 152 mg/1.
In summary, once initial operating difficulties were resolved, dissolved air
flotation proved to be an effective process for the first stage separation of algae.
The separation efficiency is closely related to chemical dose. Since the purpose
of the first stage separation process is the preparation of an effluent that is suitable
for filtration, the first stage process must be flexible enough to respond to changes
in influent quality while maintaining consistent effluent quality. A significant
variation in suspended solids can be expected through the canning season (Fig. 2).
When suspended material in the pond effluent is low, alum alone in a dose range of
75 to 150 mg/1 will yield sufficient suspended solids removal (on the order of 60 to
70 percent ) prior to filtration. In portions of August and September when increased
canning loads cause an increase in pond effluent solids, the alum dose will have
to be increased to 150 to 250 mg/1 range with acid pH control in a dose range of
1.5 to 2.7 meq/1. This will increase flotation removals to 85 to 92 percent and
yield an effluent suitable for filtration.
Long-Term BOD Removal Efficiency
Samples of flotation influent (pond effluent) and flotation effluent during
September were subjected to long-term oxygen demand analyses. Both total and
-------
soluble BOD was determined for the influent and effluent samples (Fig. 4).
During the peak of the canning season, most of the BOD is associated with the
suspended matter. Removal of the suspended material by coagulation and flotation,
caused the total effluent BOD to be low and nearly equal to the soluble BOD. The
difference between filtered influent and effluent BOD may have been due to the
coagulation of colloidal materials.
Float Recovery
In addition to its primary objective of removing the suspended algal material
from the liquid stream, flotation demonstrated a unique capability of concentrating
the separated materials as float to a much greater extent that can be obtained in
sludge concentration by the sedimentation process alone. There are two reasons
for this.
First, float removal from the flotation unit takes place on the liquid surface
where the operator has good visual control over the thickening process. He,
therefore, can see the immediate effects of changes in operating variables such
as the speed of the float skimmer, float skimmer submergence, and float blanket
depth. Second, thickening of the float takes place by drainage of the liquid from
the float. This mechanism has a greater driving force promoting thickening than
the mechanism of thickening in sedimentation which involves setting and compaction
of the loose algae-alum floe.
During the experimental work, it was found that variation in thickening
operation did yield improvements in float concentration. For instance, initial
float concentration was improved from 0.13 percent to values averaging 2.45
percent by decreasing the float skimming frequency from 2-3 minutes to 15-30
minutes. A further improvement in float concentration was attained by altering
the float skimmer submergence so that the skimmer was positioned slightly
above the water surface level to minimize inclusion of water in the float. This
increased float concentration to an average concentration of 3.6 percent. This
was attained despite the fact that skimming frequency was simultaneously reduced
to 7 to 8 minutes.
It was found that an anionic polymer, Dow A-23, could significantly increase
float concentration even further (runs 27 to 29). As little as 0.25 mg/l of A-23,
employed as a coagulant aid, increased float concentration to 5.3 percent. No
improvement in effluent clarity was obtained over the use of alum alone. A
cationic polymer, Dow C-31 was also tried, but did not improve either float con-
centration or effluent clarity when used in conjunction with alum.
In summary, flotation has demonstrated an in-process ability to achieve signi-
ficant thickening of the algae-alum sludge produced. Such initial thickening has a
beneficial impact on the economics of further solids processing, since processing
will not require an extra initial thickening step.
-------
100
INFLUENT TOTAL
(Pond Effluent)
r-INFLUENT SOLUBLE
\ (Pond Effluent)
EFFLUENT TOTAL
EFFLUENT SOLUBLE
I i
15
DAYS
20
25
30
Fig. 4 . Oxygen Demand of Flotation Unit
Influent and Effluent
-------
Solids Processing
Solids samples were collected and subjected to alternative treatment processing
by various processes on a batch scale.
