nitrification inhibition at a large advanced wwtp what is...

Nitrification Inhibition at a Large Advanced WWTP

What is this Stuff!!??

2014 CIPCA Fall Conference

Greg Farmer, CWP Process Specialist Littleton / Englewood WWTP

The Littleton / Englewood WWTP

• 50 mgd TF/SC Plant

▫ 22 mgd Average Flow

• Post Nitrification

▫ Nitrifying Trickle Filters (NTF)

• Post Denitrification

▫ Deep Bed Denitrification Filters

The Problem

• Periodic unexplainable spikes in final effluent ammonia

• Treatment back to normal on following day

Presentation Overview

• Problem Identification

• Inhibition Confirmation

• Source Tracking

• Substance Identification

• Source Identification

Problem Identification

Daily Final Effluent Ammonia 2009 - 2014

Potential Causes

• Internal recycle stream? ▫ Centrate return

• Sampling problem?

• Lab error?

• Equipment problems?

• Something coming into the plant?

• No high ammonia loadings to plant

• No abnormal in house return streams

• Final effluent BOD, TSS, Fecal coliform unaffected

• Normal Alkalinity

• Not septage related

Process Schematic and Instrumentation

Real Time Analysis and Information

• Located downstream of nitrification process

• Performs nitrate and ammonia analysis every 25 minutes

Typical Events

Nitrification Inhibition Event - Oct 8, 2012(Denitrification Influent)

10/7

/12 0

:00

10/7

/12 3

:00

10/7

/12 6

:00

10/7

/12 9

:00

10/7

/12 1

2:0

0

10/7

/12 1

5:0

0

10/7

/12 1

8:0

0

10/7

/12 2

1:0

0

10/8

/12 0

:00

10/8

/12 3

:00

10/8

/12 6

:00

10/8

/12 9

:00

10/8

/12 1

2:0

0

10/8

/12 1

5:0

0

10/8

/12 1

8:0

0

10/8

/12 2

1:0

0

10/9

/12 0

:00

10/9

/12 3

:00

10/9

/12 6

:00

10/9

/12 9

:00

10/9

/12 1

2:0

0

10/9

/12 1

5:0

0

10/9

/12 1

8:0

0

10/9

/12 2

1:0

0

10/1

0/1

2 0

:00

Date Time

0

2

4

6

8

10

12

14

16

18

20

22

24

26

Nit

rate

/Am

mo

nia

(N

)

Ammonia

Nitrate

Really Weak Event

Weak Event

Nitrification Inhibition Event - Jan 28, 2013(Denitrification Influent)

1/2

8/1

3 0

:00

1/2

8/1

3 3

:00

1/2

8/1

3 6

:00

1/2

8/1

3 9

:00

1/2

8/1

3 1

2:0

0

1/2

8/1

3 1

5:0

0

1/2

8/1

3 1

8:0

0

1/2

8/1

3 2

1:0

0

1/2

9/1

3 0

:00

1/2

9/1

3 3

:00

1/2

9/1

3 6

:00

1/2

9/1

3 9

:00

1/2

9/1

3 1

2:0

0

1/2

9/1

3 1

5:0

0

1/2

9/1

3 1

8:0

0

1/2

9/1

3 2

1:0

0

1/3

0/1

3 0

:00

Date Time

0

2

4

6

8

10

12

14

16

18

20

22

24

26

Am

mo

nia

/Nit

rate

(N

) m

g/L

Ammonia

Nitrate

Moderate Event

Strong Event

Inhibition Confirmation

Effluent Sampling

To confirm the presence of an inhibitory substance

• Samples sent to outside lab to perform nitrification inhibition testing

• Save last 2 days effluent composite sample

• If event occurs, day of, and 2 days prior to event samples are sent out.

Effluent Inhibition Test Results

8/18 OK - 8/19 OK - 8/20 Event 8/18 OK – 8/19 OK - 8/20 Inhibitory

Source Tracking

Temporal Distribution

Frequency of Events

• Most Popular Days ▫ Monday 2 ▫ Tuesday 4 ▫ Wednesday 5 ▫ Thursday 6 ▫ Friday 2 ▫ Saturday 4 ▫ Sunday 0

• Most Popular Years ▫ 2007 4 ▫ 2008 7 ▫ 2009 4 ▫ 2010 6 ▫ 2011 2

• 21 Events - 2007 to 2011

• Days Between Events ▫ Average – 61 days

▫ Minimum – 6 days

▫ Maximum – 169 days

▫ Mean – 44 days

• Most Popular Months ▫ March – 5 events

▫ Jan – 4 events

▫ Feb and Aug – 3 events

▫ July – 2 events

▫ Remaining seven months – 1 event each

Influent Sampling

To narrow down the source; • Set Up additional auto

samplers at each influent (Littleton and Englewood)

