NATIONAL FIELD INVESTIGATIONS CENTER
CINCINNATI
AN EVALUATION
OF THE
HAGERSTOWN, MARYLAND
WATER POLLUTION CONTROL PLANT
NOVEMBER 1973
UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF ENFORCEMENT AND GENERAL COUNSEL
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NATIONAL FIELD INVESTIGATIONS CENTER
CINCINNATI
AN EVALUATION
OF THE
HAGERSTOWN, MARYLAND
WATER POLLUTION CONTROL PLANT
Alfred W. West,, Chief
and
Robert J. Touhey, San. Engr-
Waste Treatment Branch
NOVEMBER 1973
UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF ENFORCEMENT AND GENERAL COUNSEL
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TABLE OF CONTENTS
LIST OF TABLES. . . . . . . . . . . . . . . .
SUMMARY. . . . . . . . . . . . . . . . . . .
INTRODUCTION. . . . . . . . . . . . . . . . .
PLANT DESCRIPTION. . . . . . . . . . . . . .
PLANT EVALUATION. . . . . . . . . . . . . . .
PLANT PERFORMANCE. . . . . . . . . . . .
PROCESS LOADINGS.
. " " "
" " " " " " " "
DISCUSSION. . . .
" " " " "
" " " " " " "
RECOMMENDATIONS
" " " " " " " " " " " " " " "
APPENDIX
iii
PAGE NO.
v
1
3
5
9
9
12
21
24
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TABLE NO.
1
2
3
4
5
6
7
8
A-1
A-2
A-3
A-4
LIST OF TABLES
BOD5 AND TOTAL SUSPENDED SOLIDS, mg/1 . . . . . .
BOD5 AND TOTAL SUSPENDED SOLIDS PERCENT REDUCTIONS
INFLUENT FLOW. . . . . . . . . . . . . . . . . .
PRIMARY CLARIFIER DETENTION TIME AND SURFACE
OVERFLOW RATE . . . . . . . . . . . . . . . . . .
AERATION TANK DETENTION TIME . .
.. .. .. .. .. .. .. ..
ORGANIC LOAD TO AERATION TANKS .
.. .. .. .. .. .. .. ..
ESTIMATED AIR SUPPLY TO AERATION TANKS .
.. .. .. ..
FINAL CLARIFIER DETENTION TIME AND SURFACE
OVERFLOW RATE . . . . . . . . . . . . . . . . . .
APPENDIX
ORGANIC LOAD TO AERATION TANKS
LOADING PARAMETER FOR MODIFIED SECONDARY SYSTEM
UNIT CAPACITIES (METRIC)
UNIT CAPACITIES (ENGLISH)
v
PAGE NO.
10
11
13
14
16
18
19
20
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SUMMARY
Representatives of the U. S. Environmental Protection
Agency (EPA) National Field Investigations Center - Cincinnati
visited the City of Hagerstown, Maryland, Water Pollution
Control Plant on May 15, 1973, to observe and evaluate plant
facilities and operation.
Analysis of plant records from January 1972 through
April 1973 indicated that plant personnel had experienced dif-
ficulty in maintaining consistent effluent quality.
Final
effluent biochemical oxygen demand (BOD5) and total suspended
solids (TSS) averaged 19.2 mg/l and 57 mg/l, respectively, in
1972 and final effluent BOD5 and TSS averaged 22 mg/l and 37 mg/l
from January through April 1973.
Analysis of process loadings indicates that some units,
particularly the primary clarifiers, were severely overloaded.
High
organic loads had been imposed upon the secondary system
because of primary system deficiencies.
Both the aeration tanks
and final clarifiers were hydraulically overloaded during periods
of sustained high flow.
Process control had been hampered by an overall lack of
1
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flow meters and controls.
The flow could not be distributed to
the various units to maximize the efficiency of the secondary
system, and return and waste sludge flows could not be accurate.
ly controlled.
Recommendations are presented for both inm~diate and
long-range modifications to improve process control capability,
to increase the capacity of the secondary system, and to
upgrade final effluent quality.
2
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INTRODUCTION
In response to a request by Mr. Herbert M. Sachs,
Director, Water Resources Administration, State of Maryland,
through the U. S. Environmental Protection Agency (EPA)
Region III, representatives of the National Field Investiga-
tions Center - Cincinnati, Waste Treatment Branch, visited the
City of Hagerstown, Maryland, Water Pollution Control Plant on
Mary 15, 1973.
The visit was conducted to observe and evaluate
the operation of the Hagerstown plant in cooperation with the
Maryland Environmental Service's program for resolving waste-
water treatment problems.
Branch personnel inspected the facilities, reviewed the
plant records, and discussed process control methods with plant
personnel.
At the conclusion of the visit, Branch personnel
discussed their preliminary observations with representatives of.
the City of Hagerstown, plant personnel, and others.
Data from the plant records were subsequently analyzed to
determine if modified process control procedures would improve
effluent quality.
