WATER ENGINEERING

Water Engineering

Water Engineering

Introduction to the Problem

Today, the attention of the whole world is mainly focused on the problems which result in undesirable changes in the physical, chemical and biological characteristics of air, water and soil, ultimately affecting human life and the lives of animals and plants (Misra and Dinesh, 1991). An important segment of environmental pollution that is directly affecting the health via crops and soil is due to the indiscriminate use of untreated sewage water. In Pakistan, the pre-disposable treatment of sewage effluent is not practicable. Sewage is the spent water of a community, its liquid portion becoming a carrier for the transport of waste in sewers. This sewage comprises a complex mixture of organic and inorganic matter. It also contains macro- and micro-organisms and is an excellent vehicle for their dissemination. Thus it serves as an efficient carrier of human pathogen along with heavy metals that are hazardous to the environment and human health. There are two basic disposal systems of sewage in Pakistan. One is its direct application on vegetables and crops, while the other is disposed of in nearby rivers or lakes.

Discussion

Although the sewage effluent is considered to be a source of organic matter and plant nutrients and serves as good fertilizer, it also contains considerable amount of potentially harmful substances including soluble salts and heavy metals like Fe2+, Cu2+, Zn2+, Mn2+, Ni2+, Pb2+. Additions of these heavy metals are undesirable (O'Riordan et al., 1983). The use of sewage effluent as fertilizer has gained much importance in Pakistan. Effluent users are mainly interested in its visual benefits, like increased agriculture production, low cost water source, effective way of effluent disposal, source of nutrients, organic matter and so many others. But they are not well aware of its harmful effects like heavy metal contamination of soils, crops and quality problems related to health, etc. Studies have shown that long term use of this sewage effluent for irrigation contaminates the soil and crops to such an extent that it becomes toxic to plants and causes deterioration of soil (Quinn and Syers, 1978; Hemkes, et al., 1980).

The heavy metals accumulate in the various food parts of the crop which leads to various clinical problems in animals and human beings all over the world. Some general toxic effects of heavy metals are hepatic damaging, renal system damaging, mental retardation, CNS breakdown, diarrhoea, hookworm infection and degeneration of basal ganglia of brain and liver (Misra and Dinesh, 1991). Heavy metals in the nutrient cycle have seriously threatened health and environmental integrity, so this problem of contamination should be taken up immediately on war footings. Different studies have been carried out in Pakistan to research the existing situation. The present study is also one of the attempts to explore the alarming scenario with data collected by different researchers.

Measurement of Losses

In developing countries, most water supplies are unmetered. In many instances, water standpipes or blocks of houses have never been fitted with meters, or they have ...