Comparison of Treatment Capacities of Swim-bed and Activated Sludge Processes for Domestic Wastewater

Some operational problems remain unsolved for the conventional activated sludge (CAS) process, such as the large space requirement, high operational cost and large excessive sludge production. Swim-bed technology using a novel acrylic-fi ber material biofringe (BF) material for biomass attachment is considered as a solution to some of these problems. In lab-scale tests, the CAS and BF processes were operated in parallel while contaminant removal effi ciencies and sludge productions were compared. The study was conducted in two runs with BOD volumetric loading rates of . kg-BOD/m /d for the Run I and . kg-BOD/m /d for the Run II, corresponding to hydraulic retention times of . h and . h, respectively. Overall, superior contaminant removal effi ciencies were demonstrated for the BF process. Average COD removal effi ciencies for the BF and CAS processes in Run I were % and %, respectively, and in Run II, % and %, respectively. High nitrifi cation effi ciencies were obtained for both processes throughout the study; however, during Run II, the BF process had a signifi cantly improved nitrogen removal effi ciency of % versus % for the CAS process. After increasing the volumetric loading rates in Run II, sludge washout occurred in the CAS process, while high biomass levels were maintained in the BF process, demonstrating the retention capacity of the BF carrier. Sludge yields were calculated to be . kg-MLSS/kg-CODremoved for the CAS process versus . kg-MLSS/kg-CODremoved for the BF process in Run I and . kgMLSS/kg-CODremoved versus . kg-MLSS/kg-CODremoved, in Run II, respectively. A large amount of protozoa and metazoa were found in the BF process, which could have contributed to the observed reduction of excess sludge.