Asian Institute of Technology School of Environment, Resources & Development Environmental Engineering & Management Membrane Fouling Studies in Suspended and Attached Growth Membrane Bioreactor Systems Kwannate (Manoonpong) Sombatsompop Examination Committee: Prof. C. Visvanathan (Chairman) Prof. Ajit P. Annachhatre Prof. Jy S. Wu Prof. Sudip K Rakshit Dr. Oleg V. Shipin 1/36 K. Sombatsompop-May 2007 1/36
Membrane Bioreactor Bioreactor System System Membrane Influent Treated water Clarifier Sludge storage Aeration tank Sludge return Excess sludge 2/36 /36 2 K. Sombatsompop-May 2007
Advantages and disadvantages of Advantages and disadvantages of membrane bioreactor membrane bioreactor Air Permeate Wastewater Wastewater � High effluent quality Biological Biological � Small size reactor reactor � Flexible in the operation Membrane immerged MBR � Low sludge production module � Removal of infectious pathogens Fouling Limitation of MBR : Fouling Limitation of MBR : • A reduction of the membrane performance • A decrease of flux • An increase in filtration resistance • Membrane cleaning requirement 3 3/47 /47 3/36 /36 3 K. Sombatsompop-May 2007
Attached growth bioreactor Attached growth bioreactor Biomass growth on small carrier materials that Advantage for attached move along with the water in the reactor growth bioreactor Screen Better oxygen transfer High organic removal ability Influent Effluent Relatively short HRT Carrier Being more compact (Tavares et al, 1994; Ødegaard et al,1994; Ødegaard 2000 ) Air Attached growth reactor 4/36 /36 4 K. Sombatsompop-May 2007
Objectives of the study Objectives of the study To examine suitable test conditions and to select suitable media for attached growth reactor To investigate effects of operating conditions, such as HRT and MLSS on membrane performance, fouling characteristics, EPS production and sludge properties To compare membrane fouling behavior of attached and suspended growth MBRs 5/36 /36 5 K. Sombatsompop-May 2007
Scope of the study Scope of the study • Synthetic wastewater with a constant COD value of 500 mg/L • Five different types of media polyethylene bead (PB), polyethylene granule (PG), polyethylene sheet (PS), cylindrical polypropylene (CP) and polyethylene sponge (S) • Effect of operating conditions; 1. HRT was varied at 2, 4, 6 and 8 h. 2. MLSS was altered at 6, 10 and 15 g/L. • Sludge characteristics, EPS production, fouling rate, cake resistance and microscope observation • Removal efficiency of COD, and nitrogen compounds 6/36 /36 6 K. Sombatsompop-May 2007
Preliminary study Preliminary study To examine suitable test conditions and to select suitable media for attached growth reactor 7/36 /36 7 K. Sombatsompop-May 2007
Research methodology Research methodology Preliminary Study Preliminary Study EPS Extraction analysis Batch reactor EPS Extraction analysis Batch reactor Variation of Variation of re-suspended solution re-suspended solution Suspended growth reactor Attached growth reactor Suspended growth reactor Attached growth reactor Variation of Variation of centrifugation speed Variation of centrifugation speed Variation of media media Variation of Variation of centrifugation time centrifugation time EPS production Removal efficiency EPS production Removal efficiency 8/36 /36 K. Sombatsompop-May 2007 8
Media types Media types Polyethylene Polyethylene Cylindrical Cylindrical Sponge(S) Sponge(S) beads (PB) beads (PB) polypropylene (CP) polypropylene (CP) Polyethylene Polyethylene granule (PG) granule (PG) Polyethylene Polyethylene sheet (PS) sheet (PS) 9/36 /36 9 K. Sombatsompop-May 2007
Experimental set- -up up and operation and operation Experimental set Conditions: pH 7 pH 7- -8 8 DO 2- -4 mg/L 4 mg/L Conditions: DO 2 COD 500 mg/L HRT 6 h. COD 500 mg/L HRT 6 h. SRT 10 d. MLSS 4000 mg/L SRT 10 d. MLSS 4000 mg/L F/M 0.1 kgCOD/kgMLSS.d kgCOD/kgMLSS.d F/M 0.1 Timer Motor Air diffuser Control (no media) PB PG CP PS S Air Suspended growth Attached growth reactor reactors 10/36 /36 10 K. Sombatsompop-May 2007
