Low Cost Sanitation in Tropical Slums

Outline

Background - Slums and Sanitation

Criteria for selecting sanitation technologies

Comparison of available technologies

Background: Slums

“unfit for human habitation”

“very poor”

“densely populated”

- Oxford English Dictionary

Definition:

Population increase by 58 million/year - due to rural-urban migration

890 million by 2020

Background: Slums 23 million people lifted out of slum conditions

every year (UN) A decreasing proportion of urban populations live

in slums

Background: SlumsWide variety: building materials, population density, layout, ground conditions...

Sanitation – diseases

Pathogens in excrement Transmission

Ingestion Insects Skin

Mosquito reduction important

Background: Sanitation

Objectives: Increased life expectancy Improved quality of life Poverty alleviation

Linked withHygiene educationWater supply

Selection Criteria

Health improvement Economic feasibility Technical feasibility Cultural acceptability Ownership Institutional support

Technologies

Focus: Pit latrines Simplified sewerage

Too expensive: Conventional sewerage Septic tanks Holding tanks & collection

Pit latrines: Features

Odour reduction Mosquito reduction Permeable walls $200 per unit

VIP Latrine

Pit latrines: Assessment

Cost effective Hygienic Independent of

institutional backing

Space issues

Ground issues

Water-table issues

Sullage disposal

Simplified sewerage: Features

Cheap version of conventional sewerage Narrower pipes Shallow gradient Peak flow used to clear pipes Shallower depth Fewer, simpler manholes Often combined with pour-flush toilets

Simplified sewerage: Assessment

Far cheaper than conventional sewerage

Excellent hygienically Cultural acceptability

Capital cost

Requires extensive institutional support

Sewage treatment required

Cost comparison

Source: D. Mara, Leeds University

Simplified sewerage is cheaper at high population densities

Conclusions

Slum populations are increasing due to rural-urban migration

Low cost sanitation technology plays an crucial role in improving the conditions of slum inhabitants

Sanitation must be designed to suit local requirements and implemented in conjunction with health education

Conclusions

Simplified sewerage Very high level of sanitation Most cost effective if widespread take-up

Pit latrines High level of sanitation Feasible with less institutional support

Questions?

Technologies – Toilet Design

Hole in floor

Healthimprovement

Economic feasibility

Cultural feasibility

Technical feasibility

Cistern-flush

GOOD POOR GOOD POOR

Pour-flush

GOOD VARIABLE GOOD VARIABLE

No-flush

VARIABLE GOOD POOR GOOD