You may have recently seen Bill Gates drinking water distilled from human faeces. It was on the BBC, and all over the Web -- you can watch him do it if you are not convinced.
And truly, the Omniprocessor machine that his Foundation has helped develop is an inspiration to all of us sanitation engineers. It's a vision for the future where everybody has access to sanitation, and faeces can become a cheap and convenient source of fertiliser and energy.
Where does YOUR water come from?
You may not know it, but there is a good chance that you, too, have already been drinking water that has been - at least partially - recycled from wastewater.
If you live in London, and enjoy a view of the river Thames from which much of your drinking water comes, remember that Windsor, Reading and Oxford are just upstream, and so are the sewer pipes of their inhabitants. This is something to ponder next time you turn on the tap.
We in London do not fall ill from this thanks to the development of treatment plants and good sewerage systems. WaterAid is uncovering this story in our Big History project, tracing how the UK's cities have become healthier, cleaner places since the advent of sanitation.
Not just toilets
Gates's famous drink is also a healthy reminder that sanitation does not stop at toilets. In places where expensive sewers cannot be installed, toilet pits are dug, and must be emptied. The resulting sludge must be transported, treated and hopefully reused.
Emptying the sludge is usually the first hurdle, as recently shown by WaterAid's experience in Tanzania. Despite large investments in treatment machines, we are still relying on a £200 'Gulper' pump to empty these pits, as other options are simply too expensive for most residents of poor urban settlements in Africa and Asia.
WaterAid Tanzania staff demonstrate the Gulper hand-operated pump for emptying latrine pits in Kigamboni, Dar es Salaam, Tanzania. Photo credit: WaterAid/Jake Lyell
Affordable and appropriate solutions
The Omniprocessor may provide a solution in urban areas where some sanitation exists. But we are still researching options for toilets, pumps and treatment systems that are affordable for the poor, and appropriate for smaller towns which cannot afford complex systems. In Bangladesh, we are developing drying beds for compact sludge from toilet pits; in Pakistan, our engineers are improving septic tanks in slums.
More complex machines such as the Omniprocessor do have their place, especially in larger cities, and I hope this invention draws interest from African and Asian municipal engineers and planners.
But that glass of water I am drinking in London also reminds me of something else: I do not know - or much care - how my water has been treated, but I trust that the water company and its regulator have done their jobs well. Ultimately, whatever the technology, we must make sure that governments fulfil their role: to help deliver services for all, especially those hardest to reach, and to make sure we can trust these services are functioning well when we turn on the tap.