Innovative drinking water treatment

In innovation development PWN attaches great importance to high drinking water quality which, among other factors, is a function of a high level of biological stability with a limited regrowth of undesirable microorganisms in the distribution network. Besides such regrowth, what is also important in preventing possible impacts on health is the absence of mutagenic activity in the supplied drinking water. Previous KWR research showed that the mutagenic activity can occur when medium-pressure UV processes are used.

Technology

In 2015, the current full-scale treatment process is to be gradually replaced. To achieve an optimal treatment in the new situation, the production of biologically stable drinking water has to be further characterised in the pilot treatment, and results generated from the full-scale treatment of surface water for the production of drinking water. The research into the occurrence of mutagenic activity following middle-pressure UV processes will identify the substances responsible. The identity of these substances is currently unknown. This is difficult to remedy, in part because of the large number of reaction products that can form during middle-pressure UV. Consequently, it is not possible to determine the relevance to health of the formed by-products. Because PWN applies biological process in the post-treatment, no mutagenic activity has been observed in the drinking water to which middle-pressure UV technology has been applied.

Challenge

The production of biologically stable drinking water using the new treatment concept is characterised in a pilot set-up. In addition, the research into the full-scale treatment is used to determine the extent to which the pilot treatment is predictive in this context. A determination is also made as to whether the new KWR measurement methods can be successfully applied to assess the biological stability of the drinking water produced by full-scale treatment.

In order to identify reaction products with mutagenic activity formed during middle-pressure UV treatment, artificial water, to which a known composition of natural organic matter (NOM) has been added, is subjected to UV radiation. Following the extraction of the radiated and untreated water, part of the extract is subjected to an Ames mutagenicity test. Then, on the basis of the chromatogram of an NOM solution, following separation by means of HPLC, a decision is made to separate the water extracts into eight fractions, on the basis of polarity. These fractions are each separately submitted to the Ames test and analysed using an Orbitrap MS so as to reveal, respectively, the mutagenic response and the presence of disinfection by-products

Solution

Demonstrate that PWN’s new treatment concept is suitable for the production of pure drinking water from surface water. This primarily involves an examination of:

• The impact of spent and regenerated carbon on the biological stability of drinking water in the pilot treatment with the new treatment concept at the Andijk production location.
• The biological stability of the (distributed) drinking water, produced by the new treatment concept under full-scale conditions at the Andijk production location.
• The biological stability of the (distributed) drinking water produced by the new treatment concept compared to that of water produced by conventional treatment.
• The use of KWR’s methods to determine the biological stability of drinking water produced under pilot and full-scale conditions.
• The possible identification of specific compounds responsible for a positive response in the Ames fluctuation test after UV/H₂O₂
• The relative contribution to mutagenic activity of the polar fraction (in which NOM in particular evolves), the moderately polar and the apolar fraction from water samples treated with UV/H₂O₂.
• The polarity of substances that cause the response in the Ames fluctuation test.