Sewage and sustainable development

Can sewage treatment systems be financed sustainably when the poor cannot pay for drains? One option is to market the water and material in sewage for industry or as soil conditioners, even methane for electricity. And there other alternatives.

Some principles, however, are common to all kinds of wastewater treatment, whether domestic human or animal products:

• Complete treatment on-site wherever possible
• Consider retaining or constructing wetlands to provide treatment services, including removing pathogens, "for free"
• But be careful – assimilation capacities of natural wetlands are limited and poorly known. Creating artificial wetlands, however, can increase the extent of coastal wetland habitat, now widely threatened.
• It is usually best to treat domestic and industrial liquid waste separately