Views: 0 Author: Wordfik Vacuum Publish Time: 2026-01-13 Origin: Wordfik Vacuum
Most water treatment plants face recurring issues: accelerated pipe corrosion, frequent RO membrane cavitation, unstable flocculation results, and even secondary microbial growth. These problems often trace back to one overlooked factor: dissolved gases in raw water. While conventional aeration or thermal degassing can partially address this, vacuum degassing has emerged as the most efficient, cost-effective solution for both municipal and industrial water systems.
Dissolved oxygen (DO), carbon dioxide, nitrogen and trace volatile gases naturally exist in source water, and their impact goes far beyond water taste. For treatment systems, they create tangible operational and maintenance costs:
Pipeline and equipment corrosion: Dissolved oxygen is the primary cause of pitting corrosion in carbon steel pipes and boiler tubes. When DO levels exceed 2mg/L, the annual corrosion rate of carbon steel can reach 0.2mm — 4 to 5 times higher than in properly degassed water.
Membrane system damage: Gas bubbles form and collapse on RO/UF membrane surfaces, causing cavitation erosion that reduces membrane flux by 15-20% and shortens service life by nearly 30%.
Unstable treatment efficiency: Dissolved CO₂ lowers water pH, interferes with coagulant dosing, and leads to fluctuating effluent turbidity in sedimentation processes.
Secondary microbial risk: Dissolved oxygen supports aerobic bacteria growth in distribution networks, increasing disinfection byproduct formation and pipeline biofouling.
Vacuum degassing operates on Henry’s Law: the solubility of a gas in liquid decreases as the partial pressure of that gas above the liquid drops.
In a typical system, water is sprayed from the top of a degassing tower, while a vacuum pump maintains a stable negative pressure (usually -0.08 to -0.095 MPa) inside the tower. As water falls through the packed bed, dissolved gases are rapidly released from the water phase into the gas phase, then extracted and discharged by the vacuum pump.
Unlike simple spray aeration, which only achieves 30-40% removal efficiency for dissolved oxygen, a properly sized vacuum degassing system can reduce DO to below 0.1mg/L and remove over 90% of dissolved carbon dioxide. It also avoids the high energy consumption of thermal deaerators, making it suitable for both new installations and retrofits.
Vacuum degassing is not a one-size-fits-all process. Its value varies by water source and treatment goal, with the most common use cases including:
For low and medium-pressure industrial boilers, vacuum degassing is the standard alternative to thermal deaerators. It prevents oxygen pitting in boiler tubes and steam lines, reduces blowdown frequency, and cuts energy costs by 40-60% compared to steam-heated deaeration. It is especially cost-effective for waste heat boilers and small-to-medium boiler rooms.
Industrial wastewater often contains dissolved corrosive gases and volatile organic compounds. Vacuum degassing removes these contaminants before biological treatment, reducing load on aeration tanks, preventing odor emissions, and protecting downstream pumps and instruments from corrosion.
In municipal supply systems, dissolved nitrogen and CO₂ cause flat taste and accelerate distribution pipe corrosion. Vacuum degassing improves organoleptic quality, stabilizes pH, and extends the service life of pipe networks without adding chemicals.
Installed before membrane systems, vacuum degassing eliminates gas bubble formation inside membrane elements, preventing cavitation damage and water hammer. It also improves permeate flux consistency and reduces membrane cleaning frequency.
For pharmaceutical grade water and electronic ultrapure water, dissolved gas levels must meet ppb-level standards. Vacuum degassing, when paired with polishing processes, reliably achieves ultra-low DO levels to meet pharmacopoeia and semiconductor manufacturing specifications.
Compared to widely used aeration, thermal deaeration and chemical degassing, vacuum technology offers clear operational and economic benefits:
Higher removal efficiency: 95%+ DO removal, far exceeding the 30-50% of conventional aeration.
Lower operating cost: No steam heating required; energy consumption is only 30-50% of thermal deaerators.
Compact footprint: Modular design with smaller tower volume, easy to integrate into existing treatment lines.
No secondary contamination: Oil-free vacuum systems introduce no additional chemicals or oil mist into the water.
Wide adaptability: Works for flow rates from 1 m³/h small systems to 100+ m³/h large municipal plants.
To maintain long-term efficiency and reduce downtime, follow these field-proven operational practices:
Maintain inlet water temperature above 15°C — higher water temperature improves degassing efficiency under the same vacuum level.
Install a vacuum surge tank to stabilize negative pressure in the tower and avoid efficiency drops from pressure fluctuations.
Drain the water-gas separator regularly to prevent liquid carryover into the pump chamber.
Control spray density between 10-20 m³/(m²·h) in the degassing tower; too high or too low reduces gas-liquid contact efficiency.
Install an online DO monitor at the outlet to adjust pump speed and vacuum level based on real-time water quality.
Q: What is the lowest dissolved oxygen level vacuum degassing can achieve?
A: A standard industrial vacuum degassing system typically reduces DO to 0.1 mg/L or lower. For ultrapure water applications, when combined with downstream membrane degassing polishing, levels can reach single-digit ppb ranges.
Q: Can vacuum degassing remove all dissolved gases from water?
A: It is highly effective for oxygen, carbon dioxide, nitrogen and most non-condensable gases. Removal rates vary by gas solubility, with CO₂ and O₂ removal usually exceeding 90%.
Q: Is vacuum degassing feasible for small-scale water treatment?
A: Yes. Modular compact units are available for flow rates starting at 1 m³/h, making them suitable for small industrial facilities, laboratories and residential water systems.
