economic criterion
5.In the research of environment economics, economists try to find the cause of environmental pollution from the economic point of vie w. They attempt to find a reasonable criterion of welfare to combine the use of resources, economic development and social welfare, and analyse the problem of e nvironment economics on the basis of efficiency and equality.
6.The processf electrophoretic-deposition which occupies impoartant place in painting-industry produces plenty of waste-water, whose BOD and COD exceed the emission criterion, The treatment and beneficient-recycling of the waste-waste-water have great economic-benefits, environmental-benefits and social-benefits.

