Naeim Banisaeid
1 
, Afshin Takdastan
2 , Mahboobeh Cheraghi
1* , Ali Afrous
3 , Reza Jalilzadeh Yengejeh
1 1 Department of Environmental Engineering, Ahvaz Branch, Islamic Azad University, Ahvaz, Iran,
2 Environmental Technology Research Center, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran
3 Department of Environmental Engineering, North Tehran Branch, Islamic Azad University, Tehran, Iran
Abstract
One of the problems of wastewater disposal is the release of nitrogen and phosphorus in addition to organic and microbial substances into receiving waters, and the removal of nutrients from wastewater has become one of the main global problems because the compounds of nitrogen and phosphorus in natural aquatic environments cause eutrophication. This quantitative, sectional, and analytical research explored the use of thermo-biological methods in the return sludge line to reduce the pollution and address excessive sludge production. The research also investigated the impacts of temperature changes in the anoxic tank and the return sludge line. Results showed that the existing conventional bioreactor, with a temperature change in the return sludge to 40 °C, significantly improved total nitrogen (TN) and total phosphorus (TP) removal efficiency. Although the change in the temperature of the returned sludge increased the TN and TP removal efficiency, the removal rate was not significant, and this is despite the fact that this efficiency also decreased with increasing temperature. The study revealed a reduction in biomass production coefficient at higher return sludge temperatures, it also highlighted the negative impact on effluent quality and sludge settling capability.