EPA/600/R-94/108 August 1994 CHARACTERIZATION OF CLEAN AND FOULED PERFORATED MEMBRANE DIFFUSERS by Lloyd Ewing and Joseph Kitzinger Ewing Engineering Co. Milwaukee, Wisconsin 53209 Cooperative Agreement No. CR812167 Project Officer Richard C. Brenner Water and Hazardous Waste Treatment Research Division Risk Reduction Engineering Laboratory Cincinnati, OH 452 68 RISK REDUCTION ENGINEERING LABORATORY OFFICE OF RESEARCH AND DEVELOPMENT U.S. ENVIRONMENTAL PROTECTION AGENCY CINCINNATI, OHIO 452 68 ------- 4. TITLE AND SUBTITLE Characterization of Clean and Fouled Perforated Membrane Diffusers TECHNICAL REPORT DATA (Please read Instructions on the reverse before comple 1. REPORT NO. EPA/600/R-94/108 2. 3. 6. PERFORMING ORGANIZATION CODE 5. REPORT DATE August 1994 7. AUTHOR(S) 8. PERFORMING ORGANIZATION REPORT NO. Lloyd Ewing and Joseph Kitzinger 9. PERFORMING ORGANIZATION NAME AND ADDRESS 10. PROGRAM ELEMENT NO. Ewing Engineering Co. Milwaukee, Wisconsin 53209 11. CONTRACT/GRANT NO. CR-812167 12. SPONSORING AGENCY NAME AND ADDRESS Risk Reduction Engineering Laboratory—Cincinnati, OH Office of Research and Development U.S. Environmental Protection Agency Cincinnati, OH 45268 13. TYPE OF REPORT AND PERIOD COVERED Project Report 14. SPONSORING AGENCY CODE EPA/600/14 15. SUPPLEMENTARY NOTES Project Officer - Richard Brenner (513) 569-7657 16. ABSTRACT Laboratory analyses were conducted on plasticized PVC perforated membrane tube diffusers after varying periods in service at two different municipal wastewater treatment facilities. One set of diffuers from Cedar Creek, NY, was in service for 26 months. The other set from the Green Bay Metropolitan Sewerage District facility was in service for approximately 47 months. Tests on the membranes included dynamic wet pressure (DWP), flow uniformity, weight, dimensions, tensile modulus of elasticity hardness, and standard oxygen transfer efficiency (SOTE). Results of this brief study indicate a significant increase in DWP and decrease in flow uniformity and SOTE after service. Following membrance cleaning, there was a nonrecoverable reduction in DWP below that of a new membrane; an increase in specific gravity, durometer hardness, and circumferential modulus of elasticity; and a decrease in weight, length, and strain at failure. These findings were in good agreement with other field tests performed with these diffusers. 17. KEY WORDS AND DOCUMENT ANALYSIS DESCRIPTORS activated sludge process, diffusers, aeration, oxygenation b. IDENTIF IE RS/OPEN ENDED TERMS c. COSATl Field/Group fine pore diffusers, plastic membrane dif- fusers, oxygen transfer efficiency, dynamic wet pressure, diffuser foul- ing, diffuser cleaning 18. DISTRIBUTION STATEMENT RELEASE TO PUBLIC 19. SECURITY CLASS (This Report) unclassified 21. NO. OF PAGES 16 20. SECURITY CLASS (This page) unclassified 22. PRICE EPA Form 2220-1 (R«». 4-77) PREVIOUS EDITION IS OBSOLETE ------- DISCLAIMER Development of the information in this report has been funded in part by the U.S. Environmental Protection Agency under Cooperative Agreement No. CR812167 by the American Society of Civil Engineers. The report has been subjected to Agency peer and administrative review and approved for publication as an EPA document. Mention of trade names or commercial products does not constitute endorsement or recommendation for use. ------- FOREWORD Today's rapidly developing and changing technologies and industrial products and practices frequently carry with them the increased generation of materials that, if improperly dealt with, can threaten both public health and the environment. The U.S. Environmental Protection Agency (EPA) is charged by Congress with protecting the Nation's land, air, and water resources. Under a mandate of national environmental