EVOLUTION OF WASTEWATER TREATMENT IN FINLAND
This paper is based on several studies on the long-term development of water and sanitation services in Finland and presents the evolution of domestic wastewater treatment in Finland in the 20th century. It shows that the first phase of wastewater treatment development took almost 60 years; thereafter the systems expanded rapidly over two decades to cover all permanent habitation except for dispersed rural areas. During the last two decades, activated sludge with simultaneous precipitation has been the most commonly used method, and biological nutrient removal is now under development. In the future, a major challenge will be finding economically feasible methods and pracrices for removing loading from non-point sources. All in all, experience has proven the importance of undersranding and taking into account local conditions in wastewater treatment and its development under harsh, Nordic climatic condiuons.