Please see my additions below...........
Originally Posted by Dancing Camel".............I've managed to convince them that spent grains/trub/yeast are going to the cows so it's really just the cleaning side they're concerned with.
Be careful with the grains and yeast with regards to cattle. The farmers need to use the byproducts as suppliments to a grass/hay diet or the cattle will bloat and die a somewhat horrible passing due to a ruptured stomach (from gases produced). You can do a search on Probrewer for prior discussions.
Some of the details they've been asking about:
1. How often are tanks cleaned
After every use. On the day of transfer of the product from them. This is scrubbing out or caustic washing any yeast deposits that are on the surfaces.
2. How often are the tanks sanitized
Prior to every use. The tanks MUST be clean prior to sanitation. We use Iodifor, but Per-Acetic acid or similar is fine.
3. How much water is used in cleaning/sanitizing process
Cleaning: Around 20 gallons if using caustic and recirculating.
Sanitizing: Around 8 - 10 gallons.
4. What chemicals are used in cleaning/sanitizing and in what dilutions
Cleaning: Caustic soda heated to around 130 - 140F. The mix will be very basic (hi pH)
Sanitizing: Iodifor, Per-Acetic acid. Use cold. Both break down into some pretty tame solutions.
Follow the package instructions.
5. What will be the PH of the caustic & acid solutions when sewered. I've told them I'll be reservoiring & recycling the solutions so the real question is until what PH is the caustic and the acid effective?
I don't have a ready answer for the pH, but you can't re-use your sanitizers. They'll go to drain. You can use your caustic as long as the pH is high enough, but you'll eventually need to change it out. You can cut it with yeast or beer to neutralize its pH (both are acidic), but your sewer district might not like you dumping yeast down the drain a whole lot.
6. What special equipment do I need to recycle caustic & acid solutions & is it worth it?
Basically, to re-use the caustic you need a small stainless tank somewhere in your Brewery. I don't know if you made it down to our place when you were in Everett, but we have an old yogurt flavor mix tank that looks like a mini conical fermenter without a lid. We store caustic in there. You can use all your existing process equipment (pumps, hoses). Rinse them with hot water.
Don't forget to backfush your heat exchanger with hot caustic regularly. That system you have has the heat exchanger below the decking and it's a real pain to tear it down and clean the leaves.
Anything else you can think of that would be of interest to a sewage plant would be extremely helpful.