Leachate wastewater treatn1ent via application of natural Zeolite

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 water contarninant concentration is then crucial before entering water to the natural resources or its transfusion d irectly to the soil as irrigation water. Four studies were carried out in a pilot plant to evaluate the effect of natural Zeolite to decrease chemical and biological index of compost factory leachate. Land treatment was considered as the main strategy; however, some pounding and column experiment was implemented as well. Wastewater chemical and biological indexes were analyzed. These indexes consisted ofNa, K, Mg, Ca, Co3, HCo3, Ni, Cd, Pb, Cr, Chemical Oxygen Demand (COD), Fecal Coliform (FC) and Total Colifor1ll (TC) . In addition, soil was analyzed for EC, pH, Cation and Anion. Results: In the first study, three types of Zeolite,derivated from Semnan, Mashhad and Mianeh rnines were tested with four sizes (70, 140, 270 and 840 micrometer) at 25°C in smmner 2007. It was concluded that high value of the cation concentration in the leachate, causes niether adsorption of remaining cation nor heavy metals (HM). There was no statistically significant difference between the Zeolite sizes and the heavy metal adsorption. The results also showed that the adsorption ratio (AR) was 52, 23 and 40 percent for Na, Ca and Mg, respectively. In the second study, a loamy sand soil was enriched by adding five and ten percent of the Zeolite. The result uncovered that adding ten percent of the Zeolite to the soil brings about more elements' absorption in comparison to application of the five percent Zeolite. Irrigation with the leachate reduced soil specific yield, significantly. In the third study, a complete randomized design experiment was used with 6 treatments (2 kind of soil, loamy sand and clay loam, and 3 levels of zeolite, 0, 5 and 10%) and 3 replications perfonned in the lysimeter size. The results revealed that in·igation with the leachate reduces soil bulk density, infiltration rate and saturated hydraulic conductivity. Heavy metals could not be absorbed by loamy sand soil; whereas, clay loam soil had a high ability to absorb heavy metals and reduce the salinity. In loamy sand and clay loam soil, ten percent Zeolite had a significant effect on heavy metals' absorption. The result of subsequent study (the same setup as the third study), exhibited the fact that the COD was significantly decreased by application of five percent Zeolite;while,this reduction was occured via applying ten percent of Zeolite in TC. Conclusions: In short, this research indicated that the wastewater can be treated in a simple, economically process of land treatment tlu·ough application of a clay loam soil texture with a cation pre-treatment

Keywords:

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