Effect of disinfection upon dissolved organic carbon (DOC) in wastewater: bacterial bioassays

Quantitative and qualitative changes in organic matter content of wastewate r effluents attributable to chlorination and ozonation have been analysed u sing bioassays as well as organic carbon direct measures. Bioassays were ca rried out using the bacterial populations of wastewater and two Escherichia coli strains as test micro-organisms. Our results indicate that pure strai ns present some advantages over indigenous bacteria. Although wastewater ba cterial populations are better adapted to growth in wastewater, E. coli str ains are more sensitive to changes in dissolved organic carbon (DOC) conten t. Moreover, the use of pure cultures allows estimation of the portion of D OC which can be converted in cell biomass, the assimilable organic carbon ( AOC). Finally, the results obtained using prototrophic and the auxotrophic strains of E. coli suggested that ozonation alters the amino acid compositi on of wastewater while chlorination does not change the quantity nor the qu ality of the DOC present in effluents.