ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF ENFORCEMENT
EPA-300/2-75-009
Nutrient-Algal Relationships
Lake Lillinonah
Danbury, Connecticut
June-September, 1975
FEDERAL ENFORCEMENT INVESTIGATIONS CENTER
DENVER.COLORADO
AND /^^
REGION I. BOSTON, MASSACHUSETTS f
NOVEMBER 1975
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ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF ENFORCEMENT
NUTRIENT-ALGAL RELATIONSHIPS
IN LAKE LILLINONAH
Danbury, Connecticut
June-September 1975
NATIONAL ENFORCEMENT INVESTIGATIONS CENTER - Denver, Colorado
and
REGION I - Boston, Massachusetts
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CONTENTS
I. INTRODUCTION 1
II. CONCLUSIONS AND RECOMMENDATION . . 3
III. STUDY DESCRIPTION 4
IV. RESULTS AND DISCUSSION 6
APPENDIX A: NPDES PERMIT
NO. CT0100145 ... .10
APPENDIX B: STUDY FINDINGS
TABLES 1-9 18
APPENDIX C: METHODS 28
REFERENCES 33
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TABLES
1 Sampling Parameters and Station
Locations 19
2 Secchi Depth of Receiving Water 20
3 Receiving Water Dissolved Oxygen Profiles . 21
4 Nutrient Analyses of Water and Sediments . 22
5 Nutrient Analyses of Waste and
Receiving Waters 23
6 In Situ Algal Growth Potential Tests
Nutrient Additions 24
7 Algal Growth Potential Tests
Effluent Additions 25
8 Nutrient Removal from Danbury WWTP
Effluent 26
9 Nutrient Analyses of Waste and
Receiving Waters 27
FIGURES
1 Map of Danbury, Connecticut
Lake Lillinooah Area 2
2 Schematic diagram of sampling locations
in the Danbury, Connecticut
Lake Lillinonah Area 5
1v
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I. INTRODUCTION
Lake Lillinonah is an impoundment of the Housatonic River in
western Connecticut [Fig. 1]. The lake is used primarily for power
generation but it has the potential for recreation, including an ex-
cellent smallmouth bass fishery. Despite good public access, lake
recreational resources are limited by summer algal blooms.
A study by the National Eutrophication Survey Program of the
Environmental Protection Agency (EPA) in 1972-73 found that reducing
phosphorus (P) concentrations in Lake Lillinonah would diminish algal
growths.1 The study concluded that phosphorus is the growth-limiting
nutrient in the lake and also identified nutrient point sources. The
Danbury Wastewater Treatment Plant (WWTP) contributed more than 30% of
the phosphorus load to the lake. Consequently, in December 1974, the
state issued NPDES Permit No. CT0100145 requiring the Danbury Plant to
remove phosphorus to correct water quality deficiencies [App. A, paragraphs
16 and 17].
To assess the impact on Lake Lillinonah of nutrient removal at the
Danbury WWTP, EPA-Region I requested that the National Enforcement
Investigations Center (NEIC) provide technical assistance to the State
of Connecticut. The specific study objectives were:
1. Assess water quality conditions in Lake Lillinonah
2. Determine the algal growth-limiting nutrient and critical
nutrient levels for algal growth in Lake Lillinonah
3. Measure the biostimulation characteristics of the Danbury,
Connecticut WWTP discharge and its effects on Lake
Lillinonah
4. Determine the effects of phosphorus removal from the
Danbury WWTP discharge on algal growth in Lake Lillinonah.
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Joiisatonic River
t
N
Shepaug
River
OSeptic Tank Disposal Pit
Lake
Kenosia
Limekiln Brook
East Swamp Brook
Figure 1. Map of the Danbury, Connecticut - Lake Lillinonah Area
(Not to Scale)
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II. CONCLUSIONS AND RECOMMENDATION
1. An algal bloom blanketed the surface of Lake Lillinonah during
the summer of 1975. The bloom was composed primarily of
filamentous blue-green algae, Aphanizamenan and Anabaena.
2. Field and laboratory tests demonstrated that reductions in
phosphorus concentrations would diminish algal growths in Lake
Lillinonah; each 1 ug/1 phosphorus reduction in the lake would
result in a corresponding decrease of 0.02 mg/1 of blue-green
algae.
3. Danbury Wastewater Treatment Plant effluent stimulated algal
growth when mixed with water simulated to represent Lake
Lillinonah.
4. Removing 95% of the phosphorus at the Danbury Wastewater
Treatment Plant would reduce Lake Lillinonah algal growths by
at least 29%.
Based on the study results, the following recommendation is made:
Implement NPDES Permit No. CT0100145, paragraphs 16 and 17, which require
phosphorus removal at the Danbury Wastewater Treatment Plant.
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III. STUDY DESCRIPTION
The Housatonic River enters western Connecticut from Massachusetts
and flows south by southeast to Long Island Sound. Lake Lillinonah is
the first of three run-of-the-river reservoirs in Connecticut. Formed
by construction of the Shepaug Hydroelectric Dam in 1955, the lake
includes backwaters on the Housatonic, Still and Shepaug Rivers. The
lake winds through steep forested valleys which limit shoreline develop-
ment. The Housatonic River arm of the lake is approximately 16 km long
and 1/2-1 km wide with a surface area of about 800 hectares. The up-
stream limit of this arm is near the confluence of the Still and Housa-
tonic Rivers [Fig. 1].
