南方某污水厂UNITANK工艺的活性污泥性状评估

Evaluation of Characteristics of Activated Sludge in UNITANK Process in a WWTP in South China

目前,南方城镇污水处理厂的进水污染物浓度普遍偏低,受此影响经常出现除污效率偏低、活性污泥性状不佳等问题,导致出水水质不稳定。为此,研究了采用UNITANK工艺的南方某典型城镇污水处理厂的处理效果及活性污泥性状。该污水处理厂半年平均进水COD、BOD5、氨氮、总磷浓度分别为78.1、21.88、11.42、1.63 mg/L,平均出水浓度分别为21.0、6.33、1.34、1.12mg/L,除总磷外其他指标均能稳定达到《城镇污水处理厂污染物排放标准》(GB 18918—2002)中的一级A标准。出水总磷浓度高于1.0 mg/L的主要原因可能是上一次污水处理厂停产后对活性污泥系统进行恢复,刻意降低排泥频率导致磷在活性污泥系统中累积。由于长期碳源不足,污泥的VSS/SS和SVI值都偏低,难以观测到钟虫、累枝虫和轮虫,表明污泥系统营养状况不佳,污泥活性并未处于最佳状态。系统内微生物长期处于内源呼吸状态,污泥很有可能处于老化阶段。

The low concentration of pollutants in influent is a common situation in several wastewater treatment plants in South China, which can cause the problems of low removal efficiency of pollutants and poor quality of activated sludge, thereby resulting in unstable effluent quality. The treat- ment efficiency and characteristics of activated sludge in a typical WWTP using UNITANK process in South China were investigated. The average concentrations of COD, BODs, NH3 - N and TP in the influ- ent were 78.1 mg/L, 21.88 mg/L, 11.42 mg/L and 1.63 mg/L respectively, and their average concen- trations in the effluent were 21.0 mg/L, 6.33 mg/L, 1.34 mg/L and 1.12 mg/L respectively. Except for TP, the other major indexes all could meet the first level A criteria specified in the Discharge Standard of Pollutants for Municipal Wastewater Treatment Plant （GB 18918 -2002）. The main cause of TP con- centration higher than 1.0 mg/L might be the accumulation of phosphorus in the activated sludge system caused by deliberately reducing the sludge discharge frequency during the recovery of activated sludge system after the last shut down of the WWTP. Because the concentration of the long-term carbon source was low, the VSS/SS ratio and SVI value were both very low, and it was very difficult to find the Vorticella, Epistylis and Rotifers, which indicated that the nutritional status of sludge system was poor, and the activated sludge was not in the best state. In the system, the microorganisms were in the endogenous res- piration phase, and the sludge was likely to be in the aging stage.