Microbial community structure of activated sludge in treatment plants with different seasons

Abstract

Biological treatment is based on activated sludge that shows filamentous bulking with change in temperature, which has effect on wastewater treatment process. The aim of study focuses on variation microbial (Bacteria-Fungi) in the activated sludge in two seasons and affects them on treatment of wastewater. The wastewater samples were collected in October-November of 2018 and March–April in 2019 during (autumn - spring) from (old project - second expansion - third expansion, Al-Rustmiya). The results showed 418 isolates representing 9 fungal species screened from wastewater samples during two consecutive monthly surveys seasons (for October-November, 2018 and (March-April, 2019). Results showed that fungal number varied through the survey months. The highest number was 112 isolates. Also, presence of more fungus was there in the old Al-Rustmiya plant, second expansion Al-Rustmiya plant, especially in April, despite the lack of dominance, where Aspergillus flavus species predominated by 40%. For all projects the highest isolation count found was in April (143 isolates). All projects (old Al-Rustmiya plant and second, third expansion Al-Rustmiya plant) show increase in sludge volume index due to the high fungi, especially the filaments fungus. In addition, four types of bacteria were isolated; Escherichia coli, Pseudomonas aeruginosa, shigella sp. and Klebsiella sp. Also observed during statistical analyses program was correlation between phosphate and Nitrate, Aspergillus tamarri, as well as the relationship between phosphate and Biochemical Oxygen Demand Fusarium solani Aspergillus Tamari, Nitrate relationship with Total Dissolve Solid. Although, the sludge volume index is high but it is close to specification and does not indicate about sludge bulking.