The NEIC conducted a three-phase study to assess the impact of
wastewater discharges from the Danbury WWTP upon nutrient-algal relation-
ships in a portion of the Lake Lillinonah watershed [Fig. 2].
(
In June and August 1975, water samples collected from the Housatonic
and Still Rivers (Stations 11, 12, 14, 15) and wastewater samples collected
from the Danbury WWTP (Station 10) were analyzed for nutrient content
and used in laboratory biostimulation tests.
In July 1975 a field study was conducted. In Lake Lillinonah,
Secchi depth, sediment oxygen demand (SOD), and dissolved oxygen (DO)
were measured at selected stations [App. B, Table 1]. Water and sediment
samples were collected from all lake stations for nutrient analyses.
Primary productivity studies and in situ algal assays were conducted in
Lake Lillinonah (Station 5) to determine the rate of algal growth, and
to verify laboratory biostimulation test results. Water and wastewater
samples were collected for algal assays as described previously except
the actual test was in situ. Methods for the entire study are presented
in Appendix C.
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Goodye;
''Island
Route 133
o «-
<0 >
I/I T-
Shepaug Dam
Figure 2.
Schematic diagram of sampling locations in the Danbury, Connecticut
Lake Lillinonah Area
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IV. RESULTS AND DISCUSSION
The algal bloom that blanketed the surface of Lake Lillinonah
during the summer of 1975 was composed of filamentous blue-green algae,
Aphanizomenon and Anabaena. Primary productivity tests revealed that
the algae grew profusely at the rate of 1,511 mg Carbon/m /day in the
top 4 meters of the lake. The algae appeared to be uniformly dense to a
depth of 6-8 meters. This dense growth reduced water clarity and caused
major fluctuations in the dissolved oxygen concentrations in Lake
Lillinonah. Secchi depth ranged from 0.6 to 2.3 meters [App. B, Table 2],
Dissolved oxygen ranged from 4.0 to 17.6 mg/1; usually the lowest
concentrations occurred near the lake bottom [App. B, Table 3]. The SOD
rate was 1.4 g Oxygen/m /day inferring that the decrease in oxygen with
lake depth was related to algal productivity, particularly respiration
and decomposition, in addition to SOD. Study results indicated that a
reduction in the algal population would subsequently improve the en-
vironmental conditions in Lake Lillinonah.
Water and sediment samples collected at 9 stations in Lake Lilli-
nonah were analyzed for nutrient content. Results showed that the
nutrient concentrations in the water and sediment were highest in the
upper end of the reservoir near the confluence of the Housatonic and
Still Rivers [App. B, Table 4]. Additional nutrient studies at the
mouths of these lake tributaries showed that the Still River contributed
an average concentration of 2.4 mg/1 nitrogen and 0.9 mg/1 phosphorus.
This was approximately 9 times the average concentration of nitrogen and
^4 times the average concentration of phosphorus contributed by the
Housatonic River [App. B, Table 5]. Reportedly, the major source of
nutrients in the Still River was the Danbury WWTP.1
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Algal assays were conducted in June, July and August 1975 to
determine the significance of the Danbury WWTP discharge as a nutrient
source. As described in Methods [App. C] Lake Lillinonah water was
simulated in the laboratory by proportionally mixing water from the
Housatonic River (Stations 14 and 15) with water from the Still River
(Stations 11 and 12). Algal assay tests showed that this lake water
stimulated only minor growth of test algae Selenastrum and Andbaena.
The in situ tests were the most extensive and a summary of this data is
presented in Appendix B, Table 6.
To determine if nitrogen or phosphorus was the growth-limiting
nutrient, various concentrations of these nutrients were added to
simulated lake water. Assays using green and blue-green test algae
responded to the nutrient additions differently. In the June and July
tests with the green algae Selenastrwn, nitrogen additions stimulated
algal growth; in August, phosphorus additions were found to stimulate
algal growth. Phosphorus additions stimulated algal growth in all tests
with the blue-green alga Anabaena.* Therefore, phosphorus was the
growth-limiting nutrient in all tests with Andbaena and in August tests
with Selenastrum. The in situ tests were the most extensive and a
summary of this data is presented in Appendix B, Table 7.
As discussed earlier, the algal bloom in Lake Lillinonah was
composed largely of blue-green algae and subsequent algal assays demon-
strated that phosphorus must be limited to control blue-green algal
growth. The algal assays also indicated that each reduction of 1.0 ug/1
of phosphorus resulted in a corresponding reduction of 0.02 mg/1 dry
weight of blue-green algae.
* Some blue-green algae including Anabaena and Aphanizomenon are
capable of using atmospheric nitrogen as a nutrient source.
