The Dynamics of Electrochemicals and Microbial Populations during Anaerobic Treatment of Human Urine in Soil Microbial Fuel Cells

Abstract

The dynamics of electrochemicals and microbial populations during anaerobic treatment of human urine in soil microbial fuel cells (MFCs) were investigated. The experimental MFC was supplemented with daily urine input while the control MFC was without urine. During the treatment process, electrochemical and microbiological parameters in effluent of the urine-supplemented MFC were monitored using standard methods. The pH of the urine increased from 5.70 to 7.16 after 15 days of treatment in the urine supplemented MFC. The concentration of phosphorus, potassium, sodium, calcium, magnesium, total nitrogen and total organic carbon of the urine reduced from 0.76 g/l to 0.07 g/l, 1.91 g/l to 0.17 g/l, 2.24 g/l to 0.09 g/l, 0.14 g/l to 0.003 g/l, 0.08 g/l to 0.00 g/l, 8.25 g/l to 0.74 g/l and 7.10 g/l to 0.53 g/l respectively after 15 days of treatment. Furthermore, Open voltage of the urine supplemented MFC ranged from 5.63 V to 10.34 V while Open voltage of the control ranged from 1.84 V to 5.02 V after 15 days of operation. The population of facultative bacteria (FAB) and strict anaerobic bacteria (SAB) ranged from 64.2 x 104 CFU to 36.2 x 104 CFU and 21.2 x104 CFU to 61.3 x104 CFU respectively with time. The urine supplemented MFC performed significantly (p < 0.05) better than the control with respect to voltage output while significantly reduced concentrations of organic carbon, nitrogen and metallic (salt) species were found. Therefore, the soil MFC may be applied as a waste management option to treat human urine while generating electricity before disposal.