FEATURES OF THE STRUCTURE, FUNCTIONING AND RECONSTRUCTION OF THE LANDFILL NIZHNEKAMSKNEFTEKHIM PUBLIC JOINT STOCK Co.

PJSC Nizhnekamskneftekhim is one of the largest petrochemical companies in Europe. Industrial production was launched there in 1967. Production waste is stored in a sludge reservoir and waste landfill. The landfill has been operating since 1982. It is equipped with systems of surface and underground drainage, impervious curtains, and two belts of observation wells. More than 0.5 million m³ of mostly solid waste III-V classes of hazard has been accumulated there. The landfill capacity is depleted by more than 80%. Its operation has led to a significant groundwater level rise (4.0–4.5 m) and groundwater pollution, the water salinity reaching 12.75 g/l, and hardness, 73.9 mmol/l. These negative hydrogeoecological effects are primarily due to increased atmospheric recharge of groundwater and the active interaction of atmospheric precipitation with the waste substance. There is plan to reconstruct the landfill. It involves encapsulating the waste in a watertight reservoir confined by artificial geosynthetic materials with extremely low filtration properties. Hydrodynamic and balance methods were used to determine the infiltration supply of groundwater in natural and disturbed conditions, productivity of underground drainage; the continuously formed flow rate of polluted groundwater, which is not intercepted by drainage system (with the flow discharge equal to 116.7 m³/day); as well as modern and predicted (postreconstruction) water balances. The effectiveness of the existing engineering protective structures of the landfill was assessed. It is shown that the planned reconstruction should lead to a decrease in the groundwater level and its pollution degree. In this case, the concentrations of organic substances, which are the priority pollutants, will decrease most intensely. The geological environment of the landfill site is characterized by significant buffer (protective) properties. They control just local spreading of contaminated groundwater. According to the data of numerous different-time sampling at a distance of 1.0–1.5 km from the landfill in the direction of groundwater current spreading, no signs of pollution caused by the landfill operation are registered. The main processes determining the self-purification of groundwater are as follows: dilution of polluted water by pure infiltration nutrition, the minimum layer of which is 67.6 mm/year; chemo- and biodestruction of pollutants, their sorption, diffusion-dispersion scattering and precipitation as pH–Eh conditions change.