The mechanical waste water treatment plant went into operation in 1981 with design capacity of 115,800 m³/day. Its current load is 45-50000 m³/d.

Waste water is collected at the pumping station and is fed through a mixing basin to 3 radial-flow settling tanks where it stays for 6-7 hours to allow the suspended particles to settle. Part of the clarified waste water is pumped for after-treatment (i.e. to radial-flow settling tanks for additional settling of suspended particles) to be reused in paper production and other purposes. The remaining clarified water, together with industrial and domestic effluents of the local community, is pumped to the biological treatment facilities.

The sludge accumulated in the settling tanks is regularly removed for final sedimentation, concentration and disposal at the sludge dumps.

JSC Volga’s biological waste water treatment facilities process waste water coming from our own mechanical treatment plant as well as from other industrial plants and the local community.

The design capacity of the biological treatment plant is 149,000 m³/day, while the current load is just about 60,000 m³/day.

The main treatment by biological oxidants and oxygenation of waste water takes place in the aero tanks. The treatment effect is due to the influence of micro-organisms that are active in the presence of nitrogen, phosphorus and oxygen.

For several years, modernisation of the aero tanks was the focus of a collaborative work between the treatment plant personnel, specialists from the EAC and other departments of JSC Volga. The project has been completed.

The upgrading of the aeration system required replacement of the existing power-consuming mechanical aerators (i.e. agitators) for efficient modern ones manufactured by “Green Frog”. The new construction comprises stainless steel collectors equipped with small round funnels that have a porous PE membrane. Warm air blown through the water enrich the waste water with oxygen. The oxygen utilization coefficient under the new process is 14-15% against the previous figure of 10%. The increased oxygen utilization enables reduced air consumption from the compression plant, thus saving electric power.

The results of various analyses by EAC show that the suspended particles content and biochemical oxygen demand (BOD) of the discharged water after the treatment plants is at acceptable levels. However, further upgrading of the water treatment facilities will continue.

One major investment project concerns the construction of a boiler for bark and sludge. After completion, the sludge waste from the water treatment plants will be burned in a modern boiler removing negative environmental impacts concerned with dumping sludge waste.