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8
Biostimulatory characteristics of the Danbury WWTP effluent were
evaluated from the results of another series of algal assays. Effluent
from the DAnbury WWTP was serially diluted with stimulated lake water
and the mixtures were inoculated with algal cells. The effluent and
lake water mixture stimulated an algal bloom. On a maximum dry-weight
basis algal growth increased an average of 482% when compared to growth
In lake water without the effluent addition [App. B, Table 7].
In a final series of laboratory tests, the Danbury WWTP effluent
was treated with calcium hydroxide, CafOHjg, which precipitated
(removed) an average of 96% of the phosphorus [App. B, Table 8]. The
treated effluent was added to lake water containing test algae. Results
showed that the treated effluent stimulated 90% less algal growth than
the phosphorus-rich effluent that was being discharged by the Danbury
WWTP [App. B, Table 7].
The State of Connecticut has developed a Housatonic River Basin
Model that can be used to show the relationship of nutrient removal at
the Danbury WWTP to the reduction of nutrients in Lake Lillinonah.2
According to model predictions and laboratory test results described
herein, the removal of 96% of the phosphorus from the Danbury WWTP
effluent would result in a phosphorus contribution into Lake Lillinonah
of between 0.01 and 0.02 mg/1 from the Still River. Therefore 96%
phosphorus removal at the Danbury WWTP will ultimately reduce algal
growth in Lake Lillinonah"by at least 29%. For minimum algal problems
nutrient levels should not exceed 0.30 mg/1 inorganic nitrogen and 0.01
mg/1 ortho phosphorus.3 However, any reductions in Lake Lillinonah
phosphorus concentration will result in reductions in algal growths.
ASSOCIATED STUDY OBSERVATIONS
Nutrient studies were conducted in the Still River watershed near
the Danbury WWTP to obtain supplemental information concerning nitrogen
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and phosphorus sources. Results showed that the Still River at Eagle
Road (Station 12) had nutrient concentrations of 1.4 mg/1 inorganic N,
0.7 mg/1 total P. Upstream concentrations for the Still River at Lake
Kenosia were much lower (0.02 mg/1 inorganic N, 0.15 mg/1 total P) [App.
B. Table 5]. The only known nutrient source between the two stations is
Sympaug Brook which carries wastes from the Bethel WWTP. Reportedly,
this plant contributes less than 2% of the annual phosphorus load to
Lake Lillinonah.1 Increases in nutrient concentrations were observed
downstream from the Danbury WWTP to Station 4 in the headwaters of Lake
Lillinonah. Because concentrations at the Dump Road 0.1 km downstream
from the Danbury WWTP were higher than concentrations in the effluent
other potential nutrient sources at the Danbury WWTP and Septic Tank
Disposal Pit were sampled [App. B, Table 9). A leak from the grit
chamber at the Danbury WWTP was sampled and found to contain 10.4 mg/1
inorganic N and 19 mg/1 total P. The plant is under State order to
eliminate this unpermitted discharge. Nutrient concentrations in this
discharge were sometimes higher than in the influent. This discharge
accounts for only part of the increased nutrient concentrations at the
Dump Road. The concentrated wastes of the septic tank disposal pit
contained 130 mg/1 inorganic N and 185 mg/1 total P. The septic tank
disposal pit is located in the sanitary landfill and has no discrete
discharge. The area is swampy and located within 1 km of the Danbury
WWTP [Fig. 1].
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APPENDIX A
NPDES PERMIT NO. CT0100145
FOR DANBURY WASTEWATER TREATMENT PLANT DISCHARGE 001
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STATE OF CONNECTICUT
DEPARTMENT OF ENVIRONMENTAL PROTECTION
£•. .j . ^ -• '^^1
':< STATE OFFICE BUILDING HARTFORD, CONNKCTICUT 06115
WATER COMPLIANCE AND HAZARDOUS SUBSTANCES
DIVISION OF ENVIRONMENTAL QUALITY
CONNECTICUT DEPARTMENT OF ENVIRONMENTAL PROTECTION
STATE OFFICE BUILDING - ROOM 129
HARTFORD, CONNECTICUT 06115
NPDES PERMIT
City of Danbury
City Hall
174 Main Street
Danbury, Connecticut 06810
Attention: Mr. Charles Ducibella
Mayor
Re: DEP/WPC 034-S01
City of Danbury
Still River Watershed
Gentlemen:
This order is authorized to be issued by Chapter 474a, Connecticut
General Statutes and Section 402(b), Federal Water Pollution Control Act
Amendments of 1972, 86 Stat. 816 et. seq., and pursuant to an approval
dated September 26, 1973, by the Administrator of the United
States Environmental Protection Agency for the State of Connecticut to
administer an N.P.D.E.S. permit program.
Your application, filed with the Connecticut Department of Environmental
Protection on May 11, 1973 has been reviewed by the Connecticut Department
of Environmental Protection.
The Director, Water Compliance and Hazardous Substances Division, Department
of Environmental Protection (hereinafter "the Director") hereby finds
that the City of Danbury is maintaining a facility described in the above
referenced application which no longer insures or adequately protects
against pollution of the waters of the state under the provisions of
Chapter 474a of the Connecticut General Statutes.
