The Esso Norge AS (ENAS) plant in Valløy is one of the oldest industrial sites in Norway. Between 1900 and 1993 refinery related activities were carried out on these grounds. After the closure of the refinery, cleaning- and dismantling activities took place, and a thorough survey of the site was executed. Widespread contamination was reported and a full remediation of the site was considered necessary.
During the refining process, various fuels and petroleum-related products were produced, including transformer- and lubricating oil. These oils were produced by means of vacuüm distillation and were cleaned by acidification and filtration. Residues of the production process included acid tar and bleaching earth, which have settled on the grounds.
Groundwater was heavily contaminated with suspended solids, TPH, PAH and benzene. In order to meet the discharge standards for the Oslofjord, the groundwater had to be treated in the first place.
Based on pilot tests, Purazur NV designed an appropriate physicochemical water treatment installation for purification of the comtaminated groundwater and the run-off water in the excavation zone. The process successively consisted of an oil/water separator, influent buffer, coagulation step, neutralisation step, flocculation, an automatic sand filter backwash, and active carbon filtration.
Apart from the polluents that are listed aboven, the process can also remove low concentrations of BTEX and heavy metals. The effluent of the water treatment facility is continuously monitored for turbidity, pH and flow rate.