中高分子量聚丙烯酰胺对污泥厌氧消化的影响

市政污水处理厂剩余污泥通常通过脱水和进一步厌氧消化实现减量和资源化。阳离子聚丙烯酰胺(cPAM)是脱水过程中常用的絮凝剂,其对后续厌氧消化性能的影响研究仍不深入。研究发现:中高分子量cPAM会抑制厌氧消化过程中有机质的溶出与水解、产酸和产甲烷效率;且中分子量的cPAM抑制效果更强。添加中分子量cPAM的溶解性蛋白质、多糖和短链脂肪酸(SCFAs)的最高产量比对照组分别降低了22.3%、28.4%和38.6%,添加高分子量cPAM的实验组则分别降低了7.4%、19.4%和25.9%;相应地,添加中、高分子量cPAM污泥的30 d甲烷累积产量为(40.4±1.4),(49.8±1.3) mL CH₄/g VSS,比对照组的(61.0±1.4) mL CH₄/g VSS分别降低了33.7%、18.3%。由此建议剩余污泥脱水过程中,要综合考虑cPAM添加量和分子量对后续厌氧消化性能的影响,以达到效益最佳。

EFFECT OF MEDIUM AND HIGH MOLECULAR WEIGHT POLYACRYLAMIDE ON PERFORMANCE OF SLUDGE ANAEROBIC DIGESTION

Dehydration and successive anaerobic digestion are widely used for the reduction and resource utilization of the excess sludge from municipal wastewater treatment plants. Cationic polyacrylamide(cPAM) is a commonly used flocculant in the dehydration process, and its influence on the performance of subsequent anaerobic digestion is still not well understood. This study found that cPAM with medium and high molecular weight could inhibit the solubilization and hydrolysis of organic matter, and the efficiency of the subsequent acidogenesis and methanogenesis during anaerobic digestion. In addition, the inhibition effect of medium molecular weight cPAM was stronger. Compared with the control, the maximum yields of soluble protein, polysaccharide, and short-chain fatty acids(SCFAs) decreased by 22.3%, 28.4% and 38.6%, respectively, for the digestion of sludge after the addition of medium molecular weight cPAM; while they declined by 7.4%, 19.4% and 25.9% respectively for high molecular weight cPAM. The 30-day cumulative methane production for sludge digestion with medium and high molecular weight cPAM were(40.4±1.4) mL CH₄/g VSS and(49.8±1.3) mL CH₄/g VSS, respectively, which were 33.7% and 18.3% lower than that of the control. The results suggested that the effect of cPAM, including the amount and molecular weight of cPAM, on the performance of subsequent anaerobic digestion should be integrated into consideration in the process of excess sludge dewatering to achieve the best overall benefit.