Overview Increased Increased federal emphasis emphasis on on filter filter performance Virginia s emphasis emphasis on

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2 Overview Increased federal emphasis on filter performance Virginia s emphasis on filter performance Media filter optimization Challenges to good filtration Finding solutions

3 Federal Emphasis on Filter Performance: LT2 Summary Increased filter performance is equated to increased pathogen reduction Source water monitoring for Cryptosporidium determines Bin classification Current classification my change in (periodic testing is required) Bin classification determines additional Cryptosporidium removal requirements

4 LT2 Bin Classification Bin Classification for Filtered Systems Cryptosporidium Concentration (oocysts/l) Bin Classification Additional Cryptosporidium Treatment Required Conventional Filtration Direct Filtration Slow Sand or Diatomaceous Earth Filtration Alternative Filtration <0.075 Bin 1 No Additional Treatment Required No Additional Treatment Required No Additional Treatment Required No Additional Treatment Required to <1.0 Bin 2 1 log 1.5 log 1 log (1) 1.0 to <3.0 Bin 3 2 log 2.5 log 2 log (2) 3.0 Bin log 3 log 2.5 log (3) (1) As determined by the state (or other primacy agency) such that the total removal/inactivation > 4.0-log. (2) As determined by the state (or other primacy agency) such that the total removal/inactivation > 5.0-log. (3) As determined by the state (or other primacy agency) such that the total removal/inactivation > 5.5-log.

5 Federal Emphasis on Filter Performance: LT2 Microbial Toolbox Pathogen removal credits granted for: Source Protection and Management Pre filtration, pre sedimentation, bank filtration Filter performance Additional Filtration (bags, membranes, DE, etc.) Inactivation (UV, Ozone, etc.) Optimization of filter performance can frequently provide additional pathogen removal credit with limited capital cost

6 Increased Federal Emphasis on Filter Performance: LT2 Filter Performance Credit Combined filter performance (0.5 log Crypto removal credit) 0.15 NTU in 95% of filtered water measurements Individual filter performance (0.5 log Crypto removal credit) 0.15 NTU in 95% of filtered water measurements Never exceed 0.3 NTU in any two consecutive 15 minute measurements Optimized Filter performance can yield a 1.0 log Crypto removal credit; Bin 2 systems with optimized filtration can avoid capital expenses for UV, Ozone, etc.

7 Example Individual Filter Data Months Examined February 2009 Filter 1 Filter 2 Filter 3 Filter 4 # 0.15 NTU % 0.15 NTU # 0.15 NTU % 0.15 NTU # 0.15 NTU % 0.15 NTU # 0.15 NTU % 0.15 NTU % % % % July % % % % December 2009 January % % % % % % % % July % % % % July % % % %

8 Example Individual Filter Data Applied filter turbidities averaged 0.42 NTU Filtered water turbidities averaged NTU In three years, there was one month that would have failed the LT2 individual filter requirements to help meet Bin 2 based on 4 hour data There is some forgiveness if failure is very rare, but reliance on this is risky Consistent performance is essential!!!

9 Virginia Optimization Program (VOP) Meeting the EPA standards is not the ultimate goal the goal is to provide pathogen free drinking water The VOP program establishes achievement goals to inspire operators to optimize their plants From 2012 VOP Document: The purpose of VOP is to reduce the risks to public health associated with drinking water beyond the risk reduction inherent by adherence to regulatory standards. VOP is currently focused on enhanced particulate removal at surface water treatment plants with gravity flow, granular media filters.

10 Performance Goals for Optimization Clarification Effluent turbidity < 1.0 NTU 95 % of time when average raw water turbidity for month < 10.0 NTU Effluent turbidity < 2.0 NTU 95 % of time when average raw water turbidity for month > 10.0 NTU Filtration Filtered water turbidity < 0.10 NTU 95 % of time (excluding 15 minutes after backwash) Filtered water turbidity < 0.3 NTU 100% of time Filter Backwash Backwash recovery period < 15 min. (return to < 0.10 NTU) in 95% of backwashes Peak turbidity < 0.3 NTU during backwash recovery period2 in 95 % of backwashes Filtered water turbidity < 0.10 NTU 95% of time a filter is placed into service following a backwash (for 15 min) Minimum Data Monitoring Requirements Raw water 2 hr. intervals (15 minute intervals if continuous monitoring is provided) Clarified water 2 hr. intervals (15 minute intervals if continuous monitoring is provided) Filtered water 15 minute intervals, each filter (in conformance with SWTR) Filtered water turbidity when filter is returned to service following a backwash Peak turbidity during backwash recovery, and period of recovery, each filter, every backwash

