4-Log Virus Treatment under the Groundwater Rule Guy Schott, P.E.

4-Log Virus Treatment under the Groundwater Rule Guy Schott, P.E. State Water Resources Control Board August 17, 2017

Topics Groundwater Rule Source Waters Log Inactivation Types of Disinfectants Ct Basics Baffling Factor Ct & Log Inactivation Calculation Example Problems

Groundwater Rule Regulatory Requirements Groundwater Rule: Groundwater systems (GWS) that do not provide disinfection or do disinfect but do not get virus inactivation credit must conduct source water monitoring (E. coli) whenever they are notified of a total coliform positive (TC ) routing sample (Total Coliform Rule). As a result of the above rule, GWS may choose to provide 4-log virus treatment to forgo triggered source water E. coil monitoring due to a routine positive bacteriological distribution sample. Groundwater systems with significant deficiencies may be required to disinfect to achieve 4-log inactivation of viruses. – Fecal/E.coli – Inadequate construction – Near surface water source (possible influence)

Source Waters Vertical and Horizontal Wells Springs

Log Inactivation Understanding 4-Log Virus Treatment Virus treatment means virus removal and/or inactivation. Removal/inactivation of microorganisms, including viruses, generally is measured on logarithmic scale. Log – – – – inactivation of viruses relates to % inactivation of viruses. 1-log inactivation 9 out of 10 90% inactivation 2-log inactivation 99 out of 100 99% inactivation 3-log inactivation 999 out of 1,000 99.9% inactivation 4-log inactivation 9,999 out of 10,000 99.99% inactivation

Type of Disinfectants Chlorine Ozone Most common for small water systems Ultraviolet Radiation (UV) Chlorine Dioxide Chloramines

Ct Basics - Log inactivation is based on the Delivered Dose, “Ct” “C” is the disinfectant residual (mg/L) “t” is the exposure or contact time (minutes) Multiply them: C t mg/L min (delivered dose) The calculated Ct value is looked up in EPA Ct tables to determine the log inactivation based on specific monitoring parameters (pH, disinfectant residual and/or temperature). Ct value

Ct Table – Inactivation of Viruses by Free Chlorine, pH 6.0-9.0 Inactivatio n (log) 4 20 6 22 Temperature (oC) 10 12 8 14 16 18 24 2 4.4 3.8 3.4 3.0 2.6 2.2 1.8 1.4 1.0 1.0 1.0 3 6.7 5.6 4.8 4.0 3.6 3.2 2.8 2.4 2.0 1.6 1.2 4 8.9 7.6 6.8 6.0 5.2 4.4 3.8 3.4 3.0 2.6 2.2 Calculated Ct is 4.5 mg/L*min Temperature: 10oC From Ct Table: The log inactivation is somewhere between 3 and 4.

Ct Basics Disinfectant concentration “C” is measured before the first customer or outlet of water system. Exposure or contact time “t” is difficult of quantify. Theoretically, “Ƭ” is calculated as V (gal) H RT (Hydraulic Residence Time) Q (gal/min) where V tank and/or pipe volume and Q flow rate V Q

Baffling Factor (BF) Q1 V1 Ƭ V1/Q2 mg/L (disinfectant, C) Cl2 Ct mg/L min Q2 Baffling factor or short-circuiting factor (0.05 – 1): – Determined from tracer study or estimated – BF t10/ Ƭ from tracer study. t BF Ƭ

The Ct value is Analogous to UV Dose (It) It is the product of UV light intensity and exposure time “I” is in mW/cm2 (UV light Intensity) “t” is in seconds (exposure time) I t mW/cm2 seconds mJ/cm2 (delivered dose) It value

Calculating Ct and Log Inactivation Pipeline Contactor Pressure Tank Wel l Distribution System NaOCl Cl2 Daily grab ( 3,300 people) Continuous ( 3,330 people)

Pipeline Contactor Calculating Ct and Log Inactivation Pipeline Length (L): 520 feet Pipeline Diameter (D): 2-in 0.167-ft Well Flow: 30 gpm 2 2 Pipeline Volume (Vol): π D L 3.14 0.167 ft 520 ft 7.48 gal 85 gallons 4 4 ft 3 Baffling Factor (BF) for Pipeline: 1.0 (assume plug flow) Pipeline Contact Time: (Vol BF)/flow (85 gal 1)/(30 gal/min) 2.8 minutes Measured Chlorine Residual: 1.6 mg/L at water temperature of 14oC Calculated Ct: 1.6 mg/L 2.8 minutes 4.5 mg/L minutes (Delivered Dose)

Ct Table – Inactivation of Viruses by Free Chlorine, pH 6.0-9.0 Inactivatio n (log) 4 20 6 22 Temperature (oC) 10 12 8 14 16 18 24 2 4.4 3.8 3.4 3.0 2.6 2.2 1.8 1.4 1.0 1.0 1.0 3 6.7 5.6 4.8 4.0 3.6 3.2 2.8 2.4 2.0 1.6 1.2 4 8.9 7.6 6.8 6.0 5.2 4.4 3.8 3.4 3.0 2.6 2.2 Pipeline: Calculated Ct is 4.5 mg/L*min 4.4 mg/L*min (EPA Table) for temperature at 14oC at 4 log virus inactivation 4.5 4.4, therefore the water system is meeting at least 4 log virus inactivation.

