A Novel bioreaktor for High Density Dyrkning af Diverse mikrobielle samfund
Summary
A novel reactor design, coined a high density bioreactor (HDBR), is presented for the cultivation and study of high density microbial communities. Here, the HDBR is successfully applied in a photobioreactor (PBR) configuration for the study of nitrogen metabolism by a mixed high density algal community.
Abstract
A novel reactor design, coined a high density bioreactor (HDBR), is presented for the cultivation and study of high density microbial communities. Past studies have evaluated the performance of the reactor for the removal of COD1 and nitrogen species2-4 by heterotrophic and chemoautotrophic bacteria, respectively. The HDBR design eliminates the requirement for external flocculation/sedimentation processes while still yielding effluent containing low suspended solids. In this study, the HDBR is applied as a photobioreactor (PBR) in order to characterize the nitrogen removal characteristics of an algae-based photosynthetic microbial community. As previously reported for this HDBR design, a stable biomass zone was established with a clear delineation between the biologically active portion of the reactor and the recycling reactor fluid, which resulted in a low suspended solid effluent. The algal community in the HDBR was observed to remove 18.4% of total nitrogen species in the influent. Varying NH4+ and NO3– concentrations in the feed did not have an effect on NH4+ removal (n=44, p=0.993 and n=44, p=0.610 respectively) while NH4+ feed concentration was found to be negatively related with NO3– removal (n=44, p=0.000) and NO3– feed concentration was found to be positively correlated with NO3– removal (n=44, p=0.000). Consistent removal of NH4+, combined with the accumulation of oxidized nitrogen species at high NH4+ fluxes indicates the presence of ammonia- and nitrite-oxidizing bacteria within the microbial community.
Introduction
Kommunalt spildevand er almindeligt behandles med aktiverede slam processer for at reducere de suspenderede faste stoffer (SS), biologisk iltforbrug (BOD), organisk og uorganisk kvælstof, og fosfor indhold 5,6. Det aktiverede slam proces, et middel til sekundær spildevandsrensning, indebærer oxidation af organisk kulstof i en beluftningstank fyldt med en blandet væske af indkommende spildevand og genbrugt heterotrofe mikroorganismer (almindeligvis benævnt aktiveret slam) 5-7. Den blandede væske derefter ind i en forholdsvis stor klaringstank (bundfældningstank), hvor slammet afregner for nemmere samling, enten bortskaffes eller recirkuleres tilbage til luftningstanken, mens den klarede, renset spildevand kan fortsætte til tertiær behandling eller desinficering, før de frigives til der modtager vand 5-7. Effektiv separation af det behandlede spildevand og faste stoffer (slam) i den sekundære klaringstank er afgørende for den korrekte funktion af en vartewater behandlingssystem, som enhver aktiveret slam fortsætter ud klaringstankene vil øge BOD og SS i spildevandet 5-8.
En række alternative biologiske processer findes for sekundær rensning af spildevand, som reducerer eller eliminerer behovet for store præciserer tanke, herunder fæstnet-vækst (biofilm) reaktorer, membranbioreaktorer (MBRs), og granulerede slam reaktorer. I biofilm reaktorer, dannelsen af biofilm, hvor mikroorganismer naturligt aggregat og vedhæfte som et lag på en fast overflade, giver mulighed for opbevaring og akkumulering af biomasse uden behov for en afklaring tank. Biofilm reaktorer kan inddeles i tre typer: pakket leje, reaktorer med fluid bed-reaktorer og roterende biologiske kontaktorer. Pakket bed-reaktorer, såsom en rislende filtre og biologiske tårne, udnytte en stationær solid vækst overflade 5,6. Fluid bed-reaktorer (FBRs) afhænger af fastgørelsen af mikroorganismer til partikler,såsom sand, granuleret aktivt kul (GAC), eller glasperler, som holdes i suspension ved en høj opadgående strømningshastighed 9,10. Roterende biologiske reaktorer afhænger biofilm dannet på medier knyttet til en roterende aksel tillader biofilmen skal skiftevis udsættes for luft, og væsken bliver behandlet 5,6. MBRs bruger membran filtreringsenheder, enten inden bioreaktoren (nedsænket konfiguration) eller eksternt via recirkulation (side-stream konfiguration) 5,11. Membranerne anvendes til at opnå en god separation af biomasse og faste partikler fra den behandlede væske 11,12. Granulære slam reaktorer er opstrøms- reaktorer, hvor dannelsen af ekstremt tætte og godt bosætter granulat af mikroorganismer opstår, når de udsættes for høje overfladiske luft opstrøms hastigheder 13.
