Why is flocculant demand up in my secondary clarifiers?

When we use the term "bugs" for our wastewater microbial poulation, we are simplifying what is actually a community of thousands of microbial genera. The organisms form functional groups that ensure complete waste treatment. An important part of this action is the formation of Extracellular Polymeric Substances (EPS). The EPS is the glue that holds cells in a biofilm or floc. EPS is composed of polysaccharides, proteins, enzymes, and DNA that form a matrix containing bacteria, particulates, and stored organic compounds. Even filamentous bacteria are needed for "best" quality floc. As long as the filmanets are functioning in their macrostructure role and inside the floc, the flilaments are beneficial. So maintaining EPS at proper composition and levels is key to separating the biomass from treated effluent even if you use clarifiers, DAF, MBR, or other solids separation system. Now for a few common reasons why secondary polyer demand can increase:

• Filamentous bulking - bulking is where filaments bridge floc and become the dominant microbial form. If you see filaments at a 5 or 6 (Scale 0 - 6), then you should go through the identification of the filament, associated cause, and take corrective measures. This is where someone with filamentous bulking expertise can help you with the best control options.
  
  
• Non-filamentous or Zoogleal bulking - this is a problem with the natural slime or biological polymers produced by microorganisms in the MLSS. It is much more common than people realize. Like filamentous bulking, you need to indentify the cause and work to get the excess EPS out of the system by wasting. We are now having success monitoring for the organisms responsible of non-filamentous bulking using qPCR and increasing wasting rates before bulking is observable in the MLSS.
  
  
• Old Sludge (Low F/M) If the problem is "fines" or turbidity - you can look at "old sludge" which is very low F/M where microbes start to degrade the biopolymers holding floc together. Unless your influent organics concentration will soon increase, you should waste to maintain a proper F/M ratio. Once you are in the ideal F/M zone for your system, it should start to clear itself up.