Visual determination of nitrite and nitrate in waters by color band formation method

摘要

A spot test for aqueous nitrate and nitrite for controlling nitrogen removal performance in small-scale wastewater treatment facilities is proposed. In this method, NO_2~- ion in water samples was allowed to react with sulfanilic acid and 1-naphthol to form an anionic azo dye. The resulting colored solution was introduced onto a mini column (similar to a gas detecting tube) packed with PVC particles coated with benzyl cetyl dimethyl ammonium chloride (BCDMA) and biphenyl. The NO_2~--N concentration was determined visually by measuring the color band length (CBL) in the column. The CBL correlates linearly with nitrite concentration in the 4-20 mg-N l~(-1) range. The concentration of nitrite + nitrate was determined after reduction to nitrite with zinc. The concentration of NO_3~--N species was calculated by difference. This method was used to visually determine the concentrations of NO_2~--N and (NO_2~- + NO_3~-)-N in domestic wastewater samples with maximum suspended solid (SS) and chemical oxygen demand (COD) concentrations of 114 mg l~(-1) and 73.9 mg l~(-1), respectively.