EVALUATION OF CERAMNIC MBR TECHNOLOGY FOR WATER REUSE James F. DeCarolis, P.E., Black & Veatch, 300 Rancheros Drive, Suite 250, San Marcos, CA, 92069, decarolisjf@bv.com, Ph: 619-204-2537 Scott Freeman, P.E., Black & Veatch, Kansas City, MO. Gary Hunter, P.E., Black & Veatch, Kansas City, MO. Bikram Sabherwal, Black & Veatch, Kansas City, MO. Sock-Hoon Koh, Black & Veatch, Singapore. Sandeep Sathyamoorthy, Black & Veatch, Walnut Creek, CA. Abstract An 8-week demonstration test of the Meiden Ceramic Flat Sheet (CFM) MBR is ongoing at the City of Escondido s Hale Avenue Resource Recovery Facility (HARRF) located in Escondido, California. The primary goal of the testing is to demonstrate the CFM membrane can meet filtration requirements (i.e. Title 22 Filtration Requirements) of the CDPH (now Division of Drinking Water) Water Recycling Criteria. This paper presents membrane operational and water quality performance data collected over a 30 day reporting period. Introduction The use of ceramic membranes for water reuse is relatively new in comparison to the long history and experience with the evaluation/implementation of polymeric based membrane systems for various reuse applications (Freeman et al., 2008; Adham & DeCarolis 2004; DeCarolis et al., 2009). In general, ceramic membranes have several advantageous properties when compared to polymeric membranes. Such properties include higher mechanical stability (allowing higher pressures), relatively narrow membrane pore size distribution, high chemical stability (resulting in longer membrane life and lower fiber breakage). In the past few years, Meidensha Corporation (Meidensha), Tokyo, Japan, has incorporated their ceramic flat-sheet membrane (CFM) into a submerged membrane bioreactor (MBR) configuration. In 2013, Meiden Singapore (fully owned subsidy of Meidensha) began operation and testing of 1 MGD capacity MBR demonstration plant using the CFM technology at the Jurong Water Reclamation Plant (located in Singapore) which treats both municipal and industrial wastewater. Results of the demonstration testing showed the Meiden MBR could treat industrial water and produce a high quality effluent that can be reused for industrial uses after being blended with MBR permeate produced from municipal wastewater (Kekre et al., 2015). Black & Veatch is conducting demonstration testing of the CFM MBR treating municipal wastewater. The primary goal of the testing is to demonstrate the CFM membrane meets filtration requirements (i.e. Title 22 Filtration Requirements) of the California Department of Public Health (CDPH, now called Division of Drinking Water, DDW) Water Recycling Criteria under the Title 22 Code of Regulations which requires turbidity of: 0.2 NTU 95% of the time within 24 hours; 1
0.5 NTU 100% of the time (CDPH 2013, 2014). The City of Escondido (City), California is sponsoring the demonstration testing of CFM technology. Testing of the CFM membrane is being done using a MBR pilot system, which is currently operated on primary effluent from the City s municipal wastewater treatment plant (i.e. Hale Avenue Resource Recovery Facility-HARRF). This paper presents initial operational and water quality performance data from the on-going demonstration testing of the Meiden Ceramic MBR, which began steady-state operation in September 2015. The paper is organized as follows: Introduction Demonstration Study Objectives Materials and Methods MBR Performance Monitoring Results Next Steps Summary Acknowledgments Demonstration Study Objectives The main objective of the Meiden MBR demonstration study is to evaluate the ability of the Meiden CFM membrane to comply with filtration performance requirements per California s Title 22, Section 60301.320. The overall study objectives are being achieved by operating a pilot system on primary wastewater effluent produced at the City s HARRF. Specific study objectives include: Demonstrate the CFM membrane can meet Title 22 turbidity requirements via continuous online filtrate turbidity monitoring; Collect operational performance data from the CFM membrane including membrane fouling performance and air scouring requirements; Evaluate water quality performance of the MBR system via the implementation of detailed sampling plan; Demonstrate the Meiden CFM MBR can achieve minimum 1 log (90%) removal of seeded virus at the 50th percentile; Assess effectiveness of manufacturer recommended membrane cleaning protocols. 2
