Introduction

Hello! We are John and Kody, and we are going to be relaying to you the knowledge and uses of polymers in the cleaning and filtration of water to be used or released back into the environment. We will be talking about where in the process they are used, their properties/effect, and which ones are used.

Water treatment

A general water treatment process goes through a particular set of steps and steps can be added or omitted if need be based on the treatment process. First water flows into a tank for primary clarification. Clarification is the process by which solids are allowed to settle, which eliminates a good chunk of the solids in the water. Since many are tiny and are not heavy enough to resist buoyancy factors, chemicals must be added to get them to stick together and clarify out.

Coagulants

Coagulants remove or add electrical charges, which allow the particles to stick together.  Most particles in a typical solution of water that requires treatment are negatively charged particles.This process is called flocculation. A variety of things could be used as a coagulant which includes polymers.

After flocculation of these particles occur they travel to a secondary clarifier to settle out.

coagulant 1

coagulant 2

Types

There are different types of polymers that are used in water treatment. They can be stored and transported in different forms.

There is a dry powdered form which is easy and cheap to transport but it is often difficult to mix, requiring special equipment to process it into solution form.

There is a liquid form which is a concentrated solution of a polymer which only requires diluting to use, but it is more difficult and possibly more expensive to transport.

And finally there is an emulsion form which are polymer dissolved in droplets of water in oil. These are not 100% active and can separate out over time which requires occasional mixing. The upside is these can account for various charges in treatment.

Which polymers are used?

There are a few major types of polymers used and then there are some minor ones used as well.

Major

Polyamines   –   nonionic bridge particles together. Anionic and cationic formed by copolymerizing with acrylic acid or cationic monomer.

Poly (Diallyl Dimethyl Ammonium Chloride) – similar to polyamines but can be copolymerized with other monomers.

Polyacrylamides – usable in various pHs

Minor

Polyethylene-imines

Polyamides-amines

Polysaccharides – guar gums, used in acid

Bentonite Clay

The many uses of Bentonite Clay range from coagulant to filter aid. It is a highly effective chemical, in granular form, for the purification of wastewater and sludge dewatering. It is composed of inorganic minerals and other proprietary compounds specially produced to absorb a wide variety of contaminants, and will encapsulate suspended solids, many organic compounds and toxicants. Bentonite clay can be dispersed into the treatment tank manually with a measuring scoop or continuously with a dry feed system, providing easy-to-use one-step chemistry.

Bentonite Clay

Typical Properties:

  • Granules, beige
  • Odorless
  • pH@5%: 8-9

Diatomaceous Earth Filter Aid

Diatomaceous earth is a natural filter aid comprised largely of pure silica. This mineral powder can improve the filtering capacity of inert filters by helping to remove suspended solids, semi-colloids and oily liquids. It is also used for pre-coating the septum in a variety of filtering devices such as filter presses, vacuum filters, leaf filters, tubular filters and other specialty filters. In addition to being extremely effective, diatomaceous earth is also economical, making it a great choice for facilities managers looking to boost the productivity of their wastewater systems without making huge upgrades.

With an odorless makeup, specific gravity of 2.3 and a pH of 5-7 S.U (10% slurry), it’s a great choice for industrial wastewater.

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Perlite

Perlite is the filter aid of choice for many industrial and sludge dewatering applications, due to its high efficiency, effectiveness, and utility as a sludge dewatering agent. The chemical leaves no residual color, and offers very good precoat conditioning.

Perlite

Typical Properties:

Can be diluted in water to 10% slurry
Fine white powder
Odorless