The engineering and geological properties of the surface layer of the tailing dump, mineral and chemical composition of tailings were studied, the probability of nickel ions migration to the adjacent water bodies was shown, the scheme of tailings processing by means of preliminary granulation and subsequent leaching using water, sulfuric acid solution and bacterial solution was proposed. It is confirmed that the application of 10% sulfuric acid solution as a binder using nitrite ion as an oxidizing agent allows to recover more than 50 % of nickel and 47.8 % of copper at the heap leaching stage. It is shown that 11.6 % of nickel and 13.5 % of copper are recovered by bioleaching of tailings pellets prestrengthened with polymer binder.

The possibility of poultry waste utilization based on a comprehensive technology, including biological and thermochemical conversion, is considered. Optimal technological parameters of anaerobic digestion of chicken manure in the mesophilic mode were determined. A basic technological scheme for waste utilization at a poultry farm in the Republic of Tatarstan is presented. A preliminary assessment of the material balance of the comprehensive technology is made.

Using the example of the phyto-purification system (PPS) (Lake Nizhniy Kaban, Republic of Tatarstan, Kazan), its effectiveness in suppressing water bloom, as well as in inhibiting the development of dinophytes and potentially toxic species of blue-green algae, was established. It was confirmed that cattail, calamus and water lily act as effective biofilters. It is concluded that in ponds with macrophytes, the water quality is improved in terms of phytoplankton (the total number and biomass are decreased, the proportion of green and diatom algae in the overall indicators is increased); dominant species causing water "blooming" are suppressed; transparency is increased, the trophic level (biological productivity) of water is decreased; the water quality class is improved from "dirty water" to "clean", from "extremely dirty" to "very clean – quite clean"; the effect of anthropogenic impact on water is reduced. It is recommended to build PPS in coastal zones of urban reservoirs, combining recreational and water treatment functions.

The issues of treatment of sewage sludge generated at sewage treatment plants from the point of view of greenhouse gas emissions are considered. The results of the conducted research on systematization and actualization of data on applied of wastewater sludge treatment processes are presented, the reasons for the insufficient use of anaerobic digestion processes in the activities of water utilities are noted on the example of the technological chain of biological wastewater treatment facilities in settlements and urban districts.

Equations describing the extraction dynamics of ethyl carbamate from a porous product using an organic solvent were derived. It is noted that the equations are an adaptation of the mathematical description of the adsorption and ion exchange process to the conditions of the solid-phase extraction process. It is concluded that the developed mathematical model will allow optimizing the process by reducing the amount of extractant and significantly reducing the duration of the process, while maintaining the structural and mechanical characteristics of the product.

Information on the impact of runoff from mining enterprises in the conditions of the North Caucasus was provided. The role of ore processing tailings in chemical pollution of the region was shown using the example of the Tyrnyauz and Sadon deposits. The mechanism and quantitative parameters of the impact of mining operations on the environment were formulated. It was concluded that radical protection of the environment from chemical pollution by industrial wastewater is only possible through the disposal and recycling of waste. Promising technologies for the treatment and disposal of industrial wastewater were presented.

The possibility of ash dump reclamation using perennial grasses (Festuca pratensis (Meadow Fescue), Bromus inermis (Awnless Brome) and Medicago polymorpha (Medicago varia)) both in monocropping and in grass mixtures was considered. The greatest increase in green mass was noted in Medicago polymorpha, and among cereal crops – in Bromus inermis. It was established that the Medicago polymorpha plant and the Bromus inermis + Medicago polymorpha grass mixture are effective for the ecologization of the ash dump in areas with the introduction of mineral background fertilizer.

The study was conducted to determine the degree of contamination of soils along the coastline of the Black River (right tributary of the Neva River). Gross and mobile forms of heavy metals were determined in the soil samples. It was found that industrial activity in areas along the river contributes to an increase in the concentrations of heavy metals in the soil cover. The ecological condition of the soils was studied using bioassay methods, and the selection of sensitive bioassays for the detection of contaminants was tested. The bioassays on the mortality of Daphnia magna Straus, on the chemotaxis of Paramecium caudatum ciliates, on the change in optical density of Chlorella vulgaris Beijer algae, and a contact bioassay on the seeds of Triticum vulgare L. were conducted. A "block" of bioassay systems was formed, which allows assessing the ecological state of these soils. Zones of increased ecological risk associated with the impact of highways, as well as the construction of residential complexes located along the river, were identified. The information obtained is recommended for use in applied purposes for managing the risks of technogenically contaminated soils.

The methods of geoecological monitoring of natural hydrocarbon gas emissions in marine waters were studied. A systematization of various indicators used for the detection of hydrocarbon manifestations was presented. A comparative analysis of modern remote and contact methods for detecting hydrocarbons in marine waters was conducted. An algorithm for conducting geoecological monitoring of hydrocarbons in marine waters was proposed, combining both remote and contact methods. It is noted that the obtained results allow us to outline the main tasks and prospects for research in the field of marine monitoring, detection of offshore oil and gas fields, as well as sustainable management of marine resources.

A methodological approach was developed for assessing the geoecological risk of river water pollution by biogenic substances due to diffuse runoff from agricultural and reclaimed lands, as well as from point sources, using the example of the left tributary of the Volga River. The results of studies on water quality assessment across river cross-sections based on monitoring data were presented, along with statistical processing of hydrochemical analysis data for analyzing the geoecological risk of river water pollution. A complex indicator was used – the specific combinatorial index of water pollution, which made it possible to assess the impact of the total presence of several pollutants. Calculations of the potential eco-economic damage were performed, and the geoecological risk of water pollution due to the influx of biogenic substances from the watershed of the studied river was assessed.

The features of accumulation of heavy metals by some species of wild plants (Trifolium montanum L. (mountain clover), Anthemis tinctoria L. (dyer's chamomile), Thymus serpyllum L. (creeping thyme), Galium verum L. (yellow bedstraw), Inula montana L. (mountain elecampane), Scutellaria supina L. (squamish skullcap)) were studied. Using the method of atomic absorption spectrometry, an analysis of soils and phytomaterial for the content of heavy metals (Cu, Zn, Fe, Mn, Ni, Pb, Co, Cd) was performed. Aspects of accumulation of metals and plant species accumulating heavy metals in increased quantities were established. It was suggested to use plants with high metal-accumulating capacity as promising candidates for phytoremediation of contaminated areas.