Effects of different carbohydrate growth substrates on anaerobic hydrolysis–aerobic cometabolism treatment of cutting fluid wastewater

ABSTRACT

Using real cutting fluid wastewater pretreated by oil separation and coagulation, this study explored the influences of carbohydrate growth substrates (glucose, sucrose, and starch) on the cometabolic performance, metabolic activity, and sludge settleability of aerobic reactors. The results indicated that under similar organic loading rates, the sludge volume index (SVI) was higher in aerobic reactors fed with more refractory cutting fluid wastewater or starch as growth substrate than in aerobic reactors fed with glucose or sucrose as growth substrate. All three carbohydrate growth substrates at volumetric ratios (growth substrate/anaerobic hydrolysis effluent) of 1:1, 3:7, and 1:4 in the aerobic reactors could elevate the dehydrogenase activity (DHA) of mixed liquor and facilitate cometabolism of refractory organics in real cutting fluid wastewater. As growth substrate content decreased in the aerobic reactor influent, the occurrence of the peak DHA in the aerobic reactor was delayed. DHA content was not only positively correlated with the growth substrate content, but also related to the metabolic complexity of the growth substrate. Considering cometabolic performance as well as SVI and DHA in the aerobic cometabolism reactors, sucrose was the preferred growth substrate, and the optimal volumetric ratio of growth substrate to anaerobic hydrolysis effluent in the influent was 1:1.