Primary (Chemical) Sludge Dewatering Application

I wanted to share my real-time troubleshoot experiences in this document. As we knew there are various types of sludge that have a specific ionic characteristic. Below are the major types of sludge and recommended polymers range

1)   Primary sludge: Low charge Anionic poly

2)   Biological Sludge: High Charge Cationic

3)   Digested primary Sludge: Low cationic

4)   Mixed Sludge: Medium cationic

I Would like to share here the most interesting and repeated experience in my career that primary sludge dewatering application. When we conduct a Dewatering test with fresh primary sludge, in many cases we get better results with Low charge anionic polymers. As long as they run with their normal operation they don’t get any issues with the dewatering results but if they stop dewatering unit due to breakdown for some time then slowly primary sludge converts to digested sludge in a period of time (approx. 15-20 days ) under partial anaerobic conditions. Once they resume the dewatering process they don’t get the same dewatering results as they get previously. You should be ready for the statement from the particular customer that your polymer not working well. As discussed, digested sludge characteristics completely different than fresh primary sludge. In that case, Cationic polymer works better than Anionic polymer. Apart from this, there are other points that are also important to have in our checklist to find the root cause.

Find the polymer solution age

Check the dosing pump function

Check the polymer solution characteristic ( Anionic or cationic)  

Thank You