Home · Resources · Field Notes · Wash bay water recycling the dirty math and the clean economics
Field notes

Wash bay water recycling — the dirty math and the clean economics

February 8, 2024·11 min read·By Devon Marks
sustainabilityoperationswash

When we installed the second wash bay in 2022, our water bill jumped from a comfortable line item to the third-largest operating expense. Fresh potable water at municipal rates for an industrial wash operation adds up fast, especially when the regulatory side requires that rinse water meet potable standards before it touches a Grade A bottle. We needed a recycling setup. Here’s what we built and what it cost.

The starting state

Pre-recycling, our wash bay used roughly 110–140 gallons of potable water per tote (cold flood, caustic stage, two hot rinses, final test). At 200–240 totes per week, that’s 25,000–33,000 gallons of water per week, all entering our wash effluent stream and going out to municipal sewer with a BOD-and-pH-loaded discharge.

The first cut: catch the rinse

Most of the water we use is for the final two rinses, where the water comes off clean. Catching the final rinse for use as the next tote’s first flood was the obvious first move. We installed a 1,500-gallon polypropylene catch tank with an inline pH meter and a turbidity probe. Final rinse water that hits pH 7.0–7.5 and turbidity below 5 NTU diverts to the catch tank; out-of-spec water continues to drain.

Results: 35% reduction in fresh water use, no quality degradation in inbound totes. Capex was $9,200 (tank, plumbing, pumps, controls). Payback at our rates was 11 months.

The second cut: filter and reuse the wash water

The caustic wash water carries most of the bottle residue. Filtering and reusing it (rather than fresh caustic per cycle) reduces fresh water use further and reduces caustic consumption. We added a bag-filter housing (50 micron primary, 10 micron secondary) and a small heater to maintain temperature between cycles. Caustic concentration is replenished with a small additive pump triggered by a pH meter.

Results: an additional 25% reduction in fresh water, plus a 40% reduction in caustic chemical purchase. Capex was $12,800. Payback was 17 months on the second cut, blended into the system.

The constraint: bottle-by-bottle quality

Recycled wash water is fine for industrial-grade totes (Grade B and Grade C) but we use fresh-only protocol for Grade A food units. The blended system runs Grade A on one bay (fresh only) and Grades B/C on the other bay (recycled). This complicates scheduling but maintains the food-grade guarantees we need.

Effluent side

The recycling system reduced our discharge volume by 60% and the BOD load by closer to 70% (because the recycled stream is reused rather than discharged). Our municipal pretreatment surcharge dropped substantially — we’re now below the threshold for industrial pretreatment review, which removed an annual compliance fee.

What didn’t work the first time

Original plan included reverse osmosis polishing of recycled water, with the idea that polished recycled could feed Grade A. The membrane fouling rate at our throughput was too high — we were replacing membranes every 5–6 weeks at $1,200 per cartridge, which destroyed the economics. We dropped the RO step and accepted the constraint that Grade A washes use fresh.

What we’d do differently

Larger catch tank upstream. We sized 1,500 gallons assuming a 6-hour residence time; we ended up needing 9 hours of residence to let suspended solids settle properly. A 2,500-gallon tank would have eliminated the second-stage filtration entirely for Grade C work.

Questions on this one? Email info@ibctankscleveland.com. We answer everything inside one business day — usually inside four hours.

← Older
Insulated heating blankets — when they’re worth it and how to spec
Newer →
Measuring tote fill level without a sight glass
Topic requests

Want us to write about something specific?

Fill in a few details — quantity, product type, the work you need done. We respond by email within one business day.

Format: name@example.com
Format: (555) 555-1234 or 555-555-1234 — US or Canada only
Format: 12345 / 12345-6789 (US) or A1A 1A1 (Canada)

More from Field Notes