Abstract:
The research work embodied in this report investigated the effects of sewage sludge, and sewage irrigation on heavy metals contents in soils and plants, soil salinity, soil fertility, and crops yield. This work was carried out during the years 1998-99 and 1999-2000.
Sewage sludge is the product of sewage treatment plants and is the solid waste (digested aerobically or anaerobically) removed from sewage during treatment. Sewage sludge can be used as organic amendment for improving soil fertility and crops yield but as it may contain excess of heavy metals and salts, its long-term land application for crop production may deteriorate soil quality and cause health hazards. In Islamabad, sewage sludge is being produced at CDA Sewage Treatment Plant and sold to the farmers as an organic amendment without considering its pollution effects on soil and crop. It was therefore, important to evaluate suitability of this sewage sludge for crop production and advise the farmers accordingly.
Sewage (city and industrial wastewater) is being generated daily in thousands of tons in the main towns. The sewage is mainly drained into streams, nullahs, lakes and rivers. Part of it is employed by the farmers to irrigate their fields situated in and around the towns. Since it is rich in organic matter and plant nutrients, the farmers are able to get good crop production from this wastewater which is available to them free of cost most of the time. However, the sewage may contain excess of heavy metals and salts and its use may result in soil pollution and health hazards. It was therefore, considered important to study the impact of sewage irrigation on heavy metals contents in soil and plants, soil salinity.
The research findings about sewage sludge and sewage irrigation are presented in Part-I and Part-II of the report, respectively.
