碱性发酵污泥脱水性能的变化及其原因分析

Change and mechanism of sludge dewaterability during alkaline fermentation

通过控制温度在25℃和35℃,利用Ca(OH)2和NaOH调节碱性发酵过程中pH至10,研究了碱性产酸发酵过程中碱性发酵液脱水性能的变化,并且分析了影响碱性发酵液脱水性能的因素。研究发现NaOH条件下得到的发酵污泥的脱水性能比Ca(OH)2条件下得到的发酵污泥的脱水性能差,同种碱试剂条件下,35℃条件下的发酵污泥脱水性能比25℃条件下差。通过对溶解的蛋白和多糖含量的分析,得出在一定范围内,两者的含量与标准化CST(毛细吸水时间)存在较好的线性关系,并且单位多糖比单位蛋白更能引起发酵污泥脱水性能的恶化。通过对溶解的蛋白多糖结合Zeta电位、平均粒径分析,得出温度和Ca2+可能是引起碱性发酵污泥脱水性能差异的根本原因,Ca2+能中和胶体表面较多的负电荷,在污泥絮体之间起到良好的吸附架桥作用,从而不利于污泥的水解,抑制有机物的溶出,而有利于污泥的脱水。从脱水成本和产酸量综合分析,Ca(OH)2比NaOH更适合作为碱试剂调节pH,25℃条件下更适合作为碱性发酵的温度。

Change of sludge dewaterability during alkaline fermentation was investigated by controlling temperature at 25℃ and 35℃ and using Ca（OH）2 and NaOH to adjust the pH of reactor.The factors influencing dewaterability of alkline fermentation sludge were analyzed.Alkaline fermentation sludge with pH adjusted by NaOH had poorer dewaterability than that with pH adjusted by Ca（OH）2.Dewaterability of the sludge fermented at 35℃ was worse than the sludge fermented at 25℃ using the same alkaline fermentation.The CST（capillary suction time）correlated with the soluble proteins concentration in alkaline fermentation sludge within a certain range and the change of soluble carbohydrates concentration had a more remarkable influence on the CST than proteins.The analysis combining Zeta potential,particle size with soluble carbohydrates and proteins indicated that temperature and concentration of Ca2＋ may be the cause for dewaterability difference of the sludge using different alkaline reagents.Ca2＋ could neutralize more negative charge and act as a better bridging agent between flocs,which may inhibit sludge hydrolysis and dissolution of organics,but improve dewaterability of the sludge.From the angle of dewatering cost and SCFAs（short chain fatty acids）products,Ca（OH）2 is a better alkaline reagent than NaOH to adjust the pH of sludge during alkaline fermentation.