| Nitrogen and phosphorus removal from wastewater is important to protect the receiving waters from the objectionable aquatic plant growth. Many existing wastewater treatment facilities have been upgraded in recent years to include nitrogen and phosphorus removal.; Biological phosphorus and nitrogen removal has received considerable interest in recent years. Basic benefits reported for biological nutrients removal include monetary savings through reduced aeration capacity, and the obviated expense for chemical treatment.; A suspended growth biological treatment process was designed and operated to achieve high removals of carbon, nitrogen, and phosphorus from municipal and industrial wastewaters without the addition of chemicals; and to develop the biological kinetic coefficients of nutrient removal. The process utilized anoxic, anaerobic and aerobic reactor sequence with sludge return. The influent and return sludge were mixed into the first reactor. In this reactor the anoxic condition was maintained due to high nitrate and DO in the returned sludge. Sixty to eighty percent total nitrogen removal was achieved in this reactor. The contents were continuously discharged into the second reactor that maintained anaerobic condition. Under constant mixing and anaerobic environment complete release of phosphorus occurred as orthophosphate. The flow from the anaerobic reactor was continuously released into the third reactor that maintained aerobic condition. In the third reactor, high removal of carbonaceous material, high-rate biological nitrification, and high soluble phosphate removal occurred. This process eliminated the need for an internal recycle, and total detention time was lower than that for conventional activated sludge.; To determine the biological treatment kinetic coefficients, the mean cell residence, (THETA)(,c) was varied. This was achieved by operating the reactors at six different MLSS concentrations, 5000, 4200, 3300, 2600, 1900, and 1200 mg/l. Each MLSS concentration was maintained for 4 to 5 days after steady state conditions were reached. The biological kinetic coefficients (Y, k(,d),K(,s),k,K(,1)) for removal of BOD(,5). |
