| Water Sources from different places have a variety of impurities in different concentrations. The impurities are a combination of various cations and anions – which are inorganic in nature and contribute to the “total dissolved solids” in water. Machine coolants are a blend of 4-5% mineral oil in
| On continuous recycling of the coolant, these salts get concentrated due to evaporation of
water alone, when the cutting fluid comes in contact with the hot machining surface. Such build up of dissolved solid will have two problems,
| 1. Higher salt concentrations have been noticed to increase Pseudomonas growth.
| 2. Large concentrations of hardness cations and other dissolved solids can lead to instability of the
| emulsion and precipitation of insoluble material on the machining surface.
| An important aspect of coolant
recovery is the removal of salts from water in the emulsion. This can be achieved by membrane separation after suitable pre-treatment by photochemical oxidation to ensure bacteria free coolant emulsion as feed to the membrane process.