Development of novel low-cost sewage treatment system applicable to developing countries

由于缺乏基本的城市污水处理设施，发展中国家大部分城市地区面临着水环境严重恶化的问题。由于财政资源有限，迫切需要一种具有成本效益的污水处理系统技术。在这种实际约束下，厌氧过程可能是最具吸引力的污水处理，因为它比传统的好氧过程具有优势，在不需要曝气和通过生物气体产生能量回收方面受益。然而，厌氧过程有一些弱点。厌氧工艺的出水质量往往不能与活性污泥法的出水质量相比。这就是为什么厌氧过程有时需要后处理以去除残留的有机物和营养物质。本研究提出了一种新的工艺，该工艺由一个UASB预处理装置和以下DHS（下流式悬挂海绵帘）反应器组成，用于在没有外部曝气输入的情况下对UASB出水进行抛光。我们提出的系统安装在一个城市污水处理厂，并通过进行长期实验，以实际污水为饲料，评估其可行性。所提出的整个系统不仅具有优异的有机去除效果，而且在8小时的总HRT下具有优异的硝化效果。微生物分析和DO微电极表明，DHS反应器具有保持高密度生物质和良好的大气吸氧功能。在整个两年的实验期间，我们的系统没有产生污泥。一个简单的模型说明在新系统中没有多余的污泥产生。

Most of urban areas of developing countries are facing severe deterioration of aquatic environment due to shortage of facilities for basic municipal sewage treatment. Because of the limited financial resources, there is a definite need of a cost-effective appropriate technology for sewage treatment system. Under this practical constraint, anaerobic process could be the most attractive for sewage treatment, since it has advantages over conventional aerobic processes, in such points as no need of aeration and energy recovery benefit through bio-gas production. However, anaerobic processes possess some weak points. Effluent quality of anaerobic process is often not comparable with that from activated sludge process. That is why anaerobic process sometimes requires post-treatment for removal of residual organics and nutrients.A novel process, which consists of a UASB pre-treatment unit and the following DHS(Downflow Hanging Sponge-curtains)reactor for polishing up the UASB effluent without external aeration input, was proposed in this study. Our proposed system was installed at a municipal sewage treatment plant site, and its feasibility was evaluated by conducting a long-term experiment with actual sewage as a feed. The proposed whole system verified to perform not only superior organic removal but also excellent nitrification at an overall HRT of 8hrs. Microbial analysis and DO microelectrode showed that the DHS reactor had a function of retaining highly density biomass and excellent oxygen-uptake from atmosphere. Over the whole experimental duration of two years no sludge withdrawal was made in our system. A simple model accounted for no excess sludge production in the new system.