Outline of NAP DAM Presentation: Brief overview Six workshops 1. - - PDF document

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Directed Assistance Module (DAM) 8:

Nitrification Action Plans (NAPs)

Developed by the TCEQ Water Supply Division (WSD) Texas Optimization Program (TOP) Presented by the WSD Financial, Managerial, and Technical (FMT) Capacity Development Contractor

• v. 2

Outline of NAP DAM

 Presentation: Brief overview  Six workshops

• 1. Sample Sites
• 2. Monitoring Frequency
• 3. Methods
• 4. Goals, baselines, and triggers
• 5. Actions
• 6. Communication strategies

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Outline of Presentation

 Chloramination  Nitrification

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Chloramines

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The chemicals of interest

 Chlorine

– Regardless of gas or other source, in water it is hypochlorite ion and hypochlorous acid

 Ammonia

– “Free Available” ammonia

 Inorganic (what is being dosed)  Organic (what is in some source water)

 Chloramines: Mono-, Di-, Tri-

– Monochloramine is what we want

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O

H

Cl Cl

H

O

Cl Cl

O

• N

H H H

H

N

H H H

Cl

N

H

Yuefeng Xie’s Bar Theory

• f chloramination

 This chlorine molecule walks into

a bar…

– At first, there are lots of free available ammonia molecules….

 Later, a chlorine molecule walks

into a bar…

– And all the free available ammonia molecules were used up…

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N

Cl

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Chloramine chemistry

 HOCl + NH3  NH2Cl + H2O  NH2Cl + HOCl  NHCl2 + H2O  2 NH2Cl

 NHCl2 + NH3

 NHCl2 + HOCl  NCl3 + H2O

 2 NH2Cl + HOCl  N2 + 3 Cl- + 3 H+ + H2O

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Breakpoint curve

Total Chlorine Species Cl2:N mass ratio 5:1 7.6:1

Free Ammonia

Mono- chloramine Dichloramine Trichloramine

Free Chlorine Total Chlorine = The sum of the active chlorine species

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Breakpoint curve: Question

 What CAN you measure?

– Using normal equipment Chlorine Residuals: Total and Species (mg/L) Cl2:NH3-N (Chlorine to Ammonia-Nitrogen mass ratio)

Free Ammonia

Mono- chloramine

Free Chlorine

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Nitrification

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Nitrification

 Nitrification happens when bacteria

called nitrifiers ‘eat’ ammonia, then nitrite, to form nitrite, then nitrate.

 Nitrification causes loss of residual

chloramines.

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The chemicals of interest

 Normal chloramine reactions,

 in the monochloramine zone:

HOCl + NH3  NH2Cl + H2O 2 NH2Cl  NHCl2 + NH3

 Nitrification

NH3 + O2 AOB NO2

• + 3H+ + 2e-

NO2

• + H2O NOB NO3
• + 2H+ +2e-

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Nitrification in the environment

NITRITE (NO2

• )

Nitrosomonas bacteria (AOB) uses up ammonia and makes NITRITE

PLANT FERTILIZER

AMMONIA

Wastew ater effluent

Plant remnants Fish excreta and urine

NITRATE BUILD UP

Gases

ANAEROBIC BACTERIA

NITRATE (NO3

• )

Nitrobacter bacteria (NOB) uses nitrite to make NITRATE Run off

Nitrification in a pipe

Nitrosomonas bacteria (AOB) uses AMMONIA to produce NITRITE Nitrobacter bacteria (NOB) uses NITRITE to produce NITRATE

Reactions happen in biofilm

Naturally occurring Decomposition

• f chloramines

AMMONIA Added

NITRATE BUILD UP

NITRATE (NO3

• )

NITRITE (NO2

• )

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Nitrification is an imbalance

 There is a balance between how fast the

chloramines can kill (“inactivate”) the bacteria and how fast the bacteria can regrow.

 Nitrification is a problem when that

balance shifts to where the bacteria are eating ammonia and growing too fast for the monochloramines to kill all of them.

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Comparison of a Utility's

• perations during normal

and nitrification events.

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NAP Workshops A Nitrification Action Plan is like a Monitoring Plan

 It includes

• 1. A sample site map,
• 2. Sample schedules,
• 3. Analytical methods,
• 4. Site-specific goals, baselines, and trigger

levels,

• 5. Actions, and
• 6. Communication strategies.

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DAM Workshops

 This DAM includes a workshop for each

element of the DAM.

