United States
Environmental Protection
Agency
Municipal Environmental Research EPA 600 2 79 075
Laboratory July 1979
Cincinnati OH 45268
Research and Development
Nitrogen and
Phosphorus
Control by Two
Facilities in Florida
-------
RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into nine series. These nine broad cate-
gories were established to facilitate further development and application of en-
vironmental technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The nine series are:
1 Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
6. Scientific and Technical Assessment Reports (STAR)
7 Interagency Energy-Environment Research and Development
8. "Special" Reports
9. Miscellaneous Reports
This report has been assigned to the ENVIRONMENTAL PROTECTION TECH-
NOLOGY series. This series describes research performed to develop and dem-
onstrate instrumentation, equipment, and methodology to repair or prevent en-
vironmental degradation from point and non-point sources of pollution. This work
provides the new or improved technology required for the control and treatment
of pollution sources to meet environmental quality standards.
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.
-------
EPA-600/2-79-075
July 1979
NITROGEN AND PHOSPHORUS CONTROL
BY TWO FACILITIES IN FLORIDA
by
Tom Comfort
Hillsborough County Utilities Department
Tampa, Florida 33601
and
Larry Good
Florida Cities Water Company
Sarasota, Florida 33581
Grant No. 805005
Project Officer
E. F. Earth
Wastewater Research Division
Municipal Environmental Research Laboratory
Cincinnati, Ohio 45268
MUNICIPAL ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CINCINNATI, OHIO 45268
-------
DISCLAIMER
This report has been reviewed by the Municipal Environmental Research
Laboratory, U.S. Environmental Protection Agency, and approved for publica-
tion. Approval does not signify that the contents necessarily reflect the
views and policies of the U.S. Environmental Protection Agency, nor does
mention of trade names or commercial products constitute endorsement or
recommendation for use.
11
-------
FOREWORD
The Environmental Protection Agency was created because of increasing
public and government concern about the dangers of pollution to the health
and welfare of the American people. The complexity of that environment and
the interplay between its components require a concentrated and integrated
attack on the problem.
Research and development is that necessary first step in problem solu-
tion and it involves defining the problem, measuring its impact, and
searching for solutions. The Municipal Environmental Research Laboratory
develops new and improved technology and systems for the prevention, treat-
ment, and management of wastewater and solid and hazardous waste pollutant
discharges from municipal and community sources, for the preservation and
treatment of public drinking water supplies, and to minimize the adverse
economic, social, health, and aesthetic efforts of pollution. This publica-
tion is one of the products of that research; a most vital communications
link between the researcher and the user community.
This report describes the operational and analytical considerations
necessary for municipal wastewater treatment facilities that are required
to produce high quality effluents.
Francis T. Mayo
Director
Municipal Environmental Research
Laboratory
111
-------
ABSTRACT
Municipal wastewater treatment plants employing multi-stage processes
can be operated to consistently produce high quality final effluents.
Data for both the 11,400 m /d Hillsborough County, Florida and the
6,813 m3/d Florida Cities Water Company facilities are presented in tabular
and graphic form.
These data show that both utilities can achieve the stringent State of
Florida effluent limitations. These limitations, for selected sites in the
State, require that the effluent shall not contain more than 5 mg/1 five
day Biochemical Oxygen Demand, 5 mg/1 suspended solids, 3 mg/1 total nitrogen
and 1 mg/1 total phosphorus.
This report was submitted in fulfillment of Grant No. 805005 by
Hillsborough County under partial sponsorship by the United States Environ-
mental Protection Agency. This report covers a period from February 1976 to
December 1978 and work was completed January 1979.
IV
-------
CONTENTS
FOREWORD iii
ABSTRACT iv
FIGURES , vi
TABLES viii
1. Introduction 1
2. Conclusions and Recommendations 3
3. River Oaks Facility 4
4. Gulf Gate Facility 25
v
-------
FIGURES
Number , Page
1 Location of River Oaks Facility 5
2 Flow Diagram of River Oaks 6
3 First Stage Carbonaceous Reactor 10
4 Sodium Aluminate Storage Tank 11
5 Influent to Denitrification Reactor 13
6 Methanol Tank Before Insulation 14
7 Insulated Methanol Tank 15
8 Hillsborough County Laboratory 18
9 Sludge Truck Transport to Orange Grove 19
10 Total Nitrogen Content of River Oaks Final Effluent. ..... 23
11 Total Phosphorus Content of River Oaks Final Effluent 24
12 Location of Company Treatment Plants 26
13 Billing and Records Office 27
14 Gulf Gate Flow Diagram 29
15 Equalization Tank 30
16 First Stage Carbonaceous Reactors 31
17 Denitrification Facilities 32
18 Rotating Disc Surface 33
19 Gravity Dual Media Filters . . 34
20 Filtered Final Effluent 35
VI
-------
FIGURES (continued)
Number Page
21 Control Laboratory 37
22 Aerobically Digested Sludge Transport 39
,•
23 Total Nitrogen Content of Gulf Gate Final Effluent 45
24 Total Phosphorus Content of Gulf Gate Final Effluent. ... 46
Vii
-------
TABLES
Number Page
1 Design Values for Major Components of the River Oaks Plant. . . 7
2 Hillsborough County Utilities Sampling Schedules 16
3 River Oaks Plant Efficiency, Monthly Average Values - 1976. . . 20
4 River Oaks Plant Efficiency, Monthly Average Values - 1977. . . 21
5 River Oaks Plant Efficiency, Monthly Average Values - 1978. . . 22
6 Sampling Schedule of Gulf Gate Plant 36
7 Gulf Gate Plant - Final Filters, Unit Removals 41
8 Gulf Gate Plant - Final Filters, Unit Removals 42
9 Gulf Gate Plant Efficiency, Monthly Average Values 43
vni
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SECTION 1
INTRODUCTION
Designated areas of the State of Florida are subject to wastewater eff-
luent discharge standards of five milligrams per liter 6005, five milligrams
per liter suspended solids, three milligrams per liter of total nitrogen and
one milligram per liter total phosphorus, depending on the population density
and receiving water quality.