• Sequential samples collected Thurs, Fri, & Sat (1:00-9:00 pm)

• Samples dumped if no event

• Samples analyzed if there is an event

Influent Sample Analysis

• Influent ▫ Both Englewood and Littleton samples

tested for nitrification inhibition

▫ Testing confirmed Littleton sample as source (Repeated for 3 events)

Influent Inhibition

Test Results

Service Area Investigation

Searching for an Unknown Substance

• Pretreatment Division Gets Involved

• Collection System Sampling Begins

• Samples Collected Every Thur, Fri, Sat

• Wait for an “event”

Littleton/Englewood Service Area

Littleton Service Area

Englewood Lines

Littleton Lines

3 Large Industrial Pockets

4

6

5

2 Close Industrial Pockets

Wadsw

ort

h

Kip

ling

Belleview

2

1

Sampling

Locations

Isolating Industrial Flow – GIS Tracing

6

Location 4

Substance Identification

What it’s Not

• Chemical Scan – Negative

• Organic Chemical Scan – Negative

• Cyanide

• Phenol

• Xylene

• EPA 625 (Acid/Base/Neutral Organics)

• EPA 624 (Volatile Organics

• EPA 628 (Pesticides)

• Metals - Negative

• Toxicity testing (Chronic & Acute WET, MicroTox) - Negative

• Quaternary Ammonium Compounds (QAC) - Negative

The “agent” causing the toxicity is relatively stable (still present 4+ weeks after initial toxicity testing; samples stored at room temperature).

Effort to Remove Substance

• Treatment to capture or remove agent – All Negative • Activated Carbon

• Silica Gel

• Diatomaceous Earth

• Filtration (0.45 um)

• UV

• Resins (Anionic and Cationic)

Literature & Other Searches

• Nitrification Inhibitory Chemicals

• Agriculture sources

• Analytical Methods

• Toxicity in general

• Microbiology

• Cellular Biochemistry

• Presented at Conferences

• Queried Universities

• Contract Laboratories

• Consultants

• Anybody who’d listen ……..

Possible Nitrification Inhibitors

• pH, DO, Temp, Flow

• Hypochlorite, etc.

• Amines, etc.

• Thioureas

• Fatty Acids

• Biocides, antibiotics, personal care products, etc.

• Surfactants, detergents, etc.

• Metals

• High BOD

• High Nitrite

• Halogenated solvents

…. we use allyl thiourea to measure recovery when we measure thiourea Using a method we developed using lC – MS - MS …. lets see what we can see ….

Someone Listened

Someone Listened

• Vic Hahn from Metro mentioned to Phil that he developed a procedure to test for thiurea, using allyl thiorurea, a known inhibitor and on our list of suspects

• L/E still had some sample remaining from the last inhibition event.

• Sample sent to Metro

• Tested positive for thiourea

NI Event October 1, 2013

• Organic Chemical Analysis

Raw Spectra Comparison

LC-MS-MS

Results: Thiourea • October 2 Sample - 7 ug/L (Normal)

• October 1 Sample - 52 ug/L (Inhibited)

… as luck would have it ….

… another inhibition event….

Results: Thiourea • October 31 Sample - 8 ug/L (Normal)

• October 30 Sample - 76 ug/L (Inhibited)

In House Confirmation

• Thiourea (~100ug/L) added to NTF water

Nitrification Inhibition Events 1-19-14, 1-24-14 and 2-19-14

Nitrification Inhibition Event 2-19-14

Nitrification Inhibition Event 2-19-2014 With Thiourea Data

Thiourea Levels of Last Five Events

Thiourea Uses

• Production of flame retardant resins

• Used in light-sensitive photocopy paper and almost all other types of copy paper

• Used for solder conditioning in circuit board manufacturing

Source Identification

Source Identification

• Thiourea known to be used in manufacturing of circuit boards

• Two circuit board Manufactures located in Littleton Service area

• Both used thiourea and discharged to sanitary sewer

• One discharged diluted rinse tank containing thiourea

• One discharges high strength concentrated dip tank ▫ And they kept a log of these discharges

Viasystems events vs LE Denit Inhibition events

Circuit Board Manufacturers

• All discharges of thiourea immediately prohibited ▫ Treatment options explored

• Concentrated batch tank contents (Board Brite II)no longer discharged

• Rinse tanks (ACL 634M) discharged over longer period of time.

• No inhibition events have occurred since

Isolating Industrial Flow – GIS Tracing

6

Location 4

X

Questions?

gfarmer@englewoodgov.org

Philip A. Russell - russell@englewoodgov.org