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并实现“零排放”技术，具有能够最大限度地矿化废水中的有机物并最小化剩余污泥产量的废水处理系统是非常重要的。为此，已经开发了具有污泥消化流的活性污泥工艺，其中一部分回流污泥在返回到曝气池之前被消化和溶解。这是一种有前途的方法，但为了实际使用该体系，必须解决无机组分在体系中积累的问题，并确认该体系的长期稳定性。在本研究中，活性污泥法与回流污泥臭氧消化在实验室运行的城市污水和物料，不同的无机化合物的平衡进行了研究。研究的具体目的是通过ICP分析监测无机物进入系统的行为，并阐明其行为的机制。实验结果表明：1）某些金属元素如钠在系统中没有积累，而是以可溶态的形式随废水排出。2)铁、铝等金属元素在污泥中有一定的积累，但经过一段时间后达到饱和;锌、铜等金属元素在污泥中持续积累。其中，Fe表现出一种有趣的行为：当Fe积累达到饱和后，出水可溶性Fe浓度增加，表明存在Fe再增溶的机制。铁再增溶的化学机理有待进一步研究。

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.