Gravity oil-water separator

Gravity-type oil-water separator | Purely physical separation · No reagents required · Stable operation

A gravity oil-water separator is a device that separates oil and water based on the density difference and hydrostatic pressure. It requires no chemical reagents and operates with little or no power. After oily wastewater enters the separator, optimized hydraulic channels and extended residence time allow suspended oil droplets to naturally rise to the oil collection area, while heavier particles sink to the sludge hopper, ultimately achieving three-phase separation of oil, water, and sludge. This equipment has a compact structure with no easily damaged moving parts and is widely used in oil separation of catering wastewater, pretreatment of industrial oily wastewater, and drainage of oil depots and gas stations.

core components

Inlet Rectification Zone: Water is evenly distributed using baffles or guide tubes to eliminate turbulence and improve separation efficiency.

Separation Zone: Utilizes inclined/corrugated plate coalescing modules (optional) or a horizontal flow design to increase the effective separation area and accelerate oil droplet buoyancy.

Oil Collection Zone: An oil drain trough or collection pipe is installed at the top for manual or automatic oil drainage.

Sludge Hopper: A conical structure at the bottom collects settled sludge, sand, and heavy oil (specific gravity > 1), which is periodically discharged.

Outlet Regulating Device: An adjustable overflow weir or outlet control valve stabilizes the outlet water level.

Ventilation Pipe and Observation Port: Ensures safety and ease of maintenance.

Working principle

Oily wastewater enters the rectifying zone through the inlet, where its flow rate slows and becomes more uniform. It then flows upwards or horizontally through the separation zone. During the residence time (usually 30-60 minutes), tiny, dispersed oil droplets collide and merge, floating to the top oil collection zone due to their lower density than water. Solid particles with a specific gravity greater than water and some heavy oil settle to the bottom sludge hopper. The supernatant is discharged through the overflow weir. The floating oil in the oil collection zone can be periodically discharged by opening a valve or collected by an oil skimmer, while the sludge is discharged through the bottom drain outlet.

Main advantages

Energy-efficient or extremely low-energy consumption: Standard models rely entirely on gravity flow, requiring no chemical dosing or power; an automatic oil discharge mechanism (extremely low power) is optional.

High separation efficiency: With the coalescence module, oil droplet removal rates exceeding 90% for particles larger than 60μm are achieved, with effluent oil content ≤50mg/L.

No moving parts (basic model): High reliability, virtually maintenance-free.

Corrosion-resistant materials: Optional materials include epoxy-coated carbon steel, 304/316 stainless steel, FRP (fiberglass reinforced plastic), and HDPE (high-density polyethylene).

Flexible installation: Above-ground or underground design, customizable to suit site space.

High adaptability: Can handle vegetable oils, animal oils, mineral oils, and petroleum hydrocarbons.

Technical parameters

Processing flow rate: 0.5 – 100 m³/h (larger sizes can be customized)

Separation efficiency: ≥90% (oil droplets ≥60μm)

Residence time: 30 – 60 min

Operating temperature: 0 – 60℃

Inlet water oil content: ≤5000 mg/L (recommended for pretreatment of high concentrations, using in series)

Outlet water oil content: ≤50 mg/L (depending on oil properties and coalescence module)

Material: Corrosion-resistant carbon steel / 304/316 stainless steel / fiberglass / HDPE

Installation method: Above ground (bracket) or buried (thickened and reinforced)

Application areas

Oily wastewater separation from restaurant kitchens (upgrade and replacement of grease traps)

Rainwater and oily water from auto repair shops, car washes, and gas stations

Drainage pretreatment from steel, petrochemical, and machinery processing workshops

Primary separation of produced water from oil fields

Ballast water from ships and oily wastewater from ports. We can provide hydraulic calculations and coalescence module selection based on oil characteristics, flow rate, and discharge standards. We welcome on-site parameter requests for customized design solutions.

Company Profile

AA SS AQUA HITECH CO., LTD. was established in 2005 in Shenzhen, China. It is a leading technology enterprise specialized in the design, manufacturing, installation, commissioning and maintenance of technical solutions for high-difficulty industrial wastewater treatment projects.

Since its establishment, the company has been fully committed to the research of treatment technologies for high-difficulty and refractory industrial wastewater, wastewater recycling and reuse technologies, and wastewater zero-discharge technologies. It strives to achieve low project costs, high outputs and optimization of total social resources.

The water treatment technology solutions and achievements developed by the company have been widely applied in multiple fields of high-difficulty and refractory organic wastewater treatment, including pharmaceutical wastewater, chemical wastewater, pesticide wastewater, laboratory wastewater, coal chemical wastewater, petrochemical wastewater, breeding wastewater, slaughterhouse wastewater, semiconductor wastewater, printing and dyeing wastewater, coating wastewater, landfill leachate, food processing wastewater, mechanical processing wastewater and domestic wastewater.

Adhering to the business philosophy of leading technology, first-class quality and sustainable service, the company endeavors to provide customers with strong technical support and realize the sustainable development and utilization of water resources.

The electrochemical wastewater treatment equipment independently developed and invented by our company can achieve a removal rate of over 99% for COD and ammonia nitrogen in refractory industrial organic wastewater featuring high salinity, high toxicity, high concentration and strong acidity or alkalinity. It has solved the long-standing problem of high-difficulty and complex wastewater treatment in the industrial wastewater treatment industry, representing a significant breakthrough in the treatment scope, methods and effects of high-difficulty and complex industrial wastewater.

