Theoretical and Experimental Studies of Processes of Oily Wastewater Treatment with a Synergetic Mixture

Abstract

Theoretical studies of processes of oily wastewater treatment for removing various impurities determined the main mechanism of the formation of coagulation structures and aggregates with their subsequent settling and phase separation, which disturb the aggregation and kinetic stability of the medium. It was found that a more advanced coagulation leads to the destruction of interlayers of the medium between particles, which brings the particles into direct contact with each other. This results in the formation of rigid aggregates with fractal structure, which consist both of hard particles, and of asphaltenes and resins, sometimes shaped as flakes. If the particles coagulate in a turbulent flow, their number decreases, although their sizes increase up to the sizes of aggregates. It was noted that the formation of coagulation structures is beneficial for separation of the solid phase from the liquid phase in wastewater treatment. An investigation was made of the potential of a synergetic mixture of slaked lime and ferric chloride for accelerating the formation of coagulation structures in oily wastewater treatment. Experimental studies showed the efficiency of using such a mixture for removing petroleum products and solid particles in wastewater treatment. In intense stirring of this mixture in a mixer at 1500–2000 rpm, isotropic turbulence is reached, which favors the coagulation and aggregation of particles. It was found that the best composition of the mixture is 1.0 g of slaked lime and 0.06 cm³ of ferric chloride, which best promote the high-quality coagulation and settling of particles. Based on the boundary conditions for mass transfer, kinetic models for calculating the consumption of the mixture were proposed, and a kinetic parameter was estimated. The results of the performed experiments showed that, with increasing concentration of the mixture, the impurity content of wastewater progressively decreases, and wastewater becomes almost transparent. Using the synergetic mixture in wastewater treatment creates conditions for the formation of stronger structures of aggregates prone to natural settling.