The plant records, including BOD5' total suspended solids,
3
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and flow data, used in this analysis were provided by the Plant
Superintendent.
The dimensions and capacities of the various
process units were provided by representatives of J. B. Ferguson
Engineering, Inc. and Associates, consulting engineers for the
City of Hagerstown.
On June 13, 1973, Branch personnel again met with the
Maryland Department of Health and Water Resources Administration
officials and representatives of the City to suggest immediate
and future modifications to improve effluent quality.
4
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PLANT DESCRIPTION
The Hagerstown Water Pollution Control Plant is located
on Antietam Creek, a tributary of the Potomac River, and pro-
vides secondary treatment by the activated sludge process to the
wastes generated by an estimated population of 43,500 people.
Several small industries within the City also discharge waste-
/
water into the collection system.
The treatment plant was constructed in 1924 and has been
expanded several times since then; the most recent expansion was
completed in 1964.
At the time of the inspection, the plant
included the following facilities:
1 - Communitor
1 - Aerated Grit Chamber
1 - Gravity-type Grit Chamber (standby)
2 - Pre-aeration Tanks
2 - Rectangular Primary Clarifiers
1 - Circular Primary Clarifier
2 - Aeration Tanks - 3 compartments each
1 - Aeration Tank - 2 compartments
2 - Square Final Clarifiers
5
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2 - Circular Final Clarifiers
2 - Chlorine Contact Tanks
1 - Gravity Sludge Thickener
2 - Fixed Cover Anaerobic Digesters
2 - Floating Cover Anaerobic Digesters
1 - Sludge Storage/Aerobic Digestion Tank
A detailed list of all units including descriptions and tank
capacities is appended (Tables A-3 and A-4).
The existing plant facilities were designed on the basis of
an average flow of 30,280 cu m/day (8 mgd), but this figure had
often been exceeded because of severe storm water infiltration
throughout the collection system and periodic flow surges from
industrial sources.
In fact, the average raw wastewater flow for
the month of April 1973 was 42,328 cu m/day (11.183 mgd).
~e
City has taken steps to curtail infiltration and, according to
City representatives, the various industries were cooperating in
an effort to eliminate flow surges.
The consulting engineers stated that the plant had also
been subject to some organic load fluctuations and at times ex-
cessive amounts of grease and oils in the -raw waste.
~e con-
sultant also indicated that the major sources of these wastes had
been identified and were complying with the City's request to
6
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pretreat or eliminate such wastes before discharging into the
collection system.
A partial flow diagram, Figure 1, illustrates the various
units and the general flow pattern.
In the primary system the
raw waste is pre-aerated and then settled.
The secondary system
consists of two individual activated sludge systems each of which
has separate final clarifiers and return sludge lines.
The
aeration tanks are equipped with swing-type air diffusers arranged
in a spiral roll configuration.
Some flexibility had been
provided to enable several modifications of the flow pattern
through the compartments of each tank.
Settled sludge from the final clarifiers is returned to the
head of the aeration tanks, and a portion of the return sludge
may also be diverted to the pre-aeration tanks to achieve some
degree of pretreatment of the incoming waste.
Excess sludge is
drawn from each return sludge line to waste to' the primary
clarifiers.
The effluent from the final clarifiers is chlorinated
and discharged into Antietam Creek.
7
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BAR SCREEN
-"0
AERATED
GRIT
REMOVAL
UNIT
GRIT
REMOVAL
UNIT
(STANDBY)
PRE AERATION
.
I
--.1
I '
I I
I t
I
1
I
I
.
L - - - - - -~S-f ------
RAW
TANKS
SERVICE
BUILDING
-- ---_SS..!_- ----I CSF PUMPS
, I 1
_I XSF I. I I
t 1______---_9'f..---_-! I
IRSF 1
I ,. I
"
/
I
I FINAL
\ CLARIFIER
\"1 I
'..... .,...,'"
/- ........,
/ ,
I FINAL"
\ CLARIFIER J
\ .2 ./
'.... ,-
---
-- ----@-
I I
I II:: I
1 ; ~ ! (AERATION
I i:L UN I
! ~. f ~,- i
I ~ ~ I \....- 'AERATION
I if R: I 1
1 I I
I 1
I
I XSF I
----------- I
1 I
. .
CSF - CLARIFIER SLUDGE FLOW (RSF +XSF) : I
RSF - RETURN SLUDGE FLOW -.R.-5£.@-@--_...fSF ---
XSF - EXCESS SLUDGE FLOW TO WASTE I
.
@ - VALVE I
I
.....,
TANK .1 )
.-
,-
.-
,-
~
SLUDGE TO ANAEROBIC
DIGESTION
TANK "'2 )
LEGEND
FIGURE
PLANT SCHEMATIC
HAGERSTOWN WATER POLLUTlON-
CONTROL PL ANT
AERATION
HAGERSTOWN, MARYLAND
(NOT TO SCALE)
TO CHLORINATION FACILITIES
TANK
.3
--:.r---7)-..;.""r"~
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PLANT EVALUATION
Plant Performance
The efficiency of the primary and secondary systems and the
overall plant in removing biochemical oxygen demand (BOD5) and
total suspended solids (TSS) is illustrated in Tables 1 and 2.
