The petroleum and petrochemical industries are some of the largest users of water, and it’s imperative to find an alternative supply of water such as grey water or wastewater that can provide a cost-effective and ecologically friendly option. Wastewater treatment in petroleum refineries is a complex process because the by-products are so volatile and toxic. Petrochemical wastewater usually needs a combination of treatments whereby oil and other contaminants are removed, as well as VOCs.