RESEARCH ON IMPROVEMENT OF THE METHOD OF PERIODIC AERATION OF WASTEWATER

Abstract

The aeration process is a key part of biological wastewater treatment technology. But, paradoxically, during the existence of this technology, it has not changed significantly. The process of aeration of wastewater remains the largest consumer of electricity in the entire complex of treatment facilities. The possibility of adjusting the duration of the aeration cycle depending on the "explosive" change in the amount of contaminants was stated. In this case, the system must respond to this "perturbation" and adjust the duration of the aeration cycle to provide the necessary oxygen regime of biological oxidation of contaminants. The research data on the method of periodic aeration based on a comparison of the concentration of oxygen in the liquid to be cleaned and in the gases leaving after aeration are presented. The basic principle is that the aeration system continues to supply oxygen, which is no longer able to diffuse into the aerated liquid, and comes to the surface, bypassing the process of mass transfer. The experimentally established method of adjusting the duration of aeration periods for implementation in one aeration tank can be applied to a whole group of aeration tanks. Using the method in the optimal mode for each of the specified number of aeration tanks is impossible without the use of a microprocessor. Therefore, a control method was developed that allows the application of a fundamentally new algorithm for periodic aeration. This algorithm allows to increase the growth of activated sludge and to increase the efficiency of wastewater treatment. To assess the possibility of stabilizing the operation of certain aeration tanks, in the implementation of intermittent aeration by the concentration of oxygen in the liquid, a model example was considered, from which follows the differential equation of oxygen balance in the liquid. The study of this equation for stability and behavior in the phase plane makes it possible to choose the conditions under which the periodic aeration algorithm will be the most efficient in terms of purification and energy consumption. Theoretical calculation gave a mathematical justification for the experimental data. Based on numerical calculations, the condition of optimal operation of the aeration system for a group of aeration tanks is derived. Thus, it was found that the optimal concentration of oxygen in the liquid at which to start aeration is 0.06-0.12 mg / dm3. Periodic aeration with a period of 30 minutes makes it possible to maintain a stable gradient of oxygen concentrations in the liquid. The productivity of treatment plants according to the developed algorithm of controlled aeration, in accordance with the concentration of oxygen in the liquid to be cleaned, ensures the rational use of electricity.