Water samples were filtered through a 0.45 μm filter paper after which strong HNO3 (or HCl when measuring Ntot) was added to them and they were refrigerated. Elementary analyses of SSW using ICP-OES and XRD analyses of EC sludge (from SSW test runs) were conducted at the University of Oulu. All analyses of the real wastewaters were conducted at an accredited test laboratory – Ahma ympäristö Oy, Oulu.