Greases and oil can be removed from a wastewater stream by:

Greases and oils can be effectively removed from a wastewater stream through skimming. This process involves the physical separation of floating materials, such as oils and greases, from the water surface. Since these substances are less dense than water, they tend to rise to the top, where they can be collected and removed.

Skimming is particularly advantageous because it does not require complex chemical reactions or processes; it simply takes advantage of the physical properties of the grease and oil. This method can be employed in various settings, such as in treatment plants, where a specifically designed skimming device is often utilized to maintain water quality.

Other methods like settling tanks, chlorination, and hydroxide precipitation address different types of contaminants or processes. Settling tanks can separate solids from liquids based on density, mainly targeting particulate matter instead of surface substances. Chlorination is primarily used for disinfection and does not effectively remove oils and greases. Hydroxide precipitation involves forming insoluble compounds through chemical reactions, which again may not target oily substances specifically. Thus, skimming stands out as the most direct and efficient method for removing greases and oils from a wastewater stream.