Sixteenth Annual Report of the Green Bay (Wis.) Metropolitan Sewerage District for the YearEnding March 31, 1948Author(s): George MartinSource: Sewage and Industrial Wastes, Vol. 22, No. 1 (Jan., 1950), pp. 116-118Published by: Water Environment FederationStable URL: http://www.jstor.org/stable/25031215 .

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116 SEWAGE AND INDUSTRIAL WASTES January, 1950

averaged 4.7 per cent solids, of which

68 per cent were volatile. This con

stituted a daily digester loading of 591 lb. of solids, or 398 lb. of volatile sol ids. Digestion produced a reduction of 62.2 per cent volatile matter, which

was equivalent to 248 lb. of volatile solids destroyed per day. Unfortu

nately, the gas production is not met ered and must be computed. As a re

duction of 62 per cent of volatile is

efficient digestion, 17 cu. ft. of gas per

pound of volatile matter destroyed has been arbitrarily selected as a conserva

tive estimate for the production at Rochester. Assuming this to be true, the 90,357 lb. of volatile solids digested during the year yielded 1,536,000 cu.

ft. of gas, equivalent to 4,208 cu. ft. per day, or 0.99 cu. ft. per day per capita.

The operating activities were all

routine, with only minor maintenance

problems. The sludge collecting mech

anism, which was reported as being in a very worn condition at the close of

1947, is still in service. It was anticipated that the treat

ment facilities would require a mini mum of time. Consequently, when

planning the year's work the somewhat extraneous but desirable aspects were

considered. Rather extensive concrete work was needed, and an increasing interest in the plant by the public indicated that some serious considera tion should be given to it's aesthetic

appeal. These two objectives were se

lected as the projects for the season.

Operation data for 1948 are sum marized in Table I.

Sixteenth Annual Report of the Green Bay (Wis.) Metropolitan Sewerage District for the Year Ending March 31, 1948 *?2

By George Martin, Chief Engineer and Superintendent

The Green Bay, Wis., sewage treat ment plant, providing primary treat ment with separate sludge digestion and gas utilization, is unusual in that it is one of very few that are com

pletely enclosed in a modern brick structure.

War Surplus Purchases

Several times during the year advan

tage was taken of the opportunity to

purchase, at greatly reduced prices, equipment from the War Assets Ad

ministration. Material so obtained

during the year included a portable 1,500-w. generator, 2 other 1,500-w. generators, 5 portable blowers, 54 wash able air filters, an electric welder, and numerous smaller items. All the

i For previous extracts see This Journal, 13, 3, 587 (1941); 17, 1, 130 (1945); and 18, 6, 1208 (1946).

2 Recipient of FSWA 1949 Hatfield Award for plants between 10,000 and 100,000 popu lation.

equipment was needed and the cost to the District was ridiculously low.

Park Board Agreement

Past practice has been to permit Green Bay City park department em

ployees to use the District's sludge grinder. To relieve the District from

any responsibility in case of accident, an agreement was reached to rent the

sludge grinder for $1 per year, the

park department to assume all responsi bility while so using it.

Labor Distribution

An examination of the labor distri bution schedule, made up from daily reports submitted by each employee, discloses that 77.4 per cent of employ ees' time (other than administrative

personnel) was devoted to only five classes of work. The greatest amount

(36 per cent) was devoted to plant operation; plant repairs and mainte

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Vol. 22, No. 1 EXTRACTS FROM OPERATION REPORTS 117

nance consumed 24.8 per cent; labora

tory was charged with 7.8 per cent; and janitor service and experimental work each required a little more than

4 per cent.

Plant Heating

Previously, almost the entire amount

of heat required by the treatment plant was furnished by reclaiming heat from

the gas engine cooling system. How

ever, this year, due to power shortages and the District's cooperation with the

power company, engine operation was

changed so that both gas engines were

run during the peak load periods and

both units were off during low demand

periods. By so operating, gas was

stored during the low demand periods and utilized during the peak periods. Such procedure helped out on the

power situation but materially affected

the District's heat system. That (is,

during the periods when both engines were in operation more heat than was

actually required was being produced, whereas at other periods no gas engine heat was available. Thus, the coal fired boiler had to be operated at

nearly full capacity. This required a

coal expenditure of $1,622, or about four times as much as had been ex

pended in any previous year. It should be noted, however, that the treatment plant was much better heated than it had ever been before.