In 1972, final effluent BOD5 and TSS averaged 19.2 mg/l and
57 mg/l; the corresponding plant removals were 85 percent BOD5
and 30 percent TSS.
From January through April 1973 final effluent
BOD5 and TSS averaged 22 mg/l and 37 mg/l which represented plant
reductions of 79 percent and 54 percent, respectively. These
data, particularly final effluent TSS, illustrate the difficulty
the' operators had in maintaining satisfactory effluent quality.
The best overall TSS reduction was 80 percent, and the average
effluent TSS exceeded plant influent TSS concentrations in four
of the 16 months analyzed.
The primary treatment system operated inefficiently through-
out this 16-month period.
Primary effluent (PE) monthly average
BOD5 and TSS concentrations were greater than the corresponding
plant influent values in every month except July 1972.
The lack of
efficient primary treatment resulted in high BOD and suspended
9
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TABLE 1
BOD5 AND TOTAL SUSPENDED SOLIDS, mg/l
HAGERSTOWN, MD., W.P.C.P.
Monthly Averages
MONTH BOD BOD BOD TSS TSS TSS
Raw PE FE Raw PE FE
Jan. 1972 187 210 21.1 95 577 96
Feb. 11 118 161 22.3 81 388 89
Mar. " 95 166 20.6 72 246 49
Apr. " 120 204 24.9 75 975 76
May 11 95 201 8.6 67 950 44
JWle " 100 129 14.2 62 1370 88
July 11 70 44 17.4 49 115 29
Aug. 11 147 176 25 78 365 39
Sept. 11 141 142 18.6 102 217 31
Oct. 11 201 226 18.1 120 1563 24
Nov. 11 170 619 14.3 98 2241 72
Dec. 11 82 316 25 72 956 51
AVG. (1972) 127 216 19.2 81 830 57
Jan. 1973 110 361 19 93 1235 45
Feb. 11 95 503 22 60 1749 25
Mar. 11 137 663 19 90 2835 28
Apr. 11 69 295 28 75 853 51
AVG. (1973) 103 456 22 80 1668 37
10
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TABLE
2
BOD AND TOTAL SUSPENDED SOLIDS PERCENT REDUCTIONS
HAGERSTOWN) MJ).) W .P.C .p.
Monthly Averages
* BOD * T S S
MONTH Primary Secondary Plant Primary Secondary Plant
% % % % % %
** 89 83
Jan. 1972 NR 90 NR NR
Feb. " NR 86 81 77
NR NR
Mar. " NR 88 78 80 32
NR
Apr. " NR 88 79 92 NR
NR
May " NR 96 91 95 34
NR
June " NR 89 86 94 NR
NR
,July " 37 61 75 75 41
NR
Aug. 11 NR 86 83 89 50
NR
Sept. 11 NR 87 87 86 70
NR
Oct. " NR 92 91 98 80
NR
Nov. NR 98 92 NR 97 27
Dec. " NR 92 70 95 29
NR
AVG. (1972) NR 91 85 NR 93 30
Jan. 1973 NR 95 83 NR 96 51
Feb. " NR 96 77 99 58
NR
Mar. " NR 97 86 99 69
NR
Apr. 11 NR 91 59 94 32
NR
AVG. (1973) NR 95 79 NR 98 54
*
Combined treatment by preaeration tanks and primary clarifiers.
** Months in which effluent BOD5 and TSS values were greater
No Reduction. than the corresponding influent values.
11
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solids loadings on the secondary system which no doubt affected
overall plant performance.
Process Loadings
The individual process units were evaluated by determining
either the hydraulic or organic load) or both) for each unit.
The monthly average wastewater flows used to calculate the
various process loadings are listed in Table 3.
As noted pre-
viously) the engineer's design capacity for the primary and
and secondary systems was based on an average flow of 30)280 cu m/day
(8 mgd).
The maximum daily flow (not shown in Table 3) recorded
since January 1972 was 60)560 cu m/day (16 mgd) or double the
design capacity.
The primary clarifiers were evaluated by calculating the
hydraulic detention times and the surface overflow rates based
on m8nthly average plant flows.
Although excess sludge was also
pumped to the primary clarifiers) this flow had not been measured
and therefore was not included in this analysis.
As illustrated
in Table 4) the surface overflow rates exceeded the design rate
of 40.7 cu m/day sq m (1)000 gal/day/sq ft) by as much as 100 per-
The increase in primary effluent BOD5 and TSS concentrations
over the plant influent values indicates that significant amounts
cent.
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TABLE 3
INFLUENT FLOW
HAGERSTOWN, MD., W.P.C.p.
