I operate a wastewater plant in Mich, thought some might interested in how it relates to the residential end. My system usues both gravity and pressure systems. Most towns use gravity, the house is connected to the sewer main with 4″pvc, the mains run to pump stations which are large concrete wetwells containing 2 pumps, most of the time only 1 pump is used and they alternate, if flow dictates both pumps will run, they are controlled by floats which turn them on at diff. intervals. Sewage is pumped to the plant from pump stations. If a batroom is in a basement lower than the sewer main we use a grinder pump system, which is basicly a small pump station, the house is plumbed into this small unit and sewage is pumped to the main line.
Pressure systems use individual pumps at each residence and can pump sewage a great distance with ease, my longest pressure system is 6 miles from the plant. They use a regular concrete tank, sewage is plumbed to the tank as in regular systems, a small pump chamber sets in the other end, when floats turn the pump on sewage is pumped through 1/1/2 pvc line, check valves protect each unit from back presssure. Each pump provides the pressure to move the effluent to the plant. www.orenco.com has a good overview of how these work.
My plant uses aerated lagoons, basicly 3 ponds 2.25 acres each by 12ft deep, water enters and is biologicly broken down, after lab samples water is dispersed through irrigation rigs, we lease the fields to farmers for corn, oats hay ect. We use a myriad of sampling so the end product is basicly clean water that gets sprayed on the fields. Any questions?
Thanks, Alan
Replies
thanks for the lesson. So in a pressurized system a pump can pump the sewage 6 miles away?? Thats a LOOOOONG ways to pump poo.
Do sewer lines have the same pitch as ones inside a house? Like 1/4" per ft. If so then some sewer lines must be pretty deep.
thanks
the pressurized system uses each pump to move the sewage, they are 3/4 hp, the line has approx 20 lbs press. And yes the gravity mains have very little fall, some are 20 ft deep.
Alan
You mention that the water is "...biologicly broken down..."
What exactly does that mean? What kind of treatments are used to make the water clean?
Practice safe eating - always use condiments.
Boss,
It is bacteria that attacks the raw sewage, we use aerators that pump oxygen in the ponds, top layer is aerobic, in that they need oxygen to work, lower is aneroabic, which neds no oxy. Really works quite well, there is some odor at the plant, but no where near what you would think.
Alan
About that biological treatment, here's some more info.
In a large treatment plant, like the Hyperion plant in Redondo Beach in Southern California, the sewage first goes into anaerobic digestors (no oxygen). Think swamp muck--and swamp gas.
The anaerobic bacteria break the organic solids down into simpler molecules, and produce methane in the process. There is some sludge produced, and this is composted. It makes a good soil amendment, but not for food crops (the heavy metals are concentrated in the sludge).
At Hyperion, enough methance is produced from this anaerobic digestion to fuel large reciprocating engines that run compressors for the next step, which is aerobic digestion. The compressed air is injected at the bottom of large open tanks, and another set of bacteria take over to "eat up" most of the rest of the organic matter. The extra methane is "cleaned up" and sold to the local gas company.
This two-step process is called secondary treatment, and produces an effluent that, after treatment with chlorine disinfectant, is fit for landscape and golf course watering, with no public health worries. And in So. Cal, that's what they do with some of the effulent. The rest goes out in a pipeline a few miles out to sea.
I used to work for a consulting company that designed and built industrial wastewater treatment systems. Visited Hyperion a few times. The main interceptor (sewer pipe) coming onto the plant was mammoth--something like 18 feet in diameter.
And like alan said, at a properly run sewage treatment plant, there's very little odor.
Cliff