These water quality standards are established under the State of Florida
Pollution of Waters Act referred to as the Wilson-Grizzle Act. It was
enacted in 1970 under Chapter 403.086 of the Florida Statutes and amended by
Chapter 72-58 of the Laws of Florida in 1972 and Chapter 17-3.04, Florida
Administrative Code.
The Federal Environmental Protection Agency permit requirements as set
forth by Region IV limit effluent residuals to 8 mg/1 BOD, 8 mg/1 suspended
solids, 5 mg/1 total nitrogen and 2 mg/1 total phosphorus.
Florida's second largest industry, tourism, and other water related
industries are dependent upon the availability of safe, clean waters. Through
the enactment of the Wilson-Grizzle Bill, the State's greatest natural
resource, its costal waters, will be protected from degradation.
The River Oaks treatment facility, operated by the Hillsborough County
Utilities Department, and the two treatment facilities known as Gulf Gate and
South Gate (Sarasota County) operated by the Florida Cities Water Company
are subject to the Wilson-Grizzle effluent standards.
Florida rules define secondary treatment as having a minimum efficiency
of 90 percent. Sarasota County also has an Ordinance which demands 98 per-
cent removal of BODg and suspended solids.
Chapter 17-3.04 does provide: (3) Alternate effluent disposal is a
minimum of secondary treatment (90 percent) followed by an effluent disposal
system approved by the Department which will prevent any effluent from being
discharged to the surface waters of the State. Such disposal may include
land disposal, deep injection wells, or combinations thereof, or other
methods approved by the Department.
These facilities have been in operation for several years and have
demonstrated the feasibility of controlling both nitrogen and phosphorus in
municipal effluents. This report will concern the operational and analytical
considerations involved with the daily routine for the River Oaks and Gulf
1
-------
Gate facilities. Since the River Oaks and Gulf Gate facilities are required
to meet the same effluent limitations, but employ different processes,
comparative data should be of interest to designers, operators and regulatory
personnel.
-------
SECTION 2
CONCLUSIONS AND RECOMMENDATIONS
CONCLUSIONS
1. This study has shown that multi-stage wastewater treatment systems
can be very efficient for the control of BOD , SS, TN and TP.
2. Combined chemical-biological processes can be managed by plant
operators.
3. Combined chemical-biological processes depend upon adequate
laboratory control.
4. Sludges generated by these processes can be applied to agricultural
land.
RECOMMENDATIONS
1. Efficiency data should be routinely displayed as frequency
distribution plots so that variability of effluent composition can
be documented.
2. Effluent limitations should be based on probability of occurrence
rather than "never to exceed values", in the case of general
pollutants such as nutrients. Toxic residuals however may have
to be restricted to absolute values.
-------
SECTION 3
RIVER OAKS FACILITY, HILLSBOROUGH COUNTY
The plant is located in the Northwest area of Hillsborough County on the
outskirts of the City of Tampa as shown in Figure 1. The receiving water is
a man-made canal which is subject to tidal action, and empties into Old
Tampa Bay.
3
The plant was designed to treat 11,400 m /d O3 mgd) with provisions
for future expansion to 34,000 m3/d (9 mgd). Initial design was for a
complete mix two sludge nitrification system, followed by deep bed, dual
media, down flow filters for denitrification and filtration.
Figure 2 is a schematic layout of the River Oaks facility showing the
major unit processes and initial points of chemical additions for control of
nitrogen and phosphorus.
Table 1 gives the design valves of the major unit processes at plant
hydraulic capacity of 34,000 m^/d and a process design of 11,400 m^/d.
Operation of the River Oaks Plant
Due to an unexpected economic recession, the projected growth rate in
the area did not occur and the hydraulic loading on the facility was less
than 3,785 m /d for several years. During this time the nitrification stage
was bypassed and the carbonaceous reactor was operated as an extended aera-
tion process to provide nitrified effluent for the dentrification units.
Figure 3 is a view of the carbonaceous reactor. Considerable equipment and
operational changes were made during this time to optimize phosphorus and
nitrogen removal.
The best dosing point for sodium aluminate addition proved to be after
the grit chamber and just before the inlet to the carbonaceous reactor. -A
1.2:1 mole ratio of A1:P at this point provided the most efficient and eco-
nomical dose to achieve the 1 mg/1 effluent total phosphorus limitation.
Figure 4 shows the sodium aluminate storage tank and dual metering pumps for
addition of the chemical.
Continual problems with the denitrification filters plagued operation
due to the fact that the filters would not accept the design application rate
without rapid headless and consequent frequent backwashing. Excessive slime
growth, inorganic aluminum percipitates and media destratification were all
evaluated as probable causes. Eventually the filters could be kept on line
-------
Y T~a->s~^*~ T-"™
_J -.-.-, 3 ff*~^ --•-- 1 ~
Figure 1. Location o£ River Oaks Facility
-------
fWER OAKS ADVANCED WASTE TREATMENT PLANT
o\
FINAL
EFFLUENT
CONTACT
J
(t
s „ 1
0| S
t- Z
1 2
T|REA™T,ON *
CIIU'OER
»ACKV«SH
RETURN
TANK
-^
\
^
DtNIIF- * 1
FILTERS * 2
» 3
*«
DACKWASH RETURN
Figure 2. Flow Diagram of River Oaks
-------
TABLE 1. Design Values For Major Components of
The River Oaks Plant
COMPONENTS
Flow Meters Magnetic
Influent
Return Sludge (Carbon Cycle)
Return Sludge (Nitrogen Cycle)
Nitrogen Cycle Spikeline (Carbon
Source)
Denitrification Influent
Grit Removal
DESIGN.
(at 11",400 in /d)
Cyclone Degritter
Bar Rack (Hand cleaned)
Comminutor
Phosphorus Removal
56 m (15,000 gal) tank (storage)
Chemical Feed Pump (1)
Chemical Feed Pumps (2)
Denitrification Carbon Source
38 m (10,000 gal) tank (storage)
500 gallon tank (day)
Chemical Feed Pump
Chemical Feed Pump
Aeration Tank (Carbonaceous)
Diameter
Capacity
Mechanical Aerators
Aerator Horsepower
Detention Time
Return Sludge Rate
1
1
1
1
1
0.3 m
34,000 nu/d
34,000 m /d
0.02 1/s
0.2 1/s
1
1
0.005 1/s
0.03 1/s
(12 in.)
