Two bioassay procédures are proposed for determining biodégradable dissolved organic carbon (BDOC) in waters. Both involves stérile filtration of the sample, reinoculation with a natural assemblage of bacteria from the same origin as the sample, and incubation for at least 10 days in the dark at 20°C. In the first procédure, dissolved organic carbon (DOC) is followed, until a plateau is reached and the différence between initial and final DOC is taken as a measure of BDOC. In the second procédure, bacterial biomass and mortality rate are followed and the integrated flux of mortality during the incubation period is calculated and divided by the growth yield to give an estimate of BDOC. Both procédures provide closely concordant results. An example of application to the study of ozonation and biological activated carbon filtration in drinking water treatment is presented.

Enhanced biological phosphorus removal from wastewater by means of microorganisms found in activated sludge has for the past few years been the subject of much research and it is now commonly recognized that an activated sludge system must include alternating anaerobic-aerobic periods. The present article covers biochemical aspects of this phenomenon using a phosphorus removing biomass obtained in a laboratory-scale pilot with alternating phases and a synthetic substrate feed. The percentage of phosphorus obtained in the pilot sludge was four times greater than that of a conventional sludge plant. By exposing the same biomass to different conditions and using 31P Nuclear Magnetic Resonance, we were able to accurately pin-point the various forms of phosphorus found within cells and follow their development during the course of alternating phases. The following results were obtained:the transformation of phosphorus in its inorganic to polyphosphate form depends on the medium's level of oxygenation,the presence of nitrates disturbs the anaerobic period but does not affect phosphorus uptake in the aerated period.Continuous nitrate addition alters biomass behaviour in the anaerobic phase, which loses the capacity to release phosphorus,copper at a concentration of over 1 mg Cu2+/1 inhibits phosphorus uptake in the aerated phase. Various microbiological analyses made on the pilot biomass isolated conventional bacteria found in activated sludge.

The identification of certain organic compounds in drinking water has led water treatment specialists to be increasingly concerned about the eventual risks of such pollutants to the health of consumers. Our experiments focused on the role of ozone and granular activated carbon in removing mutagenic compounds and precursors that become toxic after chlorination. We found that if a sufficient dose of ozone is applied, its use does not lead to the creation of mutagenic compounds in drinking water and can even eliminate the initial mutagenicity of the water. The formation of new mutagenic compounds seems to be induced by ozonation that is too weak, although these mutagens can be removed by GAC filtration. Ozone used with activated carbon can be one of the best means for eliminating the compounds contributing to the mutagenicity of water. A combined treatment of ozone and activated carbon also decreases the chlorine consumption of the treated water and consequently reduces the formation of chlorinated organic compounds. *Compagnie Gen6rale des Eaux, 52, rue d'Anjou

The identification of certain organic compounds in drinking water has led water treatment specialists to be increasingly concerned about the eventual risks of such pollutants to the health of consumers. Our experiments focused on the role of ozone and granular activated carbon in removing mutagenic compounds and precursors that become toxic after chlorination. We found that if a sufficient dose of ozone is applied, its use does not lead to the creation of mutagenic compounds in drinking water and can even eliminate the initial mutagenicity of the water. The formation of new mutagenic compounds seems to be induced by ozonation that is too weak, although these mutagens can be removed by GAC filtration. Ozone used with activated carbon can be one of the best means for eliminating the compounds contributing to the mutagenicity of water. A combined treatment of ozone and activated carbon also decreases the chlorine consumption of the treated water and consequently reduces the formation of chlorinated organic compounds.