Turns out there is fascinating precedent for water recycling in Golden Gate Park! The following information is from a paper entitled: “The Beautification and Irrigation of Golden Gate Park with Activated Sludge Effluent,” written in 1937 by Charles Gilman Hyde, Professor of Sanitary Engineering at UC Berkeley, and published in Sewage Works Journal, Vol.9, No.6, Nov.1937 (pp. 929-941).
According to this informative paper, the Golden Gate Activated Sludge Plant was constructed in Golden Gate Park in 1932 to treat sewage effluent for use in irrigation and water features in the western half of the park. Wells that had been supplying water for the park were running low, following an eight-year drought, and could no longer supply enough water to maintain “the wealth of botanical material with which the park [had] skillfully, but laboriously, been planted.” The author noted that “water has always been a relatively costly and at times none-too-abundant item among the city’s public utilities. The long dry seasons with virtually no rainfall compel irrigation. The demand for irrigation becomes more important and the quantitative demands are greater if the soil is exceedingly porous and lacks humus. Such is the case in Golden Gate Park.” (still the case!)
The facility cost an estimated $85,000 to construct and was built,” for the most part, by ‘distressed’ or relief labor” in only five months. (federal stimulus money during the Great Depression?) It was “artistically designed” and landscaped to create “a really beautiful spot and an ornament rather than a disfigurement in the Park.”
The plant received raw sewage from the Lincoln Way main sewer, which collected from an area of about 2.1 square miles (the resident population of this area was estimated to be between 10,000 and 15,000 persons). It was designed for a nominal capacity of one million gallons per day; the output over a period of 18 weeks in 1933-1934 averaged 530,000 gallons per day.
The paper includes tables with analyses of the content of the screened sewage and the effluent before it was chlorinated, including measurements of suspended solids, 5-day B.O.D., alkalinity, grease, chlorides, pH and temperature. There was regular testing for B.coli and the results were deemed negligible. The author concluded that the plant produced effluent that was hygienically safe.
The chlorinated effluent was combined with water from Stowe Lake via “an artificial brook about two-thirds of a mile in length, with numerous cascades and waterfalls” to supply Metson Lake and the Chain of Lakes. Elk and Mallard Lakes were wholly filled with treated recycled water. Water from the plant was also used to irrigate the stadium polo fields. The paper noted that Stowe Lake and other lakes in the park supplied by ground water were already heavily infested with algae, but that the recycled water, high in nitrogen, stimulated the growth of algae even more in the lakes where it was used.
The paper ends with a summary of plans to build another sewage treatment plant (the proposed Richmond-Sunset Sewage Treatment Plant) on a site near the Murphy Windmill, with the capability of supplying 3 million gallons per day of treated effluent. All sludge produced at this proposed plant would be “dried to an acceptable degree of moisture and ground to a consistency suitable for employment as a fertilizer in the parks under jurisdiction of the Park Commission.”
Now that’s recycling!