2013-02-25 DOI: 10.3724/SP.J.1145.2013.00184 http://www.cibj.com/ 应用与环境生物学报 Chin J Appl Environ Biol 2013，19 ( 1 ) : 184-188

Membrane Fouling in Microfiltration of Sanitary Landfill Leachate for Removals of Colour and Solids Emad S. M. Ameen1*, Abdullrahim Mohd Yusoff1, Mohd Razman Salim1, Azmi Aris2 & Aznah Nor Anuar2 (1Water Research Alliance, Institute of Environmental and Water Resource Management, Faculty of Civil Engineering, Universiti Teknologi Malaysia, Johor Bahru 81310, Johor, Malaysia) (2Department of Environmental Engineering, Faculty of Civil Engineering, Universiti Teknologi Malaysia, Johor Bahru 81310, Johor, Malaysia)

Abstract In this research, the treatability of solids from sanitary landfill leachate by microfiltration membrane was investigated and the fouling of the membrane was carefully studied. Continuous microfiltration process was carried out for 21 h in experimental system involved coagulation with Moringa oleifera followed by filtration using submerged hollow fibre microfiltration membrane (MFM). Coagulation with M. Oleifera, air diffusers and back fush technique were used for preventing or alleviating fouling of the membrane. The hollow fibre MFM showed high removals of 98%, 91% and 99% for turbidity, colour and total suspended solids respectively. It was obtained at the beginning of the filtration. However, quality of the filtrate rapidly declined during the filtration process. Fouling was found to proceed according to the classical cake filtration model. Coagulation with M. Oleifera as well as the back-fush technique could not fully restore the deterioration occurred to the membrane. Fig 4, Tab 3, Ref 20 Keywords coagulation; leachate; membrane fouling; microfiltration; solids removal CLC X705

The major environmental problem usually associated of throughput of a membrane device as it becomes chemically or with landfill leachate production is the heavy contamination of physically changed by the process fuid [8]. The membrane fouling [1-2] nearby existing underground and surface waters . Thereby, with a consequent reduction in specific flux is considered as a it is imperative that the generated leachate must be collected major limitation of the membrane filtration process. It is caused and efficiently treated, before being discharged back to the by the gradual build-up on the membrane surface [9]. Membranes environment. In many cases, stabilized leachate from biological can be fouled by natural organic matter (NOM) overtime, leading stage still shows high chemical oxygen demand (COD) values to loss in water production and requiring more frequent cleaning. (500-1 500 mg/L) because the 500-1 000 molecular weight fulvic- In most membrane filtration processes, fouling occurs due to like fraction increases with landfill age. Therefore, an additional solute adsorption, particle interception or membrane blocking. [3-5] treatment step after a biological treatment is often required . As a result, coagulation/flocculation is often used as pretreatment Membrane filtration has been widely used in the separation [10] to increase NOM removal and to control membrane fouling . and purification of water and wastewater. It has been considered The most important factors affecting membrane fouling are as a promising solution to treat aerobic-anaerobic effluent to the membrane characteristics, particle or solute properties meet the increasingly strict discharge standards as it could and operating conditions [11]. Alleviating membrane fouling remove physical, chemical and microbiological contaminants [6]. is therefore the most important course to achieve optimum Hollow fiber MFM becomes an interesting separation technique operations. In order to control cake formation, two types of since reliable separation of particles of size range 0.02-10 