Monthly Averages
MONTH INFLUENT FLOW INFLUENT FLOW
(cu m/day) (mgd)
Jan. 1972 21,011 5.551
Feb. " 25,254 6.672
Mar. " 31,154 8.231
Apr. " 29,069 7.680
May " 31,650 8.362
June " 29,705 7.848
July " 28,596 7.555
Aug. " 18,418 4.866
Sept. " 16,366 4.324
Oct. " 15,185 4.012
Nov. " 18,505 4.889
Dec-.. " 33,259 8.787
AVG. (1972) 24,848 6.565
Jan. 1973 34,690 9.165
Feb. " 43,433 11.475
Mar. " 31,120 8.222
Apr. " 42,328 11.183
AVG. (1973)
37,893
10.011
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TABLE
4
PRIMARY CLARIFIER DETENTION TIMES AND SURFACE OVERFLOW RATES
HAGERSTOWN, MD., W .P.C .P.
Monthly Averages
MONTH
Jan. 1972
Feb. "
Mar. 11
Apr. 11
May 11
June 11
July 11
Aug. 11
Sept. It
Oct. 11
Nov. 11
Dec. 11
Detention Time (Hrs.)
(Calculated at Average Flow)
*
Surface Overflow Rate
cu m/day/sq m (gal/day/sq ft)
1.8
2.0
47.3 (1161)
56 .9 (1396 )
70.2 (1722)
65.5 (1607)
71.3 (1749)
66.9 (1642)
64.4 (1581)
41.5 (1018)
36.9 (905)
34.2 (839)
41.7 (1023)
74.9 (1838)
1.6
1.3
1.0
1.1
1.0
1.1
1.1
2.1
1.8
1.0
AVG. (1972)
1.4
55.9 (1373)
Apr.
11
0.8
78.1 (1917)
97.8 (2400)
70.1 (1720)
95.3 (2340)
Jan. 1973
Feb.
11
0.9
0.8
1.0
Mar.
11
AVG. (1973)
0.9
85.3
(2094)
*
Design overflow rate 1)000 gal./day/sq.ft.
14
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of excess sludge were washed out of the primary clarifiers.
~e
overloaded primary clarifiers not only reduced primary treatment
efficiency, they also limited the ability to effectively waste
excess sludge from the secondary system.
TI1e aeration system was evaluated by determining the deten-
tion time provided by the aeration tanks (Table 5), the organic
load imposed on the system (Table 6), and the quantity of air
provided (Table 7).
Each of the two individual secondary systems
was evaluated separately whenever possible.
Return sludge flow
was not
metered, therefore an estimate of 50 percent of the plant
influent flow was used.
~e detention time provided by the combination of Aeration
Tanks Nos. 1 and 2 in parallel averaged as low as 3.5 hours at
flow and 2.35 hours at total flow in February and April 1973.
Since a minimum of six hours at flow and four hours at total flow
are normally required to achieve adequate treatment, these results
indicate that additional aeration tank capacity is needed to
accommodate periods of sustained high flow.
The differences in
the detention times
provided by those systems also indicate that
the flow had not been proportioned between them to fully utilize
the available aeration tank capacity.
TI1e aeration tanks were also organically overloaded.
As
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TABLE 5
AERATION TANK DETENTION TIME
HAGERSTOWN, MD. W.P.C.P.
Monthly Averages
Detention Time(Hrs.) Detention Time (Hrs.)
MONTH (Calculated at Average Flow) (Calculated at Flow + 50% Return)
Tanks 1&2 Tank 3 Tanks 1&2 Tank 3
Jan. 1972 7.9 9.9 5.3 6.6
Feb. " 6.4 8.9 4.3 5.9
Mar. " 5.3 6.9 3.5 4.6
Apr- " 5.8 6.8 3.9 4.5
May " 5.4 6.0 3.6 4.0
June " 5.6 6.7 3.7 4.5
July " 6.0 6.6 4.0 4.4
Aug. " 10.3 8.6 6.8 5.7
Sept. " 11.8 9.3 7.9 6.2
Oct. " 12.6 10.2 8.4 6.8
Nov. " 9.4 9.9 6.3 6.6
Dec. " 4.9 6.4 3.3 4.3
AVG. (1972) 7.6 8.0 5.1 5.3
Jan. 1973 4.6 6.6 3.1 4.4
Feb. 11 3.5 6.1 2.4 4.0
Mar. " 5.4 6.5 3.6 4.3
Apr. " 3.5 6.8 2.4 4.5
AVG. (1973) 4.3 6.5 2.9 4.3
16
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shown in Table 6, the organic load to the aeration tanks fluc-
tuated drastically, and frequently exceeded the design loading of
641 g BOD5/day/cum (40 lb BOD5/day/1000 cu ft).
The magnitude of
those overloads, which were more than twice the design load of
1973, again emphasizes the need for additional aeration tank
capacity.
The quantity of air provided to the aeration tanks was eval-
uated on the basis of both influent flow and BOD5 load (Table 7).
Based on the organic load, the amount of air supplied to the aer-
ation tanks was at times below the minimum desired rate of
62.4 cu m air/kg BOD5 (1000 cu ft air/lb BOD5).
