Public Lab Wiki documentation


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Wastewater is “used water” that’s created by households, cities, and industry. It ranges from sewage to surface runoff that can flow from roadways into storm drains. Untreated or under-treated wastewater can contain a variety of pollutants that can harm people and ecosystems when it’s released into the environment.

On this page, we’re collecting information on some of the clues that might indicate wastewater pollution in the environment, and ways to investigate them. Some methods assess general water quality conditions that can correlate with wastewater pollution, while other methods can more directly signal the presence of wastewater by identifying specific pollutants.

Detecting possible wastewater pollution

There’s lots of information (in English and Spanish) about what to look for in the comments of this question: What are some observable tell-tale signs of wastewater pollution?

Change in water color or clarity

Why? Solid particles, chemicals, or microscopic organisms in wastewater can give it a color or cloudy appearance. When wastewater is discharged into the environment, you might see a discolored plume in a river or a colored residue on land.

turbid wastewater in a stream

Cloudy looking stream water, Sustainable Sanitation Alliance, CC BY


Documenting visual changes in water color or clarity

NYC Flushing Bay CSO

Satellite image showing discolored, cloudy water in the Gowanus Canal. From this slideshow by @eymund.

Documenting changes in water color/clarity with spectral imagery (might not be visible to human eyes)

Gowanus plume

Visible and near-infrared photos composited to reveal a plume of flowing sewage scum, originally from this note by @liz.

Measuring turbidity of water

Solid particles floating throughout the water (called suspended solids) increase its turbidity. Learn more about turbidity in this research note from @anngneal.