laws, the Agency strives to formulate and implement actions leading to a compatible balance between human activities and the ability of natural systems to support and nurture life. These laws direct EPA to perform research to define our environmental problems, measure the impacts, and search for solutions. The Risk Reduction Engineering Laboratory is responsible for planning, implementing, and managing research, development, and demonstration programs to provide an authoritative, defensible engineering basis in support of the policies, programs, and regulations of EPA with respect to drinking water, wastewater, pesticides, toxic substances, solid and hazardous wastes, and Superfund-related activities. This publication is one of the products of that research and provides a vital communication link between the researcher and the user community. As part of these activities, an EPA cooperative agreement was awarded to the American Society of Civil Engineers (ASCE) in 1985 to evaluate the existing data base on fine pore diffused aeration systems in both clean and process waters, conduct field studies at a number of municipal wastewater treatment facilities employing fine pore aeration, and prepare a comprehensive design manual on the subject. This manual, entitled "Design Manual - Fine Pore Aeration Systems," was completed in September 1989 and is available through EPA's Center for Environmental Research Information, Cincinnati, Ohio 45268 (EPA Report No. EPA/625-1- 89/023) . The field studies, carried out as contracts under the ASCE cooperative agreement, were designed to produce reliable information on the performance and operational requirements of fine pore devices under process conditions. These studies resulted in 16 separate contractor reports and provided critical input to the design manual. This report summarizes the results of one of the 16 field studies. E. Timothy Oppelt, Director Risk Reduction Engineering Laboratory ------- PREFACE In 1985, the U.S. Environmental Protection Agency funded Cooperative Research Agreement CR812167 with the American Society of Civil Engineers to evaluate the existing data base on fine pore diffused aeration systems in both clean and process waters, conduct field studies at a number of municipal wastewater treatment facilities employing fine pore diffused aeration, and prepare a comprehensive design manual on the subject. This manual, entitled "Design Manual - Fine Pore Aeration Systems," was published in September 1989 (EPA Report No. EPA/025/1-89/023) and is available from the EPA Center for Environmental Research Information, Cincinnati, OH 45268. As part of this project, contracts were awarded under the cooperative research agreement to conduct 16 field studies to provide technical input to the Design Manual. Each of these field studies resulted in a contractor report. A listing of these reports is presented below. All of the reports are available from the National Technical Information Service, 5285 Port Royal Road, Springfield, VA 22161 (Telephone: 703-487-4650) . 1. "Fine Pore Diffuser System Evaluation for the Green Bay Metropolitan Sewerage District" (EPA/600/R-94/093) by J.J. Marx 2. "Oxygen Transfer Efficiency Surveys at the Jones Island Treatment Plants, 1985-1988" (EPA/600/R-94/094) by R. Warriner 3. "Fine Pore Diffuser Fouling: The Los Angeles Studies" (EPA/600/R-94/095) by M.K. Stenstrom and G. Masutani 4. "Oxygen Transfer Studies at the Madison Metropolitan Sewerage District Facilities" (EPA/600/R-94/096) by W.C. Boyle, A. Craven, W. Danley, and M. Rieth 5. "Long Term Performance Characteristics of Fine Pore Ceramic Diffusers at Monroe, Wisconsin" (EPA/600/R-94/097) by D.T. Redmon, L. Ewing, H. Melcer, and G.V. Ellefson 6. "Case History of Fine Pore Diffuser