The Director, acting under Section 25-54J hereby orders the City of
Danbury to take such action as is necessary to:
1) Insure that all wastewaters described in the above referenced
application are collected, treated and discharged in accordance with the
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plans and specifications approved by the Director on March 4, 1970 together
with associated engineering documents, correspondence and other data submitted
to comply or obtained to verify compliance with Order No. 7 entered on
May 15, 1967 and/or discharged in accordance with this order.
2) Insure that all discharges described in this order shall not
exceed and shall otherwise conform to the specific terms and general
conditions specified herein.
A) Discharge Serial No. 001 (Effluent)
Receiving Stream - East Swamp Brook
Average Daily Flow - 12,500,000 gallons per day
Before September 30. 1977
Monthly Average Monthly Average Minimum Percentage
Parameter ' Quantity Concentration Removal Efficiency
Biochemical Oxygen Demand 1419.4 kg/day 30 mg/1 85%
Suspended Solids 1419.4 kg/day 30 mg/1 85%
1) The discharge shall be required to meet the more stringent
of the monthly average concentration or minimum removal
efficiency requirements for each parameter.
2) The monthly average quantities and monthly average con-
centrations specified above shall not be exceeded by a
factor of 1.5 during any week.
3) The pH of the discharge shall not be less than 6.5 nor greater
than 8.0 at any time.
4) The discharge shall not contain a visible oil sheen, foam
or floating solids.
5) The discharge shall not contain more than 0.1 milliliters
per liter settleable solids.
"6) The discharge shall not.cause visible discoloration of the
receiving waters.
7) The total chlorine residual of the effluent shall not be
less than 0.5 mg/1 nor greater than 3.0 at any time.
8) The geometric mean of the total coliform bacterial values
for the effluent samples collected in a period of 30
consecutive days shall not exceed 1000 per 100 milliliters
The geometric mean of these values for effluent samples
collected in a period of seven consecutive days shall
not exceed 2000 per 100 milliliters.
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- 3 -
After September 30, 1977
In conformance with the criteria to be established in the engineering
report required by paragraph F.
3) Not discharge any new pollutant not authorized by this order which
has or may have an adverse impact on the receiving waters.
4) Monitor and record the following for the purpose of reporting
quality and quantity of each discharge according to the following schedule:
A) Influent
Minimum Frequency
Parameter of Sampling. Sample Type
Biochemical Oxygen Demands Twelve per Month Composite
Suspended Solids Twelve per Month Composite
Temperature Twenty per Month Grab
pH Twenty per Month Grab
Settleable Solids Twenty per Month Grab
Total Phosphorus One per Month Composite
Organic Nitrogen as N One per Month Composite
Ammonia Nitrogen as N One per Month Composite
Nitrite-Nitrate as N One per Month Composite
a) Record the total flow during the period of composite sample
collection and the instantaneous flow at the time of each
aliquot sample collection, and the instantaneous flow at
the time of grab sample collection.
b) Any grab sample or composite sample required to be
taken less frequently than daily shall be taken during the
, period of Monday through Friday inclusive. Composite samples
and grab samples shall be taken between 6 a.m. and 6 p.m.
B) Discharge Serial No. 001 (Effluent)
Minimum Frequency
Parameter ' of Sampling Sample Type
Biochemical Oxygen Demands Twelve per Month Composite
Suspended Solids Twelve per Month Composite
Chlorine Residual Four per Working Day Grab
Total Coliform Four per Month Grab
Dissolved Oxygen Twenty per Month Grab
Temperature Twenty per Month Grab
pH Twenty per Month Grab
Turbidity Twenty per Month Grab
Settleable Solids Twenty per Month Grab
Total Phosphate as P One per Month Composite
Organic Nitrogen as N One per Month Composite
Ammonia Nitrogen as N One per Month Composite
Nitrite-Nitrate as N One per Month Composite
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a) Record and report on a daily basis the minimum, maximum
and total flow of the discharge.
b) Record the total flow during the period of composite sample
collection and the instantaneous flow at the time of each
aliquot sample collection, and >the instantaneous flow at
the time of grab sample collection.
c) Any grab sample or composite sample required to be taken
less frequently than daily shall be taken during'the period
of Monday through Friday inclusive. Composites and grab
samples shall be taken between 6 a.m. and 6 p.m.
5) Monitor and record the following operational parameter according to
the following schedule:
Minimum Frequency
Parameter Location of Sampling Sample Type
Temperature Each Digestion Unit Weekly Grab
Alkalinity Each Digestion Unit Weekly Grab
Volatile Acids Each Digestion Unit Weekly Grab
pH ' Each Digestion Unit Weekly Grab
A) Record the gallons of septage discharged to the treatment
facility for the month.
B) Record the pounds of dry solids discharged to and removed
from the solids handling system on a monthly basis.
C) Record the chlorine dosages in pounds and mg/1 on a daily
basis.
D) Record the percentage of recycled flow on a daily basis.
E) Record the volume of digester gas produced on a monthly
basis.
6) Not bypass the treatment facilities at any time except as may be
authorized in Section 2 of this order and/or under emergency conditions.
