Drain overflows
One of the most serious problems derived from the accumulation of grease in sanitary drains is sewer overflows. More than 90% of overflows are caused by FOG plugs.
The drainage of the Cities can be, in broad strokes, of two types: Combined, where sanitary water and rainwater come together and run through the same pipe and Separated, where the rainwater runs in different pipes than the wastewater.
The presence of grease blocks in either system causes unwanted overflow.
There are still more than 700 cities in the US that have combined systems and in Mexico, the vast majority have combined drains.
In dry weather, combined drains work by carrying rainwater and sanitary water to the Treatment Plant.
On the other hand, when the drains are separated, the rainwater will discharge into an aquifer with minimal treatment.
When there are heavy rains, the separate drainage system works in the same way, sewage to the WWTP, rainwater to the body of water.
But the combined system when the rains exceed the input capacity to the WWTP, allows the excess flow to be discharged untreated (with black, gray, hospital, industrial water, etc.) directly to the water body.
The photo on the left, shows an overflow of drainage water in a stream, you can see the difference in color and the amount of trash it carries. This effect can last for several days.
The photo on the right shows a warning sign on a lake stating that, in case of heavy rains, you should not fish or bathe, as the water body can eventually receive contaminated water.
The photo on the right shows a warning sign on a lake stating that, in case of heavy rains, you should not fish or bathe, as the water body can eventually receive contaminated water.