Materials and Methods Pilot Testing Site The pilot testing site for this study is HARRF, located in Escondido, California. HARRF is designed to treat 36 mgd, which is two times the permitted monthly average discharge flow of 18 mgd. HARRF receives municipal wastewater from the City of Escondido and the Rancho Bernardo community located in the City of San Diego. The main wastewater treatment process at HARRF consists of conventional activated sludge (CAS) and includes mechanical and bar screens, grit removal system, primary clarifiers; aeration basins, secondary clarifiers, flocculation basins, DynaSand filters, UV and chlorine disinfection. The solids handling process includes: DAF thickeners, anaerobic digesters, solids dewatering centrifuges, and an energy recovery system. Several chemicals are dosed throughout the main treatment process as summarized in Table 1. As indicated, the plant periodically practices chemically enhanced primary treatment (CEPT), which utilizes coagulant and polymer addition. During the pilot study, the use of CEPT will be tracked to evaluate the impact (if any) on the MBR pilot performance. The pilot system is located on a concrete test pad located at HARRF. The site provides sufficient influent water supply, electrical power, compressed air, and drainage lines to meet the needs of the pilot testing. During the pilot period, the MBR system will be operated with primary effluent. Primary effluent quality from samples collected between 2012 2013 as provided by the City is presented in Table 2. Table 1 HARRF Chemical Dosing Locations DOSING LOCATION CHEMICAL PURPOSE TYPICAL DOSE, MG/L Grit Chamber Inlet Ferric Sulfate Chemically Enhanced Primary Treatment 0-15 (as Fe 2 S0 4 ) Primary Clarifiers Polydyne, Clarifloc WE 1024 Chemically Enhanced Primary Treatment 0-0.3 Tertiary Filter Inlet Polydyne, Clarifloc WE 850 Improve Filter Performance 30-60 Tertiary Filter Inlet Polydyne, Clarifloc WE 888 Improve Filter Performance 1-2 3
Table 2 HARRF Primary Effluent Quality PARAMETER UNITS TYPICAL MIN MAX Alkalinity mg/l as CaCO 3 310 261 369 CBOD mg/l 158 107 247 TSS mg/l 92.1 55 165 VSS mg/l 78.2 48 127 TDS mg/l 889 811 988 TKN mg/l as N 50.2 37 58.8 Ammonia mg/l as N 40.6 34.4 46.4 Description of Pilot Plant Pilot Meiden and Fluidyne Corporation (Cedar Falls, Iowa) jointly provided the components of the MBR pilot system. The MBR pilot system includes a 2-mm static fine screen, 19,000 gallon MBR tank, 500 gallon clean water tank, and a 300 gallon chemical tank. The MBR tank consists of five separate chambers: anaerobic #1 (3,004 gallons), anaerobic #2 (2,337 gallons), anoxic (5,341 gallons) aerobic (5,341 gallons) and membrane (3,004 gallons). The system was designed for an average filtrate flow of 22 gpm and peak flow of 33 gpm. The overall biological system prior to the membranes utilizes a Fluidyne Integrated Surge Anoxic Mix (ISAM ) System. Typically, ISAM systems utilize a Sequencing Batch Reactor (SBR) in conjunction with dual anaerobic zones and a Surge Anoxic Mix (SAM) tank. For the MBR pilot system, the SBR tank is operated in continuous mode and serve as the aerobic tank. A basic flow schematic of the Meiden/Fluidyne MBR pilot system is provided in Figure 1. 4
Figure 1 Schematic of the Meiden MBR Pilot System Primary effluent is pumped to the fine screen and flows via gravity into the first anaerobic chamber. The clarified liquid and any decomposed products then pass into the second anaerobic chamber for further processing prior to passing through an underflow into the anoxic reactor. Mixed liquor from the anoxic chamber is pumped to the aerobic zone using a jet motive / recycle pump. The speed of the pump is controlled by the dissolved oxygen (DO) concentration measured in the aerobic chamber. Nitrate rich mixed liquor suspended solids (MLSS) from the aerobic zone is returned by gravity flow to the anoxic chamber for rapid denitrification. The system also allows controlled recirculation of MLSS from the anoxic tank (using manual valves off the jet / motive pump) to the anaerobic chambers to further enhance denitrification. Lastly, MLSS from the aerobic/anoxic tank enters the membrane tank via a recycled line and is returned to the aerobic tank via an underflow. Sludge wasting is conducted manually from the membrane tank and monitored by the PLC after receiving output from the MLSS sensor submerged in the membrane chamber. The system design also allows manual wasting from the anaerobic Tank #1. The membrane chamber is equipped with a dual stacked membrane unit, containing 300 full-size membrane elements for a total membrane area of approximately 1,614 ft 2. The Meiden membranes operate with an outside-in flow path and have a pore size of 0.1 µm. General specifications for the Meiden Ceramic Flat-sheet unit are provided in Table 3. A photograph of the unit being installed into the membrane chamber of the MBR tank is provided in Figure 2. 5
