Sewage Reclamation at Golden Gate ParkAuthor(s): Benn MartinSource: Sewage and Industrial Wastes, Vol. 23, No. 3 (Mar., 1951), pp. 319-320Published by: Water Environment FederationStable URL: http://www.jstor.org/stable/25031554 .

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Vol. 23, No. 3 SEWAGE EECLAMATION AT GOLDEN GATE PAEK 319

out and replaced with alcohol or some

other anti-freeze unless the digesters are heated. During the winter months, all valves, seals, and manhole covers

should be checked for gas leaks. A small leak can mean loss of heat if gas is used for heating. Always use a soap solution in testing for gas leaks?

matches cause explosions.

There has been some trouble in the withdrawal of sludge to the drying beds during winter operation. Be sure

all lines have been flushed out and

properly drained to prevent freezing. After sludge is withdrawn to the dry ing beds, the lines should be flushed out and the valves left open part way at each drying bed. Otherwise they will freeze and be inoperable when needed again.

Trickling Filters

Winter operation of trickling filters has caused more trouble than any other

unit and requires more attention. Dur

ing cold weather it is necessary to

prevent pipes and nozzles from freez

ing. Providing bleeder valves in the distributor piping is usually sufficient.

Nozzles that become clogged ought to be cleaned as soon as possible, otherwise

they are liable to freeze. Snow and ice must not be permitted to accumu

late on the filter stone to such an ex tent that the distributor arms will not rotate. Winter troubles resulting from ice formations at the center column of the distributor can be eliminated by plugging the openings nearest the center of each arm. If a dosing tank is used to apply sewage to the trickling

filters, the dosing chambers should be cleaned of accumulations of grease,

slime, and leaves once a week. If these accumulations are not removed, they

will be sucked into the distributor pip ing, the nozzles will become clogged, and freezing will result.

SEWAGE RECLAMATION AT GOLDEN GATE PARK

By Benn Martin

Superintendent, Golden Gate Park Sewage Treatment Plant, San Francisco, Calif.

The sewage treatment plant in San Francisco's Golden Gate Park is a

secondary treatment plant using the activated sludge process preceded by primary treatment, which consists of

screening, grit and grease removal, and

plain sedimentation. There are manu

ally cleaned bar-racks, a by-pass to a sewer which crosses the park, a grit chamber, a flash aeration tank for

grease removal, two rectangular pri

mary settling tanks operated in parallel (by a structural change effected in

1949), two aeration tanks operated in series using spiral flow and tapered air

distribution, and one rectangular final

settling tank. This is followed by a contact tank for final chlorination. There are also two digesters and four

drying beds, although these are not in use.

At the design capacity of 1 m.g.d. the detention period in the primary sedimentation tanks is somewhat more than 2 hr. In the aeration tanks the detention period is approximately 8 hr. The final settling tank has a detention

period equal to that of the primaries; the chlorine contact tank provides a

minimum period of 20 min. for dis infection.

Actually Water Treatment Plant

The plant is unique in that it is situated between a sewer and a sewage treatment plant (Richmond-Sunset plant), and present operating policy makes full use of the advantageous position. All screenings, grit, and

grease are washed through the by-pass into a sewer connected with the sewage treatment plant that normally treats

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320 SEWAGE AND INDUSTEIAL WASTES March, 1951

the sewage of the contiguous area.

Eaw sludge, which is drawn from the

primary sedimentation tanks at 2-hr.

intervals, is sent with sufficient wash water into this same line. The excess

activated sludge also is wasted into this sewer. Thus, all problems normally associated with the disposal of solids are non-existent. This permits all ac

tivity and personnel effort to be di rected toward the production of efflu

ent for use in the irrigation system of the park.

Until 1947, the plant effluent was

used solely for maintaining the level of various lakes in the park. After

July of that year, the installation of a

pump and discharge line on the shore of Elk Lake, which is now used as the

plant reservoir, make it possible to

pump effluent directly into the irriga tion system and Stow Lake, or the park reservoir atop Strawberry Hill. Here, in addition to the distribution system

directly connected to the reservoir, it is possible for a limited amount of plant effluent to enter the line leading to the

waterworks and be pumped, along with well water, into the northeast areas of

the park. These arrangements make

plant effluent available for irrigation in all areas of the park except that one

served by the domestic supply. This latter has a separate system.

The plant effluent is derived from a

sewage which is almost entirely do

mestic. Suspended solids are 250

p.p.m., with a B.O.D. of 350 p.p.m. After primary treatment the settled

sewage has a suspended solids content of 50 p.p.m. and a B.O.D. of 150 p.p.m.

After secondary treatment, both the B.O.D. and the suspended solids are less than 5 p.p.m. in samples taken from the final settling tank.

Chlorination is carefully controlled, and a residual of 2 p.p.m. after the full contact period is maintained. An in

spector from the Department of Pub lic Health samples the water routinely.

The plant effluent meets drinking wa ter standards.

Costs

The cost per 1,000-gal. unit of efflu

ent at the plant is $0.07. Gravity flow

is sufficient to maintain those lakes

which are at a lower elevation. For

irrigation purposes, and for maintain

ing the level of Stow Lake, where a

boating concession has been established, effluent must be pumped from the plant reservoir. The cost of pumping is

$0.04 per 1,000 gal. These costs com

pare with a cost of $0.22 per 1,000 gal. for irrigation water taken from the

distribution system of the domestic sup

ply. Cost data, where indicated, were

taken from a survey based on the 1948

1949 water production. Included in

the annual operating cost was the total

of certain capital improvements made

during that fiscal year.

TIPS AND QUIPS Famous Boat Trip

News of the death on November 24,

1950, of Reuben F. Brown, superin

tendent, Sewer Maintenance Division,

City of Los Angeles, Calif., recalls his

daring 6-mi. boat trip through the

city's outfall sewer from Inglewood to

the sea. Attired in a rubber suit and

gas mask, and using all rubber covered

equipment to prevent sparking in the

explosive sewer atmosphere, Brown

spent a few hours in the sewer line

every day for six weeks. During the

trip he found several breaks in the

huge pipe. As a result of his subse

quent report, thousands of dollars were

expended on repairs, including Con struction of a thick concrete blanket over the outfall.

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