CQDHX SERIES EO Electrochemical Advanced Oxidation Technology

Cutting-edge Electrode Manufacturing Technology

Over a 15-year period starting from 2010, we have been dedicated exclusively to the R&D, manufacturing and application of electrodes. Having completed more than 3,000 verification tests on electrode materials and manufacturing processes, as well as over 5,000 experiments on different types of highly complex wastewater, we have tailored the compositions of electrode substrates, surface materials and the deposition conditions of electrode surfaces by integrating the characteristics of various highly complex wastewater types. This has enabled us to achieve optimal performance in treating different categories of highly complex wastewater.

The CQDHX Series Electrode Modules are capable of meeting the requirements for treating highly complex industrial wastewater under extreme conditions. They can effectively remove organic matter (COD), ammonia nitrogen, toxic substances, bacteria, chromaticity, phosphorus and various heavy metals from refractory industrial organic wastewater characterized by high salinity, high toxicity, high concentration and strong acidity or alkalinity.

Working Mechanism of CQDHX SERIES EO Electrode Modules

Electrochemical oxidation is a technology that utilizes an applied electric field to drive chemical reactions for pollutant degradation. Its core reaction occurs at the anode of the electrolytic cell, and the operating mechanisms are primarily categorized into two types: direct oxidation and indirect oxidation, which often function synergistically.

Direct Oxidation Mechanism: Pollutant molecules migrate to and adsorb onto the anode surface. Subsequently, the anode, acting as an electron acceptor, directly extracts electrons from the pollutant molecules, causing their oxidative decomposition. This process is controlled by the mass transfer rate and relies on the catalytic activity and adsorption properties of the anode material, exhibiting a certain degree of selectivity towards different pollutants.

Mechanism of Indirect Oxidation: The anode does not directly oxidize pollutants. Instead, it generates highly oxidizing agents by electrolyzing components within the solution. These agents then diffuse into the bulk solution and carry out homogeneous oxidation of the pollutants. Depending on the type of oxidants generated, the main pathways can be categorized as follows:

Electrochemical oxidation achieves pollutant degradation through two main mechanisms: electron transfer at the anode surface and the in-situ generation of highly oxidizing species. In practical applications, particularly for complex wastewater systems, direct and indirect oxidation often work synergistically. By optimizing electrode materials and process parameters, efficient and advanced treatment of organic pollutants can be achieved.

 Technical Advantages

High Salinity Tolerance: It can effectively remove COD and ammonia nitrogen from unsaturated saline wastewater with a removal rate of up to 99%.

High Toxicity Tolerance: It can effectively remove COD and ammonia nitrogen from highly biotoxic wastewater with a removal rate of up to 99%, while efficiently eliminating the biological toxicity of the wastewater.

High Concentration Tolerance: It can effectively remove COD and ammonia nitrogen from high-concentration organic industrial wastewater with a COD level of ≤ 450,000 mg/L, achieving a removal rate of up to 99%.

Strong Acid-Alkali Tolerance: It can effectively remove COD and ammonia nitrogen from strongly acidic or alkaline wastewater with a pH value ranging from 1 to 11, with a removal rate of up to 99%.

High Safety: The equipment operates at a DC voltage ranging from 3 to 15V, causing no harm to the human body.

No chemical agents are added during wastewater treatment, and no residues or solid wastes are generated.

The electrode modules operate without scaling or clogging.

The equipment achieves a removal rate of 75–100% for high ammonia nitrogen, cyanide breakdown, decolorization, and other pollutants.

No pH adjustment is required for incoming wastewater, which significantly saves on acids, alkalis, labor costs, and floor space, while avoiding secondary pollution.

No water dilution is needed to reduce the salinity of incoming wastewater, decreasing the system’s treatment load and conserving resources.

No water dilution is needed to reduce the COD concentration of incoming wastewater, decreasing the system’s treatment load and conserving resources.

The equipment features a small footprint, occupying approximately 2% of the floor space required by traditional processes of the same capacity.

The equipment has no special environmental requirements and can be installed in well-ventilated, rainproof, non-explosion-proof areas.

The equipment operates with no noise and zero discharge of secondary pollutants.

It features fully automated operation, which is simple, safe, and does not require on-site personnel monitoring.

Equipment Specifications: 0.5T–1000T/h

Electrochemical Oxidation Equipment for Treating Common Pollutants

Application Scenarios:

Treatment of Refractory and Toxic Pharmaceutical Wastewater

Treatment of Refractory and Toxic Chemical Industry Wastewater

Treatment of Refractory and Toxic Pesticide Wastewater

Treatment of Refractory and Toxic Laboratory Wastewater

Treatment of Refractory and Toxic Coal Chemical Industry Wastewater

Treatment of Refractory and Toxic Petrochemical Wastewater

Treatment of Aquaculture Wastewater

Treatment of Slaughterhouse Wastewater

Treatment of Refractory and Toxic Semiconductor Industry Wastewater

Treatment of Refractory and Toxic Dyeing Wastewater

Treatment of Refractory and Toxic Painting/Paint Coating Wastewater

Treatment of Refractory and Toxic Landfill Leachate

Treatment of Food Processing Wastewater

Treatment of Refractory Machining Wastewater

Treatment of Domestic Sewage