The Water Compliance Unit Sewerage Facilities Services Section,
(Telephone No. 566-2409 or 566-2373) shall be notified during normal
working hours, Monday through Friday 8:30 a.m. to 4:30 p.m. and in
writing within 72 hours, of each occurrence of an emergency diversion or
bypass of untreated or partially treated sewage, or failure of any major
component of the treatment facilities which would reduce the quality of
the effluent. The written report shall contain:
a) The cause of the diversion or bypass or treatment component
failure.
b) The time the incident occurred and the anticipated time
which it is expected to continue or, if the condition has
been corrected, the duration.
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c) The steps being taken to reduce and minimize the effect
on the receiving waters.
d) The steps that will be taken to prevent reoccurrence of the
condition in the future.
7} Dispose of screenings, sludges and other solids or oils and other
liquid chemicals at locations approved in accordance with the provisions
of Chapter 474a and/or Chapter 361a of the Connecticut General Statutes
or to waste haulers licensed under Chapter 474a of the Connecticut
General Statutes.
i
8) Provide an alternate power source and/or such other means as may be
appropriate to adequately operate the wastewater treatment facility
and/or pumping stations to insure that no discharge of untreated wastewater
will occur during a failure of the primary power source.
9) No new dishcarge from a single source to the sewage system of: 1)
domestic sewage in excess of 5,000 gallons per day, 2) industrial wastewaters;
and/or 3) cooling waters may be authorized without the discharger first
obtaining a permit from the Director.
10) On or before April 10, 1975 and monthly thereafter, submit to the
Director a listing of all new discharges authorized to be connected to
the wastewater collection system.
11) On or before March 31, 1975 submit for the review and approval of
the Director a Sewer Ordinance regulating discharges to the wastewater
collection system.
«
12) On or before March 31, 1975 verify to the Director that compliance
with paragraph 1 is being achieved and that the provisions of paragraphs
2, 3, 4, 5, 6, 7, 8 and 9 will be complied with.
13) On or before March 31, 1975 submit for the review and approval of
the Director a report detailing the existing or proposed system of
achieving compliance with the terms of paragraph 8 including if appropriate
a time schedule for: 1) the submission of plans and/or specifications,
2) the start of construction, and 3) the placing of the system in operation.
14) On or before August 10, 1975 and before the 10th of each month
thereafter, submit to the Director all detailed monitoring data required
under the provisions of paragraphs 4 and 5 above.
15) On or before September 30, 1975 verify to the Director that all
construction required by paragraph 8 above has been completed.
16) Install alterations and/or additions to the existing wastewater treatment
facility to .provide the level of treatment necessary to correct water
quality deficiencies in East Swamp Brook, the Still River and Housatonic
River giving special attention to the removal of additional carbonaceous
and nitrogenous biochemical oxygen demand, and phosphorous. The specific
loading allocations to be considered in the design of such additional
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treatment facilities will be established at the pre-report conference and
confirmed in the engineering report.
17) Install temporary alterations and/or additions to the existing waste-
water treatment facility and modifications to the operational procedures
as may be practical to provide for the removal of phosphorous until such
time as the requirements of paragraph 16 above are accomplished.
The above described specific terms may be revised foil-owing public
notice and public hearing, if required, and/or on the basis of a detailed
engineering study if agreed to by the Director.
The City of Danbury is further ordered to accomplish the above
described program, except as may be revised by agreement reached at or
following the pre-report conference required by Section 25-54v of the
Connecticut General Statutes or as amended by the recommendations of a
detailed engineering study and agreed to by the Director in accordance
with the following schedule:
A) On or before April 30, 1975 submit for the review and
approval of the Director a report describing such
alterations/additions in staffing and operating procedures
as may be required to assure compliance with the specific
terms of this order.
B) On or before July 31, 1975 verify to the Director that
such procedures have been placed in operation.
C) On or before July 31, 1975 verify to the Director that
such additional manpower necessary to assure compliance
with the specific terms of this order has been employed.
D) On or before May 31, 1975 submit for the review and' approval
of the Director an engineering report containing an inflow-
infiltration analysis of the wastev/ater collection system
prepared in accordance with the requirements of 40 C.F.R.
§ 35.927 (39 Federal Register 5262).
E) On or before September 30, 1976, if deemed necessary by
the Director as a result paragraph D above, submit for
the review and approval of the Director an engineering
report containing a inflow-infiltration evaluation prepared
in accordance with 40 C.F.R. § 35.927 (39 Federal Register
5262).
F) On or before June 30, 1975 submit for the review and approval
of the Director an engineering report addressing the re-
quirements of paragraph 16 above prepared in accordance
with § 25-54v which shall include a current detailed cost
estimate of the eligible construction work.
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G) On or before June 30, 1975 submit for the review and approval
of the Director contract plans and specifications with a
summary basis of design for alterations and/or additions as
may be required to comply with oaragraph 17 above.
H) On or before October 31, 1975 verify that the construction
of the alterations and/or additions to the existing waste-
water treatment facility and modifications to the operational
procedures required to comply with paragraph 17 above has
been completed.
I) On or before January 31, 1976 submit for the review and
approval of the Director contract plans and specifications
for the alterations and/or additions required to comply
with paragraph 16 above.
