Study On Effective Operation Mode Of Wastewater Irrigation In Agricultural Ecosystem

The effective operation mode of wastewater irrigation has been studied, involving investigation of fundamental information, field experimenting at centralized wastewater irrigation area, simulating bonsai test and evaluating of economic loss. The investigation is carried out on thoroughly the pollution source , wastewater capacity and area investigated in Hebei province. The types and level of wastewater affecting on soil ,water and crops in different of irrigation modes and standard conditions, analyzing qualitatively the effect by using economic method and supporting economically the reasonable irrigation scheme are developed. And a effective irrigation mode in Hebei province is advanced based on investigations above mentioned.The impacts of sewage on 4 typical irrigation area — Luan City, Zhao county , Xinhe in Shijiazhuang and Qingyuan county in Baoding city are investigated and compared with clean water irrigation area nearby.Comparing with clean water irrigation, heavy metal is accumulated obviously in soil irrigated chronically by sewage at typical wastewater irrigation area, but besides cadmium, the heavy metal contents are lower than those of the Environmental quality standard for soils. According to quality and capacity analysis of irrigation wastewater presently, at typical sewage irrigation area the contents of arsenic and cadmium is increased in soil. The ground water in shallow land is polluted ,The contents of nine kinds pollutions-COD, NH₃-N et al. are higher than clean water irrigation area's. Heavy metals such as cadmium, arsenic ,are accumulated in water, but their contents aren't higher than those of Water Quality Standard for Drinking Water. Population health is damaged obviously at wastewater irrigation area. By calculating morbidity gap at clean and waster water irrigation area, there are 153389 patients who have cancer, liver tumefaction, stomach ailment as well as digestive system sick caused by sewage irrigation, which is 6.7% of total population at sewage irrigation area. The contents of heavy metals in agricultural products are higher than those of the standard of stipulating in the country at wastewater irrigation, the total output polluted takes 0.17-0.9% of total output. The crop output can be improved obviously by irrigating sewage reasonably, and the rate of increase production is more 10%. Environmental cost of wastewater irrigation is about 85.7 million every year in Hebei province, which takes 0.1% total agricultural output (2000). The economic loss from health damage is the highest. The marginal environmental cost of crop(wheat and com) is 0.076 RMB/kg.About 36,000 datum are accomplished in two yeas period investigation. The effects of each essential factor and economical property in agricultural ecosystem are determined at provincial level. Technical advices to irrigation mode are posed. The work has made important progress in effective operation of agricultural ecosystem, for consumer health and sustainable development of society.