Abstract:
Mass use of quaternary ammonium compounds (QACs) caused these chemicals to become an environmental concern. Little or no elimination of QACs in wastewater treatment plants necessitates a removal policy for these chemicals within treatment system before discharge. In this study, an advanced treatment system after biological treatment is proposed for efficient removal of benzalkonium chlorides (BACs), the most common type of QACs in consumer products. Cultures of Pseudomonas sp. BIOMIG1BDMA which can convert BACs into dimethylbenzylamine (BDMA) were immobilized into Ca-alginate beads. Beads were optimized with respect to CaCl2 concentration and diameter for the best BAC biotransformation efficiency at a cell density of 107 CFU/mL. Optimal beads were 3 mm beads produced by using 0.15 M CaCl2. Number of cells in these beads was found to be 4.6±1.4x106 CFU/bead. BAC degradation kinetics of these beads were analyzed for C12BDMA and C14BDMA. The cell specific utilization rate constant was estimated to be 0.46 μM-BACs/hr. Continuous flow packed bed reactors were prepared using alginate beads as packing material and operated at 4.7, 2.3, and 1.2 hrs empty bed contact times corresponding to 1.3 hrs, 0.8 hrs, and 0.3 hrs mean residence times. 85±5% removal efficiency was obtained with the setup of 0.3 hrs mean residence time at 20 μM BACs. The same flow rate gave 102±11% removal efficiency for 2 μM BAC concentration, and 95±5% removal efficiency for actual wastewater.
