Research On Advanced Treatment Of Dyeing Wastewater By Coagulation-Dynamic Membrane Filtration

According to the urgent demand of water reuse in dyeing wastewater, this paper studied the advanced treatment of secondary effluent of dyeing wastewater by coagulation-dynamic membrane filtration, which gave reference to application in project.First using ceramic membrane as supporter and kaolin as membraning material, dynamic membrane was prepared for advanced treatment of dyeing wastewater. According to permeating flux and removal rate of COD, affecting factors were mainly discussed. The prepared dynamic membrane was provided with good performances as a result of the optimization of composite conditions by orthogonal design. The majorizied kaolin dynamic membrane was formed by particle size of 6000 mesh and concentration of 0.7g/L in 30 minutes under the transmembrane pressure of O.lMPa at crossflow velocity of lm/s.Operating conditions were also discussed. Theresults showed that the operating conditions of determined dynamic membrane filtration were operation pressure of O.lMPa and crossflow velocity of 1.5m/s.Then the ability of monotonous coagulants to remove COD was investigated. Moreover, different filtration ways of coagulation-dynamic filtration were studied. The results showed that the coagulant of A1₂(SO₄)₃ was better, and the indirect coagulation -dynamic membrane filtration was the best on the part of flux, while the direct way was best for COD removal. At last the direct coagulation-dynamic membrane filtration was regarded as the best one according to the influent quality by comprehensive analysis.The fouling mechanism was also investigated. According to blockage model analysis, direct filtration, dynamic membrane filtration and coagulation-dynamic membrane filtration separately belonged to full blockage filtration, standard blockage filtration and cake filtration in the early filtration stage. According to resistance analysis, the reversible pollution was the main part of total pollution, which could be removed by physical cleaning. Also according to SEM and ICP elemental analysis, the foul mechanism was the blockage of pollutant on the fenestra of dynamic membrane and the cake formation. The polluted ceramic membrane was cleaned by high speed air and water flushing(5min)-water back flushing(5min)- 1%NaClO(60min).As a result the membrane flux would berestored up to 98%.Finally the feasibility of water reuse was studied. It was proved that the permeate liquid quality satisfied the water reclaimed standard and coagulation-dynamic membrane filtration could save much energy compared with direct filtration, which showed good environmental benefits, economic benefits and social benefits.