Investigation Research of Effectiveness of Blue-green Algae Growth Control in Chinese Lakes as a Model Case

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We obtained the following empirical results for consideration in formulating measures to reduce the load on the aquatic environment in the target lakes of Guizhou Province of China as a case study. It is possible to reduce concentrations of nitrogen and phosphate in treated domestic wastewater to less than 20mg・1^<-1> and less than 1mg・1^<-1>, respectively, in a stable manner by optimizing management and maintenance, which includes eliminating waste sludge from advanced Johkasou systems. It is possible to reduce concentrations of nitrogen and phosphate to less than 10mg・1^<-1> and less than 0.5mg・1^<-1>, respectively, through optimal operation of the unpowered anaerobic filter beds of soil-trench domestic wastewater-treatment facilities (30m^3・d^<-1>, while pursuing energy conservation. It is possible to reduce by 60 percent of the concentration of chlorophyll-a at dam sites by controlling algal growth through the operation of cylindrical intermittent aeration pumps. To reduce existing concentrations of toxic blue-green algae it is possible to keep the population density of Ceriodaphnia dubia, a predator that is present during, filtration, at a high level by increasing the level of aquatic vegetation. With a view to introducing Bio-Eco Engineering, we also conducted a survey of the current situations in the lakes of neighboring countries. We found that the existing amounts of blue-green algae in these lakes have reached 150,000cells・ml^<-1>, and that problems with water utilization are growing obvious because of the increasing amounts of toxic blue-green algae, as in the eutrophic lakes in China. We clarified the fact that eliminating nitrogen and phosphate through the application of Bio-Eco Engineering, which works well to prevent the growth of toxic blue-green algae, is very important to control eutrophication in these aquatic environments. The methods described above are expected to be very useful.