Water Operator Class 3 Practice Test 2025 - Free Water Operator Exam Questions and Study Guide

Calcium carbonate is used in water treatment primarily for corrosion control, especially in the context of adjusting pH levels to reduce the corrosiveness of water. When applied just after filtration, it effectively increases the alkalinity and pH of the treated water to more stable levels, reducing the potential for leaching of metals from pipes and fixtures.

Applying calcium carbonate after the filtration process allows it to dissolve into the water column, ensuring that it thoroughly interacts with the treated water. This is crucial because if it were applied just before or during filtration, the filter medium might trap or absorb the calcium carbonate particles, which would prevent it from achieving the desired pH adjustment effectively. Additionally, if applied after the treatment plant, it would still serve its purpose, but the timing immediately after filtration allows for optimal interaction before water enters the distribution system.

Thus, placing the calcium carbonate just after the filter is the most strategic choice for achieving effective corrosion control in the water supply system.