11 MEDIA FILTER OPTIMIZATION

12 Measuring Filter Performance Although the design of media filters is highly standardized their performance varies widely. Why? Source: Hancock et al, Journal AWWA, 1996

13 Media Filter Optimization Coagulation Backwashing Procedures

14 Coagulation Straining is not the most important particle removal mechanism in media filtration Adhesion due to particle media collision is key Optimized chemical pretreatment (coagulation) has a greater impact on Cryptosporidium removal than filtration rates, filter media design, and filtration aids (polymer) Optimizing filtration for turbidity removal can provide Cryptosporidium removal in excess of 5 log (treatment technique) Under LT2, 4 log credit can be achieved for conventional treatment with optimized filtration

15 Coagulation Coagulant Selection & Dose ph Alkalinity Temperature Physical Factors Addition Location Mixing Flocculation Transport Coagulation Aids

16 Coagulation Is your current coagulant the best for your water? Is your water chemistry optimized for your coagulant and your water? Is your coagulant addition point and mixing intensity optimized for your coagulant?

17 Filter Backwashing Reduced filter performance during filter ripening can reduce Cryptosporidium removal by up to 1 log Turbidity removal is indicative of Cryptosporidium removal a reason to filter the waste

18 Filter Backwashing: Sub-fluidization Wash More important with evolving clarification processes that produce lower applied filter turbidities. Source: Amburgey et al, Journal AWWA, 2003

19 Filter Backwashing: Backwash Water Chemistry Backwashing with filtered vs. finished water Corrosion Inhibitor, Chlorine, ph control Source: Amburgey et al, Journal AWWA, 2004

20 Filtration Challenges Chemical pretreatment: Coagulant type ph and other water chemistry parameters Coagulant addition point and mixing Backwash Procedures: Adequate backwashing Long ripening period New Media Algae Turbidity Measurement

21 Filtration Challenges: New Media Design media size and depth properly Creates tortuous path Potential for higher filtration rates Require onsite sieve analysis

22 Filtration Challenges: Algae Type of Algae can change over time Algal growth can lead to shorter filter runs Chemical pretreatment can reduce algal growth but different chemicals may not provide the same results Chlorine and chlorine dioxide may cause the algal cell to lyse Sodium permanganate kills the algal cells without destroying them

23 Filtration Challenges: Turbidity Measurement Are the turbidimeters reporting numbers representative of actual turbidities? Equipment maintenance and calibration is a must

24 Filtration Challenges: Turbidity Measurement Don t shear the particles Source: Brumberger et al, Hach Turbidity Science

25 Filtration Challenges: Turbidity Measurement Gas bubbles

26 Solutions Cost effective solutions come down to good operators who know their plant and are devoted to producing the best water possible Vigilance Education and Experience Willingness to Change Improvement Implementation Plans

27 Solutions: Vigilance Be proactive Determine/Understand what is going on Consider ways to make improvements Ask questions

28 Solutions: Education & Experience Understand the issue and know your water and your plant

29 Solutions: Willingness to Change Alternate pre oxidants Alternate coagulants Adjust mixing intensity/addition point Polymer/PACl before filters

30 Solutions: Incremental Changes Make process changes one at a time and allow time to observe the effects Consider new coagulants and/or adjusting water chemistry Adjusting mixers to the best speeds Consider adding coagulant in a pipe instead of rapid mixer Consider adding polymer in the flocculators Consider permanganate addition for algal issues Consider adding polymer just prior to filters Consider changing backwash to include more or less wash and perhaps sub fluidization flows Make sure your instruments are accurate with calibration and that you understand their reporting protocol (averaging, instantaneous)

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