Heat treatment by the Porteous process at temperatures ranging from 380 to
415°F improved the slurry dewaterability on a vacuum filter, but the process was
disappointing in terms of both filter yield and cake concentration. Filter yield
was uniformly low in the range of 0.9 to 2.5 pounds per square foot per hour
(Ibs/sq ft/hr). The highest cake concentration achieved was 21.6 percent total
solids with a low value of 8.3 percent, which is not a great improvement over the
feed concentration of 4 percent. At these cake concentrations, incineration of
the cake would be expensive in terms of fuel costs.
Zimpro low oxidation at temperatures ranging from 180 to 220°C, yielded
vacuum filter cake concentrations ranging from 15 to 19 percent total solids at
filter yield ranging from 0.67 to 3.05 Ibs/sq ft/hr. Incineration of the filter cake
under these conditions would still be costly.
Zimpro wet air oxidation was also investigated as a process which would lead
directly to ultimate disposal of the sludge. In evaluating this process, cake con-
centration and filter yield were marginal, indicating that ultimate disposal should
incorporate lagoons. In this process, the reduction of volatile solids is the
important step in producing a stable end product. The high oxidation process
removes about 97 percent of the volatile suspended solids from the sludge. Although
some of the volatiles are solubilized in the liquid, the final solids are stable and
would be suitable for lagoon storage.
Two other processes investigated were chemical oxidation schemes which
employ chlorine as the oxidant. Both of these processes , Pepcon and Purifax,
were capable of achieving stabilization of the sludge and yielded a product that
could be dewatered on sand drying beds or in a lagoon.
Conclusions
Field tests have proved that dissolved air flotation is a viable alternative to
sedimentation for algal removal at Stockton. Further, capital costs will be less
owing to the much smaller tanks required for flotation than for sedimentation. If
sedimentation facilities were to be designed for canning season use, special
attention would have to be given to providing facilities to prevent autoflotation.
The facilities at Stockton will be designed as dual purpose units so that the
tanks can be used for sedimentation during the low flow, non-canning period. The
system employing flotation and filtration is currently under design. Four 80-ft
diameter circular flotation units are planned. By 1974, Stockton will be operating
a 55 mgd algal removal facility, the largest of its type in the world.
-------
nowludg ments
The City of Stockton treatment plant staff, under the direction of Mr. Art
Vieira, Utilities Division Superintendent, made all field modifications to the
pilot unit and conducted most of the chemical analyses. Certain special
analyses were made by Environmental Quality Analysts, Inc., a division of
Brown and Caldwell. The flotation unit was rented from the Eimco Division
of The Envirotech Corporation.
Test work on solids processing alternatives were run by the Envirotech
Corporation, Zimpro, Inc., Pacific Engineering and Production Co. of Nevada,
and BIF.
-------
References
1. Brown and Caldwell, "Benefits of Proposed Tertiary Treatment to San Joaquin
River Water Quality," prepared for the City of Stockton, November 1970.
2. Van Vuuren, L.R.J. and Van Duuren, F.A., "Removal of Algae from Waste
Water Maturation Pond Effluent," Journal of the Water Pollution Control
Federation (JWPCF), Vol. 37, No. 9, pp 1256-1262, 1965.
3. Stander, G.J. and Van Vuuren, L.R.J., "The Reclamation of Potable Water
from Wastewater," JWPCF, Vol. 41, No. 3, pp 355-367, 1969.
4. Cillie, G.G., Van Vuuren, L.R.J., Stander, G.J. and Kolbe, F.F., "The
Reclamation of Sewage Effluent for Domestic Use," 3rd Annual Conference
IAWPR, Munich, 1966.
5. Van Vuuren, L.R.J., Meiring, P.G.J., Henzen, M.R. and Kolbe, F.F., "The
Floatation of Algae in Water Reclamation," Int. 3, Air Water Pollution, Vol. 9,
pp 823-832, 1965.
