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Non-hazardous flocculants – using chitosan in waste water systems

Chitosan is a flocculant that has been proven effective at removing both suspended solids (colloids) and dissolved contaminants from waste water. Additionally, interest in chitosan has been further spurred on by the fact that, unlike many other flocculants used widely in industry, chitosan is not harmful to health, is environmentally benign, readily biodegradable, does not bioaccumulate, and is renewable.

Chitosan is a natural bio-polymer derived from chitin, the chemical that the exoskeletons of all insect, crustaceans and fungi are composed of. When this hard chitin polymer is converted into a soluble chitosan it possesses cationic properties.

In waste water systems chitosan is best added to a flocculation tank, where it will precipitate out compatible contaminants in a process that can take seconds to hours (at most). Once the contaminant is attached to the polysaccharide backbone the whole molecule falls out of solution and clumps together with others that have also precipitated. This macro-particle can then easily be removed depending upon its density. If it is denser than water it will settle on the bottom of the tank as a sediment, if it is lighter it can be skimmed off the top of the tank, and if it is equal to water the tank can be agitated and the macro-particles removed by trapping them in a filter mesh.

Some agitation of the flocculation tank is desirable straight after adding the chitosan to ensure that it has fully dissolved not just settled on the bottom. After the initial agitation the tank can be either continually mixed or left to settle (depending upon the system in place).

Chitosan is most effective at removing anionic contaminants, especially if the water being treated is pH neutral or alkaline. However, even some contaminants that do not match these properties can also be removed by chitosan, so it is always worth getting a sample to test chitosan in your system with your challenging contaminant.

When used in waste water systems, chitosan represents an environmentally friendly alternative to a number of toxic flocculants (clarifying agents), including; ferric chloride, aluminium chlorohydrate, sodium aluminate, polyacrylamide, aluminium sulfate, alum, calcium oxide, and calcium hydroxide.

Polyacrylamide is of particular comparison as, like chitosan, it is a cationic polymer. However, its use as a flocculant is highly questionable for two reasons. Firstly, it represent the mass release of a synthetic polymer into the environment. Secondly, polyacrylamide can contain residual contamination with the monomer acrylamide. Acrylamide is a know neurotoxin and carcinogen. Therefore, swapping out acrylamide for chitosan is a wise option to consider for any water treatment operation!

Until recently chitosan has been too expensive for industrial/professional use, with applications restricted to cosmetic/medicinal products. However, as a primary manufacturer, Eutrema can offer bulk volumes at prices that are now making it a commercial reality in waste water treatment facilities. We can supply chitosan of various grades, sources, and formulation types, so that you can tailor the product to your exact contaminant and situation. So please contact us to arrange for a sample.

The Eutrema product is of high purity, of high solution strength, highly effective and virtually free of insoluble particles.

Below are some examples of chitosan flocculating out contaminants from various solutions:

Removal of humic acid from a highly concentrated solution. Untreated sample on the left.

chitosan flocculants humic

Removal of yeast cells from ‘unfined’ beer. The beer on the left has only been filtered, the beer on the right has had chitosan added and has been filtered. Thus creating a beer that does not need fish-derived flocculants; such as isinglass.

chitosan flocculants beer

Precipitation of alginic acid from a solution it was previously dissolved in.

chitosan flocculants alginates

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