Performance of UASB septic tank for treatment of concentrated black water within DESAR concept

Abstract

Separation of wastewater streams produced in households according to their origin, degree of pollution and affinity to a specific treatment constitutes a starting point in the DESAR concept (decentralised sanitation and reuse). Concentrated black water and kitchen waste carry the highest load of organic matter and nutrients from all waste(water)streams generated from different human activities. Anaerobic digestion of concentrated black water is a core technology in the DESAR concept. The applicability of the UASB septic tank for treatment of concentrated black water was investigated under two different temperatures, 15 and 25 degrees C. The removal of total COD was dependent on the operational temperature and attained 61 and 74% respectively. A high removal of the suspended COD of 88 and 94% respectively was measured. Effluent nutrients were mainly in the soluble form. Precipitation of phosphate was observed. Effective sludge/water separation, long HRT and higher operational temperature contributed to a reduction of E. coli. Based on standards there is little risk of contamination with heavy metals when treated effluent is to be applied in agriculture as fertiliser.

Performance of a lab-scale bio-electrochemical assisted septic tank for the anaerobic treatment of black water

“…Lower H 2 S values in the MEC-septic tank were measured between day 25 to day 60 of phase 1 and during phase 2, they became below detection limits (<2 ppmv). The H 2 S concentrations in the control reactor were as high as 700 ppmv (day [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] and on average about 200 ppmv (day 20-98). …”

“…The combination of an Upflow Anaerobic Sludge Blanket and a septic tank (UASB-septic tank) enhances the contact between the sludge bed and the sewage, increases the removal of suspended solids and allows methanation of dissolved organic compounds [7]. In the context of source separated decentralized water treatment, the UASB-septic tank has been proposed for the treatment of black water as well [6][7][8]. Black water (mainly faeces and urine) has high concentrations of organic material and nutrients, making it a suitable input for anaerobic digestion.…”

ZeroWasteWater: short-cycling of wastewater resources for sustainable cities of the future

“…is excreted and it is assumed that around 80% of the COD ends up in the concentrated line for anaerobic digestion, mainly by the advanced concentration step and with a minor sludge contribution from subsequent biological treatment. f Anaerobic digestion of primary and secondary sludge at 35°C converts around 50% of the COD into biogas (Wett et al, 2007;Siegrist et al, 2008), whereas digestion of black water and kitchen waste can remove up to 70-80% of the COD, even at 25°C (Kujawa-Roeleveld et al, 2005;Meulman et al, 2010), which is in the same order as the digestability of (flocculated) grey water (Elmitwalli and Otterpohl, 2007;Hernandez Leal et al, 2010). A 70% COD conversion from mixed sources was therefore assumed to be feasible at 35°C.…”

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).…”

“…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). …”