The worlds growing population demands more food and creates more waste. Economically viable and environmentally friendly would be to use sewage sludge for agricultural production. There are several limitations for this use – heavy metal content, pathogenic microorganisms, helminths etc.. The different methods of treatment of sewage sludge helps to overcome this problem. The aim of the study is to find the effects of treated sewage sludge on the growth of maize and changes in soil biological activity. Experiments were carried out with dry sewage sludge preparation (SSP) in the such combinations 1) SSP, 2) SSP+PK, 3) SSP+NPK. Controls- loamy soil without additional fertilizer, soil mixed with mineral fertilizer (Kristalon 18:18:18). Maize (Zea mays var. saccharata ‘Elan F1’) was grown. Experiments were arranged in 1L vegetation containers placed in open area with additional watering. Plant growth parameters and soil enzymatic activity was detected. The SSP alone and in combination with potassium and phosphorus fertilizers does not provide the maize with the mineral nutrients in appropriate value, therefore, the combination of SSP with nitrogen containing fertilizers significantly improves plant growth and promotes development. The use of SSP increases the microbiological activity of the soil. This can have a beneficial long-term effect on the mineral nutrition of plants.

Conversion of organic-containing sludges to a high value fertilizer is considered to be a rational solution from a recycling point of view. Aerobic respiration could serve as an indicator of stability and maturity of the treated sewage sludge (SS). The aim of this study was to characterize two SS samples, obtained from different wastewater treatment plants („D” and „J”), i.e, at the initial stage of treatment, alone and with amendments. Two methods for estimation of microbial respiration, as well as dehydrogenase activity were used. The SS-J demonstrated the higher microbial biodegradation activity, as compared to SS-D. In experiments with OxiTop® device, statistically significant (p<0.05) differences of the pressure drop between SS-J and SS-D have been revealed. Addition of peat to SS resulted in a more intensive pressure drop, compared to non-amended SS, i.e., -145 hPa vs. -76 hPa for SS-D and-199 hPa vs. -180 hPa for SS-J, respectively. The obtained results represent a methodical approach for characterization of raw SS in order to evaluate the amount of aerobically degradable organic substances and intensity of their oxidation. Further research is needed for highlighting the mechanisms responsible for interrelation of respiration intensity, bacterial community activity and other metabolic changes towards SS stabilization.

There are many threats to the quality of human life in the environment of the modern world. Among them, one can single out the growing pollution of the environment and water resources, which leads to crop failures, hunger, and disease. Concomitantly, narrowly targeted measures often lead to an aggravation of the situation as a whole. For example, an attempt to solve the problem of yield quality deterioration by increasing the use of synthetic fertilizers leads to accelerated destruction of the fertile layer due to the irreversible loss of organic matter. It is proposed to use complex technology, including standard dewatering of sewage sludge at wastewater treatment plants, transportation, disinfection, and processing into a highly effective organic fertilizer. This paper deals with the problems of transportation of a viscous, epidemically dangerous, biologically aggressive substance for its further processing. To improve the quality of working conditions directly at treatment facilities to protect the environment, human health and counteract the emergence of epidemics, it is necessary to develop sealed systems for safe sludge transportation, maximally isolated from the environmentwith taking into account many variables, such as environmental temperature, intern biological processes, various tribometric, rheological and thermophysical properties. Upon the laboratory studies and bench tests, the main affected factors were identified. Fundamental design solutions for transporting substances with rheological characteristics of the sludge below 80% humidity level are proposed. Research has been carried out to decontaminate the substance during its transportation.

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The article is devoted to the problem of designing recycling in sustainable logistics systems in the field of processing wastewater treatment waste - municipal sewage sludge (MSS). The essence of the developed and proposed wastewater treatment project is based on its integration into the city's public utilities system, which will be a single basis for a closed-type logistics system. This approach to the design of sustainable logistics systems ensures the formation of a closed material flow in terms of "supply of raw materials - production - product distribution". This allows solving two problems: ensuring the creation of a closed logistics system and developing a new type of fertilizer. The solutions proposed in this project in the implementation of the MSS processing project are complex and allow implementing all areas of the sustainable development strategy. The design technology makes it possible to completely close the logistics cycle for the supply and processing of MSS into finished products in the form of organic fertilizers.