WTR_M_PM_01.40_Jackson - NC AWWA-WEA

Spring Conference:
Spring into Operation
April 6 - 8, 2014
Wilmington Convention Center
Eliminating the Ripening Spike and Saving
Water – Optimizing Filter Backwash at a 30
MGD WTP
Jay Jackson, P.E.
Acknowledgements
NC AWWA WEA 2011 §  Barry Parsons and Staff, City of Greensboro, NC
§  Colleen Geohagan and Gary Iversen, Hazen and Sawyer
§  Dr. James Amburgey, UNC- Charlotte
Reasons for the Project
1 - Continue to improve filter water quality @ Townsend WTP
Reclassification of Greensboro’s water supply into Bin 2 of LT2 is a
possibility – NC DENR promotes Enhanced Filter Performance as first
method to meet Bin 2 requirements for existing Surface WTPs
Enhanced Filter Performance – Toolbox Item Number 7 in the LT2Guidance
Manual
NC AWWA WEA 2011 2 - Observations that filter media may not be adequately
expanded/cleaned all of the time, and:
Filter Runs are shorter than desired, especially in the summer
NC AWWA WEA 2011 Composite Sample of Existing Media – Matched Original Specification
Evaluated Effectiveness of Backwash
Test Conducted on March 7, 2013
§  Installed Temporary Strap-On Ultrasonic
meter to check reported flow rate
§  Strap-on Meter and Townsend Flow Meter
agreed (10%)
§  Measured Backwash Flow Rate =
18 MGD (20 MGD on SCADA)
§  Raw Water Temp = 9.5 o C
§  Calculated Backwash rate at this
Temperature = 16.4 MGD for
approximately 30% Bed Expansion
NC AWWA WEA 2011 §  Measured Bed Expansion using City’s
Entech Trial Instrument = 42%
§  Turbidity measured by Entech and also
checked by Lab
Backwash Turbidity Profile – Filter 7 (March 7, 2013)
Turbidity Removal and Backwash Water Usage vs. Time 100 90% of Turbidity Removal at 8 min with roughly 35% of water use 95% of Turbidity Removal at 9.5 min with less than 50% of backwash water use 90 80 Percent (%) 70 60 50 40 Cumm. % Total Turbidity Removed 30 Cumm. % Backwash Water Used (SCADA) 20 10 Cumm. % Backwash Water Used (UltraSon) 0 NC AWWA WEA 2011 0 2 4 6 8 10 12 14 Time (minutes) 16 18 20 22 NC AWWA WEA 2011 29 12:04:50 12:05:30 12:06:10 12:06:50 12:07:30 12:08:10 12:08:50 12:09:30 12:10:10 12:10:50 12:11:30 12:12:10 12:12:50 12:13:30 12:14:10 12:14:50 12:15:30 12:16:10 12:16:50 12:17:30 12:18:10 12:18:50 12:19:30 12:20:10 12:20:50 12:21:30 12:22:10 12:22:50 12:23:30 12:24:10 12:24:50 12:25:30 12:26:10 12:26:50 12:27:30 12:28:10 12:28:50 12:29:30 12:30:10 Expanded Bed Height -­‐ Inches 43 41 39 30 37 25 35 20 33 15 10 31 5 Bed Level Expansion (inches) % Expansion -­‐ 18in anthracite, 8in sand 0 % Expansion Entech Expansion Profile – Filter 7 (March 7, 2013)
Greensboro Townsend WTP Entech Design Demo -­‐ Filter 7 50 45 40 35 Backwash Recommendations
§  Adjust backwash duration in
cool water conditions to
conserve water
§  Adjust max backwash flow rate
in cool water conditions to
conserve water
NC AWWA WEA 2011 §  50% Savings in water use based on historical data (Oct –
March), could save 104,000 gals
per wash or approximately
337,000 gals per day
How effective is current backwash during warm water/
summer conditions ?
