Jätevesipuhdistamoilla

Jätevesipuhdistamoilla, known in English as wastewater treatment plants, are essential facilities for treating sewage and other wastewater before it is discharged into the environment. Their primary goal is to remove pollutants and contaminants to protect public health and aquatic ecosystems. The process typically involves several stages.

The first stage is pre-treatment, where large solids are removed through screening and grit removal. This prevents damage to downstream equipment and removes heavy materials like sand and gravel. Following pre-treatment, primary treatment involves settling. Wastewater flows into large tanks, allowing suspended solids to settle to the bottom as sludge, while lighter materials float to the surface as scum.

The next stage is secondary treatment, which is primarily biological. Microorganisms, such as bacteria, are used to break down dissolved and suspended organic matter. This is often achieved through aeration tanks where air is pumped in to provide oxygen for the microbes, or through trickling filters where wastewater passes over media covered in microbial growth. After biological treatment, a secondary settling stage separates the sludge containing the microorganisms from the treated water.

Tertiary treatment, if implemented, further refines the wastewater. This can involve processes like filtration, disinfection (using chlorine, UV light, or ozone), and nutrient removal (nitrogen and phosphorus). Nutrient removal is particularly important to prevent eutrophication in receiving waters. The treated effluent is then discharged, and the removed sludge is typically treated further, often through dewatering and digestion, before being disposed of or repurposed.