Dephenolization of wastewater: techniques and prospects

The current legislation provides for tight standards of residual concentrations of pollutants if wastewater is discharged into reservoirs. The problem of waste management for phenolic compounds in wastewater is one of the most urgent, which requires the development of new efficient, environmentally friendly and economical methods. The conditions of wastewater formation are very diverse in chemical composition; this implies the use of specific technological conditions for purification, taking into account not only complexity of the component composition of wastewater, but also the presence of related substances, which in most cases are not fully considered. The range of concentrations of phenols in various industries varies significantly. Currently, there are various methods of wastewater dephenolization. Choosing a technique for removing phenol and its derivatives, it is necessary to determine the composition of the related contaminants, and adopt a purification method on the basis of the requirements, established for the quality of the purified wastewater. Currently, the development of optimal solutions for treatment of phenolic wastewater is a priority, taking into account the subsequent use of treated water. The applied methods of dephenolization can be divided into two groups: separation methods and destruction methods. Biopurification is mainly used at sufficiently low concentrations of phenol, the restrictions for biopurification of wastewater are associated with the biodegradability of pollutants and the presence of substances that inhibit the growth of microorganisms in the composition of wastewater. Photocatalytic oxidation with a fairly wide range of photocatalysts is considered one of the promising techniques for destruction of organic pollutants. The main methods of removal of phenols and their derivatives from wastewater are systematized and described. Attention is mainly paid to the most efficient methods of phenol degradation, such as photocatalytic oxidation, electrochemical oxidation, and biopurification.