J) On or before February 29, 19fr? verify to the Director that
all the necessary local financing for the alterations and/or
additions required to comply with paragraph 16 above has
been completed.
K) On or before April 30, 1976 verify to the Director that
advertising for bids for the alterations and/or additions
required to comply with paragraph 16 above has been
completed.
L) On or before June 30, 1976 verify to the Director that
construction of the alterations and/or additions required
to comply with paragraph 16 above has been started.
M) On or before September 30, 1977 verify to the Director aht
the constructed facilities have been placed in operation.
This order shall be considered as the permit required by Section 402 of
the Federal Water Pollution Control Act and shall expire on December 30, 1979.
This order shall be subject to all the NPDES General Conditions dated
December
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APPENDIX B
STUDY FINDINGS
TABLES 1-9
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Table 1
SAMPLNG PARAMETERS AND STATION LOCATIONS
LAKE LILLINOUAH - DANBURY, CONNECTICUT
July 1975
Station
Number
1
2
3
4
5
6
7
8
9
Location
Surface
Mater
Lake Lillinonah
Still River 0.2 km upstream
from mouth
Still River at mouth
Housatonic River at Lanesville Road
Housatonic River at first island
downstream from Goodyear Island
Housatonic River at Route 133 X
Housatonic River at cove near
Shepaug Dam
Housatonic River upstream from
Shepaug Dam
Shepaug River 1.0 km upstream from
mouth
Shepaug River at mouth
Nutrient Sources
Nutrients
Bottom
Water
X
X
X
X
X
X
X
X
X
Parameters Measured
Primary Sediment
Sediment Production Oxygen
Demand
X
X
X
X
XXX
X
X
X
X
Dissolved
Oxygen
X
X
X
X
X
X
X
Secchi
Depth
X
X
X
X
X
X
X
X
X
10 Danbury WWTP Effluent X
Housatonic and Still Rivers
11 Still River at Lake Kenosia X
12 Still River at Eagle Road X
13 Still River at Lanesville Road X
14 Housatonic River at Boardman's
Bridge X
15 Housatonic River at Lands End
Marina X
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20
Table 2
SECCHI DEPTH OF RECEIVING WATER
LAKE LILLINONAH - DANBURX, CONNECTICUT
July 1975
Station
Number
1
2
3
4
5
6
7
8
9
15
Location
Still River 0.2 km upstream from mouth
Still River at mouth
Housatonic River at Lanes vi lie Bridge
Housatonic River at first island
downstream from Goodyear Island
Housatonic River at Route 133
Housatonic River at cove near Shepaug Dam
Housatonic River upstream from Shepaug Dam
Shepaug River 1.0 km upstream from mouth
Shepaug River at mouth
Housatonic River at Lands End Marina
Secchi Depth
(meters )
0.6
0.7
1.0
. 2.0
2.3
1.9
2.0
2.0
2.1
1.0
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Table 3
RECEIVING WATER DISSOLVED OXYGEN PROFILES
LAKE LILLINOMH - DANBURY, CONNECTICUT
July 1975
Station
Number
2
3
4
5
7
9
15
Location Depth
(meters)
Still River Surface
at mouth 2
Housatonic River Surface
at Lanesville 3.5
Bridge 7
Housatonic River Surface
at first island 3
downstream from 6
Goodyear Is.
Housatonic River Surface
at Route 133 2
4
14
Housatonic River Surface
upstream from 10
Shepaug Dam 20
28
Shepaug River Surface
at mouth 3
6
Housatonic River Surface
at Lands End 2
Marina 4
Temperature
(°C)
26.5
25.0
25.0
25.0
24.5
27.0
26.0
25.0
27.5
26.5
25.5
23.0
29.5
23.5
22.5
22.0
28.0
25.5
23.5
25.0
24.5
24.5
Dissolved
Oxygen
(mg/1)
6.3
8.3
9.5
9.1
9.2
17.6
9.2
6.4
14.9
10.5
8.4
7.0
16.0
6.8
6.9
5.4
14.8
8.3
4.0
9.6
8.8
11.4
Saturation
(%)
77
99
113
108
109
217
112
76
186
128
101
80
208
79
78
61
187
100
47
114
105
136
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Table 4
NUTRIENT ANALYSES OF VATER AND SEDIMENTS
LAKE LILLINONAH - DANBURY, CONNECTICUT
July 1975
Station
Number
1
2
3
4
5
6
7
8
9
15
Location
Still River 0.2 km upstream
from mouth
Still River at mouth
Housatonic River at Lanesville
Road
Housatonic River at first island
downstream from Goodyear Island
