TECHNICAL ASSISTANCE PROGP AM
Dartmouth, Mass .
UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
REGION I
Operation and Maintenance Section
Water Programs Division
John A. S. McGlennon
Regional Administrator
August 1975

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INTRODUCTION
This report describes the results of an Environmental Protection Agency
Technical Assistance projecL at the Dartmouth, Massachusetts Wastewater
Treatment Facility. Personnel From EPA’s Operation & Maintenance Section
Regioi 1 and the Southeast Regional Office of the Massachusetts Division of
Water Pollution Control participated in the training of Dartmouth personnel
in Operation Contr-ol Testing and Process Control Procedures. The return
sludge flo i control method used was formulated by A.W. West of EPA’s
National Field Investigations Center in Cincinnati, Ohio, The request
for assistance originated with the Toxin of Dartmouth, Massachusetts and
was approved by the Massachusetts Water Resources Commission. The
cooperation and assistance of the personnel at the Dartmouth Wastewater
Treatment Plant and the Massachusetts Water Resources Commission,
Division of Water Pollution Control are gratefully acknowledged.
PURPOSE
The purpose of the Dartmouth Technical Assistance Project was to create a
focal point for interest in the West method by training the operator of a
successfully operating plant. The project would train an operator, provide
a training opportunity for State and Federal engineers, and potentially
improve th quality of the plant effluent.
PLANT SELECTION
Following a series of technical assistance projects at troubled plants, the
O & N Section decided to provide technical assistance and training at a
plant more typical of New England. It was decided that a small, well-
operating activated sludge plant with adequate controls wodid be good for
this purpose.
In November, 1974, M. David Andrade, Chief Operator of the Dartmouth
Wastewater Treatment Plant, called EPA directly to request training in
West’s return sludge flow control method. The Dartmouth Plant had a
history of successful operation. (See Appendix)
PRELIMINARY EVALUATION
The plant was given a preliminary evaluation by the two senior members
of the 0 & M staff in January, 1975. The plant appeared to have good
potential as a focal point for interest in the West method. The operator
was interested. The plant was modern, had adequate controls, and was
located in an area surrounded by many new plants. There is an active
operators’ association in Southeastern, Massachusetts and there is need
for Iraining in plant process control.

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PLANT DESCRIPTION
The Dartmouth Water Pollution Control Facility is a modified extended
aeration plant that has been in operation since 1971. The design
capacity is 2.0 mgd and current flow is 400,000 gpcl. Processes include
grit removal, comminution, aeration, sedimentation and chlorination.
All sewage is pumped to the influent pumping station from pumping
statiøns at Tucker Road, Russells Mills Road, and Clarence Street. The
two variable speed and one constant speed pumps at the treatment plant
are equipped wit1 .automatic controls to smooth the flows to the trealment
facility.
The plant is manned 40 hours a week by a staff of three. There is no
night, weekend, or holiday coverage. No industrial, wastes are treated
at the plant.
PR EPAR AT ION
A final field reconnaissance was performed a week prior to the T.A.
The plant was operating with only one aeration tank and one clarifier.
The detention time in the aeration tank was typical of a plant running
in the conventional activated sludge mode. The mechnical aerator was
running 2 hours on, 2 hours off, during the 40 hour workweek and
constantly the remainder of the time. There was e thick scum on the
final clarftiers and over-oxidized sludge or ash was present in the
effluent. Sludge was discharging onto the ground from grill work
cover of the flow splitter box. A solid cover, added during February,
prevented this from occurring again. S]udge was being wasted and
dewatered on a weekly basis.
Preparation for the T.A. included instruction of the operator in use
of the testing equipment. The operator then began to measure turbidity,
and settled sludge concentration (SSC) and settled sludge volume (Ssv).
The performance data for the plant was reviewed and effluent improvement
goals set. 0 & M staff members hoped that with the West. method the
plant would be able to attain 1 hour turbidities of 2.0 NTU and effluent
concentrations of 5 mg/l BOD and SS. It was decided that it would be
necessary to spend one week in resident work to teach the operator the
testing techniques and how to interpret their results.
TECHNICAL ASSISTANCE IMPLEMENTATION
On February 11, 1975, the one—week resident phase of the technical assistance
effort began. Emphasis was p).aced on teaching the control tests and inter-
pretation of test results. During the 3 month non-resident phase the
operator performed the tests twice daily and discussed the results daily

