Nitrification in the distribution System Nitrification ¢â‚¬¢Nitrate and Nitrite are currently not monitored

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  • Nitrification in the distribution System

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    Take Home Messages

    • Nitrification is a naturally occurring biochemical process

    • Nitrification causes water quality problems and can occur in any distribution system

    • The increased use of monochloramination has increased the likelihood of nitrification episodes

    • Distribution system monitoring can help to anticipate the onset of nitrification

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  • Nitrification

    • Prepared from literature provided by AWWA with assistance from Economic and Engineering Services, Inc.

    • http://www.epa.gov/ogwdw/tcr/pdf/nitrification.pdf

    Additional information about the chemistry and parameters for analysis for Nitrification can be found below

    • http://water.epa.gov/lawsregs/rulesregs/sdwa/tcr/upload/nitrification.pdf

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    Nitrification – What is it?

    A microbial process by which reduced nitrogen compounds (ammonia) are sequentially oxidized to nitrite and then to nitrate

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    http://www.epa.gov/ogwdw/tcr/pdf/nitrification.pdf

  • Nitrification

    • Nitrate and Nitrite are currently not monitored regularly in the distribution system

    • Action levels for Nitrite in distribution system are often listed at ~ 0.05 mg/L to ~ 0.15 mg/L

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    Method 10271

    Primarily, two types of bacteria cause nitrification

    • Nitrosomonas

    • Nitrobacter

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  • Nitrification

    • Note the production of excess Hydrogen Ion (H+) in the preceding reactions

    • This is the reason pH changes

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    NH3 NO2 NO3

    Hydrogen Ion

    Impacts of nitrification-chemical

    • Increase in nitrite and nitrate levels

    • Reduced alkalinity, pH, DO, and chloramine residual

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  • Impacts of nitrification-biological

    (bacteria)

    • Ammonia oxidizing bacteria increase

    • Nitrite oxidizing bacteria increase

    • HPC increase ( general indicator of bioactivity )

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    Decrease in pH and

    Alkalinity

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  • Change in pH and alkalinity-

    • Affects the Langelier calculation

    • Can lead to corrosion (lead and copper rule)

    • Optimum for nitrifying bacteria is

    pH 7.0 – 8.0

    • Affects chloramine decomposition

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    Nitrification indicators

    • Loss of chloramine residual

    • Decrease in DO

    • Drop in pH and alkalinity

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  • Nitrification indicators

    • Increase in water temperature

    • Increase in HPC populations

    • Nitrite/nitrate levels increase

    • Nitrifying bacteria counts increase 13

    Ammonia

  • Free ammonia

    • Almost completely eliminated when proper ratio of chlorine to ammonia is used to form chloramine (5:1)

    • Important for treatment and “boosting”

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    Ammonia

    • Excess can sometimes be found in finished water due to treatment errors

    • Also occurs naturally in some ground and surface waters

    –(normal levels are usually very low unless influenced by agriculture, for example)

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  • Nitrification – Ammonia

    Ammonia is released by many complex reactions within the distribution system

    Two species :

    • ionized (NH4 +) aka ammonium

    • un-ionized (NH3) aka ammonia

    –Species depends on pH and temperature at time of sample collection

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    Ammonia

    • Can be released by:

    –Chloramine decay (autodecomposition)

    –Corrosion products at pipe surfaces (catalysis)

    –Oxidation of nitrite by chloramine

    –Oxidation of organic matter

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  • Nitrogen,Free Ammonia and Chloramine (Mono) –

    Method # 10200

    • Patented method

    • Works well in most samples

    • A sequential method used to determine both analytes

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    Method 10200

    Method 10200

    • First measure the monochloramine

    • Next convert remaining free ammonia to monochloramine by adding hypochlorite

    • Then determine the increase in monochloramine and calculate free ammonia

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    Method 10200.pdf

  • Nitrification Monitoring

    • Total chlorine

    • Monochloramine

    • pH

    • Alkalinity

    • Nitrite/Nitrate

    • DO

    • HPC

    • DBP’s

    • Nitrifying bacteria

    • Free ammonia

    • Temperature

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    Distribution Monitoring

    • It is nearly impossible to measure every parameter

    • Use indicators to monitor your system

    • Collect data to establish baseline

    • Look for deviations in “normal” readings

    • More data increases chances of correct interpretation

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    Total Cl2.pptx Monochloramine.pptx pH.pptx Nitrite-Nitrate.pptx HPC.pptx

  • Grab Sample

    • Good way to start

    • Characterize your system

    • Begin to accumulate data, select monitoring sites

    • “Better than nothing”

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    Trending – Data Accumulation

    • Collecting baseline data is a crucial aspect of monitoring in the distribution system

    • Need to collect enough reliable data to determine:

    –Normal variation

    –When a deviation has occurred

    –When the problem has been corrected

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  • What Tests?

    • A baseline must be established of standard tests values

    –pH, free ammonia, disinfection residual, temperature, turbidity, conductivity, chlorine, alkalinity, …

    –Nitrite and Nitrate 25

    Look for Patterns

    • No single analysis can give the complete picture

    • Try to reduce errors in sampling and analysis to improve data quality

    • Compare trends to baseline:

    –learn to distinguish between seasonal, known variables

    –true excursions or other anomalies

    –when data has returned to baseline 26

  • Nitrification in the distribution System

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