基于丝状真菌生物处理改善水热处理污泥滤液性质及脱水性能的机理研究

Hydrothermal treatment has been an effective pre-treatment of sewage sludge because of its simple and high efficiency. Hydrothermal treatment could effectively improve sludge dewaterability and decrease the water content of sludge cake. However, high energy consumption of hydrothermal treatment was inevitably needed to improve sludge dewaterability. And it was also difficult to deal with the sludge leachate because of its high organic matter content and complex components. Meanwhile, the hydrolysis of solid organic matter during the process inevitably reduced the organic matter content of sludge cake which was not beneficial to later utilization. During the fungal treatment of sewage sludge, fungal biomass could increase their biomass by shifting their secondary metabolism by using soluble/insoluble solid of sludge. As a result, the free water was released which enhanced the dewaterability of treated sludge. Meanwhile, filamentous fungi in sludge could entrap solid particles from sludge and compress sludge with their filamentous mycelia, thus modifying the porous structure of biosolids and enhancing the dewaterability and filterability of fungal enriched sludge. In this study, the biological treatment of filamentous fungi on hydrothermal treated sludge was investigated. The present works were to investigate the degradation efficiency of sludge leachate, and to explore the dewaterability improvement of sludge, and to evaluate the ameliorated properties of sludge cake during the fungal treatment on hydrothermal treated sludge. Our purposes in conducting these studies were to understand the mechanisms of fungal treatment on hydrothermal treated sludge, and to provide theoretical basis for the advanced treatment, energy saving and resource utilization of the combined treatment of hydrothermal environment with low energy consumption and fungal treatment on sewage sludge.

水热处理技术因其简单高效等特点，已成为城市污泥的高效预处理技术。水热处理能有效改善污泥脱水性能，降低脱水泥饼含水率。但是水热处理能耗较高，处理后污泥滤液有机浓度高，成分复杂，不易处理。丝状真菌在处理剩余污泥过程中，可利用污泥中的可溶性和不溶性的大分子有机物进行自身生长，此过程可以释放束缚在此类物质中的结合水。同时，丝状真菌能通过菌丝捕获并挤压污泥颗粒，改变污泥的孔洞结构，从而提高污泥脱水性能。本项目从丝状真菌对水热处理污泥的生物处理入手，探究丝状真菌对水热处理污泥滤液的降解机理；探究丝状真菌对水热处理污泥脱水性能的改善机制；研究丝状真菌对脱水泥饼性质的改善效果，逐步阐明丝状真菌对水热处理污泥的生物作用机理，为低能耗水热处理/丝状真菌联合处理技术在城市污泥的深度处理、能耗控制及资源化利用提供理论依据。

本项目通过研究丝状真菌Mucor circinelloides ZG-3对水热处理污泥滤液的降解情况，污泥脱水性能以及脱水泥饼的改善效果，阐明丝状真菌对水热处理污泥的生物作用机理。取得的主要成果如下：（1）研究了水热处理条件对城市污泥性能影响。城市污泥经高能耗水热条件处理后，会降低污泥pH，提高污泥DOM浓度和生物高聚物含量。当水热处理温度超过临界点（170℃）时，才能改善污泥脱水性能。当处理温度低于170℃，主要发生脱羟基反应，而当水热温度达到190℃时，脱羧基反应才开始显著。（2）研究了丝状真菌Mucor sp. ZG-3对水热处理污泥滤液降解情况。确定以120℃/15 min作为最佳低能耗水热处理条件。随着接种量的增加，DOM降解效果逐渐提升。接种量10%，处理时间2天，DOM降解效果达到最佳。丝状真菌能明显降解L-DOM，部分降解M-DOM和H-DOM。丝状真菌对滤液中生物高聚物和腐殖酸都具有明显的降解效果。随着接种量的增加以及处理时间的延长，真菌生物量逐渐增加。（3）研究了丝状真菌改善低能耗水热处理污泥脱水性能。丝状真菌改善低能耗水热处理污泥脱水性能的最佳处理条件为：接种量15%，处理时间2天。随着接种量的增加，过滤脱水体积出现先升高后稳定的趋势，而压缩脱水体积则出现先降低后升高的趋势。随着接种量的增加，过滤阶段和压缩阶段的水分去除速率都随之提升。低能耗水热处理/丝状真菌处理不仅能同时提高污泥过滤阶段和压缩阶段的脱水速率，还能提高污泥脱水程度。（4）研究了丝状真菌改善低能耗水热处理污泥脱水泥饼性质。接种丝状真菌不仅能降低脱水泥饼含水率，而且还能提高脱水泥饼有机质含量。随着处理时间的延长，脱水泥饼中挥发分和固定碳含量都出现增加趋势，说明丝状真菌主要以固定碳形式存在其中。丝状真菌能提高燃烧失重速率，降低燃烧所需温度，改善泥饼的焚烧特性，使其更易于焚烧。原始污泥经水热条件处理后，其能量回收效率会显著降低，不利于作为后期的生物燃料。而低能耗水热处理/丝状真菌处理能提高污泥的能量回收效率，便于后期能源利用。