Enclosed Clarifiers

It may be of interest to others to learn of the District's experience with enclosed clarifiers. When the first two clarifiers were built they were enclosed in a building having 13-in. solid brick

walls, face brick on the outside, com mon brick on the inside ; with steel window sash, steel roof trusses, precast Haydite roof slabs, and a steel, stucco, and glass skylight. Shortly after these units were placed in operation the paint failed, then the inside com

mon brick started to chip and spall, the structural steel severely corroded, the

steel sash deteriorated to the extent

that they were replaced with glass

block, and the skylight was floored over

to prevent it from falling into the

clarifiers. In an attempt to improve conditions the outside face of the walls

was waterproofed with a transparent solution and the temperature in the

building was maintained above the dew

point. This year the skylight has been

replaced with an all-aluminum and

TABLE IL?Summary of 1947-48 Operat

ing Data, Green Bay (Wis.) Metro

politan Sewerage District

Item Average Rainfall (in.) . 31.27

Tributary population (esti

mated) _. 60,000

Sewage flow (m.g.d.) . 9.05

Storm water by-passed, total

(m.g.). 836.36

Screenings (cu. ft. daily) . 10

Grit (cu. ft. daily) . 31

Raw sludge, total dry solids (lb.) 3,790,264

Dry solids (lb. per day) . 11,050 Volatile dry solids, total (lb.) 2,461,669 Volatile dry solids (lb. per day) 7,177

Sludge gas (cu. ft. per day) :

Produced . 57,233* Consumed . 60,586

Hydrogen sulfide in sludge gas

(grains per 100 cu. ft.) :

Max . 91.9

Min. 13

Digested sludge withdrawn:

Wet sludge, total (cu. yd.)... 7,694 Per cent moisture:

Max. 91.9

Min. 85.8

Volatile matter (%) Max. 48.9

Min. 40.2

5-day B.O.D. (p.pjn.) :

Influent ... 206

Final effluent . 159

Reduction (%) . 22.9 Suspended solids (p.p.m.) :

Influent . 207

Final effluent . 101

Reduction (%) . 51.3

Chlorine :

Total for 5 months (lb.) _ 59,370 Max. p.p.m. fed. 14.8

Electrical energy (kw.-hr.) Produced by plant, total. 726^662 Consumed, total. 948,750

Operating costs ($) Total for year .

64,912.08 Per m.g. 20.91 * Meter error.

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118 SEWAGE AND INDUSTRIAL WASTES January, 1950

glass unit and the walls, steelwork, and floor have been completely sand blasted and the entire building and

equipment painted. In addition, a

ventilating system and unit heaters have been installed.

A second clarifying unit was built about a year after the first one was

placed in operation. To correct the

shortcomings of the first unit, salt

glazed tile was used to line the inside of the walls, structural steel was hot

dipped galvanized, then painted, and the window sash were all of aluminum. The galvanizing and aluminum have stood up exceptionally well, but the

glazed tile are spalling quite badly. Had ceramic glazed tile been used in

place of the salt glazed tile the District would have had an excellent job. As it is, the glazed tile make a less service able wall than the common brick,

which can at least be painted so that it looks good. Nothing can be done,

however, to the spalling tile to preserve them and to make the walls neat ap

pearing.

Conclusions

This, the thirteenth year of treat ment plant operations, was quite typi cal. The flows, both through the plant and the storm-water bypass stations,

were above the preceding year but they were by no means all time highs.

The solids actually removed this

year were about 800 lb. per day more than the previous year, and in total amounted to nearly 1,900 tons (dry

weight) or 51 per cent of the suspended solids carried by the sewage. This

percentage of removal is about 6 per cent less than the previous year, but the records show that more sludge was removed from the elarifiers this year than last year. The difference, no

doubt, is due to testing and calculating errors.

B.O.D. removals are rather low,

primarily because most of the Green

Bay B.O.D. load is in solution and comes from packing plants (blood), dairy waste, and other soluble food

wastes.

A review of the data discloses that

operations were average and about what could be expected of a primary treatment plant on a combined sewer

system.

An effort has been made to gather complete laboratory data so as to de termine how efficient the treatment

process is and to furnish information for the design of a secondary sewage treatment plant, which is in the engi neering contract stage. Come what

may, the District is preparing for com

plete treatment, and when the day ar

rives the District will be ready and

prepared, financially and otherwise.

Operation data for 1947-48 are sum

marized in Table II.

OXYGEN ABSORPTION BY TRICKLING FILTER SPRAY

By Walter C. Anderson

Chemist, City of Brockton Sewage Testing Laboratory, Brockton, Mass.

Little, if any, information is avail

able regarding the amount of oxygen absorbed by the spray from the nozzles

in trickling filter operation. There

fore, when the information developed herein became available as a secondary result of another investigation, it was

thought it might be of interest to other

operators of trickling filter plants.

Sewage as applied to the trickling filter unit of the Brockton, Mass., treat ment plant with very few exceptions contains no dissolved oxygen. In its

passage through the trickling filter, however, it absorbs, on an annual aver

age, about 6.0 p.p.m. of D.O.

To determine how much of the oxy gen absorption is attributable to the

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