Optimization by uniform design U8(83) approach for enhanced caffeine degradation in synthetic wastewater in bioreactor

Abstract

Coffee wastewater contains large amounts of caffeine which affects microflora and seed development to great extent. Although several physio-chemical methods available for caffeine degradation, they are not preferred for large-scale treatment. In this study, we optimized induced cell concentration, aeration and agitation rate for maximizing caffeine degradation rate in bioreactor using Uniform design. Maximum caffeine degradation rate of 23·59 mg L−1 h−1 was achieved. The reduction in chemical oxygen demand, biological oxygen demand and total organic carbon removal were found to be 72, 78 and 72% respectively. Mathematical model was developed through regression analysis and predicted maximum caffeine degradation rate of 24·2 mg L−1 h−1 under optimal conditions of 0·35 g L−1 biomass, 395 rev min−1 and 1·62 vvm. Experimental validation at optimum condition resulted in 22 mg L−1 h−1 of caffeine degradation rate. This is the first-ever bioreactor study showing highest caffeine degradation rate in synthetic coffee wastewater with limited experimental runs.