clean water sanitation resource-based economy Kadagaya


The water infrastructure in most cities today provides a single potable water supply which is used for drinking, bathing, washing clothes and dishes, watering gardens, etc. It is unnecessary and wasteful to be flushing toilets with drinking-quality water and it is more efficient to have several grades of water for different purposes. Three main grades can be classified: (1) drinking water – high-quality clean water with acceptably low levels of pathogens, salt, and toxic chemical; (2) grey water - household waste water (e.g. from showers, washing clothes, and cooking) that does not contain faecal matter; and (3) black water - waste water from toilets that contains pathogens. Waste water from workshops and laboratories may require additional treatment due to contamination with e.g., heavy metals and industrial chemicals. Thoughtful design of the water network and material that enters the waste stream (e.g., detergents) is important to maximise efficient water use and facilitate recycling and re-use.

The campus location (in a tropical region of Peru) has access to water from a nearby river and plenty of rainfall. Rainwater is the cleanest source for drinking and is collected in tanks from the rooves, then pumped to header tanks for gravity feeding to the buildings. Currently, rainwater is exclusively used for all purposes. However, in the future, it will be used only for cooking, drinking, and personal hygiene. For washing clothes, cleaning, and agriculture a lower grade of water can be used (e.g., river or recycled water). We have several stages of purifying the rain water. First, mesh filters and a “first-flush” system prevents leaves and other debris from the roof entering the tank. This water is then passed through ceramic filters before being collected in the header tank. Both the storage and header tanks have submerged UV lights to kill bacteria and viruses (and prevent fungi growing in the tanks). These methods produce potable water without the need of chlorine or other chemicals.

We have constructed one small grey water processing system for the existing house. This consists of a two-stage underground tank that allows slow sedimentation of the particulates in the water. The cleaner water passes from the top of the tank into a retention pond where the water is filtered and cleaned by natural biochemical processes. A variety of water-loving plants were selected for cleaning the water and the pond is landscaped to be an attractive feature of the garden and look like a natural part of the environment. In the case of larger ponds for future buildings, we will be evaluated if bamboo and other technical materials (for construction etc.) can be planted in these ponds as they have high water requirements.

Another important aspect of water management is suitable drainage and rainwater management as we have very high seasonal rainfall and it is important to avoid flooding. This is especially important as dirty water and poor drainage are major disease factors (particularly with respect to mosquito-borne diseases in this area). Human waste from toilets is currently being collected in composting latrines. In the future, toilet waste will be collected in a bioreactor for producing methane gas (for cooking).