ABSTRACT
Septic tanks are usually small, rectangular chambers lo cated underground to collect wastewater in urban and rural dwellings where individual households are connected to a single tank or to small municipal and institutional sewage plants. The tank should allow the liquid to be retained at least 24 hours to ensure effective sedimentation of the sewage solids and to permit partial anaerobic decomposition of the organic matter. Both processes take place in the same unit in which two-thirds of the volume is reserved for the storage of accumulated sludge and scum. Effluents leaving the septic tank can be disposed either by seepage pits or in drainfield trenches (Eitan, 1993).
