Organic Compounds in Water and Wastewater NOM and DBPs Special - - PowerPoint PPT Presentation

CEE 697z

Organic Compounds in Water and Wastewater

NOM and DBPs Special Lecturer: Rassil El Sayess

Dave Reckhow - Organics In W & WW

Print version

Lecture #9

http://www.ecs.umass.edu/eve/research/nyc_chloramines/literature.html

Formation of Cl2-driven DBPs

2

Natural Organic Mater

Anthropogenic Chemicals

(PPCPs, Ag & industrial products)

Cl2 NaOCl NH3 Br-, I- OBr-, I3- ~90%

CO2 + Oxidized Organic Compounds

• Acids
• Aldehydes
• Ketones
• Nitrosamines

NH2Cl The non- halogenated DBPs The Halogenated DBPs

• THMs
• HAAs and other haloacids
• Haloaromatics
• N-halo compounds
• Halo-nitriles, aldehydes, nitros, etc

~10%

Other Compounds The DBP Iceberg

Halogenated Compounds Non-halogenated Compounds

ICR Compounds

50 MWDSC DBPs ~700 Known DBPs THMs, THAAs DHAAs

Stuart Krasner AWWA Susan Richardson USEPA

The Trihalomethanes (THMs)

4

Cl Cl Cl C H Br Cl Cl C H Br Cl Br C H Br Br Br C H Chloroform Bromodichloromethane Chlorodibromomethane Bromoform

1921-2010

Rook, 1974, Water

• Treat. & Exam., 23:234
• Published in Dutch journal H2O, Aug

19, 1972 issue

• Deduced that they were formed as

byproducts of chlorination

• Proposed chemical pathways

Treated Waters: TTHMs from US Surveys

5

Occurrence Assessment for the Final Stage 2 DBPR, 12/05, USEPA

5

The Haloacetic Acids (HAAs)

6

 HAA5 include the two monohaloacetic acids (MCAA & MBAA) plus

 One of the trihaloacetic acids:  And 2 of the

dihaloacetic acids

Cl Cl Cl C COOH Br Cl Cl C COOH Br Cl Br C COOH Br Br Br C COOH Trichloroacetic Bromodichloroacetic Chlorodibromoacetic Tribromoacetic Acid Acid Acid Acid

(TCAA)

Cl Cl H C COOH Br Cl C COOH Br Br H C COOH Dichloroacetic Bromochloroacetic Dibromoacetic Acid Acid Acid

(DCAA)

H

6

(DBAA)

Regulated Compounds

 THMs  HAA5  Bromate  Chlorite

 The regulated compounds are

 Common “end products” produced by almost all precursors  Chemically very stable

 This is not typical of other DBPs

DBP Precursor Materials

General Groups Specific Structures

 Bulk NOM  Hydrophobic NOM

 Acids (Fulvics & Humics)  Neutrals  Bases

 Hydrophilic NOM

 Acids, Bases, Neutrals

 Mesophilic NOM

 Acids, Bases, Neutrals

 Soluble Metabolics

 Lignin  Carbohydrates  Proteins & Amino Acids  Terpenoids  Fatty Acids  Tannins  Anthropogenics

 Ranitidine

DBP Data - Availability

 Based on precursors

 Bulk NOM: most data, from raw & treated waters  NOM Fractions: some data  Specific Structures: far less data

 Based on type of DBP

 Regulated compounds (THMs & HAAs)

 Extensive Data, especially for bulk NOM

 Common unregulated compounds

 Moderate level, especially from ICR and selected “studies”

 Emerging unregulated compounds

 Very little data

10 Time (hrs)

20 40 60 80 100 120 140 160 300 350

TOX Concentration (µg/L)

100 200 300 400 500 600 700 800 900 1000 1100 1200 1300

THM, HAA Concentration (µg/L)

100 200 300 400 500 600

TOX TCAA TTHM DCAA

20 mg/L chlorine dose pH 7.0 20oC

(from: Reckhow & Singer, 1984)

Fulvic Acid

Some Common Unregulated DBPs

11

 Many decrease with

time

 Degradation  Chemical  Biological

 Not shown

Time (hrs)

20 40 60 80 100 120 140 160

Concentration (µg/L)

2 4 6 8 10

DCAN 1,1,1-TCP Chloropicrin 1,1-DCP

Chlorinated Raw Drinking Water from New Jersey (MacNeill's UMass thesis, 1994)

Model Compound Studies

 Model compounds

 Synthetically prepared in the lab: water that has been spiked

with certain compounds

 Most have been used to assess formation of regulated

DBPs (THMs & HAAs)

 Some have been conducted to find new DBPs and

especially intermediates formed along the way to the final byproducts

Lignin: Halobenzoquinones (HBQs)

13

 Many pathways

 Plants to HQs

 Toxicity

 HQs are known to be reactive and damaging to DNA  Postulated to be bladder carcinogen of high potency

Bull et al., 2006

O O H

Cl

OH H O O H Cl Cl O O HCl O O H H O O H H Cl Cl Cl Cl

4 HOCl

Cl Cl Cl Cl Cl Cl Cl Cl Cl Cl Cl

5

Lignin?

Halobenzoquinones (cont.)