Som et andet alternativ til fremgangsmåden med aktiveret slam, en hidtil ukendt opstrøms reaktor systemet, nu kaldet en høj densitet bioreaktor (HDBR), var designed og bygget af Salg og Shieh (2006) til at studere COD fjernelse af aktiveret slam fra syntetiske affaldsstrømme i lav F / M forhold, der er kendt for at forårsage dannelse af dårlig afregning slam (dvs. bulking slam) 1,7,14. Den HDBR systemet udnyttes modificeret fluid bed-reaktorer, der typisk består af en opstrøms reaktor og en ekstern -recirkuleringstank. Fluid bed-reaktorer drives typisk med recirkulationsstrømmen strømningshastigheder høj nok til at holde biofilmvækst undergrunden suspenderet, men lav nok til, at biofilmen-dækket substrat bibeholdes. I modsætning til fluid bed-reaktorer, i HDBR beskrevet i salgs- og Shieh (2006), der anvendes relativt lave recirkulationsstrøm strømningshastigheder, som sammen med ekstern beluftning, forhindrede forstyrrelse af biomassen zone dannet inde i reaktoren 1. Efterfølgende undersøgelser har vist denne reaktor design evne til at behandle en række kvælstof strømme ved hjælp af nitrificerende / denitrificerende bakterier 3,4. I al studIES dannelsen af et stabilt, tæt biomasse zone inden for HDBR fjernet behovet for en ekstern flokkulering / sedimentering proces 1-4.
Som vi rapporterer her, er brugen af HDBR at vokse tætte kulturer også blevet testet i en fotobioreaktor (PBR) konfiguration til dyrkning af alger. Vi diskutere fordele og ulemper ved denne roman reaktorsystem for alge dyrkning og dens potentiale for at overvinde en stor hurdle i kommercialiseringen af alger biobrændstoffer i forbindelse med biomasse høst (dvs. god fast-væske separation 15,16). Følgende protokol beskriver de nødvendige skridt for at samle, opstart, prøve fra, og opretholde en HDBR med alger som det mikrobielle samfund af interesse. Variationer i opstart og drift protokol heterotrofe og nitrificerende / denitrificerende kulturer vil også blive nævnt. Endelig vil generelle fordele, ulemper og ukendte i denne roman reaktor design fremhæves.
Protocol
Representative Results
Discussion
Dette afsnit vil starte med en diskussion af protokol variationer er nødvendige for at behandle eventuelle operationelle spørgsmål samt bruge forskellige mikrobielle samfund. Styrkerne i denne reaktor design vil blive diskuteret, herunder evnen til at styre kontrollen med oxygen flux og dannelsen af høj densitet fnug inden i reaktoren. Aktuelle udfordringer og mulige veje af undersøgelsen vil også blive nævnt.
Protokol nuancer og variationer
Driften af HDBR…
Disclosures
The authors have nothing to disclose.
Acknowledgements
The authors would like to acknowledge Aspen Walker at the University of Pennsylvania for her assistance in reactor maintenance and sample collection.
Materials
| Aeration stone | Alita | AS-3015C | |
| Aerator | Top Fin | Air-1000 | |
| Ammonium chloride | Sigma Aldrich | A9434 | |
| Anion analysis column | Shodex | IC SI-52 4E | |
| Beaker (600 mL) | Corning Pyrex | 1000-600 | Used as mixing vessel (MV). Addition of hose barbs at the bottom and 500 mL levels. Outside diameter of hose barbs 3/8". |
| Calcium chloride | Sigma Aldrich | C5670 | |
| Cation analysis column | Shodex | IC YS-50 | |
| Cobalt chloride hexahydrate | Sigma Aldrich | C8661 | |
| Copper chloride | Sigma Aldrich | 222011 | |
| Ferric chloride | Sigma Aldrich | 157740 | |
| Filter (vacuum) | Fisherbrand | 09-719-2E | 0.45 um membrane filter, MCE, 47 mm diameter |
| Graduated cylinder (1000 mL) | Corning Pyrex | 3025-1L | Used as reactor vessel (R). Addition of hose barbs at bottom, 500 mL, and 1 L levels. Outside diameter of hose barbs 3/8". |
| HPLC/IC | Shimadzu | Prominence | |
| Magnesium sulfate | Sigma Aldrich | M2643 | |
| Masterflex L/S variable speed drive | Masterflex | 07553-50 | Drive for recycle and feed pumps (2 needed) |
| Nickel chloride hexahydrate | Sigma Aldrich | N6136 | |
| Potassium nitrate | Sigma Aldrich | P8291 | |
| (Monobasic) Potassium phosphate | Sigma Aldrich | P5655 | |
| Pump head | Masterflex | 07018-20 | Recycle pump head |
| Pump head | Masterflex | 07013-20 | Feed pump head |
| Pump tubing | Masterflex | 6404-18 | Recycle pump tubing |
| Pump tubing | Masterflex | 6404-13 | Feed pump tubing |
| Sodium bicarbonate | Sigma Aldrich | S5761 | |
| Zinc sulfate heptahydrate | Sigma Aldrich | Z0251 |
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