APPLICATION OF FLAT SHEET CERAMIC MEMBRANE TECHNOLOGY FOR WATER REUSE. Abstract. Introduction

Transcription

1 APPLICATION OF FLAT SHEET CERAMIC MEMBRANE TECHNOLOGY FOR WATER REUSE James F. DeCarolis, P.E., Black & Veatch, 300 Rancheros Drive, Suite 250, San Marcos, CA, 92069, Ph: 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 Meidensha Corporation (Tokyo, Japan) contracted Black & Veatch to perform third party demonstration testing of their ceramic flat sheet membrane CFM membrane to demonstrate its ability to meet the California Division of Drinking Water (DDW) Recycled Water Criteria per California Code of Regulations Title 22. The City of Escondido (City), California sponsored the CFM technology by providing the test site and required utilities. Testing of the CFM membrane was completed over an 8 week steady state operating period which began in September During this time the CFM was configured into an MBR pilot system, and operated on primary effluent from the City s municipal wastewater treatment plant (i.e. Hale Avenue Resource Recovery Facility). This paper builds on initial results presented previously (DeCarolis et al., 2015). 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., 2007). 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, and 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 recently conducted demonstration testing of the CFM MBR treating municipal wastewater. The primary goal of the testing was to demonstrate the CFM membrane meets 1

2 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; 0.5 NTU 100% of the time (CDPH 2014). The City of Escondido (City), California sponsored the demonstration testing of CFM technology. Testing of the CFM membrane was done using a MBR pilot system, which operated on primary effluent from the City s municipal wastewater treatment plant (i.e. Hale Avenue Resource Recovery Facility-HARRF). This paper presents operational and water quality performance data from the 8-week demonstration testing of the Meiden Ceramic MBR, which began steady-state operation in September The paper is organized as follows: Introduction; Demonstration Study Objectives; Materials & Methods; MBR Performance Monitoring Results; Summary & Conclusions ; Acknowledgments. Demonstration Study Objectives The main objective of the Meiden MBR demonstration study was to evaluate the ability of the Meiden CFM membrane to comply with filtration performance requirements per California s Title 22, Section The overall study objectives were 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; 2

3 Assess effectiveness of manufacturer recommended membrane cleaning protocols. Pilot Testing Site Materials and Methods The pilot testing site for this study was the 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: dissolved air flotation (DAF) thickeners, anaerobic digesters, solids dewatering centrifuges, and an energy recovery system. Several chemicals are dosed throughout the HARRF treatment process as summarized in Table 1. The plant periodically practices chemically enhanced primary treatment (CEPT), which utilizes coagulant and polymer addition. During the pilot study, the use of CEPT was tracked to evaluate the impact (if any) on the MBR pilot performance. The pilot system was located on a concrete test pad located at HARRF. The site provided 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 was operated with primary effluent. Primary effluent quality from samples collected between as provided by the City is presented in Table 2. Table 1 HARRF Chemical Dosing Locations HARRF DOSING LOCATION CHEMICAL PURPOSE TYPICAL DOSE, MG/L Grit Chamber Inlet Ferric Sulfate Chemically Enhanced Primary Treatment 0-25 as Fe2(S04)3*9H2O Primary Clarifiers Polydyne, Clarifloc WE 1024 Chemically Enhanced Primary Treatment Tertiary Filter Influent Polydyne, Clarifloc WE 850 Improve Filter Performance Tertiary Filter Influent Polydyne, Clarifloc WE 888 Improve Filter Performance 1-2 3

4 Table 2 HARRF Primary Effluent Quality PARAMETER UNITS AVERAGE MIN MAX Alkalinity mg/l as CaCO Carbonaceous biological oxygen demand (CBOD) Total Suspended Solids (TSS) Volatile suspended solids (VSS) mg/l mg/l mg/l Total dissolved solids (TDS) mg/l TKN mg/l -N Ammonia mg/l-n 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 served as the aerobic tank. A basic flow schematic of the Meiden/Fluidyne MBR pilot system is provided in Figure 1. 4

5 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. Photographs of the unit being installed into the membrane chamber of the MBR tank is provided in Figure 2. 5

6 Table 3 Specifications of the Meiden Ceramic Flat Sheet Membrane Unit PARAMETER UNITS VALUE Commercial Designation CH TM100-U2DJ Unit Configuration Level stack Number of Membranes # 400 total installed elements (300 elements were connected to the filtrate header for pilot testing). Membrane Type Flat-Sheet Approximate size of element (LXWXH) mm 261X12X1046 Nominal Pore Size (micron) micron 0.1 Membrane Material Alumina Active Membrane Area per element ft Maximum Backwash Pressure pounds per square inch (psi) 8.7 Maximum Trans-membrane Pressure psi 8.7 Maximum Temperature C 60 Operating / Cleaning ph Standard Units 4-10 /

