title: Treatment of dairy wastewater by two-stage membrane operation with ultrafiltration and nanofiltration.
abstract: Treatment of dairy wastewater by a two-stage membrane process with ultrafiltration (UF) and nanofiltration (NF) was investigated. The results showed that the flux of UF was higher at pH = 4.6 than that at pH = 8 because the resistance of the fouling membrane was lower at the isoelectric point of protein (pH = 4.6) in UF operation. Protein rejection exceeded 99% by UF + NF operation. Lactose rejections were 98.5 and 54% for UF + NF90 and UF + NF270 respectively. Experiments on membrane cleaning showed that the fouling layer of UF and NF was mainly protein and casein which could be removed by aqueous NaOH with pH = 10. The result of long-term experiments showed that the chemical oxygen demand (COD) of NF90 permeates was below 70 mg/L consistently and the wastewater could be concentrated to 24% by a two-stage membrane process.
authors.affiliation: School of Chemistry and Chemical Engineering, Hennan University of Technology, Zhengzhou, China. ywgong123@yahoo.com.cn
authors.forename: Yan-Wen
authors.initials: YW
authors.lastname: Gong
authors.forename: Hong-Xun
authors.initials: HX
authors.lastname: Zhang
authors.forename: Xue-Ni
authors.initials: XN
authors.lastname: Cheng
mesh_terms: D057219:Biofouling; D057919:Biological Oxygen Demand Analysis; D003612:Dairying; D006863:Hydrogen-Ion Concentration; D007220:Industrial Waste / Q000032:analysis*; D008567:Membranes, Artificial; D036103:Nanotechnology / Q000379:methods*; D012972:Sodium Hydroxide / Q000737:chemistry; D012996:Solutions; D014462:Ultrafiltration / Q000379:methods*; D014865:Waste Disposal, Fluid / Q000379:methods*; D018508:Water Purification / Q000379:methods*
chemical_list: D007220:Industrial Waste; D008567:Membranes, Artificial; D012996:Solutions; D012972:Sodium Hydroxide