**6. Active pharmaceutical ingredient (API)**

Active pharmaceutical ingredient (API) is one of the most widely used and oldest systems for removing fat and oil from water, wastewater, and wastewater. These systems tend to remove free oil down to less than 15 mg L−1 [7]. The construction of water and oil separators by API method is similar to a rectangular clearinghouse, although they have different sizes and design details.

These grease traps are used to remove free oil as well as solid particles from wastewaters of refineries, petrochemicals and chemical plants and other industries. These grease traps are designed according to the standards published by the American Petroleum Institute. The basis of this type of separator is the difference in specific gravity. Less specifically-weighted liquid (usual oil) is collected from the surface, while the fluid with more specific gravity remains in the lower part. Wastewater may contain insoluble oil, sludge, and some soluble components. In common API degreasers, wastewater is initially collected in a pretreatment section for sludge collection. Baffles allow the sewage flow to move slowly towards the outlet, and the oil is separated from the water and effluent.

Usually, in the process of API grease traps, the oil layer, which may contain amounts of water and suspended solids, must be continuously emptied. This layer of isolated oil may be reprocessed or destroyed to recover valuable products. The sedimentary layer containing solid particles formed at the bottom of the degreaser is removed by a remover (or similar device) and a sludge pump.

In the design of API grease traps and other similar gravity tanks, if the input current meets the following conditions, the performance of the grease traps will be difficult:


## **7. Corrugated plate interceptor (CPI)**

In addition to the grit classifier at this stage, different types of grease traps can also be used. For example, CPI degreaser is one of the most applicable equipment in this field. It is a kind of gravity separator and causes colloidal particles suspended in wastewater with a size of at least 50 microns to be separated from wastewater. This type of degreaser, sometimes called Tilted Plate Interceptor, has widely replaced API separators and primary settling tanks [8].

In CPI fat, the inlet wastewater is transferred to the machine to diagonal plates at an angle of 45 to 60 degrees. These plates have resin-reinforced layers, eventually causing the fat particles to settle above the surface of the sewage and the rest that weighs heavier. The simple structure of this method reduces the cost of construction and maintenance of facilities. One of the most important uses of CPI separators is oil and gas refineries, oil terminals and ports, repair shops, food industry, detergent, and chemical production industries, automobile manufacturing, and petrochemical industries. The advantages of this method are:

