Analys av framtidens system för hantering av avloppsvatten och matavfall i Eskilstuna

Sammanfattning: Wastewater treatment is increasingly controlled by the Swedish environmental quality objectives, adopted by the Swedish parliament. There is a need for a sewage system that can fulfill stringent requirements concerning the environment, recycling and resource use and hygiene. Additional environmental aspects in recent years are the impact of climate change, new knowledge about the effects of pharmaceuticals in water, the need for improved wastewater treatment and increased recycling of nutrients to agriculture.   This report has, from a future scenario of the year 2050, analyzed seven different systems for wastewater treatment and treatment of compostable biowaste from households in Eskilstuna. A future scenario was chosen based on that within a forty year period new challenges may arise which can result in higher demands on sewage treatment than those we see today. Another reason why the future scenario was established is that changes in wastewater treatment systems are slow to establish.   The analysis is mainly focused on the economical aspects but environmental aspects such as emissions to receiving waters and potential recycling of plant nutrients has also been evaluated briefly. The economical analysis was made from a new construction perspective. The economy model is constructed in Microsoft Office Excel and named URWARE Eko. The report also includes a section based on results from previous system studies.   A target image of Eskilstuna 2050 was initially created. Seven systems were then analyzed based on this target image. The seven different systems could be divided in to three main categories: conventional sewage system that were modified, source separated blackwater systems and a sewage plant with improved treatment technology in the form of membrane technology and reverse osmosis.   The results showed that it differed a factor of 1.9 between the cheapest system (sludge recovery to productive land) and the most expensive (separated blackwater treated in a central treatment facility). All systems have a big recycling potential of phosphorus. Blackwater systems and wastewater plants with membrane technology and reverse osmosis are the best systems for recycling of other nutrients such as nitrogen, potassium and sulfur.