Housatonic River at Route 133
Housatonic River at cove near
Shepaug Dam
Housatonic River upstream from
Shepaug Dam
Shepaug River 1.0 km from mouth
Shepaug River at mouth
Housatonic River at Lands End
Water
Inorganic N
(mg/1)
1.9
1.3
0.71
0.15
0.49
0.48
0.43
0.33
0.37
Total P
(mg/1)
8.8
2.2
3.6
0.24
1.6
1.1
1.6
1.8
1.6
Sediment
Total P
(mg/g)
2.3
1.2
1.4
1.8
1.4
2.9
1.8
0.9
1.3
Marina
0.55
1.5
0.8
ro
ro
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Table S
NUTRIENT ANALYSES OF WASTE AND RECEIVING WATERS
LAKE LJLLINONAH - DANBUPY, CONNECTICUT
Station
Number
10
11
12
13
14
15
5
Location
Danbury WWTP effluent
Still River at Lake Kenosla
Still River at Eagle Road
' Still River at Lanesville Road
Housatonic River at Boardman's
Bri dge
Housatonic River at Lands End
Marina
Housatonic River at Route 133
Inorganic N (mq/1)
June
14.2
1.4
3.0
0.05
<0.20
<0.03
July
8.9
<0.02
0.71
1.1
<0.32
<0.36
<0.02
August
11.1
0.02
2.0
3.0
0.37
<0.27
0.38
Average
11.4
0.02
1.4
2.4
0.25
0.28
0.14
June
8.8
0.56
0.30
0.17
. 0.10
0.25
Total P (mq/1)
July
7.2
0.15
0.54
0.90
0.47
0.39
0.23
August
6.9
0.15
1.1
1.6
0.29
0.19
0.18
Average
7.6
0.15
0.73
0.93
0.31
0.23
0.22
ro
CO
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24
Table 6
JN SITU ALGAL GROWTH POTENTIAL TESTS - NUTRIENT ADDITIONS
LAKE LILLINONAH - DANBURY, CONNECTICUT
July 1975
Addition
(mg/1)
Control
(100% simulated
Lake Water)
0.3N
l.ON
3. ON
ION
0.03P
0.1P
0.3P
l.OP
l.ON, 0.1P
3. ON, 0.3P
Inorganic N
(mg/1 )
0.32
0.62
1.32
3.32
10.32
0.32
0.32
0.32
0.32
1.32
3.32
Total P
(mg/1 )
0.17
0.17
0.17
0.17
0.17
0.20
0.27
0.57
1.17
0.27
0.47
Maximum yield
Selenastrum
21.2
22.7
24.3
23.7
21.6
21.0
20.0
20.0
20.5
47.9
71.8
(mg/1 -dry wt)
Anabaena
16.2
15.4
17.8
16.7
15.2
19.9
20.5
29.1
24.6
45.4
73.3
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Table 7
ALGAL GROWTH POTENTIAL TESTS - EFFLUENT ADDITIONS
LAKE LILLINONAH - DANBURY, CONNECTICUT
July 1975
Addition
(*)
Control
(100% simulated
lake water)
0.3
1.0
3.0
10.0
25.0
Inorganic N
Danbury 001
0.32
0.34
0.40
0.57
1.16
2.42
(rag/1 )
Treated
0.34
0.40
0.57
1.16
2.42
Total
Danbury 001
0.
0.19
0.23
0.35
0.78
1.70
P (mg/1)
Treated
17
0.17
0.17
0.18
0.19
0.21
Maximum
Danbury 001
21.
22.7
22.4
27.8
42.9
75.7
yield*
Treated1"
2
19.5
20.1
21.4
23.6
17.8
t mg/l - dry wt.
tt Treated with 400 mg/l Ca(OH)
ro
in
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Table 8
NUTRIENT REMOVAL FROM DANBURY WffTP EFFLUENT
LAKE LILLINONAH - DANBUPY, CONNECTICUT
Month
(1975)
Total P Qnq/1)
Intake
Effluent
Stripped
% Phosphorus Removal
Influent Effluent
June
July
August
9.9
20.0
21.0
8.8
7.2
6.9
0.43
0.34
0.19
96.6
98.3
99.1
96.0
95.3
97.2
ro
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Table 9
NUTRIENT ANALYSES OF WASTE AND RECEIVING WATERS
LAKE LILLINONAH - DANBURY, CONNECTICUT
Location
June
Danbury WWTP influent ' 9.7
Danbury WWTP bypass (grit chamber leak)
Danbury septic tank disposal pit
East Swamp Brook at Heckauer Park
Limekiln Brook at Meckauer Park
Limekiln Brook at Dump Road
Limekiln Brook at Newtown Road
Housatonic River downstream from
Shepaug Dam 0.40
Inorganic N (mg/1)
July
10.4
10.6
110
0.23
0.21
8.5
3.9
0.41
August
17.3
10.3
150
0.41
0.39
12.3
7.8
0.58
Average
12.5
10.4
130
0.32
0.30
10.4
5.8
0.46
Total P (mq/1)
June July
9.9 20
24
60
0.27
0.22
8.4
3.3
0.05 0.24
August
21
14
310
0.09
0.37
9.3
4.9
0.19
Average
17
19
185
0.18
0.30
8.8
4.1
0.16
ro
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APPENDIX C
METHODS
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29
METHODS
NUTRIENTS
Nutrient analyses (NH3 - N, N02 + N03 - N, ortho and total P) were
performed on a Technicon Autoanalyzer using procedures described in EPA
Methods of Chemical Analysis of Water and Wastes.1* Nutrient analyses
were conducted on all receiving water, effluent, and sediment samples
collected during the survey. All samples were collected by grab sampling.
