Energy efficient submerged UF/MF system utilizing reciprocating inertia for wastewater treatment

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1 Energy efficient submerged UF/MF system utilizing reciprocating inertia for wastewater treatment Jaeho Ho, Shaleena Smith, Gyu Dong Kim and Hyung Keun Roh Doosan Hydro Technology, Tampa, USA

2 Why Membrane Bioreactors? Smaller footprint Consistent better water quality - Solids-free effluent Operational reliability - Efficient nutrient removal Phased expansion - Installation flexibility Wastewater Sludge MBR effluent* 2 * 1 Jeffrey, C. Membrane Applications for Wastewater Reuse in the Middle East. Enviro Arabia * 2 Williston, A. and Gellner, T. MBR activated sludge truths: the real information concerning O&M associated with MBR activated sludge. OWEA State Conference 2012.

3 The Challenge Energy intensive air scouring for membrane cleaning Additional 0.2 ~ 0.3 kwh/m 3 required for air scouring 6% 9% 17% 11% 57% Flat Sheet MBR * Rest MBR Membrane Aeration Biology Aeration Mixers Recirculation 11% 43% 15% 17% 1% 5% 3% 3% 11% KWh/m kwh/m 3 3 3% 16% 1% 35% 36% Rest Membrane aeration Biology Aeration Feed Pumps Permeate Pump Propulsors Rest MBR 3% 3%1% 5% 11% 16% 15% 35% 36% *1 Krzeminski, P., J.H. van der Graaf, and J.B. van Lier, Specific energy consumption of membrane bioreactor (MBR) for sewage treatment. Water Science Technology, (2): p % 11% 17% 0.84 kwh/m 3 Hollow Fiber MBR * Multi-Tubular MBR * 3%1% Membrane Aeration Biology Aeration Influent Pumps Feed Pumps Permeate Pumps Membrane cost ($7 ~ $9/ft 2 )** Low flux (20 10,000 mg/l) *2 Menniti, A., Erdal, Z., Crawford, Z. and Johnson, B., The evolution of MBR design to minimize capital cost and optimize energy efficiency, WEFTEC 2011, p

4 Innovative Approaches Inertia Force on Membrane Fibers through Reciprocating Motion as a Solution to Energy Intensive Air Scouring (rmbr) Eliminate air scouring system (savings in OPEX and CAPEX) Membrane oscillation causes the fibers to move More effective membrane fouling control compared to indirect air scouring Prevent/Delay sludge accumulation throughout membrane fibers Increase interval time between CIP cleans Target Goal More than 50% energy savings (<0.15 kwh/m 3 ) and flux increase (>30 LMH) in MBR operation 4

5 Air scouring vs. Inertia Air Scouring Inertia via reciprocation Pros Cons No moving parts Maintenance free (?) Energy intensive (indirect cleaning) DO in RAS Energy effective (direct cleaning) No blowers, No DO in RAS Moving parts!!! Bearing replacement

6 LENA (Less Energy No Aeration) System Gear motor with belt connected rotor: Gear motor provides low RPM and high torque to move the vibration frame back and forth smoothly. Linear motion bearing on rail: Linear plane bearing with self lubrication (works with dirt). Friction coefficient is high (0.15 vs for ball bearing) and uses 80% power The rest of energy needed for the drag force by the membrane fiber in the mixed liquor [ rmbr Pilot Mechanical Setup ] [ rmbr Pilot Setup with Tank Modifications ]

7 LENA MBR System Configuration NRCY Sludge recirculation 3-4Q Effluent, Q Influent M M MBR MBR Blower Only one or no internal recirculation pump for both N and P removal Blower High DO Sludge recirculation 3-4 Q Overflow [ Conventional UCT MBR ] Sludge Treatment Effluent Influent M M MBR No blower (Post anoxic zone): Complete denitrification No DO in RAS: Direct return to anoxic or anaerobic Return Sludge Overflow Blower Sludge treatment [ Reciprocation MBR ]