(9 mgd)
(9 mgd)
(17 gal/hr)
(175 gal/hr) each
(5 gal/hr)
(27 gal/hr)
(105 ft x 12 ft SWD)
(778,912 gal)
(60 hp)
32 m x 3.6 m
2,950 m
3
45 kW
6.2 hrs
6800-8700 m /d (1.8 - 2.3 mgd)
-------
TABLE 1. (continued) - Design Values for Major Components of the River Oaks
Plant
COMPONENTS
Aeration Tank (Nitrification)
Diameter
Capacity
Mechanical Aerators
Horsepower
Diffused Air Blowers
Capacity
Detention Time
Return Sludge Rate
18 m x 3.6 m
960 m
1
17 kW
3 3
0.5 m /s at
34 kn/m
2 hr
DESIGN ,
(at 11,400 m /d)
(60 ft x 12 ft SWD)
(253,791 gal)
(25 hp)
(1042 cu ft/min at
5 psi)
6800-8700 m /d (1.8 - 2.3 mgd)
Clarifiers (Nitrification § Carbonaceous)
Diameter
Capacity
Surface Settling Rate
Detention Time
Wier Overflow Rate
Aerobic Digesters
Number of Units
Diameter
Capacity
Aerators (Mechanical)
Horsepower
Sludge Handling
Sludge Thickening Tank
Diameter
Capacity
Sludge Holding Tank
Diameter
Capacity
Sludge Disposal (Contract Hauling)
Chlorine Contact Tank
Number of Rectangular Units
Length
Width
Depth
Total Volume
27 m x,3.6 m
2160 m
19,190 1/m
4.56 hr
134 m /m/d
2
23 m x 3.6 m
1,500 m
2
30 kW
1
10 m x 3 m
270 m
1
9 m x,7 m
480 m
(90 ft x 12 ft SWD)
(571,030 gal)
(471 gal/sq ft)
(10,600 gal/lin ft/day)
(75 ft x 12 ft SWD)
(53,105 ft (3.5 ftV
capita))
(40 hp)
(34 ft x 10.5 SWD)
(71,272 gal)
(30 ft x 24 ft SWD)
(126,831 gal)
1
17 m
14.5 m
1.5 m
374 m
(55.6 ft)
(48 ft)
(5 ft)
(99,813 gal)
-------
TABLE 1. (continued) - Design Values for Major Components of the River Oaks
Plant
COMPONENTS
Denitrification Filters (Dual Media)
Number of Units
Rectangular Units
Denitrification (Anthracite)
Polishing (Sand)
Support (gravel)
Surface Loading
Contact Wet Time
Reaeration (Mechanical Aerator)
DESIGN
(at 11,400 m /d)
7.6 m x 3 m (25 ft L x 10 ft W
x 4 m x 13 ft)
0.9 m (36 in.)
0.5 m (18 in.)
0.3 m 7 (12 in.) 2
1.4 - 4.1 1/m (2.0 - 6.0 gal/min/ft )
/S
5-10 min
3.7 kW 1 - (5 hp)
-------
Figure 3. First Stage Carbonaceous Reactor
-------
Figure 4. Sodium Aluminate Storage Tank
-------
a reasonable length of time by maintaining a 1.5 mg/1 chlorine residual in
the backwash chamber and releasing nitrogen gas with periodic short pulses
of air and backwash through the underdrain system. Figure 5 shows the in-
fluent end of the down flow dual media denitrification filters.
Careful monitoring of the methanol fed for denitrification showed that
there was an 11 percent loss of methanol during storage due to evaporation.
The original storage tank was not insulated. Foamed, in-place insulation
was applied to the storage tank and the day-tank used for daily dosage con-
trol. Figures 6 and 7 show these tanks before .and after foam insulation.
The insulation was effective in greatly reducing evaporation losses.
Gradually population increased and the County purchased several small
private utility package plants which were abandoned and the flows diverted
to the River Oaks Plant. When flow increased over the 3,785 m^/d mark, the
nitrification system was placed into operation.
Staff Required for River Oaks Operation
1 - Chief Operator - 40 hours per week
3 - Lead Operators - 120 hours per week
3 - Shift Operators - 120 hours per week
2 - Relief Operators - 80 hours per week
2 - Laboratory Tech-
nicians 80 hours per week
440 Total Manhours per week
Chemicals Required for River Oaks Operation
Sodium aluminate - 1.2:1 A1:P weight ratio
Methanol - 3:1 methanol to nitrate nitrogen weight ratio
Polymer - for sludge thickening
Chlorine for disinfection - 9 mg/1
Analytical Program and Sampling Schedule
The laboratory for the analysis of the River Oaks Advanced Wastewater
Treatment Plant is located approximately one block away. Samples composited
for 24 hours are collected by four automatic samplers and analyzed the
following day. To meet minimum State requirements, analysis for total
nitrogen, total phosphorus, suspended solids, BOD and fecal coliform are
required on the chlorinated effluent only. Analysis on the effluent alone
would not provide the data necessary for process control. Therefore, four
sample points were chosen throughout the treatment process for control. The
sample locations are: the influent before any chemical addition or treatment,
the carbon cycle clarifier effluent, the nitrogen cycle clarifier effluent
and the chlorinated effluent. Table 2 shows the sampling and analysis
schedule.
