What factor should be evaluated in the bed surface of a water treatment system?

Evaluating the efficiency of the treatment is crucial when assessing the bed surface of a water treatment system. The bed surface impacts the overall performance of the treatment process by influencing the contact time between the water and the treatment media, as well as the flow dynamics through the system. An effective bed surface will ensure optimal conditions for processes like filtration, adsorption, and biological treatment, which are essential for removing contaminants and achieving regulatory compliance for safe drinking water.

While other factors like cost, appearance, and age may have relevance to operational considerations or maintenance scheduling, they do not directly pertain to how effectively the water treatment system performs its primary function of purifying water. Efficiency is the central measure of how well the system accomplishes its goals, hence making it the key factor to evaluate in this context.