Pilot Filter Columns
3 Pilot Filter Columns
1 ) Existing Media
2 ) Larger ES: Sand and
Anthracite
3 ) Existing Sand and
Anthracite + Ceramic Media
Cap; then New Sand and
Anthracite + Ceramic Media
Cap
758’ ~ 5’-­‐6’ available head NC AWWA WEA 2011 751.52’ Clearwell water level 18” Anthracite 8” Fine Sand 4” Coarse Sand Ceramic Media
§  Expanded clay aggregate:
§  Larger size but lower specific gravity than anthracite;
§  Requires lower backwash rates;
§  Proper selection to ensure it doesn’t sink into anthracite
§  Used in Europe and the UK in drinking water
applications; USA manufacturer pursuing NSF
approval
NC AWWA WEA 2011 §  Results from a previous study for Gwinnett County,
GA (Amburgey) indicated that a cap of ceramic media
would reduce rate of headloss and increase run times
§  Ceramic media in Pilot Filter 3 is US product – NSF 61
certification soon
Pilot Filters -Media Selection
Filter 1*
Sand
Depth
(in)
d10
(mm)
8
Filter 2
Filter 3
Initial*
Anthracite
UC
Depth
(in)
d10
(mm)
0.54
1.63
18
12
0.55
1.4
8
0.54
Filter 3 Final
12
Filter 4*
Ceramic Media
UC
Depth
(in)
d10
(mm)
UC
L/d
0.92
1.48
N/A
N/A
N/A
873
18
1.2
1.4
N/A
N/A
N/A
935
1.63
18
0.92
1.48
6
1.6
1.5
969
0.55
1.4
18
1.2
1.4
6
1.6
1.5
1030
8
0.54
1.63
18
0.92
1.48
N/A
N/A
N/A
873
Filter 5
Filter 6
Initial
12
0.55
1.4
18
1.2
1.4
N/A
N/A
N/A
935
12
0.45
1.5
18
1.1
1.4
6
1.6
1.5
1093
Filter 6 Final
12
0.55
1.4
18
1.2
1.4
6
1.6
1.5
1030
NC AWWA WEA 2011 * Pilot Filters contained media from the existing WTP filters
Pilot Filter Standard Backwash Sequence
NC AWWA WEA 2011 1) Air Scour 2 minutes
2) Air + Low Rate (approx 1.5 minutes)
3) High rate for 10 minutes (dependent on temp
and media)
4) Reduce from high to low rate
5) Filter -to- Waste @ 4 gpm/sf for 15 min
Pilot Filter Test Periods Spring and Summer 2013
Observations:
•  Existing fine sand (sampled twice) mixed w/
coarse sand -affects fluidization
•  Water Temperature = 12 – 29o deg C
•  Settled water pH = 5.5 – 5.9
•  Settled water turbidity = 0.3 – 1.0 ntu
•  Pilot filters tested at 2 to 3.8 gpm/sf
(15.7 to 30 MGD full scale)
•  Full Scale filter rate 1.8 to 2.5 gpm/sf
•  Pilot filter rate > full scale filter rate
NC AWWA WEA 2011 (because plant flow rate was 13-20 MGD instead of
30 MGD)
Pilot Filters – Run Time to 5 feet headloss
(Spring 2013)
Townsend Filter Pilot Headloss Curves 7 6 3.8 gpm/sf Run Times: Filter 1 = 52 hrs Filter 2 = 51 hrs Filter 3 = 73 hrs 2 gpm/sf Run Times: Filter 1 = 96 hrs Filter 2 = 96 hrs Filter 3 = 96 hrs Delta Pressure (J) 5 4 Filter 1 3 2 1 NC AWWA WEA 2011 0 Filter 2 Filter 3 Pilot Filters – Run Time to 5 feet headloss
(Summer 2013)
8 7 Delta Pressure (J) 6 Q = 3.8 gpm/sf Run Times: Filter 1 = 60 hrs Filter 2 = 70 hrs Filter 3 = 94 hrs 5 4 Filter 1 Filter 2 3 2 1 0 NC AWWA WEA 2011 Q = 2 gpm/sf Run Times: Filter 1 = 157 hrs Filter 2 = 163 hrs Filter 3 = 165 hrs Filter 3 Pilot Filter Run Times
