At present, the crystallization method has become a hotspot in the field of wastewater treatment. The crystallization method not only remove phosphorus effectively in wastewater, but the phosphorus also can be recycled. The crystallization method includes ammonium magnesium phosphate crystallization method, calcium hydroxy calcium phosphate crystallization method, vivianite crystallization method and so on. The study introduced the principle of phosphorus removal and the influencing factors of the three crystallization methods, and discussed the effects of pH, ion concentration and stirring conditions on the crystallization. pH has the greatest influence on crystallization among of them. The best pH of the vivianite crystallization is between 7 and 9, and it is easier to form crystals in the general wastewater than MAP and HAP. In a certain concentration range, the phosphorus removal rate increased with the increase of ion concentration. In the case of air stirring or cyclical stirring, crystallization can be instantly formed, effectively increasing the crystallization rate. Finally, the application prospect of crystallization method in the treatment of phosphorus wastewater is prospected, which provides technical and theoretical support for the removal and recovery of phosphorus in wastewater.

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With the development of the refining industry, the treatment of refinery wastewater has become an urgent problem. In this study, a ceramic membrane (CM) was combined with Fenton-activated carbon (AC) adsorption to dispose of refinery wastewater. The effect of the combined process was analyzed using excitation–emission matrix (EEM), ultraviolet-visible (UV-vis) and Fourier transform infrared spectroscopies (FTIR). Compared with direct filtration, the combined process could significantly improve the removal of organic pollution, where the removal rate of the COD and TOC could be 70% and the turbidity removal rate was above 97%. It was found that the effluent could meet the local standards. In this study, the membrane fouling was analyzed for the impact of the pretreatment on the membrane direction. The results showed that Fenton-AC absorption could effectively alleviate membrane fouling. The optimal critical flux of the combined process was increased from 60 to 82 L/(m2·h) compared with direct filtration. After running for about 20 d, the flux remained at about 55 L/(m2·h) and the membrane-fouling resistance was only 1.2 × 1012 m−1. The Hermia model revealed that cake filtration was present in the early stages of the combined process. These results could be of great use in improving the treatment efficiency and operation cycle of refinery wastewater.

Membrane separation technology, as an important water quality safeguards, has been widely studied and applied in water and wastewater treatment，because of its advantages ( low cost, convenient operation, no phase change and no secondary pollution). Compared with organic membrane, the inorganic ceramic membrane with more stable material properties, which can be described as high temperature resistance, acid-alkali resistance and good chemical stability, has more superiority in the complex wastewater，that have the characteristics of strong acidity, alkaline and corrosive, such as oily wastewater. This article summarizes the classification and characteristics of the ceramic membrane, and analyzes its filtration mechanism. The utilization and development of ceramic membrane and its combination process in different types of oily wastewater treatment are discussed. The future development and existing problems to be solved of ceramic membranes is proposed.

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