Dredging - is an excavation activity or operation usually carried out at least partly underwater, in shallow seas or fresh water areas with the purpose of gathering up bottom sediments and disposing of them at a different location. Dredging can create disturbance in aquatic ecosystems, often with adverse impacts. The activity of dredging can create the following principal impacts to the environment:
- Release of toxic chemicals (including heavy metals and PCB) from bottom sediments into the water column.
- Short term increases in turbidity, which can affect aquatic species metabolism and interfere with spawning.
- Secondary impacts to marsh productivity from sedimentation
The Client's Needs
Reason for Dredging
To increase the flow of river by widening it, which in turn would allow a larger flow to the adjacent Drinking Water Treatment Plant. In order to avoid sediment transfer from the dredging location, the Total Suspended Solids (TSS) had to be limited to avoid the transfer of material. The TSS value to be respected was less than 25 mg/L. The Client needed a temporary water treatment solution to ensure this limit was respected.
- Flowrate Range: 700 - 1,200 m3/d
- Sludge Treatment - Thickening by Polymer injection in separate tanks. The supernatant was then redirected to the feed of the ACTIFLO®. The thickened sludge was removed and disposed of offsite by Veolia Environmental Industrial Services