Produetion Of A Bioflocculantby Enterococcus Faecalis And Its Application To The Removal Of Graphene Oxide From Water

Graphene oxide(GO) has been widely used in electronics, biosensors, pipes and semiconductors for its excellent electrochemical properties. With the enterprise development of GO,the wastewater containing GO are increasingly discharged. According to the present GO production process of China, GO was mainly producted from oxidative graphene by sulfuric acid. The entire production process of GO requires a large amount of water used to flush and remove the sulfuric acid and to make GO into powder byforce shear from water. Therefore, it produced a large number of wastewater containing GO. Because GO has excellent electrical property in the water, so it exit stablely withconcentration of 50mg-100mg/L in the form of nano particles in water. According to previous studies, GO can negatively impact the wastewater microbial communities, because their bacterial metabolic activity are significantly compromised in the presence of GO which indicates that GO can hinder the essential microbial functions in activated sludge processes. Furthermore, the presence of GO in the activated sludge may lead to the decline in BOD5 and depress the removal of nitrogen and phosphorus in the biological treatment process. So it is necessary to achieve the recovery of GO in wastewater by treatment of wastewater containing GO.Bioflocculant is an extracellular biopolymer, which is derived from the natural secretions of bacteria. As the predominant components of bioflocculant are polysaccharide,glycoprotein, protein, and nucleic acid bioflocculation is becoming a popular method for water treatment study. It has advantages of safety, biodegradation and free of secondary pollution risk. Though some studies have reported for the removal of GO from the water with bioflocculation, the research on this area is still limited.Accordingly, the major objectives of this research is to(1) screen and identify a novel bioflocculant-producing strain from active sludge,(2) study various factors affecting bioflocculant production including: carbon source, nitrogen source, initial p H and temperature of incubation,(3) evaluate and optimize the effects of temperature, p H, bioflocculant dosage and flocculation time by response surface methodology,(4) explore mechanisms of flocculation of GO with bioflocculant.