Wastewater treatment of petroleum depot

Wastewater characteristics

The nature of the oil is a viscous liquid, usually with a characteristic odor lighter than water and usually insoluble in water. They oxidize very slowly, can last up to 50 years.

In reality, oil exists in water in many different states, and it is difficult to accurately determine these components by experiment. Commonly oil exists in water in the following 4 states:

Free form: In this form, the oil will float to the surface of the oil, the oil exists as free oil particles or mixed with a little water, the free oil will float to the surface due to the lower specific gravity of the oil. relative to the specific gravity of water.

Mechanical emulsion: There are two types of mechanical emulsions depending on the diameter of the oil drop:

Several tens of micrometers: low stability.
Smaller type: high stability, similar to glue.

Chemical emulsion: A form formed by chemical agents (soap, caustic soda, detergents) or asphaltene chemicals that change the surface tension and chemically stabilize the dispersed oil.

Solubilized form: Molecules dissolve as aromatics.

In addition, insoluble oils form a thin film around suspended solids, which can affect the ability of suspended solids to settle or float when forming unsettled aggregates.

Proposed technology diagram


Production wastewater containing oil and grease generated during the operation of the Western Petroleum Depot is collected along pipelines and trenches and then led to a centralized treatment station.

Wastewater receiving and conditioning tank is the first oil-contaminated wastewater receiving facility of the Treatment Station. This work is responsible for receiving and regulating the flow and quality of wastewater. Oil-contaminated wastewater is transported by 02 pumps to transport wastewater from the wastewater receiving and conditioning tank to the DAF flotation treatment device. The pump operates on the signal of the level float.

DAF flotation equipment is an oil treatment equipment imported completely and synchronously from abroad. The flotation device consists of 3 treatment tanks placed in series. Wastewater from the conditioning tank is pumped into the mixing tank, where the coagulant is added to the water, thanks to the operation of the high-speed agitator, the coagulant is mixed with the wastewater. Then the wastewater is flowed to the reaction tank, where the colloidal agent, PAA, is mixed with the wastewater by a low-speed agitator before flowing to the DAF flotation tank.

Diagram of DAF . flotation device system

At the DAF flotation tank. Thanks to the operation of equipment including high pressure pump, air compressor and pressure vessel. Micro-bubbles are generated in the treatment tank. These air bubbles have an attractive force that adheres to the particulate matter in the wastewater, grease and oil and floats on the surface of the tank to form a layer of foam or scum floating on the surface of the tank. After that, the foam removal system will remove this layer of scum and lead to the pipeline to the waste oil tank. The sludge deposited in the flotation tank will be periodically discharged to the sludge drying yard by the operation of the solenoid valve. Clean water after the treatment tank is usually drawn from the end of the flotation tank, and is led along the pipe to the receiving source

+ The waste sludge stored at the sludge drying yard, the waste oil stored in the conditioning tank and receiving waste oil will be periodically removed and treated according to regulations. Waste oil containers after the flotation device are also closed and transported for treatment according to regulations.