puhdistamoa

Puhdistamo (Finnish for wastewater treatment plant) is a facility designed to treat wastewater from households, businesses, and industry. The aim is to remove pollutants, protect water bodies, and recover resources. They are part of municipal infrastructure and may be operated by municipalities or utilities; in some cases they treat industrial effluent.

The typical treatment sequence includes preliminary treatment (screens and grit removal), primary clarification to settle solids, secondary biological treatment—most commonly activated sludge or biofilm processes—to degrade organic matter and remove nutrients, and sometimes tertiary treatment such as filtration and disinfection (chlorination or UV) to meet discharge standards. Some plants include constructed wetlands or lagoon systems, especially in smaller communities. Nutrient removal strategies target nitrogen and phosphorus to prevent eutrophication.

Sludge generated in the process is thickened and treated separately, often by anaerobic digestion to produce biogas, which can be used for energy. Dewatering and drying produce biosolids suitable for disposal or agricultural use, subject to safety standards. Modern designs optimize energy efficiency, instrumentation, and automation.

In Finland and the European Union, wastewater treatment is regulated to protect aquatic environments, under national legislation aligned with the EU Urban Waste Water Treatment Directive. Municipal plants vary in size from small village plants to large urban facilities; ongoing modernization focuses on nutrient removal, resilience, and energy recovery.