– As you go through each workshop, note follow-up actions that you will need to complete later.

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Workshop 1. NAP sites

 NAP sample sites:

– Represent sources, entry points, average and high water age in all pressure planes. – Can be the same as coliform sites

 But they don’t have to be.

– Critical control points

 “A point where control can be applied and is

essential to prevent or eliminate nitrification”

– EG: Before booster chloramination

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Workshop 2. Monitoring frequency

 NAP monitoring must be done weekly,

– May be done more frequently.

 Small systems, <750 people or 250 cnx.

– Monitor monochloramine and ammonia with every weekly total chlorine sample.

 Large systems, select sites at low,

average and high water age for weekly sampling.

• 3a. Sample collection

method

 Water representing the main

– Not stagnant water in the sample line

 Use the calculated flush time (CFT)

– Based on volume and flow – Flush just two (2) pipe-volumes – Don’t overflush

 Consider building a hydrant and tap

sampler

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• 3b. Analytical methods

 Total chlorine:

– Use EPA approved method

 Monochloramine, ammonia, nitrite, nitrate

– EPA does not have approved methods. – Achieve the required accuracy

 Document on the List of Analytical

Methods (LAM)

– Attach to Monitoring Plan

• 4. Goals/baselines and

trigger levels

 Nitrification is controlled by defining

what “normal” is and looking for trends that are “abnormal.”

– Therefore, initial data must be analyzed to define normal levels, – And additional data must be analyzed or hypothetical levels must be projected for levels that are a concern: trigger levels.

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Comparison of a Utility's

• perations during normal

and nitrification events. Workshop 5. Actions!

 Preventive action:

– Routine operating conditions

 Do this even when your levels are ok

 Corrective: Trigger 1

– Intermediate--Do this when levels are not quite ok

 Corrective: Trigger 2

– Do this when nitrification is bad

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Most preventive and corrective actions overlap

 Preventive and corrective actions:

– Verify results. – Flush. – Dose chlorine and ammonia correctly. – Minimize water age.

 Operational corrective action:

– Temporary conversion to free chlorine.

Workshop 6. Communication strategies

 Make sure that all communication

pathways are robust:

– Standard operating procedures – Chain of command for action approval – Notification of other PWSs, customers, TCEQ as needed.

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Example: Nitrification Action Plan

Nitrification Action Plan Example

Chloramine-Effectiveness Sample Suite Site Chemical Goal Yellow Flag Red Flag Trigger Actions Trigger Actions Entry Point Total / Mono 4.2 3.5 1) Verify results 2) Check and adjust dose Till levels return to normal 3.0 1) Verify results 2) Adjust dose Till levels return to normal Free ammonia 0.01 0.2 0.3 Average Water Age Total / Mono 2.0 1.5 1) Verify results 2) Measure nitrite and nitrate 3) Adjust dose 4) Identify affected area (check upstream and downstream) 5) Flush area 6) Flush dead ends Till levels return to normal 1.0 1) Verify results 2) Measure nitrite and nitrate 3) Adjust dose 4) Identify affected area (check upstream and downstream) 5) Flush area 6) Flush dead ends 7) Convert to Free Chlorine Till levels return to normal Free ammonia 0.3 +/- 20% +/- 50% High Water Age Total / Mono 1.0 0.7 0.5 Free ammonia 0.5 +/- 20% +/- 50% Nitrite/Nitrate Site Chemical Baseline Yellow Flag Red Flag Trigger Actions Trigger Actions Entry Point Nitrite 0.025 +/- 20% (<0.02 or >0.03) 1) Verify results 2) Identify source changes IF confirmed-modify BL 3) Identify area, 4) Flush area Till levels return to normal +/- 50% (<0.013 or >0.05) 1) Verify results 2) Identify affected area 3) Flush 4) Perform free chlorine burn Till levels return to normal Nitrate 1.5 >1.7 >2.0 Source water(s) Nitrite 0.025 +/- 20% (<0.02 or >0.03) +/- 50% (<0.013 or >0.05) Nitrate 1.5 >1.7 >2.0 Blended water Nitrite 0.025 +/- 20% (<0.02 or >0.03) +/- 50% (<0.013 or >0.05) Nitrate 1.5 >1.7 >2.0

Take-home Message

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Take-home Message

 Chloramines are an important tool.

– They can help maintain residuals, and – Avoid unwanted disinfection byproducts.

 Nitrification is a potential risk of

chloramination.

 Nitrification can be detected and

controlled using a Nitrification Action Plan