Aerobic and Anaerobic Degradation of Xenobiotics

Except for pesticides and insecticides, which are widely used in horticulture and farming and small amounts of which are washed into the groundwater, many xenobiotics are spilled in the environment, by spot contamination or contamination of large areas. Biological remediation of soil and groundwater contaminated with gasoline (e.g., Yerushalmi and Guiot, 1998) and the volatile fractions of diesel oil (e.g., Greiff et al., 1998), even at low temperatures (Margesin and Schinner, 1998), seems to be no problem. Results of many laboratory and field studies with a variety of substances are available (e.g., Arendt et al., 1995; Hinchee et al., 1995a, b; Kreysa and Wiesner, 1996). Except for studies in complex field or wastewater environments, many xenobiotics can be degraded by aerobic or anaerobic pure or defined mixed cultures (Table 1.7). These include monoaromatic and polyaromatic substances with or without chloro substituents. Whereas the two-ring compound naphthalene is relatively easily degradable by Pseudomonas sp. and Rhodococcus sp., the four-ring compounds fluoranthene and pyrene are much less degradable by Rhodococcus sp. (Bouchez et al., 1996). Aromatic compounds such as phenol and benzoic acid are degradable by mixed consortia at rates up to 1g L-1 d-1 in either the presence or absence of oxygen (Morsen and Rehm, 1987; Knoll and Winter, 1987; Kobayashi et al., 1989). A potent population is required, which can be obtained by preincubation. Even PCP is biodegradable by a methanogenic mixed culture from UASB granules (Juteau et al., 1995; Wu et al., 1993; Kennes et al., 1996). Some pure cultures and mixed cultures are capable of dechlorinating aromatic or aliphatic compounds

(Table 1.7, second part). As for the aerobic and anaerobic degradation of phenol, the rates of dechlorination of 2-chlorophenol under aerobic and anaerobic conditions are the same order of magnitude, 102 and 128 mg L-1 d-1, respectively (Kafkewitz et al., 1996; Dietrich and Winter, 1990). A pure culture of Pseudomonas pickettii was used for aerobic dechlorination, but for anaerobic degradation a mixed culture was used. The main problem in degradation of xenobiotic compounds in wastewater is a too short residence time in the reactors, which does not allow selection or adaptation of bacteria for dechlorination or degradation. Only if a permanent pollution is prevalent, the degradation potential may develop with time. Alternatively, biofilm reactors should be used to enrich dechlorinating and xenobiotic-degrading bacteria.

Table 1.7 Aerobic and anaerobic degradation or dechlorination of xenobiotics.

(mg L-1 d-1)

Microorganisms

Reference

Aerobic degradation

2-Hydroxy-

138

Rhodococcus rhodochrous

De Wever et al.

benzothiazole

(1997)

Naphthalene

57

Pseudomonas sp.

Bouchez et al. (1996)

Rhodococcus sp.

Fluoranthene

6.6

Rhodococcus sp.

Bouchez et al. (1996)

Pyrene

6.6

Rhodococcus sp.

Bouchez et al. (1996)

Pyrene

0.56

Mycobacterium flavescens

Dean-Ross and

Cerniglia (1996)

Toluene

57

Pseudomonas putida

Heald and Jenkins

(1996)

Phenol

188

Bacillus sp. A2

Mutzel et al. (1996)

Phenol

1000

mixed immobilized culture

Mörsen and Rehm

(1987)

Cresol (o, m, p)

259

mixed immobilized culture

Mörsen and Rehm

(1987)

2,4- Diphenoxy-acetic

33

Alcaligenes eutrophusa

Valenzuela et al.

acid

JMP134 (pJP4)b

(1997)

2,4,6-Trichlorophenol

15

JMP134 (pJP4)b

Valenzuela et al. (1997)

Anaerobic degradation

Pentachlorophenol

107

methanogenic mixed culture,

Juteau et al. (1995)

(PCP)

fixed film reactor

PCP

90

methanogenic mixed culture

Wu et al. (1993)

UASB

PCP

4.4

methanogenic granules

Kennes et al. (1996)

PCP

22.7

methanogenic mixed culture

Juteau et al. (1995)

Table 1.7 Aerobic and anaerobic degradation or dechlorination of xenobiotics (Continued).

Reaction Substance

Rate Microorganisms

Reference

Benzene

Phenol

Phenol

Phenol Benzoic acid Toluene Toluene

Xylene Xylene

0.029

1000

Aerobic Dechlorination

2-Chlorophenol 102

4-Chlorophenol 41

1,3-Dichloro-2- 671 propanol

Tetrachloroethene 35.8 totalc

Anaerobic Dechlorination

2,6-Dichlorophenol 38.4

4-Chlorophenol 2-Chlorophenol

2-Chlorophenol

3-Chlorobenzoate

0.43 128

3-Chloro-4-hydroxy- 29.9 benzoate

Polychlorinated biphenyls (PCBs):

2.3.4.6-CB Tetrachloroethene

sulfate-reducing mixed culture methanogenic mixed culture syntrophic mixed culture syntrophic mixed culture syntrophic culture sulfate-reducing mixed culture methanogenic mixed culture sulfate-reducing mixed culture methanogenic mixed culture

Pseudomonas pickettii Pseudomonas pickettii Pseudomonas pickettii anaerobic mixed culture methanogenic mixed culture sulfate-reducing consortium methanogenic mixed culture anaerobic mixed culture anaerobic mixed culture

Desulfitobacterium chlororespirans methanogenic granules anaerobic sediments anaerobic sediment methanogenic granules

Edwards and Gribic-Galic (1992) Knoll and Winter (1987)

Knoll and Winter (1989)

Kobayashi et al. (1989) Kobayashi et al. (1989) Edwards et al. (1992) Edwards and Gribic-Galic (1994) Edwards et al. (1992)

Edwards and Gribic-Galic (1992)

Kafkewitz et al. (1996)

Kafkewitz et al. (1996)

Kafkewitz et al. (1996)

Dietrich and Winter (1990)

Häggblom (1998) Dietrich and Winter (1990)

Kuo and Sharak Genthner (1996)

Kuo and Sharak Genthner (1996)

Sanford et al. (1996)

Natarajan et al. (1996) Berkaw et al. (1996) Wu et al. (1996) Christiansen et al. (1997)

1.7 Bioaugmentation in Wastewater Treatment Plants for Degradation of Xenobiotics | 39 Table 1.7 Aerobic and anaerobic degradation or dechlorination of xenobiotics (Continued).

Reaction Substance

Rate

Microorganisms

Reference

Tetrachloroethene 1.64

dichloro-ethenec Tetrachloroethene 2.05

dichloro-ethenec

DCB, TCB, TeCBe 1.24

methanogenic mixed culture Middeldorp et al.

strain TT 4B

strain MS-1

Sharma and McCarty (1996)

Krumholz et al. (1996)

a Alcaligenes eutrophus = Ralstonia eutropha. b pJP4 = 2,4-dichlorophenoxy acetic acid-degrading plasmid.

c Dehalogenation product: total dehalogenation or partial dehalogenation to the corresponding deha-

logenation product. d 2,3,4,5,6-CB = 2,3,4,5,6-chlorinated biphenyls.

e DCB = dichlorobenzene, TCB = trichlorobenzene, TeCB = tetrachlorobenzene.

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