It took me years to finally realize that more polymer is not better, no matter how many times my outstanding polymer salesperson (Randy H.) tried to tell me this. As operators, when we have, for example, sludge conditioning problems on a dewatering unit, such as a belt filter press, we always think the problem is that we don’t have enough polymer. So our inclination is to turn up the polymer feed pump. But too much polymer is quite detrimental to good conditioning. Too much polymer, rather than increasing the tendency of solids to come to together, can actually result in particles being repelled from one another. This is referred to as re-stabilizing as illustrated in in Figure 1.
Figure 1: Particle Restabilization Due to Overfeeding Polymer
Use caution when deciding on a dosage change and keep in mind that a reduction in the polymer feed rate may result in better performance. This is especially true when feeding polymer to a secondary clarifier, a common practice for industrial wastewater treatment systems. Notice in Figure 2 that the polymer dosage is shown as being 10 ppm. If you have to go too much higher than this dosage you need to do some jar testing to find a more effective polymer product.
Figure 2: Polymer Feed to a Secondary Clarifier