When biodiesel is produced from rapeseed oil, both the feedstock and the finished product can enter the wastewater system. This was the case at one manufacturer, where the discharged wastewater had to meet the local treatment plant’s limits.
During peak periods, when particularly large quantities of oil and biodiesel entered the drainage system, the oil separator could no longer retain the entire oil load.
Considerable costs were also incurred because a vacuum tanker had to empty the oil separator regularly.
The situation was therefore unsatisfactory.
A solution was therefore needed that could continuously remove the accumulated oil.
This would prevent the separator from being overloaded while allowing the company to collect the oil itself for disposal or recycling—a far more cost-effective alternative to repeatedly calling a vacuum tanker.
An oil skimmer was well suited to the task: it could operate without constant supervision and remove the oil accumulating inside the oil separator. The recovered oil would then be directed into a designated IBC.
To verify that a hose-type oil skimmer could remove the floating phase and deliver the required result, a frame-mounted FRIESS Type 1S oil skimmer was tested on the separator.
The oil skimmer operated continuously and removed the oils and fats entering the wastewater stream.
After only a short period, it was clear that the skimmer was removing substantial quantities of oil and fat, as shown by the steadily rising level inside the IBC.
Limit exceedances at the downstream monitoring station also declined.
There was initially concern that the collector hose would have a short service life because organic oils and fats can attack plastics and cause them to swell. In practice, this concern proved only partly justified. Although the collector hose lost some rigidity, this did not affect its conveying capacity or otherwise impair the oil skimmer. Its average service life was approximately six months.
After the successful proof of concept, the oil skimmer was purchased. Further trials are now being carried out at other points in production to reduce the wastewater load upstream of the separator and remove oils and fats as close to the source as possible.
The oil skimmer is currently being tested at two additional locations:
