Study On Printing Wastewater For Advanced Treatment By Ceramic Dynamic Membrane

The aim of this paper is to enhance the permeate flux of the ceramic membrane and to lower the operation cost of the membrane equipments, in the area such as advanced treatment of the printing wastewater. By analyzing the advanced treatment of printing wastewater, we proposed a way of ceramic dynamic membrane (CDM) and complex moving bed biofilm reactor (CMBBR) to solve these problems in the application area.Water resource shortage in China is getting more and more serious, which directly influences the sustainable development of our economy. But those high water consumption industries, for example the printing, discharging vast sewage with high turbidity, color and chemical oxygen demand (COD) to pollute environment. So wastewater reuse attracts more and more people's attention. Filter membrane such as nanofiltration (NF) membrane, and reverse osmosis (RO) membrane can remove most of particulates, but their energy-consumption is intensive. By selecting dynamic membrane (DM) as supporters at lower price, the turbidity, color and COD can be eliminated at a certain extent, and the filtrate can be recycled and reused in manufacturing processes with economical factors being taken into account.This paper introduces an approach that is to use powdered activated carbon (PAC) to form DM on the surface of the 19-channel porous ceramic tube as the supporter. The CDM was well-formed after 15min of circulation under the applied pressure of 0.2 MPa and at a cross-flow velocity of 0.75 m/s and PAC dosage of 1.5 g/L.The film-forming mechanism according to the analysis of forces on particles has been formulated and implemented in this thesis. The math model was checked by experimental data in this study. The results demonstrated the former 10 mins is according with middle blocking, while the latter 10-15 mins is according with filtercake blocking. According to the test, filter cake resistance was the main pollution resistance and it was 66.5% of total resistance. The tap water flush technology can control membrane fouling efficiently. When NaOH (0.2 mol/L) and oxalic acid (0.2 mol/L) detergent are applied in turn to clean the contaminative membrane, pure water permeates flux could return to 90% of the originality.Comparing the result of A/O and CMBBR, the latter pretreatment method was best. Animalcule was analyzed by microscope. It confirmed that they might suspend or fix in the reactor. Metazoa was not found.The printing factory effluent contained COD, color and turbidity in the range of 294-412mg/L, 61-83 times and 19-28 NTU, respectively. But the quality of treated water by complete equipment was excellent. The results showed that the COD, color and turbidity removal efficiencies of the permeate were 90%, 95%, and 97%, respectively, which is superior to the return water quality standards of printing and dyeing. It was found that the filtrate could be applied as some processes water of printing. EPS was the significant factor affecting cake layer permeability. The contribution of Proteins to CDM fouling is largest among EPS, while the polysaccharides contribute to filtration fabric DM fouling most. Contaminants on filtration fabric DM surface and CDM surface were analyzed by the scanning electron microscopy and EDX. It confirmed that calcium and magnesium were selectively adsorbed on the membrane surfaces, which result in more membrane fouling. The permeation flux can be recovered by washing with alkali and acid. It is concluded that lower sludge discharge make the complete equipment more competitive.The result shows that CDM was considered as a promising method for purification aimed at reuse of printing wastewater, which resulting in directly environmental and economic benefits.