Unformatted text preview: ANAEROBIC AND AEROBIC REMEDIATION A. Hypothe5cal example ‐ 1000 gallons of JP4 fuel ‐ sandy soil, shallow aquifer ‐ benzene C6H6 toluene C7H8 assume this stoichiometry as average xylenes C8H10 ‐ theore5cal complete degrada5on of the spill C7H8 + 4O2 + NH3 C5H7O2N + 2CO2 + 2H2O mw 92 128 17 113 ‐ 6,000 lbs fuel ‐ 1,110 lbs ammonia needed (~100 lbs phosphorus) ‐ 8,350 lbs oxygen needed ‐ 8,350 lbs oxygen needed ‐ water saturated with air, 8 mg/L ‐ water saturated with pure oxygen, 40 mg/L need 27,000,000 gallons of water ‐ can use peroxide need 20,400 lbs of peroxide 2H2O2 O2 + 2H2O ‐ also 7,370 lbs of cells produced ***Alterna5ve approach ‐ Use nitrate as the electron acceptor ‐ Need to know that the contaminants will be suscep5ble to biodegrada5on with nitrate ‐ Need to also carry out the feasibility study that it can take place under the soil geochemical condi5ons at the site Nitrate NO3‐ Advantages ‐ high solubility ‐ provides good distribu5on ‐ no iron oxyhydroxides ppts ‐ innocuous end product, N2 Disadvantages ‐ regulated in groundwater (10 mg/L) ‐ forma5on of nitrite Oxygen O2 ‐ rapid degrada5on ‐ low solubility ‐ poor mass transfer and distribu5on ‐ clogging around the well head from biomass and iron oxyhydroxide ppts Use the same example with nitrate instead of oxygen C7H8 + 3.2NO3‐ + 3.2H+ + NH3 C5H7O2N + 2CO2 + 1.6N2 + 3.6H2O mw 92 198 113 ‐ 6,000 lbs fuel ‐ 12,913 lbs nitrate ‐ solubility of KNO3 = 13.3 g/100 ml (0°C) ~ 12,400 gallons water Compare that with 27,000,000 gallons of water saturated with pure oxygen Bioremedia5on and in‐situ Treatment Deﬁni5ons: bios5mula5on bioaugmenta5on bioven5ng bioﬁlters bioreactors compos5ng landfarming, solid phase treatment in‐situ biotreatment ex‐situ biotreatment natural adenua5on Bioremedia5on and in‐situ Treatment 1. Deﬁni5ons: bios5mula5on‐ adding N, P to s5mulate biodegrada5on bioaugmenta5on‐ adding microbes to the contaminated site bioven5ng‐ adding air (oxygen) to s5mulate biodegrada5on bioﬁlters‐ pumping contaminated grdwater through treatment unit with microbes adached to a large surface area bioreactors compos5ng landfarming, solid phase treatment‐ adding nutrients to contaminated surface soil to s5mulate contaminant degrada5on in‐situ biotreatment vs ex‐situ biotreatment natural adenua5on‐ allowing naturally occurring microbes in the site to degrade contamina5on with site monitoring of speciﬁc parameters Prince William Sound, Alaska Knight Island Prince William Sound, Alaska Katmai Na5onal Park Bioremedia5on of oil impacted beach (ES&T) 2. Regulatory and cost compe55ve considera5ons ‐ Can it compete with other technologies in the marketplace? landfarming vs incinera5on ‐ How well established is the technology? e.g. TCE in groundwater‐ air stripping + vapor‐phase ac5vated carbon sorp5on is a known technology ‐ while biotreatment is less well known 3. Regulatory criteria can drive the decision on the process ‐ e.g. biotreatment can reduce pentachlorophenol 90‐99% from 2000 mg/kg to 200 or 20 mg/kg, incinera5on can cost several million dollars more. ‐ but if the criterion for cleanup is 10 mg/kg, biotreatment is insuﬃcient ‐ e.g. bioreactor treatment of PAH contaminated soil can reduce levels from >1000 mg/kg to 25 mg/kg in 10 days. ‐ cleanup criterion of 1.5 mg/kg needs 60‐100 addi5onal days can add several million dollars, makes incinera5on cost compe55ve conc. 5me 4. Criteria for selec5ng bioremedia5on a) Is the chemical biodegradable? ‐ what func5on does it serve? Is it the primary substrate or C source or electron donor? e.g. PAHs Is it an electron sink or electron acceptor? e.g. PCBs, TCE Are there inhibitors or poisons to biodegrada5on? b) Is there a community of degraders at the site? ‐ the likelihood is yes, if it is longstanding contamina5on especially for carbon based contaminants, e.g. petroleum compounds c) Is the environment habitable? ‐ is it too toxic for microorganisms? ‐ are there suﬃcient nutrients for growth? e.g. N, P, electron acceptors, other ‐ is the C:N:P ra5o met? ~ 30‐100:5‐10:1 d) What is the rate limi5ng factor and can it be modiﬁed? ‐ the most frequently encountered limi5ng nutrient for all prac5cal purposes is electron acceptor, e.g. O2 ‐ then N & P contaminant Bioavailable? Mobile? Sorbed? Toxicity? Nutrient limited? Oxygen limited? degradable? organism environment ‐ bioremedia5on most suitable for surface soil or sediment ‐ process typically needs a) site characteriza5on, physical and chemical b) treatability/feasibility study ‐ ﬂask, columns, microcosm ‐ this can provide answers to whether relevant microbes are present, amendments needed, toxicity at site ‐ diesel fuel contaminated soil ‐ meet criteria of 100 ppm total petroleum hydrocarbon (TPH) ‐ this requires a 95% reduc5on in TPH at site ‐ TPH represents ~50% of total organic carbon (TOC) ‐ baseline analyses show need for inorganic nutrients • data indicate N & P limita5on with respect to TPH • also note bacterial nos indicate site is not hazardous but petroleum degrada5on may be limited • heterogeneity of ‘no nutrient’ condi5on • importance of sterile control • interpret ‘plus inoculum’ data • best results with ‘plus nutrients’ Example 2 ‐ Soil contamina5on with no. 6 fuel oil, electric u5lity in FL. ‐ 3,200 barrels (509 m3) spilled onto surface, most of the free product recovered, leaving 900 barrels (140 m3) in surface soil, 6‐8 inches deep. ‐ Treatability studies used to evaluate land treatment alterna5ves PHC = petroleum hydrocarbon ‐ Field remedia5on & ac5ve management for 6 months ‐contaminated soil was consolidated to 44,000 p2 ‐samples taken before and during remedia5on ‐fer5lizer solu5on added weekly and totaled 3,600 lbs ‐plowing and 5lling carried out 4 to 5 5mes/week ‐ moisture content maintained ‐ ﬁve replicates taken at each sampling 5me • observe decrease in total hydrocarbons • observe less variability with5me Field data pristane, C‐19 branched alkane • lower mw cpds loss is more rapid, more vola5le & more easily degraded • ﬁeld treatment occurs over a rela5vely long 5me period ‐ aper ac5ve phase, passive phase took place for 3 yrs passive phase begins • aper 6 months, no visual or olfactory evidence of contaminants • passive phase, no further 5lling or nutrient addi5ons • con5nued deple5on of PAH, especially the high mw aroma5c components Ac5ve and passive treatment • peaks represent individual petroleum components • even during passive period, loss of petroleum components occurs naphthalene pyrene benzo(a)pyrene benzoperylene Example 3 • coal tar released into a wetlands, covered with aqua5c sediment, tar located in a concentrated submerged hydrophobic strata • used excava5on and land treatment approach Lab treatability studies, 6 in. depth site soil samples • site soil characterized • grew up indigenous PAH degraders for bioaugmenta5on • used radiolabeled 14C‐naphthalene for mineraliza5on study • established degree of 1)fer5lizer applica5on, 2) aera5on frequency, 3)loading rate, 4)amount vola5lized, 5)moisture content, 6)pH Laboratory studies • rate of degrada5on for 2 and 3 ring PAH • 2 ring PAH, napthalene, methyl‐ naphthalene CH3 • 3 ring PAH, phenanthrene, ﬂuorene Laboratory studies • gas chromatography of samples aper 12 days Field plot demonstra5on, pilot scale study (used seven 6 x 9 x 2 p plots) ‐ Condi5ons used were established in the lab studies • Rate and extent of degrada5on decreases with increasing mw of the PAH Field study test plot • loss of individual PAH components during ﬁeld trials • all frac5ons decreased, while smaller mw frac5ons decreased more quickly MICROBIALLY MEDIATED OXIDATION-REDUCTION REACTIONS
Electron donor reactions glucose toluene xylenes C6H12O6 } } } } CO2 + H2O (+ cells) C 7H 8 C8H10 benzene C6H6 Complete reactions Glucose (with O2) p-Cresol (+ nitrate) C6H12O6 + 6O2 C7H8O + 6.8NO36CO2 + 6H2O 7CO2 + 3.4N2 + 7.4H2O 7CO2 + 18H3AsO3 + 4H2O Toluene C7H8 + 18H2AsO4- + 18H+ (+ arsenate) 24 42 4 ENVIRONMENTAL AND POLLUTION MICROBIOLOGY PROBLEM SET 1. Write a balanced equa5on for the mineraliza5on of 2,4‐dichlorophenol to carbon dioxide under sulﬁdogenic condi5ons. You need not consider the produc5on of cells. 2. Write a balanced equa5on for the degrada5on of toluene to carbon dioxide under iron reducing condi5ons (Fe+3 —> Fe+2). You need not consider the produc5on of cells. 3. Compare the aerobic oxida5on of glucose to carbon dioxide and water (ignore cell produc5on) with the aerobic oxida5on of a comparable 6 carbon alkane (ignore cell produc5on). What is the diﬀerence in oxygen required? If you were asked to s5mulate the biodegrada5on of a 50,000 gallon spill of this alkane (~ 40 tons of petroleum) in a coastal environment, how much nitrogen (in tons) would be needed (assume a 10:1 ra5o of C:N)? What kinds of ecological consequences could result by adding this nutrient to this coastal environment site? ...
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- Spring '11
- Benzene, PAH, electron acceptor, Prince William Sound, bioreactors compos5ng landfarming, lbs oxygen