Stožice Stadium, a modern football arena in Ljubljana with a capacity for more than 15,000 spectators, faced significant challenges with its rainwater-based irrigation system. The stormwater used for turf irrigation contained high levels of pathogenic microorganisms and exhibited low dissolved oxygen values—conditions that threatened the health of the playing surface and the well-being of stadium users. In March 2022, an innovative disinfection and oxygenation upgrade using ozone and oxygen nanobubble technology was implemented, yielding dramatic improvements in water quality and turf resilience.

Introduction

Football stadiums are not only venues for sport but also public spaces where water quality is paramount for both safety and turf management. Stožice Stadium’s irrigation system historically relied on rainwater, which, despite its eco-friendly nature, often carried harmful pathogens. Coupled with low oxygen content, the raw water posed multiple challenges, particularly under extreme weather conditions.

In March 2022, the stadium initiated a nanobubble-based solution to tackle these issues. The system was designed to disinfect the irrigation water and enrich it with dissolved oxygen, creating an environment conducive to robust turf growth and resilience. This upgrade delivered direct financial benefits by ensuring the playing surface remained in optimal condition while also protecting public health.

Nanobubble Technology Overview

Nanobubble technology harnesses the power of extremely small gas bubbles—typically less than 200 nanometers in diameter—to treat water. The process includes two key components:

• Ozone Nanobubble Disinfection:
  Ozone, encapsulated in nanobubbles, delivers a potent oxidative effect that almost completely eliminates pathogenic microorganisms from the water. This step is crucial in safeguarding the health of stadium users and ensuring the water does not contribute to disease risks.

• Oxygen Nanobubble Oxygenation:
  After disinfection, oxygen nanobubbles are infused into the water, drastically increasing its dissolved oxygen concentration to levels greater than 15 mg/l. This enriched oxygen content supports enhanced nutrient uptake and robust turf growth, directly counteracting the stress caused by high temperatures.

The integration of these processes in the stadium's irrigation water tank has turned previously suboptimal water into a high-quality resource that actively promotes turf vitality and longevity.

Implementation at Stožice Stadium

Timeline & Context:

• Implementation Start: March 2022

• Installation Type: Irrigation water tank system

• Starting Parameters:

  • Dissolved Oxygen Levels: Low

  • Pathogenic Microorganisms: High

• Post-installation Parameters:

  • Water Quality: Disinfected with dramatically reduced pathogen levels

  • Dissolved Oxygen: Exceeding 15 mg/l

Process Overview:

1. Initial Disinfection with Ozone Nanobubbles:
   The system began by treating incoming rainwater with ozone nanobubbles, achieving an almost complete reduction of harmful pathogens. This step was critical to eliminate waterborne disease risks, thereby ensuring a safer environment for both athletes and spectators.

2. Oxygen Nanobubble Injection:
   Following disinfection, oxygen nanobubbles were introduced into the water. Within 14 days, significant improvements were observed in the condition of the turf’s root system—a marker of the water’s enriched oxygen content and overall quality.

3. Integration into Existing Infrastructure:
   The nanobubble system was seamlessly incorporated into the existing irrigation water tank. This ensured that every watering cycle delivered high-quality, disinfected, and oxygen-rich water to the football turf.

Key Outcomes and Benefits

Direct/Indirect Financial Benefits

• Pathogen Elimination:
  The advanced ozone nanobubble treatment achieved an almost complete reduction of pathogenic microorganisms in the irrigation water. This enhanced water safety directly contributes to reducing health risks for stadium users and minimizes liability and related costs.

• Enhanced Turf Resilience:
  The oxygen nanobubble injection boosted dissolved oxygen levels to over 15 mg/l. As a result, within 14 days, noticeable improvements in turf root development were observed. Healthier root systems lead to stronger, more resilient turf, which reduces the need for expensive, frequent repairs.

Additional Operational Benefits

• Mitigation of Heat Stress:
  In July 2022, Ljubljana experienced its hottest month in 50 years, with average daily temperatures exceeding previous averages by more than 3°C. Under such extreme conditions, the turf faced the risk of heat shock. However, the oxygen-enriched irrigation water significantly reduced the severity of this shock, effectively preventing turf death and saving the playing season.

• Public Safety and Maintenance Savings:
  The transformation of the irrigation water quality not only safeguards the health of visitors by eliminating pathogens but also reduces long-term maintenance costs. A robust and resilient playing surface requires fewer interventions, thereby ensuring uninterrupted use during critical sporting events.

Discussion

Agronomic Impact

The transition to a nanobubble-enhanced irrigation system has revolutionized turf management at Stožice Stadium. By disinfecting water and elevating dissolved oxygen levels, the technology addresses both microbiological safety and plant physiological needs. The prompt recovery and reinforcement of the turf’s root system translate into a stronger, more resilient playing field capable of withstanding environmental stresses.

Economic and Operational Advantages

• Cost Savings:
  With reduced risk of pathogen-related issues and enhanced turf performance, the stadium benefits from lower maintenance and operational costs. The quality of the turf is maintained even during extreme weather, thereby safeguarding revenue from matchday operations and ensuring fan safety.

• Enhanced Public Image and Safety:
  Upgrading to a state-of-the-art water treatment system reinforces Stožice Stadium's commitment to public safety and high-quality facilities, which can improve stakeholder confidence and community support.

Conclusion

The implementation of ozone and oxygen nanobubble technology at Stožice Stadium in Ljubljana represents a landmark advancement in irrigation water management for football turf. The system has:

• Achieved an almost complete reduction of pathogenic microorganisms in irrigation water.

• Increased dissolved oxygen levels to above 15 mg/l, significantly improving turf root development.

• Protected the turf against heat shock during record-breaking temperatures in July 2022, effectively saving the playing season.

This case study demonstrates that integrating nanobubble technology into existing water treatment infrastructures not only enhances the safety and quality of irrigation water but also yields measurable financial and operational benefits. Stožice Stadium's success story offers a replicable model for other sporting venues looking to modernize their turf management practices while ensuring public safety and operational efficiency.