PILOT-SCALE INTEGRATED FIXED FILM ACTIVATED SLUDGE SYSTEMS FOR WASTEWATER BIOLOGICAL NUTRIENT REMOVAL

Abstract

ABSTRACT PILOT-SCALE INTEGRATED FIXED FILM ACTIVATED SLUDGE SYSTEMS FOR WASTEWATER BIOLOGICAL NUTRIENT REMOVAL by Kingsley Nze The University of Alberta, Winter 2018 Under the supervision of Dr. Yang Liu In this study, the performance of two identical pilot-scale biological nutrient removal - activated sludge (BNR-AS) reactors were assessed as their influent flow rate was increased from 30L/min through 45L/min and up to 60L/min. The bacteria community structure for nitrifiers and denitrifiers as well as the protein to polysaccharide ratio (PN/PS) of the extracellular polymeric substances (EPS) in both reactors were monitored during each flow rate. The experimental results showed that both reactors maintained excellent chemical oxygen demand (COD) removal, however, the removal of ammonia and phosphorous deteriorated at some point during 40L/min influent flow rate and beyond. Furthermore, bacteria community analysis showed that Nitrobacter was the more dominant of the two nitrite-oxidizing bacteria (NOB) communities that were investigated. The EPS analysis demonstrated that the PN/PS of sludge EPS significantly decreased as the solids retention time (SRT) decreased from 9.3 days to 2.2 days. Furthermore, PN/PS content had the tendency to temporarily increase in response to an increase in flow rate before decreasing back to a steady value. This study also compared the performance of a BNR-AS reactor side-by-side with a biological nutrient removal â integrated fixed-film activated sludge (BNR-IFAS) reactor. The experimental results showed that the proliferation of red worms identified as Aeolosoma hemprichi in the BNR-IFAS reactor led to the significant deterioration in the BNR-IFAS reactor performance especially in ammonia removal, although COD and phosphorous removal seemed to be unaffected by the red worms. Of the different strategies applied to eliminate the red worms, the most effective was shutting off the dissolved oxygen in the aerobic zone for 48 hours in addition to cutting off influent feed supply, stopping nitrified liquor recycling and maintaining low mixed liquor suspended solids (MLSS) concentration.