Specificities of the study of physical and chemical treatment of wastewater with a significant content of synthetic phosphate-based detergents

Abstract

The relevance of research. Despite the decrease in the total volume of sewage over the first decades of the 21st century in the territory of Ukraine, the nature of the contaminants that make up their composition has changed significantly. In particular, the content of phosphate compounds and ammonium nitrogen increased. The increase in the phosphate component of wastewater is caused by the widespread of synthetic phosphate-based detergents. Existing treatment facilities are not designed to remove significant volumes of phosphate compounds. That provokes the process of reservoirs eutrophication, their secondary contamination due to biological processes (catastrophic reproduction of cyanobacteria and rapid development of higher aquatic vegetation). Possible ways to solve this issue include: prohibition of the use of synthetic phosphate-based detergents; reconstruction of sewage treatment plants, which will enable effective retention of phosphate compounds; reconstruction of water treatment plants, which will enable to purify poor quality water from water sources and the combination of all these three ways, but not with the global prohibition of the use of synthetic phosphate-based detergents, but by increasing the extra charges for them to the level of phosphate-free detergents and subsidizing them for that. Research results. A number of physical and chemical methods based on the oxidation reactions of a model solution of synthetic detergent were investigated. In particular, such a promising area of new water purification technologies as the use of so-called advanced oxidation technologies (AOTs), in which strong oxidants are generated by electric discharges in the water-air environment or on the surface of a thin film of water. Ozonation was performed using an apparatus that combined cavitation treatment and ozonation. The results of organic component oxidation experimental studies of the model solution with the use of «Fenton» reagent, physical methods of purification (ozonation with cavitation, plasma treatment) and treatment with hydrogen peroxide are presented. Conclusions. The best oxidation effect of the organic component of the model solution was achieved with the use of «Fenton» reagent – 89.5 %. All physical methods (cavitation with ozonation and plasma treatment) achieved about 50 % reduction in COD content: ozonation - 58.3 %; plasma treatment - 51.3 %. The worst results were obtained when treating with hydrogen peroxide - 1.78 %. The experiments in this area need to be continued because all the methods that have been tested require further water purification. In our view, it may be advantageous to combine physical treatment methods with «Fenton» reagent or with additional adsorption of organic compounds residues or with additional biological treatment.