Tell me about the sewer

[spingears]

@Polycarp

Spingears, I agree that “sanitary sewer”

Intended as a joke, ie. an oxymoron if you will.

I worked in the utilities dept. of a large research facility to generate and/or deliver compressed air, electric power, gas, steam, water for “sanitary” and process use, and maintained steam stills to provide double distilled water to chem labs.

The effluent from a well run sewage disposal plant should be of drinking water quality. It is usually discharged in to streams, you don’t dare to drink from, to be scooped up downstream and run thru the municipal water treatment plant to provide drinking water to a town or another facility.
The facility originally used septic tanks and a sewage plant was the result of pressure from the feds.

[robby]

@NinetyWt

Actually, since enforcement of the Phase II Stormwater regulations (part of the Clean Water Act) began a couple of years ago, cities are now being required to “treat” their stormwater before discharging it. Both new construction and existing development are included.

Look at your state’s DEQ site and search for “best management practices”. This details all of the things one can do to lessen the pollution in stormwater discharges.

Since governments in my area already require stormwater detention facilities to knock the peak off of stormwater flows, it makes sense to modify the design of the outlet structures so that they also function as settling basins.

In tight spots, grit- and trash-separating chambers can be installed at each inlet. For an example, I give you the stormceptor.

Slowly, you will see these regulations expand so that one day the treatement of stormwater will be commonplace.

To follow up on this, regulations for new construction generally require that the “peak flow” of runoff from a construction project not increase when compared to that before construction.

For example, suppose I have a project where I am taking a 10-acre grassy parcel, and replacing it with a large parking lot. Before the project, much of the rainfall infiltrated into the ground, and only a small amount ran off the property into the storm drain system downgradient of the property. After paving the property, I now have a great deal of runoff to deal with when it rains, since it can’t percolate into the ground like it used to. This runoff could cause serious problems for people downgradient from my parking lot, potentially flooding out them out.

The solution is to pass regulations prohibiting me from increasing the peak rate of flow from my project, when compared with the initial conditions. To meet the regs, I have to store all of the water that runs off from my parking lot, and slowly dribble it out into the drain system. Water is store in two basic ways: 1) aboveground in retention/detention ponds; or 2) belowground in tanks or galleries. Many, many parking lots have elaborate stormwater storage systems installed beneath the parking lot.

@NinetyWt

Interesting aside: Poly is correct in that most “combined” systems are considered a no-no, and many cities have spent oodles trying to separate stormwater from wastewater. However, one city discovered that by continuing to treat the stormwater as well as the wastewater, they could satisfy their Phase I and II stormwater requirements better than if they had implemented Best Management Practices.

This is generally not an option due to the high expense of treating water at a wastewater treatment facility (WWTF).

[NinetyWt]

@robby

To follow up on this, regulations for new construction generally require that the “peak flow” of runoff from a construction project not increase when compared to that before construction.

Right. The OP seemed more concerned with water quality than water quantity.

This is generally not an option due to the high expense of treating water at a wastewater treatment facility (WWTF).

Agreed. I mentioned this to point up the fact that sometimes the best environmental solution is not the one we’ve been accustomed to using.

[BrainGlutton]

Life is like a sewer.

What you get out of it depends on what you put into it!

– Tom Lehrer

[Tim_T-Bonham.net]

@Una Persson

OK, a wastewater engineer who I just phoned here at work tells me that in the EC, there are some cities that have separate systems using crude settling ponds/basins and gravel beds to catch debris, but he does not know of anything in the US like that.

In Minneapolis, the city recently finished a project which effectively recreated wetlands near a lake (the original ones were filled in decades ago when the lake was dredged to make it deeper) and then redirected some stormwater drainage systems into these wetlands. So the water goes there, and is somewhat filtered naturally before it reaches the lake itself, or the connnecting creeks.

On the other hand, a recent newspaper story from the same area reported that a park visitor found a moneybag full of checks from a local church floating on the lakeshore. Apparently a thief took the cash from the bag, and then threw it into the drain gutter at a street corner. From there it flowed thru the drainwater pipes and ended up in a lake, within only a couple of weeks of the robbery. (The bag still contained all the donations made by check; the church was able to dry them off and deposit them!)