8 LENA MBR Pilot Operation [ Membrane Characteristics and Operation Conditions] Material Parameter PVDF Value/Setpoint Pore size 0.4 µm Total surface area 45 m 2 (484 ft 2 ) Operation flux Reciprocating frequency L/m 2 h ( gfd) 0.38, 0.43 and 0.48 Hz Reciprocating amplitude 38, 44 and 57 mm (1 ½, 1 ¾ and 2 ¼ ) MBR tank feed flow rate Filtration: Idling CEB CIP HRT SRT 5 ~ 8Q (32-40 gal/min) 9 min: 1 min Every 1,000 filtration cycles (weekly) Not done for 8 months 4 ~ 7 h 20 ~ 30 d

9 Membrane Performance (I)

10 Membrane Performance (II)

11 High Flux Test Operation Conditions Permeability Flux TMP 40 LMH continuous operation for 4 weeks MLSS: 10,000 ~ 12,000 mg/l 9 min filtration / 1 min idling Weekly CEB No backpulsing CEB CEB CEB 44 mm amplitude 0.43 /s frequency

12 Biological Performance (I)

13 Biological Performance (II)

14 Biological Performance (III)

15 Cumulative Energy Consumption (kwh) Power Consumption 140 Conventional (20 LMH): 0.22kWh/m (30 LMH) kwh/m (20 LMH) 0.08 kwh/m 3 (25 LMH) 0.07 kwh/m 3 (35 LMH) kwh/m 3 (40 LMH) kwh/m Cumulative Permeate Volume (m 3 )

16 LENA MBR Processes An Ax Ox IR pump 1 Overflow MBR Feed pump Filtration pump For N & P removal: Membrane overflow to anoxic Membrane tank serves as a post anoxic One internal recirculation from anoxic to anaerobic High N & P removal with one less internal recirculation compared to N & P removal processes (e.g., A2O, UCT, etc.) Ax Overflow An MBR Feed pump Filtration pump For N removal: Membrane overflow to anoxic No internal recirculation High nitrogen removal due to low DO in the overflow from secondary anoxic membrane tank Overflow An Ax Ox MBR Feed pump Filtration pump For N & P removal (less strict P limits): Membrane overflow to anaerobic No internal recirculation form aerobic to anoxic No internal recirculation required for N & P removal

17 LENA UF/MF applications Rapid mixing w/chemicals LENA UF for flocculation and filtration For N & P removal: Membrane overflow to anoxic Membrane Submerged tank LENA serves UF/MF as a post system anoxic for One Enhanced internal recirculation from anoxic to anaerobic High N & P removal with one less internal recirculation compared coagulation/flocculation/filtration to N & P removal processes (e.g., A2O, UCT, etc.) SWRO pretreatment Potable water treatment Selenium reduction and removal from mining water The integrated LENA UF/MF with chemical precipitation system can significantly reduce footprints and improve filtration performance compared to conventional chemical coagulation/flocculation and settling (or filtration) process. Also suitable for filtration where it is necessary to maintain either anoxic or anaerobic conditions with less turbulence.

18 Conclusions 1. The first pilot scale rmbr system has been successfully demonstrated with enhanced biological N and P removal. 2. Inertia force on membrane fibers created by reciprocation motion of membrane cassette prevents membrane fouling effectively. 3. More than 90% COD, TN and TP removal at 6 ~ 7 h HRT without chemical additions consistently. 4. More than 50% energy savings in membrane reciprocation compared to membrane air scouring. 5. Higher operating flux ( ~ 40 LMH) at 10,000 mg/l MLSS reduces membrane cost. 6. No air scouring in MBR benefits CAPEX and OPEX.

19 Acknowledgement Howard F. Curren Advanced Wastewater Treatment Plant City of Tampa, Florida Doosan Heavy Industries & Construction Co., Ltd. Co-Authors: Jaeho Ho, Ph.D. Jaren Patamasank Petia Tontcheva, MS Gyu Dong Kim, Ph.D. Hyung Keun Roh, Ph.D.

20 Let it shake itself out Thank you for attention Any questions?