Natural organic matter (NOM) - precursoe of undesirable compound in drinking water

Chlorine is a common disinfection agent used in the natural water supplies treatment in order to
ensure the microbiological safety of drinking water. At the same time, chlorine is used as oxidant
agent for removal of oxidable pollutants from groundwater, especially for ammonium ions. The
high doses of chlorine imposed by ammonium break point chlorination process (Cl2:NH4+ = 8
÷15:1) generate also chlorinated by-products such as trihalomethans (THMs) and haloacetic
acids (HAAs) with potential carcinogenic effects. The brominated species were suspected to be
much stronger carcinogens and mutagens than their chloride – containing analogues. The
reaction between chlorine and natural organic matter (NOM), which contain substantial amount
of humic substances (HS) and also the THMs concentration level, are affected by several factors
as: pH, temperature, dissolved organic carbon (DOC), bromide concentrations, chlorine dose,
contact time. The present paper has as main objective the evaluation of halogenation effect on
THMs formation and upon evolution of some indicators of NOM quality / reactivity (A254,
SUVA) for three groundwater sources with different pollution degrees (DOC = 2 ÷ 4,5 mgC/l,
NH4+ = 1,6 ÷ 10mg/l, Br - = 0,1 – 1,1 mg/l).