Material balance and microbial community of activated sludge process with excess sludge minimization stream

为了减少废水处理过程对环境的影响，实现零排放技术，废水处理系统必须能够最大限度地提高废水中有机无机物的矿化度，并最大限度地减少剩余污泥的产生。为此目的，开发了带有污泥消化流的活性污泥法，在该工艺中，部分回流污泥在返回曝气池之前被消化和溶解。这是一个很有前途的过程，但为了系统的实际使用，有必要解决系统中无机组分的积累问题，并确认系统的长期稳定性。本研究以某城市污水为研究对象，在实验室内采用臭氧消化回流污泥的活性污泥法，对不同无机物的物质平衡进行了研究。这项研究的具体目标是通过电感耦合等离子体分析监测进入系统的无机物的行为，并澄清其行为的机理。实验结果表明：1)部分金属如Na不会在系统中积累，而是以可溶的形式进入出水。2)铁、铝等金属在污泥中积累，但经过一段时间后达到饱和；3)锌、铜等金属在整个实验期内继续在污泥中积累。在这些金属中，Fe表现出一种有趣的行为：在Fe的积累达到饱和后，出水中的可溶性Fe浓度增加，这表明存在Fe的再溶解机理。这种铁再溶解的化学机理还有待于进一步研究。

In order to reduce the environmental impact from wastewater treatment processes and to achieve "zero emission" technology, it is very important to have wastewater treatment systems that can maximize mineralization of organic mattes in the wastewater and to minimize the excess sludge production. For such a purpose, the activated sludge process with a sludge digestion stream has been developed, in which a part of the return sludge is digested and solubilized before returning to the aeration tank. This is a promising process, but it is necessary for the purpose of practical use of the system to solve the problem of the accumulation of inorganic components in the system and to confirm the long-term stability of the system. In the present study, an activated sludge process with a return sludge digestion by ozonation was operated in the laboratory with a municipal wastewater and the material, balance of different inorganic compounds was investigated. The specific objective of the study was to monitor the behavior of inorganic matters entering the system by using ICP analysis and to clarify the mechanism of their behaviors. The experimental results indicated that: 1) Some metals like Na did not accumulate in the system and go out in the effluent in the soluble form. 2) Some metals like Fe and Al accumulated in the sludge, but after some time the accumulation appeared to come to a saturation, and 3) Some metals like Zn and Cu continued to accumulate in the sludge throughout the experimental period. Among these metals, Fe showed an interesting behavior: after the accumulation of Fe came to saturation, the effluent soluble Fe concentration increased, indicating there is a mechanism of Fe re-solubilizatlon. It is needed to further investigate the chemical mechanism of this re solubilization of Fe.