New Rules for Disinfection Byproducts Is your system compliant? Presentation Topics. Achieving Compliant Water Means Balancing the Ultimate Goals

Transcription

1 New Rules for Disinfection Byproducts 2006 APWA International Public Works Congress and Exposition Kansas City, Missouri Vice President Presentation Topics Disinfectant/Disinfections Byproducts Rules (D/DBP) Source to Tap Approach for Reducing DBPs Other Distribution System Water Quality Benefits Chloramines Pros and Cons Summary Achieving Compliant Water Means Balancing the Ultimate Goals Improve Disinfection to Kill Microbials Reduce Disinfection Byproducts 1

2 History of Rules (TTHM and HAA 5 ) to Today s Stage 2 D/DBP Rule Total THM Rule TTHM < 100 μg/l (RAA) Stage 1 D/DBP Rule TTHM < 80 μg/l (RAA) HAA 5 < 60 μg/l (RAA) Stage 2 D/DBP Rule TTHM < 80 μg/l (LRAA) HAA 5 < 60 μg/l (LRAA) Effective Date of the Rules Stage 2 D/DBP Rule Other Details Requires PWS to monitor high DBP sites Sites selected during Initial Distribution System Evaluation (IDSE) Monitoring based on size and source water type Three main components: Consecutive Systems Operational Evaluations IDSE Stage 2 D/DBP Rule Impact on Consecutive Systems Most drinking water regulations don t specifically address consecutive systems (CS) DBPs aren t like most contaminants Water age is a factor, can increase in DS, etc Result is discrepancy in how CS are handled from state to state Stage 2 D/DBP rule tries to close the loop on consecutive systems 2

3 Stage 2 D/DBP Rule Consecutive Systems Requirements TTHM/HAA 5 MCLs = 80/60 as LRAA Must meet monitoring, reporting, recordkeeping, public notification and other requirements Must conduct IDSE Due with largest system in the combined DS Combined DS Stage 2 D/DBP Rule monitoring Must collect at least one sample in each CS Stage 2 D/DBP Rule Operational Evaluations Can have periodic high DBP concentrations and still comply with MCLs But, if (Q1 + Q2 + 2Q3)/4 > MCL then required to conduct an Operational Evaluation Stage 2 D/DBP Rule Operational Evaluation Requirements Examine treatment and distribution practices to determine contributors to high TTHM or HAA 5 formation Does not require system to implement changes to correct contributing factors as long as system remains in compliance with MCLs 3

4 Stage 2 D/DBP Rule Initial Distribution System Evaluations Why How What... intended to select new monitoring sites that more accurately reflect sites representing high TTHM and HAA5 levels.... based either on system specific monitoring or other system specific data.... recommend new or revised monitoring sites to their primacy agency based on their IDSE. Stage 2 D/DBP Rule More IDSE Facts Who has to conduct an IDSE? System using primary or secondary disinfectant (other than UV) Exemptions for NTNCWS < 10,000 Waivers for systems < 500 or all individual TTHM/HAA 5 compliance samples < 40/30 What are IDSE options? System Specific Study (SSS) Standard Monitoring (SM) Stage 2 D/DBP Rule Compliance Schedule Submit IDSE Plan* Complete IDSE Submit IDSE Report Begin Stage 2 Monitoring Compliance Dates by System Size* 100,000 50,000 99,999 10,000 49,999 October 1, 2006 April 1, 2007 October 1, 2007 September 30, 2008 March 31, 2009 September 30, 2009 January 1, 2009 July 1, 2009 January 1, 2010 April 1, 2012 October 1, 2012 October 1, 2013 < 10,000 April 1, 2008 March 31, 2010 July 1, 2010 October 1, 2013 * Consecutive systems follow schedule of largest system in combined distribution system ** 40/30 certification due for qualifying systems 4

