Advanced Biological Oxidation of Domestic Sewage with the Use of Compost Beds in a Natural Treatment System for Wastewater

Abstract

Due to the progressing problems with ensuring sufficient quantity and quality of water for municipal, irrigation and economic purposes, the pressure to reuse treated wastewater is increasing. This fact forces the development of advanced systems enabling more effective wastewater treatment. This article presents the results of a 2.5-year study period in which compost beds, which are part of a natural treatment system for wastewater (NTSW), were used to treat domestic sewage by fully removing easily degradable organic matter and by fully nitrifying ammonium nitrogen. It was shown that the compost environment provides complete access to oxygen for the coexisting heterotrophic and autotrophic bacteria, covering 100% of their oxygen demand. Moreover, the outflow of treated wastewater shows an oxygen content of 4–7 g O2/m3. Advanced biological oxidation occurring in the compost beds with an area of 1 m2 per inhabitant and a daily hydraulic load of about 100 L/m2 can effectively and without additional energy expenditure provide a 98% reduction in biological oxygen demand and a 99.5% reduction in ammonium nitrogen. In addition, the effluent from the compost filters meets the most stringent quality criteria for (1) treated wastewater used for irrigation and (2) bathing water in terms of microbiological contamination.