Nitrate content of Malta and Gozo tapwater

Abstract

The aim of the present investigation was to determine the quality of tapwater, with respect to nitrate content, as it actually reaches the consumer and how this quality varies for consumers living in different areas of the Maltese Islands. Nitrate in drinking water originates from contaminated groundwaters since reverse osmosis (RO) water is nitratefree. Aquifers receive nitrates mainly from agricultural fertilizers but possibly also from sewage water and other sources. Nitrate is a health hazard and is known to cause infantile methaemoglobinaemia in newborns and is suspected to increase the incidence of stomach cancer in adults. The WHO guideline value for nitrate is 45 ppm.

Tapwater from various localities in Malta and Gozo were analyzed during the period July - October 1991. The results showed that nitrate concentrations varied dramatically from barely detectable in certain localities to very high values, >100 ppm, in certain areas in central Malta and in parts of Gozo. In view of the toxicity of nitrates, the present situation warrants a remedy without delay. A solution to the problem would involve a more rigorous mixing programme of the two water types, i.e. RO and ground supplies, prior to distribution to consumers. An alternative or parallel approach would involve the use of an RO plant for the purification of high nitrate groundwater. The energy demand of such a plant would be much lower than that of RO plants running on seawater. Such a solution could be especially useful for Gozo, which in the meantime, should have its nitrate values reduced by being provided with adequate blending facilities and with RO water from the Cirkewwa plant.