Modelling of the release of organic compounds from polyethylene pipes to water

The use of polyethylene pipes in the distribution network causes contamination of the drinking water. The contaminants are a mixture of phenols, quinones, antioxidants and short polyethylene chains that in general have a functional polar oxygen group. With the use of the film-layer theory and a mass balance for a pipe, an equation is derived to compute the outlet concentration from a given pipe. The equation indicates that if the water in a pipe has a turbulent flow, the water becomes significantly more contaminated by the migrants, compared to water with a laminar flow. The maximum concentration of contaminants is predictable, and is equal to the product of the migrants' concentration in the polymer and its partition coefficient at the polymer and water interface. E.g. the maximum obtainable concentration of a stabilizer, as Irganox^® 1010, in drinking water exposed to PE pipes used in Denmark is between 0.2 and 0.3 mg/L if no reaction of the added antioxidant has taken place in the pipe extrusion step.