Regeneration of activated sludge and methods of its control

Abstract

The analysis of the problem of regeneration of activated sludge during aerobic biological wastewater treatment is carried out, it is noted that the process of natural and artificial sludge regeneration becomes one of the key stages of wasterwater treatment plants in conditions of increasing anthropogenic impact on the aquatic environment.  New tasks are assigned to the active sludge for removal not only biogenic elements but also pollutions of wastewater with ballast, inhibitory and toxic substances, their oxidation and detoxification. This is facilitated by the property of sludge to accumulate in large quantities non-degradable, difficult to decompose and toxic organic and inorganic pollutants. his leads to swelling, a decrease in the metabolic and physiological activity of sludge, worsens the quality of wastewater treatment, creates problems for the disposal of excess sludge contaminated with hazardous substances, and also requires mandatory regeneration of sludge when it is returned to treatment plants. The existing system for monitoring the regeneration of activated sludge is based on an characterizing the oxidative capacity of sludge according to the indicators of BOD_f, and does not allow for operational monitoring of its condition during wastewater treatment and sludge regeneration. The purpose of the work is to analyze the process of regeneration of activated sludge and the choice of effective methods of its control. It is proposed a system of methods for monitoring sludge condition, including analysis of sedimentation, adsorption properties; reductase activity, as well as surface tension strength, the index of toxicity of the filler fluid during sludge regeneration. The study showed that the most sensitive indicators of the degree of regeneration of activated sludge are its adsorption capacity and cell reductase activity. The duration and complexity of the analysis of sludge by the optical-reductase method is an order of magnitude lower than that of the sorption method, which allows it to be used for operational monitoring of the state of sludge during wastewater treatment and its regeneration. The discovered effect of solubilization of non-oxidizable sludge pollutants and their discharge into the aquatic environment in micellar form expands the understanding of the mechanism of regeneration of activated sludge. It is shown that it includes 2 stages: additional oxidation of hard-to-destroy substances with oxygen in the air under conditions of silt starvation, as well as synthesis and isolation of biosurfactants that clean the surface of sludge from non-destructible compounds. The two-stage nature of the change in the toxicity index of the filler fluid during sludge regeneration makes it possible to determine the proportion of oxidizable and non-oxidizable pollutants associated with activated sludge.