14

 Identified following QSAR deductive reasoning

 SPE - LC/MS/MS method: Zhao et al., 2010

 Little occurrence data:

 U Alberta: 7 samples in 2 publications

 Dichloro (DCBQ): 14 ng/L median (165 ng/L max)  Others much lower

 UMass: several dozen samples - unpublished

 Dichloro: 306 ng/L high value

Formation Potential

Dave Reckhow - Organics In W & WW

 Experiments designed to maximize exposure of water to

chlorine (in this case) under optimal conditions and measure the concentration of DBP for a specified duration

 Disinfection by-product formation potential (DBP-FM):

72 hr, 20 mg/L Cl2 dose, pH 7, 20C

 Simulated distribution system (SDS) test: 24 hr, 4 mg/L

Cl2 dose, 20C and pH 7

THM-FP

16

Cumulative Frequency

0.0 0.2 0.4 0.6 0.8 1.0

Specific THMFP (µg/mg-C)

20 40 60 80 100 120

Specific THM-SDS (µg/mg-C)

10 20 30 40 50 60 Surface Waters Groundwaters

From: Reckhow et al., 2006 AWWARF report (in press)

16

From: Reckhow et al., 2007 WRF Report #91186 Median Value

45 µg-THM/mg-C Formation Potential conditions: 72 hrs, 20 mg/L Cl2, pH 7, 20C

FP and SDS for NOM Fractions

17

 Cumulative Frequency Plot for THM Precursor

Content in Major RW Fractions

Cumulative Frequency

0.0 0.2 0.4 0.6 0.8 1.0

Specific THMFP (µg/mg-C)

20 40 60 80 100 120

Specific THM-SDS (µg/mg-C)

10 20 30 40 50 60

Pre-exponential Term (a)

0.0 0.1 0.2 0.3 0.4 0.5 0.6 Philic Phobic Trans

Untreated Waters Only

Formation Potentials of NOM Fractions

18

Neutrals

TTHMFP (µg/mg-C)

10 20 30 40 50 60 70

Hydrophobic

Bases Acids Neutrals Bases Weak Acids Humic Acid Fulvic Acid

Hydrophilic

18

TOX Formation

David Reckhow

HOCl NOM Br I HOBr HOI NOM NOM Cl-DBPs Br-DBPs I-DBPs TOX Other disinfectants: NH2Cl, O3, ClO2 TOX=TOCl + TOBr + TOI

From: Guanghui Hua; 2004 WQTC

What do we know so far?

 Approximately 50% of the TOX formed by drinking water

chlorination is not accounted for concern about the identity and concentrations of DBPs

 Not feasible to account for each and every compound that

might be formed in disinfected water

 TOX: A surrogate measure for organically-bound halogenated

DBPs in a disinfected water sample.

 Comparing the TOX vales with the halides attributed to the

identified DBPs: allow for the estimation of the unidentified TOX

 TOX analyzers: used to quantify amounts of organically-bound

chlorine, bromine and iodine in raw and disinfected water samples

TOX: Known & Unknown

Trihalomethanes 20% Sum of 5 Haloacetic Acids 10% Bromochloroacetic Acid 3% Unknown Organic Halogen 64% Chloral Hydrate 1% Haloacetonitriles 2% Haloketones Chloropicrin

21

Data from the Mills Plant (CA) August 1997 (courtesy of Stuart Krasner)

Regulated DBPs But, the Bad Stuff is probably somewhere here?

Unknown TOX TTHMs

Cyto- and Geno-Toxicity of DBP classes

Occurrence, genotoxicity, and carcinogenicity of regulated and emerging disinfection by-products in drinking water: A review and roadmap for research . (Richardson et al., 2007)

C- and N-based DBPs

Occurrence, genotoxicity, and carcinogenicity of regulated and emerging disinfection by-products in drinking water: A review and roadmap for research . (Richardson et al., 2007)

Final disinfectant

Dave Reckhow - Organics In W & WW

 Drinking water treatment plants usually employ a

chemical as a final disinfectant

 Common oxidative chemicals

 Free chlorine  Chloramines  Chlorine dioxide  Manganese oxide  Potassium permanganate

Use of chloramine vs chlorine as final disinfectant

 Less formation of

regulated DBPs

 THMs & HAAs

 Hydrolysis and

• xidation is slow

which minimizes further oxidation to TXAA

 Dihalo products, but

little trihalo

R'' C CCl2 O C R' O R'' C CCl2 O C OH O C OH O Cl2HC C OH O Cl3C CHCl3

NOM

R'' C CHCl2 O R'' C CCl3 O

Oxidation & Substitution (chlorine & chloramines) Hydrolysis Hydrolysis Substitution (free chlorine only) Hydrolysis Oxidative Hydrolysis

DCAA TCAA THM

Hydrolysis & Oxidation

Slow

DBP Formation Reactivities of NOM Fractions of a Low-Humic Water” by Hwang, Sclimenti & Krasner

Normalized per micromole of DOC

Use of chloramine vs chlorine as final disinfectant

DBP Formation Reactivities of NOM Fractions of a Low-Humic Water” by Hwang, Sclimenti & Krasner

Normalized per micromole of DOC

Use of chloramine vs chlorine as final disinfectant

Final Thought

 US federal and state environmental agencies still only regulate

four THMs and five HAAs (none of which include iodinated species) in addition to bromate and chlorite.

 How to change that?  Literature is lacking in studies conducted on treated drinking

waters that are not spiked with model compounds

 attention should be put in that direction.

 Focus on quantifying more harmful compounds or TOI/TOBr

in drinking water

 With the recent advances in analytical techniques, it is possible

to have data that will supplement existing and ongoing epidemiological/toxicological evidence.

 Once enough concrete evidence is generated, regulatory

agencies will have no choice but to improve on current regulations.

Dave Reckhow - Organics In W & WW

 To next lecture