12
-------
•
Figure 5. Influent to Denitrification Reactor
-------
Figure 6. Methanol Tank Before Insulation
-------
[\
FLAMMABLE
MATERIAL
Figure 7. Insulated Methanol Tank
-------
TABLE 2. Hillsborough County Utilities Sampling Schedules
RAW
ANALYSIS WASTEWATER
BOD5
ss
TKN
N03-N+N02-N
NH3-N
P Total
D.O.
pH
Alkalinity
COD
Fecal Coliform
5C
1C
5C
X
5C
5C
7G
7G
7C+G
5C
X
CARBONACEOUS NITROGENOUS
CLARIFIER CLARIFIER
EFFLUENT EFFLUENT
5C
7C
5C
5C
5C
5C
7G
7G
7C+G
5C
X
1 = once per week
2 = twice per week
5 = five times per week
7 = seven times per week
8 = once per month
5C
7C
5C
5C
5C
5C
7G
7G
7C+G
5C
X
x = no sample
C = composite samples
G = grab samples
CHLORINATED
EFFLUENT
EFFLUENT
5C
7C
7C
7C
X
5C
7G
7G
7C+G
5C
2G
16
-------
In order to better compare the data from the Gulf Gate treatment plant
with the River Oaks Plant, four portable automatic samplers were purchased
and set at comparable points of the treatment process at Gulf Gate for
sampling. Once per week the four samples were split between the two labora-
tories for comparative analytical results. Figure 8 is a view of the
Hillsborough County laboratory.
Sludge Production at River Oaks
About 25 m3 of waste sludge is produced for each 3,785 m3 of wastewater
treated (6,800 gal/million gallons). This sludge is aerobically digested
in two-1500 m3 digesters utilizing floating mechanical aerators of 30 kW
(40 hp) each. Loading rates dictated an average of 30 days detention per
digester. After aerobic digestion, Nalco #7120 polymer is added to thicken
the digested sludge from two percent solids to 3.2 percent solids. The sludge
is then hauled by truck to a local orange grove for land spreading. Figure 9
shows the application of the digested sludge in the grove.
Efficiency of the River Oaks Multi-Stage Treatment
Tables 3, 4, and 5 show the overall efficiency of the facility in
removing BOD5, SS, TN (total nitrogen) and TP (total phosphorus). The tables
cover the period 1976 to 1978. As the daily flow increased from less than
3,785 m3/d (1 mgd) in 1976 to near 11,400 m3/d (3 mgd) in 1978 there was no
reduction in efficiency for removal of pollutants.
Figure 10 is a plot of 145 daily analyses for total nitrogen during the
first six months of 1978 reported in Table 2. The data were arrayed in 0.1
mg/1 increments and the frequency of occurrence plotted on logarithmic
probability paper. Results show that 50 percent of the samples contained
1.5 mg/1 TN, or less; and the effluent limitation of 3 mg/1 TN was achieved
on 90 percent of the samples.
This same technique was used to plot the total phosphorus values for
the first six months of 1978 analyses. Figure 11 shows that 50 percent of
the 155 data points were 0.7 mg/1 TP, or less; and the effluent standard of
1 mg/1 TP was achieved on 66 percent of the samples. Efficiency improved
during the latter six months of operation.
Calculation of the spread factor, by comparing the mean value with one
standard deviation, for each of the above data sets shows that the process
control for TP is more variable than control of TN. Tables 3, 4, and 5 show
that River Oaks more consistently meets the total nitrogen effluent limita-
tion than the total phosphorus limitation on a monthly average basis.
17
-------
POLLUTION
ISA
WRTYWORD
Figure 8. Hillsborough County Laboratory
-------
-
Figure 9. Sludge Truck Transport to Orange Grove
-------
TABLE 3. River Oaks Plant Efficiency, Monthly Average Values
K)
O
YEAR
1976
January
February
March
April
May
June
July
August
September
October
November
December
ANALYSIS, mg/1
BOD SS
Inf. Eff. Inf. Eff.
238
212
208
204
193
207
234
188
170
198
193
238
33
45
27
17
5
6
3
5
2
2
6
4
166
155
163
155
149
219
277
210
157
205
233
191
3
4
4
3
2
5
4
4
2
2
1.6
2
FINAL EFFLUENT
TOTAL N
TKN
0.6
0.6
0.6
0.6
0.6
0.6
0.6
0.6
0.6
0.6
0.6
0.6
NO -N*
X
5.5
0.8
0.7
1.2
1.5
1.2
0.6
1.2
0.8
1.5
0.5
1.2
SOL. P TP
0.9
0.9
0.9
0.7
0.9
1.9
2.0
1.0
0.8
1.2
1.0 0.8
0.6
DAILY
FLOW
mgd**
1.1
1.1
1.1
1.0
1.1
1.1
1.0
0.9
1.0
0.9
0.8
0.8
**mgd x 3,785 = m /d
*NO -N = N00-N+NO,-N
x 23
-------
TABLE 4. River Oaks Plant Efficiency, Monthly Average Values
YEAR
1977
January
February
March
April
May
June
July
August
September
October
November
December
ANALYSIS, mg/1
BOD SS
Inf. Eff. Inf. Eff.
237
238
245
258
249
263
207
197
200
242
261
240
4.0
5.0
4.0
1.6
2.3
2.6
2.0
0.6
1.6
0.9
1.4
2.0
168
235
220
193
172
197
153
196
134
175
234
210
1.0
2.6
1.9
1.4
1.6
1.2
1.0
1.1
1.2
1.4
0.9
1.0
FINAL EFFLUENT
TOTAL N
TKN
0.6
0.6
0.6
0.6
0.7
0.6
0.6
1.6
1.1
1.3
1.2
0.9
NO -N*
x
1.
1.
0.
1.
1.
0.
0.
1.
1.
2.
0.
0.
5
8
8
2
2
3
1
3
2
1
8
6
SOL.
0.
0.
0.
0.
0.
0.
0.
0.
1.
0.
0.
0.
P
5
7
3
7
7
8
8
5
1
7
8
5
TP
0.8
0.9
0.4
0.9
0.9
0.9
0.9
0.6
1.3
1.2
1.4
0.6
DAILY
FLOW
mgd**
1.0
1.3
1.3
1.2
1.2
1.3
1.5
2.0
2.3
2.1
2.1
2.1
**mgd x 3,785 = m /d
*NO -N = NO^-N+NO_-N
x 23
-------
TABLE 5. River Oaks Plant Efficiency, Monthly Average Values
N)
YEAR
1978
January
February
March
April
May
June
July
August
September
October
November
December
ANALYSIS, mg/1
BOD SS
Inf. 5Eff. Inf. Eff.
