This is a Sewage Pump Station Pt.3
The wastewater plant pump station from my earlier posts (one here, two here) has been in service, continually pumping raw sewage, for about 9 months now. Below are some of the more visually striking images I could find from inside the completed underground structure. Unlike the photos in earlier posts, I didn’t take most of these. Image credits, except for the last one, belong to Hazen and Sawyer.
Upstream face of pump station. Once all flows combine in the main sewer junction box they come down these dual influent lines into the pump station structure. The inside diameter of these influent lines is 5’- 4”. After we built the deck slabs over the pump station we had to walk through these pipes to get in and out (the access steps were built in the junction box where there was no deck slab).
Still looking to the upstream side of the pump station. This is one of the three ‘screenings’ channels you can make out in earlier photos looking through that intermediate part of the earth work. Later we install huge mechanical raked bar screens into these channels. Those are what they sound like. Moving rakes on the machines bring undissolved solids greater than 3/8” diameter up to the surface and into a compactor. If you’ve ever been on a school field trip to a wastewater plant, you’ve probably seen the top end of one of these machines (and the condoms, “flushable” wipes, and hair balls it brings with it). Usually the most stomach-turning part of any visit to a wastewater plant.
This is in one of the wetwells, looking up at two set of strut beams (remember, really columns laid on their side, taking some of the earth load off of the walls). Taken before any piping went in. I think I mentioned in the first post how eerie it can feel when you’re 50-ft underground. Well, inside one of these wetwells, with the hatches closed and in the dark, it can really unnerve you. Dark damp cavernous spaces are not for me I guess.
At the bottom of the wetwells the floor is sloped and filleted to the position of each eventual pump. The pump intakes sit right above these finned cones (anti-vortex cones). To accommodate variable incoming flow rates, this wetwell has one small pump, capable of about 5,000 – 9,000 gallons per minute (gpm), and three larger ones each capable of handling about 8,500 – 17,000 gpm. Smaller one will mount at the left-hand side of this photo, the three larger ones beyond. The larger pumps, with their motors, stand over 8-ft tall.
Image on left is pump discharge piping (24”) rising up from where we were looking in the previous photo. The set of smaller stainless steel pipes strapped to the discharge pipes are guide rails for the submersible pumps. With the help of a crane, the pumps can be pulled out of service, ride up these rails, to the top for maintenance. After our personnel leave the wetwell and open the sewers, no human will ever be down here again (hopefully anyway, for their sake). Image on the right is one of the 6-ft wide cast iron sluice gates mentioned in previous post. These allow or disallow sewage into any particular wetwell.
Back upstream in the screenings channels. Including these because I like how they look—'cathedral of shit’ comes to mind. Clips on the walls to the left will bracket the mechanical bar screen equipment in place. Middle channel in right-side image is really an emergency bypass channel; main channels are on the left and right. A quick note about the whitish paint. This is not to make the place look nice. The cathedral of shit will not be white for long. This is an epoxy barrier coating protecting the concrete from sewer off-gasses. Concrete can stand up just fine to liquid sewage, but the acid gasses given off by the bacteria in our waste will slowly weaken and decay concrete. So anything in a concrete structure, above the low liquid level line, must be coated with a microbiologically-induced-corrosion inhibitor.
One more. The view from above a nearly finished pump station. The four pump discharge lines from each wetwell turn horizontal and run through the sunken vaults on each side visible here. In these vaults are check valves, motor op open/close valves, air release valves, as well as some instrumentation. The squarish building stores the compacted refuse from the bar screen equipment. On the far left of the image you can actually see most of one of the mechanical bar screens that will get dropped into a screenings channel.
There’s more, but I won’t bore you. You have now seen a sewage pump station. And that is probably more wastewater infrastructure than you ever wanted or needed. But this stuff is important. Our cities couldn’t function without this. Without this you wouldn’t be able to get even close to a river, much less get on a kayak or go fishing (actually the fish would mostly be dead anyway). I’ll end this the way every Environmental Engineer likely would. Like it’s required by a code of ethics or something. So to keep my cred: Don’t flush flushable wipes; don’t flush unused medications; and for the love of god, don’t wash anything more than tiny incidental amounts of grease or oil down the sink. TP poo and pee only please. OK thanks, bye.