Chemical Oxygen Demand Removal in Na₂SO₄ Saturated Wastewater by Cultivable Halotolerant Bacterial Community

Abstract

Industrial wastewater with a high Na 2 SO 4 concentration is characterized by high osmotic pressure and salinity, and requires pretreatment before discharging into central treatment facilities. To date, few studies have addressed the chemical oxygen demand (COD) removal in biotreatment of Na 2 SO 4 wastewater. Here, a novel aerobic system for treating Na 2 SO 4 wastewater was developed based on screening halotolerant bacterial strains. The system maintained a stable COD removal at >90% in saturated concentration (varying from 5 to 40% depending on the temperature) of Na 2 SO 4 for 5 years. Activated sludge was initially constructed by cultured strains of Hyphomicrobium sp. CB03, Dietzia sp. XM15, Staphylococcus sp. T211, Flavobacterium sp. AXY1, Ochrobactrum sp. BY4, Bacillus sp. BYXT, Sphingobacterium sp.YY1, Rhodococcus sp. NH7-4, Stappia sp. HM4, Microbacterium sp. PY3-1, and Pseudomonas sp. MN3-2. Uncultured phylum TM7 was detected in the sludge after acclimatization. The present aerobic cultivable halotolerant bacterial community was successfully applied to large scale removal of organic pollutants in saline wastewater.Abbreviations: BOD 5 , biochemical oxygen demand after five days; CHBC, cultivable halotolerant bacterial community; COD, chemical oxygen demand; DO, dissolved oxygen; HRT, hydraulic retention time; MLSS, mixed liquor suspended solid; SEM, scanning electron microscopy 593