239
205
207
250
206
218
238
229
207
216
216
183
3
2
2
3
1
1
1
1
1
2
1
1
212
190
212
239
214
229
293
246
162
177
181
166
1
1
1
1
2
1
3
2
1
2
4
3
FINAL EFFLUENT
TOTAL N
TKN
1.2
1.1
1.2
1.1
1.1
1.0
2.1
1.2
2.7
2.6
1.6
2.1
NO
X
0
0
1
0
0
0
0
0
0
0
0
0
-N*
.1
.7
.5
.7
.6
.1
.1
.1
.2
.7
.5
.5
SOL
1
0
0
0
1
0
0
0
0
0
0
0
. p
.3
.9
.4
.9
.0
.8
.5
.3
.4
.6
.5
.7
TP
1.2
1.1
0.5
1.0
1.6
0.9
0.6
0.4
0.5
0.7
0.8
0.8
DAILY
FLOW
mgd**
2.2
2.5
2.3
2.0
2.3
2.1
2.3
2.4
2.6
2.9
2.8
2.9
**mgd x 3,785 = m /d
*NO -N = NO_-N+NO_-N
x 23
-------
K)
5.0
4.0
^3.0
E
§2.0
o>
o
* 1.0
o
0.5-
Spread Factor = 1.7
River Oaks
Effluent
Standard
Mean
10 30 50 70
Percent of Observations
90
98
Figure 10. Total Nitrogen Content of River Oaks Final Effluent
-------
N>
5.0
4.0
3.0
2.0
O>
S 1.0
o
JC
a
(A
o
0- 0.5
"5
0.1
Spread Factor = 2.4
River Oaks
Effluent
Standard
Mean
90
98
2 5 10 30 50 70
Percent of Observations
Figure 11. Total Phosphorus Content of River Oaks Final Effluent
-------
SECTION 4
GULF GATE FACILITY, SARASOTA COUNTY
The Gulf Gate area utility was purchased by Florida Cities Water
Company in 1965 and provides water and wastewater utility services. Figure
12 shows the location of the two plants owned by the Company in Sarasota
County. The present facilities, designed to meet the AWT standards, were
completed in early 1975 after being judged by Company management as being the
most practical and economical process available to achieve the desired
results. The billing and records office of the Company is shown on Figure 13.
Facilities Design
NOMINAL CAPACITY 6,813 m3 (1.8 mgd)
1. Grit removal is sized to remove + 150 mesh grit.
2. Equalization tank is a 24m (80 ft) diameter tank having a capacity
of 2,700 m3 (715,000 gal.) with a turbine aerator and peripheral
diffusers.
3. Aeration Tanks - There are 4 tanks having a total volume necessary to
permit a BOD loading of 961 g/m3 (60 lb/1000 ft ) at design flow.
Each tank is provided with turbine aerators.
4. Intermediate Clarifiers - There are 3 designed for 2.2 hr detention
and 35 m3/m2/d (850 gal/ft /d).
2
5. Rotating Disc Nitrification - There are 8 shafts rated at 9290 m „
(100,000 ft2) each, for a hydraulic loading of 0.1 m3/m2/d (2.2 gpd/ft )
6. Suspended Growth Denitrification - There are 3 mixing basins of equal
volume with a total detention time of 2.5 hr. Each basin is equipped
with a submerged mixer to keep the denitrification mixed liquor in
suspension. Methanol is added for controlling the denitrification
reaction.
7. Purge tank to blow out nitrogen operates at one minute rapid mix and
5 minutes high rate air purge.
8. Final Clarifiers - There are 2 with 2.5 hr detention time and a surface
loading of 30 m /m2/d (750 gpd/ft2).
25
-------
FLORIDA CITIES WATER CO, L/S MAP
Figure 12. Location of Company Treatment Plants
26
-------
'
I
Figure 13. Billing and Records Office
-------
9. Filters - There are 4 gravity/sand/anthracite filters with air2surface
wash. Surfa.ce loading is 2.3 H/jtT/s (3.5 gpm/ft2) or 3.3 £/m /s
(5.0 gpm/ft ) with one filter being backwashed.
10. Aerobic Sludge Digesters - There are 2 rectangular tanks with coarse
air diffusion having a capacity of 0.06 m (2 ft3) per capita. An
air rate of 0.3 Jl/m /s (20 cfm/1000 ft ) is applied.
Figure 14 shows a schematic flow diagram of the Gulf Gate Plant. The
major installed unit processes are shown in a series of pictures. Figure 15
is the 2,700 m3 equilization tank. This tank is considered essential by the
operational staff since it allows the following processes to be operated at
constant flow. This is particularly important for chemical dosages and
final filter and disinfection control. Figure 16 shows two of the first
stage aeration tanks with turbine aerators. Figure .,17 shows the second
stage rotating discs on the left, suspended growth denitrification reactor
in the middle background, nitrogen gas purge in the left foreground, and
the final clarifiers in the right foreground. Figure 18 is a close-up view
of the rotating disc inside the plastic shell. Since the discs receive a
very low BODs load from the first stage carbonaceous reactor, only a very
thin film of biological growth occurs on the discs. There is no intermediate
settling between the rotating discs and the denitrification reactor because
these second stage discs do not slough solids. Figure 19 is a top view of
the gravity dual-media filters. Figure 20 shows a one liter beaker of the
filtered final effluent; the clarity and sparkle are characteristic of daily
effluent production.
Analytical and Sampling
Two composite samples are taken daily. One is taken as a raw sample
ahead of the grit chamber and the other is taken from the effluent in the
tank located ahead of chlorination. Automatic samplers take a 200 ml
sample every 40 minutes totaling 7,200 ml per day. A sampling and analysis
schedule is shown in Table 6.
