# Rationale for the Combined Use of Biological Processes and AOPs in Wastewater Treatment Tasks
## 3 Results and Discussion
### Modeling the Effects of Antibiotics and Surfactants on the Activity of Bioprocesses
Disadvantages of AOPs neutralized by biochemical solutions include:  
- Blocking organic pollutants from synthesizing oxidants, transporting them to the necessary reaction zones;  
- Reduction of oxidation efficiency;  
- Use of active oxidants to remove pollutants, which are also eliminated by cheaper and simpler solutions. To substantiate these directions of combinations of cleaning methods in order to level the disadvantages of AOPs using biochemical solutions, experiments on the treatment of aqueous solution circulating in a closed-loop water supply plant for industrial fish farming were conducted. Based on the above-mentioned purposes of combined use, a scheme of water treatment is proposed (Figure 8). Consider in more detail each of the treatment units shown in Figure 8:  
- Pre-biological treatment unit (aerobic filtration): removal (partial) of pollutants that passivate AOPs' oxidation processes (reduce efficiency); biochemical \"start-up\" of redox processes;  
- Pre-oxidation module (pressurized electrolysis, anolyte generation, chlorine-derived oxidizers): direct oxidation of pollutants, formation of pollutant complexes for more effective biological removal, elimination of surfactants, and partial elimination of antibiotics;  
- Block of the main biological treatment (anaerobic denitrification stage): NOx reduction to gaseous nitrogen in the process of activity of heterotrophic denitrifying bacteria, with the formation of anoxic zones in the activated sludge flocculus against the background of anaerbiosis of the biosystem as a whole;  
- Biological processes activation module (electrolysis activation units, hydro- and ultrasonic cavitators, electromagnetic irradiators): intensification of biological processes of water treatment at the stage of dephosphatation under biochemical sulfate reduction with precipitation of heavy metals;  
- AOPs pre-oxidation (sterilization) and removal of specific pollutants (photo-isolation, Fenton reaction, pressurized electrolysis, electrokinetic oxidation) module: final elimination of pollutants of aqueous solutions submitted to oxidation (reduction), including SPAs and antibiotics. The process-control module in real time: management and coordination of minimum-reagent combination of biological processes and AOPs for wastewater treatment in real time (by indicators: pH, COD, turbidity, ORP, silt index, conductivity, and temperature). Using such a system (Figure 8), it is possible to apply the elements of inorganic pollutant removal, pH correction, and other necessary solutions. In Figure 9 we have formalized the flows of the combined wastewater treatment system with the identification of several control parameters, grouping them into two blocks:  
1. The basic parameters of control on the characteristic influence factors of the input wastewater;
2. Control indicators of the biological system, which take into account the state of the biocenosis of activated sludge when affecting the basic parameters of control. It is important to note that the categorical parameters of biosystem state control--i.e., forming a response to the parameters of basic control--have a \"mutual optimum\" zone of intersection. Such a zone is understood as a range of values of the parameters of the biosystem in their combination. For example, the dependence of the sludge index on the dose of activated sludge when increasing its sedimentation rate--this maintains a high level of oxidation capacity of aeration tanks, determining the amount of contaminants that can be oxidized by microbial biocenosis inhabiting a certain volume of activated sludge or biofilm for 1 day. In this case, the oxidative capacity of biological treatment facilities depends on the oxygen supply of microorganisms of different ecological and trophic groups of activated sludge, and on directional change in the chemical activity of microorganisms along the trophic chains. In the thermophilic mode, the oxidative capacity of sewage treatment plants is increased by 1.5-2 times, but this mode is more energy-consuming than the mesophilic one.