Discussion on Sewage Irrigation Development Process in the Suburbs of Beijing City

Since the local farmers started to irrigate farmland with the sewage water of the Shijingshan Iron and Steel Industry Factory in the 1940's, the sewage irrigation development in Beijing City can be divided in 4 periods: beginning, rapid increasing, stabilizing, and declining. Meanwhile, the quantity of sewage water is increasing every year. From 1954 to 2000, the quantity of sewage water increased from 0.24×10 8 m 3 to 13.55×10 8 m 3, and the average increase rate per year was 9.16%. The domestic sewage water toke more part of the total sewage water with the population increasing. For example, in 2000 the domestic sewage water accounted for 60% of total sewage water, while the industry sewage water accounted for 40%. The location of sewage water irrigation shifted from the west to the northwest suburb, then to the north suburb, south suburb, and southeast suburb of the city. The initial area was only 666.67 hm 2 in the west suburb, then it increased to its maximum 80 000 hm 2, and then it decreased to 26 700 hm 2, mostly located in the southeast suburb.