Biological dephosphatization and (de)nitrification

Abstract

A modified activated sludge system is provided wherein wastewater is treated to reduce BOD, nitrogen, and/or phosphorus. The disclosed system features a zone sequence nitrification/denitrification, with nitrification induced by recycling mixed liquor that contains a significant concentration of oxygen and nitrifying bacteria. With a further modification, the main treatment zones of the treatment system are split into two or more parallel treatment trains that are either high-loaded with BOD or low-loaded with BOD. The high-loaded sections facilitate the sludge generation and BOD removal, while the low-loaded sections are operated for nitrification and to enhance the growth of nitrifying bacteria. The parallel treatment zones combine and pass into a final denitrification zone. Phosphorus removal is achieved with phosphate release in a reverse flow regime to the main treatment, and phosphate retention primarily in aerated treatment zones in the main stream of the process. The phosphorus is discarded from the system as sludge.

Dependencies are inferred from the claim text.