城市污水“处理”的误区——化点为面

MISCONDUCT OF URBAN WASTEWATER DISPOSAL—SPREAD COLLECTED SEWAGE TO THE LAND

本文根据人类与水环境关系发展的三个阶段,分析了东、西欧污水土地利用和污水灌溉事业的兴衰过程和天津市污水灌溉对“引滦”水质带来的影响,以及目前美国、加拿大等国某些地区仍在进行污水土地利用的特点后认为,我国大中城市周围都已进入生态环境阶段,可资利用的土地和水体资源已十分有限,这一方法已不能作为污水处理的代用品和污水资源化的途径。如仍将已集中起来而未经处理的城市污水再分散到农田和水体去,则只能起一种污染搬家和与现代排水工程的功能相反的作用。作者赞同将城市污水进行二级处理后,再把出水(BOD_5<20mg/L)送到农田、水体进行补充净化,使其达到更高的水质。但强调指出,这只是一种污水深加工的手段,而不能作为一种“污水处理”的方法。

A very critical relationship between mankind and water sphere called eco- environmental stage has been evolved in the densely populated eastern part of China.The water resource falls short of the demand and the natural assimilation capacity is lower than the pollution load created by human activities.Looking back on the rise and decline of sewage irrigation(SI) in Europe and the consequences of SI in Tianjin metropolis,especially its influence on the quality of water from Luanhe River—the unique water resource for Tianjin—the authors of this paper were convinced that any disperse disposal of urban wastewater,spreading collected sewage to the land such as SI,land treatment and so far as oxidation pond,which are opposite to the essential purpose of urban sewer system,will be harmful to the ecological balance and result in unfavorable effects to the water environment.However,on the eco-environmental stage,the disperse disposal may still be adopted as a polishing measure to the treated effluent but not a substitute for secondary wastewater treatment.