The aforementioned aims can be achieved by source control in sanitation! Source separation of different streams of domestic wastewater helps to prevent pathogens from faecal matter to be spread in the Environment, utilizing nutrients from yellow water, and preventing grey water from being further contaminated with nutrients, faecal pathogens, and contamination with hazardous substances from industrial wastewaters making it a suitable source for being reused - even for high quality demand like groundwater recharge.

The issue of source control requires some special pre-requisites: separate pipes for yellow, brown and grey water, no-mix toilets for separate collection of yellow and brown water and low volumes for toilet flushing.

Generally, there are different options for source separation. A simple scheme would be the separation of grey water from black water, requiring two separate pipe systems in the home (one for grey water, one for black water). Low volumes of toilet flush water are helpful in further treatment of black water solids in order to sanitise them. For certain sanitation techniques (dehydration, composting), the black water solids have to be separated from the liquid phase. One possibility for sanitisation the entire black water is anaerobic digestion, which also offers the possibility of harvesting biogas.

The second option is to collect all three sources of domestic wastewater separately: grey water, yellow water, and brown water. This option requires three different types of pipes in the home (for grey water, yellow water, and brown water). In such a scheme, the excellent fertilizer “yellow water“ is collected very purely.

Source separation of different particular domestic wastewater flows (related to the nutrient as well as to the water cycle) facilitates sanitisation of human excreta as well as nutrient recovery from excreta – and also purification of the grey water stream.