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with the 0 & M personnel. Biweekly visits were made to the plant.
The process and operational controls were modified.
The return sludge and wasting rates were adjusted using West’s
Clarifier Sludge Flow Demand Formula:
C1.arifier Sludge Flow X(Return Sludge Concentrations — Aeration Link Concentration )
(Settled Sludge Concentration - Aeration Tank Concentration)
All concentrations in the above formula are measured by centrifuge
The following t ble indicates the changes that occurred.
Month RSFmgd RSFP MLSS RSSS
0.511 0.68 4500 9.800
FEB. 0.615 0.83 5500 11.800
MAR. 0.540 0.70 4500 11.100
APR. 0.503 0.71 4100 10.400
When the staff arrived at the plant on February 10 the sludge blanket
was within 4 feet of the clarifier surface and the sludge settled very
slowly in he settloineters. There was a thick scum on the clarrifier
surface and the aeration tank contents had the appearance of older sludge.
It was recognized that a high sludge blanket is subject to washout when
there arc surges in flow and thai a lower b.1.anket was desireable.
A setiling test performed on a mixture of mixed liquor and
unchiorinated clarifier effluent confirmed thai the poor seLtling was
due to an excess of solids.
Wasting of solids and a decrease in return rate led to a marked increase
in return sludge concentration. Mixed ].iquor suspended solids were
reduced from 5,300 to 3,800 mg/I in the first week of Narch. AL the
same time return sludge flow was reduced from U.blSmgd (83i of [ low)
to 0.491. mgd (58% of flow). The return sludge suspended solids
concentration was from 10,800 ing/l to 14,300 mg/l during this period.
In response to these changes the scum cleared from the final clarifier,
the rapidly settling sludge formed a blanket clarifier eight feet from
the surface and the effluent turbidities, measured after one hour of ad-
ditional settling, decreased to less than I NT1J and averaged 1.5 NTIJ.
Two other changes were instituted to smooth operations. No timers were
available for the aerators and the weir was at its lowest level. The
aerators had been switched manually two hours on and two hours off
during the workweek to help lower the disolved oxygen concentration.

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It was decided it would be more beneficial to leave the aerators on
constantly until such time as automatic tuners could be purchased
which could more closely control aeration. IL was also suggested
that rather than wasting large quantities of sludge at large intervals,
smaller quantities could be wasted frequently. This was done during
po .tions of the T.A. effort and had a noticeably smoothing effect on the
settled sludge curves.
After this ver successful week in March, however, the MLSS began to
rise again. The return sludge flows increased and the return sludge
suspended solids concentrations decreased. The blanket level was
held down. Turbidities rose and were generally greater than 3 NTU
for the remainder of the T.A. The morning 5 minute SSV’s were generally
greater than 900 mi/i. On a few occassions the 5 minute SSV’s
were less than 900 mi/i. A decrease in 1 hour turbidity values to ]ess
than 3 NTU followed the improved seLtling. These changes however,
were only short term.
The technical assistance program concluded on April 30, 1975. However,
the operator has agreed to continue sending in weekly reports of the
control testing which will be reviewed by the 0 & [ ‘1 Section.
DATA SUMMARY
Initially, SSV’s and SSC’s fluctuated considerably, but the switch
to more frequent wasting reduced variation somewhat. Turbidity was
lowered to 0.8 NTU during the third week only to rise again as the
SSV’ s increased. By the end of the T.A. the t.urbiditius averaged over
4 NTU. ‘i’hc operator quickly ] earned to keep Lhc return sludge COIl-
centraL ion (RSC) beLween the 30 minute and 60 minute SSC va] UCS.
Seven day moving averages showed that while there had been short-
term changes in plant operation resulting in lowered turbichitics, t.here
was little lasting change in operaLion or effluent quality.
EVALIJATI ON
As a focal point for inLerest in the West method the T.A. was quite
successful. The chief operator, assistant operators, new State and
Federal personnel received training. During this period, the chief
operator trained his staff in the West method and gave a short
presentation at the Naragansett Wastewater Treatment Plant Operators
Association Meeting. Bristol Community College contacted the operator
and EPA to learn more about the method.
Area treatment plant operators have visited the plant to watch the
method in operation and the town has agreed to purchase the necessary
laboratory equipment to continue the method aL the plant.