These data
indicate that additional blower capacity may be needed to insure
adequate dissolved oxygen residuals in the aeration tanks at peak
organic loads.
The monthly average surface overflow rates for the final
clarifiers exceeded the design rate of 32.6 cu m/day/sq m
(800 gal/day/sq ft) by as much as 50 percent as shown in Table 8.
Overflow rates of this magnitude indicate that additional final
clarifier capacity is needed to accommodate periods of high flow
and to permit maintenance and repair of individual clarifiers
without degrading effluent quality.
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TABLE 6
*
ORGANIC LOAD TO AERATION TANKS
HAGERSTOWN, MD., W. P . C . P .
Monthly Averages
*
MONTH Based on FE BOD5
Tanks 1 & 2 Tank 3
Jan. 1972 638 (39.8) 511 (31.9)
Feb. II 606 (37.8) 436 (27.2)
Mar. II 760 (47.4) 577 (36.0)
Apr. II 842 (52.5) 721 (45.0)
May II 888 (55.4) 803 (50.1)
June II 555 (34.6) 460 (28.7)
July " 175 (10.9) 159 ( 9.9)
Aug. II 412 (25.7) 494 (30.8)
Sept. II 290 (18.1) 366 (22.8)
Oct. 433 (27.0) 535 (33.4)
Nov. " 1576 (98.3) 1499 (93.5)
Dec. II 1542 (96.2) 1178 (73.5)
AVG. (1972) 726 (45.3) 644 (40.2)
Jan. 1973 1876 (117) 1331 ( 83)
Feb. II 3431 (214) 2004 (125)
Mar II 2950 (184) 2469 (154)
Apr. II 2004 (125) 1042 ( 65)
AVG. (1973) 2565 (160) 1715 (107)
*
Based on FE BOD5'
_1 r' E" ]J;-/<~-r" i -'- . Ie-v 17}
I - (
I
(/ b;; /~Ji y / / 6C{j VtA. Ii- )
18
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TABLE 7
*
ESTIMATED AIR SUPPLY TO AERATION TANKS
HAGE RST OWN, MO., W.P.C.p.
Monthly Averages
. ** ***
cu m Alr/cu m Flow cu m Air/kg FE BOD 5
MONTH (cu ft Air/gal Flow) (cu ft Air/lb FE BOD5)
Jan. 1972 17.2 (2.3) 81.8 (1312)
Feb. " 14.2 (1.9) 88.2 (1414)
Mar. " 12.0 (1.6) 115.3 (1848)
Apr. " 12.7 (1.7) 62.4 (1000)
May " 11.6 (1.55) 57.6 ( 924)
June r: 12.3 (1.65) 95.6 (1533)
July " 12.7 (1.7) 288.8 (4630)
Aug. " 20.2 (2.7) 114.7 (1838)
Sept. " 22.4 (3.0) 157.9 (2532)
Oct. " 23.9 (3.2) 105.9 (1697)
Nov. " 19.8 (2.65) 32.0 ( 513)
Dec. " 11.2 (1.5) 35.5 ( 569)
AVG. (1972) 15.7 (2.1) 103.0 (1651)
Jan. 1973 10.5 (1.4) 29.3 (469)
Feb. " 8.2 (1.1) 16.8 (269)
Mar. " 12.0 (1.6) 17.8 (285)
Apr. " 9.0 (1.2) 29.4 (471)
AVG. (1973) 9.7 (1.3) 23.3 (374)
* Plant personnel estimated that a supply of 255'cu.m/min (9000 cfm) was avail-
able for aeration tanks.
** Minimum desired rate: 7.5 cu.m air/cu.m (1.0 cu.ft. air/gal.)
***
Minimum desired rate: 62.4 cu.m air/kg. BOD5 (1,000 cu.ft. air/lb. BOD)
19
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TABLE 8
FINAL CLARIFIER DETENTION TIME AND SURFACE OVERFLOW RATE
HAGE RST OWN, MO., W .P.C .P.
Monthly Averages
*
Detention Time (Hrs.) Surface OVerflow Rate
MONTH (Calculated at Flow + 5CY/o Return) cu m/day/sq ill (ga1/day/sq ft)
Claro I, 2 & 4 Claro 3 Claro I, 2 & 4 Claro 3
Jan. 1972 2.3 2.4 22.0(54l) 22.4(55l)
Feb. " 1.8 2.2 27.3(670) 24.9(6l2)
Mar. II 1.5 1.7 33.2(8l4) 32.0(785)
Apr. II 1.7 1.6 29.9(734) 32.6(800)
May II 1.6 1.5 32.l(787) 36.8(904)
June II 1.6 1.6 3l.2 (765) 32.8(806)
July II 1.7 1.6 29.0(7ll) 33.3(8l7)
Aug. " 3.0 2.1 l6.9(4l6) 25.8(634)
Sept. " 3.4 2.3 l4.8(363) 23.7(58l)
Oct. " 3.6 2.5 l3.8(339) 2L7(533)
.Nov. " 2.7 2.4 l8.5(453) 22.3(548)
Dec. II 1.4 1.6 35.4(868) 34.3(843)
AVG. (l97:2) 2.2 2.0 25.3(622) 28.6(70l)
Jan. 1973 L3 L6 37.6(924) 33.8(829)
Feb. " LO l.5 49.3(l2ll) 36.5(897)
Mar. " L6 1.6 32.3(792) 34.3(842)
Apr. " LO L7 49.3(l2l0) 32.5(797)
AVG. (l973) 1.2 L6 42.1(l034) 34.3(84l)
*
Design overflow rate: 800 ga1/day/sq ft.
