This term is used so frequently in polymer treatment of raw, process and waste water that it deserves an adequate definition. Suspended solids is a common term used to describe almost any type material that is found in a water solution that isn’t water, but a floating particle, visible to the eye. A suspended solid may also be classified as a contaminant to be removed for disposal or a valuable substance, ore or a food product for example, that ought to be recovered through polymer treatment techniques. Some common methods for treating suspended solids include:
Sedimentation: Sedimentation is a process in which suspended solids are allowed to settle out of water by gravity. In this process, the water is allowed to sit in a tank or even a lagoon for a period of time, during which time the physically heavier suspended solids, particulate matter, will settle to the bottom. The settled solids can then be removed from the bottom of the tank or lagoon. Polymer treatment can be very effective in improving the sedimentation performance.
Filtration: Filtration is a process in which water is passed through a specific type of media, such as cloth, wound filaments, sand and gravel, fibers or screening to remove the solids which will not on their own settle to the bottom of the clarifier or treatment tank. This process can be used alone or prior to other treatment methods, such as coagulation and flocculation.
Coagulation and flocculation: Coagulation and flocculation are processes in which chemicals are added to water to cause suspended solids to clump together into larger particles, known as flocs. The flocs can then be more easily removed from the water using sedimentation or filtration. There is a easy to read report containing more definitions and examples of both coagulation and flocculation.
Membrane filtration: Membrane filtration is a process in which water is passed through a plastic film with sub-micron holes through which allow only water molecules can pass. The non-water ionic species do not penetrate the film but are sent to a collection portion of the membrane system. The membrane system selectively removes suspended and dissolved solids and other impurities. Common membrane systems are reverse osmosis (RO), ultra-filtration (UF), nano-filtration (NF), micro-filtration (MF), membrane distillation and other purification modalities. These processes can be used alone or in combination with other treatment methods, such as coagulation and flocculation.
Biological treatment: Biological treatment methods, such as activated sludge treatment or bioreactors, use microorganisms to break down and remove suspended solids from water. It is a common practice to dose a waste stream with facultative bacteria or enzymes to feed and grow unwanted or hazardous contaminants in the stream.
The specific treatment method or combination of methods used for treating suspended solids will depend on factors such as the type and concentration of suspended solids in the water, the flow rate, and the available treatment infrastructure. The manufacturer can make helpful recommendations.