Plant Operation
1. An operator is on-duty from 7:00 AM to 12:00 Midnight each day. Mainte-
nance and control work are performed by a lead operator and three shift
operators. The laboratory is staffed seven days a week by two labora-
tory technicians. Figure 21 is a view of the wastewater control
laboratory.
2. Operator Training: Operators are encouraged to study and take classes
from schools offering courses leading to certification and licensing.
The company pays tuition and expenses directly related to operator
training programs. On-site instruction and discussion is a daily
occurrence. The Sarasota Division of Florida Cities Water Company
has two "A" Wastewater Operators in staff, one "B" and one "C" Operator.
28
-------
AIR
BLOWERS
METALLIC SAL1
FEED SYSTEM
N)
i ! f
FLUENT COMMNUT.MI _ __™»._.. ^INFLUENT "!£*"
" SUPERNATANT
DIGESTER .
a — ~> &UUHU£HIIUN VrjPIIMD<: mlA
GRIT REMOVAL ^T "UWKa AERATION
C BACKWASH RETURN _
FILTER
CHLORINE POLYMER
FEED SYSTEM FEED SYSTEM
i
BACKWASH |
PUMPS ' 1
®. .. !
i
i FlLTFR !
•NT CHLORINE DUAL MEDIA PUMPS
;,__ ^nLUKiMt nriAuiTY t fr\ , r) AniFirATirtra
CONTACT FILTRATION ^
SLUD6E
K RETURN
WASTE ACTIVATED SLUDGE
< (SLUDGE , • —
* IPUMPS F
, , SUPERNATANT TlM »•
PUMPS V^* AEROBIC
t a -fpS . niKFSTOB
i_
— >
/^K RETURN 8 WASTE
*'" vL/SLUUBE
T PUMPS
!
| METHANOL
. ; FEED SYSTEM
i
FLASH MIX
NITROGEN PURGE
SLUD_GE }
!
SLUDGE PUMPING
STATION
r llFN
nar© — "4-r
\
\
\
Figure 14. Gulf Gate Flow Diagram
-------
i
Figure 15. Equalization Tank
-------
Figure 16. First Stage Carbonaceous Reactors
-------
I J
Figure 17. Denitrification Facilities
-------
I
Figure 18. Rotating Disc Surface
-------
w
i.
Figure 19. Gravity Dual Media Filters
-------
Figure 20. Filtered Final Effluent
.
-------
TABLE 6. Sampling Schedule of Gulf Gate Plant
SOLIDS
Raw Waste
Equal . Tank
M.L. Carbon
BOD5
mg/1
Daily
Comp.
cycle
SS
mg/1
Daily
Comp.
Daily
Spot
Sett.
Solids
Daily
Spot
DO
mg/1
Daily
Spot
Daily
Spot
pH Alk. C12
mg/1 mg/I
Daily
Spot
Daily
Spot
Total Fecal
TKN NO_-N P Coliform
mg/1 mg/1 mg/1 MPN
Inter-Sett.
Eff. Bio Surf
M.L.-Denite
Final-Sett.
Filtered Eff.
Chlorinated Eff.
Aerobic Digester
2-weekly Daily
Spot Spot
Daily Daily
Comp. Comp.
Weekly
Spot
Daily Daily Daily
Spot Spot Spot
Daily
Spot
Daily Daily Daily
Spot Spot Spot
Daily Daily Daily
Spot Spot Spot
Weekly Weekly Weekly
Comp. Comp. Comp.
Daily
Spot
Daily
Spot
-------
I
Figure 21. Control Laboratory
-------
3. Special Operational Techniques: Chemical inventory and feed rates are
checked each day and adjusted as needed. The day shift operator reads
flow totalizer, temperature and rain gauge, collects samples and runs
daily D.O., pH and chlorine residual tests as well as 30 minute settle-
able solids tests on the two mixed liquors. Daily alkalinity tests on
each process indicate the efficiency of nitrification, denitrification
and filtration.
4. Carboncycle sludge is wasted to the digesters each day to maintain a
constant mixed liquor concentration. The return sludge pumps are shut
down for one hour after which 37 m^ (10,000 gal) clarified underflow
is pumped to digesters at 12 £/s (200 gpm) rate which equates to 550 kg
(1220 Ibs) of solids per day.
5. Denitrification sludge return telescopic valves are checked and adjusted
each hour. Sludge from this system is wasted once a week by diverting
return sludge to waste for desired time. Normally 30 m^ (5,000 gal)
per week is sufficient to maintain fairly constant mixed liquor
concentration. This translates to about 160 kg (354 Ibs) of sludge
accumulation per week or 22 kg (50 Ibs) per day from the loss of carbon
cycle solids plus solids made in the nitrification and denitrification
of 68 kg/d (150 Ibs/d).
Sludge Operations and Disposal
From the previous discussion it is known that sludge wasted to digesters
amounts to about 590 kg/d (1300 Ibs/d). By careful wasting the concentration
of solids in the aerobic digesters is maintained at about 1.5%. Since final
disposal of all solids is by hauling and spreading over pasture lands, it is
important that sludge be as concentrated as possible and there be no objec-
tionable odors when sludge is spread. At 1.5% it is necessary that two tank
trailer loads per day or 14 per week at 20 m^ (5,000 gal) be disposed of.
During the rainy season in Florida this method of disposal can become very
difficult to manage. Figure 22 shows the sludge tanker used for hauling.
Special Studies and Problem Solutions
1) The first vexing problem experienced after initial start-up was the
attempt to use ferric chloride to precipitate phosphates. The resulting
turbidity and iron precipitates leaving the plant could not be corrected
through various operating changes or polymer additions. Operating personnel
gave up on trying to use ferric chloride and turned to sodium aluminate.
In order to control colloid loss in the effluent it was necessary to feed
sodium aluminate to the aerator effluent ahead of the settlers.
2) In order to control the amount of solids build-up in the equalization
tank, the plant was designed with an exposed grit chamber. The raw waste-
water was aerated by the grit washer and the neighborhood was exposed to
H_S odors from the treatment plant, along with many irrigation wells in the
neighborhood which also released hLS when sprinkling. The winter of 1975-76
created further strained relations with neighbors due to noise, lights and
38
-------
Figure 22. Aerobically Digested Sludge Transport
-------
H S odors. The H2S was alleviated greatly by a change in water supply.
