1 Groundwater Pollution Using the characteristics of living things as tools for environmental improvement - exercises & case studies

2 The pollution of groundwater by organic chemicals affects 300,000 to 400,000 contaminated sites in the USpollutiongroundwater contaminated Picture:

3 BioremediationBioremediation is when organisms either metabolize or fix contaminants

4 ContaminantOrganisms Less harmful chemicals

5 ContaminantOrganisms Contaminants are fixed

6 Bioremediation is any process that uses microorganisms, fungi, green plants or their enzymes to return the contaminated environment to its original condition.

7 Because there is too much of something we need to either reduce it or immobilize (fix) it

8 Other Names Bioremediation is also called enhanced ( 늘리다 ) bioremediation or engineered bioremediation.

9 Aerobic bioremediation usually involves oxidative processes Contaminants may be partially oxidized to less toxic thingspartiallytoxic Contaminants may be fully oxidized to chemicals such as carbon dioxide and waterfully

10 BTEX (Benzene, Toluene, Ethylbenzene, and Xylenes) are monoaromatic hydrocarbons which are in petroleum and petroleum products such as gasoline.monoaromatic hydrocarbons

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12 If there is enough oxygen more degradation can happen degradation

13 If there is enough oxygen they can degrade to water and carbon dioxide 2C 6 H O 2 12CO 2 + 6H 2 O

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15 Microorganism Inputs Outputs Boundary Organic pollutant & Oxidized electron Acceptor (O 2 ) Energy Environment CO2 + H2O + other waste Products + Reduced electron Acceptor (H 2 O) Energy Feedback

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17 The organisms make chemical reactions happen Balance these reactions Benzene (a component of gasoline) 2C 6 H O 2 ?CO 2 + ?H 2 O Alanine (an amino acid) 4C 3 H 4 NH 2 O 2 H + 15O 2 12CO H 2 O + ?

18 The organisms make chemical reactions happen Balance these reactions Benzene (a component of gasoline) 2C 6 H O 2 12CO 2 + 6H 2 O Alanine (an amino acid) 4C 3 H 4 NH 2 O 2 H + 15O 2 12CO H 2 O + 2N 2

19 These chemical equations are used to calculate how many other chemicals need to be added 150 kg of analine needs to be degraded. How much oxygen needs to be supplied?

20 Atomic weights N=14 O=16 H=1 C=12 C 3 H 4 NH 2 O 2 H = 89 4C 3 H 4 NH 2 O 2 H needs 15O / 89 x 4 = X / 32 x 15 X = 202 kg O 2

21 Bioremediation might be improved We could add more or better organisms to the soil (bioaugmentation)

22 We could help the organisms grow by changing things in the environment (biostimulation)

23 How could we stimulate the growth of microorganisms?

24 How could we stimulate the growth of microorganisms? We could add nutrients, change the pH, change the temperature, and add or remove oxygen. Eg Benzene 2C 6 H O 2 12CO 2 + 6H 2 O

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26 We can engineer the conditions Engineered bioremediation involves supplying oxygen (or other electron acceptor), water, and nutrients at the correct rate so that the naturally existing microorganisms are stimulated to degrade the contaminants.stimulated

27 Microbial biodegradation of pollutants occurs most rapidly under certain optimal conditions:rapidly Temperature (15-30 C) High moisture content High oxygen content Nutrient availability Usually neutral pH (~7) Constant ionic strength Absence of toxic inhibitors Biotechnological plants try to maintain optimal conditions for micro-organismsoptimal

28 How can we follow what is happening?

29 Signs of Biological Activity Biological activity will result in decreased oxygen concentration (for aerobic processes) and increased metabolites (e.g. CO 2 ). metabolite

30 ContaminantOrganisms Less harmful chemicals We can count this, this or this.

31 Types of Contaminants Bioremediation is commonly used for: Organic contaminants Some inorganic pollutants such as ammonia, nitrate, and perchlorate Changing the valence states of heavy metals to convert them into immobile or less toxic forms. (eg mobile hexavalent chromium into immobile and less toxic trivalent chromium)

32 Perchlorates are the salts of perchloric acid (HClO 4 ). They are commonly found in rocket fuel and explosives, often those used by the military.

33 Advantages of Bioremediation It may result in complete degradation of organic compounds to nontoxic byproducts. Not much equipment is needed Bioremediation does not change the natural surroundings of the site. Low cost compared to other remediation technologies.

34 Advantage 우위 Toxic ≠ nontoxic equipment 설비

35 Disadvantages of Bioremediation There could be partial degradation to metabolites that are still toxic and/or more mobile in the environment. Biodegradation is easily stopped by toxins and environmental conditions. We have to always measure biodegradation rates. Generally requires longer treatment time as compared to other remediation technologies.

36 Partial 불완전한 Mobile 가동성의 Rate 속도, 진도

37 Bioremediation processes may give: complete oxidation of organic contaminants (called mineralization), biotransformation of organic chemicals into smaller parts, or reduction of halo- and nitro- groups by transferring electrons from an electron donor (eg a sugar or fatty acid) to the contaminant, resulting in a less toxic compound.