7 Figure 2 Photograph of the Meiden Ceramic Membrane Unit during Installation Pilot Plant Operating Conditions 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

8 Table 4 Target Steady State Operating Conditions of the Meiden MBR Pilot System PARAMETER UNITS VALUE Total HRT hours 14.4 Aerobic + Anoxic HRT hours = 8.08 SRT days MBR TSS mg/l 8,000 10,000 Instantaneous Filtrate flow gallons per minute (gpm) 27.4 Instantaneous Flux gfd 24.5 Net Flux gfd 19.6 Filtration Cycle min 9 Backwash duration sec 30 Backwash flow gpm 54.8 Operational & Water Quality Performance Monitoring Approach The overall approach to meet the demonstration study objectives was 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 was conducted. Examples of various operational parameters 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 was 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 were 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 was 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 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 were measured by off-site laboratories in accordance to methods listed in the Standard Methods for the Examination of Water and Wastewater (SM), United States 8

9 Environmental Protection Agency (EPA) or the American Public Health Association (APHA). Specific laboratories used throughout the project include the City of Escondido Water Quality Laboratory, Eurofins-Calscience, and Biovir Laboratories. Membrane cleaning was performed per manufacturer recommended cleaning protocols after observing a significant increase of TMP (or corresponding decrease in temperature corrected specific flux). The pilot system was 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 chlorine cleaning was performed with a high ph solution of sodium hypochlorite at a target concentration of 0.1% w/w. Acid cleanings were conducted using a low ph solution of citric acid at target concentration of 0.5% w/w citric acid. MBR Performance Monitoring Results Membrane Operational Performance Monitoring The membrane performance data from the Meiden CFM MBR monitored over the reporting period of 9/28/15 to 11/23/15 is provided in Figure 3. The upper graph shows the average TMP and temperature (measured in the anoxic chamber). The lower graph shows the temperature corrected flux and temperature corrected specific flux. The graphs also indicate when maintenance cleanings (MC s) were conducted and the type of chemicals used (i.e. chlorine only or chlorine followed by citric acid). During the majority of this time period, the system was operated with a target instantaneous flux of 24.5 gfd. Backwashing was performed every 9 minutes for duration of 30 seconds. The backwash flow rate was approximately 2 times the filtration flow rate. Based on the filtration and backwash conditions the target net flux during this time period was 19.6 gfd. The TMP trends observed over the demonstration period indicate fouling occurred between chlorine only MC s. The results also showed the MC conducted with chlorine followed by citric acid was very effective at reducing the TMP to initial values. This data suggests membrane fouling was due to build of inorganic foulants on the membranes. It is speculated the CEPT chemicals present in the HARRF primary effluent including ferric sulfate and polymer may have been the source of inorganic foulants. 9

10 Figure 3 Membrane Performance of the Meiden CFM MBR 10

11 Water Quality Performance Monitoring Water quality performance results of the Meiden MBR system collected over the reporting period including particulate (turbidity), organic (BOD/COD), total inorganic nitrogen (ammonia, +nitrate+ nitrite) and microbial (total coliform, fecal coliform, and coliphage) constituents are provided in Figures 4, 5, 6, and 7 respectively. Figure 4 shows the Meiden CFM MBR consistently met 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 MCs, 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 24 mg/l. The average TOC concentration (not shown) measured in the influent wastewater and MBR filtrate was 101 mg/l and 7.6 mg/l, respectively. These results indicate the Meiden MBR achieved a high degree of organic removal. Figure 6 shows the total inorganic nitrogen (TIN) results measured in the influent wastewater and Meiden CFM MBR filtrate. The results show the TIN of the influent ranged from mg/l-n. MBR filtrate TIN range from 8-23 mg/l-n. The ammonia and nitrite values (not shown) measured in the MBR filtrate were all below the method reporting limit (MRL) indicating the system was fully nitrifying. The nitrate values (not shown) measured in the MBR filtrate ranged from mg/l-n indicating partial denitrification was achieved. This data indicates that denitrification could have been inhibited during the testing. Possible causes include carry over of dissolved oxygen (DO) present in the recycle streams to the anoxic chamber and the amount of available readily biodegradable COD present in the influent. Figure 7 shows the results of total coliform (upper graph) and fecal coliform (middle graph) analyses conducted on the Meiden CFM MBR system over the reporting period. Results showed the total and fecal 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. Figure 7 (lower graph) shows the total coliphage (Somatic + Male Specific) measured in the feed wastewater and MBR filtrate. Total coliphage concentration in the feed wastewater ranged from 4.3 x 10 6 to 7.3 x 10 6 PFU/100 ml with an average concentration of 6.0 x 106 PFU/100ml. MBR Filtrate concentration of total coliphage ranged from 35 to 360 PFU/ml. Based on the average feed wastewater and MBR filtrate concentrations, the system achieved 3.5 log removal of total coliphage. 11

