# Rationale for the Combined Use of Biological Processes and AOPs in Wastewater Treatment Tasks
## 4 Conclusions  
The main technological disadvantages of the systems of physical (mechanical), chemical, and biological methods of treatment were grouped into a single block diagram. It was highlighted that a common disadvantage of the methods is that it is necessary to monitor dozens of parameters of water quality and technological processes in real time, and there is a limited number of automated measuring devices that work reliably at industrial sites. It is also necessary to consider qualitative and quantitative parameters of the operation of the activated sludge biosystem in order to form a dynamic equilibrium in its species diversity for the most effective destruction of organic pollutants. Thus, a promising direction is the use of methodical approaches of the aggregation of different basic approaches to water treatment. As an example of a combination of different basic solutions, the use of biological processes as a technological core was considered, while reducing their disadvantages with the help of AOPs. Studies were conducted on water treatment using an electric process pilot plant to remove contaminants from the circulating water of fish farming equipment. It was determined that the deterioration of the treatment effect was due to the excessive presence of organic pollutants--primarily organic (total) nitrogen--compared to the complex oxidative potential of the system of \"anodic oxidation + photolysis\". This can be explained by the process of oxidation of organic nitrogen (total nitrogen) along the chain \"total nitrogen \(\rightarrow\) ammonium nitrogen \(\rightarrow\) nitrites \(\rightarrow\) nitrates\", and by the insufficient oxidative potential of the destruction of pollutants by anode oxidation alone. In an in vitro microbiological study to assess the resistance of the biocenosis to an antibiotic such as amoxicillin, we observed the same pattern. Thus, the value of the stunting diameter of the accumulating activated sludge culture when cultured with an antibiotic concentration of 2 mg/dm\({}^{3}\) and without the antibiotic was 4.7 \(\pm\) 2 mm and 3.2 \(\pm\) 2 mm (R--resistant), respectively, which shows the insensitivity of the accumulated activated sludge culture to low concentrations of this antibiotic. The stunting zone around the amoxicillin disk with a maximum dose of 8 mg/dm\({}^{3}\) was the largest in all dishes, and was 40.8 \(\pm\) 5 mm (S--sensitive). The results of bioindication of activated sludge cannot be taken as positive--even at the surfactant concentration of 10 mg/dm\({}^{3}\), which is still negative--which can be attributed to structural changes in the qualitative composition of the microbiocenosis, leading to a narrowing of species diversity. To implement the combined processes of biological treatment and AOPs, formalization of the main functional elements of the system, in terms of comprehensive elimination of the drawbacks of individual technological solutions of water treatment, and increasing their effectiveness, was carried out. The proposed combination of wastewater treatment methods can potentially be used for the treatment of wastewater from various industrial facilities with multicomponent pollutants of organic and inorganic nature:  
* Food enterprises (dairies, meat processing plants, fish processing, winemaking, cheese factories);
* Agro-industrial complexes (poultry farms, livestock farms, pig farms);
* Light industry (wood processing, tanneries, cosmetology);
* Communal objects. S.D. and V.C. ; writing--review, M.G. All authors have read and agreed to the published version of the manuscript. This research was funded by VEGA--Scientific Grant Agency of the Ministry of Education, Science, Research, and Sport of the Slovak Republic and the Slovak Academy of Sciences, grant number 1/0419/19. Not applicable.