The consequences of disposing wastewater in an endorheic wetland in southwest Iran

Wetlands are important ecosystems both at regional and global scales. They are home to a diverse group of flora and fauna, and provide water for drinking, irrigation, and recreational purposes. Miangaran endorheic wetland in SW Iran serves as the discharge point of the municipal wastewater of a nearby city; it receives agricultural return flows as well. To identify the consequences of the wastewater input, 29 water samples from the wetland's body and inlet streams were analyzed for physico-chemical parameters. The average EC of the wetland was 405 μS/cm; calcium, magnesium, and bicarbonate were the dominant ions. The average pH was high, about 8.6, due to carbonate dissolution in the drainage area which was exacerbated by photosynthesis process inside the wetland. The concentration of phosphate was over the eutrophication limit of 0.1 mg/L. Nitrate contents varied from 5.7 to 12.3 mg/L. Trophic state index based on total nitrogen was about 63, falling within the eutrophic group. Heavy metal concentrations were generally higher than WHO drinking limits. Highest values of EC, nutrients, and metals were observed in the south and northwest, clearly signifying the role of wastewater input as the main source of contamination, which has resulted in the eutrophication of the wetland.