Study On The Mechanism And Control Of Membrane Fouling In Advanced Technology For Water Purfication

A handle to the aqueous treatment technique, the technique of filter separating is applied more extensively. The Filter separation process has characteristics blow: the material does not take place to change mutually, the separation coefficient is bigger and being operated in indoors temperature, economizing on energy efficiently. It is a new technique for debasing the crisis of energy and resources, and solving the pollution of the environment what contemporary mankind facing. But one of the critical issues for the successful application of membrane in water treatment is membrane fouling. So, a series of study were conducted as below: the mechanism of ultrafiltration membrane fouling was studied theoretically; in order to prevent RO fouling effectively, contrasting and analyzing between three RO pretreatments systems by direct UF and UF's hybrid processes and general pretreatment process; To the membrane fouling ,the optimal cleaning ways were obtained to UF and RO. The main conclusions of the study are as below:(1)Hollow fiber UF membrane with 104 Da MWCOS was used to filtration experiments of different characters water. It is proved that HAs were found to be the main pollutants attributing to membrane fouling, whereas fouling was alleviated as tubidity coexisted. It is evident that pore narrowing mainly happens in the initial period of a filtration circle, but cake filtration becomes dominant afterwards.(2)The micro-polluted surface water was used as raw water, and be treated by three pretreatment process that prevent RO from fouling respectively. The result show that: all index meet the demand for the quality of RO influent water though the treatment of coagulation-ultrafiltration process.(3)UF membrane in treatment for the micro-polluted surface water was studied. It is proved that the organic matters(incluing microorganism,bacterium) and inorganic matters were found to be the main factors attributing to membrane fouling. The result showed that the organic and inorganic matters were covered each other in the fouled membrane.(4)The optimum parameters of backflushing technology used for UF fouling controlling were obtained. The experiment showed that UF water permeating capability declined with time extension, the critical time is 40min. The optimal approach to control the fouling degree was to periodically backflush the UF membrane at work for 60s at intervals of 40min by water at 0.8MPa pressure difference,which could renew about 60 percent water permeating capacity and need cleaning by chemical methods.(5)The compound cleaning agent was advanced in the first time. The agent was composed by H₂O₂ and citric acid, it could make cleaning high effectively, simply and conveniently and could renew more than 97 percent water permeating capability.(6)To preventing RO membrane from fouling, dosing antiscalant could leave membrane flux depressing. The cleaning with the different version of combination between 1%HCL and 2% Na₅P₃O₁₀ and 0.8%EDTA and 0.1%Tritonx-100 and H₂SO₄(pH=8) in turn had good effect. The membrane character can renew about 90 percent. Yan Dandan(Environment Engineering) Supervised by Vice Professor Xue Gang...