1. THM Removal – Small System Applications
Aug 14, 2008 Draft
THM Removal – Small System Applications
Finger Lakes Conference – Watkins Glen
Thomas F. Clark, P.E.
Monroe County Water Authority

2. DBP Control Efforts MCWA system overview
DBP reduction water spray system
Results
Pembroke tank

3. Aug 14, 2008 Draft

4. Monroe County Water Authority
Shoremont Treatment Plant
145 MGD

5. MCWA Service Area

6. MCWA Zones
MCWA operates 28 separate pressure zones – each are essentially a small supply.
One or two points of water entry with tankage.
Each one is a small system….some are quite small demand-wise.

7. Pembroke New York One of these zones is the Pembroke zone.
MCWA buys water from Erie County Water Authority.
Just as many systems do, we purchase treated, disinfected water.
We have no control over the initial water quality that we receive.

8. Service Area by Supply
Pembroke Booster
Pump Station

9. Path of Water Aug 14, 2008 Draft ECWA VandeWater Treatment Plant
MCWA Pembroke BPS
Pembroke service
area
26 miles from plant to BPS

10. DBP Formation Time NOM + Cl2 DBPs Temperature pH Aug 14, 2008 Draft
We’re all familiar with the process that forms DBP’s. With regard to pH and temperature of Lake Erie, the parent supply is helpless.
Temperature pH

11. Town of Pembroke
Several hamlets and the Village of Corfu constitute the Genesee Water District. MCWA assumed operation of the district in 2003.
Approx 500 accounts in the district plus another 670 accounts in the Village of Corfu and the Town of Darien, further south along Rte 77.
Average demand ~ 400,000 gpd

12. Aug 14, 2008 Draft
Pembroke BPS
Pumping distance is approx 26 miles from Buffalo to the BPS in Pembroke.
Because of travel time, THM levels coming into Pembroke can be problematic during the late summer after Lake Erie water has warmed.

13. Historic THM Data at Entry Point
Aug 14, 2008 Draft
Historic THM Data at Entry Point
Quarterly sample results………additional samples during 2010 showed levels of THMs entering the zone rose as high as 88 ppb.

14. Pembroke System
The water enters our grid and moves 3 ½ miles to the Pembroke tank.
The tank is 0.5 MG capacity.
Retention time of water within the tank is 4- 5 days.

15. Pembroke System
Upon leaving the tank, water moves another (nearly) 5 miles (about 4 days travel) to our 2594 Main Road DBP sample site.
THMs at sample point have been higher than our in house goal of 64 ppb during the summer.

16. Pembroke Grid

17. Pembroke Tank 31 ft diameter 61 ft tall Steel plate construction
0.50 MG capacity
Water spray aeration
added in 2010 due to
high DBP levels

18. Why Water Spray?
Chloroform and dichlorobromomethane are two THMs that are relatively volatile.
One benefit…..increasing water temperature increases Henry’s Law constant and increases THM removal.
Reports are being prepared by engineers in both this country and in Canada describing removal of THM compounds by either water spray or aeration.

19. Why Water Spray? We have optimized treatment at the plant.
Localized treatment allows us to zero in on “problem” areas of water in the distribution system.
The MCWA opted for a water spray at tanks due to the height of the tank and the desire to keep equipment out of the tank.

20. Inflow/Discharge Line
Aug 14, 2008 Draft
Pembroke Water Spray T
Tank Inlet Line
Tank Outlet
Inflow/Discharge Line

21. Riser Piping
Sch 80 PVC pipe
2 inch diameter

22. Tank Penetration Penetration into the hatch- bulk head fitting.
From 7 to 25 ft in
separation between
spray heads and water surface.

23. Aug 14, 2008 Draft
Multi-spray head
Two were inserted into the top of the tank. Each head is brass costing about $ 300 each.
To be replaced with stainless steel for longevity.
Fog particle ~ 2000 microns

24. Spray Heads

25. Hypo System
Because of the long travel time to the hamlets at the east end of the season, we also added a sodium hypo disinfection system. This allows us to keep a free residual at the end of the system.

26. Pembroke Tank
To assist with moving water faster, we have the option of installing an automatic flush unit at the eastern end of the system.

27. Pembroke Tank- Autoflushing
The unit is set to release about 100 gpm for 90 minutes each night.
This is equivalent to about 1.25 ft of water in the Pembroke tank

28. Pembroke Water Spray- 2010-2011
In 2010, Pembroke water spray turned ON July 6.
Water flow through the aeration unit was 65 gpm.
=>About 4-5 day recirculation rate.

29. Water spray started July 8
Aug 14, 2008 Draft
Pembroke Results- 2010
Water spray started July 8
Immediately, we obtained 47 % removal in both the July 13 and July 20 samples.
The following week saw some problems with undetected loss of the pump system and the removal went down to
35 – 40 %

30. THM level at monitoring site
Aug 14, 2008 Draft
And at 2594 Main Rd
Water spray started
July 8th
THM level at monitoring site
drops 12 days later
Loss of power to water
spray pump ?
Values at the monitoring site went from 99 ppb to 65 ppb and 57 ppb before rising again due to lapses in operation.
Average value at our monitoring site was 66 ppb, just a little higher than our in house goal of 64 ppb.

