Recent studies have pointed out the importance of nitrogen compounds,
such as amino acids, on chlorine consumption of drinking water: chlori
ne demands of amino acids would range from 2 to 16 mol Cl2/mol of amin
o acids. Better knowledge of amino acid concentrations in water could
lead to improve water treatment and so, water quality on distribution
networks. The general objective of this study is to quantify total ami
no acids in surface waters and drinking waters. For that purpose, OPA
precolumn derivatization followed by HPLC analysis with fluorimetric d
etection was used. Natural water samples were first hydrolysed under a
cidic conditions. Amino acid analysis were carried out on raw surface
waters from three french rivers (Oise, Seine, and Marne), and on the w
ater treatment plant of Mery sur Oise (Paris, France). Analysis were p
erformed at different steps of the treatment plant: storage, flocculat
ion-sedimentation, sand filtration, interozonation, GAC filtration, po
stozonation and chlorination. The global amino acid concentration meas
ured ranged in most cases from 50 to 250 mug l-1, expressed as carbon
content (i.e. 20 to 90 mug l-1 N). Major compounds were glycine, serin
e, alanine, aspartic acid, glutamic acid, threonine and valine at conc
entrations ranging from 0.2 to 0.9 mumol l-1. Seasonal variations were
observed, with an increase of total amino acid concentrations in raw
waters at spring and summer periods. Based on our previous studies, we
can estimate chlorine consumption of treated water due to these compo
unds between 0.4 to 1 mg l-1 Cl2.