| 英文摘要 |
The purpose of this study is to evaluate the treatment efficiencies and management of 25 wastewater natural purification sites.
1. The treatment efficiencies were evaluated based on the data of the removal rate of BOD, SS,TP and NH4; and their average removal rate was 51.2％, 3.3％, 43.5％ and 50.3％, respectively. The treatment efficiency of BOD, TP and NH4 are similar to the data of other countries; however, the treatment efficiency of SS is lower due to high density of aquatic plants and longer hydraulic retention time.
2. After the completion of surface flow-, subsurface flow-, contact bed- artificial wetland techniques, with operations over 1-year, 2-year, or even beyond the guarantee period, it still functions well.From the data of the natural purification sites from 2004 to 2006, it is clear that the treatment efficiency is increasing; and on the implementation and management of water purification, EPA has made a significant progress.
3. Whether by artificial liner or clay liner, the result for seepage prevention is rather limited. It is recommend that artificial wetland should be constructed in the soil with fine materials; or with the artificial liner or clay liner, below the liner, soil compacting must be implemented and repeated for every 30 cm of soil.
4. On-site investigation of the growth and spatial distribution of pomacea doliodes, rats and mosquito were conducted. They tend to multiply in numbers with water depth lower than 30 cm, longer hydraulic retention time, and overgrowth of aquatic plants. Thus, to manage an artificial wetland, it is necessary to cut the high density of aquatic plants twice a year (May and Nov.) and to trap rats all-year-round thus not to be a threat to public health.
5. It is recommended that at the inlet and outlet of the site to set up water-measuring devices, such as triangular weir, for future management and evaluation purpose.
6. The SS value of several sites is negative, and it is recommended to set up sediment pond for pre-treatment.
7. The smaller the area of surface flow artificial wetland is, the less significant its treatment efficiency is; it is recommended that the area of surface flow artificial wetland should be at least 1 ha.
8. The water quality natural purification technique has been developed and implemented from the country side to the urban area, and contact bed treatment is an option worth considering.
9. It is recommended not to set sites at school or military districts due to its large volume of polluted water and inconvenience to manage.
10. It is recommended to take both the pollutant total load and pollutant removal amount into consideration, not just the latter.
11. The bio-diversity in artificial wetlands is related to the water quality: the cleaner the water is, the higher the Shannon Index is for insects, water birds and frogs; however, it does possess the habitat function in the polluted wastewater treatment artificial wetlands.
The design of water purification technique and its training system is proposed. The scheme and preliminary teaching material for the water quality natural purification technique is presented in the report as well. Based on the results of field survey and evaluation of 25 sites, ‘Guidelines on operations and maintenances on water natural purification technique’ was revised.
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