Sludge granulation during anaerobic treatment of pre-hydrolysed domestic wastewater

Abstract

The aim of this study was to examine sludge granulation during the anaerobic treatment of pre-hydrolysed municipal wastewater. The pretreated wastewater had a total chemical oxygen demand (CODt) of 432 ± 20 mg/l, a soluble COD (CODs) of 259 ± 8 mg/l, volatile fatty acids (VFA) of 101 ± 9 mg/l and suspended solids (SS) of 94 ± 12 mg/l. Prior to entering the digester, the influent was supplemented with sucrose, which increased the total and soluble COD by 300 mg/l. An upflow anaerobic sludge bed (UASB) digester was operated at different hydraulic retention times (HRT) ranging from 26.7 h to 2.2 h, while the organic load rate (OLR) ranged from 0.9 to 7.3 kgCOD/m 3 ·d. Sludge granulation was observed after day 150 of operation, at an HRT of 3.4 h, when small granules of less than 2 mm in size appeared. The granules had a weak structure and low density, with the specific methanogenic activity of the sludge being about 0.24 g CH 4 -COD/gVSS·d. After granulation, the digester performance was 57% CODt removal and 76% CODs removal for steady state operation at an HRT of 3.4 h and an OLR of 5.6 kgCOD/m 3 ·d.

Treatment of domestic wastewater using upflow anaerobic sludge blanket reactor

“…Gas production rates were highly variable due to the fluctuation of organic concentration in the influent. Maximum gas production (7080 mL/day) was recorded at a HRT of 3.3 h. The present values are relatively higher than those reported by earlier workers (Kobayashi, et al, 1982;Ligero and Soto, 2002). Higher volumes of biogas recorded during the present study can be attributed to higher concentrations of organic matter present in the wastewater.…”

“…At different phases, the VFA as acetate in the medium varied from 100 to 165 mg/L. Low VFA levels in anaerobically treated domestic wastewater have been reported by several workers (Kobayashi, et al, 1982;Ligero and Soto, 2002;Elmitwalli, et al, 2002a). VFA has been recognized as one of the important intermediates during the anaerobic digestion (Ahring and Angelidaki, 1997;Wang, et al, 1999) and is considered a central parameter for anaerobic treatment (Ahring and Angelidaki, 1995;Pind, et al, 1999;.…”

Combined Treatment of Domestic Wastewater using Anaerobic and Solar Photocatalytic Treatment

“…The maximum cumulative gas production (3,300 mL) was recorded for cycle 2, and minimum cumulative gas production (1,550 mL day) was recorded for cycle 12. Biogas production was higher than reported by earlier workers (Kobayashi et al 1982;Ligero and Soto 2002). This was due to the presence of high organic content in the domestic wastewater used.…”

Investigating the feasibility and the limits of high rate anaerobic winery wastewater treatment using a hybrid-EGSB bio-reactor

“…This led to a high F:M ratio (∼10 kgCOD kgVSS −1 ); the rationale behind this choice was the promotion of granulation at high ratios as confirmed by Kalogo and Verstraete (2001) and Ligero and Soto (2002). Additionally, this ratio would assist in the investigation of the performance of the inoculum at high loads of organic material (either easily (VFAs) or slowly degradable (particulate) COD).…”