mm is action can be undertaken: (a) prevent the particles from reaching difficult and not economical by the other separation methods such the membrane; these include the use of air diffusers under the as sedimentation, centrifugation and depth filtration [7]. However, membrane, filtration aids, coagulants, and electro-filtration and membrane fouling during a filtration may markedly reduce the (b) flush the particles out; periodic backwashing, ultrasound filtration flux, decrease product quality and consequently increase fields, and pulsated flow are intended to remove the particles the operating costs. Fouling is the term used to describe the loss already located in the membrane or at its surface [12]. In recent Received: 2012-06-29 Accepted: 2012-08-06 years, studies showed that membrane filtration processes in ** Corresponding author (E-mail: [email protected]; emad.alhajar@ gmail.com) combination with physicochemical processes, such as adsorption 185 19卷 Emad S. M. Ameen, et al. or coagulation could effectively alleviate membrane fouling [6, 13-14]. 1.2 Experimental system Pre-treatment of the process stream to either remove or modify The experimental system shown in Fig. 1 is consisted of: potential foulants is an effective method for reduction of flux cylindrical tank having a capacity 30 L (Diameter 310 x Height decline [15-17]. In this study an experimental system involving 400 mm) in which the coagulation process with M. oleifera was physicochemical processes was developed to investigate the carried out, filtration tank having a capacity 30 L (L 300 x D efficiency and the foulants of submerged hollow fibre MFM in the 200 x H 500 mm), hollow fiber MFM and diffusers for aeration. removal of solids from sanitary landfill leachate. For the purpose Filtered water was produced by providing suction pressure using of preventing or alleviating fouling of the membrane, coagulation Master Flex pump. with M. Oleifera, air diffusers and back flush technique were 1.3 Methods Microfiltration of Leachate Sample: Raw leachate sample used. was treated with an effective dose (175 mg/L) of M. oleifera 1 Material & methods stock solution previously determined before it discharged into filtration tank to filter it through submerged hollow fibre MFM. 1.1 Material The filtration tank was provided with 3 diffusers installed under 1.1.1 Leachate samples Raw leachate samples were obtained the membrane to generate cross-fow stream of air bubbling. The from Air Hitam Sanitary Landfill located in Selangor State of air bubbling prevents the build-up of particles on the membrane Malaysia, which handles domestic solid waste. The leachate surface and avoids the fouling of the membrane that resulted from samples were taken in plastic containers; the cap was closed the cake layer formation. The coagulation-filtration process were carried out at room temperature of (26±1) ℃ and continued for 21 tightly in order not to lose CO2 produced from the microbial h. Raw leachate and filtrated samples were analysed for turbidity, action that may have occurred or not to gain CO2 or other gases [18] when exposed to air. The sample was transferred directly to colour and total suspended solids (TSS) . The fux and suction the laboratory and refrigerated at 4 ℃ until the time of the pressure were also measured periodically. Back-fush technique [18] for 25 min using distilled water was adopted after 16 hours of experiment to minimize microbiological decomposition of solids . commencing the microfiltration process. This technique was used Characteristics of raw leachate sample are shown in Table 1. as a measure to recover the membrane fouling. Table 1 Characteristics of raw leachate sample Parameter Raw leachate Turbidity (NTU) 1815 Colour (TCU) 26350 Total Suspended Solids (TSS, ρ/mg L-1) 1.51

