The occurrence of nitrogen compounds in well water

Abstract

INTRODUCTION: Nitrogen compounds in drinking waters have been related to groundwater contamination and inadequate sanitary conditions. Nitrite and nitrate are etiologic agents of methemoglobinemia. In acid solution, nitrous acid formed from nitrite can react with secondary amines to form carcinogenic nitrosamines. The survey of ammoniacal and albuminoid nitrogen, nitrite and nitrate in groundwater supplies as regards the extent of the contamination they cause and discussion of the drinking water regulation regarding nitrogen compounds. MATERIAL AND METHOD: Samples collected predominantly in the Metropolitan Region of S. Paulo City was analysed for nitrogen compounds using colorimetric methods: N-NH3 and N-albuminoid by the Nessler method, nitrite by diazoted sulfanilamide with N-(1-naphthyl)-ethylenediamine, and nitrate by reaction with phenoldisulphonic acid. RESULTS: Federal and S. Paulo State drinking water regulations, respectively, Portaria 36/90 and Decreto nº 12.486, were applied to interpret the results obtained. Of the 607 samples analysed, 15% of them had at least one of the concentrations of nitrogen compounds exceeding the maximum contaminant level (MCL) of the S. Paulo State Regulation. Otherwise, as regards the Federal Regulation, only 4% of the samples exceeded the MCL requirement for nitrate. CONCLUSION: In federal drinking water regulation only MCL for nitrate is reported. Otherwise, S. Paulo State regulation requirements report MCLs for all the compounds that have been analysed in this work. The observed results showed that concentrations of ammonia and albuminoid nitrogen, and nitrite, as well as nitrate, gave rise to water of inadequate quality, further they may have adverse effects on human health. The inclusion of nitrogen compounds other than nitrate in federal regulation is recommended.