ABSTRACT
This chapter discusses the trickling filter process for the purpose of providing an overall background on the history and development of fixed-film biological treatment systems. The trickling filter process consists of a bed of rocks or synthetic media over which wastewater is uniformly distributed. After a short period of operation, a biological growth develops. The attached film of microorganisms is often defined to contain two distinctly different regions of activity. The effective film depth is that which is in immediate contact with the wastewater. Excess biological growth sloughs from the filter media and is carried out of the process by the wastewater flow. The trickling filter process became readily accepted and widely used because of its simplicity and low operating costs, however, a number of economic and operating problems developed. In the mid-1950s, a synthetic plastic media was developed which promised to solve many of the problems of the trickling filter.
