Effective catalytic removal of nitrates from drinking water: An unresolved problem?

Over the past 29 years there have been myriad research efforts into the catalytic removal of nitrates from drinking water. In this work, 147 papers published during that period have been examined from the point of view of the ability of catalysis to produce water that is suitable for human consumption as well as amenable to industrial scale-up at reasonable working conditions of temperature and residence time. After close examination of the aforementioned articles, it is evident that this methodology has fulfilled only half its aims: it is able to reduce the nitrate concentration to guideline levels for human consumption, but it inevitably produces concentrations of ammonia and nitrites that are beyond the accepted limits for safe consumption of water. It is sometimes recommended that catalysis be combined with an ancillary technique, such as adsorption, in order to eliminate the undesirable byproducts mentioned above. However, this implies resorting to extra treatment units at the industrial scale, thus making the whole treatment process more complex and expensive. Our conclusion is that the effective catalytic removal of nitrates from drinking water is a very difficult problem. (C) 2019 Elsevier Ltd. All rights reserved.