Which company has a platoon that can purify 140k liters of water per day from a freshwater source?

The Water Support Company is specifically designed to handle operations related to water purification and supply. This unit is equipped with specialized equipment and trained personnel to effectively purify large quantities of water, making it vital in combat and humanitarian scenarios where access to clean water is often limited. The capacity to purify up to 140,000 liters of water per day from a freshwater source highlights the company's essential role in sustaining troops and supporting operations in the field.

Other companies mentioned have distinct functions that do not focus on water purification. For example, the Forward Support Company provides logistical support, the Field Feeding Company is concerned with food service and meal preparation, and the Combat Service Support Company offers various logistical services but does not specialize in water purification. This specialization of the Water Support Company makes it the correct choice for the question regarding daily water purification capability.