Eliminating Microbiological Contamination in Ozone Fruit Wash Water
Location:
South Africa
Date:
May 2025
Background
At a leading fruit processing facility, Arc Aqua ozone washers were deployed to sanitize fruit surfaces before entry into high-care zones. Initial expectations were that combining ozone with standard filtration would meet hygiene standards. However, the facility faced ongoing challenges:
Persistent microbial contamination (E. coli, coliforms, and total bacteria)
Organic residue accumulation
Biofilm formation in wash systems
Unsustainable water losses in early-stage solutions
Filtration System Overview
To remove physical contaminants, a multi-stage filtration system was implemented:
Settler: Removed sand, soil, and large debris
Carbon Filter: Adsorbed organic compounds
Sand Filter: Removed suspended solids
Bag Filters (25μm): Captured fine particles
Treatment Tank: Enabled water recirculation
UV Lamps: Provided baseline disinfection
Waboost Ozone Ultrafine Bubble Generator: Trial focus
Ultrafiltration: Reserved for future integration
Filtration Performance Metrics:
ParameterRemoval EfficiencySuspended Solids98%Organic Matter76%Chemical Oxygen Demand57%Microbial Contamination0% (no removal)
Despite strong physical performance, filtration alone could not resolve microbial contamination, requiring advanced disinfection.
Disinfection Trials Overview
Objectives:
Eliminate microbial contaminants
Enable water reuse in a closed-loop system
Avoid harmful residues and surface effects on produce
Suppress biofilm formation and regrowth
Treatment Methods Trialed:
Total Loss System – Effective but unsustainable (6,000 L/hr water loss)
Sodium Hypochlorite – Reduced bacteria but introduced chemical residues
Hydrogen Peroxide – Effective but costly
Peracetic Acid – Strong disinfectant, but caused odor and residue issues
Chlorine Dioxide – High efficacy but corrosive to infrastructure
Ozone Injection via Ultrafine Bubbles – ✅ Highly effective, chemical-free, sustainable
Reverse Osmosis (RO) – Excellent microbial removal, but overengineered and expensive
Long Water Loop Simulation – Promising closed-loop model incorporating ozone + filtration
Why Ozone via Nanobubbles Was the Optimal Solution
Among all methods tested, ozone injection using ultrafine bubbles provided the best balance of efficacy, sustainability, and cost:
✅ Complete microbial and biofilm control
✅ No chemical residues or impact on fruit quality
✅ Compatible with closed-loop systems
✅ Minimal infrastructure upgrades required
✅ Lowest cost per liter of treated water
✅ Breaks down naturally into oxygen—no toxicity
Scientific Advantages of Ozone:
50% stronger oxidizer than chlorine
Broad-spectrum action against bacteria, viruses, and spores
Penetrates biofilms that resist conventional agents
Recommended Future Strategy: Long Water Loop Model
To achieve best-in-class sanitation and sustainability, the facility should adopt a Long Water Loop model by recirculating wash water through a centralized treatment plant featuring:
Multi-stage filtration (sand, carbon, bag, cartridge, glass media)
UV disinfection
Centralized ozonation (primary method)
Optional chlorine dioxide dosing for periodic sanitation
Expected Benefits:
Regulatory compliance through full microbial control
Reduced chemical procurement, handling, and storage
Improved water sustainability metrics
Prolonged equipment lifespan due to chemical-free treatment
Conclusion
The use of ozone ultrafine bubble technology emerged as the only method that effectively unified food safety, sustainability, and economic efficiency. In the context of increasing regulatory and environmental pressures, ozonation offers a future-proof standard for produce sanitation—delivering complete microbial control without chemical compromise.