Partial Oxidation of Hydrolysed and Unhydrolysed Textile Azo Dyes by Ozone and the Effect on Biodegradability

Ozonation of acid yellow 17 dye in a semi-batch bubble column

“…Such results indicate that the wastewater biodegradability increased with an increase in ozonation time. These data suggest that partial oxidation of the dye occurred, not total mineralization, resulting in lower molecular weight compounds that were more amenable to microbial oxidation [6,14,15,18,19]. These results are consistent with our previous observations from experiments conducted in an unbuffered system that showed the pH drop throughout the ozonation process indicating that smaller, more biodegradable, organic acids are being produced.…”

Removal of COD and color from hydrolyzed textile azo dye by combined ozonation and biological treatment

“…The decrease in pH is very pronounced in the initial phase of the process (particularly for alkaline solutions) because there is a greater ozone consumption and dye degradation/mineralization. Alvares et al [30], Soares et al [31] and several other researchers have observed that ozone decomposition is directly affected by the solution pH. Hydroxyl radicals are formed from ozone decomposition at high pH values, while molecular ozone remains as the main oxidant at low pH.…”

“…8. According to Alvares et al [30], the cleavage of the chromophoric group suggests that color removal is the first step of partial oxidation.…”

EVALUATION OF UV/O3AND UV/H2O2PROCESSES FOR NONBIODEGRADABLE COMPOUNDS: IMPLICATIONS FOR INTEGRATION WITH BIOLOGICAL PROCESSES FOR EFFLUENT TREATMENT

“…Therefore, it should make economic sense to employ UV-O 3 and UV-H 2 O 2 processes specifically for the destruction of nonbiodegradable compounds (or streams) and employ biological processes for the destruction of biodegradable compounds (or streams) at a given site. Moreover, when nonbiodegradable compounds (or streams) undergo oxidation through UV-O 3 and UV-H 2 O 2 processes, it results mostly in biodegradable compounds (Carberry and Benzing, 1991;Alvares et al, 2001;Arsan-Alaton and Balcioglu, 2001). Therefore, for nonbiodegradable compounds (or streams), it will be optimal to employ the UV-O 3 or UV-H 2 O 2 process first for the destruction of nonbiodegradable entities, followed by biological processes for the bulk of removal of COD.…”