Control Engineering

Peter Welander

Exactly how much sludge is there?
July 26, 2007

Going back to my posting from yesterday, I said I had done some cipherin' on how much sludge BP wants to put in the lake. If you go back to my posting of July 23, I link to Dennis Byrne's column where he makes this claim:

"Tiny dispersed solids, too small to be caught by the treatment's fine filters, do reach the lake; they are about 10 microns in size (1/25,000 of an inch.) The 20 million gallons of treated wastewater discharged daily into the lake is 99.999 percent water; the remaining 0.001 percent is mostly two kinds of salt -- chloride and sulfate -- and even tinier amounts of nutrients, organics and metals, most of which are found naturally in Lake Michigan."

Tiny percentages can add up to something real if you are talking about 20 million of anything. A gallon of water weighs 8.345 pounds, so 20 million gallons is 166,900,000 pounds of water. If we multiply that by the percentage above, the discharge consists of 166,898,331 pounds of water, leaving 1,669 pounds of particulate.

According to the article referenced in yesterday's posting, the new permit will allow BP to dump 4,925 pounds of suspended solids into the lake. Actually they can also include 1,584 pounds of ammonia, but we'll ignore that for the moment.

Let's say you live near the lake or other large body of water where you can look out your window and see the shore. Every day some guy drives up in his big pickup truck and starts dumping bags of concrete mix into the lake. If he dumped 20 bags (80 pounds each) into the water, would it get your attention? How about 60 bags? The permit allows the equivalent of 60 bags each day.

If somebody does that every day, the material is going to build up either as solids or in solution. Yes, Lake Michigan is big, but history has shown that process industries can move the chemical concentration needle more than we'd like, no matter how big the lake is.

Posted by Peter Welander on July 26, 2007 | Comments (0)