Effects of the Water Matrix on the Degradation of Micropollutants by a Photocatalytic Ceramic Membrane.

The consumption of pharmaceuticals has increased the presence of micropollutants (MPs) in the environment. The removal and degradation of pharmaceutical mixtures in different water matrices are thus of significant importance. The photocatalytic degradation of four micropollutants-diclofenac (DCF), iopamidol (INN), methylene blue (MB), and metoprolol (MTP)-have been analyzed in this study by using a photocatalytic ceramic membrane. We experimentally analyzed the degradation rate by using several water matrices by changing the feed composition of micropollutants in the mixture (from mg· L-1 to µg·L-1), adding different concentrations of inorganic compounds (NaHCO3 and NaCl), and by using tap water. A maximum degradation of 97% for DCF and MTP, and 85% for INN was observed in a micropollutants (MPs) mixture in tap water at environmentally relevant feed concentrations [1-6 µg·L-1]o; and 86% for MB in an MPs mixture [1-3 mg·L-1]o with 100 mg·L-1 of NaCl. This work provides further insights into the applicability of photocatalytic membranes and illustrates the importance of the water matrix to the photocatalytic degradation of micropollutants.

Influence of process conditions and water quality on the formation of mutagenic byproducts in UV/H2O2 processes.

UV/H2O2 processes in drinking water treatment may generate byproducts which cause an increased response in Ames fluctuation assays. As this probably involves a mixture of substances in very low concentrations, it is challenging to identify the individual byproducts. Therefore it was studied under which conditions mutagenic byproducts are formed and how this can be prevented. It was found that positive Ames fluctuation test responses only are obtained when Medium Pressure UV lamps are used, and not with Low Pressure lamps. This probably is explained by the photolysis of nitrate, which plays an important role in the formation of mutagenic byproducts. The most important parameters involved in the formation of such byproducts were demonstrated to be the nitrate concentration, the natural organic matter, the UV spectrum of the lamps, and the UV dose applied. These factors explain up to 74-87% of the Ames fluctuation test responses after UV/H2O2 drinking water treatment. By taking this into account, drinking water utilities can estimate whether UV processes applied in their case may cause the formation of mutagenic byproducts, and how to take measures to prevent it.