Treatment of a chocolate industry wastewater in a pilot-scale low-temperature UASB reactor operated at short hydraulic and sludge retention time

• Published in: Water science and technology 2013-01, Vol.67 (6), p.1353-1361
• Main Authors: ESPARZA-SOTO, M, ARZATE-ARCHUNDIA, O, SOLIS-MORELOS, C, FALL, C
• Format: Article
• Language: English
• Subjects: Anaerobic digestion; Anaerobic processes; Anaerobic treatment; Analysis methods; Applied sciences; Biofuels - analysis; Biogas; Biological Oxygen Demand Analysis; Bioreactors; Cacao; Chemical oxygen demand; Chocolate; Correlation analysis; Exact sciences and technology; Food Industry; General purification processes; Hydraulic retention time; Industrial Waste; Influents; Load distribution; Loading rate; Low temperature; Natural water pollution; Organic loading; Performance evaluation; Pilot Projects; Pollution; Pretreatment; Processing industry; Reactors; Removal; Retention; Retention time; Sewage; Sludge; Suspended particulate matter; Suspended solids; Temperature; Temperature effects; Time constant; Upflow anaerobic sludge blanket reactors; Waste Disposal, Fluid; Wastewater; Wastewater treatment; Wastewaters; Water treatment and pollution
• ISSN: 0273-1223; 1996-9732
• DOI: 10.2166/wst.2013.010

The aim of this work was to evaluate the performance of a 244-L pilot-scale upflow anaerobic sludge blanket (UASB) reactor during the treatment of chocolate-processing industry wastewater under low-temperature conditions (18 ± 0.6 °C) for approximately 250 d. The applied organic loading rate (OLR) was varied between 4 and 7 kg/m(3)/d by varying the influent soluble chemical oxygen demand (CODsol), while keeping the hydraulic retention time constant (6.4 ± 0.3 h). The CODsol removal efficiency was low (59-78%). The measured biogas production increased from 240 ± 54 to 431 ± 61 L/d during the experiments. A significant linear correlation between the measured biogas production and removed OLR indicated that 81.69 L of biogas were produced per kg/m(3) of CODsol removed. Low average reactor volatile suspended solids (VSS) (2,700-4,800 mg/L) and high effluent VSS (177-313 mg/L) were derived in a short sludge retention time (SRT) (4.9 d). The calculated SRT was shorter than those reported in the literature, but did not affect the reactor's performance. Average sludge yield was 0.20 kg-VSS/kg-CODsol. The low-temperature anaerobic treatment was a good option for the pre-treatment of chocolate-processing industry wastewater.