Occurrence of Free Amino Acids and Related Disinfection By-Products in Drinking Water Treatment Systems Zuo Tong How Kathryn Linge, Francesco Busetti & Cynthia Joll Curtin Water Quality Research Centre Curtin University, Perth, Australia

Amino Acids in Water Systems •  Organic compounds that consist of amine (-NH2) and carboxylic acid (-COOH) functional groups with a side-chain specific to each amino acid

•  Important building block for protein and organic tissues •  Amino acids account for 20-75 % of dissolved organic nitrogen

•  Algal organic matter is one of the main contributors of amino acids in natural waters

Westerhoff and Mash,2002, J. Water Supply Res Technol.Aqua Yang et. al., 2010, Water Research

Water Disinfection •  Water disinfection is the removal or inactivation of pathogens in water

•  Ensures safe drinking water •  Undesirable disinfection by-products (DBPs) can form during disinfection

•  Depending on the disinfectant (e.g. chlorine) used and the organic matter present, different DBPs can be formed

•  Example: •  Amino acids can formed odorous compounds like aldehydes and N-chloraldimines

Image taken from internet

Odorous Disinfection ByProducts DBPs

Odour threshold (µg/L)

Isobutyraldehyde

0.9

Isovaleraldehyde

0.15

2-Methylbutyraldehyde

1.25

Phenylacetaldehyde

4

Benzyl Cyanide

3

N-Chloroisobutyraldimine

0.2

N-Chloromethyl-3-butaldimine 0.25

Frezue et. al. (2006) Water Research

Taken from: http://www.talkshop.info/wildcat-aquifer/smelly-water/smelly-

Aldehydes, Nitriles and NChloraldimines •  Depending on chlorine to amino acid ratio, either only aldehydes or aldehydes, nitriles and N-chloraldimines can be formed

•  1 mole of amino acid (e.g. valine) formed 0.35 mole of aldehyde and nitrile;

Cl:AA > 2

and 0.3 mole of N-chloraldimine at Cl:AA ratio of >2 Cl:AA < 1

Project Aims —  Develop mass spectrometric based analytical methods for the detection of: 1.  Free amino acids in natural waters 2.  Organic chloramines 3.  Disinfection by-products related to amino acids

—  Occurrence study of free amino acids in source water and treated water

—  Occurrence of disinfection by-products derived from amino acids

—  Investigation of the formation and degradation pathways of organic chloramines and the reaction kinetics

Analytical Methods Analyte

Method

Free amino acids

SPE-LC-HRMS

Dissolved organic carbon

UV-persulfate oxidation

TDN

Catalytic combustionchemiluminescence

Bromide

Ion chromatography

Aldehydes, Nitriles & N-Chloraldimines

HS-SPME-GC-MS

Haloacetonitriles

HS-SPME-GC-MS

•  Only free amino acids and not total amino acids

Amino Acids & DBPs Analysed 18 Amino acids

alanine, asparagine, aspartic acid, glycine, glutamine, glutamic acid, histidine, isoleucine, leucine, lysine, methionine, proline, phenylalanine, serine, threonine, tryptophan, tyrosine, valine

4 Aldehydes

2-methylbutyraldehyde, isovaleraldehyde, phenylacetaldehyde, isobutyraldehyde

4 Nitriles

2-methylbutyronitrile, isovaleronitrile, benzyl cyanide, isobutyronitrile

3 NChloraldimines

N-chloromethyl-2-butaldimine, N-chloromethyl-3butaldimine, N-chloroisobutyraldimine

N-chloromethyl-2-butaldimine

N-chloromethyl-3-butaldimine

N-chloroisobutyraldimi

Drinking Water Treatment Plants Plant

Source

Organic matter removal process

Disinfectant

Chlorine residual (mg/L-Cl2)

DWTP 1 Groundwater

Magnetic ion exchange and alum coagulation

Chlorine

1.5

DWTP 2 Groundwater

Alum coagulation

Chlorine

2.5

DWTP 3 Surface water

Alum coagulation, sand filtration, ultrafiltration

Chlorine

2

DWTP 4 Surface water, Groundwater, Desalinated water

Dissolved air flotation Monochloramine filtration and biological activated carbon filtration

•  Plants sampled from inlet and outlet •  Samples collected during summer

4 (Combine chlorine)

Results

Source

Glutamic acid

Isoleucine

Leucine

Phenylalanine

DWTP 1

GW

4

20

5

8