Study On The Degradation Of Pollutants By The Sludge Enriched With Humic Acid Reducing Bacteria

The humic substance is ubiquitous in the biosphere and can be readily isolatedfrom nearly all soil, waters, and sediments. It is not only as redox mediator inbiotransformation of the noxious or innoxious compounds, but also it can accept theelectron from some organic acids or poisonous compounds (e.g., toluene, etc) as thesole electron acceptor, coupled the energy production for cell growth, which isnamed humus respiration. At the same time, noxious compounds are degraded.The anaerobic sludge was sampled from Hang Zhou SiBao wastewatertreatment plant and West Lake sediment for the enrichment of humic acid reducingmicroorganisms. The result of enrichment showed that much humic acid reducingbacteria existed in the sludge. The incubated sludge with formate or acetate hadmore capacity of reducing AQDS. AQDS was a good humic acid analogue forhumus respiration. The results of MPN showed that Microorganisms conservedenergy to support cell growth by humus respiration.The degradation of two organic pollutants by the anaerobic sludge enrichedwith humic acid reducing bacteria was studied. The results show that: 1,4 dioxanecould be removed by two different kinds of enriched sludge, especially when Fe³⁺ asthe electron acceptor. The coexistence of Fe³⁺ and humic acid in anaerobic sludgecould further improve the 1,4 dioxane degradation efficiency. When the enrichedsludge was used for acetaminophen degradation, comparing with common anaerobicsludge, the degradation efficiency with the sludge enriched for one month could beenhanced by 34% in a week, while the sludge enriched for half a year had betterdegradation efficiency which exceeded 90%. The optimal pH for the anaerobicsludge was 7.0. The coexistence of Fe³⁺ and humic acid in anaerobic sludge couldfurther improve the acetaminophen degradation efficiency.The study of Cr⁶⁺ remove was investigated that three ways were useful: one isthe adsorption of sludge, another is direct reduction by microorganisms, the third isAQDS as the electron intermediate for indirect reduction by humus respiration.Whether the SiBao incubated sludge or the West Lake incubated sludge, Cr⁶⁺ couldbe removed continuously once there was enough carbon resource supporting humusrespiration. Cr⁶⁺ was reduced to Cr³⁺, then could be removed from water byprecipitation. But when the concentration of Cr⁶⁺ was over 20mg/L, the humusrespiration was inhabited.