3.5.3. Biodegradation and ecotoxicity assessment
Fig. 8 shows the SUVA and biodegradability index (BOD5/COD ratios) of the raw NF concentrate and samples treated by ozonation or UV/O3 process. SUVA was known as a useful parameter for estimating the dissolved aromatic carbon content in aquatic systems [46]. Both ozonation and UV/O3 treatment decreased the SUVA value of the raw NF concentrate with reduction of 12% and 19% respectively, showing that both processes were capable of destroying the aromatic structure of organics in NF concentrate. This could be attributed to electrophilic substitution reactions of aromatic compounds with electrophilic species, such as ozone and radical dotOH [36].