Retrofit at Ridgewood, New Jersey" (EPA/600/R-94/098) by J.A. Mueller and P.D. Saurer iv ------- 7. "Oxygen Transfer Efficiency Surveys at the South Shore Wastewater Treatment Plant, 1985-1987" (EPA/600/R-94/099) by R. Warriner 8. "Fine Pore Diffuser Case History for Frankenmuth, Michigan" (EPA/600/R-94/100) by T.A. Allbaugh and S.J. Kang 9. "Off-gas Analysis Results and Fine Pore Retrofit Information for Glastonbury, Connecticut" (EPA/600/R-94/101) by R.G. Gilbert and R.C. Sullivan 10. "Off-Gas Analysis Results and Fine Pore Retrofit Case History for Hartford, Connecticut" (EPA/600/R-94/105) by R.G. Gilbert and R.C. Sullivan 11. "The Measurement and Control of Fouling in Fine Pore Diffuser Systems" (EPA/600/R-94/102) by E.L. Barnhart and M. Collins 12. "Fouling of Fine Pore Diffused Aerators: An Interplant Comparison" (EPA/600/R-94/103) by C.R. Baillod and K. Hopkins 13. "Case History Report on Milwaukee Ceramic Plate Aeration Facilities" (EPA/600/R-94/106) by L.A. Ernest 14. "Survey and Evaluation of Porous Polyethylene Media Fine Bubble Tube and Disk Aerators" (EPA/600/R-94/104) by D.H. Houck 15. "Investigations into Biofouling Phenomena in Fine Pore Aeration Devices" (EPA/600/R-94/107) by W. Jansen, J.W. Costerton, and H. Melcer 16. "Characterization of Clean and Fouled Perforated Membrane Diffusers" (EPA/600/R-94/108) by Ewing Engineering Co. v ------- ABSTRACT Laboratory analyses were conducted on plasticized PVC perforated membrane tube diffusers after varying periods in service at two different municipal wastewater treatment facilities. One set of diffusers from Cedar Creek, NY, was in service for 26 months. The other set from the Green Bay Metropolitan Sewerage District facility was in service for approximately 47 months. Tests on the membranes included dynamic wet pressure (DWP), flow uniformity, weight, dimensions, tensile modulus of elasticity, hardness, and standard oxygen transfer efficiency (SOTE). Results of this brief study indicate a significant increase in DWP and decrease in flow uniformity and SOTE after service. Following membrane cleaning, there was a nonrecoverable reduction in DWP below that of a new membrane; an increase in specific gravity, durometer hardness, and circumferential modulus of elasticity; and a decrease in weight, length, and strain at failure. These findings were in good agreement with other field tests performed with these diffusers. This report was submitted in partial fulfillment of Cooperative Agreement No. CR812167 by the American Society of Civil Engineers under subcontract to Ewing Engineering Co. under the partial sponsorship of the U.S. Environmental Protection Agency. The work reported herein was conducted over the period of 1988-1989. vi ------- CONTENTS Foreword iii Preface iv Abstract vi Tables viii Introduction 1 Methods 1 Results 2 Conclusions 3 vii ------- TABLES Number Page 1. Characteristics of Parkson Membrane Tube Diffusers - Cedar Creek, NY (After 26 Months in Service) 4 2. Characteristics of Parkson Membrane Tube Diffusers - Green Bay, WI (After 24 and 41 Months in Service, as Noted) 6 3. Record of DWP and Steady-State SOTE - Green Bay, WI 7 viii ------- INTRODUCTION In the comprehensive study of fine pore diffusion systems by the U.S. Environmental Protection Agency, which resulted in the publication "Design Manual - Fine Pore Aeration Systems" (EPA/625/1-89/023), the subject of changes in characteristics of elastomeric diffusers as a function of time in service was discussed. The results are tabulated in Table 3-6 of that manual. In the final stages of preparation of the design manual, additional data on this topic became available from two sites, one at Green Bay, WI, the other at Cedar Creek., NY. Results of the Cedar Creek investigation by Mueller and Bauer