Evaluation Of The Biodegradability Of Modified Collagen Sizing Agent And Modified Collagen Flocculating Agent

Modified collagen paper sizing agent(MCSA), synthesized by modifying collagen extracted from leather solid wastes, had excellent biodegradability in theory. The OECD-301 B and OECD-310 B methods of the organization for economic cooperation and development(OECD) were improved, and named Modified OECD-301 B and Modified OECD-310 B, respectively. Based on BOD5/CODCr, OECD-301 B, OECD-310 B, Modified OECD-301 B, Modified OECD-310 B, ATP test method and comprehen-sive assessment method, with the aid of self-made indicators, the biodegradability of MCSA was evaluated in this study. Additionally, its biodegradability was compared with that of alkyl ketene dimes(AKD) and styrene-acrylic ester copolymer(SAE). Meanwhile, the relationship between molecular structure and biodegradability was studied. The results are as follows:(1) The BOD5/CODCr values of MCSA, AKD and SAE were 0.32, 0.28 and 0.21, respectively, they were biodegradable material, poor biodegradable material and difficult biodegradable material;(2) The biodegradation rate of MCSA, AKD and SAE was 56%~72%, 54%~56%, 48%~49%, respectively in 28 d;(3) The biodegradability of MCSA, AKD and SAE was evaluated from reduction index of the organic material(Modified OECD-310B), the amount of degradation products index(Modified OECD-301B) and the microbial activity(ATP test) by the method of comprehensive assessment(IW index). Their IW index values were 125.37, 81.97 and 61.23, respectively, which were biodegradable material, biodegradable material and difficult biodegradable material. The experimental results obtained by the 7 methods were consistent. And their biodegradation abilities are: MCSA>AKD>SAE, indicating that MCSA is environmentally friend-ly chemical.Cationic collagen copolymer(PCDMC) was synthesized by graft copolymerization of collagen hydrolyzate and cationic monomer methacryloyloxyethyl trimethyl ammonium chloride(DMC), had excellent biodegradability in theory. Based on OECD-301 B 、 OECD-310 B, Modified OECD-301 B, Modified OECD-310 B, ATP test method and comprehen-sive assessment method, with the aid of self-made indicators, the biodegradability of PCDMC was evaluated in this study. Additionally, its biodegradability was compared with that of polyacrylamide(PAM) and poly dimethyl diallyl ammonium chloride(PDMDAAC). Meanwhile, the relationship between molecular structure and biodegradability was studied. The results are as follows:(1) The biodegradation rate of PCDMC, PAM and PDMDAAC was 61%~70%, 35%~39%, 17%~26%, respectively in 28 d;(3) The biodegradability of PCDMC, PAM and PDMDAAC was evaluated from reduction index of the organic material(Modified OECD-310B), the amount of degradation products index(Modified OECD-301B) and the microbial activity(ATP test) by the method of comprehensive assessment(IW index). Their IW index values were 152.57, 67.93 and 40.75, respectively, which were biodegradable material, difficult biodegradable material and difficult biodegradable material. The experimental results obtained by the 6 methods were consistent. And their biodegradation abilities are: PCDMC>PAM>PDMDAAC, indicating that PCDMC is environment-ally friendly chemical.The PCDMC was used to improve sludge dewaterability in sewage plant. The PCDMC’s sludge dewatering performance was studied by four factor: dosages of PCDMC, stirring speed, sludge temperature and sludge p H. At the same time,dewatering mechanism was also studied. The experimental results showed that the best parameters were that the amount of PCDMC was 4 m L/100 m L(the concentration of the PCDMC was 1g/L), the stirring speed was 120 r/min and sludge p H value range was from 6 to 7. The results also indicated that when the sludge temperature was among 5~40 ℃, the higher the sludge temperature the better the dewatering. The flocculation properties of PCDMC and CPAM were quite at the same relative molecular mass. The water content of sludge was decreased from 98.72% to 75.63%, the CODcr of sludge supernatant was decreased from 347.2 mg/L to 104.3 mg/L, the sludge specific resistance was decreased from 2.174×1013 m/kg to 5.273×1011 m/kg. So the PCDMC showed excellent flocculation.