污泥厌氧/好氧消化过程对泥中水形态分布及其脱水性能的影响研究

Influence of anaerobic/aerobic digestion process on moisture distribution and dewatering performance in sludge

以污泥中水的4种形态(重力水、封闭水、包裹水、结合水)含量变化为评价指标,探讨厌氧消化(Anaerobic digestion,AAD)和好氧消化(Aerobic digestion,AD)两系统处理过程中污泥所含水的形态变化及其对污泥脱水性能的影响.结果表明:处理前污泥结合水含量约占污泥总水分的3.5%,其含量几乎不随消化过程而产生改变.污泥厌氧酸化阶段由于污泥絮体中有机酸降解反应消耗了重力水及包裹水,使该阶段脱水性能下降;气化阶段由于产甲烷代谢反应及污泥絮体结构的破坏使重力水含量上升,此时污泥比阻(SRF)降低了36.5%.而污泥好氧的升温和降解阶段均伴随细胞裂解释放的蛋白酶对水与亲水性胶体结合能力的削弱,以及大分子有机物向小分子有机物的转化,使重力水含量增加了15.15%,封闭水含量下降了16.16%,污泥脱水性能提高,此时SRF下降了44.44%.相比于AD,AAD过程中各水形态含量和污泥胞外聚合物(EPS)各组分之间无显著相关性,而AD处理后的污泥紧密层EPS(TB-EPS)中多糖含量与封闭水含量呈正相关(r=0.628),表明污泥好氧消化过程中TB-EPS中多糖的降解更有助于封闭水的释放,从而改善污泥脱水性能.当消化进入稳定阶段,粒径和分形维数的减小可能是造成后期脱水性能差的主要原因.

In this paper,the content changes of the four forms of water in the sludge(gravity water,pent-up water,coating water,and bounding water)were used as evaluation indicators,and the morphological changes of water content in sludge and their effects on sludge dewatering performance in the process of anaerobic digestion and aerobic digestion are discussed.Results show that the bounding water content in the two systems accounts for about 3.5%of the total sludge moisture,and its content hardly changes with the digestion process;In the acidification stage of AAD,gravity water and coating water were consumed by the organic acid degradation reaction in the sludge floc,which reduced the dehydration performance at this stage;During the gasification stage,the gravity water content increased due to the methanogenesis metabolic reaction and the destruction of the sludge floc structure,and the SRF decreased by 36.5%at this time.The heating and degradation stages of AD were accompanied by the weakening of the binding ability of water and hydrophilic colloids by proteases released by cell lysis,and the conversion of macromolecular organic matter to small molecular organic matter,which increased the gravity water content by 15.15%and decreased the pent-up water content by 16.16%,thereby improving the sludge dewatering performance.At this time,SRF dropped by 44.44%.Compared with AD,there was no significant correlation between the content of various water forms and the components of sludge EPS during the AAD process,while the polysaccharide concentration in the sludge compact layer EPS(TBEPS)after AD treatment was positively correlated with the pent-up water content(r=0.628),indicating that the degradation of polysaccharides in TBEPS during AD of sludge was more conducive to the release of pent-up water,thereby improving sludge dewatering performance.When the digestion entered a stable stage,the decrease in particle size and fractal dimension may be the main reason for the poor dewatering performance in the later stage.