El-Mardi (1995) studied the effect of treated sewage water on the vegetative and reproductive growth of date palms. Leaves and fruit samples were collected from location irrigated with treated sewage water (TSW), desalinized and well water. Samples were analyzed for their Ca, Mg, Fe, Pb, Cu Zn, Na and K. Treated sewage water from university campus utilities significantly increased the Na, K and Cu and reduced Ca in leaves and Zn in fruits of date palms. But no significant effect was observed on the k, Ca, Mg and Na contents in fruits of the same palms. Leaves of date palms irrigated with desalinized and well water contained higher Ca and Zn. But lower K, Mg, Na, Cu and Pb content of leaves compared to well water. None of the examined metal was found to reach toxic level to man or plant.
Shalaby et al (1996) carried out a greenhouse experiment to study different types of wastes (sewage effluent, oil and soap company and super-phosphate factory) as environmental pollutants and their effect on the mineralization composition of some medicinal plants. The results showed that the trace elements Fe, Mn, Zn, Cu, Pb, Co, Ni and Cd in all the six medicinal plants were slightly and considerably enhanced according to either the source or the concentration of the applied wastes. The higher increases were observed in iron concentration of anise plant, while the Cu concentration showed the least increase.
Venkatesan et al. (1996) conducted an experiment to study the effect of Mn on fodder sorghum. Fodder sorghum was grown with five levels of Mn (0, 2, 4, 8 and 16 ppm) in black soil irrigated with sewage and well water. It has been found that the Mn application significantly influenced the accumulation of most metals in post harvest soil in both available and total forms and concluded that Mn application will restrict the accumulation of heavy metals in soil.
Aitkrn et al. (1997) conducted an experiment to study the effects of liquid sewage sludge application on heavy metal behavior, agricultural productivity and long term soil fertility. Metal sludge applications increased soil concentrations of Cu, Zn, Pb, Ni and Cr to a depth of 100-150 mm. Plant Cu and Zn concentrations were increased but those of Cd, Ni, Cr and Pb were unaffected by sludge application.
Achari et al. (1999) analyzed the paper mill effluent applied at a differing amount with irrigation water to rice crop. Soils irrigated with paper mill effluent had a higher pH and EC. Effluent irrigation, in general, increased the available N and K and decreased available p. DTPA-extractable Fe, Mn, Zn and Cu were also increased due to effluent irrigation. Effluent irrigation did not affect the grain yield. The results suggest the possibility of using paper mill effluent for irrigating rice crop without a major adverse effect on the growth and yield.
Ansari et al. (1999) collected different vegetables grown separately in agricultural soil amended with sludge samples from Mirpurkhas and Hyderabad city, Pakistan in identical conditions. The analysis of soil and sludge samples and vegetables for different micronutrients and toxic elements was accomplished using reliable analytical methods. It was observed that the levels of Cu, Cr, Cd, Pb, Ni and Zn were higher in sludge samples of industrial area than the agricultural soil, Mirpurkhas and the domestic areas of Hyderabad. The level of the elements was high in vegetables grown in soil amended with industrial sludge.
Shah (1999) found that collection drains of Hayatabad Industrial Estate Peshawar (HAIE) were carrying higher BOD and TSS concentrations then the NEQS limits while TDS and pH were found within the standard limits.
Marseille et al.(2000) conducted a green house experiment in France, to measure the heavy metal (Zn, Pb, Cd, Cu) mobilization during the growth of different crop species and their absorption by vegetation. The results indicate that high concentration of heavy metals are absorbed by the plants. Moreover, the establishment of a crop cover ( maize, rape and ryegrass) on dredged sediments is able to quantitatively modify the physicochemical parameters of the sediments, and to increase the mobility of the heavy metals inside.
Bhatti and Perveen (2005) reported that due to the use of sewage water and industrial effluents for agriculture in NWFP, there is a great threat to human animal health. Three channels were surveyed and it was found that 10 out of 18 samples had lead content above safe limits, while 2 in cadmium and 8 in chromium. While soils irrigated with these channels, all the 18 samples were high in Cu and Pb, and 6 in Mn. As regards plants growing on these soils, 5 samples of garlic, 4 of wheat and 3 of berseem were high in Pb, Cd content was high in 5 garlic samples, 5 wheat and 3 berseem. Effluents from two industries were high in Cu, 3 in Cd, and 6 in Pb. A survey of 20 industries in Industrial Estate Hattar showed that all the effluents samples collected from these Industries were above the safe limits in Ni, Pb, Cd and Cr. From these studies, it seems that use of sewage water and Industrial effluents for longer period can create heavy metals hazard in agriculture in NWFP.