What substance does mechanical treatment of boiler water primarily reduce?

The mechanical treatment of boiler water primarily targets the reduction of oxygen. Oxygen is a significant factor contributing to corrosion within boiler systems. When dissolved in water, oxygen can react with metal surfaces, leading to rust and other forms of deterioration that compromise the integrity and efficiency of the boiler.

Mechanical treatment methods, such as deaeration, are specifically designed to physically remove dissolved gases, including oxygen, from the water before it enters the boiler. This process involves heating the water and reducing the pressure to encourage the release of gases, thereby minimizing oxygen levels. Maintaining low oxygen levels is crucial for the longevity of the boiler and helps in minimizing maintenance costs and downtime.

The other substances listed in the options—nitrogen, acidity, and steam loss—are addressed through different treatment methods or processes. Nitrogen, while present in the air, is generally inert and does not pose a significant risk compared to oxygen. Acidity is managed through chemical treatment rather than mechanical methods, and steam loss pertains to operational efficiency rather than the treatment of water. Therefore, the focus of mechanical treatment directly aligns with the elimination of oxygen from the boiler water, making it the correct answer.