Using a Recirculating Aeration System to Remove Bromoform and Other Thms

Using a Recirculating Aeration System to Remove Bromoform and Other THMs

Russell Porter, P.E. May 9, 2014 Presentation Outline

Plant background & DBP history Description of pilot efforts Carbon Aeration Discussion of pilot results Conclusions Eagle Cove Homeowners Association San Juan Island – NW Washington ~30 residential connections All residential Well 10 gpm capacity NaOCl added 17,000 gallon reservoir Booster station System Schematic

17K Tank

Pressure Tanks

Distribution NaOCL Service Pump

Well Eagle Cove Homeowners Well Source

Raw well water quality pH = 7.7-7.8 TOC Average = 3.4 mg/L Range 2.7-4.5 mg/L Mn = 0.14 mg/L

Disinfection by-products High THMs Low HAA5s

Pb/Cu High Cu - 90% Percentile 0.73-2.15 mg/L Pb well below action level 200 THM History 180

160 Quarterly Sampling Running Annual Average (RAA) 140 MCL

120

100

80 THM, ug/L THM,

0 2005 Q1 2005 Q2 2005 Q3 2005 Q4 2006 Q1 2006 Q2 2006 Q3 2006 Q4 2007 Q1 2007 Q2 2007 Q3 2007 Q4 2008 Q1 2008 Q2 2008 Q3 2008 Q4 2009 Q1 2009 Q2 2009 Q3 2009 Q4 2010 Q1 2010 Q2 2010 Q3 2010 Q4 2011 Q1 2011 Q2 2011 Q3 Quarter 80

70 HAA5 History

60 Quarterly Samples Running Annual Average (RAA) MCL

40 L

30 HAA5, ug/

05 Q1 Q3 1 20 Q 2005 06 20 Quarter 2006 Q3 Q3 2007 Q1 07 20 08 Q1 Q3 20 08 Q1 3 20 Q 2009 09 20 2010 Q1 Q1 2010 Q3 11 20 11 Q3 Q1 20 12 Q3 1 20 Q 2012 13 1 20 Q 2013 Q3 14 20 THMs

Predominantly bromoform and bromonated THMs

Bromoform, CHBr3 – 64% Dibromochloro methane, CHBr2Cl – 25% Chlorodibromo methane, CHBrCl2 –9% Chloroform, CHCl3 –2%

Most systems are predominantly chloroform (Another San Juan system, for example)

Bromoform, CHBr3 –<1% Dibromochloro methane, CHBr2Cl – 2% Chlorodibromo methane, CHBrCl2 – 19% Chloroform, CHCl3 – 79% Initial Pilot Efforts

Investigate activated carbon.

Full-scale using carbon filter in a 55-gallon drum.

UV 254 and THM testing for performance System Schematic

17K Tank

Pressure Tanks NaOCL

Distribution Pilot Service Pump Carbon Unit

Well 0.8 Carbon was used up quickly – each barrel lasted 0.7 only about a month

0.6

THMs = 113 ug/L 0.5

0.4

0.3 THMs = 64 ug/L

0.2

UV absorbance treated/UV absorbance raw absorbance treated/UV absorbance UV A verage monthly use ~ 120,000 gallons 0.1

0 0 100,000 200,000 300,000 400,000 500,000 600,000 700,000 800,000 Gallons Treated THM Data A few days after startup, total THMs in the distribution system were sampled at 64 μg/L.

A month after startup, total THMs in the distribution system were sampled at 113 μg/L.

Carbon not the answer – cost too prohibitive to change drums frequently. Second Pilot - Aeration Aeration has been used effectively on THMs.

Aeration also can raise the pH for Cu/Pb. Theoretical pH rise given pH and alkalinity would be from 7.7 to 8.2. Second Pilot - Aeration Dissolved gases in water governed by Henry’s Law generically given as:

p = Hc

Where: p = Constituent pressure in gas H = Henry’s constant c = Constituent concentration in liquid Henry’s Law Constants Reflect Volatility of Gasses in Water

DBP H - atm Chloroform 200 Dichlorobromomethane 121 Dibromochloromethane 56 Bromoform 35

CH2ClCOOH 0.00051

CHCl2COOH 0.00046

CCl3COOH 0.00075

CH2BrCOOH 0.00037

CHBr2COOH 0.00024 THMs volatile but bromoform much less volatile than chloroform. Orcas Island Example – System Schematic Using Recirculating Aeration Aeration Pilot Spray System and Fan

Treatment Plant Pressure Tank

Distribution Recirculating Pump Service Pump Simple Spray Header with Recirculation 60% Removal – But Mostly Chloroform (78%) Aeration Pilot Something more efficient than spray aeration would be needed.

