Your wastewater can reveal a lot about you, or at least about your neighbourhood: drug consumption, diabetes, resistance to antibiotics... and recently, COVID-19: based on rapid tests, you can potentially detect outbreaks as they happen, before data from individual tests. You can use this dashboard from Duke University, and this handy map by CovidPoops19.
Notice how this map only shows high-income countries? That's the problem with wastewater, which you can analyse only when you have a functioning sewerage system. As big as the field of wastewater-based epidemiology may be, it doesn't cover pit toilets, which contain faecal sludge: in that case, such data is harder to come by – you need to go and collect rather than use existing pipes and treatment stations. But this is also where such data could be even more useful, given the prevalence of faecal-oral diseases.
This didn't deter a team in Maputo from trying. In their recent study, they compared the pathogens in children's faeces and in the sludge from shared toilets. They found that, for bacteria (including salmonella and our good friend e.coli) and some parasites like giardia, there was a clear correlation, which means that you could sample faecal sludge from the pits to have an idea of whether such common diseases are prevalent in the area. It didn't work for viruses or worms, though.
If you find this area of work exciting, I strongly suggest that you take a look at their additional doc, which explains how they collected sludge samples, featuring a modified "Sludge Nabber"!
More information: Capone et al., Analysis of Fecal Sludges Reveals Common Enteric Pathogens in Urban Maputo, Mozambique
Spotted by: Joe Brown