Ozonation of naphthalene sulfonic acids in aqueous solutions. Part I: elimination of COD, TOC and increase of their biodegradability

Ozonation of 11 naphthalene sulfonic acids (NSA) in the aqueous solution was studied by bubbling at 31°C at an ozone dose rate of 5.56 mg min−1 l−1. COD, TOC and BOD5 of these compounds were tested. It was found that COD and TOC can be removed effectively by ozonation as expected. More than 40% COD of compounds No. 1 (2-amino-1-NSA), No. 5 (1-hydroxy-7-amino-5-NSA), No. 6 (6-hydroxy-1-NSA), No. 8 (6-amino-1,4-naphthalene disulfonic acid) and No. 11 (1-hydroxy-6-amino-3-NSA) has been eliminated at an ozone dosage of 5.56 mg min−1 l−1 for 2 h. Although TOC removal was very different, a good biodegradability was reached for NSAs with an average ozone consumption of 3.0 mg l−1 for a TOC0 concentration of 100 mg l−1. Ozonation and biotreatment should be good alternatives for these compounds, especially after 20% TOC reduction and TOC removal were more sensitive in predicting an increase in biodegradability during ozonation, than that of COD. NSAs are similar in their behavior with reference to ozone consumption. In order to obtain a good biodegradability of NSAs at a TOC0 concentration of 100 mg l−1, an ozone consumption between 2.0 and 4.0 mg mg−1 ΔCOD is needed for this setup and 3.0 mg O3 mg−1 TOC0 requirement may be more practical in predicting the biological behavior of naphthalene compounds.