Study On The Treatment Of Rural Domestic Wastewater By Hydrolysis Pond/Trickling Filter/Constructed Wetland

The eutrophic degree of Lake Taihu has descended after the effectual treatment of industry effluence point pollution in the recent years. But the non-point pollution in Lake Taihu area has been the most important one for the pollution contribution with the serious pollution of nitrogen and phosphorus. So the disposition of water circumstance in Lake Taihu area has become the most imperative thing that will be done. This full-scale experimental study belongs to the subject about technology and demonstrative engineering for rural domestic wastewater treatment which is one part of the 863 tasks. Combined with the rural fact complexion, the advanced treatment progress and technology which can treat rural domestic sewage in Lake Taihu area effectively will be provided. With the experimental data, a practical technique of domestic wastewater treatment that can be generalized in rural areas of Taihu valley will be developed, and design criteria and manual of operation related with process will be stipulated for, the optimal running conditions are obtained which can provide the experiences for continued treatment tasks.Based on these, the hydrolysis pond/trickling filter/constructed wetland combined processes for treating rural domestic wastewater are designed. The following conclusions can be arrived at during the practice:1. The trickling filter is suitable for removal of N and organics in rural domestic wastewater due to its excellent performance and its adaptive to the change of the water quality.2. The treatment performance of the trickling filter is influenced by the organic load, hydraulic load, circumfluence ratio, temperature and the height of the filter layer. The best treatment performance of COD and NH4+-N are achieved when the hydraulic load is 4.0～7.0 m3/m2·d and 7.0～8.0 m3/m2·d, the removal rates are 85% and 92%, respectively. The removal rate of TN is over 60% when the circumfluence ratio is 200%.Temperature influences the performance of the trickling filter slightly.3. The analysis through the microorganisms inside the TF indicates that the magnitude of nitrifying bacteria in TF is 109cells/g medium and the delamination distribution cases increase, which is similar to that of the nitrosomonases. The magnitude of nitrosomonases is 108cells/g medium. The reduction of organics occurs mainly in the middle and top of the trickling filter while nitrification occurs mainly in the middle and bottom.4. The constructed wetland has perfect performance in removing of COD and NH4+-N.The main mechanism of nitrogen in wetland systems is nitration and denitrafication. The main mechanism of phosphorus removal is the adsorption and sedimentation by the reaction of wetland bed medium with phosphate in wastewater.5. The trickling filter/constructed wetland combined processes have excellent performance of treating rural domestic wastewater. The removal rates of COD, TN and TP are over 90%, 90%, 95%, respectively. The combined processes provide a successful technology for rural water pollution problem nowadays.