After studying changes of biodegradability (BOD5/CODCr

the ratio of biochemical oxygen demand after 5 days to chemical oxygen demand) of several refractory organic compounds before and after pre-ozonation a oxidative degree conception of organic compound

defined as (4TOC-CODCr)/4TOC

in which TOC refers to total organic carbon

has been put forward. The results show that after pre-ozonation the oxidative degrees and biodegradability of nitrobenzene

1

2-dimethyl phthalate and sulfosalicylic acid solutions all increases

and that there is a positive correlation between the sample's oxidative degree and their biodegradability. The BOD5/CODCr values of the samples can be more than 0.2 when its oxidative degrees are greater than 0.65

showing that these samples can be directly treated by biological treatment. The results of pre-treating acidic chemical wastewater by an advanced ozone-based oxidative process (Ti(Ⅳ)/H2O2/O3) show that the removal rates of CODCr and TOC were 66.09% and 34.09% after 120 min

respectively

and that the oxidative degree and BOD5/CODCr value of the acidic chemical wastewater increased from initial 0.346 and 0.05 to 0.664 and 0.332

respectively. There also is a good positive correlation between the oxidative degree and the BOD5/CODCr value. The results mentioned above indicate that the oxidative degree value can probably be used to evaluate the biodegradability of wastewater. Due to the determination of the oxidative degree is simple and fast

it will be of significance for common application of ozonation technology in pre-treatment of refractory wastewater.