In late 2022 we put a reverse-osmosis water recovery system on all three wash lines. The capital investment was $310k. The annual operating-cost reduction is about $98k. The payback is 38 months. Those are the boring numbers. The interesting numbers are about water.
Before
Each wash cycle on a 275-gallon tote consumed approximately 62 gallons of municipal water. Wash, recirculate, hot rinse, RO final rinse, gone to drain. At our annual volume that came out to roughly 11.2 million gallons a year, or about 8 Olympic pools.
After
The RO system runs in a recapture loop. Rinse water drains into a settling tank, gets filtered through a multi-stage prefilter, then through the RO membrane. The permeate (clean water on the other side of the membrane) becomes makeup water for the next wash cycle. The retentate (the dirty side) goes to industrial wastewater handling.
Net new water per tote: about 5 gallons. Recovery rate: about 84%. Annual draw: about 1.8 million gallons.
The membrane question
RO membranes are the expensive part. They are also the part most prone to fouling in a caustic-heavy waste stream. We chose membranes rated for high-pH service and budget a replacement every 14–18 months at $42k per line. That replacement cost is baked into our payback math.
The cleaning-in-place procedure for the membranes is a side science of its own. We do citric-acid cycles weekly and full chemistry cycles monthly. A skipped CIP cycle costs you about three months of membrane life.
Why this matters beyond water savings
The non-obvious benefit of an RO system is what it does for your relationship with the municipal wastewater plant. Industrial wastewater discharge in Green Bay is metered and surcharged based on volume and pollutant load. By recapturing 84% of our process water, we send 84% less load downstream. Our annual discharge surcharge fell by about $61k.
A wastewater plant that does not have to absorb a heavy industrial slug from you every Tuesday is a wastewater plant that is happy to be your neighbor. We have been told this in actual words by actual people there. That counts as a benefit too.