What are Flocculants？
Flocculants substances that promote the agglomeration of fine particles present in a solution, creating a floc, which then floats to the surface (flotation) or settles to the bottom (sedimentation). This can then be more easily removed from the liquid. For example, a flocculant may be used in swimming pool or drinking water filtration to aid removal of microscopic particles which would otherwise cause the water to be turbid (cloudy) and which would be difficult or impossible to remove by filtration alone.
Types Of Flocculants
Flocculants can be generally divided into two categories: inorganic flocculants and organic flocculants according to their chemical composition. Inorganic flocculants include inorganic flocculants and inorganic polymer flocculants. organic flocculants include synthetic organic polymer flocculants, natural organic polymer flocculants and microbial flocculants.
Inorganic Flocculants
Advantages of inorganic Flocculants
Enable highly charged ions to give a high charge density to neutralise suspended particles, which allows hydrated inorganic hydroxides to form and produce short polymer chains that enhance microfloc formation and heavy floc.
Capable of removing a portion of the organic precursors which may combine with chlorine to form disinfection by-products.
Low unit cost and widespread availability.
Organic Polymer Flocculants
Polyacrylamide
PolyDADMAC
Polyamine
Styrene sulfonate
Lignosulfonate
Acrylic acid
Methacrylic acid
Advantages of organic Flocculants
Enable relatively low charge density to neutralise lower charged suspended particles, more effectively. Produce longer polymer chains that enhance microfloc formation without metals or hydroxides.
Capable of removing a portion of the organic precursors which may combine with chlorine to form disinfection by-products.
Produce small floc volume.
Liquid forms, non-corrosive, ready for direct use.
Do not impact and are rarely or marginally affected by pH.
When will we use inorganic or organic flocculants? in what situation?
The choice of using inorganic or organic coagulants depends on several factors, including the nature and characteristics of the water to be treated, the specific contaminants to be removed, the required water quality standards, and the cost-effectiveness of the coagulation process.
Here are some general guidelines:
Inorganic coagulants such as aluminum sulfate (alum), ferric chloride, and polyaluminum chloride (PAC) are commonly used for treating surface water and groundwater sources containing high levels of turbidity, suspended solids, and organic matter. They are effective in removing these contaminants and are relatively inexpensive compared to organic coagulants.
Organic coagulants such as polyDADMAC, polyamine, polyacrylamide, chitosan, and tannin-based coagulants are typically used in situations where the treated water must meet stringent water quality standards or where the presence of organic contaminants is a concern. They are effective in removing color, organic matter, and some heavy metals. However, they are generally more expensive than inorganic coagulants and may require higher dosages to achieve the desired treatment effect.
In summary, the choice of coagulant depends on the specific water treatment needs and the desired water quality standards.
