High biogas evolution of distillery wastewater under potassium toxicity in a three-stage upflow anaerobic sludge blanket

Abstract

This investigation aimed to enhance the methanogenic activity of distillery wastewater containing high potassium (K) content in a mesophilic three-stage upflow anaerobic sludge blanket (UASB). The three-stage UASB could not function at a chemical oxygen demand (COD) loading rate greater than 3 kg/m3d due to the K toxicity, causing system failure. The K concentration in the distillery wastewater was 9000–10,000 mg/L, close to the severe inhibitory range for anaerobes (> 12,000 mg/L). Hence, the wastewater was diluted to reach moderate K toxicity. Surprisingly, the three-stage UASB could function effectively, providing high optimum and maximum COD loading rates (20 and 40 kg/m3d, respectively). This was because the three-stage UASB was regulated under a slow stepwise increase in the COD loading rate to achieve fully adapted anaerobe communities for each COD loading rate. This then led to the high ability to withstand the moderate inhibition of K via the successive development of sludge granules.