The study was conducted with an aim to optimize the parameters involved in removing organics from brewery effluents using a newly developed horizontal subsurface flow vermifilter. It was also aimed at understanding the impact of hydraulic retention time (HRT) on the vermifiltration of brewery wastewater. With the help of Box-Behnken design (BBD) and response surface methodology, optimization of the COD removal from the vermifiltration was carried out. The parameters chosen for the optimization were hydraulic loading rate (HLR), organics strength and earthworm densities (EWDs). The model obtained from the response surface methodology (RSM) analysis was a quadratic polynomial model with R2 value of 0.99. The optimal conditions for achieving maximum chemical oxygen demand (COD) removal were at influent COD concentration of 3542.22 mg/L, EWD of 9661.33 earthworms/m3 and HLR of 1.84 m3/m2·d. At the optimum conditions, COD removal of 94.99% was obtained against the predicted value of 95.85%. Verification of the model on real brewery wastewater also showed minimal error against the predicted COD removal. The COD, total nitrogen (TN) and total phosphorous (TP) removal at the HRT of 10.66 h were found to be 73.88%, 18.13% and 39.04%, respectively. Whereas, The COD, TN and TP removals at the HRT of 26.66 h were 96.24, 21.57 and 43.3%, respectively.
Keywords: Brewery wastewater; Earthworm density; Hydraulic loading rate; Hydraulic retention time; Optimization; Response surface methodology.
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