Page - 85 - in Clean Water Using Solar and Wind - Outside the Power Grid

Used water treatment 85 Urine is an important source of sustainable nutrients and is usually less  contaminated than water containing faeces. It is a major contributor to nitrogen, phosphorus and potassium and can be an excellent fertiliser. Urine must be separated from faeces, which can be used for biogas production. Urine can be stored in a tank until it is needed for agriculture; and if it is stored for a sufficiently long time it becomes hygienised and safer for agricultural use (WHO, 2006). Storage space may be available in remote areas but more difficult to come by in urban or peri-urban areas. A storage tank will need pumping capacity and the maintenance demand should not be underestimated (Tilley, 2013). Greywater is often a source of many pollutants, an overview of which is presented by Friedler et  al. (2013). High concentrations of organic substances come from the kitchen sink. Typical components are food residues, oils and fats, detergents and drain cleaners. Greywater from washing usually contains shampoos, soaps, preservatives and dyes. The water may also contain some heavy metals like zinc and copper from in-house plumbing. Faeces and blackwater contain high concentrations of organic matter and are useful sources of bioenergy. Anaerobic treatment is a method of extracting the inherent energy and producing biogas. Particular attention should, however, be paid to hygiene; pathogens must be reduced or eliminated. Naturally, separating the used water into different categories for separate treatment increases the complexity of the process but it is an important way to save precious water resources. 7.2 TREATMENT OF USED WATER Today there is a wide spectrum of methods and processes available for small-scale treatment of used water. On top of conventional methods there are treatment technologies developed for specific products. However, not only do technologies have to be implemented, but financing and business models should be considered as well, as pointed out by Tilley (2013). It should be emphasised that no particular technology is necessarily better than another. The key point is the relevance of the technology for the local conditions and how its users are motivated to manage it. Here we describe major technologies that are sufficiently Downloaded from https://iwaponline.com/ebooks/book-pdf/520710/wio9781780409443.pdf by IWA Publishing user