Sludge Dehydrating Reagent Preparation By Grafted Copolymer Of Chitosan And The Sludge Dewatering Ability

Sludge dewatering can effectively achieve the reduction sludge. The dewatering ability of the sludge from the city sewage treatment plant is low. Adding dewatering agent before the dehydration is usually required. The most commonly used dehydration agent is organic synthesis polymer cationic polyacrylamide(CPAM). Although the dehydration effect of CPAM is good, the degradation products and acrylamide are harmful to the environment. Therefore, the preparation of efficient dehydration agent by natural polymers become concerned focus.Two sludge dehydrating reagents CTS-AM-DMDAAC and CTS-St-DMDAAC were prepared by grafted copolymer of chitosan. The synthesis conditions were optimized through the study on graft yield and graft efficiency. Structure of graft copolymer was detected both by the chemical means and the fourier infrared spectrum(FT-IR). It was confirmed that the monomer was successfully grafted to the backbone.The dewatering properties of two copolymers increase as the graft yield increased. Therefore, the paper selected the highest graft yield CTS-AM-DMDAAC and CTS-St-DMDAAC as the sludge dewatering reagents applying to the sludge dewatering. The effect of the two copolymer were better than the graft backbone chitosan. At the optimal dosage of CTS-AM-DMDAAC, the minimum of the sludge cake moisture content was 74.0%; The minimum of specific resistance was 5.04×10¹¹m/kg; The minimum of filtrate turbidity was 9.61NTU. At the optimal dosage of CTS-St-DMDAAC, the minimum of the cake moisture content was 80.1%; The minimum of specific resistance was 6.36×10¹¹m/kg; The minimum of filtrate turbidity was 30.5 NTU. At the optimal dosage of CPAM, the dehydration ability of CTS-AM-DMDAAC was better than CPAM, While at the same dosage, The CTS-St-DMDAAC was worse than the CPAM. The two copolymer of chitosan were technical feasibility to apply in the practice.The graft copolymers were expensive. The poly aluminium chloride(PAC) and the two graft copolymers used as compound reagents in sludge dewatering. Low dosage of the graft copolymers can get a good effect of sludge dewatering. It was estimated that the cost of CTS-AM-DMDAAC was less than CPAM. While the CTS-St-DMDAAC cost more than the CPAM. When PAC as part of the compound reagents, the costs of the two compound reagents were less than the CPAM. The compound reagents could get much better dewatering effect than the CPAM when the cost is slightly higher. The two chitosan copolymer were economic and environmental feasibility when they were combined with the PAC as compound sludge dewatering reagents.