Conditional Backwash Control with In-Filter Media And Turbidity Monitoring - An Optimization Tool for Gravity Filters.

Transcription

1 American Water Works Association New York Section Saraotoga Springs, NY April 2016 Conditional Backwash Control with In-Filter Media And Turbidity Monitoring - An Optimization Tool for Gravity Filters Kary Steadman

2 In-Filter Monitoring Of Media Expansion and Turbidity Filters are Backwashed by reversing the direction of flow and discharging into wash troughs. Proper expansion fluidizes the media to allow impurities to escape. Optimal Media Expansion is critical to effective filter cleaning and health. FILTERING BACKWASHING Smart, Flexible, Friendly!

3 Organ Pipes or Pan Pipes Smart, Flexible, Friendly!

4 What Do They Have In Common? Manual Measurement Method, Not Tied Into Control System Can be Subjective Most Importantly: It s a Snapshot and does not give you the entire backwash profile

5 Level & Turbidity Sensor Smart, Flexible, Friendly!

6 Monitor Bed Expansion AND Turbidity In The Filter ~Conditional Backwash Control~ Optimum Expansion PLUS Optimum Duration Equals Optimized Backwash! Smart, Flexible, Friendly!

7 Echo Profile of Media at Rest Smart, Flexible, Friendly!

8

9 Typical Installation Media Filters Drinking Water and Wastewater Mono or Dual Media Surface Wash & Air Scouring Systems OK Effective in All Media Types

10 In-Filter Monitoring Of Media Expansion and Turbidity For Conditional Backwash Control Smart, Flexible, Friendly!

11 Percent Bed Expansion Net Expansion Resting Media Level Max Expansion

12 How Much Expansion is Best? A proper backwash rate should expand the filter 20-25%, but expansion can be as high as 50% ~USEPA Technical Guidance Manual 2004

13 How Much Expansion? Appropriate Fluidization Backwash Rates (Reference: AWWA B100-01) Water Temperature Fluidization Backwash Rate, gpm/ft2 o C o F Sand Anthracite Coal (d60% size of 0.7 mm) (d60% size of 1.5 mm) Note: These fluidization backwash rates are guidelines for media with a grain size of d60% (effective size x uniformity coefficient). The specific gravities are: sand = 2.65 and anthracite coal = The rates should be adjusted as necessary for other filter materials. An appropriate fluidization backwash rate is one that fluidizes the bed with adequate expansion and attains sufficient velocities to bring fines to the surface. Fluidization is the upward flow of a fluid through a granular bed at sufficient velocity to suspend the grains in the fluid and depends on filter media properties, backwash temperature, and backwash water flow rates

14 Turbidity Endpoint (or, When Does It All Stop!?!?) Susumu Kawamura-In his book Integrated Design and Operation of Water Treatment Facilities- Notes that typically Plant Operators want a turbidity of 5 to 10 NTU in waste wash water Keeping 5-10 NTU can reduce the ripening time of the filter reducing the amount of water to waste Plant Operators can experiment with different NTU s to determine the optimal ripening time for their specific filters

15 Example 1 Las Vegas Water Reclamation Facility 8 Filters with approximately 35.5 inches of expandable media (anthracite + sand) Each filter gets backwashed about 40.6 times per year, for a total of 325 backwashes per year Assumed cost to process water is $10.70 per 10,000 gallons

16 Example 1 Las Vegas WRF Existing Process Smart, Flexible, Friendly!

17 Example 1 Las Vegas WRF-Existing Process Backwash process is 13 minutes of high flow at 10,000 GPM Objective is to have turbidity at less then 10 NTU before the end of high flow Existing process yields expansion of 3.5 inches or 10% Existing process takes 12 minutes and 30 seconds of high flow to achieve 10 NTU 12.5 min. X 10,000 GPM = 125,000 gallons 125, 000 gallons X $10.70/10,000 gallons = $ $ X 324 Backwashes per year = $43,335.00

18 Example 1 Las Vegas WRF New Process Smart, Flexible, Friendly!

19 Example 1 Las Vegas WRF-New Process Increase high flow from 10,000 GPM to 20,000 GPM Reduce duration of high flow based on turbidity of 10 NTU or less High flow of 20,000 GPM increases media expansion to 8.5 inches or 24% New process takes 5 minutes and 20 seconds of high flow to achieve 10 NTU 5.33 min. X 20,000 GPM = 106,600 gallons 106,600 gallons X $10.70/10,000 gallons = $ $ X 324 Backwashes per year = $36, Yearly savings $43, $36, = $6,379.56

20 Example 2 Providence WTP Smart, Flexible, Friendly!

21 Example 2 Providence WTP Backwash Sequence

22 Example 2 Providence WTP Filter recently rebuilt Combined low flow and high flow total of 221,096 gallons per backwash Assumed cost of water $5.25 per 10,000 gallons 221,096 x $5.25/10,000 = $ per BW 18 Filters BW 121 times each per year = $252,800 per year Reducing high flow by 2 minutes would result in 151,096 g x $5.25/10,000 = $ per BW 18 x 121 x $79.33 = $172,780 per year Total savings of $80,020 per year

23 Implementation Options Smart, Flexible, Friendly!

24 Smart Sensors Provide Additional Benefits Digital Technology Field Networks of up to 16 sensors Plug-n-Play Components Remote Start-up and Monitoring Smart, Flexible, Friendly!

25 Field Networks Stand-Alone Systems Wired Field Networks Wireless Field Networks Smart, Flexible, Friendly!

26

27 Smart, Flexible, Friendly!

28 Smart, Flexible, Friendly!

29 Remote Monitoring via Cell Modem Cellular Modem in the Controller All Settings Available for Remote Startup 24/7 Secure Access to All Sensors in the Network for Monitoring & Support Smart, Flexible, Friendly!

30 To Summarize: Achieve Proper Expansion Every Time Adjust Flow Rates Based on Water Temperature Control Length of Backwash Based on Real Time Turbidity Measurement, Avoiding Wasting Water, Chemicals and Energy Ensure You Are Not Losing Media Prevent Mud Balls and Other Problems Conditional Backwash Control Smart, Flexible, Friendly!

31 Interface Level Analyzers Thank You! Kary Steadman Smart, Flexible, Friendly!