Commissioning of the Biological Treatment Stage at the Central Wastewater Treatment Plant in Ostrava-Přívoz

In recent days, the Central Wastewater Treatment Plant (ČOV) in Ostrava has entered its next phase of operation. With the gradual launch of the so-called biological treatment stage, the period during which the country’s third-largest wastewater treatment plant was not fully operational has come to an end. Thanks to the dedicated efforts of employees of Ostrava Waterworks and Sewerage (OVAK), the City of Ostrava, and various contractors, the damage is being systematically repaired.

“Since the mechanical wastewater treatment process was restarted in January, we have also managed to repair and activate the biological treatment stage. Our commitment to restoring both treatment stages by March of this year was successfully fulfilled on Saturday, March 1, through intensive work. It is worth mentioning that some equipment was sourced from abroad, and suppliers responded promptly to the urgency of the situation—our thanks go out to them. For example, blowers were delivered from Finland. The good news is that the wastewater pumping station is now back in operation, meaning all incoming wastewater is being properly treated. Now, we need to complete some minor repairs and allow time for the bacteria—whose activity depends on temperature—to fully regenerate, ensuring that the treated water meets strict legal standards once again. To restart the biological treatment process, several essential repairs were needed. Electrical substations had to be restored, flooded cables near the sedimentation tanks were replaced, new blowers for aeration tanks were installed, sluice gates and sedimentation tank rails were repaired, and all related electrical systems were restored. Additionally, more than 550 m³ of activated sludge was introduced to seed the biological treatment process,” explained Aleš Boháč, Deputy Mayor for Environmental Affairs.

Thanks to funding from the Ministry of the Environment, the city's involvement, and the dedication of OVAK employees and contractors, the recovery timeline has been maintained. The treatment efficiency of the aeration tanks is expected to gradually improve as microorganisms grow, as system loads increase, and as remaining repairs to sludge separation facilities are completed. Full technological capacity, equivalent to pre-flood levels, should be achieved by mid-year. As treatment efficiency improves, water quality in the Odra River will also continue to get better.

Repairs to various flood-damaged infrastructure, such as pumping stations and sedimentation tanks, are still ongoing. Even after full operational capacity is restored, additional technological systems—while not immediately necessary for restarting the plant—will need repairs to ensure the long-term reliable operation of the treatment facility. The most challenging repairs took place in areas where wastewater continued to flow from the sewer system and where groundwater infiltration complicated restoration efforts.