Avista Impact Study

We will explore an impact study that demonstrates how Avista Membrane Treatment Solutions helped a Beverage plant uncover and solve the drivers for high operational costs and high membrane replacement rate.

Over the span of ten years, this beverage plant experienced a significant operational cost increase for their RO system due to a lack of maintenance, operator training and changing water quality.

A detailed Avista audit of the original system design including pretreatment, water quality, particle count, turbidity testing as well as the results of a membrane autopsy results helped to identify the source of membrane fouling.  Cost comparison between the current operation and the past 10 years will be shown in the Impact conclusions. This tactical planning approach can be applied to help other food and beverage reverse osmosis treatment plants reduce their operational costs while also increasing membrane life.

We will study cost increase causes, including:

• Energy cost increasing with the increase of feed pressure
• Weekly RO CIPs
• Daily cartridge filter replacement
• Annual RO membrane replacement

Understanding the system design

First step in the process is to evaluate the current system design. Follow the diagram to see what we learned.

The data agreed with the plant suspicions

Based on their own evaluation, the Beverage plant’s management team had a suspicion of what what the problem was – insufficient removal of metals by the green sand filters. The normalized permeate flow data was the overall flow rate of the 1st Pass RO. The disadvantage of only looking at the total permeate flow is that it was not possible to tell whether Stage 2 performance had been compromised.

The CIP efforts did not appear to help with restoring the permeate flow rate or the DP back to baseline and also did not provide sustainable performance over time.

Avista cartridge filter autopsy result

A walkthrough of the plant revealed black cartridge filters, which had just been replaced after being online for only three days.

After confirming the material as primarily manganese, the next step was to determine how it was bypassing the GS filters and fouling the membranes.

Easy but effective troubleshooting

Additionally, a profile of iron, manganese, particle count and turbidity removal throughout the system was performed to determine the source of the manganese bypass. The site was surprised to see that the GS filters were achieving efficient removal of iron, manganese and particulates. However, manganese levels increased above the raw well values before the cartridge filter. The primary explanations for this result include slugs of manganese coming into the system that were not observed at the time of sampling or issues within the holding tank.

This finding prompted the operators to inspect the holding tank.

Was the holding tank to blame?

The beverage plant believed that the manganese in the tank was likely a result of small bypasses throughout the years accumulating, which then sloughed off the tank periodically, fouling the cartridge filters and RO. After the tank was cleaned, it was believed that the cause of the system fouling was resolved.

The RO system was cleaned with a specialty cleaner targeting metals. The water production and DP were restored but the permeate conductivity was too high.

Taking extra steps is key in troubleshooting

The decision was made to replace the membranes in the first pass because they did not provide the needed quality. Loss in membrane integrity historically influenced the replacement of the first pass membranes; however, the site did not know the cause for the decrease in permeate quality.

A lead and tail membrane were chosen for dissection and an Avista Membrane Autopsy to troubleshoot the loss in element rejection.

Stage 1, lead position

Dye Test showing membrane oxidation damage:

Stage 2, tail position

Dye Test showing membrane oxidation damage:

Saturation indices at 75% recovery