{"id":{"repo_id":"vt","oai_identifier":"oai:vtechworks.lib.vt.edu:10919/28883"},"canonical_url":"https://search.dev.ndltd.org/etd/vt/oai:vtechworks.lib.vt.edu:10919/28883","repository":{"repo_id":"vt","name":"Virginia Tech","base_url":"https://vtechworks.lib.vt.edu/oai/request"},"display":{"title":"The Kinetics, Biochemical Patterns, and Microbial Ecology in Multiredox (Anoxic, Microaerobic, Aerobic) Activated Sludge Systems Treating BTX Containing Wastewater","abstract":"BTX biodegradation rates, biochemical expression patterns and microbial ecology were studied under anoxic (denitrifying), anoxic/microaerobic/aerobic, and anoxic/microaerobic conditions in activated sludge sequencing batch reactors. The studies showed that toluene and m-xylene were denitrified via benzoyl-CoA reductase. Although benzene, o-, and p-xylene were recalcitrant under denitrifying conditions, they were biodegraded under microaerobic (< 0.2 mg/L dissolved oxygen) and nitrate or nitrite (NOx)-supplemented microaerobic conditions. The patterns of the specific enzymes associated with BTX biodegradation under microaerobic conditions indicated that the three compounds were metabolized by oxygen-dependent pathways. The expression levels of catechol 1, 2-dioxygenase and catechol 2, 3-dioxygenase under microaerobic conditions were induced to levels as high as under aerobic conditions (> 4 mg/L dissolved oxygen). Benzene, o-, and p-xylene biodegradation rates were twice as fast under NO<sub>x</sub>-supplemented compared to NO<sub>x</sub>-free microaerobic conditions, and the specific biodegradation rates under aerobic and NO<sub>x</sub>-supplemented microaerobic conditions were comparable. 16S rRNA probes targeting representative toluene-degraders were used to investigate the microbial communities in the three sequencing batch reactors by using a dot blot hybridization technique. The hybridization results suggest that multiple redox environments fostered a more diverse microbial community and the activities of the target organisms in the reactors with multiple redox environments were higher than in the single redox reactor. Additionally, facultative toluene-degraders appeared to play a less significant role than the strict anoxic and aerobic toluene-degraders in all three SBRs.","abstract_html":"BTX biodegradation rates, biochemical expression patterns and microbial ecology were studied under anoxic (denitrifying), anoxic/microaerobic/aerobic, and anoxic/microaerobic conditions in activated sludge sequencing batch reactors. The studies showed that toluene and m-xylene were denitrified via benzoyl-CoA reductase. Although benzene, o-, and p-xylene were recalcitrant under denitrifying conditions, they were biodegraded under microaerobic (&lt; 0.2 mg/L dissolved oxygen) and nitrate or nitrite (NOx)-supplemented microaerobic conditions. The patterns of the specific enzymes associated with BTX biodegradation under microaerobic conditions indicated that the three compounds were metabolized by oxygen-dependent pathways. The expression levels of catechol 1, 2-dioxygenase and catechol 2, 3-dioxygenase under microaerobic conditions were induced to levels as high as under aerobic conditions (&gt; 4 mg/L dissolved oxygen). Benzene, o-, and p-xylene biodegradation rates were twice as fast under NO&lt;sub&gt;x&lt;/sub&gt;-supplemented compared to NO&lt;sub&gt;x&lt;/sub&gt;-free microaerobic conditions, and the specific biodegradation rates under aerobic and NO&lt;sub&gt;x&lt;/sub&gt;-supplemented microaerobic conditions were comparable. 16S rRNA probes targeting representative toluene-degraders were used to investigate the microbial communities in the three sequencing batch reactors by using a dot blot hybridization technique. The hybridization results suggest that multiple redox environments fostered a more diverse microbial community and the activities of the target organisms in the reactors with multiple redox environments were higher than in the single redox reactor. Additionally, facultative toluene-degraders appeared to play a less significant role than the strict anoxic and aerobic toluene-degraders in all three SBRs.","abstract_has_math":false,"creators":["Ma, Guihua"],"institution":"Virginia Tech","degree_name":"Ph. D.","degree_level":"doctoral","degree_discipline":"Civil Engineering","degree_department":"Civil Engineering","school":null,"contributors":[],"advisors":[],"committee_chairs":["Love, Nancy G."],"committee_members":["Novak, John T.","Dietrich, Andrea M.","Stevens, Ann M.","Terlesky, Kathy C.","Benoit, Robert E."],"year":1999,"date_issued":"1999-09-02","date_published":"1999-09-02","updated_at":"2026-07-22T22:20:25Z","subjects":["16S rRNA","BTX","microbial activity","anoxic","enzymes","dot blot hybridization","standard blots","energy balance","redox","aerobic","microaerobic","probe"],"languages":[],"rights":["In Copyright"],"rights_urls":["http://rightsstatements.org/vocab/InC/1.0/"],"identifier_entries":[{"key":"dc:identifier.other","label":"Dc Identifier Other","values":["etd-090699-164851"],"render_values":[{"text":"etd-090699-164851","href":null,"code":true}]}]},"links":{"outbound_url":"http://hdl.handle.net/10919/28883","outbound_label":"Handle","outbound_source":"dc:identifier.uri"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor.committeechair","label":"Committee Chair","values":["Love, Nancy G."]},{"key":"dc:contributor.committeemember","label":"Committee Member","values":["Novak, John T.","Dietrich, Andrea M.","Stevens, Ann M.","Terlesky, Kathy C.","Benoit, Robert E."]