Comparison of the efficiency of extended aeration activated sludge system and stabilization ponds in real scale in the removal of protozoan cysts and parasite ova from domestic wastewater using Bailenger method: a case study, Kermanshah, Iran

AbstractOne of the most significant qualitative characteristics that is associated with reusing wastewater in agriculture is microbial quality. The present study is aimed to determine the efficiency of extended aeration activated sludge system and stabilization ponds in real scale in removing protozoan cysts and parasite ova from domestic wastewater in Kermanshah. Within 6 months, influents and effluents of four wastewater treatment plants (WTPs) were collected weekly. A total of 192 samples were collected and examined microscopically (McMaster Counting Slide), applying modified Bailenger method. The results revealed that mean removal efficiencies of protozoan cysts and parasite ova for both stabilization pond systems were 100% and 100%, respectively. The mean efficiencies of removing these elements in the extended aeration activated sludge in Sarpol-e-Zahab wastewater plant was 99–100% and 100%, respectively. Also, in the extended aeration activated sludge in Paveh, these mean removal efficiencies were 97.5–100% and 100%, respectively. The results indicated that the efficiency of the stabilization pond system was more honorable than the extended aeration activated sludge system. Moreover, the efficiency of all three WTPs was desirable. Thereafter, the effluent quality of all three WTPs was consistent with Engelberg standard indicator (number of Nematode eggs: 1 ≥ per liter).