STUDY OF THE PROCESS OF INDUSTRIAL WASTEWATER PURIFICATION WITH HIGH-CONCENTRATED ORGANIC IMPURITIES

Abstract

Introduction. Purification of industrial wastewater is an urgent task for modern chemical production. There is a large number of methods for wastewater treatment at the petrochemical enterprises, but the effectiveness of such methods is significantly reduced, and often is lost in the case of treatment of sewage of complex composition with high content of organic substances. The goal  of this paper is to search the possibility for reducing the level of sewage contamination and to study the effect of the biological neutralization system for the production of styrene and propylene oxide on the microorganisms. The task is to eliminate the flaring of wastewater in the production, redirecting the contaminated water to biological neutralization. Objects and methods of the research. The experiments were carried out with the real effluents of the actual chemical production of styrene and propylene oxide with COD values varying from 34 to 860 mg O2 / L. The degree of purification was determined by the dichromate method to change the COD index. Results. When the wastewater is acidified in the production of styrene and propylene oxide, the organic substances contained in the effluent are resolved in a dissolved form into a separate emulsion phase, which is removed by extraction with organic solvents. This leads to a decrease in COD by 38%. Introduction of the proposed method of preparation of effluents for biological treatment in an industrial experiment showed that biological post-treatment of effluents was possible with a decrease in the value of the COD index to 40 gO₂ / l. It was also found that the desired result could be achieved by the methods of dilution of effluent with industrial water or an effluent from the dehydration stage of styrene and propylene oxide production when the effluent was acidified to a neutral medium (pH = 7-8). Conclusion. The possibility for reducing the level of sewage contamination with organic substances transferring such substances to a water insoluble form by acidifying the waste water to low pH values (from 1 to 3) was revealed. It was also found that application of the extraction method in combination with acidification of effluents made it possible to achieve a higher degree of purification of effluents from organic components that interfered with biological purification. In this case, the efficiency of purification is increased by 38%. During the industrial experiment at the operating enterprise, the maximum permissible value of the COD indicator (40 gO₂ / l) was determined. At the figures of 40 gO₂ / l, the effluents can be sent to biological neutralization, excluding the death of biological community. Morever, it is possible to direct the treated waters to biological neutralization without lowering the pH of these waters to a deep acidic medium by diluting the effluent with industrial water or drainage from the dehydration stage having a low COD value.