Document Detail

Stratification and oxidation-reduction potential change in an aerobic and sulfate-reducing biofilm studied using microelectrodes.
MedLine Citation:
PMID:  11561597     Owner:  NLM     Status:  MEDLINE    
Recent studies in aerobic-nitrifying biofilms demonstrated the heterogeneity of biofilms used in wastewater treatment and led to modifications of the homogeneous assumptions in the conventional biofilm kinetic models. However, the stratification in aerobic-anaerobic biofilms has not been well investigated because of a lack of effective experimental tools. In this study a suite of microelectrodes, recently developed in the authors' laboratory, was used to examine the stratification of microbial processes and the change of oxidation-reduction potential (ORP) within an aerobic, sulfate-reducing biofilm. The microelectrodes have tip diameters of 3 to 20 microm and a high spatial resolution. They were used to measure the profiles of oxygen, total dissolved sulfide, ORP, and pH as a function of depth in the biofilm. The biofilm reactor was used to treat an azo-dye-containing wastewater with a chemical oxygen demand of 160 mg/L. The reactor bulk-phase dissolved oxygen concentration of the biofilm was 1.7 mg/L. The experimental results demonstrated that the microbial processes in the biofilm were stratified. In this biofilm, aerobic oxidation took place only in a shallow layer of 0.55 mm near the surface and sulfate reduction occurred in the deeper anoxic zone. The ORP changed with the shift of primary microbial process. The ORP was +362 mV at the biofilm surface and -166 mV near the substratum. Near the interface between the aerobic zone and the sulfate reduction zone, a surprisingly sharp decrease of ORP from a positive potential of +194 mV to a negative potential of -77 mV was observed. This occurred within a narrow band of 50 microm in depth. These new experimental findings support the concept of stratification of microbial processes and the associated ORP change in biofilms.
T Yu; P L Bishop
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Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  Water environment research : a research publication of the Water Environment Federation     Volume:  73     ISSN:  1061-4303     ISO Abbreviation:  Water Environ. Res.     Publication Date:    2001 May-Jun
Date Detail:
Created Date:  2001-09-19     Completed Date:  2001-10-25     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  9886167     Medline TA:  Water Environ Res     Country:  United States    
Other Details:
Languages:  eng     Pagination:  368-73     Citation Subset:  IM    
University of Cincinnati, USA.
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MeSH Terms
Azo Compounds / metabolism
Bacteria, Anaerobic / physiology*
Hydrogen-Ion Concentration
Population Dynamics
Sulfates / analysis,  chemistry*
Sulfides / analysis,  chemistry
Waste Disposal, Fluid*
Reg. No./Substance:
0/Azo Compounds; 0/Sulfates; 0/Sulfides

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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