Embed Size (px)
Citation preview
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
