ANALYSIS OF NITRATES AND NITRITES IN SOME WATER AND FACTORY EFFLUENT SAMPLES FROM SOME CITIES IN SWAZILAND

Abstract

The levels of nitrates and nitrites in drinking water, river water and factory effluents from three major cities in Swaziland were determined by a pre-calibrated colorimetric method. The pooled mean concentration range for the nitrates in the river water samples is 1.74±0.13 – 115±3.27 mg/L as NO₃–N and for nitrites is 1.50 ± 1.70 – 2.90 ± 2.77 mg/L as NO₂–N. For the factory effluents, nitrate levels varied between 72.3 ± 6.81 mg/L and 75.7 ± 3.21 mg/L, giving a pooled mean of 74.0 ± 3.76 mg/L, while the concentration range for nitrites is 0.16 ± 0.02 – 0.21 ± 0.07 mg/L, giving a pooled mean of 0.18 ± 0.03 mg/L as NO₂–N. Nitrate levels in the drinking water samples ranged between 0.70 ± 0.10 – 1.6 ± 0.07 mg/L, giving a pooled mean concentration of 1.3 ± 0.26 mg/L as NO₃–N, while levels of the nitrites vary from 1.1 x 10^-3 ± 1.2 x 10^-4 – 7.93 x 10^-3 ± 8.1 x 10-4 mg/L, yielding a pooled mean of 3.4 x 10-3 ± 3.0 x 10-4 mg/L as NO₂–N. The observed mean as well as the highest single-point values for both nitrates and nitrites in drinking water are well below WHO\'s maximum acceptable concentration (MAC), of 10.0 mg/L nitrate as NO₃–N and 3.0 mg/L nitrite as NO₂–N. However, the levels of both species in the river water and factory effluents are high enough to necessitate the monitoring of their respective levels.



KEY WORDS: Leaching, Runoff, Methemoglobinemia, Nitrate fertilizer, Nitrogenous-waste, Water quality assessment


Bull. Chem. Soc. Ethiop. 2005, 19(1), 35-44.