Heavy metal elimination from industrial wastewater using natural substrate on pitcher irrigation

Combination of pitcher irrigation with drip irrigationsystem could be resulted in prolonging the secondarytreatment period, as it could be an efficient systemin which municipal and industrial wastewater can be treatedand heavy metals can be reduced. For this purpose, anexperiment was conducted with three treatments [claypitcher included natural zeolite Clinoptilolite (NZ), perlite(P) and vermiculite (V)] which filled half of the volume ofa clay pitcher with five replications for each treatments.Beside each tree, one pitcher was placed at 50 cm depth.The soil of each hole was initially sampled, sealed, andtransported to the laboratory. The pitchers were irrigatedwith treated industrial wastewater (from steel factory) 60times (1500 cc per each irrigation event) over a period ofsix months. At the end of experiment period, the pitcherswere removed and samples were taken from the substrateinside each pitcher and from the soil near the walls andbottoms of the holes. The sealed samples were transportedto the laboratory for analyzing heavy metals (Fe, Cd, Cr,Cu, Pb, Mn, and Zn) using an atomic absorptionspectrophotometer. The results showed that the used substratesin this experiment have high ability to absorb someheavy metals, especially Pb and Zn which concentrationwere increased in final value 75 and 80 times comparedwith initial values, respectively. However, an increase ofthese two elements in the soil (Zn = 26 and Pb = 71 ppm)nearby the pitcher indicate that the used substrates havelimitations in absorption capacity for the heavy metals inhigh concentration of them in the wastewater. As this isrelated to their surface area, application of a nano form ofthe substrates such as nano zeolite might remarkablyincrease their cation exchange capacity and surface area.