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The operator reports reduction in final clarifier scum and greater case
and efficiency in sludge wasting. The effluent at the end of ihe T.A.
showed:
1974 1975
JAN k2 25 JAN 21. 21
FEB 24 2 .. FEB 16 13
MAR 19 14 MAR 16 14
APR 22 21 APR 22 15
RBCOMMENDAT ION S
It is recommended that the following changes be implemented to assist
the plant in improving the effluent quality still further.
1. The MLSS concentration should be reduced to minimum and
then raised to find the optimum value.
2. increased control over mixed liquor DO through the use
of timers should be provided.
CONCLUSION
Tile T.A. demonstrated thai the improved plant eff]clcncv attainabI
through the use of the West: method can rc iuce the amount of pol1uiant
being discharged to Buzzards Bay. The plant- s successfulLy serving
as a center for interest in the West mctliod in the Southeastern
Massachusetts area.

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APPENDIX
Table II
South Dartmouth Wastewater Treatment Facility
Performance History
1974
JAN
FEB
MAR
APR
MAY
JUN
JUL
AUG
SEP
OCT
NOV
DEC
ANNUAL VALUE
flow mgd
.585
.527
•&75
.504
.416
.399
.358
.311
.304
.298
.284
.321
.398
Peak flow
.704
.578
.609
.645
.482
.495
.504
.554
.378
.380
.321
.376
.704
Set. Sol. In
Out
0.5
T
0.5
T
0.5
T
1.3
T
2.0
T
1.5
T
2.5
T
1.5
T
2.0
T
2.5
T
3.0
T
1.5
T
1.6
T
Susp. Sol. In
Out
/ Removal
120
25
79
70
24
66
102
14
86
109
21
81
105
9
91
157
7
95
165
6
96
158
6
96
136
11
92
136
13
90
190
8
96
126
8
94
131
12
91
BOD In
Out
% Removal
71
12
83
88
24
73
105
19
82
100
22
78
104
11
89
153
8
95
158
5
97
142
4
97
168
23
86
187
20
89
210
22
89
121
12
90
134
15
89
Effluent DO
Chlorine Res.
pH Minimum
Maximum
4.8
1.0
6.7
9.1
2.6
0.5
6.7
7.5
1.3
1.0
6.9
7.6
3.2
1.0
6.9
7.6
1.4
1.5
6.8
7.4
1.3
0 5
6.4
7.7
6.9
1.0
7.1
7.6
0.8
1.0
6.8
7.8
0.6
1.0
6.5
7.4
0.7
1.0
6.8
7.8
1.0
1.0
6.9
7.7
1.6
1.0
6.8
7.8
2.2
1.0
6.8
7.8