Pilot Filters 1 and 3 @ 2 and 3.8 gpm/sf 120.0 Average Run Time (hrs) 100.0 80.0 60.0 40.0 20.0 NC AWWA WEA 2011 0.0 Filter 1 Run Time -­‐ 2 gpm/
sf Filter 1 Run Time -­‐ 3.8 Filter 3 Run Time -­‐ 2 gpm/
gpm/sf sf Filter 3 Run Time -­‐ 3.8 gpm/sf Pilot Filter UFRV
Pilot Filters 1 and 3 @ 2 and 3.8 gpm/sf 18000.0 16000.0 Average UFRV (gal/sf) 14000.0 12000.0 10000.0 8000.0 6000.0 4000.0 2000.0 NC AWWA WEA 2011 0.0 Filter 1 UFRV -­‐ 2 gpm/sf Filter 1 UFRV -­‐ 3.8 gpm/sf Filter 3 UFRV -­‐ 2 gpm/sf Filter 3 UFRV -­‐ 3.8 gpm/sf • UFRV increased at higher rate of filtra\on Pilot Filter and Full Scale Filter Comparison
Run
Filtration Rate
Average
95th
Time
(gpm/sf)
UFRV
Turbidity
percentile
Full Scale Filter 4
66.3
2.1
8186
0.0256
0.06855
Pilot Filter 1 – Existing Townsend Media
95.8
2.0
11499
0.0300
0.0345
Pilot Filter 2 – Coarser Media
95.9
2.0
11504
0.0237
0.0269
Pilot Filter 3 – Ceramic Media
95.9
2.0
11510
0.0280
0.0333
Pilot Filter 1 – Existing Townsend Media
64.3
3.8
14655
0.0612
0.1939
Pilot Filter 3 – Ceramic Media
71.2
3.8
16227
0.0460
0.1368
Average
95th
Averages
Filtration
Rate (gpm/
Averages
Run Time
sf)
UFRV
Turbidity
Percentile
Pilot Filter 1 - Existing Townsend Media
91.0
2
10925
0.0556
0.0611
Pilot Filter 2 - Coarser Media
92.8
2
11135
0.0340
0.0420
Pilot Filter 3 - Ceramic Media
93.3
2
11200
0.0353
0.0439
Pilot Filter 1 - Existing Townsend Media
77.4
3.8
17637
0.0481
0.0571
Pilot Filter 2 - Coarser Media
89.6
3.8
20439
0.0337
0.0420
Pilot Filter 3 - Ceramic Media
94.6
3.8
21560
0.0349
0.0423
NC AWWA WEA 2011 Full Scale Filter 4
•  Pilot filters demonstrated longer run times and UFRVs
•  Pilot Filter 1 (existing media) run times appeared to improve after
backwashes with air scour
•  Average turbidities similar; 95th percentile of full-scale Filter 4
higher than pilot filters
Filter Performance: Turbidity
Full Scale Filter 4 and Pilot Filter Average and 95th Percen^le Turbidity 0.35 0.3 LT1 CFE Requirement Pilot Filter 1 Average 0.25 Turbidity (ntu) Pilot Filter 1 95th Percen\le Pilot Filter 3 Average 0.2 Pilot Filter 3 95th Percen\le 0.15 LT2 Enhanced Performance Full-­‐Scale Filter 4 Average Full-­‐Scale Filter 4 95th Percen\le Full-­‐Scale Filter 4 Average 0.1 Full-­‐Scale Filter 4 95th Percen\le 0.15 ntu 0.05 NC AWWA WEA 2011 0 0.30 ntu *May not meet LT2 Enhanced Performance (95th percen^le) Extended Terminal Sub-fluidization Wash (ETSW)
•  Extended Terminal Subfluidization Wash (ETSW) involves
extending the end of the backwash procedure with a low flow rate
that does not fluidize the media for a duration corresponding to
one filter-volume of water (Amburgey, 2005)
•  May help diminish the peak in turbidity during filter ripening;
possibly allowing a return to service without extended filter-towaste period
•  May improve filter performance
•  “Subfluidization” – low backwash rate (typically 3-6 gpm/sf)
•  ETSW rate for pilot testing – 5 gpm/sf
