FFS REFINERS TEAKWOOD ROAD HAS NEW UPGRADED EFFLUENT TREATMENT PLANT

Environmental technology is developing rapidly in South Africa to facilitate conformance with more stringent environmental legislation. FFS Refiners has developed the technology for processing highly emulsified waste oils and contaminated effluent waters. FFS Refiners at Teakwood Road in Durban has recently upgraded their effluent plant (conforms to Petroleum Industry requirements), which is capable of handling most contaminated effluent to meet limits set in the Durban Transitional Metropolitan Council Sewage Disposal Bylaw. It is now capable of processing 20 kilolitres per hour of effluent. This improvement will make the treatment of contaminated effluent waters more widely accessible to local industry, thereby reducing the impact of industrial effluent on the already overloaded water treatment works in the Ethekweni Municipality. It has also assisted FFS Refiners Teakwood Road in striving towards continuous improvement.

EFFLUENT WATER AT TEAKWOOD ROAD
Effluent water on site is derived primarily from the raw material. FFS Teakwood’s main feedstocks are ships' slops, refinery off-spec material, and other waste oil streams. The water content of these waste streams varies from 10% to 50%. This water is removed from the oil through various processes on site, including Forced Feed Evaporation and centrifuge equipment. This water contains approximately 2000ppm of oil and requires treatment prior to discharge to the sewer.

THE PROCESS
Effluent enters the system into the Effluent Buffer Tank, in which it is automatically dosed with acid to achieve a pH of <5.


Static separator

From the Buffer Tank the oily effluent water (2% oil) enters the Static Separator in which the oil and water naturally begin to separate due to their relative specific gravities. Oil is skimmed off the surface of the effluent and returned to the waste oil plant. Oil content of the water after the separator will have dropped from ~2% to ~0.5%.

DAF Unit
Effluent is fed into a saturator along with compressed air, which dissolves into the water under pressure. The compressed mixture is then released into the Dissolved Air Flotation (DAF) unit (oil now ~1000ppm) whereby the tiny bubbles that form, attract the dispersed oil droplets and float them to the surface. With the release of pressure the tiny air bubbles rise to the surface along with the associated oil. The oil is then skimmed off the surface of the effluent and returned to the waste oil plant. The oil content in the effluent should drop to around 300ppm – 400ppm after the DAF unit.

Coagulation Tank

Effluent is dosed with lime slurry in the coagulation tank. The lime again preferentially associates with the oil in the effluent.

Flocculation Tank

The lime/effluent mixture is then dosed with a polymer flocculent prior to discharge into the Clarifier Tank. The lime drops out of the water to the bottom of the Flocculation Tank.

Filter press (below)/Decanter (above)

After the coagulation tank effluent water it is fed through a filter press or centrifuge. A dry lime / oil sludge is derived from the filter press or decanter and will be disposed of to an H: h landfill and a safe disposal certificate obtained. Clean water from the filter press is re-introduced into the Lime Dosing tank.

Effluent taken from DAF unit and the final result after

Final effluent water with oil content of less than 50ppm weirs over the edge of the Flocculation Tank and into the municipal oil and grease trap. From this trap the effluent flows through a flow meter and into the sewer.

CONCLUSION

The process, that was designed and built by FFS is robust and stable, and capable of dealing with the wide range of effluent water sources received. Oily effluent water processing is offered by FFS to industry in Durban and to shipping under the Marpol Agreement. FFS Refiners thus offers another solution to the growing amount of contaminated effluent water, which would otherwise in some cases not be treated prior to disposal.