Immobilization of metal–humic acid complexes in anaerobic granular sludge for their application as solid-phase redox mediators in the biotransformation of iopromide in UASB reactors

In this work, granules developed from UASB reactors that treat different types of wastewaters (ethanol, carbohydrates and protein-based synthetic wastewaters) were studied. Granule parameters (size distribution; density; settlement characteristics; elemental composition; acidogenic and methanogenic activities) were analyzed along with micro-organisms identified by FISH to better understand granule behavior and its formation process. Micro-organisms distributions in anaerobic granules are highly dependent on the type of treated wastewater. Granules developed in a UASB reactor that treats wastewater with a high content of carbohydrates presented high acidogenic bacteria colonization. Members of Methanosaetaceae were the dominant methanogens in the studied granules, and Methanobacteriales appear to be co-dominant in the granules developed with carbohydrates and protein-based wastewaters.

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Toxicity of Sulfite and Cadmium to Anaerobic Granular Sludge

Water Quality Research Journal ◽

10.2166/wqrj.1994.037 ◽

1994 ◽

Vol 29 (4) ◽

pp. 581-598

Author(s):

C.F. Shew ◽

N. Kosaric

Keyword(s):

Granular Sludge ◽

Upflow Anaerobic Sludge Blanket ◽

Shock Load ◽

Anaerobic Sludge ◽

Anaerobic Granular Sludge ◽

Scanning Electron Micrographs ◽

Bacterial Growth Rate ◽

Digestion Rate ◽

Sulfate Reducing ◽

Load Conditions

Abstract Toxicity of sulfite (Na2SO3) and cadmium (CdCl2) ions to anaerobic granular sludge was investigated in 1.2 litre bench-scale upflow anaerobic sludge blanket (UASB) reactors during process acclimation and shock load conditions. Minimal sulfite toxicity was observed under gradual and shock load conditions at sulfite concentrations of up to 1000 mg S/L if proper acclimation was allowed to occur. No long-term toxic effects were observed although the COD digestion rate was temporarily inhibited by shock load of sulfite. Scanning electron micrographs indicated that more sulfate-reducing bacteria were present in the granules developed in the reactors with sulfite supplement although rod-shaped Methanosaeta-like bacteria were still dominant. High bacterial growth rate was observed in the reactors which were supplied with the feed containing sulfite. The COD digestion rate was inhibited at a cadmium loading rate of 2.4 g Cd per day under both acclimation and shock load conditions. Acclimation did not seem to improve the bacteria to tolerate the toxicity of cadmium. The concentration of free cadmium was very low in the reactors under normal conditions, but increased rapidly when the COD digestion in the reactors ceased. The bacteria could not be reactivated after inhibited by cadmium. When reactors were operated at low specific COD loading rates, more inorganic precipitates were formed inside the granules which consequently settled faster.

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The effect of extreme temperatures (70–80°C) on the effluent quality and sludge characteristics of UASB reactors

Water Science & Technology ◽

10.2166/wst.1997.0607 ◽

1997 ◽

Vol 36 (6-7) ◽

pp. 325-332 ◽

Cited By ~ 2

Author(s):

Raghida Lepistö ◽

Jukka Rintala

Keyword(s):

Volatile Fatty Acids ◽

Granular Sludge ◽

Anaerobic Sludge ◽

Methanogenic Activity ◽

Sludge Characteristics ◽

Effluent Quality ◽

Start Up ◽

Thermomechanical Pulping ◽

Increasing Temperature ◽

Uasb Reactors

The study focused on the effluent quality and sludge characteristics during the start-up and operation of extreme thermophilic (70 to 80°C) upflow anaerobic sludge bed (UASB) reactors, inoculated with mesophilic and thermophilic granular sludge and fed with acetate, volatile fatty acids (VFA), and thermomechanical pulping (TMP) whitewater. Low effluent quality and long start-up periods were observed during the start-up of the 70 to 76°C, VFA-fed UASB reactors inoculated with mesophilic granulae, while better effluent quality and considerably shorter start-up periods were observed when thermophilic (55/70°C) inocula were used. With VFA feed, a significant amount of acetate was removed at 70°C and even at 80°C, while propionate removal was negligible. With TMP whitewater feed, low VFA effluent concentration was obtained at 70°C. The volatile solids (VS) and the VS/total solids (TS) content of the sludge decreased significantly during the first 2–3 months of operation when mesophilic inocula were used. The initial specific methanogenic activity (ISMA) of the extreme thermophilic sludge decreased with increasing temperature and was slightly higher on glucose than on acetate. At 70 to 80°C, various rod-like bacteria were dispersed through the granulae in either individual or in low density micro colonies surrounded with a varying degree of precipitates.

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