Control of membrane fouling by Hydrogen Sulfide (H2S) diffusion ...

have moderate correlation due to lowamount. According to the currentresearches, proteins are the most importantfactor of membrane fouling (Meng et al.,2006).Soluble microbial product (SMP)SMP are the large amount of solubleorganic substances that are produced frombacterial populations in bioreators. SMPlevel is extremely important for biologicaltreatment process as treatment efficiencyand effluent quality highly depends on SMPamount in treatment reactors. It is wellestablished that majority of soluble organicsubstances come from SMP in effluent inbiological treatment systems and itsconcentration set up the discharge level ofchemical oxygen demand (COD) and totalorganic carbon (TOC) in effluent.Furthermore, some SMP have certaincharacteristic like toxicity and metalchelating properties which affect themetabolic activities of microorganisms bothin receiving water and in treatment process.In some case, it lessens the specificrespiration rate of microorganisms.Therefore, for better efficiency of treatmentsystems, less concentration of SMP isdesirable (Liang et al., 2007).SMP could be again categorized into two asutilization associated products and biomassassociated products. Although humicsubstances (humic and fulvic acids),carbohydrates and proteins have beenidentified successfully as major componentsof SMP, it is still unclear of its precisecomposition (Liang et al., 2007).However, most of previous studiesconcentrated on SMP in conventionalbiological treatment plants but fewer havebeen focused to grasp the impact of SMP inMBR. It is found from study that dependingof the operation condition SMP are liablefrom 26 to 52% of membrane fouling inmicrofiltration and ultrafiltrationmembranes (Liang et al., 2007).Materials and MethodHydrogen Sulphide (H 2 S) diffusionAir and mixture of air & H 2 S was sprayedinto sludge for getting differentconcentration of H 2 S in sludge. Pressure andflow rate were 2 bars and 400 ml per minrespectively and was aerated for 15 min andafter then kept it for 10 min forhomogeneous distribution of H 2 S in sludge.High concentration of H 2 S (2000 mg/l) hasbeen diluted by mixing of compressed air toget a certain concentration of H 2 S. Two gasflow meters were used to control the air andH 2 S gas flow and connected to the gascylinder by plastic tube line. This mixture ofgases has been applied to feed by diffuserwhich was connected at the end of sourcetube. Concentration of 25 ppm (0.075 mgH 2 S/g biomass), 50 ppm (0.15 mg H 2 S/gbiomass) and 100 ppm (0.3 mg H 2 S/gbiomass) of H 2 S were sprayed in threesamples with flow rate of 400 ml/min andeach sample is amount of 2 liters. Only airwas pumped into the sludge to get zeroconcentration H 2 S sample for same durationwith flow rate 400 ml/l. These samples wereanalyzed for eEPS, SMP, ZP and pH.H2S TankAir TankRegulatorRegulatorH2SFlowmeterAirFlowmeter2 mtubeline2 L Glass CylinderFigure 1: Schematic setup for H 2 S diffusionDead End FiltrationThe whole experiment was consisted ofdead end filtration cell, reservoir,compressed air and computer program formeasuring weight of collected permeate.Around one liter of aerated sludge is pouredin about 2 l volume closed feed reservoirand pump to dead end filtration cell (110 mlvolume capacity, 1.59 X 10 -3 m 2 membrane2