Polymers are commonly used in the dewatering of dredged material to improve the efficiency of the dewatering process on equipment such as screw presses, gravity belt thickeners, belt filter presses, plate and frame filter presses and centrifuges. Dredged material is usually a mixture of water, non-aqueous liquid pollutions and sediment, which can be difficult to separate. Polymers can be applied to the dewatering equipment feed to help flocculate the suspended solids. They are then more dense and able to lose the entrained water to produce a dry cake of various solids’ content. The polymers allow the equipment to produce high solids’ cake, lower solids’ filtrate improve dredging efficiency.
There are several types of polymers that are commonly used in the dewatering of dredged material including:
Polyacrylamide (PAM): PAM is a synthetic polymer that is commonly used in dewatering applications. A synthetic polymer is a very long chain man-made chemical that has billions reaction points on the chain. These points are specifically attracted to the suspended solids. This allows solids, mud, silt, debris, to be separated from the dredging material while clean water is discharged from the process. PAM can be produced in both liquid and powder form.
Polyelectrolytes: Polyelectrolytes are a type of polymer that contains charged functional groups.
They are various cationic and anionic radicals the are bonded to the polymer chain for exacting performance capabilities. They are effective at flocculating suspended solids.
Polyethylene oxide (PEO): PEO is a water-soluble polymer that is effective at flocculating suspended solids. It is commonly used in conjunction with other polymers to improve the efficiency of the dewatering process.
Polymers can be added to the dredged material using a variety of methods, including dosing pumps, batch mixing, or continuous mixing. The amount of polymer needed will depend on the characteristics of the dredged material and the desired level of dewatering and cake dryness.
Polymers are an important ingredient in dewatering systems for dredged material, helping to improve the efficiency of the process and reduce the volume of dry cake sent for disposal. By improving the clarity of the water and separating the suspended solids, polymers help ensure that dredged material can be safely and effectively processed.