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Log of the Resident Phase
Of the
South Dartmouth Technical Assistance Project
Date/Ti pe Action/Condition
2—10 / 0930 Met with operator
Began Control Tests
RSF = 490 gpm
MLTSS = 5600 mg/i
1030 Discussed DOB
and Dilution Test
1200 Sludge units discussed
1400 Afternoon control tests
began
1430 XSF calculated
XSF = 19500 gal
2-11 0900 Arrive at plant
control test started
0945 CSDT d scusscd and
calcul ated
1000 Discussed and plotted
trrnd charts
stated SSC o RSC = SSC O
]b good
1130 Discu’,sion of reLurn raL
and sludge settling
2-11 1130 Sludge wasting to be
continued. RSC expected
to be reduced to 10
1300 Tour of plant and
flotation thicknc’r —
concentrated sludge
and clear subnatant
1330 Control tests begun
1400 Increased RAS

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2-12 0930 Toured plant
Ash considered indicated
of over aeration Broken
Floc considered sign of
on-off aerators Scum
considered sign of excess
solids in system.
1100 Discussion of equipment
timers, centrifuge, Lurbidi-
meters
1130 Discussed increase of return
by 10%
1150 Control tests begun
2-13 0800 Ran control tests
ran both flotation thickners
ran vacuum filter
operator instructed to leave
aerator on
1430 RSF adjusted to 440 gpm
control tests run
aerato t]mers recommended
2—14 0840 F]otation thickner &
vacuum filter run all day
1330 Control tests run
RSF adjusted to 410 gpm
Prof. Caponc of 1 ri’ to1
Community College
called to discuss teaching
Al tJest NuLhOd as pan of
a Sanitary Engineering Course

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I I
SETTLED SLUDGE CO CEI1TRATION - SSC
ATC 7dzn
TUBBIDITY AFTER ONE HOUR
H I
— — 3/ 3113 3/193/25 3/31 1 /G /12 /i8 / o
2/li
2/17 2/23 3/1
‘$SV 7dma
900
800
700
I SETTLED SLTJI GE VOLUME
7 dznaI
H
C)
C)
500
16
17
i ’ 4
12
10
8
6
‘4
‘4
3
2
1

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L(GEND
LIQUID FLOW
OL/D$ /
AIR FLOW
£ / 4 t ’ , 1__} f A ‘ - i ) ‘\ 1’
r L 0 V V LI, , ( 7 , ‘ /H I I
.INi L. IJE/V7
OPERATIONS
8 1 / IL

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LEGEND OF NORMAL OPERATiONS
1 Raw Sewage influents (Gravity)
2 Raw Sewage (Force Main)
3 Cesspool Truck Unloading
14 Comminut9r Effluent To Aeration Tanks
5 Aeration Tank Eff1uen To Final Settling Tank
6 Final Settling Tank Effluent To Chlor nation Manhole
7 Chlorine Influent
8 Chlorinated Effluent To Effluent Well
9 Plant Effluent (Force Main)
10 Activated Sludge From Final Settling Tanks
11 Waste Activated Sludge To Thickener Tanks
12 Recirculated Sludge To Aeration Tanks
13 Thickened Sludge To Sludge Well
1 4 Scum Dra i-Off
Scw . And T ckened Sludge Tc CcnciJ ti cr
And \‘a uurn Filter
16 Dried Sludge Conveyor
27 Grit ] c n,rr.i: 1. 4oj ’ r
th Ai r J o Gr t J ernova]. Tatib
A Influent Well
B Raw Sewage Pumps
C Magnetic Flow Meter
D Effluent Well
E Effluent Pumps
F Sludge Flow eters
G Sludge RecLrculation Pumps
H Thickener Tanks
J Sludge Well
K Scum Well
L Scum Pump
M Thickened SJudge Pump
N Ccndit cninpz Thank and
\tacul,J1 fl U cr
‘r
NOTE: Sludge Recirculation Pumps Serve Dual Purpose:
1. Recirculate Sludge To Aeration Tanks
2. Pump Sludge To Thickeners
Discharge Lines Have Motor Operated Plug Valves
To Regulate Flow To Each Unit.
3. Individual Unit Bypass Lines Not Shown

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