5 Stage 2 D/DBP Rule Summary Stage 2 DBPR will increase the overall compliance challenge Each site must meet MCL Shift to high DBP locations Create the appearance of higher DBP levels Stage 2 D/DBP rule closes the loop on consecutive systems Reduces peak and average DBP concentrations Operational Excursions Stage 2 DBPR is here. Are you ready? Reducing DBPs Source to Tap Toolkit Source Management Treatment Distribution System Point of Use Devices Managing the formation of disinfection byproducts can involve a source to tap strategy. Reducing DBPs Treatment Techniques Chlorine downstream of coagulation / clarification Alternative primary disinfectant: Ozone Chlorine dioxide UV Membranes (ultra or nano) Convert to chloramines as secondary disinfectant A disinfection strategy must balance the needs of microbial inactivation to DBP production. 5

6 Reducing DBPs Treatment Techniques Powder activated carbon Granular activated carbon Magnetic ion exchange (a.k.a. MIEX ) Improved coagulation techniques Lower ph coagulation Alternative coagulant Coagulant aids Reducing organic compounds benefits not only known DBPs, but potentially those that exist but are not yet identified. Reducing DBPs Distribution System Operations Minimize water age (< 3 days ideal) Effective tank mixing and cycling Eliminate or routinely flush dead ends Flush low velocity mains Stable ph is important THMs from free chlorine can increase as much as 50% from the time the water leaves the plant until it reaches the customer. Other Possible Distribution System Water Quality Benefits Tank mixing Improve disinfection residual Reducing overall water age Mitigate taste and odor deterioration Reduce nitrification condition (associated with chloramines disinfection) Without effective mixing, thermal stratification can occur with as little as 1 to 2 degrees C, thus impacting water quality. 6

7 Other Possible Distribution System Water Quality Benefits Unidirectional flushing Improves water quality faster by maximizing flushing velocity UDF delivers clean water to areas being flushed It reduces amount of water required Can reduce colored water complaints Chloramines Pros and Cons Why are many switching to chloramines? Reduce disinfection by-product (DBP) levels Minimize peak DBP occurrences Improves disinfectant residuals throughout the distribution system Penetrates biofilms and reduces the possibility of coliform regrowth Improves taste and odor of finished water Chloramines Definition Chloramines - chlorine / ammonia combined in water Common inorganic chloramine species Monochloramine NH2Cl Dichloramine NHCl2 Trichloramine (nitrogen trichloride) NCl3 Monochloramine is the desired species. 7

8 Chloramines History of Its Use First U.S. Application 1918 Pre- Stage 1 D/DBP Rule 30-34% (ICR) Stage 1 D/DBP Rule 1998 Projected Stage 2 D/DBP Rule ~ 50% % of U.S. utilities by 1930s First TTHM Rule 1979 Post Stage 1 D/DBP Rule ~ 40-45% Stage 2 D/DBPR 2006 Chloramines Benefits & Drawbacks Benefits Excellent DBP control Minimize Cl 2 T&O Biofilm control Widely practiced Relatively inexpensive compared to GAC and other advanced technologies Short implementation time Drawbacks Less effective than Cl2 as disinfectant Nitrification Damaging to some rubber / elastomer materials 3rd party impacts Adverse health effects? Chloramines Definition of Nitrification Nitrification is the microbiological oxidation of ammonia to nitrite and ultimately to nitrate Ammonia Oxidizing NH 3 NO - Bacteria (AOB) 2 Ammonia Nitrite Typically Nitrosomonas sp. in distribution systems 8

9 Chloramines Water Quality Spiral With nitrification chloramines residual degrades Free NH 3 is released AOB oxidize NH 3 to NO 2 - NO 2 - degrades chloramines residual Bacteria grow Coliforms explode Chloramines Factors Affecting Nitrification Temperature Chlorine-to-ammonia ratio Free ammonia concentration Chloramines dose Water age (systems built for fire flows/storage needs not drinking water!!!!) Reservoir mixing and turnover Chloramines Traditional Nitrification Control Measures Implement detailed monitoring plan and early alert system Switch back to free chlorine for one month per year Resolve common inlet/outlets problems in tanks Establish effective flushing program Reduce detention time/stagnant water in distribution system and tanks Breakpoint chlorination for problem areas in distribution 9

