There have been major fluctuations in the bacterial flora of Lake Mývatn, and one factor affecting the condition of the water and the ecosystem is waste water from nearby settlements entering the lake. A regulation on the protection of Lake Mývatn and the river Laxá requires sewage to be treated more thoroughly than with a two-stage cleaning process. A decision was taken on actions to improve the waste water situation at Lake Mývatn which involve separating black water (toilet sewage) from grey water (waste water from the bath, laundry and kitchen) and re-using nutrients in the black water for revegetation of the land reclamation area at Hólasandur. The project is carried out for the municipality Skútustaðahreppur, in collaboration with the Nature Conservation Agency, Landgræðslan. The municipality and project contractors will replace traditional water toilets with water-saving toilets that use 6-9 times less water than traditional toilets. Investment will also be made in closed tanks for the storage of toilet sewage, while grey water will be treated in the existing septic tanks and septic fields on the sites of each party. A storage tank is to be constructed at Hólasandur to collect the black water to be used as fertiliser in the summer in the area. This sewage solution is brand new in Iceland, but has been used in neighbouring countries.