When you hear the words “remote sensing”, what do you think about? Drones taking pictures of streets? Spy satellites?
The chances are that if you’re in the clean technology field, you’re thinking about land use and land cover, mapping crop productivity, estimating water accessibility, monitoring air pollution - all very typical cases where data from satellites, drones, UAVs and cameras are used to observe environmental conditions and make predictions.
But, what about wastewater?
Now wastewater is typically the poor cousin of the water sector - we all need it, but we’d much rather not think about it at all! But it’s really important and as we’ve seen recently, can be used for more than just waste disposal. Right now, cities and countries around the world are monitoring wastewater to detect the spread of Covid-19. So far, sampling methods have focused on collecting traditional grab samples at the wastewater treatment plant or at other inlets in the sewer system. However, there’s increased interest in developing sensors that can monitor the system remotely at different points - though what that will finally look like is anyone’s guess right now.
Some scientists have started thinking about using paper-based sensors to test sewage for SARS-COV2, instead of the more expensive, lab-based PCR tests. Think of it as a kind of litmus test - if you drop the paper into the intake point or pass a sample through it and SARS-COV2 is present, it will show up as a clear, visual mark.
Paper-based sensors have been developed in the laboratory in the last few years to test a range of viruses from malaria, HIV and Zika to rotavirus, salmonella and E.coli In these sensors, different areas of the paper are printed using a wax printer so that different processes (extraction,enrichment, purification, elution, amplification, and visual detection) that are necessary to detect DNA material are integrated. The entire testing process is completed by folding the paper in different ways in different steps, similar to origami, so that there’s no need for a pump or power supply. These sensors were reported to be able to detect close to 98% of infected individuals in the case of malaria in Uganda and to have similar efficiencies for other viruses in other countries.
So, these paper-sensors can form the basis for an inexpensive, large-scale surveillance system for public health. But how can they be monitored remotely?
Usually, wastewater discharges to oceans and rivers have been monitored remotely using satellite data to track changes in the water systems. It may be difficult to track changes in sewer systems and wastewater treatment plants using satellites - however, with high resolution satellites like the ones deployed by Planet, it may be possible.
Another option would be to think about a combination of remote observations and image detection. For example, in the case of these paper-based sensors, we could start thinking about the sensors being placed at strategic locations together with cameras that can capture the image on the sensor and an image detection algorithm that can identify whether or not the SARS-COV2 detection mark is there or not. Maybe, even robots equipped with these sensors could periodically traverse the sewer system so that images could be sent back?
While this is not a typical remote sensing problem, you can see how combinations of computer vision, sensors and remote operations can transform the wastewater industry, among others. And this transformation is likely to be sped up because of the pandemic and the need to develop novel methods quickly and effectively.