Septic Tank Efficiency

The convenience of waterborne waste disposal in rural households and the difficulty of providing adequate central sewerage systems for the large populations migrating to urban areas from rural centres led to the widespread use of septic tank systems in North America. It is now estimated that about 50,000,000 America and 4,000,000 Canadians use septic tank systems for household sewage disposal. However, engineers have been too busy with larger treatment works to give attention to the septic system or even to learn what attention is needed. Thus the septic tank systems today are essentially the same in design and construction as they were 40 yr ago. A septic tank performs three main functions: 1. Removes a good portion of the settleable and floatable matter by sludge and scum; 2. effects reduction in settled and floating organic matter, through anaerobic digestion; and 3. acts as storage for the remaining solids till removed. There have been several investigations on the design of septic tanks. The best known studies in the United States were carried out by the United States Public Health Service (USPHS) and by the University of California, 15 yr-10 yr ago. Only a few studies have been carried out on the actual performance of septic tanks. An attempt has been made in this paper to evaluate the efficiency of a rural household septic tank.