Options Packed tower Tray aerator – chosen option Predictive Mass Balance Model

C QC (Qr+Q)C Distribution

QwCi + QrCa QwCi Well

QrCa QrC

Recirculating Pump and Tray Aerator Mass Balance Model Assumptions Continuously mixed reservoir with concentration C

C(T=n+1) = C(T=n) + inputs – outputs + dTHM/dt

Aerator efficiency (η) = (C-Ca)/C

Ci is amount formed between chlorination at well and reservoir Qw (well) = Q (distribution system), Use average day flow in gpm Some THMs form in distribution system after the reservoir Mass Balance Model Assumptions Calibrate (as best as possible) with existing system with no aeration system

–Ci = ~50 μg/L – dTHM/dt adjusted to have appropriate C – Final tap is C + ~10 μg/L

Example model without aeration conditions

Ci=50 μg/L, C=140 μg/L, and tap concentration is 150 μg/L Mass Balance Model Predictions Recirculating aeration system can be added after calibration.

Qr and η varied to size unit to achieve desired final THM.

25 gpm (Qr), 5-tray aerator (η = 55%) was selected.

HOA leased/purchased a used unit from a groundwater remediation company. Initial Pilot Testing HOA initially leased the unit for a month to test.

Initial single pass test with flow to waste to verify manufacturer’s performance claim (η = 55%) .

Average Average Influent Effluent Removal Manufacturer Concentration Concentration Efficiency Predicted Contaminant (μg/L) (μg/L) (%) Removal (%) Bromoform 68.2 36.7 46 31

Chlorodibromomethane 38.8 9.1 77 55

Bromodichloromethane 13.6 1.1 93 85

Chloroform 3.8 ND 100 93

TOTAL 124.4 46.8 62 - Pilot Test Phase 2 Full scale recirculating system - Temporary piping Pilot Test Phase 2-Full Scale Operation

Distribution Day Finished pH THMs, μg/L 07.7132 48.063.3 58.1- 68.2- 27.1 98.1 55.5 Pilot Test Phase 2-Full Scale Operation

HOA decided to purchase the unit and built a permanent installation. 200

180 Compliance Sampling – 12.3 μg/L THM

160

140

120

100

80 L , ug/ THM 60

40 Quarterly Sampling Running Annual Average (RAA) Aeration MCL 20

0 2012 Q2 2012 Q3 2012 Q4 2013 Q1 2013 Q2 2013 Q3 2013 Q4 2014 Q1 Quarter Regulatory Full Scale Considerations

Washington regulates VOC releases through WAC 173-460. WAC 173-460 regulates Acceptable Source Impact Limit (ASIL) for toxic compounds. ASIL for Chloroform = 0.0435 μg/m3 Emitters must stay below ASIL as proven by analysis. WAC 173-460 sets Small Quantity Emission Rates (SQER) and de minimis amounts in lieu of analysis. Emission Rate Limits for THMs

Compound SQER, lb/yr

Chloroform 8.35

Bromoform 174

Bromodichloromethane 5.18

Chlorodibromomethane 7.1 Eagle Cove Compliance

For analysis assume: 2 MG Annual Water Use 150 μg/L THM 100% Removal 65% Bromoform 2.5 lb/yr (174 lb/yr limit) 25% DiBromochloromethane 0.6 lb/yr (7.1 lb/yr limit) 9% Bromodichloromethane 0.2 lb/yr (5.18 lb/yr limit) 2% Chloroform 0.05 lb/yr (8.35 lb/yr limit)

All values < SQER Eagle Cove is in compliance. Eagle Cove Compliance – Pb/Cu

Raw Water pH = 7.7 Aerated Water = pH 8.1-8.2 Pb/Cu scheduled for May 2014

Distribution pH used to verify aeration system operating. Conclusions Aeration is effective at reducing THMs at Eagle Cove.

~ 130 μg/L reduced to <20 μg/L

Higher efficiency unit required for bromoform –tray aerator still only achieved ~50% removal single pass.

Effect of pH elevation on Pb and Cu remains to be seen. Questions? Russell Porter [email protected] (206) 284-0860

Acknowledgements Eagle Cove HOA Jerry Opatz, ECHOA