Table 3 Specifications of the Meiden Ceramic Flat Sheet Membrane Unit PARAMETER UNITS VALUE Commercial Designation ----------- CH250-1000TM100-U2DJ Unit Configuration ----------- 2- Level stack Number of Elements # 1 400 Membrane Type ----------- Flat-Sheet Approximate size of element (LXWXH) mm 261X6X1046 Nominal Pore Size (micron) micron 0.1 Membrane Material ----------- Alumina Active Membrane Area per element ft2 5.4 Maximum Backwash Pressure psi 8.7 Maximum Trans-membrane Pressure psi 8.7 Maximum Temperature C 60 Operating ph ----------- 2-12 1 Note: 300 membrane elements were installed in pilot system 6
Figure 2 Photograph of the Meiden Ceramic Membrane Unit during Installation Pilot Plant Operating Conditions Preliminary target steady-state operating conditions identified at the onset of the demonstration study by Meiden are provided in Table 4 below. As shown the membrane system is designed to operate with periodic back-pulse or relaxation to mitigate membrane fouling and an average flux rate of 19.6 gfd. The biological component of the Meiden MBR was designed for a MLSS in the membrane chamber of 8,000 to 10,000 mg/l and overall solids retention time (SRT) of 30 days. 7
Table 4 Specifications of the Meiden Ceramic Flat Sheet Membrane Unit PARAMETER UNITS VALUE Total HRT hours 14.4 Aerobic + Anoxic HRT hours 4.04 + 4.04 = 8.08 SRT Days 30 MLSS mg/l 8,000-10,000 Average Flux gfd 19.6 Filtration Cycle Min 9 Backwash/Relaxation Duration Sec 30 Operational & Water Quality Performance Monitoring Approach The overall approach to meeting the demonstration study objectives is to operate the Meiden MBR system on a continuous basis using primary effluent from the HARRF as the feed wastewater source for a target 60 day steady-state operating period. During this time, monitoring of operational and water quality parameters is being conducted. Examples of various operational parameters being collected over the course of the demonstration period include flows (influent, membrane backwash, membrane filtrate, internal recycle pump speed), pressures (filtrate pressure before/ backwash/relaxation and membrane cleaning), MLSS, temperature, DO, ORP, tank levels, membrane air scour flow rate, backwash/relaxation durations. The performance of the membrane system component of the MBR is being evaluated by tracking the transmembrane pressure (TMP) and temperature corrected specific flux during constant flux operation and during peak flux test conditions. Water quality samples from various locations in the MBR process are being collected and analyzed on a routine basis to assess the performance of the both the biological and membrane components of the MBR system. A key focus of the study is to demonstrate the ability of the Meiden MBR to meet the Title 22 recycled water turbidity requirements through the use of continuous online turbidity monitoring of the MBR filtrate. Other water quality parameters being monitored are categorized as follows particulate (turbidity, TSS), nutrients (inorganic nitrogen, including ammonia, nitrate, nitrite, TKN, orthophosphate, total phosphorus), organics (BOD, COD, TOC) and microbial constituents (fecal coliform, total coliform, total coliphage). Water quality samples being measured by off-site laboratories are in accordance to methods listed in the Standard Methods for the Examination of Water and Wastewater (SM), United States Environmental Protection Agency (EPA) or the American Public Health Association (APHA). Specific laboratories to be used throughout the project include the City of Escondido Water Quality Laboratory, Eurofins-Calscience, and Biovir Laboratories. Membrane cleaning is being performed per manufacturer recommended cleaning protocols after observing a significant increase of TMP (or corresponding decrease in temperature corrected 8
