This research describes the feasibility of applying a UASB reactor for the treatment of concentrated black (toilet) water at 25 °C. On average 78% of the influent load of COD at an HRT of 8.7 days was removed. Produced methane can be converted to 56 MJ/p/y as electricity and 84 MJ/p/y as heat by combined heat and power (CHP). Minimum reactor volume at full scale was calculated to be 63L per person (for black water containing 16 gCOD/L produced at 5 L/p/d) and this is more than two times smaller than other type of reactors for anaerobic treatment of concentrated black water.

Source-separated black water (toilet water) containing 38% of the organic material and 68% of the phosphorus in the total household waste(water) stream including kitchen waste, is a potential source for energy and phosphorus recovery. The energy recovered, in the form of electricity and heat, is more than sufficient for anaerobic treatment, nitrogen removal and phosphorus recovery. The phosphorus balance of a UASB reactor treating concentrated black water showed a phosphorus conservation of 61% in the anaerobic effluent. Precipitation of phosphate as struvite from this stream resulted in a recovery of 0.22 kgP/p/y, representing 10% of the artificial phosphorus fertilizer production in the world. The remaining part of the phosphorus ended up in the anaerobic sludge, mainly due to precipitation (39%). Low dilution and a high pH favour the accumulation of phosphorus in the anaerobic sludge and this sludge could be used as a phosphorus-enriched organic fertilizer, provided that it is safe regarding heavy metals, pathogens and micro-pollutants. Keywords anaerobic treatment, black water, biogas production, phosphorus recovery, separation at source, struvite INTRODUCTIONNew sanitation concepts are based on separation at source of household wastewater streams into grey water and black water (faeces and urine) or into grey water, urine and brown water (faeces), and have a large potential to recover the important resources energy, nutrients and 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). The nutrients are largely conserved in the effluent of the anaerobic treatment step. Van Voorthuizen et al. (2008) reported a phosphorus removal of only 5% during anaerobic treatment of black water collected with conventional flush toilets (6L per flush), i.e. 95% was conserved in the effluent. However, for more concentrated black water, collected with vacuum toilets (1L per flush), 40% of the phosphorus was removed when applying UASB-septic tank (Kujawa-Roeleveld et al., 2005).

No abstract

No abstract