Tuesday, July 7, 2009

Stamford's Sewage treatment Plant

It is a very well run operation. This last year they received a million dollars in Tax credits for their managing the effluent so well. The Nitrogen discharge is under 1 mg/L with its methods and usually about 0.1 or 0.2. This is some contrast to the normal Nitrogen (as Nitrate) levels that are found naturally in The Sound (0.58 mg/L).
So part of the study Art Glowka and I are undertaking is to see how the treatment plants effluent is absorbed.
The test case was Stamford's Plant and the numbers were very typical of something clean.
The first 2 samples, going up the discharge point were typical of Long Island Sound Water. No Phosphate, no Nitrite Nitrogen and a Nitrate Nitrogen around 0.52 to 0.55 mg/L
Because this was much closer to shore, there were bacteria. In the furthermost sample, no Total or fecal coliform and 2 colonies/100 mL of enterococcus.
The second sample, which was near the break wall, had 20 Total coliform colony forming units in 100 mL of sample, 5 of which were fecal coliform, all 5 proving to be E. Coli. There were 47 enterococcus colonies per 100 mL, probably due to water fowl at the sampling point.
The next sample was interesting, the Nitrate level dropped to 0.436 mg/L, but no measurable nitrite or phosphate. This was near Dyke Park. Total coliform levels were still at 20 CFU's per 100 mL with 14 being fecal coliforms, all confirming as E. Coli. Enterococcus bacteria levels were at 14 CFU's per 100 mL.
The last sample was only a short distance from the outfall (50 meters) and was a surprise.
phosphate was measurable at 0.389 mg/L
nitrite nitrogen was measurable at 0.004 mg/L
and Nitrate was 0.823 mg/L
total coliform CFUs/100 mL by membrane filtration (m-Endo) 90
fecal coliform CFUs/100 mL by membrane filtration (m-TEC) 25
enterococcus CFUs/100 mL by membrane filtration (m-EI) 35
Escherichia coli CFUs/100 mL by membrane filtration (m-TEC) 20
These are the results down stream of the best sewage treatment plant in the area.
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