20
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Discussion
The magnitude of the daily flow to the Hagerstown plant
has fluctuated considerably and periods of sustained high flow
have overloaded most of the process units.
The primary
clarifiers in particular were severely overloaded especially
when they were used for excess sludge disposal.
The efficiency of the primary clarifiers cannot be deter-
mined since the influent to these units had not been analyzed
for BOD5 and TSS.
However, primary effluent BOD5 and TSS data
indicate that there were deficiencies in the primary system
(pre-aeration tanks and primary clarifiers).
Primary effluent
BOD5 and TSS concentrations were usually greater than the corres-
ponding plant influent values and this was undoubtedly due to the
additional load imposed on the overloaded clarifiers by the excess
It is apparent from PE BOD5 and TSS data that sig-
nificant quantities of excess sludge had been washed out of the
sludge flow.
primary clarifiers, and consequently the secondary system received
excessive organic loads.
This is particularly evident when the
organic loads to the aeration tanks calculated from primary
effluent BOD5 data (Table 6) are compared to organic loads cal-
culated from plant influent BOD5 data in Table A-l.
noted that this comparison has not been made to minimize the
It must be
21
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importance of primary treatment but it has been made to emphasize
the need for efficient primary treatment and excess sludge
handling facilities to reduce the organic load to the secondary
system.
Based on the primary effluent BOD5 load, the quantity of
air supplied to the aeration tanks (Table 7) was inadequate at
times.
Plant personnel indicated that two blowers capable of
providing an additional 85 cu m air/min (3000 cu ft/min) were
inoperable.
The aeration system should have sufficient air to
accommodate high organic loads if these blowers are made availab~e.
The lack of operational control and flexibility in the
secondary system created overwhelming operational problems.
Flow
meters, control gates, and valves to enable observation and
adjustment of the flow entering the aeration tanks and final
.
clarifiers of the separate secondary systems were not provided.
Therefore, the flow could not be distributed between those
systems to balance the load and maximize treatment efficiency-
Measuring and adjusting return sludge flow is difficult since
flow meters and proper controls were not provided.
All return
pumps were constant speed and adjustments in the flow rate were
made by throttling valves on either the pump intake or discharge
lines.
Since no meters were available only very coarse adjustments
22
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were possible.
Excess sludge was drawn directly from the return sludge
lines to be wasted.
Since separate waste sludge pumps and meters
were not provided, accurate cont~ol of sludge wasting was
difficult.
Although additional facilities may be required to meet
future flow increases, modifications as suggested in the follow-
ing section will provide needed flexibility and may alleviate
operational difficulties.
23
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RECOMMENDATIONS
Based on the previous analysis and discussion, the following
\-
recommendations are made regarding immediate modifications:
1.
The Consulting Engineer should continue with plans to
convert the two rectangular primary clarifiers into
sludge holding/thickening tanks for excess waste sludge.
2.
The circular primary clarifier should be converted into
an additional final clarifier for the existing activated
3.
sludge system.
New pumps for pumping mixed liquor to and' return sludge
from the converted final clarifier should be provided
with variable speed drives.
4.
Meters and control valves should be installed to measure
and control llnxed liquor flow to the converted clarifier
5.
and return sludge flow from the clarifier.
Modification Of the circular primary clarifier piping
should also include plans for its future use as a final
clarifier for an activated sl~dge system utilizing the
existing pre-aeration tanks.
24
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6.
The two blowers, currently out of service, should be
repaired to provide additional aeration capacity.
the existing facilities controllable and more flexible include:
Recommendations for longer range modifications to make
1.
Separate pumps and meters should be installed for excess
sludge wasting.
2.
Meters and valves or gates should be provided to measure
and control:
a.
Sewage flow to each aeration tank.
b.
Return sludge flow to each aeration tank.
c.
Mixed liquor flow to each final clarifier.
d.
Return sludge flow from each final clarifier.
3.
The Consulting Engineer should continue with plans to
install a central meter and control panel to permit remote
adjustment of valves and pumps while observing metered
responses.
4.
The installation of automatic density meter controllers
should be considered to aid in sludge handling.
5.
Plans should be prepared for constructing new primary
sedimentation units to replace the inadequate units which
were recommended for conversion previously.
25
,0 #.
.,p.," .
- ~... ~ ~ ..
'~:_':~:.~5v:. .
