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Municipal Wastewater Treatment Plants

General Treatment Process:

Location: 69th St. Wastewater Treatment Plant is located at 2525 S/sg Macario Garcia Houston TX.77020 Owner: City of Houston Plant and Process Overview: Houston's 69th Street Wastewater Treatment Complex is the principal element of an extensive capital improvement program designed to keep pace with the City's rapid growth. The multi-million dollar complex is the largest single project ever undertaken by the City's Public Works Department. It represents a cooperative venture of the City, the Texas Department of Water Resources and the Environment Protection Agency, which is providing 75 percent of the funds. The complex sgnifies the desire of the City to parcitipate in the nation's efforts to protect its water resources by reducing the discharge of pollutants into streams and waterways. Wastewater is received from a 53,500 acre area encompassing the central business district and major shopping centers, industrial and cmmercial districts to the north. One-third of the City's existing and projected population lives in the area. The 69th St. Wastewater Treatment Complex will be one of the most advanced projects of its kind in the world. It will double the City's present sewage treatment capabilities and facilitate the long-range expansion and development of Houston. The 69th St. Complex will reduce pollution by its ability to accommodate all of the wase loads generated within its service area. Further, the plant's process is designed to meet the high quality effluent standards set by the Texas Department of Water Resources for descarges into Buffalo Bayou. The Complex will be Houston's largest wastewater treatment facility and will consist of a 200-mgd, two-stage, pure oxygen activated sludge, advanced wastewater treatment plant and a 125 ton/day sludge processing and disposal plant. The plant is designed to minimize noise, air and water pollution problems. It represents a 400 percent expansion to the existing capacity of the Northside Treatment Facility, which was one of the first activated sludge plants in the United States (1916). The 69th St.Sludge plant will be able to process all of the waste sludge from the Complex's wastewater units. It can also process sludge from a number of the City's other treatment plants. The plant's dried sludge will be shipped to buyers who market it as an organic fertilizer. The selling of dried sludge as a fertilizer has been carried on by the City since 1930. Through conversion into a valuable product, Houston disposes of its sludge by recycling in an evironmentally sound manner. The 69th St, Wastewater Treatment Complex consists of two distinct and operationally integrated facilities - the wastewater treatent and teh sludge disposal plant - both designed to meet federal and state environmetal standards most efficiently and economically. The 69th St. Wastewater Treatment Process Overview The 69th St. Wastewater Treatment Plant will operate through a four-step process: Preliminary treatment, two-stage activated sludge, effluent filtration and disinfection. Briefly, influent enters the plant through a 144-inch diameter trunk sewer into the preliminary treatment area and flows through four mechanically cleaned bar screens for the removal of trash. Grit removal chambers remove sand and similar particles. The wastewater then flows through the two stage activated sludge process where about 96 percent of BODs (Biochemical Oxygen Demand) is removed. The carbonaceous first stage is followed by a nitrification second stage. Pure oxygen from a 300 ton/day cryogenic oxygen generation plant is used in the activated sludge process. The pure oxygen system used in the reactor basins also alleviates odor and air pollution problems, while enhancing theappearance of the facility. The use of pure oxygen also permits greater loading rates per unit of site area. This is only way in which a plant of this capacity could accommodated onto the site. Filtration, the third step, separates out finely divided particles not settled out in the clarifiers. Finally, the flow is disinfected in a chlorine contact basin. After chlorination, dechlorination and foam alleviation, the flows enters Buffalo Bayou through an outfall structure upstream from the Houston Ship Channel Turning Basin. The 69th Street Sludge Disposal Process Overview The 69th St. Sludge Plant will have the capacity of processing all the waste activated sludge produced at the wastewater treatment plant at the rate of 112 tons of dry sludge per day. Over short durations, it can handle peak loads up to 140 tons per day. The sludge is first screened and degritted to remove troublesome materials then concentrated by gravity in thickener basins, before being pumped into the aerobic sludge digester for conditioning and partial stabilization. Sloudge from the digester is pumped to aerated holding tanks and distributed to centrifuges where chemicals are added to make it easier to separate water from solid particles. Dewatered sludge cake is then dried by hot gases, transported to storage buildings and slipped to buyers who market it as an organic fertilizer.