Majid Ghanbari Pak
1 
, Reza Shokoohi
2, Kazem Godini
3, Ghasem Azarian
2* 1 Hamedan Wastewater Treatment Plant Process Expert, Hamadan, Iran
2 Department of Environmental Health Engineering, Faculty of Health and Research Center for Health Sciences, Hamadan University of Medical Sciences, Hamadan, Iran
3 Environmental Health Research Center, Research Institute for Health Development, Kurdistan University of Medical Sciences, Sanandaj, Iran
Abstract
To facilitate the wastewater recycling process while adhering to environmental and industrial regulations, it becomes imperative to meet stringent standards. This necessitates the effective elimination of organic substances, with particular emphasis on nitrogen-based compounds. To this end, activated sludge methods, particularly the step-feed biological nitrogen removal (SFBNR) process, are employed. Although various operational measures are employed in SFBNR systems, including the elimination of complex substrates, modifications in aeration conditions, the utilization of piston hydraulic flow, and the appropriate distribution of substrates, these systems remain susceptible to the excessive growth of filamentous bacteria. The current study aimed to examine the change in the distribution of the hydraulic flow entering this system on a real scale over a period of five years. It was observed that the quality of sludge settling improved and accordingly the overgrowth of filamentous Microthrix parvicella declined, thereby enhancing the quality of the effluent.