38 Usually electron acceptors are used by bacteria in order of their thermodynamic energy yield : oxygen, nitrate, iron, sulfate, carbon dioxide.

39 The major nutrients needed include carbon, hydrogen, oxygen, nitrogen and phosphorous. The amount which needs to be added depends on what is already there. Generally, the C to N to P ratio (w/w) required is 120:10:1.

40 Bioreactors are biochemical-processing systems designed to degrade contaminants using microorganisms. Contaminated water flows into a tank, where microorganisms grow and reproduce while degrading the contaminant. The biomass produced is then separated from the treated water and disposed of as a biosolids waste. This technology can be used to treat organic wastes (BOD), ammonia, chlorinated solvents, propellants, and fuels.

41 Artificial wetland ecosystems (organic materials, microbial fauna, and algae) can remove metals, explosives, and other contaminants from inflowing water. The contaminated water flows into the wetland and is processed by wetland plants and microorganisms to break down and remove the contaminants.

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43 Constructed wetlands

44 Bioremediation ( 김동진 교수 ) Relies on microorganisms to biologically degrade groundwater contaminants through a process called biodegradation. It may be engineered and accomplished in two general ways: (1) stimulating native microorganisms by adding nutrients, oxygen, or other electron acceptors (a process called biostimulation); or (2) providing supplementary pregrown microorganisms to the contaminated site to augment naturally occurring microorganisms (a process called bioaugmentation).

45 Bioremediation ( 김동진 교수 ) It mainly focuses on remediating organic chemicals such as fuels and chlorinated solvents. One approach, aerobic bioremediation, involves the delivery of oxygen (and potentially other nutrients) to the aquifer to help native microorganisms reproduce and degrade the contaminant.

46 Bioremediation ( 김동진 교수 ) Another approach, anaerobic bioremediation, circulates electron donor materials—for example, food-grade carbohydrates such as edible oils, molasses, lactic acid, and cheese whey—in the absence of oxygen throughout the contaminated zone to stimulate microorganisms to consume the contaminant. In some cases, pregrown microbes may be injected into the contaminated area to help supplement existing microorganisms and enhance the degradation of the contaminant, a process known as bioaugmentation.

47 Bioremediation can be used to treat groundwater and landfillslandfills

48 Bioremediation

49 Bioreactor

50 Phytoremediation Selected vegetation reduces, removes, and stops the toxicity of environmental contaminants, such as metals and chlorinated solvents.

51 What does Phytoremediation do?

52 In Situ Phytoremediation System

53 Aerobic is often faster than anaerobic degradation However, many compounds can only be metabolized under reductive conditions. Then anaerobic metabolism is needed.

54 One type of anaerobic bioremediation is reductive dehalogenation where the contaminants are made less toxic by removal of halogens such as chlorine or nitro groups.halogens

55 In the degrading of tetrachloroethene

56 Anaerobic = no oxygen Tetrachloroethene is reduced with e - H 2 is the electron donor

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58 Microorganism Inputs Outputs Boundary Electron donor (sugar, fatty acid, H 2 ) & Electron acceptor (electrophilic pollutant) Energy Environment Oxidized electron donor CO2 + H2O and other fermentation products + Less halogenated pollutant and Cl - Energy Feedback

59 At many contaminated sites, organisms naturally exist that can degrade the contaminants But not all sites have organisms that work. Some sites don’t have the right conditions (such as electron acceptors) for fast degradation of the contaminants.

60 In methanogenic bioremediation, the contaminants are converted to methane, carbon dioxide and traces of hydrogen.

61 Energetics In order for energy to be released from an oxidation/reduction reaction, an overall negative Gibb’s free energy must exist. Different inorganic compounds can be used as terminal electron acceptors by bacteria during respiration. Anaerobic respiration usually gives lower energy than aerobic.

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63 Questions Describe these examples of bioremediation. Use the system model. State what the electron acceptors and donors are. 1. Water from a beef farm has a high level of organic wastes. It is treated by aeration.aeration

64 Ground Water Flow Plume of Dissolved Fuel Hydrocarbons Residual NAPL Mobile LNAPL Pool Methanogenesis Sulfate Reduction Iron (III) Reduction Dentrification Aerobic Respiration (Source: W,R, N, & W, 1999.)(Adapted from Lovley et al., 1994b.) 2. Some oil is spilt on the ground

65 3. Dissolved oxygen depletion (From: Environmental Science: A Global Concern, 3rd ed. by W.P Cunningham and B.W. Saigo, WC Brown Publishers, © 1995)

66 From: Atlas and Bartha, Breaking aromatic rings

67 Organic Carbon Oxidized Product Oxidation to yield energy; can be multiple steps e-e- Terminal e - Acceptor Reduced Product Reduction to provide e - “sink” (costs energy) General Metabolic Redox Model in Microorganisms

68 Organic Carbon CO 2 e-e- O2O2 H2OH2O Energy production; multiple steps Aerobic respiration General Model for Aerobic Respiration

69 CH 4 CH 3 OH e-e- O2O2 H2OH2O Energy production Coupled reduction Aerobic Respiration: Examples and Cometabolism Benzene CO 2 Energy production TCE CO 2 No energy production; cometabolism