Water samples were preserved with mercuric chloride (40 mg/1). All
samples for nutrient analyses were labeled, placed in an ice chest,
chilled, and transported to NEIC for analyses.
ALGAL GROWTH POTENTIAL
Algal growth potential (AGP) tests were performed as outlined in
Algal Assay Procedure - Bottle Test, August 1971.5 Samples were autoclaved
to kill indigenous algae. An inoculum of green algae, Salenastnm
capricornutwn, or blue-green algae, Anabaena flos-aquae, (standard test
organisms) was added to each test container. Receiving water was a
mixture of Housatonic and Still River water collected upstream of major
local nutrient sources. The mixture was based on low flow contributions
of the Housatonic and Still Rivers to Lake Lillinonah. Standard test
conditions (volume, light, temperature, shaking, incubation period)
remained constant in each test. Algal growth was measured by in vivo
fluorescence and gravimetrically. Tests were run in situ and in the
laboratory. In situ tests were made in 1 liter cubitaners in the reservoir
under ambient light and temperature conditions. Laboratory tests were
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30
made in 250 ml Erlenmeyer flasks under 24-hour light and constant
temperature conditions. The following experimental variables were
tested: filtered versus unfiltered receiving water, green versus blue-
green algal inoculum, raw versus treated effluent, and effluent versus
nutrient additions.
NUTRIENT REMOVAL
Phosphorus removal was attempted on Danbury WWTP effluent samples.
Phosphorus was precipitated by adding hydrated lime (400 mg/1 Ca(OH)2)
to the sample and shaking it vigorously for two minutes. Next, the
effluent was allowed to settle and the supernatant was drawn off.
Nutrient analyses were performed at NEIC.
PRIMARY PRODUCTION
Primary production was measured as outlined in the 13th edition of
Standard Methods for Examination of Water and Wastewaters (197I).6 The
depth of the euphotic zone (1% light) was determined with a submarine
photometer. Light energy received during incubation periods and daily
photoperiods were determined with a pyrheliograph. Water samples were
collected with a Van Dorn sampler. Five 300-ml bottles were filled with
water collected from each depth of the subdivided euphotic zone. Three
of these bottles were unaltered and considered light bottles. One of
the light bottles was fixed immediately and used to measure initial DO.
All light penetration was eliminated from the remaining two bottles.
The two light and two dark bottles were suspended in the water at the
depth from which the sample was obtained, and after incubation the
bottles were fixed immediately and iced in a dark container until
titration. Samples were analyzed according to the azide modification of
the Winkler Method.6
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31
ALGAL POPULATIONS
To assess algal bloom populations, surface grab water samples were
collected and preserved with 5% formalin and examined microscopically at
NEIC.
SEDIMENTS
Sediments and interstitial water samples were collected by scuba
divers. Plastic coring tubes were turned into the sediment by hand and
capped. The overlying few centimeters of water were preserved as an
interstitial water sample and the top few centimeters of sediment were
extruded from the tube into a whirlpac. This technique provided an
undistrurbed sediment sample. The samples were analyzed for nutrients
at NEIC.
SEDIMENT OXYGEN DEMAND
The sediment oxygen demand (SOD) rate was estimated from changes in
the oxygen content of water sealed and stirred in situ in a cylindrical
chamber constructed of clear plexiglas. The chamber was bolted to an
aluminum supporting flange and placed on the lake bottom by scuba
divers. The lid was lowered into place and secured. The chamber
2
covered 0.07 m of bottom sediments and entrapped 20.5 1 of water over
the sediments. Water was circulated in the chamber by the submersible
stirrer for the dissolved oxygen probe. The dissolved oxygen content of
the entrapped water was monitored with a portable dissolved oxygen
meter. A port in the lid allowed salt to be injected into the system to
raise the specific conductance. Samples were withdrawn through this
port and the conductivity was measured as a check against leakage.
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32
Clear BOD bottles containing near-bottom water were incubated 0.5 m
above the bottom to estimate dissolved oxygen changes in the water
overlying the sediment to separate water column and sediment effects.
FIELD MEASUREMENTS
Field measurements included temperature, pH, DO, and Secchi depth,
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33
REFERENCES
1. Environmental Protection Agency, The Nousatonic Impoundments-
forking Peeper Ho. 181, National Eutrophication Survey, Corvallis,
Ore., 1975, 31 p.
2. Connecticut Department of Environmental Protection, Housatonic
River Basin Plan, Water Compliance Unit, Hartford, Conn., 1975,
17 p.
3. Sawyer, Clair N., Fertilization of Lakes by Agricultural and Urban
Drainage, New England Water Works Association, Vol. 61, No. 2, 1947,
p. 109-127.
4. Environmental Protection Agency, Methods of Chemical Analysis of
Water and Wastes, Analytical Quality Control Laboratory, Cincinnati,
Ohio, 1971, 312 p.
5. Environmental Protection Agency, Algal Assay Procedure-Bottle Test,
Pacific Northwest Water Laboratory, Corvallis, Ore., 1971, 82 p.
6. Taurus, M. J., et al, Standard Methods for the Examination of
Water and Wastewater* 13th ed., American Public Health Association,
New York, 1971, 834 p.
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