31. Pembroke Water Spray
Pembroke water spray turned ON July 16, 2011.

32. resulting in increase in THMs
2011 Data
Aug 14, 2008 Draft
Reduced system demand
resulting in increase in THMs
Water spray ON
July 16
July 12 was the last baseline sample taken prior to the spray going “ON”
Water spray ON July 16th….got 40 % reduction on 7/26 but no change yet at the monitoring location.
We saw a 46 % reduction on 8/8 PLUS the treated water reached our monitoring location lower than our goal of 64 ppb.
Spike on 8/23 at 2594 Main Rd due to collapse in demand (rain came).
Our autoflush unit went on and 2594 went from mid 70’s to mid 40’s
Water cost was about $ 800 based on $ 3.97/1000

33. Water Temperatures Within the tank, the water temperatures were:
2010 average 65 degrees F
max 70 degrees F
2011 average 67 degrees F
max 72 degrees F

34. THM Removal Data Summary
In our water, 63 % of our THMs are chloroform………28 % is dichlorobromomethane.
The majority of THMs removed has been chloroform and dichlorobromomethane.

35. THM Removal Data Summary
In 2010, our removal percentage within the tank was 43 %.
In 2011, our removal percentage within the tank was 42 %.

36. THM Removal
The THM reduction at the compliance site(s) will depend on the amount of water entering into the system from the treated tank.
If only half the water at a compliance site is from a treated tank where you are getting 40 % THM removal, you may only see a 15 – 20 % reduction in THM levels.

37. Cost of Treatment- Pembroke Water Spray
A 7 ½ Hp pump
Assuming $ 0.15/kw-hr
85 % efficiency
Cost for four months of operation, 24 hrs/day = $ 1920 ($ 16/day)

38. Pembroke Tank
Major components include 7 ½ Hp pump, PVC pipe, two multi-head water spray nozzles
Total cost of components was approximately $ 7,000.

39. Cost of Treatment- Pembroke Tank
Capital Cost : $ 7,000
Includes pump and VFD, piping and spray nozzles
Operational:
$1920 electrical ($16/day)
Based on water delivered to East Pembroke, water spray cost was $ 0.10/1000 gal

40. Water Rates- Pembroke 15 cents per day for a ¾ inch meter
Commodity charge of $ 3.97/1000 gallons

41. Aeration – NYS Regulatory Impact
NYS Air Quality Standards –
Item 27- Trivial Activities
Air stripping processes used on public water supply systems are “trivial and exempt from permitting requirements.”

42. 2013 Activities
Check removal efficiency at 50 degrees F and 68 degrees F
Check removal efficiency at 25, 50, 75 and 100 % motor speed.

43. Other MCWA DBP Removal Sites

44. Pavilion Tank

45. Pavilion Tank 320,000 gallon tank
170 scfm rotary vane compressor and diffuser manifold
The air line is tapped into the base wall of the tank

46. Mumford Tank
300,000 gallon storage tank
75 gpm water spray

47. Recommendations to Others
Design electrical services with sufficient capability to operate small pumps if DBP problems are encountered or anticipated …especially in remote parts of the system.
Power loss alarms to detect loss of power to the pump. (Not a pressure alarm.)

48. Recommendations to Others
Make sure the penetration into the tank is done in a sanitary manner.
If discharge lines are disconnected for the winter, secure openings.
Water main design – don’t over size.

49. Recommendations to Others
If “in house” fabrication isn’t possible, there are manufactured units which have proven effective in THM removal.
A Medora Spray THM Removal System is one such system.  The design is a 3 part system - mixing, stripping and ventilating. 

50. Recommendations to Others

51. THM Removal Proven Results, Fall 2012
Average result across seven systems: 51% reduction
Design goal 40-50% TTHM reduction
37%
Red.
29%
Red.
68%
Red.
68%
Red.
43%
Red.
48%
Red.
62%
Red.
Notes: 1) All are lab test results shown except CA1 and CA2 which are from an oral report by operator Dec 20, 2012
2) Results shown are utilizing the floating spray nozzle system design, except OK1 which is the fixed nozzle system design

52. New Supply? Is a properly protected, drilled well possible?
True groundwater should not have any significant concentration of DBP precursors. THM generation should be minimal.
A well can be run seasonally to modify water treated by the “parent” utility or the purchasing utility.

53. Flushing to minimize DBPs
Your only option may be to what store owners do……periodically flush and release stale, off-quality water (produce) from your system.

54. Flushing to minimize DBPs
Routine flushing will improve water quality, increase your demand and will reduce detention time in the system.

55. Flushing to minimize DBPs
As an example….consider a 1 mile stretch of 8 inch main. This length of pipe will hold 13,800 gallons of water.
If you were to flush at 200 gpm, it would take a little over one hour to replace all the water in the main.
The cost?

56. Flushing to minimize DBPs
If water costs $ 3.50/1000 gallons, then you would have lost $ 48 worth of water.
This regulation is going to cost no matter what !!!!!!

57. Thank You
Dave
Ryan

58. Question
Does anyone here purchase untreated rock salt for use in their softening plant? If so, please see me.

59. Question
Does anyone here need to purchase Calgon (powdered) carbon, WPH ? If so, please see me. We have some discounted for sale.