Leather wastewater contains high molecular weight compounds such as softeners, penetrants, and surfactants, which are difficult to biodegrade. Before biological treatment, ozone is used to oxidize wastewater, transforming these high molecular weight organic compounds into low molecular weight forms, even easily digestible simple biological organisms, thereby improving the biodegradability of organisms. Experimental results have shown that after ozone treatment, the BOD5 of leather wastewater,There is a significant decrease in CODcr and chromaticity. Before biological treatment, hydrolysis acidification is carried out to treat the wastewaterThe value of m (BOD5/m (CODcr) is determined by0.2 increased toAbove 0.4, it greatly improves the biodegradability of wastewater and provides favorable conditions for aerobic biochemical treatment. Compared with the traditional physicochemical pretreatment technology, these two technologies can not only improve the biodegradability of wastewater, but also solve the foam problem in the process of wastewater treatment, with less sludge production, providing a way to solve the large amount of sludge generated in the treatment of leather wastewater. Coagulants and coagulants can also be added to remove chemical additives that are not easily biodegradable in leather wastewater. Generally, ferrous sulfate or basic aluminum chloride is used, with a dosage of0.03% -0.05%, removableCODcr andBOD5 approximately50%，S2-70% or more,SS and chromaticityMore than 80%.