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Table A-2 illustrates the various detention times,
loadings, etc., that could be expected if the existing pre-
aeration tanks and circular primary clarifier were converted
into another activated sludge system.
It is apparent from
these data that additional secondary system capacity and control
capability will provide greater flexibility in balancing the
load to the system as well as reducing the magnitude of the
hydraulic and organic loads.
A flow of 37,850 cu m/day (10 mgd),
and an influent BOD5 of 120 mg/l have been assumed.
tions are consistent with recent plant data.
These assump.
26
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APPENDIX
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TABLE A-1
*
ORGANIC LOAD TO AE RAT I ON TANKS
HAGERSTOWN) MD.) W.P.C.p.
Monthly Averages
MONTH
Organic Load) g BOD5/day/cu m(lb ~~D5/daY/1000 cu ft)
. Janks 1 & 2 Tank 3
Jan. 1973
Feb. II
Mar. "
Apr. "
AVG. (1973)
569 (35.5) 455 (28.4)
444 (27.7) 319 (19.9)
434 (27.1) 330 (20.6)
495 (30.9) 425 (26.5)
420 (26.2) 380 (23.7)
430 (26.8) 356 (22.2)
281 (17.5) 255 (15.9)
345 (21.5) 412 (25.7)
290 (18.1) 366 (22.8)
383 (23.9) 475 (29.6)
433 (27.0) 412 (25.7)
401 (25.0) 306 (19.1)
410 (25.6) 374 (23.3)
571 (35.6) 404 (25.2)
646 (40.3) 377 (23.5)
609 (38.0) 510 (31.8)
470 (29.3) 244 (15.2)
574 (35.8) 383 (23.9)
Jan. 1972
Feb. "
Mar. "
Apr. "
May "
June "
July "
Aug. "
Sept. "
Oct. "
Nov. II
Dec. "
AVG.
(1972)
*
Based on Raw BOD5
-------
PARAMETER
TABLE A-2
LOADING PARAMETERS FOR MODIFIED SECONDARY SYSTEM
HAGERSTOWN, MD., W .P.C .P.
SYSTEM
la 2b 3c
20,8l8 (5.5) 9,463 (2.5) 7,570 (2.0)
5.7 6.l 7.6
3.8 4.l 5.0
Avg. Flow to System - cu m/day(mgd)
Aerator Detention Time
@ Flow (Hrs.)
Aerator Detention Time
@ Flow + 5CY/o Return Flow (Hrs.)
Organic Load to Aeration Tanks -
g BOD5/day/cu m
(Lb. BOD5/day/lOOO cu ft)
503 (3l. 4)
470(29.3)
382(23.8)
Clarifier Detention Time
@ Flow + 5CY/o Return Flow (Hrs.)
l.7
l.5
l.4
Clarifier Surface Overflow Rate -
cu m/day/sq m
(gal/day/sq ft)
30.4(745)
36.0(884)
34.2(840)
a)
System l - includes existing Aeration Tanks l & 2 and Final Clarifiers l, 2 & 4 (See Figure l).
b)
System 2 - includes existing Aeration Tank 3 and Final Clarifier 3 (See Figure l).
c)
System 3 - would include the existing Preaeration Tanks as the Aeration Tanks and Primary
Clarifier 3 as the Final Clarifier modified as suggested in the Recommendations.
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UNIT NO. REMARKS Dn~NSIONS, Meters SURFACE AREA s'l m VOLUME cu m
Per Unit Total ?er Unit Total
Grit Chamber 1 Aerated 5.49 L x 4.88 W x 3.87 D 26.79 S'l m 26.79 sq m 103.6 cu m 103.6 cu m
1 Gravity ( Standby) 5.49 L x 5.49 W x 0.61 D 30.14 30.14 18.39 18.39
Preaeration Tanks 2 Diffused Air, Spiral-
roll Plug F1mf 28.96 L x 9.14 W x 4.57 D 264.69 sq m 529.38 sq m 1209.63 cu m 2419.26 cu m
Primary Clarifiers 2 Rectangular 22.86 L x 4.88 W x 3.05 D 111.56 S'l m 223.12 s'l m 3lfO .26 cu m 680.52 cu m
1 Circular, Center Fed 16.76 Dia. x 3.05 SWD 220.62 220.62 673.73 673 .73
Aeration Tanks 2 3 Compartments per Tank 37.19 L x 4.88 W x 4.57 D 181.49 S'l m 1088.94 sq m (29.41 cu m 4976.46 cu m
Diffused Air, Spiral Roll (each compartment) (each compartment) (each compartment)
1 2 Compartments, Diffused
Air, Spiral Roll 28.96 L x 9.14 W x 4.57 D 264.69 S'l m 529.38 S'l m 1::09.63 cu m 2419.26 CU ,11
(each compartment) (each compartment) (each compartment)
Final Clarifiers 2 S'luare Surface ,nth Circu-
1ar Floors and Sludge Scrap-
pers) Center Fed 15.24 L x 15.24 W x 3.05 SWD 232.26 S'l m 464.52 sq m 708.39 cu m 1416.78 cu m
1 Circular J C em er Fed,
Suction Sludge Collector 16.76 Dia. x 3.05 SWD 220.62 220.62 673.73 673 .73
1 Circular, Center Fed,
Sludge Scrapper Mechanism 18.29 Dia. x 3.35 SWD 262.73 262.73 880.15 880.15
Chlorine Contact
Tanks 2 6 Compartments per Tank 13.41 L x 18.59 W x 1.52 D 249.29 sq fu 498.58 sq m 378.92 cu m 757.84 cu m
Sludge Thickener 1 Out of Service 6.10 Dia. x 3.05 SWD 29.22 S'l m 29.22 sq m 88.92 cu fu 88.92 cu m
Sludge Digesters 2 Anaerobic, Fixed Cover -'<-
Coil Heated, Gas Mixed 15.24 Dia. x 7.47 SWD N.A. N.A. 1501.38 cu m 3002.76 CLl m
2 Anaerobic, Floating Cover
Coil Heated, Gas Mixed 15.24 Dia. x 6.86 SWD N.A. N.A. 1390.17 2780.34
1 Aerobic Digestion/Holding
Tank, Diffused Air 15.24 Dia. x 7.47 Svill N.A. N.A. 1501.38 1501. 38
TABLE A-3
UNIT CAPACITIES (Metric)
HAGERSTOWN, lID., W .P.C .P.
