When applying chemical methods, excessive use of certain reagents can easily lead to secondary pollution of water bodies. Therefore, relevant experimental research should be conducted before designing the treatment. Chemical methods include the iron-carbon method, chemical oxidation-reduction method (Fenton’s reagent, H2O2, O3), and deep oxidation technology.
(1) Oxidation Method This method can improve the biodegradability of wastewater and also has a good COD removal rate.
Oxygen oxidation treatment of three types of antibiotic wastewater showed that the wastewater treated with ozone oxidation not only improved the BOD5/COD ratio but also achieved a COD removal rate of over 80%.
Fenton’s Reagent Treatment Method The combination of ferrous salt and H2O2 is called Fenton’s reagent, which can effectively remove recalcitrant organic matter that traditional wastewater treatment technologies cannot remove. With further research, ultraviolet light (UV) and oxalate (C2O42-) have been introduced into Fenton’s reagent, greatly enhancing its oxidation capacity. Using TiO2 as a catalyst and a 9W low-pressure mercury lamp as a light source, Fenton’s reagent was used to treat pharmaceutical wastewater, achieving a decolorization rate of 98% and a COD removal rate of 93.5%, with nitrobenzene compounds decreasing from 8.15 mg/L to 0.43 mg/L.
(2) Iron-Carbon Method Industrial operation shows that using Fe-C as a pretreatment step for pharmaceutical wastewater significantly improves the biodegradability of the effluent. A combined iron-carbon-microelectrolysis-anaerobic-aerobic-air flotation process was used to treat wastewater from the production of pharmaceutical intermediates such as methyl methacrylate and cyclofloxacin hydrochloride. After treatment using the iron-carbon method, the COD removal rate reached 25%, and the final effluent met the comprehensive wastewater discharge standards.
