An overview on Reduction of Excess Sludge Production in Activated Sludge Systems

One of the most important problems in activated sludge systems, is the excess sludge production in wastewater treatment plants, in which its stabilization and disposal has attracted the most attention to itself. In this research, several procedures to reduce the sludge in aerated systems, especially in activated sludge system is explained. Some of the procedures are 1. Lysis-Cryptic growth which includes alkaline-thermal treatment, ozonation, chlorination, and increasing dissolved oxygen. 2. Maintenance metabolism 3. Uncoupling metabolism 4. Predation on bacteria. Also in this research, for each of the above mentioned procedures, some examples are provided. In some procedures which are most chemically (such as ozonation and uncoupler additions), the amount of excess sludge is reduced to zero. Therefore, the best solution for elimination of excess sludge, has been known as chemical procedures; although economical considerations should always be taken into account.