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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 2

Outline of Presentation

Chloramination

Nitrification

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4

Chloramines

O

H Cl Cl

H

O

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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Cl Cl O

-

H

Cl N H

N H

H H

H

N H

H

Yuefeng Xie’s Bar Theory of 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… 6

Cl

N

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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8

To

tal

Ch

lori

ne

Sp

ecie

s

Cl2:N mass ratio 5:1 7.6:1

Breakpoint curve

Free

Ammonia

Mono-

chloramine

Dichloramine

Trichloramine

Free

Chlorine

Total Chlorine =

The sum of the

active chlorine

species

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Ch

lori

ne

Re

sid

ua

ls:

T

ota

l a

nd

Sp

ecie

s (

mg

/L)

Cl2:NH3-N (Chlorine to Ammonia-Nitrogen mass ratio)

Breakpoint curve: Question

Free Ammonia

Mono-chloramine

Free Chlorine

What CAN you measure?

– Using normal equipment

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Nitrification

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-

Nitrification in the environment

PLANT

FERTILIZER

AMMONIA

Wastewater

effluent

Plant

remnants

Fish excreta

and urine

NITRATE

BUILD UP

Gases

ANAEROBIC

BACTERIA

NITRITE (NO2-)

Nitrosomonas bacteria

(AOB) uses up ammonia

and makes NITRITE

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

of chloramines

AMMONIA

Added

NITRATE

BUILD

UP

NITRATE (NO3-) NITRITE (NO2

-)

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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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.

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

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

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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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

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.

Example: Nitrification Action Plan

Trigger Actions Trigger Actions

Total /

Mono 4.0 3.5 3.0

Ammonia 0.1 0.2 0.3Total /

Mono 2.0 1.5 1.0

Ammonia 0.5 +/- 20% +/- 50%

Total /

Mono 1.0 0.7 0.5

Ammonia 0.9 +/- 20% +/- 50%

Trigger Actions Trigger Actions

Nitrite 1.23 > 1.5 > 2

Nitrate 0.12 +/- 20% +/- 50%

Entry

Point

1) Verify results

2) Check and adjust

dose

1) Verify results

2) Adjust dose

Average

Water Age

All Sites

1) Verify results

2) Identify source changes

IF confirmed-modify BL

3) Identify area,

4) Flush area

Till levels return to normal

1) Verify results

2) Identify affected area

3) Flush

4) Perform free chlorine burn

Till levels return to normal

Site Chemical BaselineYellow Flag Red Flag

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) 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

Far

Reaches

Nitrite/Nitrate

Nitrification Action Plan Example

Site Chemical GoalYellow Flag Red Flag

Chloramine-Effectiveness Sample Suite

Take-home Message

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

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Thanks! Any Questions?