As part of a site remediation project, Hexavalent chrome and Xylene needed to be removed from the groundwater beneath a former printing works north of London. It was required to treat 200 m3 per day of water from 4 shallow wells spread across the site. The resulting treated water was discharged to the public sewer.

The water contained up-to 200 mg/l of Chrome (VI) and up to 100 mg/l of Xylene.

The Discharge Limits were set as follows:
Chrome (VI)	Less than 150 mg/l
Xylene	Less than 50 mg/l

Groundwater pump and treat project at former printing works using OPS media absorber vessels to remove Hexavalent Chrome and Xylene.

Process description

Incoming solids were removed by filtration though a duplex solids filter. Xylene was removed by absorption through a 1,500kg bulk absorption vessel packed with RM25 media. Chrome VI was absorbed by two 200kg bulk vessels containing RM40C media. Final polishing was achieved through a mixed bed filter of GAC and RM40C.

Results

The pump and treat program lasted for 6 months with random sampling by the Environmental Agency who took 34 discrete samples during the programme, all of which were in compliance with the required discharge limits.