The present invention provides a physical water treatment (PWT) method and apparatus to treat liquid coolants. Electrodes (22, 24) are provided in a coolant stream (21), and an alternating voltage is applied across the electrodes (22, 24) to produce an electric field through the coolant. The alternating voltage creates an oscillating electric field in the coolant that promotes the collision of dissolved mineral ions. The ions collide to form seed particles that precipitate out of solution. Bulk precipitation of seed particles decreases the availability of ions in solution which can crystallize on heat transfer surfaces. The seed particles adhere to additional ions that separate out of solution and form larger particles that may be removed from the coolant stream (21) using a variety of treatment measures. In addition to precipitating mineral ions, the electric field may be applied to destroy bacteria, algae and microorganisms that accumulate in the coolant stream (21).