Sayyed Hassan Tabatabaei - Department of Water Engineering, Faculty of Agriculture, Shahrekord University, Shahrekord, Iran
Payam Najafi - Department of Water Engineering, Faculty of Agriculture, Shahrekord University, Shahrekord, Iran
Sayyed Mohammad Javad Mirzaei - Department of Water Engineering, Faculty of Agriculture, Shahrekord University, Shahrekord, Iran
Zohreh Nazem - Department of Water Engineering, Faculty of Agriculture, Shahrekord University, Shahrekord, Iran

Background: The entrance of untreated wastewater or disposal leachate to water resources such as surface water,groundwater or irrigation water increases the risk of contaminant accumulation. Removal or deduction of watercontaminant concentration is then crucial before entering water to the natural resources or its transfusion directlyto the soil as irrigation water. Four studies were carried out in a pilot plant to evaluate the effect of natural zeoliteto decrease chemical and biological index of compost factory leachate. Land treatment was considered as the mainstrategy; however, some pounding and column experiment was implemented as well. Wastewater chemical andbiological indexes were analyzed. These indexes consisted of Na, K, Mg, Ca, Co3, HCO3, Ni, Cd, Pb, Cr, chemicaloxygen demand (COD), fecal coliform and total coliform (TC). In addition, soil was analyzed for EC, pH, cation andanion.Results: In the first study, three types of zeolite derived from Semnan, Mashhad and Miyaneh mines were testedwith four sizes (70, 140, 270 and 840 μm) at 25°C in summer 2007. It was concluded that high value of the cationconcentration in the leachate causes neither adsorption of remaining cation nor heavy metals. There was nostatistically significant difference between the zeolite sizes and the heavy metal adsorption. The results also showedthat the adsorption ratios were 52%, 23% and 40% for Na, Ca and Mg, respectively. In the second study, a loamysand soil was enriched by adding 5% and 10% of the zeolite. The result uncovered that adding 10% of the zeoliteto the soil brings about more elements' absorption in comparison to application of the 5% zeolite. Irrigation withthe leachate reduced soil specific yield significantly. In the third study, a complete randomized design experimentwas used with six treatments (two kinds of soil, loamy sand and clay loam, and three levels of zeolite, 0%, 5% and10%) and three replications performed in the lysimeter size. The results revealed that irrigation with the leachatereduces soil bulk density, infiltration rate and saturated hydraulic conductivity. Heavy metals could not be absorbedby loamy sand soil, whereas clay loam soil had a high ability to absorb heavy metals and reduce the salinity. Inloamy sand and clay loam soil, 10% zeolite had a significant effect on heavy metals' absorption. The result ofsubsequent study (the same setup as the third study) exhibited the fact that the COD was significantly decreasedby application of 5% zeolite, whilethis reduction occurred via applying 10% of zeolite in TC.Conclusions: In short, this research indicated that the wastewater can be treated in a simple, economically processof land treatment through application of a clay loam soil texture with a cation pre-treatment.

Zeolite, Heavy metal, Soil, Leachate, Wastewater, Compost