Nielsen P H, Frølund B, Keiding K
Environmental Engineering Laboratory, Aalborg University, Denmark.
Appl Microbiol Biotechnol. 1996 Feb;44(6):823-30. doi: 10.1007/BF00178625.
Changes in the chemical composition of organic compounds in total activated sludge, activated sludge extracellular polymeric substances (EPS), and sludge bulk water during anaerobic storage (12 days) were studied. The background for the study was that anaerobic storage of activated sludge, which often takes place at wastewater treatment plants before dewatering, causes a deterioration of the dewaterability. The reasons are not known at present, but may be related to changes in exopolymer composition of the flocs. The results showed that a fast decrease in total sludge protein and carbohydrate took place within 3 days of anaerobic storage as a result of degradation processes, which accounted for approximately 20% of the organic fraction. The amount of uronic acids and humic compounds remained almost constant in the sludge. The EPS were extracted from the floc matrix using a cation-exchange resin. In the EPS matrix a similar initial (2-3 days) degradation of proteins and carbohydrate took place, whereas the content of DNA and uronic acids showed minor changes. The extractability of humic compounds increased during the first 3 days of storage. No changes in extractability of the carbohydrate were observed. A fraction of the EPS protein was found to be difficult to extract but was observed to be degraded during the anaerobic storage. The EPS composition was further characterized by high-performance size-exclusion chromatography analysis obtained by on-line UV detection and post-column detection of proteins, carbohydrates, humic compounds and DNA. Four fractions of polysaccharides were found, of which only one was responsible for the decrease in the carbohydrate content observed with storage time. The fraction was presumably of low molecular mass. Humic compounds and volatile fatty acids (acetate and propionate) were released to the bulk water from the flocs during the storage. A possible mechanism to explain the reduced dewaterability developed during anaerobic storage, partly because of the observed changes in EPS, is discussed.
研究了厌氧储存（12天）期间总活性污泥、活性污泥胞外聚合物（EPS）和污泥混合液中有机化合物的化学成分变化。该研究的背景是，活性污泥的厌氧储存（通常在废水处理厂脱水前进行）会导致脱水性能恶化。目前原因尚不清楚，但可能与絮体中胞外聚合物组成的变化有关。结果表明，由于降解过程，厌氧储存3天内总污泥蛋白质和碳水化合物迅速减少，约占有机组分的20%。污泥中糖醛酸和腐殖化合物的含量几乎保持不变。使用阳离子交换树脂从絮体基质中提取EPS。在EPS基质中，蛋白质和碳水化合物也有类似的初始（2 - 3天）降解，而DNA和糖醛酸的含量变化较小。储存前3天腐殖化合物的可提取性增加。未观察到碳水化合物可提取性的变化。发现一部分EPS蛋白难以提取，但在厌氧储存期间被观察到发生了降解。通过在线紫外检测和蛋白质、碳水化合物、腐殖化合物及DNA的柱后检测，利用高效尺寸排阻色谱分析进一步表征了EPS的组成。发现了四种多糖组分，其中只有一种导致了储存期间观察到的碳水化合物含量下降。该组分可能分子量较低。储存期间，腐殖化合物和挥发性脂肪酸（乙酸和丙酸）从絮体释放到混合液中。讨论了一种可能的机制来解释厌氧储存期间脱水性能下降的原因，部分原因是观察到的EPS变化。
