| As the population increasing, the urbanization exalting and the national economy developing, the degree of the destructive exploitation of natural resources is being deepen, making the environment rapidly worsened, especially, the water bodies have been seriously contaminated because the wastewater without being disposed poured directly into lakes, rivers and so on, besides, the pollution would make our environment deteriorated and retard the fast development of the society and economy. So, purifying and controlling polluted water has become one of the important aspects of the harnessing environment. But, in current our country' s economic strength is not strong, especially, the level of the economy development in the town of middling or small size is not high, the sources of energy run short and few technician, so it is difficult to gather the enough funds to build the traditional machine treatment factory to treat sewage in those towns.This paper sets Dongting Lake region for the example to study how to control and treat wastewater effectively and economically in developing districts. Based on the studying on the superiority of wetlands treatment systems and analyzing the natural and objective conditions, for instance, the worsening water quality, the shortage funds and so on. The paper proposes that we can fully utilize the plenty of wetland resources and apply constructed-natural wetlands to treating sewage in Dongting Lake region, preserving ecological environments and relenting the acute contradiction between the preserving environment and the investment in small towns.The paper analyzes and demonstrates the feasible ofapplying wetland eco-system to treating sewage in Dongting Lake region form three aspects: the superiority of wetland treatment systems, the natural conditions and the necessary of the purifying wastewater, then sets the process of sewage treatment at Heba Town in Datong Lake District for the example to systematically explicate the application promise of the wetland treatment system in Dongting Like region. The analyzing and demonstrating results are as follows:1. Wetlands treating sewage is the result of the cooperation of the physical, chemical and biochemical functions. Compared with the traditional technique, wetland treatment system not only has advantages of low investment, low energy, low operation cost, high efficiency, easy handling and so on, but also has good effects to the nutrition which is hard to be purified in the machine treatment factory.2. Dongting Lake region has plenty and widely distribution of the wetland sources and belongs to the subtropical wet monsoon climate with abundant heat and rich precipitation, which is good for the plant growing. Because of the special horseshoe type landformand three sides gathering to the center in Dongting Lake region, the stream of the wetland eco-system can artesian without manmade energy. Those conditions foresaid offer the superiority natural conditions to applying wetland treatment system in Dongting Lake region.3. According to the monitored data of Dongting Lake in 1999 ~ 2000a, we know: the water quality has already been polluted seriously, the most serious pollutants is phosphorus, nitrogen, suspended matter and so on. The eutrophication has already reached to the middle-high class. In further ten years, because of the effect of the SanXia project and the recovery and so on, the water quality would be even worse and theeutrophication would be more apparent. So, it is necessary to purify the water poured into Dongting Lake.4. The process of sewage treatment using wetlands at Heba Town in Datong Lake District sets a good example for the applying wetland treatment systems to Dongting Lake region. The process offers the sufficient data for other area through studying on the chosen domicile, the designed engineering, the adopted parameter and so on.Therefore, on the precondition of little investment, we would sufficiently utilize the plenty of wetland resources and strongly developing the effici...
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