and the Green Bay investigation by Marx were included in the Design Manual as References 37 and 31 of Chapter 3, respectively. Subsequent evaluation of changes in diffuser characteristics at those two sites were conducted and are reported in this paper. METHODS In both studies, new diffusers, representative of those in service, were available. At Cedar Creek, the Parkson Flex-A-Tube diffusers were put in service in June 1986 and were removed and sent to Ewing Engineering Co. for testing in August 1988 after a period of approximately 26 months in service. The Green Bay Parkson Flex-A-Tube diffusers, believed to be of the same materials and manufacture, were installed in approximately January 1986 and were removed and similarly evaluated periodically over a period of approximately 41 months. 1 ------- Characteristics measured included dynamic wet pressure (DWP), flow uniformity, weight and dimensions, tensile modulus of elasticity, hardness, and standard oxygen transfer efficiency (SOTE). These parameters and the methods of testing or measurement are described in the design manual. SOTE, DWP, and flow uniformity were measured on diffusers under as received conditions and after cleaning. Two methods of cleaning were employed, both recommended by Parkson Corp. The most commonly used up to the time of testing described herein consisted of hosing at approximately 50 psi nozzle pressure, scrubbing, and rehosing. The nozzle had an exit orifice of 0.125 in. The other method consisted of scrubbing while simultaneously flushing from the inside with about 5 gpm of clean water. This was performed in addition to the same pre and post hosing. Dimensions, weight, tensile modulus, and hardness were determined on new and cleaned diffusers only. RESULTS The data obtained from the Cedar Creek diffusers are presented in Table 1. Final characterization of the Green Bay diffusers are shown in Table 2. Sequential DWP and SOTE tests on diffusers as received and following cleaning are presented in Table 3. Although the scope of evaluation of this study was somewhat limited, the results obtained are consistent with the 2 ------- investigators' experience with plasticized membrane diffusers at other sites that were not part of this design manual project. CONCLUSIONS 1. With few exceptions, the characteristics of both the unused (new) diffusers and diffusers after varying periods of service appear to be in reasonably good agreement with those that have been obtained in other field tests of Parkson PVC membrane diffusers. 2. Service exposure apparently produces a measurable increase in "as received" DWP, as well as in "after cleaning" specific gravity and durometer hardness. The after cleaning DWP indicates a non-recoverable reduction from "new" DWP. These changes are accompanied by a dramatic increase in circumferential tensile modulus of elasticity. 3. Service exposure in these tests resulted in a measurable decrease in "as received" air flow uniformity, SOTE, and "after cleaning" weight, length, and strain at tensile rupture. 4. The two methods of cleaning investigated appeared to provide similar results. 5. The detrimental effects of service on diffuser characteristics appeared to occur at a declining rate over the period of observation. 6. These detrimental effects did not appear to be progressive beyond that period of early change. 7. Cleaning appears to have a minor beneficial effect on the restoration of SOTE to near original values. 