Sanitation for all in periurban areas? Only if we use simplified sewerage

Simplified sewerage is considered the only periurban sanitation technology that has a chance of ensuring that the WHO/UNICEF target of Sanitation for All by the end of 2025 is achieved. On-site sanitation technologies, such as ventilated improved pit (VIP) latrines, pour-flush toilets and ecological sanitation toilets, are either technically infeasible in high-density areas or more expensive than simplified sewerage. Simplified sewerage is often institutionally and professionally acceptable to sewerage authorities simply because it is a sewerage system, albeit different from conventional sewerage in that it uses small-diameter sewers laid at shallow gradients (e.g., 100-mm sewers at 1 in ∼200). The success of simplified sewerage in Latin America, principally Brazil, has to be replicated on a truly huge scale in Africa and Asia where most of those without adequate sanitation live. In areas where even simplified sewerage is unaffordable, the only option is to install communal sanitation blocks of the type implemented in India by Sulabh International.