Joseph D. Rouse

Characterization of the microbial community in an anaerobic ammonium-oxidizing biofilm cultured on a nonwoven biomass carrier

The enrichment and characterization of anaerobic ammonium-oxidizing biofilm cultures are ongoing in our laboratories. Biomass, with a predominately red color, demonstrating simultaneous removal of ammonium and nitrite under autotrophic and anoxic conditions, which is characteristic of anaerobic ammonium-oxidizing planctomycetes, was enriched and maintained for an extended period on a polyester nonwoven carrier. To investigate the bacterial composition of the mature biofilm community, 16S rDNA sequences were amplified by PCR and comparative analyses using DNA databases were conducted. Only one sequence had a notable similarity (92.2%) to that of the first discovered anaerobic ammonium-oxidizing planctomycete and lesser, yet significant, similarities to the 16S rDNA sequences of other recently reported anaerobic ammonium-oxidizing strains. The newly discovered strain (designated KSU-1) reported here was dominant among detectable members of the biofilm community. By fluorescence imaging, KSU-1 was shown to form spherical clusters wrapped in a thin layer of Zoogloea sp. Possible interactions and interdependencies of these two species are discussed with regard to the putative unculturability of the anaerobic ammonium-oxidizing planctomycetes.

Characterization of denitrifying granular sludge treating soft groundwater in an upflow sludge-blanket reactor.

Nitrate removal from soft groundwater using ethanol as a carbon source in an upflow sludge-blanket reactor containing denitrifying granular sludge was investigated. At a hydraulic retention time of 0.83 h, influent nitrate was increased stepwise from 20 to 145 mg N/l (volumetric loading rates (VLRs), 0.60 to 4.2 g N/l/d, respectively) and sludge was periodically wasted to maintain a sludge bed of about 2 3 the liquid volume. Complete nitrate removal was achieved at influent nitrate concentrations up to 75 mg N/l(2.1 g N/l/d). MLSS increased from 20 g/l at a VLR of 0.6 g N/l/d to 51 g/l at a VLR of 1.9 g N/l/d, above which it decreased. VSS increased from 11 g/l to a maximum of 25 g/l at a VLR of 2.1 g N/l/d. Settling velocities showed the same trend with maximum values in a VLR range of 1.5 to 2.1 g N/l/d. However, granule size, calcium and magnesium contents of the granular sludge and protein, carbohydrate and nucleic acid contents of extracellular polymers decreased steadily with an increase in VLR throughout the range of testing. Within the VLR range of 0.6 to 2.1 g N/l/d, corresponding to complete nitrate removal and efficient sludge retention, the granular sludge had a high calcium content of 24 to 22%, magnesium ranged from only 0.7 to 0.1%, proteins from 3.2 to 1.3%, carbohydrates from 4.2 to 1.4%, and nucleic acids from 0.34 to 0.05% of the sludge dry weight. These results suggest an optimum operational VLR in terms of nitrate removal and sludge retention of about 2 g N/l/d.

Trace elements enhance biofilm formation in UASB reactor for solo simple molecule wastewater treatment.

In this paper, trace elements (TE) adding was investigated in one bench-scale UASB reactor treating solo simple molecule wastewater with the aim of evaluating its effect on enhancing biofilm formation. After adding sufficient TE (3 mL/L) in the influent, during 3 days, COD removal efficiency increased from 74% to 90% comparing to no adding TE. Over 55 days of operation, the organic loading rate (OLR) reached 11 g/L/day with COD removal efficiencies greater than 90%. While in the steady running period no effect even improvement on treatment performance was observed without any TE adding. The results illuminated that TE accounted for quick start-up of the UASB biofilm system rather than ever known biocatalyst.