3 ------- TABLE 1. CHARACTERIZATION OF PARKSON MEMBRANE TUBE DIFFUSERS - CEDAR CREEK, NY (AFTER 26 MONTHS IN SERVICE) Date Tested Diffuser No. Condition1 Weight (g) PWP (in. w.g.) Thickness (in.) 0.75 cfm 1.00 cfm 2.0 cfm 3.00 cfm Flow Uniformity (six)2 8-24-88 1 Fouled as Received 8-25-88 1 After LP HBH 111 0.0277 5.00 3.30 5.60 3.45 8.05 3.85 12.95 4.30 0.277 0.182 8-24-88 2 Fouled as Received 8-25-88 2 After FHB 4.55 3.55 4.90 3.75 7.50 4.40 10.70 5.10 0.418 0.242 8-24-88 3 Fouled as Received 8-25-88 3 After LP HBH 5.40 4.45 6.20 4.55 8.25 5.25 11.55 5.85 0.318 0.839 8-24-88 4 Fouled as Received 8-25-88 4 After FBH 112 0.0280 6.65 5.20 7.45 5.50 11.25 6.45 15.95 7.50 0.268 0.151 8-24-88 5 Fouled as Receoved 8-25-88 5 After LP HBH 101 0.0270 6.35 4.10 7.10 4.20 10.90 4.60 15.75 4.90 0.339 0.517 8-24-88 6 Fouled as Received 8-25-88 6 After FBH 8-29-88 7 New 9-16-88 7 New 10-20-88 7 New 107 118 0.0282 0.0278 5.55 4.30 5.25 5.95 4.40 5.45 8.05 4.90 6.00 10.65 5.30 6.50 0.492 0.176 0.149 'LP - Low pressure 'HBH - Hose, brush, and rehose 'FBH - Flush, brush, and hose 2Sample standard deviation/average of individual sample points 3Shore A durometer, average of five points duplicates ------- SOTE SOTE Date Diffuser at at Tested No. 1 cfm 3 cfm 8-24-88 1 8-25-88 1 8-24-88 2 8-25-88 2 8-24-88 3 8-25-88 3 8-24-88 4 8-25-88 4 8-24-88 5 8-25-88 5 8-24-88 6 8-25-88 6 8-29-88 7 9-16-88 7 10-20-88 7 0.1342 0.1290 0.1275 0.1378 0.1301 0.1431 0.1406 0.1426 0.1802 0.1602 0.1363 0.1632 0.1476 0.1424 0.1318 0.1499 0.1363 0.1307 0.15594 0.1634 0.14264 0.1603 0.1688 0.1803 0.1781 0.1852 TABLE 1 (continued) Tensile Diameter Diameter Specific Modulus Estimated at 5 in. w.g Gravity Hardness2 (psi) (in.) (in.) 71.75 1287 2.343 2.404 75.25 1405 2.283 2.354 1.247 77.20 5967 2.154 2.204 77.12 4433 2.143 2.186 1.205 62.75 653 2.319 2.425 ------- TABLE 2. CHARACTERIZATION OF PARKSON MEMBRANE TUBE DIFFUSERS - GREEN BAY, WI (AFTER 24 AND 41 MONTHS IN SERVICE, AS NOTED) DWP fin. w.s). CWOTEused/CWOTEnew3 Flow Tube Tensile Diffujer No. Basin' Condition2 1.0 cfm 2.0 cfm 3.0 cfm 1.0 cfm 3.0 cfm exp.4 Uniformity (tlx)5 Weight (8) Length (in.) Diameter (in.) Thickness (in.) Modulus Hardness6 (psi) A-l A-l C As Found After HBH 8.1 3.7 13.2 4.1 19.2 4.7 0.68 0.75 0.77 0.91 +0.03 -0.10 0.32 0.37 A-2 A-2 C As Found After FB 9.8 3.3 14.6 3.7 20.1 4.3 0.74 0.51 0.33 114 25.3 2.34 0.0290 1,090 68.0 A-3 C As Found 6.1 10.8 17.4 0.25 > > R As Found After HBH 10.2 3.6 17.0 4.4 24.3 5.1 0.63 0.73 0.73 0.86 +0.05 +0.07 0.52 0.36 114 25.3 2.39 0.0290 1,350 65.0 A-5 R As Found 9.4 15.7 22.3 0.37 A-6 A-6 R As Found After FB 9.9 3.8 17.5 4.7 24.5 5.8 0.71 0.41 0.34 C Inlet A-7 A-7 A-8 A-8 A-9 A-9 A-10 C New A* Found After HBH C As Found Middle After HBH C As Found Outlet After HBH 9.5 4.0 9.9 3.9 8.1 3.4 7.25 16.6 5.5 19.0 5.6 16.5 4.2 9.70 0.87 0.79 0.81 1.00 1.00 -0.08 0.47 0.29 0.23 0.29 0.24 105 104 104 119 24.7 24.7 24.7 26.2 2.24 *C - Contact basin *R - Reaeration basin 2HBH = hose, brush, and rehosc 2FB > flush @ 3-5 gpm of clean water while brushing 'Ratio of small tank clean water oxygen transfer efficiencies, CWOTEnew ® 1.0 cfm = 0.180 CWOTEnew® 3.0 cfm = 0.165 ^Exponent: CWOTE = Constant x (air flow rate) exp. ^Sample standard deviation/average of individiual sample points 'Shore A durometer, average of five points 0.0310 0.0280 0.0280 0.0302 1,290 78.0 1,020 81.0 1,370 81.0 630 63.0 (mo) ~24 24 24 24 24 24 24 24 24 24 41 41 41 41 41 41 0 ------- TABLE 3. RECORD OF DWP AND STEADY-STATE SOTE - GREEN BAY, WI Date Tested Condition Time In Service (mo) Basin DWP (in. w.g.) DWP (in.w.g.) SOTE Type @1.0 elm @ 3.0 cfrn @ 2.0 cfm 11-86 11-86 As Received After HBH 10 10 Contact Contact Grid Grid 6.5 4.3 9.9 5.4 0.115 0.123 7-87 7-87 As Received After HBH 19 19 Contact Contact Grid Grid 6.3 2.9 12.5 4.9 0.125 0.142 12-87 12-87 5-89 5-89 As Received After HBH As Received After HBH Original 24 24 41 41 Contact Contact Contact- Inlet Contact- Inlet Pilot Pilot Grid Grid 8.0 3.5 9.2 3.5 7.6 18.9 4.5 17.2 5.1 10.6 0.127 0.135 0.141 0.173 1 HBH - Hose, brush, and rehose ------- |