AUGUST 1973
* Not Applicable.
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TABLE A-4
UNIT CAPACITmS (English)
HAGERSTOWN, 141)" W .P.C .P.
AUGUST 1973
-
UNIT NO. REMARKS DIJvIENSIONS, Feet SURFACE AREA sa ft VOLUME eu ft and/or Gals.
Each Unit Per Unit Total Per !Jni t Tatal
Grit Chamber I Aerated 18' Lx 16' W x 12.7' I 288 sq ft 2<38 sq ft 3658 cu ft 3658 cu ft
I Gravity (Standby) 18' Lx 18' W x 2' D 324 324 " 648 648
Preaeration Tanks 2 Diffused Air, Spiral-
roll Plug Flow 95' Lx 301 W X 15' D 2850 sq ft 5700 sq ft 42750 eu ft 85500 cu ft
or 320,000 gals. or 640,000 gals.
Prilnary Clarifiers 2 Rectangular 75' L x 16' W x 10' D 1200 sq ft 2400 sq ft 12000 eu ft 24000 cu ft
or 90, 000 gals. or 90,000 gals.
I Circular, Center Fed 55' Dia. x 10' SWD 2376 2376 23790 eu ft 23790 cu ft
or 178,000 gals. or 178,000 gals.
Aeration Tanks 2 3 Compartments per Tank
Diffused Air, Spiral Roll 122' Lx 16' W x 15' D 1952 sq ft ll712 sq ft 29280 cu ft 175680 cu ft
(each compartment) (each com- or 219,000 gals. or 1.314 m gals.
partmen t) (each compartment)
I 2 Compartments, Diffused 95' Lx 30' W x 15' D 2850 sq ft 5700 sq ft 42750 cu ft 85500 cu ft
Air, Spiral Roll (each compartment) (each com- or 320,000 gals or 640,000 gals.
partment) (each compartment)
Final Clarifier 2 Square SUI'face ,'lith Circu-
lar Floors and Sludge Scrap-
pers, C enter Fed 50' L x 50' \of X 10' S\1D 2500 sq ft 5000 sq ft 26063 cu ft 52126 cu ft
or 195,000 gals. or 390,000 gals.
I Circular, Center Fed,
Suction Sludge Collector 55' Dia. x 101 SI1D 2376 2376 23790 cu ft 23790 cu ft
or 178,000 gals. or 178,000 gals.
I Circular, Center Fed,
Sludge Scrapper Mechanism 60' Dia. x ll' S\1D 2827 2827 31100 cu ft 31100 cu ft
or 232,700 gals. or 232,700 gals.
Chlorine Contact
Tanks 2 6 Compartments per Tank 44' Lx 611 H :x: 5' D 2684 sq ft 5368 sq ft 100,050 gals. 201,300 gals.
Sludge Thickener I Out of' Service 20' Dia. x 10' 81m 314 sq ft 314 sq ft 23,500 gals. 23,500 gals.
Sludge Digesters 2 Anaerobic, FL,<:ed Cover ,
COlI Heated, Gas Mixed 50' Dia. x 21~.5' S\1D ILA. N.A. 396,660 gals. 793,320 gals.
2 Anaerobic, Floatine; Cover
Coil Heated, Gas Mixed 50' Dia. x 22.5' mID N.A. N .A. 367,280 gals. 734,560 gals.
I Aerobic Digestion/Holding
Tank, Diffused Air 50' Dia. x 24.5' SHD N .A. N.A. 396,660 gals. 3~, 660 sals.
*
Not Applicable.
{.; U.S GOVERNMENT PRINTING OFFICU973- 758-489/1064
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