NC AWWA WEA 2011 •  Included in the pilot filter study to assess if ETSW would be
beneficial to filter performance
Pilot Filter 1 & 3 Turbidity – Standard vs. ETSW
0.25 Pilot Filter 1 and 3 Average and 95th Percen^le Turbidity Filter 1 Average Turbidity Filter 1 95th Percen\le Filter 3 Average Turbidity 0.2 Average Turbidity (ntu) Filter 3 95th Percen\le LT2 Enhanced Performance 0.15 Started ETSW 0.1 NC AWWA WEA 2011 0.05 0 4/6/2013 4/11/2013 4/16/2013 4/21/2013 4/26/2013 5/1/2013 5/6/2013 5/11/2013 Pilot Filter 1 & 3 Ripening – Standard Backwash
Pilot Filter 1 and 3 Ripening -­‐ 2 gpm/sf 1 0.9 0.8 Turbidity (ntu) 0.7 0.6 Filter 3 0.4 0.3 0.2 0.1 0 NC AWWA WEA 2011 Filter 1 0.5 0.15 ntu LT1 CFE Requirement 0.30 ntu LT2 Enhanced Performance Backwash Pilot Filter 1 & 3 Ripening – Standard Backwash
Pilot Filter 1 and 3 Ripening Data -­‐ 3.8 gpm/sf 1 0.9 0.8 Turbidity (ntu) 0.7 0.6 Filter 1 0.5 Backwash 0.4 0.3 0.15 ntu LT1 CFE Requirement 0.2 0.1 NC AWWA WEA 2011 0 Filter 3 LT2 Enhanced Performance 0.30 ntu Pilot Filter 1 & 3 Ripening - ETSW
Filter 1 and 3 Ripening Data – 3.8 gpm/sf with ETSW 1 Filter 1 3.8 gpm/sf 0.9 Filter 3 3.8 gpm/sf 0.8 0.15 ntu 0.30 ntu Turbidity (ntu) 0.7 0.6 0.5 0.4 0.3 LT1 CFE Requirement 0.2 0.1 NC AWWA WEA 2011 0 LT2 Enhanced Performance Conclusions/Recommendations
•  Adjusting backwash procedure in cool water conditions can result in
50% savings in washwater use and associated $$$avings
•  Cleaning sand media would likely be improved with air-scour
•  Run time and UFRV Filter 3 (ceramic cap) > Filter 1 (existing media)
•  Pilot Filter effluent turbidity < 0.3 using standard backwash
procedure
•  Pilot Filter effluent turbidity < 0.15 (LT2 Enhanced Performance) as
study progressed, particularly during runs with ETSW
•  Ripening spike in the pilot filters was dampened when using ETSW
NC AWWA WEA 2011 •  An air scour system could be installed in existing filters with a
ceramic media cap to improve performance
NC AWWA WEA 2011 New Backwash Pump Station and Meter Vault
Filter Performance: Particle Counts
Log Removal Total Par\cle Counts (Log(No/N)) 3.00 2.50 2.00 Filter 1 1.50 Filter 2 Filter 3 1.00 0.50 0.00 NC AWWA WEA 2011 7/17/2013 7/19/2013 7/22/2013 7/24/2013 7/31/2013 8/14/2013 8/16/2013 0 12 u Grab Sample 1000 5 u Grab Sample 8 u Grab Sample 2000 3 u Grab Sample 12 u Online 2 u Grab Sample Counts/ 100 mL 3000 15 u Online 4000 8 u Online 5000 2 u Online 7000 5 u Online Backwash Backwash 3 u Online 6000 9/24/2013 9/23/2013 9/23/2013 9/23/2013 9/23/2013 9/23/2013 9/22/2013 9/22/2013 9/22/2013 9/22/2013 9/22/2013 9/21/2013 9/21/2013 9/21/2013 9/21/2013 9/21/2013 9/20/2013 9/20/2013 9/20/2013 9/20/2013 9/20/2013 9/19/2013 9/19/2013 9/19/2013 9/19/2013 9/19/2013 9/18/2013 9/18/2013 9/18/2013 9/18/2013 9/18/2013 9/17/2013 9/17/2013 9/17/2013 NC AWWA WEA 2011 Filter Performance: Particle Counts (Pilot Filter 2)
8000 15 u Grab Sample