1.1.2 Microfiltration membrane The hollow fibre MFM used in this study was manufactured by Toyota Tsusho Corporation, Tokyo-JAP, model UMF022421. It comprises hollow fibres with 0.1 mm surface pores and membrane area of 0.211 718 m2. 1.1.3 Moringa oleifera M. oleifera is a tropical plant; the seed has excellent coagulation properties for treating water and wastewater. The mechanism of coagulation with M. oleifera appears to consist of adsorption and neutralization of the colloidal charges ion [19]. The M. oleifera seeds used as coagulant Fig. 1 Schematic diagram of the physicochemical experimental in this study were obtained from Malaysia. The wings and coat system of dry M. oleifera seeds have been removed and the kernels were 1. Coagulation tank; 2. Filtration tank; 3. Microfiltration membrane; 4. Air ground to fine powder. The oil then was extracted using Hexane diffusers; 5. Suction pump; 6. Stirrer; 7. Manual valve; 8. Pressure gauge; 9. solvent. A stock solution of 10 000 mg/L was prepared to be used Effuent (fux) tank as coagulant.

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2 Results & discussion The pressure remained constant for one hour while the turbidity The operating parameters of the microfiltration process are increased again to 150 NTU at 4.5 h due to the second membrane shown in Table 2. deterioration. Turbidity then decreased gradually with the time to reach 34 NTU at 13 h. Filtrate quality after that declined Table 2 Operating parameters for microfiltration process Operating parameter Range of value with time to be 44 NTU at 16 h despite the increase in suction Suction pressure 13.3-46.7 kPa pressure, which indicated the third deterioration in the membrane -1 Effuent 4.2-0.38 L h fabric. The MF membrane was backwashed. Filtration was then Flux 18-1.6 L m-2 h-1 commenced and the turbidity of the effluent was found 110 2.1 Variation of pressure-flux with time NTU at 17 h and 53 NTU at 18 h. Turbidity after that increased Variation of pressure and flux with time is a consequence gradually with the time to be 99.3 NTU at 21 h, which indicated of the cake layer formation resulted from the build-up of micro the fourth fouling or deterioration in the membrane. floc particles on membrane surface. Flux of the microfiltration Colour of the raw leachate was 26 350 TCU. Quality of -2 -1 process started with 18 L m h . It then decreased sharply during the filtrate started with 7 660 TCU and then decreased rapidly the initial three hours followed by gradual decrease to reach a with time to reach the lowest value of 2 460 TCU after one and -2 -1 minimum value of 1.6 L m h at 16 h. The fux was improved half hour. The pressure remained constant for one hour while -2 -1 to 2.66 L m h after back-washed of the membrane and then it the colour increased to 4 020 TCU due to the first fouling or -2 -1 declined again with time to be 1.8 L m h at 21 h. Microfiltration deterioration in the membrane fabric. The colour then fuctuated, process started with 13.3 kPa that increased sharply during the increased and decreased with time. The membrane was therefore initial two hours. The pressure then gradually increased with backwashed at time 16 h. Colour of the filtrate was found 4 440 time to reach highest value of 46.7 kPa at 16 h. The pressure TCU at 17 h. The colour then decreased sharply with time to declined to 42.0 kPa after backwash of the membrane. It then 2820 TCU at 19 h and increased again with time to be 3 000 increased gradually to 45.3 kPa at 21 h. Variation of pressure-fux TCU at 21 h, which indicated a fouling in the MF membrane. The with time is shown in Fig. 2. sudden increase in turbidity-colour was due to the membrane 2.2 Variation of turbidity-colour with time deterioration that might be resulted from the stretching of the MF membrane decreased the turbidity of raw leachate from membrane fabric; breaking of the cake layer formation as the 1 815 to 350 NTU at the starting time. Turbidity then decreased suction pressure increased or such a substance in the leachate rapidly to the lowest value of 30 NTU after one and half hours might adversely affected the membrane structure. Variation of due to the build-up of particles on the membrane surface. The turbidity and colour with time is shown in Fig. 3. pressure remained constant for one hour while the turbidity of the 2.3 Variation of TSS with time effuent increased to 130 NTU at 2.5 h due to the first membrane TSS of raw leachate was 1.51 mg/L. TSS of the fux started deterioration. Turbidity after that improved to 115 NTU at 3.5 h. with 0.065 mg/L and then decreased with time to the lowest value

Fig. 2 Variations of pressure and fux with time

应用与环境生物学报 Chin J Appl Environ Biol http://www.cibj.com/ 187 19卷 Emad S. M. Ameen, et al. of 0.012 mg/L after 1.5 h. TSS varied with time along a similar Table 3 The highest removals achieved by hollow fibre trend as turbidity as these parameters are related to each other as microfiltration Raw leachate Removal Parameter Filtrate shown in Fig. 4. The increase in TSS of the effuent might be due sample (r/%) to the fouling or deterioration in membrane fabric. Turbidity (NTU) 1815 30 98 Colour (TCU) 26350 2420 91 2.4 Performance of hollow fibre microfiltration Total Suspended Solids (TSS, ρ/mg L-1) 1.51 0.012 99 membrane found to proceed according to the classical cake filtration model Filtration process was carried out continuously for 21 h; due to formation of agglomerated particle on top of the primary the suction pressure varied from 13.3 kPa to 46.7 kPa while the membrane. This result was corresponding to the finding reported -2 -1 fux varied from 18 to 1.6 L m h . The highest removals of 98%, by other researcher [20]. The membrane fouling with a consequent 91% and 99% for turbidity, colour and TSS respectively were reduction in specific flux was considered as a major limitation recorded (see Table 3). It was recorded at the beginning of the of the membrane filtration process. It was caused by the gradual filtration process (1.5 h). The quality of the filtrate declined (foul) build-up on the membrane surface of a fouling layer, which may at various intervals of 2.5, 4.5, 16 and 21 h. consist of colloidal particles, iron and/or manganese oxides, and a During the microfiltration process, the flux decreased biofilm, or may be due to inorganic scale formation [9]. The other gradually with the time due to cake layer formation from the fouling that declined the effuent quality was either, a permanent colloidal particles build-up on the membrane surface. This physical deterioration affected the membrane fabric irreversibly indicated a physical fouling in the membrane. Flux decline was resulted from high suction pressure or exists of recalcitrant

Fig. 3 Variations of turbidity and colour with time

Fig. 4 Variation of TSS with time

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