This strategy has been successfully applied over many decades in densely populated areas of industrialised countries and contributed to a great extend to an "out of sight, out of mind" system of hygienic conditions for these regions.
However, the appropriateness of this model in the context of expanding urban environments must be questioned on a number of key points.
During the last decade, various researchers and institutions, including the World Bank, have started to consider the decentralised wastewater management approach as an alternative to conventional centralised systems.
It is the following important issues that Kuma Decentralised Wastewater systems were designed to address;
- Eliminate the need for monolithic investment programmes.
- Grow the systems in line with the start-stop nature of urban development.
- Ensure a governed, affordable cost per capita.
- Take advantage of technology developments in wastewater treatment as they occur.
- Return wastewater to resusable water in less than 24 hours.
- Eliminate any chance of total system breakdown.
- Adopt a 2 phase process of safe resuable and/or potable water.
- Place the decentralised stations where they can do the most good.
- Accomodate decommissioning where neceassary.
- Ensure economical running costs by eliminating the need for large scale pumping.
The main arguments against decentralisation of wastewater management are based on financial concerns and issues of treatment efficiency.
Our reserach has proven time and time again that at worst we are on a par with the cost per capita, and in many cases can prove to be as much as 75% less capital intensive.
Why choose a decentralised approach?
Apart from its proven benefits, the centralised wastewater management system is nothing else than a transportation system for human excreta and industrial wastes to a central discharge place or a treatment unit.
This requires the use of valuable drinking water as transport medium, these systems are wasteful not only of water but also of human waste elements that can be easily treated and reused in an effective decentralised strategy.
Centralised wastewater management systems hamper wastewater reuse opportunities and increase the risk to humans and the environment in the event of system failures.
Importantly, the decentralised wastewater management concept is better suited to translate Bellagio Principles No 3 (perceiving human excreta and wastes as potential resources) and No 4 (solving sanitation issues as close as possible to the source of waste generation) into practice.
Furthermore the decentralised wastewater management concept broadens the technology options and permits;
Tailoring the solutions to the prevailing conditions.
Minimise the freshwater requirements for waste transportation.
When installing networked stations, reduce the risks associated with system failure.
Increased wastewater reuse opportunities.
Permit incremental development and investment in the communities wastewater system.
A copy of the Bellagio Principles is available from the International Institiute for Sustainable Development here >>