In June, 1976, the high sulfate well water was replaced by surface water
from the Manatee River. However, complaints continued to be received until
May, 1977 when operating personnel experimented with the use of ferrous
sulfate to precipitate H^S. It was found that the use of ferrous sulfate
added to the influent flow would effectively eliminate the odor and at the
same time react with the phosphate, thus reducing the amount of sodium
aluminate needed. Hence the H S was removed at no extra cost to the Company
and helped our neighborhood relations as well as our relations with the
County Environmental Control staff.
3) Nitrogen purge following the denitrification tanks is absolutely
necessary if sludge is to be settled and returned. The original combined
air piping resulted in decreased air to the purge system when the filters
were air scoured. The nitrogen-gas-lifted sludge covered both final
clarifier surfaces and taxed the scum removal system. Water sprayed over
the surface helped somewhat. But the problem was not solved until the
purge tank was supplied with an independent air supply to constantly and
violently agitate the denitrification mixed liquor. Various arrangements of
air diffusers were also attempted.
Regular wasting of sludge and control of return sludge rate are very
important also.
4) A special study on the effect of the equilization tank was made May 1-
15, 1978. The equilization tank study revealed that adjustment of the gate
regulating the flow to the Parshall flume was necessary to achieve a more
uniform flow from the equalization tank. Table 7 shows the utility of the
equalization tank. Analytical data adjusted for dilution from filter back-
wash indicated that about one third of the BOD,, was removed in the equaliza-
tion tank with average residence time of 7.5 hours. The ferrous iron was
almost completely oxidized as evidenced by the drop in PO. and alkalinity.
There was essentially no loss of TKN.
i
5) A special study on the operation of the final filters was concluded
May 28, 1978. The data from this study is shown in Table 8. The filters
were lightly loaded during the two week period.
Plant Efficiency
Table 9 shows the monthly average data for BOD , SS, total nitrogen
and total phosphorus during the year 1977 with the plant operating at about
48 percent of hydraulic design capacity.
Only the effluent values for phosphorus and nitrogen are shown because
these determinations are not routinely run on influent wastewater. Chemical
dosages for phosphorus and nitrogen control are based on grab samples
obtained at each respective unit process location. Reference to Table 7 can
give an approximation of the concentration of nitrogen and phosphorus that
occurs in the Gulf Gate raw wastewater.
40
-------
TABLE 7. Gulf Gate Plant - Equalization Tank
(24 Hour Composite Samples)
1978
Date
5-1
5-2
5-3
5-4
5-5
5-6
5-7
5-8
5-9
5-10
5-11
5-12
5-13
5-14
Avg.
EQUALIZED
FLOW
mgd*
0.93
.89
.95
.89
.93
.91
.88
.94
.87
.90
.92
.86
.87
.89
.90
BOD
mg/l
Raw
200
230
225
268
288
230
315
306
205
244
268
227
278
326
258
Eq.
145
120
143
132
144
149
184
153
128
133
187
187
138
225
155
SUSPENDED
SOLIDS,
mg/l
Raw
234
222
258
226
218
370
280
462
202
232
312
318
310
302
282
Eq.
220
242
248
254
248
276
256
260
260
248
252
254
242
250
251
ORTHO-PO
mg/l,
(as p)
Raw
' 9.4
9.7
9.3
8.5
8.5
8.5
11.5
11.5
8.2
8.2
8.0
8.5
8.5
8.0
9.0
Eq.
4.7
5.3
5.3
6.0
6.0
5.0
6.0
8.0
5.8
5.5
6.0
5.0
5.0
5.5
5.6
ALKALINITY
mg/l,
(as CaCO )
o
Raw
210
198
190
192
182
187
198
202
220
172
204
190
184
190
194
Eq.
152
162
158
169
154
154
165
164
171
162
173
162
151
161
161
TKN,
mg/l,
(as N)
Raw
—
38.1
38.0
39.2
38.6
40.3
36.4
43.1
39.8
39.8
40.9
41.0
44.8
41.2
40.1
Eq.
—
34.7
35.8
35.3
34.7
37.0
35.8
39.8
35.8
37.0
38.1
38.1
37.0
37.8
36.7
*mgd x 3,785 = m /d
-------
TABLE 8. Gulf Gate Plant - Final Filters, Unit Removals
(24 Hour Composites)
1978
Date
5-15
5-16
5-17
5-18
5-19
5-20
5-21
5-22
5-23
5-24
5-25
5-26
5-27
5-28
Avg.
EQUALIZED
FLOW
mgd
0.86
.88
.88
.88
.91
.89
.87
.93
.96
.84
.86
.88
.68
.89
0.87
BOD
mg/I
Inf.
2.6
2.6
1.3
0.7
1.7
1.3
1.8
5.9
6.4
3.8
1.6
1.1
1.2
0.6
2.3
Eff.
1.0
1.4
1.0
0.4
0.9
0.3
0.6
0.8
0.4
2.5
1.0
0.6
0.8
0.2
0.8
SUSPENDED
SOLIDS,
mg/1
Inf.
1.6
3.6
1.6
1.6
5.2
4.8
4.0
3.6
1.6
3.6
2.0
2.0
1.6
0.8
2.7
Eff.
0.4
0.8
0.4
0.4
0.4
1.2
0.8
0.4
0.4
0.8
0.8
0.4
0.4
0.4
0.6
ALKALINITY
mg/1
(as CaCO )
Inf.
135
128
127
128
126
128
127
126
128
133
127
128
128
134
129
Eff.
136
127
126
125
124
128
127
124
114
129
132
127
127
128
127
TURBIDITY
NTU
Inf.
3.4
2.5
2.7
1.8
1.6
1.5
2.2
3.7
2.9
2.6
1.9
— i
2.0
1.3
2.3
Eff.
