ABSTRACT
The most efficient method for eliminating or removing organic material from wastewater is by utilizing biological treatment systems. There are three basic systems most often utilized for this removal: activated sludge, trickling filters, and aerobic oxidation lagoons. The quantity of oxygen that is necessary to oxidize the organic material depends mainly on the biological oxygen demand (BOD) satisfied during the biological treatment process. The amount of new cell material produced per pound BOD added varies with the chemical composition of the substrate. Trickling filters and the activated sludge process are the most commonly encountered biological treatment systems. It is necessary to use primary treatment prior to trickling filtration systems to avoid clogging of filter media. When primary treatment is employed prior to secondary systems, a sludge is produced which is usually disposed of by anaerobic digestion. Primary tanks are utilized in all trickling filter plants and in some activated- sludge plants.
