Anaerobic digestion of blackwater from vacuum toilets and kitchen refuse in a continuous stirred tank reactor (CSTR)

Abstract

The objective of this research was mesophilic anaerobic digestion of blackwater from vacuum toilets (BW) and kitchen refuse (KR) in a CSTR within an ecological sanitation system. A detailed investigation of the BW characteristics was carried out. Research on anaerobic digestion was performed with CSTR of 101 volume at HRT of 10, 15 and 20 days. The digestion of BW at 20 days HRT showed stable performance without inhibition effects, in spite of relatively high ammonium concentrations. The removal of total and particulate COD was 61% and 53%, respectively, and the methane yield 10/CH4/cap/day. The addition of kitchen refuse (KR) improved the performance of the CSTR in terms of COD removal efficiency and methane yield. At 20 days HRT the removal of total and particulate COD increased up to 71% and 67%, respectively, and the methane yield to 27/CH4/cap/day. The results at 15 days HRT showed similar performance. At HRT of 10 days, the anaerobic treatment was limited but reached steady state conditions at higher VFA concentrations in the effluent, with a decrease of COD removal of 30 to 33% and of methane yields of 19 to 21%.

Anaerobic Treatment of Concentrated Black Water in a UASB Reactor at a Short HRT

“…Wendland et al [13] investigated anaerobic treatment of black water from vacuum toilets in a CSTR operated at mesophilic conditions (37 °C). A removal efficiency of total COD of 61% was achieved at an HRT (Hydraulic retention time) of 20 days.…”

“…A removal efficiency of total COD of 61% was achieved at an HRT (Hydraulic retention time) of 20 days. Applying a CSTR for anaerobic treatment of black water (7 L/p/d) requires a volume of 140 L per person [13].…”

Energy and phosphorus recovery from black water

“…Anaerobic treatment is regarded as the core technology for energy and nutrient recovery from source separated domestic wastewater (Otterpohl et al, 1999;Kujawa-Roeleveld and Zeeman, 2006). Previous research showed that concentrated black water (faeces and urine collected in a vacuum toilet) can be efficiently treated in a UASB (Upflow anaerobic sludge blanket) reactor at a relatively short hydraulic retention time (HRT) of 9.1 days (de Graaff et al, 2010), in a UASB septic tank at a longer HRT of 29 days (Kujawa-Roeleveld et al, 2005) or in a CSTR at an HRT of 20 days (Wendland et al, 2007). A methane production of 1.8 m 3 CH 4 per m 3 of black water can be achieved, which can be converted to 56 MJ/p/y as electricity and 84 MJ/p/y as heat by combined heat and power (CHP) (de Graaff et al, 2010).…”

Demonstration of Anaerobic Digestion of Black Water for Methane Capture and Use in an Office Building

“…Zeeman et al (2008) demonstrated energy savings by employing this approach compared to traditional methods of wastewater treatment including aeration. Other researchers have operated anaerobic digesters under mesophilic conditions to increase methane generation (van Voorithuizen et al, 2008;Wendland et al, 2007). These researchers demonstrated successful methane generation from BW, with and without addition of kitchen waste, in a continuously stirred tank reactor (Wendland et al, 2007) and a membrane bioreactor (van Voorithuizen et al, 2008).…”

“…Other researchers have operated anaerobic digesters under mesophilic conditions to increase methane generation (van Voorithuizen et al, 2008;Wendland et al, 2007). These researchers demonstrated successful methane generation from BW, with and without addition of kitchen waste, in a continuously stirred tank reactor (Wendland et al, 2007) and a membrane bioreactor (van Voorithuizen et al, 2008). These projects were conducted at the INTRODUCTION laboratory scale with 5-10 L reactors and hydraulic retention times (HRT) varying between 10-20 days.…”