OPTIMIZATION OF SUBMERGED MEMBRANE BIOREACTOR (MBR) USING RESPONSE SURFACE METHODOLOGY (RSM)

Abstract

Water is a valuable reserve for the endurance of mankind but we are losing it every day. We can conserve or recharge our ground water by using treated wastewater as an alternative water resource or recharging the ground water respectively. The conventional methods to treat the wastewater are not meeting the recent discharge standards. Eliminating the process of sedimentation, the membrane bioreactor (MBR) is the well-organized way of treating wastewater by the combination of biological process and membrane technology. However, there are some limitations which restrict its applicability i.e. membrane fouling and energy consumption etc. current study focuses on investigating the fouling behavior which is mainly due to increasing flux demand and lack of backwashing and proper relaxation modes in an MBR. Therefore, optimization of these parameters was studied; (1) Flux, (2) Backwashing and (3) Relaxation patterns. The job was done by using Box-Behnken Design Model (BBDM) (Response Surface Methodology (RSM)). The bench scale MBR was installed at wastewater Technology Lab of University. Sewage Treatment Plant, Islamabad provided the mixed liquor suspended solids (MLSS) which was acclimatized with real domestic wastewater (UET, Taxila) for a period of 30 days. To get the medium strength raw water, the half an hour’s pre-sedimentation was allowed. Chemical oxygen demand (COD) of 390.6 ± 25.3 mg/L was recorded initially. The sludge retention time (SRT) was maintained at 28 days which resulted in MLSS concentration range of 7000 and 8000 mg/L. The influence and interaction of flux, backwashing and relaxation was examined and regression models were recognized. The optimization of these parameters was achieved by BBDM. At the same time membrane fouling and permeate quality was analyzed. As a result, flux backwashing and relaxation were predicted as 18.57 LMH, 9.70 sec and 90 sec respectively. The predicted values of TMP, COD, NH3-N, TN and TP were checked and found close to the predicted ones i.e., 21.1058 (KPa), 86.0786%, 72.2403%, 80.6827 and 62.2122% respectively.