A. Selection of Media Type for Attached Growth Reactor A. Selection of Media Type for Attached Growth Reactor Question and Recommendation Question and Recommendation Table 4.1 Removal efficiency of COD and TKN in batch reactors Batch System Sampling COD TKN reactor mg/L % removal mg/L % removal point - Influent 460 - 30 - Control Suspended Effluent 23 95 6 79 (no media) growth PB Attached Effluent 23 95 4 88 growth PG Attached Effluent 22 95 3 90 growth PS Attached Effluent 21 95 4 86 growth CP Attached Effluent 22 95 4 86 growth S Attached Effluent 25 94 5 83 growth 11/36 /36 11 K. Sombatsompop-May 2007
Question and Recommendation Question and Recommendation A. Selection of Media Type for Attached Growth Reactor Selection of Media Type for Attached Growth Reactor A. 25 EPS compositions (mg/gVSS) Protein Carbohydrate 20 Ratio of Protein/Carbohydrate 15 10 5 0 l B G P S S o P C r P P t n o C Media types Figure 4.2 EPS compositions in different media types 12/36 /36 12 K. Sombatsompop-May 2007
Question and Recommendation Question and Recommendation A. Selection of Media Type for an Attached Growth Reactor Selection of Media Type for an Attached Growth Reactor A. 10000 2 of media surface) 1000 100 EPS (mg/m 10 1 PS PG PB CP S (CP) Media types Figure 4.4 EPS content in terms of media surface at different media types Cylindrical polypropylene was selected due to; floating, well mixing, high surface media and non biodegradable nature. 13/36 /36 13 K. Sombatsompop-May 2007
Conclusions for Preliminary study Conclusions for Preliminary study • No significant difference in COD removal efficiency was found between the suspended and the attached growth systems. • The average TKN removal efficiency in the attached growth system was in the range of 83 to 90%. • There was no significant difference in EPS production in the suspended and the attached growth systems. • The productions of EPS and biofilm formation were affected by shape and size characteristics of media used. Cylindrical polypropylene (CP) was most suitable. 14/36 /36 14 K. Sombatsompop-May 2007
Laboratory- -scale MBR study scale MBR study Laboratory To investigate effects of operating conditions, such as HRT and MLSS on membrane performance, fouling characteristics, EPS production and sludge properties To compare membrane fouling behavior of attached and suspended growth MBRs 15/36 /36 15 K. Sombatsompop-May 2007
Laboratory- -scale MBR study scale MBR study Laboratory Laboratory-scale MBR study Laboratory-scale MBR study Suspended growth MBR Attached growth MBR Suspended growth MBR Attached growth MBR Operational systems Fixed media Moving media Fixed media Moving media Operational Variation of HRT Variation of MLSS Variation of HRT Variation of MLSS conditions Operational analysis Fouling Sludge Microscope Fouling Sludge Microscope Removal efficiency Removal efficiency characteristics characteristics observation characteristics characteristics observation 16/36 /36 16 K. Sombatsompop-May 2007
Experimental set- -up up of MBR of MBR Experimental set Question and Recommendation Question and Recommendation Timer Pressure 3 gauge 2 Air line Solenoid 1 Effluent Storage valve tank Level Pump control AG-MBR AG-MBR SG-MBR Moving media Fixed media Manometer Hollow fiber Control tank membrane Mitsubishi Rayon Pore size - 0.1 µm Surface area- 0.42 m 2 Baffle Air flow meter Note: SG: Suspended growth AG: Attached growth Air diffuser 17/36 /36 17 K. Sombatsompop-May 2007
Results and Discussions Results and Discussions Question and Recommendation Question and Recommendation Effect of Hydraulic Retention Time (HRT) Effect of Hydraulic Retention Time (HRT) Table 4.6 COD removal in the MBRs with varying HRT COD (mg/L) (%Removal efficiency) Item HRT 8 h HRT 6 h HRT 4 h HRT 2 h 504 507 522 435 Influent Effluent of suspended growth 16 12 19 15 MBR (97) (98) (96) (97) 13 10 16 10 Effluent of attached growth MBR with moving media (97) (98) (97) (98) Effluent of attached growth 19 15 23 25 MBR with fixed media (96) (97) (96) (94) 18/36 /36 18 K. Sombatsompop-May 2007
Effect of HRT Effect of HRT Question and Recommendation Question and Recommendation Table 4.7 TKN removal in the MBRs with varying HRT TKN (mg/L) (%Removal efficiency) Item HRT HRT HRT HRT 8 h 6 h 4 h 2 h Influent 57.5 56.8 45.4 44.8 2.8 1.3 1.7 2.8 Effluent of suspended growth MBR (95) (98) (96) (94) Effluent of attached growth MBR with 2.9 1.3 1.7 2.5 moving media (95) (98) (96) (94) Effluent of attached growth MBR with fixed 3.3 1.9 2.1 3.4 media (94) (97) (95) (92) 19/36 /36 19 K. Sombatsompop-May 2007
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