Generally speaking, there are 2 different worlds with regards to wastewater tanks. Underground and above ground. Here are some things to consider with both options.
As much as I hate to say it, concrete is really the best and only option for an underground tank.
I’m a big fan of plastic and stainless steel in brewery wastewater applications, and plastic septic tanks are readily available. But plastic isn’t a good choice for underground brewery wastewater applications due to temperature ratings. Most plastic tanks are rated for no higher than 120F and brewery wastewater will get hotter than that. It will. It might not be a planned event, but valves will get stuck, things will overflow. A collapsed tank would be a big headache (and expense) because of something silly like a hot liquor tank overflowing.
Stainless steel in an underground application is surely cost prohibitive unless you use a used tank. But how many used tanks do you think you’ll find that are rated for direct burial? Right… Concrete it is.
The thing I don’t like about concrete is susceptibility to corrosion. In a brewery wastewater application, most corrosion will occur above the water line. This is due to hydrogen sulfide gas and water vapor combining to make sulfuric acid. So a liner is mandatory, not optional. A urethane coating is fine, it can be rolled or sprayed on. Hire somebody to do it, this is not a good DIY project. It will be expensive.
If you have the opportunity, have the floor of the concrete tank sloped. Or at a minimum cast in a low spot in the floor. You will want to clean these tanks every year to 2, hire a septic pumping truck to suck the goodies out of the tank. A slope or a low spot makes this a lot easier.
All of this being said, I do have a client who hit solid granite about 2″ under the existing slab. Not wanting to blast a giant hole inside a building, he elected to use a plastic tank for his lift station. He chose a wide flat tank that holds about 600 gallons. Wrapped the tank in tar paper, put it in the hole, then poured reinforced concrete around it.
I’ve mentioned this before in other parts of this website. Above ground tanks are my preferred way of doing things. Your pumps, level detectors, and other equipment don’t have to be immersed in the hot, corrosive environment inside the tank (instead they get the hot, cold, UV, rainy, freezing environment outside tank).
Tank material can be stainless or plastic, I don’t like fiberglass. Maybe you have an old fermenter laying around? An old dairy tank? Perfect for wastewater, assuming it’s big enough. You can also scrounge online for big used tanks. An ugly tank can look pretty once it’s insulated and wrapped.
My favorite material for most wastewater applications is plastic. PVC, ABS, PE, HDPE, XLPE, PVDF, Teflon. I love it. It’s (usually) cheap, lasts forever (if it doesn’t melt), and it’s easy to work with. You can even learn how to weld plastic. Seriously, welded polyethylene (PE) is very versatile. It’s not commonly used in the US, but I’ve seen it widely used in brewery wastewater applications in Europe. Sinks, drains, pipes, manifolds all from welded PE with no fittings- just sheet plastic and pipe.
Maximum temperature ratings for an above ground plastic tank isn’t as much of an issue, still it’s best to verify the tank is rated for at least 160F water before purchasing.
Of course there are a lot of little details here. I can’t give all of my secrets away, so if you need more information, please contact me.[contact-form-7 id=”253″ title=”Contact form 1″]