specific flux). The pilot system is designed to perform a cleaning automatically based on a set point increase of TMP, via set point frequency or manually initiated. Maintenance clean (MC) is typically carried out by gradual dosing of chlorine and acid (if required) through the membranes at manufacturer s recommended chemical concentration. During the demonstration study cleaning is performed with sodium hypochlorite at a target concentration of 0.1% w/w followed be a low ph cleaning using citric acid at target concentration of 0.5% citric acid. MBR Performance Monitoring Results Membrane Operational Performance Monitoring The performance data from the Meiden CFM MBR monitored over the reporting period of 10/3/15 to 11/4/15 is provided in Figure 3. During this period the system was operated with a target flux of 24.5 gfd. Back pulsing using MBR filtrate (with no chemical addition) was performed every 9 minutes for duration of 30 seconds. The backwash flow rate was approximately 2 times the filtration flow rate. Starting on 10/6/15 the system operated with little to no membrane fouling (based on the minimal change in TMP/specific flux) for a 2 week period at a target operating flux of 24.5 gfd. At the end of this period, the TMP increased sharply (approximately 2 psi) at which time an MC was performed using sodium hypochlorite. The MC was effective at reducing the TMP to the initial value and the system operated for approximately 5 days with little to no membrane fouling. After this time, the TMP started increasing steadily requiring another MC to be performed on 10/30/15. Following this MC, the system only operated for a short period (approximately 1 day) before a sharp increase in TMP was observed. Following this event, another MC was performed on 11/2/15 using sodium hypochlorite; however, it was not effective at completely restoring membrane productivity. As a precautionary measure, the flux was reduced to a target value of 16 gfd on 11/3/15 to allow time to investigate the cause of membrane fouling. Shortly after this time, a MC (not shown on Figure 3) was performed with sodium hypochlorite followed by citric acid. The results showed the citric acid was effective at reducing the TMP to initial values. This data suggests membrane fouling was due to build of inorganic foulants on the membranes. The exact cause of the fouling is currently under investigation. A potential cause is the use of ferric sulfate added in the CEPT process at HARRF. 9
Figure 3 Membrane Performance of the Meiden CFM MBR 10
Water Quality Performance Monitoring Water quality performance results of the Meiden MBR system collected over the reporting period including particulate (turbidity), organic (BOD/COD), inorganic nitrogen (ammonia, nitrate, nitrite) and microbial (total coliform, fecal coliform) constituents are provided in Figures 4, 5, 6, and 7 respectively. Figure 4 shows the Meiden CFM MBR is consistently meeting the Title 22 Recycled Water Criteria for membrane filtration with an average filtrate turbidity measured via online monitoring of 0.12 NTU. It was observed during the testing the turbidity measured by the online analyzer spiked following the performance of MC, however further investigation showed the spikes were due to residual cleaning solution in the filtrate piping and not the performance of the membrane. Figure 5 shows the influent wastewater BOD5 and COD values ranged from 163 mg/l to 300 mg/l and 274 mg/l to 555 mg/l, respectively over the reporting period. The BOD5 values measured in the MBR filtrate were < 2 mg/l and COD values measured in the MBR filtrate ranged from 3 21 mg/l, indicating the Meiden MBR achieved a high degree of organic removal. Figure 6 shows the inorganic nitrogen results including ammonia, nitrate, and nitrite measured in the influent wastewater and Meiden CFM MBR filtrate. The results show the ammonia and nitrite values measured in the MBR filtrate were all below the method reporting limit (MRL) indicating the system was fully nitrifying. The nitrate values measured in the MBR filtrate ranged from 7.5 18.7 mg/l-n indicating partial denitrification was achieved. This data indicates that denitrification could have been inhibited during the testing. Possible causes, currently under investigation, include carry over of dissolved oxygen (DO) present in the recycle streams to the anoxic chamber and the amount of available readily biodegradable COD. Figure 7 shows the results of the total coliform and fecal coliform analyses conducted on the Meiden CFM MBR system over the reporting period. Results showed the coliform concentration measured in the MBR filtrate were all below the method detection limit (MDL) of 2.2 MPN/100 ml. Based on the reported influent concentration the system achieved > 6 log removal of total and fecal coliform. 11
Figure 4 Turbidity Removal by the Meiden CFM MBR Figure 5 BOD/COD Removal by the Meiden CFM MBR 12
Figure 6 Inorganic Nitrogen Removal by the Meiden CFM MBR 13
