Virginia Section AWWA
April 5, 2017
4/4/2017
NITRIFICATION CHEMISTRY AND FACTORS THAT INFLUENCE MONITORING AND CONTROL
BEN KLAYMAN, PhD, PE
SAFETY MOMENT – SPRING BREAK!!!
• Be active • Plan a successful trip • Protect yourself from the sun
• Watch your step • Know the ropes • Eat Healthy
• Additional tips for young adults
Source: Center for Disease Control (https://www.cdc.gov/family/springbreak/)
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PRESENTATION OUTLINE AND OVERVIEW
• Nitrification overview
• Nitrification monitoring
• Nitrification control strategies
• Development of nitrification action plans
• Summary
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NITRIFICATION OVERVIEW
From the beginning…
CHLORAMINATION
• Free chlorine combined with ammonia
• Has been in use for approximately 100 years
• Used by greater than 25% of utilities
• Use on the rise in recent years due predominantly to DBP regulations
CHLORAMINATION
• Pros
• Cons
• Lower levels of regulated disinfection byproducts; in response to Stage 2 D/DBP Rule
• Nitrification!
• Fewer taste and odor complaints than free chlorine
• Lower ORP; weaker oxidant
• Good secondary disinfectant
• Potential for increase in lead corrosion
• Many studies show improved biofilm control
• Seasonal HPC control challenges
• Formation of currently unregulated DPBs
• Nitrification!
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SEASONAL HPC CONTROL CHALLENGE
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CHLORAMINE CHEMISTRY
• Goal to form monochloramine
• Factors affecting Chloramine formation
• pH
• Ratio of chlorine to ammonia
• Kinetics ‐8
FREE AMMONIA
• Inefficient chloramine formation
• Decay due to auto‐decomposition reactions of chloramine • Loss or demand due to reactions of chloramines with natural organic matter, iron, nitrite
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WHAT IS NITRIFICATION?
• Conversion of free ammonia to nitrite and nitrate
• Reported in greater than 50% of system that use chloramines • Nitrification is a 2 step microbially driven process
• Ammonia oxidizing bacteria convert free ammonia to nitrite
• Nitrite oxidizing bacteria convert nitrite to nitrate
FACTORS AFFECTING NITRIFICATION
• Free ammonia concentration
• Temperature
• Total chlorine concentration
• System cleanliness / Disinfectant demand
• System demand (time)
• HPC
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IMPACTS OF NITRIFICATION
• Loss of chlorine residual
• Increased HPC and general microbial growth
• Formation of nitrite and nitrate
• Drop in pH and alkalinity
• Increase in rate of corrosion and metals release
• Increased potential for legionella
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DISTRIBUTION SYSTEM WATER QUALITY
NITRIFICATION MONITORING
Seeing is believing…
START WITH AVAILABLE HISTORICAL DISTRIBUTION SYSTEM DATA
• Lead and Copper Rule data • Lead, copper, pH, alkalinity, hardness
• Total Coliform Rule data • Coliform incidents, disinfectant residual levels
• System maps
• Sources, treatment, DS materials, sample locations, storage tanks, dead ends • Hydraulic model results (water age)
• Miscellaneous water quality
• HPC, turbidity, Iron
• Water quality complaint records
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NITRIFICATION MONITORING PARAMETERS
• Total chlorine concentration
• Free ammonia
• Nitrite
• Nitrate
• HPC (ATP)
• pH
• Alkalinity (more critical for low alkalinity waters)
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NITRIFICATION MONITORING LOCATIONS
• Focus on problem areas (from historical data)
• Areas where water age is known to be high
• Representative pressure zones
• Storage facilities
• Both inlet and outlet
• Checking for stratification
• Special locations
• Wholesaler connections
• Sensitive customers
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NITRIFICATION MONITORING FREQUENCY
• Monthly during non‐nitrification season
• Important to establish baseline conditions
• Increase frequency as temperature warms
• Minimum weekly sampling during nitrification season
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SAMPLE MONITORING DATA ‐ NITRATE
Here nitrate was used to detect onset of nitrification. Onset lagged peak temperature by almost 1 month.
Sharp increase in nitrate concentration indicates onset of nitrification
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CONTROL STRATEGIES
Know what can and can’t be controlled…
NITRIFICATION CONTROL STRATEGIES
• Check treatment and chemical feed!
• Want free ammonia < 0.05 mg/L if at all possible
• Ensure optimal pH
• Operations
• Boost chloramine residual
• Reduce storage
• Implement / Increase flushing
• Mixing, deep cycling or cleaning of tanks
• System design
• Free chlorine burn
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ACTION PLANS
Putting it all together…
DEVELOPMENT OF AN ACTION PLAN
• First step should always be to check and optimize treatment chemical addition
• Develop sequential steps (i.e. action levels) depending on severity of nitrification as detected from monitoring
• Know what can and can’t be controlled
• Reduce storage time until you are uncomfortable but safe and compliant
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SAMPLE NITRIFICATION ACTION PLAN
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SUMMARY NITRIFICATION SUMMARY
• Understand chloramination and nitrification basics
• Monitor monitor monitor
• Know what you can and can’t control
• Don’t wait for onset of nitrification
• Put it all together in an action plan (and use it!)
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THANK YOU!
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