6. Dryden, Frank D. and Stern, Gerald, "Renovated Waste Water Creates
Recreational Lake," Environmental Science and Technology. Vol. 2, No. 4,
pp 268-278, April 1968.
7. Beck, Louis A., "Nitrogen Removal from Agricultural Wastewater." Advanced
Waste Treatment Seminar. San Francisco, California, October 1970.
8. Golueke, C. G. and Oswald, W.J., "Harvesting and Processing Sewage
Grown Planktonic Algae," JWPCF, Vol. 37, No. 4, pp 471-498, April 1965.
-------
APPENDIX I:
DESIGN CRITERIA FOR TERTIARY FACILITIES AT STOCKTON
The existing Stockton plant consists of the following sequence of processes:
preliminary treatment, primary sedimentation, trickling filters, secondary sedi-
mentation, tertiary ponds, and effluent chlorination. Solids treatment is by
digestion and sludge lagoons.
Improvements will be made to all treatment stages. Data summarized here
are concerned only with upgrading of the tertiary ponds by algae removal.
Design data for the existing ponds, the algal removal facility, and chlorine
contact channel are shown in Table 2, while the process flow diagram is shown
in Fig. 5.
The chlorine contact channel is a multipurpose unit serving for chlorine con-
tact, backwash water storage, ammonia removal by superchlorination, dechlorination
with sulfur dioxide, and post-aeration.
The original cost estimate for the tertiary facilities (excluding the ponds) was
$3,600,000 (December 1972 prices), but was for a facility using sedimentation
rather than flotation. The revised design required smaller tanks: four 85 ft. dia-
meter flotation tanks with 7 ft. side water depth instead of four 130 ft. diameter
sedimentation tanks with 20 ft. side water depths. A revised cost estimate has
not been completed by November 1, 1972.
Annual operating costs of the tertiary facility (excl. ponds) are estimated at
$40 to $45/MG, based on year-round operation of the tertiary facilities (1972 costs
prorated to design year flows).
-------
Table 2. Design Data for Stockton Tertiary Facilities
Component
Tertiary ponds (existing)
Number
Area, net water surface, acres
Volume, mg
Loading during noncanning season
BOD total, 1000 Ibs/day
BOD Ib/surface acre/day
Loading during canning season
BOD total, 1000 Ibs/day
BOD Ib/surface acre/day
Detention during noncanning season, days
Detention during canning season, days
Circulation pumping units
Number
Capacity, each, mgd
Circulation ratio (at peak)
Flotation tanks (new)
Peak weekly flow rate, mgd
Number
Diameter, ft
Sidewater depth, ft
Surface loading rate gallons/sq ft/day
(incl. pressurized flow)
Solids loading rate, Ibs/sq ft/day
Pressurized flow, percentage of total
Pressurized, psig
Alum dosage, mg/1, peak rate
Polymer dosage, mg/1, peak rate
Acid dosage, peak, ml/1
Assumed float concentration, percent
Assumed float weight, Ibs/cu ft
Float collection arms , number each tank
Float collection troughs , number each tank
Peak float discharge rate, gpm
Quantity
4(4)
630
1,320
3.2
5
57
90
57
23
3
65
3.4
55
4
85
7
2.7
6.8
26
40
250
1
3
3
41
4
2
600
-------
FROM POND
TO PONDS
TO SOLIDS
DISPOSAL
