The comparison of parasite eggs and protozoan cysts of urban raw wastewater and efficiency of various wastewater treatment systems to remove them

One of the most important quality characteristics associated with wastewater reuse in agriculture is the microbial quality. This study aimed to determine the efficiencies of Ghasreshirin (constructed wetland), Islamabadgharb and Gilangharb wastewater treatment plants (stabilization ponds), Sarpolezahab and Paveh (extended aeration activated sludge) and Kermanshah (conventional activated sludge) in the removal of protozoan cysts and parasitic eggs. This study was carried out during six months and samples were collected at weekly intervals from influent and effluent of the wastewater plants. In order to determine the concentration of ova, 288 samples were analyzed by Mc Master Slide according to Bailenger method. No parasite eggs or protozoan cysts were detected in the effluents of the constructed wetland or stabilization ponds systems. The extended aeration activated sludge system of Sarpolezahab removed 99-100% of parasite eggs and >= 99% of protozoan cysts. The respective values for extended aeration activated sludge system of Paveh were 97.5-100% and >= 99%. However, the conventional activated sludge of Kermanshah removed 97-99% and 99-100% of parasite eggs and protozoan cysts, respectively. According to the results, removal efficiency for cysts and parasite eggs in natural systems (constructed wetland and stabilization ponds) is better than mechanical systems (extended aeration activated sludge and conventional activated sludge). The effluent quality of all systems in terms of nematode eggs is consisted to Engelberg index (nematode eggs count: 1 >= counts per liter). (C) 2012 Elsevier B.V. All rights reserved.