Options for alternative types of sewerage and treatment systems directed to improvement of the overall performance

Abstract

Technology for future houses may well include a high-tech water recycling unit that makes tapwater while people drink bottled water of high quality. There may be toilets that produce just a bag of dry fertiliser per year, hopefully without fossil energy. Rainwater infiltration is increasingly replacing storm sewers anyway. Many urban areas of the future could simply be without sewerage systems. Technical feasibility is given even today and economic feasability is coming closer by advances in membrane technology. However, there are more likely scenarios than this. One person produces about 500 litres of urine and 50 litres of faeces per year (= blackwater). The same person, produces in a range of 20,000 to over 100,000 litres of wastewater. Black- and greywater (wastewater without toilet) do have very different characteristics. If blackwater is collected separately with low dilution it can be converted to safe natural fertiliser, replacing synthetic products and preventing spreadout of pathogens and other pollutants to receiving waters. New sanitation concepts are now built in several countries as pilot projects. One example is a vacuum-biogas system for around 400 inhabitants that has been built in Lübeck, Germany. It does perform recovery of resources and energy in an urban area. This type of sanitation can serve around up to 10,000 people and can be arranged in independent modules for larger settlements. Another pilot project based on urine-sorting flush toilets (no-mix-toilets) has been built in the rural water-mill museum “Lambertsmühle” near Cologne, Germany. Urine or yellow water is collected with low dilution and can be used as fertiliser as projects in Sweden have shown – the nutrient composition suits many types of soil. Brownwater (the solids and flush from the sorting toilet) is converted to small volume by a two-chamber composting tank with a filtration system. The compost can be used as soil conditioner. These and other concepts can be economic and show new ways for the many water scarce areas around the world, too.