SYSTEM
I
TO PONDS
BACKWASH
WATER
PUMPS
•AIR
CHLORINE
CONTACT
CHANNEL
TO POND
SYSTEM
Fig. 5 Tertiary Algal Removal Facility
-------
Table 2 (cont'd)
Component
Quantity
Filters (new)
Numbei
Area per filter (bifurcated), sq ft
Design filtration rates, gpm/sq ft
All filters in service
One filter backwashing
Anthracite coal
Depth, ft
Effective size, mm
Sand
Depth, ft
Effective size, mm
Pea gravel
Depth, ft
Backwash
Air
Rate, cfm/sq ft
Pressure, psig
Water
Wash rate, gpm/sq ft
Minimum
Maximum
Chlorine contact canal (new)
Length, ft
Depth, ft
Average width, ft
Residence time, peak flow, min
Chlorine disinfection dosage rate, mg/1
Chlorine for NHj removal, Ibs C\2 Per l
ammonia (NH )
Sulphur dioxide dosage, peak, mg/1
Reoxygenation, mg/1
4
1,700
5.6
7.4
2.4-4.8
1.5
0.8-1.0
0.62
4
5
10
20
1,000
6
27
30
15
12
5
5
-------
COUNTY SANITATION DISTRICTS
OP
Los ANGELES COUNTY
2O2O BEVERLY BOULEVARD
Los ANGELES. CALIFORNIA 9OO57
JOHN D. PARKHURST TBLEPHONS
CHIEF ENGINEER AND GENERAL MANAGER (213) 484-137O
13 October 1972
Denny Parker
Brown and Caldwell
66 Mint Street
San Francisco, California 94103
Dear Mr. Parker:
This letter is in reply to your phone request for data concerning the
Lancaster Tertiary Treatment Plant.
Construction Cost: $243,000
Design Flow: 0.5 MOD
Processes:
Coagulation
Sedimentation
Filtration
Chlorination
Operation Costs: 70-71 71-72
(11/23/70 to 6/30/71) (7/1/71 to 6/30/72)
Cost of Operation $19,033 $28,273
Cost per MG Treated 256 199
Cost per MG Delivered 325 238
Total Water Treated(MG) 74 142
Total Water Delivered(MG) 59 119
Overall Plant Efficiency(%) 79 83
Also enclosed is a Monthly Summary of Operation Report for August 1972.
If you desire any other information do not hesitate to contact the
Districts.
Sincerely yours,
John D. Parkhurst
Chief Engineer & General Manager
jpervisor
Monitoring" Section
Technical Services Department
JDP:KP:vic
Encl.
-------
APPENDIX II:
LANCASTER TERTIARY TREATMENT PLANT
-------
PROCESS FLOW DIAGRAM
FLOW = 500,000 GALLONS PER DAY
FLOCCULATION
CHAMBER
(20 MIN )
SEDIMENTATION
(25HRS.)
300mg/l AI2(S04)3
DUAL MEDIA
GRAVITY
FILTER
CHEMICAL COAGULANT ADDITION
CHLORINE
CONTACT
BASIN
FILTER BACKWASH AND
SLUDGE RETURNED
TO TREATMENT PLANT
DISCHARGE TO
RECREATION
LAKES
15 mg/l
26 ACRE
AQUATIC
RECREATION
LAKES
-------
ANTELOPE
VALLEY TERTIARY TREATMENT
COUNTY SANITATION DISTRICTS
OF LOS ANGELES COUNTY. CALIF
PLANT
MONTHLY SUMMARY OF OPERATION
UJ
o
T
4
5
r
B*
"«•
•t'f
•\
uJL
.21
.20_
.10
.10
*'j|
6.50
ALKA-
LINITY
AS
CoCOj
INF
mo/1
II
ISA
'"..
Tso~
262 '
248
230
250
»o
SUSP
SOLIDS
INF
m,/l_
1»
106
iir
'182
1B6
184
Tsa —
151
120
128
110
11C
111
lit
ill
11C
114
111
(04
114
AMMO-
NIA
AS
NH3
INF
"Tp"
— 5—
6
0
a
TOTAL
PHOSPHATE
AS PGA1
INF
mg/l
l«
JJ.RI
J2.06
-»
4
3
J
EFF
-1-f-
f. 81 1 "
l.l^O
1.17
.16
1C. BO
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;
J
\
1
a
2
i
2
1. 14
ii .
• V
.1
.4'
1.8:
I 1
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±L *
.1 1
21.00
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it
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