Rectangular Tanks can be designed using UL-142, Steel Above Ground Tanks for Flammable and Combustible Liquids.
Rectangular tanks are ideal for tight spaces such as an offshore facilities, but they have advantages for mixing and material handling. However, they are typically less cost effective than cylindrical tanks.
In summary, cylindrical tank will be: quicker in delivery, easier to fabricate, less expensive, easier to clean and maintain, more robust, more integrity and stronger, will resist corrosion more because it has no “weak corner welding” and can be drained easier and more positively. It will also resist more positive and negative pressures than its rectangular counterpart.