tertiääripuhdistuksessa

Tertiary treatment, also known as polishing or advanced wastewater treatment, is the final stage in the wastewater treatment process. Its primary objective is to remove remaining contaminants that were not eliminated during primary and secondary treatment. This stage often targets specific pollutants that can cause environmental harm if discharged into receiving waters, such as nutrients, residual suspended solids, and pathogens.

The methods employed in tertiary treatment vary depending on the desired effluent quality and the specific contaminants to be removed. Nutrient removal, particularly for nitrogen and phosphorus, is a common goal. This can be achieved through biological processes like nitrification and denitrification for nitrogen, and enhanced biological phosphorus removal or chemical precipitation for phosphorus. Filtration is frequently used to remove fine suspended solids and improve the clarity of the treated water. Various filtration techniques exist, including sand filters, multimedia filters, and membrane filtration.

Disinfection is another crucial aspect of tertiary treatment, aimed at eliminating or inactivating pathogenic microorganisms such as bacteria, viruses, and protozoa. Common disinfection methods include chlorination, ultraviolet (UV) irradiation, and ozonation. Each method has its own advantages and disadvantages regarding effectiveness, cost, and potential byproducts. Tertiary treatment significantly enhances the quality of wastewater, making it suitable for a wider range of reuse applications, such as irrigation, industrial processes, or even as a source for potable water after further purification. The removal of residual contaminants also protects aquatic ecosystems from eutrophication and other forms of pollution.