Optimizing Membrane Filtration Using the Revised Self Assessment Guide. Ed Chescattie Planning Section Chief SC Safe Drinking Water Program

Transcription

1 Optimizing Membrane Filtration Using the Revised Self Assessment Guide Ed Chescattie Planning Section Chief SC Safe Drinking Water Program

2 Background Self Assessment Guide (SAG) for Water Treatment Plant Optimization originally published approximately 20 years ago Recently underwent lengthy revisions by a large group Now incorporates significant amount of new information!

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4 What I will discuss Provide introduction to: Chapter 5 of this revised SAG - Membrane Filtration Process Assessment Key Self Assessment Data and Questions

5 Chapter 5 Components 49 Pages 141 to 190

6 Chapter 5 Applicability Developed specifically for surface water filtration plants using membrane filtration as a barrier for pathogen removal, expressed as a log removal value (LRV) Applies to microfiltration and/or ultrafiltration Not aimed at nanofiltration and RO, although some general principles may apply

7 Performance Assessment Data Use your plant-specific data trend graphs to complete the self assessment For membrane plants, turbidity and particle count data is important and provide a means of indirect integrity testing; but

8 Performance Assessment Data A higher degree of sensitivity is needed to identify individual fiber breakage, therefore, additional data is required for membrane self assessment, as compared to a conventional surface water treatment facility

9 Performance Assessment Data Indirect Integrity Testing (NTU/particle counts) Direct Integrity Testing (DIT) AKA Pressure Decay Tests, Membrane Integrity Tests Log Removal Value (LRV) Transmembrane Pressure (TMP) Permeability Integrity Breach Investigations

10 Performance Assessment Data

11 Performance Assessment Data

12 Performance Assessment Questions Self-Assess Contains 76 self-assessment questions specific to membrane treatment facility performance to aid facilities in identifying factors that may be limiting facility performance Discuss the self-assessment questions with your self-assessment team in the order that they appear

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14 Team Approach is Critical! Optimized Performance Goals Operation (Process Control) Capable Plant Administrative Design Maintenance

15 Performance Assessment Questions Indirect Integrity Testing Are indirect integrity control limit optimization goals established at a level that will alert operators to potential problems in a timely manner before a regulatory indirect integrity exceedance occurs? Who reviews indirect integrity data trend graphs and at what frequency?

16 Performance Assessment Questions Direct Integrity Testing How often is the operator present to observe the DIT? How long after completion of the DIT until this data is reviewed? Are DIT control limits established for all three critical parameters LRV, pressure decay rate (psi/min), and pressure decay test resolution limit (DIT start and end pressure in psi)?

17 Performance Assessment Questions DIT Control Limits LRVs Does staff have a general understanding of the normal range for LRV calculation parameters / would they identify an abnormally high or low value within the LRV equation? Will PLC/SCADA allow a membrane unit to return to service if DIT results in an LRV lower than alarm set points? How does the current LRV for each membrane compare to the baseline LRV when that unit was new?

18 Performance Assessment Questions DIT Control Limits Pressure Decay Rates Is pressure decay rate data accurately standardized in psi/min for each DIT? Does manual review of psi/min pressure decay rate data occur? Have SOPs been created that specify operator actions to be taken when pressure decay rates exceed certain values?

19 Performance Assessment Questions DIT Control Limits Pressure Decay Rates For the membrane that currently demonstrates the highest pressure decay rate, graph the psi/min decay rates for each DIT conducted on that particular membrane for the most recent 12 months. Discuss this trend with the self assessment team and summarize observations and concerns.

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21 Performance Assessment Questions Pressure Decay Resolution Limit What is the minimum psi P test resolution limit established for your membranes? What micron resolution limit does this value correlate with? Are all DIT pressures greater than the established minimum Ptest resolution limit?

22 P-test Resolution Limit Importance? 22

23 Performance Assessment Questions Corrective Actions Relationship Between Direct and Indirect Integrity Testing At what specific turbidity and/or particle count level does an indirect integrity exceedance trigger a shutdown of the membrane unit in question? Does the shutdown occur automatically, or must an operator be onsite to manually shutdown? Does and SOP outline investigative actions that should occur following this type of plant shutdown / prior to return to service?

