Densified Sludge Selection System

Densified Sludge Selection System

　　The Densified (granular) sludge selection system continuously cultivates and screens the densified sludge with a larger specific gravity so as to optimize the microbial population, improve the sludge settleability, increase the microbial concentration in the reaction tank, and finally achieve the purpose of improving the effect of biological nitrogen and phosphorus removal, improving the effluent quality and enhancing the sewage treatment capacity.

　　The Densified (granular) sludge selection system mainly promotes the formation of aerobic granular sludge through process adjustment and sludge selector. Without adding new sewage treatment structures or equipment, the activated sludge is separated into two parts through physical method which is setting a sludge selector on the return activated sludge pipeline of the secondary sedimentation tank, and the selected activated sludge with large and dense portion is returned to the biochemical system for retention, while light and loose portion sludge (such as filamentous bacteria) is discharged to the sludge thickener and leave the activated sludge system. After selection, the specific gravity and settling rate of the sludge will increase, which can effectively improve the settleability of the sludge. Meanwhile, the densified sludge contains phosphate accumulating bacteria (PAOs), ammonia-oxidizing bacteria (AOB), nitrite-oxidizing bacteria (NOB), denitrifying heterotrophic bacteria and even anaerobic ammonia-oxidizing bacteria (Anammox), which will greatly enhance the ability of biological nitrogen and phosphorus removal.

Morphological changes of granular sludge

　　Main Advantages:

　　①Enhanced bio-phosphorus removal
  Without changing the existing treatment process, the relatively heavy PAOs are naturally screened out by the sludge selector thus the phosphorus accumulating bacteria dominate the anaerobic phosphorus release and aerobic phosphorus uptake, and finally improve the phosphorus removal efficiency.
  ②Improve the settling velocity SV30 and SVI
  Removing loose sludge such as flocculent sludge, free bacteria and filamentous bacteria, leaving heavy granular sludge with higher density to improve the activated sludge settling velocity.
  ③Reduce or cancel the dosing of chemicals
  The relatively heavy activated sludge is selected and left which will improve the settling performance of the sludge. The effluent TSS from the secondary clarifier becomes better, the dosage of flocculants and coagulants is greatly reduced, and the sludge properties are improved. In order to improve the efficiency of nitrogen and phosphorus removal, the dosage of carbon source is greatly reduced or even not added.
  ④Easy to be integrated into a wide variety of processes
  It is suitable for most activated sludge treatment processes such as oxidation ditch, A2/O, CASS, CAST, MSBR, etc.
  ⑤High return on investment
  No civil works, no complicated supporting equipment, only an external filter is added to improve the sludge settling, the ability to remove nitrogen and phosphorus, and the effluent SS.
  ⑥Operating stability
  Breaking the cycle of seasonal sludge bulking, the secondary clarifier and biochemical tank can better adapt to and withstand shock loads and hydraulic loads, and the operation stability of the sewage plant becomes better.