Alternatives to waterborne sanitation – a comparative study – limits and potentials

T he study analyses the potentials and limits of alternatives to waterborne sanitation. It is based on a comparison of a waterborne sanitation (WS) to a dry sanitation solution (DS). One very important point is that the introduction of a UDDT (urine diversion dry toilets) solution enables a water provision for 50% more inhabitants. A very important aspect for the situation in Peru which is heavily affected by the climate change, coming to a sharp decrease in water availability in the future.

A cost comparison is carried out which compares a situation of 10.000 households. The comparison is done from the point of view of a sanitation company, as the authors strongly believe that only an organized municipal sanitation service (which could or not be privately operated) can assure a sustainable solution. On the company side the necessary investment for the WS is about 1038 – 1227 USD per household. The DS comes to roughly estimated 935 USD per household.

On the management side a service model is proposed, in which the sanitation company recollects the dried feces and the urine every three months. The operational costs include transport, handling in a central plant, administration costs and education costs. Based on the actual water tariff in Lima (per m³) an advantage of 1 USD/month for each household is calculated.

In total a very clear advantage for the DS can be shown and therefore it is more than necessary to implant large scale solutions in order to be able to optimize the proposed systems.

The comparison does not take into account the economic advantages which could be generated by selling the urine. Based on the price for fertilizer in agricultural use in Lima and surrounding cities this saving would be about 20 USD/household,a for the urine. In the authors view the marketing of the products should not depend on the sanitation company but on agriculture organizations. An additional desert area of 160 ha could be irrigated by using all saved or treated water in the DS model.

[Paper to be presented at the IRC symposium Sanitation for the Urban Poor, Delft, The Netherlands, 19 - 21 November 2008]