Treatment of hypersaline wastewater by a combined neutralization–precipitation with ABR-SBR technique

Inorganic salts prohibit seriously the biological treatment of the wastewater discharged from the production of long-chained dicarboxylic acids from liquid paraffin by microbial fermentation. First, the inorganic salts in wastewater were removed partly by means of neutralization–precipitation. Second, the neutralized wastewater was treated in an anaerobic baffled reactor (ABR) and a sequencing batch reactor (SBR). The digested sludge from the sewage treatment plant was taken as the seed sludge for ABR and the returned sludge for SBR, respectively. After adding glucose and rice-washing water as carbon sources, a sludge free of salt to degrade organic pollutants was cultivated. The sludge samples were observed through fluorescence microscope. It was found that the microorganisms in the SBR sludge are mainly zoogloea with a small quantity of infusorians, while the microorganisms in the ABR sludge are mainly filamentous bacteria and bacillus. More than 90% COD in the wastewater can be removed after the treatment by the neutralization–precipitation combined with ABR-SBR technique.

Research highlights
► A combined technique was used to treat the hypersaline wastewater.
► After treated, the COD removal rate of the wastewater can reach more than 90%.
► The influences of HRT, OLR, pH, temperature on COD removal rate were investigated.
► The results may have implications in studies on wastewater with high salt.