A vegetable cutting plant was having issues on its process line, with its wastewater UF/RO system going down for an average of 3-5 days per month. After some initial troubleshooting discussions with the OEM and end user, a sample of the process wastewater on the day of a failure was provided to 3M for analysis.
3M’s Liqui-Flux ultrafiltration pre-test (UFPT) was utilized in a lab for preliminary tests. This was followed by a pilot ultrafiltration (UF) system to run further tests in a small system. The 3M Liqui-Flux UFPT was utilized in the lab to provide a backwash-ability profile. This six-hour test collected the filtrate volume every five minutes for an hour followed by the backwash process.
After backwashing, the test was started over with a 1 percent crossflow, and it was able to run the full six hours and do a standard backwash every hour, effectively bringing the UFPT back each time. This six-hour test was a success, as it showed there was something in the water that was blinding the separation layer of the existing ultrafiltration system relatively quickly.
The initial test of the sample water quickly showed a degradation of the filtrate flow where a backwash was needed 35 minutes into the first hour of testing. The system was backwashed and run a second time, and degradation also occurred. The first two tests were run in dead-end mode to get an initial baseline.
In the process at the vegetable cutting plant, the ultrafiltration system was getting plugged up and blinding the RO system. Upon testing and analysis with 3M’s Liqui-Flux UFPT, it was determined the issue causing downtime was due to large spikes of oil and grease in the wastewater stream. The original UF system was an outside-in PVDF design, so it could not handle the oil and grease without being pulled offline for a number of days for aggressive cleaning.
E Craig Koch has more than 30 years of experience in water and wastewater treatment, including both chemicals and process equipment solutions. He is currently the Liqui-Flux™ (ultrafiltration) product manager and subject matter expert for 3M’s technical sales efforts in the Americas. Koch has authored and co-authored numerous papers, presentations, and training courses on innovative process applications in the water and wastewater field. He holds a bachelor’s degree from Bloomsburg University.