Case Study: Impact of Non-Food Grade Sealant on Final Water Quality.

Background

A new water bottling plant was set up with a reverse osmosis (RO) filtration system to purify water before bottling. The final purification step included ozonation to eliminate any remaining contaminants, ensuring the safety and taste quality of the water. During the RO system installation, a non-food grade sealant based on alkyd-modified resins (especially fumarated resins) was mistakenly used to seal the RO vessel ends. This error led to significant product quality issues, notably a butter-like off-taste and rancid odor in the bottled water.

Problem Identification

After the initial production run, the quality assurance team noticed a distinct off-taste described as "buttery" in the bottled water, leading to a comprehensive investigation. The team employed a 5 Why Analysis to systematically trace the root cause of this sensory defect.

Investigation Process

1. Step 1: Analyzing the Off-Taste

The team first verified the nature of the off-taste, identifying it as a "buttery" flavor. This sensory characteristic raised concerns about potential ozonation by product contamination (aldehydes or ketones), as such compounds can produce distinctive tastes and odors when present in water.

2. Step 2: Ozonation Testing

Water samples were tested both with and without ozonation. The analysis revealed that all non-ozonated samples were free from off-tastes and VOCs. However, after ozonation, a strong butter-like flavor were detected, suggesting that the reaction between ozone and certain materials in the system was responsible for the contamination.

3. Step 3: Isolating the RO System

Sequential sampling led the team to a specific RO unit that consistently produced water with the same off-taste profile as the final bottled product. The focus then shifted to materials within this unit that could potentially react with ozone.

4. Step 4: Identifying the Sealant as the Root Cause

The investigation revealed that a non-food grade, alkyd-modified resin-based sealant was applied to seal the RO vessel ends. Alkyd resins especially fumarate resins which is actually existing as 50 % of the compositionof this non food grade sealant are known to degrade under oxidative stress, such as ozone exposure, releasing aldehydes like butyraldehyde (butanal )—a compound known for its buttery aroma. This discovery linked the use of this sealant to the off-taste issue.

Scientific Analysis of the Issue

Alkyd-modified fumarated resins in the sealant are susceptible to oxidative degradation when exposed to strong oxidizers like ozone. This degradation releases butyraldehyde, and other small organic molecules, which impart a distinct buttery taste and odor. The presence of ozone accelerates this breakdown, resulting in higher threshold in the water.

The non-food grade sealant, not designed for potable water applications, lacked resistance to ozonation, making it unsuitable for use in a system involving ozonated water. This case highlights the critical role of selecting materials compatible with all aspects of the purification process, particularly oxidative steps like ozonation.

Resolution and Corrective Actions

Upon identifying the root cause, the following corrective measures were implemented:

1. Sealant Removal: A thorough cleaning procedure was undertaken to remove the non-food grade sealant and any residual traces from the RO vessel.

2. Replacement with Food-Grade Sealant: A food-grade, ozone-resistant sealant certified for potable water use was applied to ensure no further contamination.

3. Post-Cleaning Testing: Extensive water testing post-cleaning showed a complete elimination of the off-taste, confirming the effectiveness of the corrective actions.

4. Enhanced Quality Control Protocols: A protocol was instituted to verify that only certified food-grade materials are used in water-contacting components of the purification system, particularly for systems incorporating ozonation.

Outcomes

Following these corrective actions, the water quality returned to acceptable sensory standards, with no detectable off-tastes. This case underscores the importance of:

Material Compatibility: Ensuring that all components in water treatment systems are compatible with oxidative processes, such as ozonation, to prevent chemical degradation and contamination.

Food-Grade Certification: Utilizing only food-grade, potable water-certified materials in any component that comes in contact with water to prevent health risks and product quality issues.

Conclusion

This case demonstrates the critical interplay between material science and process engineering in the water treatment industry. Selecting appropriate, certified materials for each stage of water purification, especially ozonation, is essential for ensuring high-quality and safe bottled water production. Properly addressing these material compatibility issues can prevent similar occurrences in future installations, protecting both product integrity and consumer health.

Ibrahim Hashim