LOW-TEMPERATURE ANAEROBIC FILTRATION OF SEPTIC-TANK EFFLUENT

A fourteen-month study was conducted to evaluate and compare the performances of three laboratory anaerobic filters treating septic tank effluent, operating at 5-degrees, 10-degrees, and 20-degrees-C. It was found that the start-up of an anaerobic filter at 20-degrees-C (summer conditions in the Canadian North) is possible with no adverse effects on its future performance. The filter at 20-degrees-C performed better than filters at 10-degrees and 5-degrees-C; the filter at 5-degrees-C was the most affected by operational changes such as changes in HRT. The BOD values of the filter effluent were generally higher than 30 mg/l; in addition, the effluent coliform levels were also high. Thus direct discharge of the anaerobic filter effluent to the surface water may not be generally acceptable especially under low temperature and low filter HRT conditions.