Sewage is wastewater which contains human excreta (feces and urine), laundry waste, and often kitchen, bathing and other forms of waste water too. It is highly pathogenic, meaning that it contains many disease causing organisms.

Globally around two-thirds of the World’s urban dwellers rely on on-site (on-plot) sanitation. At the same time there is an increasing trend towards replacing on-site sanitation with traditional sewerage systems. Millions of dollars are spent on building sewers and sewage treatment plants while the complementary investments in household sewer connections and toilets are often neglected. What will those municipal investments in sewage treatment achieve without house connections?

A recent study from the World Bank’s Water and Sanitation Program (WSP)examined sewerage projects funded by different agencies in 12 cities of Indonesia and Vietnam. The study found that most sewerage projects focused on the ‘large investment items’ – trunk sewers and sewage treatment facilities – with scant attention, plans or investment in tertiary street drains and sewers or the house connections to collect the wastewater from homes. Unfortunately the sewers were found to collect vast amounts of storm water in the wet season and with little fecal contamination flowing into the sewage treatment plants. In these cases the sewage treatment plants are receiving not much more than ‘dirty water’ – with negligible benefits to public health and the environment. The household fecal wastes remained mostly untouched and uncollected – under or nearby to the home or local drains and waterways – when they should have been connected and removed by the new sewers and delivered to the plants for safe treatment and disposal.

The lessons learnt? That policies, strategies, plans, designs, and financing mechanisms always need to include the ‘last mile connecting infrastructure’ so that households connect to the sewers and transport it to plants for treatment. Reactions to the study from governments and development agencies have been that the findings are a ‘wake-up call’ and changes to the scope of existing and planned sewerage projects to include the tertiary sewers and house connections have already been made in Vietnam. But what do these findings mean for other countries and regions? Do the same lessons learned apply elsewhere?

This post first appeared on The World Bank Water Blog.

Publication does not imply endorsement of views by the World Economic Forum.

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Author: Isabel Blackett is a Senior Sanitation and Water Specialist for the World Bank Global Water Practice – Water and Sanitation Program

Image: A worker cleans a recycled toilet bowl. REUTERS/Romeo Ranoco