Determination of biodegradable dissolved organic carbon in waters is of particular importance for the water treatment industry. A simple method for determining biodegradable dissolved organic carbon which is applicable to surface and drinking water is proposed. It consists of sterilizing the water sample, inoculating it with autochthonous bacteria, and measuring the decrease in dissolved organic carbon concentration due to the carbon oxidization by bacteria. The detailed experimental procedure is discussed, and validation of the method is presented. The method has been used for studying river waters and for drinking water treatment plant design.

To maintain the biological stability of drinking water during distribution in large, complex networks, high standards have to be met—namely, low bacterial densities and low levels of biodegradable organic carbon. Second‐stage granular activated carbon (GAC) filtration (without regeneration of carbon) is used for this purpose at the Choisy‐le‐Roi, Paris, France, treatment plant. Effective removal of dissolved organic carbon has been observed with such filtration—mainly because of a reduction in the biodegradable organic carbon. To study the microbial processes involved in this removal, new methods based on the use of radio‐labeled tracers have been developed in order to measure the bacterial biomass and activity associated with GAC.

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A nanofiltration membrane tailor‐made to address site‐specific concerns proves capable of overcoming both variable operating conditions and inherent membrane deficiencies. At a water facility in the Paris suburbs, a prototype nanofiltration (NF) plant was used to assess NF membrane performance prior to design and construction of a large‐scale expansion to an existing plant. Prototype operation uncovered both the successes and deficiencies in membrane performance, particularly with regard to the source water supplying the plant. In response to these concerns, a new membrane was developed in partnership with the membrane manufacturer. In parallel with the prototype work conducted in France, a similar membrane assessment was carried out in England. Results from both pilot‐plant operations indicate that an NF membrane manufactured to meet site‐specific concerns can overcome variable operating conditions and treat large water flows.

A single dual-layer filter, combining sand and granular activated carbon (GAC) and maintaining the mechanisms of biological treatment, was studied in France as a possible means of achieving high-rate filtration. Initial results attest that the dual layer far outperforms a single-layer sand unit, particularly with respect to the removal of suspended solids and ammonia. Using GAC for the top layer of the double filter ensures the removal of appreciable quantities of assimilable carbon and consequently has a positive effect on final chlorination and the palatability of the water.