12 Figure 4 Turbidity Removal by the Meiden CFM MBR 12

13 Figure 5 BOD/COD Removal by the Meiden CFM MBR 13

14 Figure 6 Inorganic Nitrogen Removal by the Meiden CFM MBR 14

15 Figure 7 Coliform and Coliphage Removal by the Meiden CFM MBR 15

16 Summary & Conclusions An 8-week demonstration test of the Meiden CFM MBR was conducted at the City of Escondido s Hale Avenue Resource Recovery Facility (HARRF) located in Escondido, California. The primary goal of the testing was 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. The following provides a summary of the main results: Continuous online turbidity monitoring of the Meiden CFM pilot system showed the CFM filtrate turbidity to meet the Title 22 Filtration requirements: NTU 95% of the time within 24 hours; NTU 100% of the time (CDPH, 2014). During the testing period, the Meiden CFM MBR operated at a target instantaneous flux of 24.5 gfd. The CFM was backwashed every 9 minutes for 30 seconds resulting in a net flux of 19.6 gfd. The target instantaneous flux was reduced for approximately the last three weeks of testing due to membrane fouling. Maintenance cleans were conducted at intervals ranging from of approximately every 3 to 8 days. In general, maintenance cleaning using sodium hypochlorite only throughout the test period was effective at restoring membrane productivity; however, toward the end of the test period significant increase in TMP required cleaning with citric acid. The effectiveness of the acid cleaning suggests inorganic foulants built up over the test period. The Meiden CFM MBR pilot system achieved a high degree of organic removal with average removal of various constituents as follows BOD5 removal > 99 %; TOC = 92%; and COD = 93%. The Meiden CFM MBR pilot system consistently achieved complete nitrification with average ammonia in the feed wastewater of 52 mg/l N and MBR filtrate < MRL (0.63 mg/l-n). The Meiden CFM MBR pilot system achieved partial denitrification with average MBR filtrate nitrate concentration of 15.2 mg/l N. It is suspected denitrification was inhibited by carry over of dissolved oxygen (DO) present in the recycle streams to the anoxic chamber and the amount of available readily biodegradable COD present in the influent. The Meiden CFM MBR pilot system achieved greater than 6 LRV of total and fecal coliform with all MBR filtrate samples ND. Total coliphage removal of 3.5 LRV with average MBR filtrate concentration of 185 PFU/100 ml. 16

17 Results of the testing were summarized in a Final Report (Black &Veatch, 2016) and submitted to DDW for review in March Subsequent to reviewing the report and findings, the DDW provided a letter in June 2016 granting the conditional acceptable of the CFM as an alternative treatment technology for recycled water filtration applications. Additional information on technologies that have been recognized by DDW as being conditionally acceptable for compliance with Title 22 can be provided elsewhere (DDW, 2014). 17

18 References Adham, S., and DeCarolis, J., Optimization of Various MBR Systems for Water Reclamation Phase III. Final Report, Agreement No. 01-FC United States Department of Interior, Bureau of Reclamation, May Black & Veatch, Assessing the Ability of the Meiden Ceramic Flat Sheet Membrane (CFM) to Meet Existing Water Reuse Criteria MBR Demonstration Study Final Report, March 2016, prepared for Meidensha Corporation. CDPH, Title 22 and Title 17 California Code of Regulations California Department of Public Health s Recycled Water Regulations. Last Updated June 18, DDW, Alternative Treatment Technology Report for Recycled Water, September DeCarolis, J., Freeman, S., Hunter, G., Sabherwal, B., Sathyamoorthy, S., and Koh, SH., Evaluation of Ceramic MBR Technology for Water Reuse., presented at the Membrane Technology Conference & Exposition, March 2-6, 2015, Rosen Shingle Creek, Orlando, FL. DeCarolis, J., Hirani, Z., and Adham, S., Evaluation of Newly Developed Membrane Bioreactor Systems for Water Reclamation Phase 4 Final Report, Project No. 01-FC United States Department of Interior, Bureau of Reclamation, November Freeman, S., Bates, J., Wallis-Lage, C., and McEvoy., J., Drought relief in South East, Queensland, Australia, provided by membrane-reclaimed water, Journal AWWA 100:2, International Issue, February Kekre, K., Ang, W.S., Niwa, T., Yamashita, T., Shiota., H., and Noguchi., H., 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. 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. 18

19 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. 19