저강도 폐수처리를 위한 생물전기화학시스템

Abstract

Biological treatment of wastewater is an economical green technology, however, the effluent water quality of a biological wastewater treatment facility is affected by the characteristics of hydraulic flow in a reactor, the growth of the microorganisms, driving factors and environmental factors. Hence, the efficiency of wastewater treatment facilities is most likely low and the quality of effluent water does not meet the water quality standards. According to a recent research report, Bioelectrochemical techniques can be reliable for treating wastewater with low concentration of contaminants by applying a small voltage between the anode and cathode in a reactor. In this research, we propose an alternative technology for improving the quality of effluent from a sewage treatment plant, viz, Bioelectrochemical systems. The study contents are as follows

ⅰ) effect of applied voltage, ⅱ) effect of hydraulic retention time, ⅲ) effects of shock loading - flow rate and concentration, ⅳ) validation studies using effluent from sewage treatment plant, ⅴ) optimizing the electrode potential.

Initially, the applied voltage was varied (0.6V and 0.8V) and HRT was maintained at 1 hour, the reactor efficiency was not affected as the COD and T-N removal percentages were 87% and 30% respectively at both the applied voltages. Later, when the HRT was varied (1hr, 30min, 15min), the COD and T-N removal percentages were 87% and 30% respectively irrespective of the applied voltage (0.6V and 0.8V) but when the HRT was 10 min, T-N removal percentage decreased to 23% at both the applied voltages. The concentration of influent was varied (high: 95.7 mg/L COD & 41.6 mg/L T-N, low: 10.0 mg/L COD & 11.1 mg/L T-N) to subject the reactor to shock loading. The reactor required a recovery time of 4 hours for high concentration and 2 hours for low concentration. The recovery time was neither affected by voltage (0.6V and 0.8V) nor HRT (30min, 15min). After recovery from high shock loading, the COD and T-N concentration in the effluent were 10.3 mg/L & 36.3 mg/L, respectively. After recovery from low shock loading, the COD and T-N concentration in the effluent were 5.4 mg/L & 7.0 mg/L, respectively. The reactor was then fed with effluent from Y sewage treatment plant. the effluent contained 11.5 mg/L COD & 14.1 mg/L T-N but after treatment it was reduced to 5.8 mg/L COD & 12.3 mg/L T-N. The electrode potential was also varied to enhance T-N removal using a reference electrode (Ag/AgCl). Anode potential was set to 0.6V but cathode potential was varied (-0.3V & -0.4V). COD removal was not particularly affected by change in cathode potential, although T-N removal percentage increased with increase in cathode potential, viz, 38% at –0.3V and 47.5% at –0.4V.