VARIATION OF BIODEGRADABILITY OF NITROGENOUS ORGANIC-COMPOUNDS BY OZONATION

Five nitrophenols and two synthetic dyes were ozonated to evaluate the biodegradability of reaction products from water quality parameters, and the relationship between the biodegradability and the behavior of the reaction products and of the nitrogen forms was then discussed. Biodegradability represented in terms of BOD5/TOC was observed to reach a maximum, indicating that there was an optimum condition. It was confirmed, from the comparison of the biodegradability of the target compounds with that of phenol, that the variation of biodegradability was deeply associated with the behavior of the nitrogen forms. The amount of ozone consumed required to lead to the maximum BOD5/TOC value varied with the target compounds, lying between 2.3 and 3.8 mg per mg of initial TOC for nitrophenols, and between 1.3 and 1.7 mg for synthetic dyes. From the behavior of nitrogen, it could be assumed that nitrogen in the azo group would be partly released from solution as nitrogen gas, and that nitrogen in the nitro group would remain in solution after ozonation as nitrate ion and so on.