Figure 7 Coliform Removal by the Meiden CFM MBR Next Steps Summary An 8-week demonstration test of the Meiden CFM MBR is ongoing at the City of Escondido s Hale Avenue Resource Recovery Facility (HARRF) located in Escondido, California. The primary goal of the testing is to demonstrate the CFM membrane can meet filtration requirements (i.e. Title 22 Filtration Requirements) of the CDPH (now Division of Drinking Water) Water Recycling Criteria under the Title 22 Code of Regulations as follows: 0.2 NTU 95% of the time within 24 hours; 0.5 NTU 100% of the time (CDPH 2013, 2014). Online turbidity monitoring results collected over a 30 day period has shown the CFM membrane consistently meets the above requirements with an average filtrate turbidity measured over this time of 0.12 NTU. During the testing period, the Meiden MBR operated at a target flux of 24.5 gfd with maintenance cleans conducted at intervals ranging from of approximately every 3 to 8 days. In general maintenance cleaning using sodium hypochlorite only throughout the test 14
period was effective at restoring membrane productivity; however, toward the end of the test period significant increase in TMP required cleaning with citric acid. In addition to the turbidity performance outlined above, water quality performance monitoring results showed the Meiden MBR achieved high quality filtrate quality with respect to organic (average BOD < 2 mg/l; average COD = 14 mg/l), inorganic nitrogen (average ammonia < 0.5 mg/l-n; average nitrate = 13 mg/l-n; average nitrite < 0.05 mg/l-n) and microbial contaminants (total and fecal coliform < 2 MPN/100 ml). Upon completion of the demonstration testing the remaining data generated from the study will be summarized in a final report and presented to the Division of Drinking Water (DDW). At this time, the project team will request DDW to provide conditional approval of the Meiden CFM membrane to meet Title 22 membrane filtration requirements. Additional testing of the Meiden MBR is being planned at HARRF to evaluate the long term performance of the CFM membrane. The system is also intended to be used as pretreatment to other advanced technologies (e.g. reverse osmosis, advanced oxidation) that the City of Escondido plans on demonstrating as part of their ongoing potable reuse program (City of Escondido, 2014). References Adham, S., DeCarolis, J., 2004. Optimization of Various MBR Systems for Water Reclamation Phase III. Final Report, Agreement No. 01-FC-81-0736. United States Department of Interior, Bureau of Reclamation. CDPH, 2013. Alternative Treatment Technology Report for Recycled Water, October 2013. CDPH, 2014. Titles 22 and 17 California Code of Regulations California Department of Public Health s Recycled Water Regulations. Last Updated June 18, 2014. City of Escondido, 2014: Potable Reuse Program Task 1: Feasibility Study prepared by Black & Veatch and Brown and Caldwell. DeCarolis, J., Hirani, Z., Adham, S., 2009 Evaluation of Newly Developed Membrane Bioreactor Systems for Water Reclamation Phase 4 Final Report, Project No. 01-FC- 81-1157. United States Department of Interior, Bureau of Reclamation. Freeman, S., Bates, J., Wallis-Lage, C., Mcevoy., J. (2008), Drought relief in South East, Queensland, Australia, provided by membrane-reclaimed water, Journal AWWA 100:2, international issue, February 2008. Kekre, K., Ang, W.S., Niwa, T., Yamashita, T., Shiota., H., Noguchi., H., 2015 Production of Industrial Grade Water for Reuse from Industrial Used Water using UASB+CMBR Process, presented at WEFTEC 2015, 88th Annual Technical Exhibition & Conference, September 26 30, 2015, McCormick Place, Chicago, Illinois, USA. 15
Acknowledgments The authors of this paper would like to acknowledge the following groups and individuals for their contribution to the success of the project. California Division of Drinking Water, Recycled Water Division, lead by Randy Bernard, for reviewing the demonstration test protocol. Meiden America including: Nobunari Onishi, Bill Pagels, and Noriaki Kanamori for providing and coordinating the installation and startup of the demonstration testing pilot equipment, and providing technical and field support during the testing period. Fluidyne for design and construction of the MBR pilot system. B&V Operations & Data Management Team including: Ahmed Hussein, Osai Robinson and Maddie Ramus. City of Escondido Public Utilities Department, Director of Utilities Christopher McKinney, for sponsoring the Meiden CFM membrane Title 22 Demonstration Testing City of Escondido Water Quality Lab, Laboratory Superintendent Vasana Vipatapat and her staff, for providing analytical support and sample analysis. HARRF Operations Staff including: Jim Larzalere and John Delfante for assisting with the siting of the pilot equipment and providing HARRF operational and water quality data. 16