One could, (and many have), written a book on the use and misuse of polymers in wastewater treatment. This report will go into only a brief introduction 

 

Polymers are of three types, cationic (positive), anionic (negative), or non-ionic. In treating metal hydroxides, anionic polymers are typical. As you may know, the types and combinations of polymers available on the market today are numerous. Choosing one over the other is more a game of trial and error than exact science. I have found that the best method in choosing polymers is to do my own jar testing in the field for each client. Jar testing is simple. It lets you get a feel for the client’s particular stream. Samples of various polymers are easy to get from the distributors. Polymers come either in dry or wet form. Both require dilution before use. I prefer the wet form because the dry can absorb water from the atmosphere and foul easily. Polymers have a definite shelf life of about one to two years for dry and as little as ten days for wet. Some clients prefer the dry because of cost and not keeping drums of liquid on site. 

 

If you have ever worked with polymers, you know how slimy they are. They absorb water and have the tendency to turn water into Jell-O if not blended properly. The best place to start is to learn about how to prepare and dilute the polymer before jar testing. It is easy once you do it a couple of times. Ask your supplier for help. 

 

In adding a polymer to the wastewater, remember that a polymer’s job is to attract and clump particles together. This adds to the weight of the waste particles and aids in the settling or filtering in final removal. Since opposites attract, an anionic ( -) polymer will hold on to positive particles (not just metals). Polymers need to be blended first quickly into the waste stream (called flash mixing), and then allowed to develop slowly and gently. Equipment design here is very important.