Stormwater Treatment Unit

[Bowne]

As part of a stormwater improvement project, which serves a local urban area, the New York State Department of Conservation is requiring that a pretreatment facility be installed near the drainage system's downstream end, just prior to its discharge into tidal waters. They are looking for some type of unit such as a Bay Saver, CDS, Stormceptor, V2B1, Vortechs, etc. Has anyone had any experince with any of these treatment systems and if so, what are your comments regarding their usage

 

[LHA]

It depends on the removal criteria. If there are none, or just a reduction in TS and O&G is required, I have used The Snout in the past. It is basically a hood over the intake end of the outflow pipe out of a regular inlet box. Grit drops out, O&G are held back.

You end up with a very deep (therefore, more expensive) inlet box. But O&M is just vacuuming out the inlet periodically...no parts to service or replace.

Again, this will not remove TDS, say, nutrients or salts. Make sure of what pollutant parameters must be addresssed.

 

[Bowne]

Iha,

Besides the NYSDEC requiring that a treatment unit be placed near the discharge end of the drainage system, they are also requiring "hoods" be placed over the outlet pipes located within each and every inlet/catch basin in the entire stormwater system.

 

[bltseattle]

Gary Minton has researched the effectiveness and requirements for "package" treatment units quite extensively. Try a google search for his name and "treatment", also see the link below.

http://www.engr.washington.edu/epp/cee/ntc.html

My opinion is that some of the systems may provide hydraulics better than a basic wet vault, but at the end of the day Stokes law of settling requires some amount of residence time for particles to be removed from the water column, so any system that fits in a manhole is hamstrung from the start. Smaller systems are much more likely to reentrain fine particles and hydrocarbons than a large system. Coalescing plate separators seem to be proven effective in many instances for oil/grease/grit. In Washington, Stormfilters(tm) seem to be the most widely accepted package BMP, because they provided monitoring/testing to gain state approval.