Experimental Study Of Water Pretreatment By Using Powdered Activated Carbon For Reverse Osmosis

In order to improve the efficiency of absorption and reduce the fouling of membrane, a new technique of water pretreatment by using powdered activated carbon (PAC) for reverse osmosis (RO) is presented. In this new technique, PAC was suspended in water and flocculated with a coagulant. It was found that PAC without coagulant addition was less effective than the PAC adsorption-coagulation integrated system. PAC with coagulant can enhanced adsorption and remove organic components and colloids. PAC can be re-circulated several times, And regenerated after its adsorption capacity totally loses. The use and re-circulation of PAC can improve the efficiency of absorption. A positive side effect is that biologic fouling on RO, which is not degraded in a conventional treatment, is also inhibilate. Re-circulating significantly reduces PAC comsumption.Based on the character of contamination in the waste water, we choose the woody powdered activated carbon with high adsorption capacity and hole rate. According to the degree of contamination of the waste water, the best PAC concentration is40mg/L, and the best contact time is30min; According to the water condition and the request of RO pretreatment, we choose the aluminium sulphate as the coagulant. The best coagulant concentration is15-25mg/L,and the best pH is6.0; The coagulant is better to be added after the PAC in order to avoid the competitive adsorption between each other. According to the process the best results are obtained at PAC concentration40mg/L and3-5re-circulating rate. CODCr is removed about65%. UV254absorbance is reduced by about80%and decolorization rate is90%. No bacteriums are detected; The pre-treated water meets the the request of feed pretreatment of RO. SDI is less than1.5.