Abstarct: Over the past two decades, excessive sludge production has grown rapidly due to increase of population, and this matter has become a crucial economic and environmental challenge today. The management of excessive sludge costs more than 50% to 65% of the total operating cost of a waste water treatment plant. The research was carried out in two different stages. In the first part of this study, a batch reactor for the simulation of the actual wastewater treatment plant, along with a side-anaerobic reactor as a unit of treatment was designed and operated. In first stage, in order to achieve the optimal hydraulic retention time (HRT) in better state of sludge removal, the trend of spirometry graph was studied and the 10 days was achieved as an optimal HRT. In the second step, the sludge production efficiency were evaluated in the control, and optimized pilot, which were, 0.68 g TS / g COD and 0.51 g TSS / g COD respectively. These results confirm that this process can reduce sludge production by more than 20%. To explain the results of sludge reduction, EPS, SCOD, MLSS, etc., have been analyzed. Thus, research has shown that side-anaerobic reactor can be an effective solution in trend of sludge production due to minimizing sludge yield, which enables the efficiency of carbon and nutrients removal using a very simple technology.