UASB treatment of p-acetamidobenzene sulfonyl chloride producing wastewater and influence of sulfate

In this work, UASB treatment of p-acetamidobenzene sulfonyl chloride(p-ASC)-producing wastewater with methanol as co-substrate was investigated. The influence of the organic loading rate(OLR) from 2.0 g COD/(L·d) to 24.0 g COD/(L·d) by shortening HRT in a stepwise fashion on the performance of the reactor was firstly evaluated. The optimal OLR at HRT of 0.45 d was found 7. 0 g COD/(L·d) where 76% and 100% removal efficiencies of COD and p-ASC were achieved, respectively. Interestingly, no sulfate was added into the feed, but a certain quantity of sulfate and sulfide was simultaneously generated in the effluent. Secondly, no inhibition to the performance of the UASB was found even at a p-ASC concentration up to 1 100 mg/L when HRT was set as 0.45 d. Thirdly, by introducing the 3 000 mg/L sulfate into the feed resulted in an inhibition of methanogenesis with no obvious suppression of sulfidogenesis. When the sulfate was reduced to 1 000 mg/L, the reactor exhibited a quick recovery after one week.