All biological wastewater processes have a need for balanced sources of BOD, nitrogen, and phosphate. In aerobic processes, the correct ratio of BOD:N:P is critical for strong floc formation and good settling. A ratio of 100:7:1 works well in most aerobic processes, but his ratio can vary from 100:10:1 to 100:5:1, depending on what makes up the incoming BOD (municipal waste, cheese waste, sugary waste, etc).
100:7:1 The Ingredients for Ideal EPS
Bacteria flocculate by producing a glue that allows the cells to stick together. This glue is called EPS (exocellular polymeric substances), a matrix of proteins and polysaccharides that provide adhesion of the cells and protect the floc from toxicity. Nitrogen provides the key nutrient heterotrophic bacteria need in order to produce the protein component of EPS and the phosphate principally builds the carbohydrate (polysaccharide) portion of EPS. Together the proteins and the carbohydrates form a strong and tightly bound floc (as shown in the diagram).
When nitrogen levels are low, the tightly bound EPS will gradually become loosely bound and permeate into the mixed liquor. You’ll recognize this when the floc has a slimy or gelatinous consistency. This loosely bound EPS will cause sludge bulking and can give the MLSS a white, slimy feel.
When it is time to press solids with high EPS wastewater, plants run into other issues like:
- Poor polymer performance – floc and EPS are negatively charged, and the higher amount of EPS present, the more positively charged polymer will be required to bind the floc together
- EPS causes blinding of filter press
- Wastewater plants with nitrogen deficiencies generally produce more sludge
Prevent EPS Sliming and Poor Dewatering
Accelerator 7 is an organic nitrogen supplement that quickly combats the issues above by providing a source of nitrogen chosen for rapid uptake. The advantage behind Accelerator 7 is that its easily degradable nitrogen and vitamins are utilized exclusively by floc forming bacteria. No more wasted nitrogen that only gets consumed by nitrifiers (as commonly happens with urea and other chemical nitrogen supplements). Even better, Accelerator 7 is directly consumed by floc forming bacteria, without any additional steps required to achieve the nitrogen supplements benefit.