Understanding the dewaterability of aerobic granular sludge formed in continuous flow bioreactors treating real domestic wastewater: Is it really better than that of activated sludge?

Grey domestic wastewater from septic tank contains high nitrogen content and low C/N ratio. Therefore, the aerobic biological treatment is often not effective for ammonium and nitrogen removal. The aim of this work was to study the performance of nitrogen removal and production of aerobic granular sludge using biochar produced from coffee husk pyrolyzed at 350oC as biocarrier. It was performed under the lab-scale SBR systems. Low C/N ratio domestic wastewater was used for this work. Coffee husk biochar (CFH 350) was added into the systems at different dosage. As a result, the biochar made from coffee husk pyrolyzed at low temperature promoted the adhesion of sludge onto biochar surface. The particles size of biochar played an important role for adsorption and adhesion capacity of activated sludge on biochar. The growth rate of bacterial sludge was accelerated and higher than control sample when biochar was used with biochar dose of 15 g/L. Though nitrification rate was improved as the bacterial sludge was accelerated, however, at initial stage, the removal efficiency of COD and total nitrogen was not as high as compare to traditional activated aerobic sludge system.

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Performance of Aerobic Granular Sludge for Domestic Wastewater Treatment

International Journal of Innovative Technology and Exploring Engineering - Special Issue ◽

10.35940/ijitee.l3360.1081219 ◽

2019 ◽

Vol 8 (12) ◽

pp. 3851-3854

Keyword(s):

Wastewater Treatment ◽

Activated Sludge ◽

Batch Reactor ◽

Biomass Concentration ◽

Domestic Wastewater ◽

Granular Sludge ◽

Volume Index ◽

Aerobic Granular Sludge ◽

Domestic Wastewater Treatment ◽

Low Strength

Aerobic granular sludge can be used to treat various types of wastewater, such as industrial, municipal and domestic wastewater. This study investigated the treatment of low-strength domestic wastewater while simultaneously developed aerobic granular sludge in a sequencing batch reactor (SBR). Activated sludge was used as the seeding for granulation. The results indicated good COD and ammoniacal nitrogen removal at 72% and 73%, respectively. Aerobic granular sludge was successfully developed with low sludge volume index (SVI30) of 29 mL/g, which demonstrated an excellent settling property of aerobic granular sludge. Biomass concentration increased significantly compared to the seed sludge, indicating high biomass density in the SBR system. Settling velocity of aerobic granular sludge was significantly higher compared to the conventional activated sludge. This study showed the feasibility of aerobic granular sludge to be developed using low-strength domestic wastewater. Moreover, this study demonstrated the long-term application of aerobic granular sludge in domestic wastewater treatment.

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Anaerobic hydrolysis of complex substrates in full-scale aerobic granular sludge: enzymatic activity determined in different sludge fractions

Applied Microbiology and Biotechnology ◽

10.1007/s00253-021-11443-3 ◽

2021 ◽

Author(s):

Sara Toja Ortega ◽

Mario Pronk ◽

Merle K. de Kreuk

Keyword(s):

Hydrolytic Enzymes ◽

Oxygen Demand ◽

Domestic Wastewater ◽

Granular Sludge ◽

Hydrolytic Activity ◽

Full Scale ◽

Aerobic Granular Sludge ◽

Bulk Liquid ◽

Granule Formation ◽

Hydrolysis Of

Abstract Complex substrates, like proteins, carbohydrates, and lipids, are major components of domestic wastewater, and yet their degradation in biofilm-based wastewater treatment technologies, such as aerobic granular sludge (AGS), is not well understood. Hydrolysis is considered the rate-limiting step in the bioconversion of complex substrates, and as such, it will impact the utilization of a large wastewater COD (chemical oxygen demand) fraction by the biofilms or granules. To study the hydrolysis of complex substrates within these types of biomass, this paper investigates the anaerobic activity of major hydrolytic enzymes in the different sludge fractions of a full-scale AGS reactor. Chromogenic substrates were used under fully mixed anaerobic conditions to determine lipase, protease, α-glucosidase, and β-glucosidase activities in large granules (>1 mm in diameter), small granules (0.2–1 mm), flocculent sludge (0.045–0.2 mm), and bulk liquid. Furthermore, composition and hydrolytic activity of influent wastewater samples were determined. Our results showed an overcapacity of the sludge to hydrolyze wastewater soluble and colloidal polymeric substrates. The highest specific hydrolytic activity was associated with the flocculent sludge fraction (1.5–7.5 times that of large and smaller granules), in agreement with its large available surface area. However, the biomass in the full-scale reactor consisted of 84% large granules, making the large granules account for 55–68% of the total hydrolytic activity potential in the reactor. These observations shine a new light on the contribution of large granules to the conversion of polymeric COD and suggest that large granules can hydrolyze a significant amount of this influent fraction. The anaerobic removal of polymeric soluble and colloidal substrates could clarify the stable granule formation that is observed in full-scale installations, even when those are fed with complex wastewaters. Key points • Large and small granules contain >70% of the hydrolysis potential in an AGS reactor. • Flocculent sludge has high hydrolytic activity but constitutes <10% VS in AGS. • AGS has an overcapacity to hydrolyze complex substrates in domestic wastewater. Graphical abstract

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