With the rapid development of society and economy and the improvement of people's living standards, the problem of water environment pollution has increasingly attracted widespread attention in society.  Over the past decades, technological advances and the accumulation of experience have resulted in the effective treatment of conventional domestic sewage.  However, due to the complex composition and stable molecular structure of refractory organic contaminant in industrial wastewater, the use of conventional biochemical processing techniques is difficult to meet the emission standards.  In particular, the treatment of high-salt, high-ammonia nitrogen, and high-concentration refractory organic wastewaters still needs constant exploration and research.  In addition, as the emission standards increase and the cost of water increases, the reuse of treated wastewater becomes increasingly important. 
From the perspective of sources, the high-salt, high-ammonia nitrogen, and high-concentration refractory organic wastewater mainly come from industries such as synthetic pharmaceuticals, pesticide production, papermaking black liquor, tannery wastewater, monosodium glutamate production, petroleum refining, and coal chemical industries.  From the perspective of structure and characteristics, refractory organics mainly include: polycyclic aromatic hydrocarbons, heterocyclic compounds, chlorinated aromatic compounds, organic cyanides, organic synthetic polymer compounds, and so on.  The degradation mechanism of these compounds is to change their molecular structures through oxidation, reduction, co-metabolism and other mechanisms and gradually to transform into small molecules.  Therefore, wet catalytic oxidation, supercritical oxidation, Fenton treatment, ozone oxidation and other technologies can be used to deal with refractory organics, but in the case of high ammonia nitrogen concentration, the subsequent use of traditional anaerobic or aerobic process is difficult to achieve the denitrification requirements.  In addition, due to the high concentration of organic matter, when multi-effect evaporation or reverse osmosis treatment is used, the evaporator is likely to be clogged or the membrane is fouled, resulting in difficult cleaning and increased processing costs. 
Fenton technology is a commonly used advanced oxidation technology, and is often used to treat high-concentration refractory organic wastewater, such as dye wastewater, phenolic wastewater, acrylonitrile wastewater, papermaking black liquor, landfill leachate, and so on.  However, whether a standard Fenton reagent or a modified Fenton reagent is used, it is required to have a normal effect at a pH of 3-5.  Non-homogeneous Fenton technology can produce more HO.  by loading the iron catalyst onto the substrate even under neutral pH conditions, thereby avoiding excessive salinity due to the addition of a alkali to adjust the pH prior to subsequent biological treatment.  After the COD is lowered, the denitrification treatment needs to supplement the carbon source, resulting in cost increase.  Anaerobic ammonia oxidation technology can effectively solve this problem by denitrifying with nitrate or nitrite as electron acceptors.