Evaluation of Effluent Quality Used for Irrigation of Vegetable Production in Different Districts of Potowar, Pakistan

摘要

A study was conducted in different districts of Potowar region to evaluate the quality of sewage for irrigation purposes and heavy metal contents in sewage water. Sewage samples were collected from 25 sewage irrigated farms around Rawalpindi, Attock and Abotabad districts. Electrical conductivity of the samples ranged from 0.55-2.36 dS m-1. Sixty percent of the samples did not pose salinity hazard while forty percent were marginally fit for irrigation. Sodium adsorption ratio ranged from 0.24 to 4.36 showing that all the samples were low in Na contents. RSC varied from 0.0-8.1 mmol L-1 in the sewage samples under study; 59% of the samples had -1 of RSC showing that sewage represented by these samples had no risk of NaHCO₃ hazard when applied to soils. Chloride contents in the samples were in the range of 0.5 to 4.7 mmol L-1 and were within safe limits. Zn and Pb contents in the sewage of various locations were found within safe limits ( -1, respectively) while Cu, Cd, Ni and Cr concentrations were found to exceed the maximum permissible limits. The effluent of areas under investigation are mixture of both domestic and industrial wastewater, high levels of HCO₃- from washing soaps and detergents and excess of heavy metals from different industrial sources were present in the effluent. Therefore, sewage irrigation may cause deterioration of soil quality by causing salinity and introducing excessive contents of HCO₃- in soils and poses health hazards by increasing heavy metal contents in vegetables and crops.