What is the minimum capacity of the first tank in a three-tank system?

The correct answer outlines that the minimum capacity of the first tank in a three-tank system must be at least one-third of the total system size, with a minimum threshold of 500 gallons. This requirement ensures that the initial tank has sufficient volume to accommodate incoming wastewater, allowing for proper settling of solids and effective treatment of the effluent.

This portion of the tank capacity is critical in preventing overloading of the system, allowing time for solids to separate from the liquids, which is essential for maintaining the efficiency and longevity of the entire sewage treatment process. Insufficient capacity in the first tank could lead to issues such as backups, increased maintenance needs, and overall system failure, compromising the effectiveness of the entire installation.

In contrast, the other options suggest different minimum capacities or proportions that do not align with established guidelines for optimal tank functioning. For example, proposing a minimum of one-quarter size or varying gallon amounts would not ensure experienced operators have adequate space for proper wastewater management and treatment protocols.