UASB treatment of a highly alkaline fruit-cannery lye-peeling wastewater
Anaerobic treatment of a highly alkaline fruit-cannery lye-peeling wastewater was investigated, using an upflow anaerobic sludge blanket (UASB) reactor. Only a short initialisation period was required before COD reduction and OLR had stabilised at 85 to 90% and 2.40 kgCOD·m -3·d-1, respectively. With subsequent increases in OLR to 8.1 kgCOD·m-3·d-1, the COD reduction remained between 85 and 93% and biogas production peaked at 4.1 ℓ·d-1 (63% methane). COD and reactor pH started to decrease after 111 d. Decreases in gas production were observed by Day 102, decreasing to 2.48 ℓ·d-1 by Day 111 and 0.93 ℓ·d-1 after 129 d. Subsequent reductions in the OLR, by reducing influent COD, had no effect on reactor stability. Loss of reactor performance was ascribed to the accumulation of sodium (potentially > 20 000 mg·ℓ-1) within the reactor biomass, leading to inhibition of methanogenesis.