10 Chloramines Importance of Chlorine to Ammonia Ratio Optimum Cl 2 to NH 3 -N ratio = 4.5:1 to 5:1 Goal of minimizing the free ammonia concentration As the chloramines concentration decreases, the ratio usually decreases NH 3 = 0.5 mg/l Total Chlorine Residual, mg/l NH 2 Cl 5:1 Ratio NH 2 Cl and NHCl 2 Breakpoint ~ 7.6:1 Ratio Free Cl 2 Possibly some NCl 3 Cl 2 between 0 and 2.5 mg/l Cl 2 between 2.5 and 5.0 mg/l Cl 2 greater than 5.0 mg/l Chloramines Nitrification Monitoring and Control Plan Regularly monitor: Nitrite and potentially nitrate coupled with ammonia loss Chloramines residual drop Increase in HPC and biomass ph, alkalinity, and DO reductions Early warning is critical Ammonia or Nitrite Concentration as Nitrogen (mg/l) Total Ammonia Nitrite Total Chlorine Total Chlorine (mg/l) Chloramines Nitrification Monitoring and Sampling Plan Analysis Temperature Total Chlorine Free Chlorine ph Nitrite Total Ammonia HPC Total Coliforms Analysis Frequency Storage Tanks: Monthly 1 Distribution Sites: Weekly Storage Tanks: Monthly 1 Distribution Sites: Weekly Storage Tanks: Monthly 1 Distribution Sites: Weekly Storage Tanks: Monthly 1 Distribution Sites: Weekly Storage Tanks: Monthly 1 Distribution Sites: Weekly Storage Tanks: Monthly 1 Distribution Sites: Weekly Storage Tanks: Conditional 2 Distribution Sites: Monthly 2 Storage Tanks: Conditional 3 Distribution Sites: Routine Weekly Sampling Method: Thermometer DPD: Hach Method 8167 DPD: Hach Method 8021 Hach EC10 ph meter or equivalent Diazotization: Hach Method 8507 Salicylate: Hach Method 8155 Pour Plate Method Colilert Method 10

11 Chloramines Nitrification Control Strategy Discovered Visit in 1995 to Gulf Coast Water Authority for a taste and odor evaluation; system using ClO 2 and chloramines What s nitrification? Hypothesis testing: Chlorite ion control of nitrification Bench testing showed that low levels of chlorite inactivated AOB (e.g., 0.05 mg/l) Abilene Ft. Worth Houston GCWA Corpus Christi Chloramines Nitrification Control Strategy with Chlorite Willmar, MN Full-scale Utica, NY Pilot-scale Utica, NY Contra Costa WD Bench-scale Water Dist. Glendale, CA Demo-scale Tucson, AZ Bench, Pilot & Demo-scale Marshalltown, Iowa Full-scale Birmingham, AL Pilot-scale Chloramines Pilot-Scale Chlorite Studies Purpose of pilot studies was to determine most effective nitrification control measure for each utility Pilot testing included the following control measures: High chloramine concentration (2.5 mg/l vs. 1.5 mg/l) High chloramine ratio (5:1 vs. 3:1) Different levels of chlorite ion fed continuously (0.1, 0.2, 0.4, and 0.8 mg/l) Chlorite ion fed intermittently at doses of 0.05, 0.2, and 0.8 mg/l to control nitrification 11

12 Chloramines Impact of Continuous Low Level Chlorite Ion Ammonia and Nitrite as N (mg/l) mg/l Chlorite Ammonia as N - Bottom Nitrite as N - Bottom Weeks As little as 0.1 mg/l of chlorite Ion fed continuously COMPLETELY prevented nitrification Summary Know the rule and comply (IDSE, etc.) When considering DBP control, understand impacts to microbial With treatment process changes, understand other DBP impacts (ozone, chlorine dioxide, etc.) Enhancing distribution system performance to control DBPs can help in other ways Converting to chloramines can reduce DBP but create other water quality issues if not managed Consider a source to tap toolkit approach Questions/Further Information Coit Road, Suite 1200 Dallas, TX Tel: (972) rmccollum@pirnie.com New Rules for Disinfection Byproducts: Kansas City, MO 12