| 摘要 |
Purificn. of backwash water passed through a filter system employed for treating oil-polluted water is claimed. The filter system is of the type comprising granular bed percolating filter(s) upstream of biological filters. A polyelectrolyte, e.g. polyamide or cationic polyamine in soln. is injected into the backwash water which is then subjected to a flotation treatment and finally recycled through the filter system. The polyelectrolyte soln. can be added to the backwash water before and after being passed through the filters to be backwashed. The flotation system can be natural or air-assisted. Backwashing efficiency is enhanced to a degree which returns the filter system to "as-new" condition. This is mainly because the polyelectrolyte destabilises the oil emulsion formed by aerated backwash water. This emulsion previously fouled the filters despite backwashing. The polyelectrolyte further promotes flotation sepn. of hydrocarbons as an easily disposable sludge. |