Alternative Treatment UV Disinfection, 4-Log Virus Pressure Tank Wel l U V Distribution System Install UV Reactor that can achieve 4-log virus inactivation. UV Reactor must be validated in accordance with the 2006 USEPA UV Disinfection Guidance Manual (UVDGM). Contact: Anthony Oosterveld (519) 763-1032 or (519) 317-0428 [email protected] , viqua.com

Storage Tank Contactor Calculating Ct and Log Inactivation Storage Tank Wel l NaOCl Distribution System Cl2 Daily grab ( 3,300 people) Continuous ( 3,330 people)

Storage Tank Contactor Calculating Ct and Log Inactivation Operating Tank Volume (Vol): 6,000 gallons Well Flow: 30 gpm Tank Flow: 80 gpm Baffling Factor (BF) for Tank: 0.1 Tank Contact Time: (Vol BF)/flow (6,000 gal 0.1)/(80 gal/min) 7.5 minutes Measured Chlorine Residual: 0.8 mg/L at water temperature of 12oC Calculated Ct: 0.8 mg/L 7.5 minutes 6.0 mg/L minutes (Delivered Dose)

Ct Table – Inactivation of Viruses by Free Chlorine, pH 6.0-9.0 Inactivatio n (log) 4 20 6 22 Temperature (oC) 10 12 8 14 16 18 24 2 4.4 3.8 3.4 3.0 2.6 2.2 1.8 1.4 1.0 1.0 1.0 3 6.7 5.6 4.8 4.0 3.6 3.2 2.8 2.4 2.0 1.6 1.2 4 8.9 7.6 6.8 6.0 5.2 4.4 3.8 3.4 3.0 2.6 2.2 Storage Tank: Calculated Ct is 6.0 mg/L*min 5.2 mg/L*min (EPA Table) for temperature at 12oC at 4 log virus inactivation 6.0 5.2, therefore the water system is meeting at least 4 log virus inactivation.

Ozone Disinfection Calculating Ct & Log Inactivation Ozone Contactor Storage Tank Wel l O3 O3 Daily grab ( 3,300 people) Continuous ( 3,330 people) Distribution System

Ozone Disinfection Calculating Ct & Log Inactivation Operating Ozone Tank Volume (Vol): 1,000 gallons Well Flow: 30 gpm Baffling Factor (BF) for Tank: 0.4 Ozone Contact Time: (Vol BF)/flow (600 gal 0.4)/(30 gal/min) 8.0 minutes Measured Ozone Residual: 0.2 mg/L at water temperature of 10oC Calculated Ct: 0.2 mg/L 8.0 minutes 1.6 mg/L minutes (Delivered Dose)

Ct Table – Inactivation of Viruses by Ozone Inactivatio n (log) 4 20 6 22 8 Temperature (oC) 10 12 14 16 18 24 2 0.68 0.58 0.54 0.50 0.42 0.34 0.29 0.27 0.25 0.21 0.17 3 1.03 0.88 0.84 0.80 0.68 0.56 0.48 0.44 0.40 0.34 0.28 4 1.35 1.16 1.08 1.00 0.84 0.68 0.58 0.54 0.50 0.42 0.34 Ozone Tank: Calculated Ct is 1.6 mg/L*min 1.0 mg/L*min (EPA Table) for temperature at 10oC at 4 log virus inactivation 1.6 1.0, therefore the water system is meeting at least 4 log virus inactivation.

Log Inactivation Ct Comparisons (Delivered Dose) Disinfectant Delivered Dose mg/L min Virus Log Giardia cyst Log Cryptosporid ium Log Ozone 1.0 4.0 2.0 0.09 Chlorine 6.3 4.0 0.09 – 0.24 - Chlorine Dioxide 26.4 4.0 3.4 0.09 Chloramines 1,560 4.0 2.4 - 1 2 4 2 Temperature at 9oC; 2 MRDL: 4.0 mg/L as Cl2 3 pH: 6-9; 4 MRDL 0.8 mg/L as ClO2 1 3

UV Log Inactivation Disinfectant Ultraviolet Radiation (UV) Delivered Dose mW/cm2 sec (mJ/cm2) Virus Log Giardia cyst Log Cryptosporid ium Log 186 4.0 4.0 4.0

Website https://www.waterboards.ca.gov/ – Drinking Water – Drinking Water Field Operations Branch Districts – Mendocino – District 03 – CT Spreadsheets – CT Presentations