Full-scale Upflow Anaerobic Sludge Blanket Research Articles

Characterization of the sulfate-reducing and syntrophic population in granular sludge from a full-scale anaerobic reactor treating papermill wastewater

To gain more insight into the competitive and syntrophic interactions between sulfate-reducing and methanogenic consortia in sulfate-limited anaerobic reactors, the microbial population in granular sludge from a full-scale upflow anaerobic sludge blanket (UASB) reactor was studied, using the 16S rRNA dot-blot hybridization method in combination with most probable number estimates. The wastewater which was treated in the UASB reactor contained mainly starch, acetate, propionate, butyrate and formate, and had a chemical oxygen demand/sulfate ratio of 9.5. Evidence was obtained that acetate was mainly degraded by Methanosaeta-like microorganisms, while propionate was the preferred substrate for sulfate reduction. The Desulfobulbus-like propionate-degrading sulfate reducers in the sludge competed with Syntrophobacter-like bacteria for the available propionate. Hydrogen and formate were probably mainly degraded via methanogenesis by members of the order Methanobacteriales. Hydrogen, formate and butyrate-degrading sulfate reducers could not be characterized with the 16S rRNA probes available to date. The same was true for syntrophic butyrate degraders.

Characterization of the sulfate-reducing and syntrophic population in granular sludge from a full-scale anaerobic reactor treating papermill wastewater

To gain more insight into the competitive and syntrophic interactions between sulfate-reducing and methanogenic consortia in sulfate-limited anaerobic reactors, the microbial population in granular sludge from a full-scale upflow anaerobic sludge blanket (UASB) reactor was studied, using the 16S rRNA dot-blot hybridization method in combination with most probable number estimates. The wastewater which was treated in the UASB reactor contained mainly starch, acetate, propionate, butyrate and formate, and had a chemical oxygen demand/sulfate ratio of 9.5. Evidence was obtained that acetate was mainly degraded by Methanosaeta-like microorganisms, while propionate was the preferred substrate for sulfate reduction. The Desulfobulbus-like propionate-degrading sulfate reducers in the sludge competed with Syntrophobacter-like bacteria for the available propionate. Hydrogen and formate were probably mainly degraded via methanogenesis by members of the order Methanobacteriales. Hydrogen, formate and butyrate-degrading sulfate reducers could not be characterized with the 16S rRNA probes available to date. The same was true for syntrophic butyrate degraders.

Microbial diversity in UASB reactors

Abstract

Image analysis to quantify and measure UASB digester granules

Two-dimensional image analysis was applied to counting, sizing, and density determinations of granules in full-scale and laboratory-scale upflow anaerobic sludge blanket (UASB) digesters. An advantage of this technique for monitoring laboratory-scale digester sludge is the small amount of material required for analysis. Quantification of number of granules using this method correlated well with dry weight determinations (r = 0.989). Distinguished granule size increased with time throughout the digestion process, supported by dry weight determinations which indicated an increase in biomass. The monitoring of granule density may reveal subtleties of the selection pressure placed on granules not noticed previously.

The Application of a Full-Scale UASB Plant for the Treatment of Coffee Waste

The suitability of anaerobic digestion for the treatment of a coffee waste has been demonstrated in a full-scale UASB (Upflow Anaerobic Sludge Blanket) plant. The full-scale plant was designed after successful pilot-scale studies (19 m3 reactor) and was commissioned in September 1988. The design was based on a maximum flow of 2000 m3/day, COD concentration of 4000 mg/l, BOD load 3000 kg/day, suspended solids 1500 mg/l and total sulphur 50 mg/l. The temperature of the wastewater was between 28-30 °C. The required final effluent consent conditions for discharge into the local sewer were 700 kg BOD/day, 3000 mg/l COD, 600 mg/l suspended solids and 1 mg/l of hydrogen sulphide. The treatment plant comprised a primary settlement tank, a pre-acidification tank, a UASB reactor and a submerged aerated filter. The first three units were installed so as to obtain the consent conditions in terms of COD, BOD and suspended solids. The submerged aerated filter was constructed in order to meet the hydrogen sulphide consent. Close monitoring of the plant over a period of about 4 months demonstrated the potential of UASB reactors for the pre-treatment of this wastewater, as well as similar wastes from the food industry. A properly designed ventilation system, and de-odourization with compost filters, eliminated all odours emanating from the plant, demonstrating that anaerobic reactors can be safely installed in densely inhabited areas without causing any environmental nuisance.

Anaerobic-Aerobic Treatment of Municipal Wastewaters with Full-Scale Upflow Anaerobic Sludge Blanket and Attached Biofilm Reactors

The results of pilot experiments on municipal wastewater treatment using advanced processes are described. The most important aims of this research were to achieve reductions in energy consumption, environmental impact, quantity of stabilized sludge produced, and area necessary for plant construction. The pilot plant, which was constructed in the environs of the Senigallia (AN, Italy) municipal wastewater treatment plant, had a capacity of 500 to 2500 population equivalents (p.e.). In the most attractive system, municipal wastewaters with a low organic concentration were first treated in an upflow anaerobic sludge blanket (UASB) bioreactor with a capacity of 336 m3. Part of the effluent from this process was then conveyed to an anoxic biological fluidized bed (with a volume of 8 m3 filled with 3 m3 of quartzite sand) for pre-denitrification, and then to an aerobic fixed bed (with random plastic media and a volume of 8m3) for nitrification. It was also possible to treat the municipal wastewaters using the anaerobic fluidized bed directly, after microscreening or primary sedimentation. The research undertaken was intended to verify the reliability of these processes at ambient temperatures and with variable wastewater concentrations. The preliminary results obtained for COD, BOD, and N removal from municipal wastewaters indicate that this system is quite an attractive treatment alternative, mainly due to its low sludge production and energy consumption. These results will enable accurate design criteria to be identified for the construction of more economic treatment plants on a larger scale.