The best and appropriate way of formation of granules and the process should be speedy as well i.e. not time consuming?
Dear Muhammad,
To form granules using sequential batch reactor ,the systems should fulfill most of the following requirements:
Feast - Famine regime: short feeding periods must be selected to create feast and famine periods, characterized by the presence or absence of organic matter in the liquid media, respectively. With this feeding strategy the selection of the appropriate microorganisms to form granules is achieved. When the substrate concentration in the bulk liquid is high, the granule-former organisms can store the organic matter in form of poly-β-hydroxybutyrate to be consumed in the famine period, giving an advantage over filamentous organisms. When an anaerobic feeding is applied this factor is enhanced, minimizing the importance of short settling time and higher hydrodynamic forces.
Short settling time: This hydraulic selection pressure on the microbial community allows the retention granular biomass inside the reactor while flocculent biomass is washed-out.
Hydrodynamic shear force : Evidences show that the application of high shear forces favors the formation of aerobic granules and the physical granule integrity. It was found that aerobic granules could be formed only above a threshold shear force value in terms of superficial up flow air velocity above 1.2 cm/s in a column SBR, and more regular, rounder, and more compact aerobic granules were developed at high hydrodynamic shear forces.
Granular activated sludge is also developed in flow-through reactors using the Hybrid Activated Sludge (HYBACS®) process, comprising an attached-growth reactor with short retention time upstream of a suspended growth reactor. The attached bacteria in the first reactor, known as a SMART unit, are exposed to a constant high COD, triggering the expression of high concentrations of hydrolytic enzymes in the EPS layer around the bacteria. The accelerated hydrolysis liberates soluble readily-degradable COD which promotes the formation of granular activated sludge.
References:
Beun J.J., Hendriks A., Van Loosdrecht M.C.M., Morgenroth E., Wilderer P.A. and Heijnen J.J. (1999). Aerobic granulation in a sequencing batch reactor. Water Research, Vol. 33, No. 10, pp. 2283–2290.
Qin L. Liu Y. and Tay J-H (2004). Effect of settling time on aerobic granulation in sequencing batch reactor. Biochemical Engineering Journal, Vol. 21, No. 1, pp. 47–52.
Tay J.-H., Liu Q.-S. and Liu Y. (2001). The effects of shear force on the formation, structure and metabolism of aerobic granules. Applied Microbiology and Biotechnology, Vol. 57, Nos. 1–2, pp. 227–233.
Hoping this will be helpful,
Rafik
Dear Muhammad,
In addition to the factors perfectly explained by Rafik Karaman, you can reduce the time needed for the start up of the reactor by seeding the reactor with already formed granules.
In addition to SBR, aerobic granular biomass was also formed in continuos reactors.
The NEREDA process is already applied at full scale.
Best regards,
Nico
https://www.google.es/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0ahUKEwjTutbqpvfLAhVBfxoKHWjjAqoQFgglMAA&url=http%3A%2F%2Fwww.hach.com%2Fasset-get.download.jsa%3Fid%3D42334289201&usg=AFQjCNFU2SSJ4aCl-pTSx8jjY4qkRz094w&sig2=qV_9cFPIkjoyA6AfR6EdPw&cad=rja
http://www.sciencedirect.com/science/article/pii/S1001074209602564
Article Aerobic granular-type biomass development in a continuous st...
Hello
dear Muhammad Ali
I recommend you just follow the procedure that are sync with your goals, i.e if you will work at aerobic condition follow same articles (Same advice for anaerobic biogranulation).
For example you can make synthetic medium in order to form anaerobic granules in a long column (High H/D) with a cyclic mode. After about one week it will be formed.
Good luck
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