1.3
1.1
1.2
1.0
0.9
0.7
0.8
0.9
2.3
1.3
1.0
--
0.8
1.3
1.1
Note: Hydraulic rate 0.9 1/m /S (1.3 gpm/ft2)
Solids loading 0.4 kg/m2/d (0.08 lb/ft2)
-------
TABLE 9. Gulf Gate Plant Efficiency, Monthly Average Values
MONTH
1977
Jan.
Feb.
March
April
May
June
July
Aug.
Sept.
Oct.
Nov.
Dec.
Avg.
Year
*mgd x
FLOW,
mgd*
0.864
0.860
0.853
0.792
0.760
0.783
0.786
0.900
1.134
0.900
0.890
1.001
0.877
3,785 = m3/d
BOD
mg/I
Inf.
177
198
195
190
198
183
217
207
233
272
310
251
219
Eff.
1.3
2.7
2.2
1.0
0.7
0.5
0.6
0.7
1.1
1.0
1.0
1.4
1.2
PERCENT SS ,
REMOVAL mg/1
98
98
98
99
99
99
99
99
99
99
99
99
99
Inf.
278
279
274
288
309
282
338
245
242
293
346
251
285
Eff.
1.1
1.5
1.6
1.7
1.0
1.0
0.5
0.6
0.8
1.0
0.8
0.3
1.0
PERCENT
REMOVAL
99
99
99
99
99
99
99
99
99
99
99
99
99
EFFLUENT
TP
mg/1
0
0
0
0
0
0
0
0
0
0
0
0
0
.7
.8
.5
.8
.6
.5
.4
.8
.6
.5
.4
.2
.6
EFFLUENT
TN
mg/1
1
2
2
1
1
1
1
2
0
1
1
1
1
.5
.3
.0
.0
.4
.7
.8
.1
.9
.2
.3
.7
.6
-------
4.0
3.5
3.0
o>
E 2.5
*
c
0)
£2.0
Z
To 1-5
+*
o
1.0
0.5
Spread Factor = 1.5
Mean
Gulf Gate
Effluent
Standard
5 10 30 50 70 90 98 99.5 99.9 99.99
Percent of Observations
Figure 23. Total Nitrogen Content of Gulf Gate Final Effluent
-------
1.6
1.4
_ 1.2
\
O)
Ei.o
V)
3
0.8
w
O
Q.
_ 0.6
to
0.4
0.2
0.0
Spread Factor = 1.8
Gulf Gate
Effluent
Standard
•Mean
5 10
30 50 70 90
Percent of Observations
99-5 99.9
Figure 24. Total Phosphorus Content of Gulf Gate Final Effluent
-------
The effluent residuals for weekly average values of nitrogen and
phosphorus during 1977 were plotted as frequency distributions. Figure 23
contains the nitrogen data. Gulf Gate produces an effluent with a mean total
nitrogen content of 1.5 mg/1, and achieves the effluent standard of 3 mg/1
96 percent of the time. The spread factor for the data is about the same
as the River Oaks plant for nitrogen control.
The residual phosphorus data on Figure 24 indicates a mean total
phosphorus effluent concentration of 0.5 mg/1 and the effluent standard of
1.0 mg/1 is achieved 90 percent of the time. The spread factor of 1.8 is
slightly better than the 2.4 factor for River Oaks. The equalized flow at
Gulf Gate probably aids in more consistent chemical dosages and consequent
lower spread factors for both nitrogen and phosphorus control.
Considering the analytical variability of BOD , SS, TP, N03-N and TKN,
as reported in the 14th edition of Standard Methods for The Examination of
Water and Wastewater,* both plant effluents are of excellent high quality.
i
Figures 10, 11, 23, 24 and Tables 5 and 9 indicate both facilities are
conscientiously striving to achieve stringent Federal, State and local
effluent limitations.
Publication Office
American Public Health Association
1015 Eighteenth St. NW
Washington, DC 20036
46
-------
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
. REPORT NO.
EPA-600/2-79-075
2.
3. RECIPIENT'S ACCESSION-NO.
4. TITLE AND SUBTITLE
NITROGEN AND PHOSPHORUS CONTROL BY TWO FACILITIES
IN FLORIDA
5. REPORT DATE
July 1979 (Issuing Date)
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
Tom Comfort and Larry Good
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Hillsborough County Utilities Department
P. 0. Drawer 3292
Tampa, Florida 33601
10. PROGRAM ELEMENT NO.
1BC822, SOS #3, Task C/06
11. CONTRACT/GRANT NO.
Grant #R-805005
12. SPONSORING AGENCY NAME AND ADDRESS
Municipal Environmental Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
13. TYPE OF REPORT AND PERIOD COVERED
Final - 2/77 - 2/79
14. SPONSORING AGENCY CODE
EPA/600/14
15. SUPPLEMENTARY NOTES
Project Officer: Edwin F. Earth, (513) 684-7641
16. ABSTRACT
Municipal wastewater treatment plants employing multi-stage processes can
be operated to consistently produce high quality final effluents.
Data for both the 11,400 m /d Hillsborough County, Florida and the
6,813 m /d Florida Cities Water Company facilities are presented in tabular
and geographic form.
These data show that both utilities can achieve the stringent State of
Florida effluent limitations. These limitations, for selected sites in the
State, require that the effluent shall not contain more than 5 mg/1 five day
Biochemical Oxygen Demand, 5 mg/1 suspended solids, 3 mg/1 total nitrogen and
1 mg/1 total phosphorus.
17.
KEY WORDS AND DOCUMENT ANALYSIS
a.
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS
COSATI Field/Group
Activated Sludge Process*
Nitrification
Wastewater*
Nitrogen cycle
Phosphorus removal'
Nitrogen removal*
Tampa Bay
Attached Growth ^
Denitrification
13B
18. DISTRIBUTION STATEMENT
Release to Public
19. SECURITY CLASS (ThisReport)
Release to Public
1. NO. OF PAGES
55
20. SECURITY CLASS (Thispage)
Release to Public
22. PRICE
EPA Form 2220-1 (9-73)
47
4 U.S. GOVERNMENT PRINTING OFFICE: 1979 -657-060/5457
------- |