Abstract
One of the problems of wastewater disposal, in addition to organic and microbial substances, is the release of nitrogen and phosphorus 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 the phenomenon of Eutrophication. This quantitative, sectional, and analytical research explores the use of thermo-biological methods in the return sludge line to reduce the pollutions and address the 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 40oC, significantly improved efficiency in TN removal, TP removal, reduction in sludge production coefficient, and excess sludge disposal. The average values obtained for growth yield(Y) in the 60-day study period after the biological reactor stabilized showed a decrease from 0.75 to 0.54 in 40oC return sludge temperature, 0.38 in 50oC, and 0.30 in 60oC(gMLSS/gCOD). The examination of the difference in average cellular mass production coefficient (Y) in the existing system with 40oC return sludge indicated a 19.7% reduction compared to the system at present, 49.33% in 50oC, and 60% in 60oC conditions, reflecting a decrease in biomass production coefficient with increasing temperature. While the study revealed a reduction in biomass production coefficient with higher return sludge temperature, it also highlighted the negative impact on effluent quality and sludge settling capability.