Determination of the potential of wastewater treatment plant effluent of Yazd for use in agricultural sector based on global criteria

In order to evaluate and classify the quality of wastewater treatment plant effluent of Yazd, and assessing its potential for agricultural sector usage, wastewater samples were weekly collected, and microbial tests, the traits of fecal coli forms (FC), nematode egg (NE) number per each sample, the concentrations of PO4, NO2, NO3, NH3, SO4, Na, Ca, Mg, K, HCO3, CO3, B, Fe, Zn, Cu and Mn ions, and the amounts of pH, EC, SAR, were measured using standard methods. The results showed that wastewater is classified as class B, using WHO guidelines. So, it is suitable for irrigation of cereals, industrial and fodder crops, pastures and ornamental plants. The most limiting factor for applying this wastewater in agriculture is high concentration of HCO3 which will increases SAR through sequestration of calcium and magnesium ions and consequently decreasing the infiltration rate of soil in long period of time. According to the estimates, the Gypsum Requirement (GR) for alleviating harmful effects of high SARadj level in wastewater is equal to 8.62 ton ha-1. High concentration of macronutrients in the wastewater made it feasible for cultivating industrial and fodder crops such as cotton, barley and halophytes. Boron toxicity in the wastewater is not a limiting factor. The concentration of Na and Cl in wastewater was less than the toxicity threshold of these ions for cotton, sunflower, corn, sorghum, safflower, sesame, etc. The concentration of Fe, Cu, Zn and Mn in the wastewater is under toxicity levels that are recommended by FAO, so these elements do not cause any ionic toxicity for plants.