Biochemical treatment of oil chemical wastewater

In an oil chemical plant, animal and vegetable oil and waste glycerin are used as raw materials to produce various stearic acid, glycerin, oleic acid and other products. The wastewater is blackened, CODCr, BOD5 concentration is high and acid.

At present, there are few successful examples of this kind of wastewater treatment in China. On the basis of laboratory experiments, the anaerobic baffled reactor sequencing batch activated sludge process (ABR-SBR method) is applied to treat this kind of wastewater. After more than one year of debugging and operation, the water quality of the effluent is stable, which can reach the national first level discharge standard (cb8978-96), and the equipment operation is stable

1. Wastewater treatment process

In this project, biological method is used as the main treatment process, and oil separator and sedimentation tank are used as the pretreatment process. The sludge is regularly discharged into the sludge tank and transported out after drying.

2. Main structures and equipment

1.2.1 oil separator

Horizontal flow oil separator is adopted, with hydraulic retention time of 2H. The oil slick is recovered. The plane size is 2.0m × 3.0m, and the effective water is 3.0m.

1.2.2 regulating tank

The retention time of the regulating tank is 14h. The plane size is 6.0m × 4.0m, and the effective water depth is 3.2m.

1.2.3 inclined tube sedimentation tank

The front end of the sedimentation tank is swirl reaction area, coagulation area, and the rear section is inclined tube sedimentation area. In the reaction area, the impulse of the lifting water pump is used to form a swirling flow in the reaction area, so that the lime milk can fully react with the waste water. Ca (OH) 2 can be used as a good coagulant to neutralize the colloidal substances in the waste water and form flocs, so that most of the organic matters can settle down, form obvious solid-liquid separation, improve the pH value of the waste water, and reduce the SO42 in the waste water- The concentration is favorable for the subsequent anaerobic hydrolysis treatment. The sedimentation area adopts inclined tube sedimentation, the surface load is 1.1m3/m2, and the total residence time is 2.8h. The plane size is 5.0m × 2.0m, and the effective water depth is 3.5m.

ABR reactor

Anaerobic baffled reactor (ABR). The total hydraulic retention time is 6h, and the hydrolysis reaction section is taken. The velocity in the ascending area is 2.5 m / h, the velocity in the descending area is 13.3 M / h, and the volume load is 5.5 kg / (M3 · d). Acid hydrolysis bacteria are used to hydrolyze oil into soluble substances such as glycerin and fatty acid, which are easy to be degraded by microorganisms, so as to improve the biodegradability of the influent water of SBR reaction pool, reduce the organic load of subsequent SBR reaction pool and shorten the reaction time of SBR. The plane size is 2.0m × 7.0m, and the effective water depth is 3.5m.

1.2.5 water distribution pool

The effluent from ABR reactor is stored and used as the distribution pool of SBR reactor. The residence time is 4h, the plane size is 4.0m × 4.0m, and the effective water depth is 2.0m.

1.2.6 SBR reactor

When the mass concentration of sludge in the biochemical tank is between 3500-4500mg / L, maintain its CODcr volume load, and the operation cycle is 12h, including 1 h of water inlet, 8 h of aeration, 1.0h of sedimentation, 1.0h of decanting, and 1 h of idleness. Jet aeration is adopted with a drainage ratio of 1:2. There are two SBR reactors, running alternately in different procedures. The single plane size is 5.0m × 5.0m, and the effective water depth is 3.5m.

1.2.7 sludge tank

The sludge tank adopts gravity concentration tank, and the two tanks are used alternately. The supernatant is regularly returned to the regulating tank. After concentration, the sludge is dried by pumping the plate and frame filter press, and the filtrate is returned to the regulating tank. The plane size is 3.0m × 4.0m, and the effective water depth is 3.0m.

1.2.8 filter press

Plate and frame filter press is used to treat sludge. The filtering area of the filter press is 30m2, and the sludge is discharged once a day.