CPI Filter for Industrial Effluent: Compact Oil-Water Separation

A CPI filter for industrial effluent is a pretreatment device used to separate free oil, floating oil, grease and some settleable solids from industrial wastewater. CPI stands for Corrugated Plate Interceptor. Although many buyers call it a filter, its main function is physical oil-water separation rather than fine particle filtration.

Industrial effluent can come from petrochemical plants, machinery processing, vehicle washing, steel mills, power plants, shipyards, food processing facilities, surface treatment workshops and general manufacturing sites. These wastewater streams may contain free oil, lubricants, cutting fluids, grease, suspended solids and other pollutants. If free oil is not removed early, it may reduce DAF performance, block filters, foul membranes, disturb biological treatment and increase maintenance costs.

The CPI separation process relies on gravity and coalescence. Wastewater enters the inlet distribution chamber and flows slowly through inclined corrugated plates. Because oil is lighter than water, free oil droplets rise along the plate surface. The plate structure shortens the rising distance and helps small droplets merge into larger droplets. These oil droplets then float to the oil collection zone and are discharged through an oil outlet or skimming device. Heavier solids settle into the sludge hopper and are discharged regularly. The separated water flows out for further treatment.

A typical treatment flow is:

A complete CPI oil-water separator system may include an inlet chamber, flow distribution device, corrugated plate pack, separation tank, oil collection area, oil skimmer or oil outlet pipe, sludge hopper, sludge discharge valve, outlet chamber, access cover, pipelines, valves and optional control components. Depending on wastewater properties, the equipment can be manufactured using carbon steel with anti-corrosion coating, stainless steel, FRP or other suitable materials.

For correct selection, buyers should provide more than nominal flow rate. Important parameters include average flow, peak flow, oil concentration, oil droplet size if available, TSS, pH range, wastewater temperature, viscosity, corrosiveness, required outlet oil content, installation space and downstream process. These factors affect equipment size, plate configuration, retention time, material selection and sludge discharge design.

It is also important to understand the application boundary. CPI filters are suitable for free oil and separable oil droplets, but they are not enough for stable emulsified oil, dissolved organic pollutants or soluble chemicals. If the wastewater contains surfactants, emulsified oil or complex industrial chemicals, the CPI unit may need to work with demulsification, coagulation, DAF, filtration, biological treatment or membrane treatment.

Qingdao Jinwantong provides customized CPI filters and supporting wastewater treatment equipment for industrial effluent pretreatment. Buyers can send water quality data, flow rate, oil content, TSS, pH, site layout and treatment target for technical selection and quotation.