24 Performance Assessment Questions Membrane Repair Triggers for DIT Parameters Has an SOP been created that specifies triggers to remove a membrane from service to conduct repairs? Who is responsible for monitoring these triggers and making the decision to remove the membrane from service to initiate repairs? Are the established membrane repair triggers sensitive enough to identify the need for fiber repair before too many fibers are damaged?

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26 Performance Assessment Questions Integrity Breach Investigations Identification of Specific Modules Contributing to Pressure Decay Do operators feel confident they have the tools and training necessary to accurately identify which specific modules are leaking air during DITs?

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28 Performance Assessment Questions Integrity Breach Investigations Membrane Removal Tools Are operators in need of additional tools or training in order to efficiently remove a membrane module? Are operators able to isolate a specific module from a membrane skid and still keep the remainder of that skid in service?

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30 Performance Assessment Questions Integrity Breach Investigations Identification and Repair of Specific Fibers Contributing to Pressure Decay What constraints apply with regard to maximum amount of time to identify and repair fibers before excessive air begins to cause false positives? Is membrane fiber repair more prevalent on a particular membrane skid? If so, why?

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32 Performance Assessment Questions Evaluating the Impact of Membrane Repair Efforts Are pressure decay rates and LRVs evaluated following membrane repair as a means to verify the success of the repair? Have specific goals been established for these parameters that correlate to a successful membrane repair effort?

33 Most important component of a membrane filtration plant? 33

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35 Performance Assessment Questions Protecting Membranes From Debris What are the primary types of debris present in your source water that may damage your membranes? What is the size of this debris in comparison to your prescreen size? Is an SOP established and consistently implemented relative to a maximum raw water turbidity that would result in plant shutdown to avoid overloading prescreens and/or damaging membranes?

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39 True or False? True or False? Pressure decay loss only occurs from fibers that are broken or are cut? 39

40 Inorganic Particles? Sand particles can cause abrasion and difficulties with pre-screens! 40

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42 Performance Assessment Questions Transmembrane Pressure Are existing TMP alarm set points and testing frequency adequate to prevent membranes from operating at TMP that could result in damage? Does review of TMP data indicate that backwash frequency is adequate to prevent excessive increase in TMP?

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44 Performance Assessment Questions Efforts to Prevent and Reduce Irreversible Fouling: Up until this point, self-assessment review questions have focused on ensuring the production of optimized water quality and protecting the membrane fibers. The ability of membranes to consistently provide adequate quantity of water over a reasonable life span is also important to consider.

45 Performance Assessment Questions Efforts to Prevent and Reduce Irreversible Fouling Permeability: Is accurate permeability data available for real-time operator review and long-term trending? Is a minimum permeability value established and consistently referenced by operators to determine the need to conduct chemical cleaning of membranes? Is an optimal permeability recovery goal used to evaluate the effectiveness of each CIP?

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47 Performance Assessment Questions Efforts to Prevent and Reduce Irreversible Fouling Permeability: How does the current permeability for each membrane compare to the permeability when that unit was first placed into service? Based on the current rate of permeability reduction, what is the anticipated life expectancy of the membranes before irreversible fouling prevents capability to produce adequate water quantity?

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49 Performance Assessment Questions Efforts to Prevent and Reduce Irreversible Fouling Optimizing Clean in Place Procedures: Does your self assessment team consider current CIP procedures optimized to target specific fouling agents of concern for your facility at this time? If necessary, are CIP practices adjusted (via SOPs) seasonally to effectively target variation in the fouling agents present? Is ph recorded and reviewed following CIP as a means to document adequate flushing of membranes has occurred prior to return to service?

50 Trending Permeability can help anticipate and extend life expectancy of membranes

51 Administrative Policies Complete the assessment questions included in Chapter 7, and questions related to Reliability and Life Expectancy Based on lessons learned via this self assessment, is the anticipated life expectancy of your membranes significantly less than originally anticipated? Is adequate funding available to replace membranes in a timely manner? Has your team identified modifications to existing SOPs that could extend the functional life of the membrane filters?

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