Determination of Kjeldahl nitrogen in sewage effluents, trade effluents and sewage sludges using a copper-titanium catalyst

Studies were carried out to develop a method for determining Kjeldahl nitrogen in sewage, sludge, and industrial wastewaters, which would use reagents less environmentally unacceptable than the procedure using mercury catalyst. The performance of the digestion methods tested initially are summarized in tables, and full details are given of the procedure finally adopted, using a block digester and a copper-titanium catalyst of low toxicity. Application of the method to a solution of nicotinic acid (200 mg nitrogen per litre), gave a standard deviation of 1.6 mg nitrogen per litre and a nitrogen recovery of 95.6 per cent. The limit of detection was 0.85 mg nitrogen per litre. Results obtained by this method and by the mercury catalyst method on sewage sludge, digested sludge, and nicotinic acid are compared.