Access to clean and safe drinking water is a global necessity, and advanced water treatment technologies play a pivotal role in achieving this. Among the highly effective materials employed in water purification, activated alumina has emerged as a leading adsorbent, particularly for the removal of fluoride and other detrimental contaminants. Its unique physical and chemical properties enable it to efficiently purify water, making it a critical component in municipal and household water treatment systems.

Activated alumina, a form of aluminum oxide (Al2O3) processed to create a highly porous structure with an extensive surface area, functions through the principle of adsorption. This means that contaminant molecules in the water physically adhere to the surface of the activated alumina particles. The material's high surface-area-to-volume ratio provides an abundance of binding sites, allowing it to capture target contaminants with remarkable efficiency.

One of the most significant applications of activated alumina in water treatment is fluoride removal. In many regions, naturally occurring fluoride levels in groundwater can exceed recommended limits, posing health risks such as dental and skeletal fluorosis. Activated alumina effectively adsorbs fluoride ions from water, significantly reducing their concentration to safe levels. The adsorption process is influenced by factors such as pH, contact time, and the alumina's specific properties, but generally, activated alumina can achieve substantial fluoride reduction, often lowering levels from several parts per million (ppm) to below 1 ppm.

Beyond fluoride, activated alumina also demonstrates efficacy in removing other harmful substances from water. It is known to adsorb arsenic and selenium, both toxic heavy metals that can contaminate drinking water sources. The selective adsorption of these contaminants by activated alumina helps to ensure that water is not only free from excessive fluoride but also from other dangerous impurities. This broad-spectrum adsorption capability makes activated alumina a versatile solution for comprehensive water purification.

The performance of activated alumina in water treatment is enhanced by its physical robustness. It maintains its structural integrity even when continuously exposed to water, resisting breakdown and minimizing the release of fines into the treated water. While regeneration of activated alumina for water treatment is possible through chemical washing (e.g., with lye or acid), it is often replaced once its adsorption capacity is exhausted, especially in continuous water treatment systems, to ensure consistent purity levels. For many water treatment applications, the focus is on the effective removal of contaminants to meet stringent drinking water standards.

In conclusion, activated alumina is a highly valuable adsorbent in water treatment, primarily recognized for its exceptional ability to remove fluoride and other harmful contaminants like arsenic and selenium. Its physical strength, large surface area, and efficient adsorption mechanism make it a reliable and effective medium for ensuring the safety and potability of drinking water, contributing significantly to public health.