},{"key":"dc:contributor.department","label":"Department","values":["Civil Engineering"]},{"key":"dc:creator","label":"Author","values":["Ma, Guihua"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.accessioned","label":"Dc Date Accessioned","values":["2014-03-14T20:15:58Z"]},{"key":"dc:date.available","label":"Dc Date Available","values":["2014-03-14T20:15:58Z","2000-09-08"]},{"key":"dc:date.issued","label":"Date","values":["1999-09-02"]},{"key":"dc:publisher","label":"Institution","values":["Virginia Tech"]},{"key":"dc:type","label":"Dc Type","values":["Dissertation"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Civil Engineering"]},{"key":"thesis:degree_level","label":"Degree Level","values":["doctoral"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Ph. 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The studies showed that toluene and m-xylene were denitrified via benzoyl-CoA reductase. Although benzene, o-, and p-xylene were recalcitrant under denitrifying conditions, they were biodegraded under microaerobic (< 0.2 mg/L dissolved oxygen) and nitrate or nitrite (NOx)-supplemented microaerobic conditions. The patterns of the specific enzymes associated with BTX biodegradation under microaerobic conditions indicated that the three compounds were metabolized by oxygen-dependent pathways. The expression levels of catechol 1, 2-dioxygenase and catechol 2, 3-dioxygenase under microaerobic conditions were induced to levels as high as under aerobic conditions (> 4 mg/L dissolved oxygen). Benzene, o-, and p-xylene biodegradation rates were twice as fast under NO<sub>x</sub>-supplemented compared to NO<sub>x</sub>-free microaerobic conditions, and the specific biodegradation rates under aerobic and NO<sub>x</sub>-supplemented microaerobic conditions were comparable. 16S rRNA probes targeting representative toluene-degraders were used to investigate the microbial communities in the three sequencing batch reactors by using a dot blot hybridization technique. The hybridization results suggest that multiple redox environments fostered a more diverse microbial community and the activities of the target organisms in the reactors with multiple redox environments were higher than in the single redox reactor. Additionally, facultative toluene-degraders appeared to play a less significant role than the strict anoxic and aerobic toluene-degraders in all three SBRs."]},{"key":"dc:description.degree","label":"Dc Description Degree","values":["Ph. D."]},{"key":"dc:title","label":"Title","values":["The Kinetics, Biochemical Patterns, and Microbial Ecology in Multiredox (Anoxic, Microaerobic, Aerobic) Activated Sludge Systems Treating BTX Containing Wastewater"]}]}],"canonical_facts":{"dc:contributor.committeechair":["Love, Nancy G."],"dc:contributor.committeemember":["Novak, John T.","Dietrich, Andrea M.","Stevens, Ann M.","Terlesky, Kathy C.","Benoit, Robert E."],"dc:contributor.department":["Civil Engineering"],"dc:creator":["Ma, Guihua"],"dc:date.accessioned":["2014-03-14T20:15:58Z"],"dc:date.available":["2014-03-14T20:15:58Z","2000-09-08"],"dc:date.issued":["1999-09-02"],"dc:description.abstract":["BTX biodegradation rates, biochemical expression patterns and microbial ecology were studied under anoxic (denitrifying), anoxic/microaerobic/aerobic, and anoxic/microaerobic conditions in activated sludge sequencing batch reactors. The studies showed that toluene and m-xylene were denitrified via benzoyl-CoA reductase. Although benzene, o-, and p-xylene were recalcitrant under denitrifying conditions, they were biodegraded under microaerobic (< 0.2 mg/L dissolved oxygen) and nitrate or nitrite (NOx)-supplemented microaerobic conditions. The patterns of the specific enzymes associated with BTX biodegradation under microaerobic conditions indicated that the three compounds were metabolized by oxygen-dependent pathways. The expression levels of catechol 1, 2-dioxygenase and catechol 2, 3-dioxygenase under microaerobic conditions were induced to levels as high as under aerobic conditions (> 4 mg/L dissolved oxygen). Benzene, o-, and p-xylene biodegradation rates were twice as fast under NO<sub>x</sub>-supplemented compared to NO<sub>x</sub>-free microaerobic conditions, and the specific biodegradation rates under aerobic and NO<sub>x</sub>-supplemented microaerobic conditions were comparable. 16S rRNA probes targeting representative toluene-degraders were used to investigate the microbial communities in the three sequencing batch reactors by using a dot blot hybridization technique. The hybridization results suggest that multiple redox environments fostered a more diverse microbial community and the activities of the target organisms in the reactors with multiple redox environments were higher than in the single redox reactor. Additionally, facultative toluene-degraders appeared to play a less significant role than the strict anoxic and aerobic toluene-degraders in all three SBRs."],"dc:description.degree":["Ph. D."],"dc:identifier.other":["etd-090699-164851"],"dc:identifier.uri":["http://hdl.handle.net/10919/28883"],"dc:publisher":["Virginia Tech"],"dc:rights":["In Copyright"],"dc:rights.uri":["http://rightsstatements.org/vocab/InC/1.0/"],"dc:subject":["16S rRNA","BTX","microbial activity","anoxic","enzymes","dot blot hybridization","standard blots","energy balance","redox","aerobic","microaerobic","probe"],"dc:title":["The Kinetics, Biochemical Patterns, and Microbial Ecology in Multiredox (Anoxic, Microaerobic, Aerobic) Activated Sludge Systems Treating BTX Containing Wastewater"],"dc:type":["Dissertation"],"thesis:degree_discipline":["Civil Engineering"],"thesis:degree_level":["doctoral"],"thesis:degree_name":["Ph. D."],"thesis:institution_name":["Virginia Polytechnic Institute and State University"]},"updated_at":"2026-07-22T22:20:25Z"}