Impact of treated vs. un-treated municipal wastewater irrigations in Eggplant (Solanum melongena L.) on soil-plant metal translocation, crop yield and consumer health hazard

Abstract

Abstract The present study assessed the impacts of municipal wastewater treated through a constructed wetland on the crop yield of eggplant and human health hazards, due to the consumption of the metal and pathogen enriched eggplant fruit. The impacts were compared with groundwater the untreated municipal wastewater irrigations, applied individually and conjunctively. The soil irrigated with untreated wastewater had 1.94, 2.41, 4.68 and 3.29 times higher soil organic carbon, nitrogen, phosphorus, potassium and 2.18–4.46 times higher soil micronutrient contents, respectively compared to soil irrigated with treated wastewater. The plant nutrient uptake and crop yields from the untreated wastewater irrigated plots were 22–23 and 10–18% higher than those from the groundwater; treated wastewater and conjunctively irrigated plots. Compared to the untreated wastewater irrigated plots, the plots receiving treated wastewaters (having 14 to 86% lower metal concentrations) or conjunctive water use had 47 to 50% reduced trace metal built-ups and 31–50% and 14–31% reduced consumer health hazards, respectively. Further, the produce generated from treated wastewater had 36% lower total heterotrophic bacteria and 70% lower total coli-form. The produce obtained from the conjunctively irrigated plots also had 24% lower total heterotrophic bacteria and 46% lower total coli-forms but these values were still 20 and 76% higher than those from the treated wastewater irrigated plots thereby confirming safer reuse potential of the treated wastewaters compared to either the conjunctive use or the direct disposal of untreated wastewaters in the vegetable production systems.