Biotreatment of industrial effluents CHAPTER 7 – fluoride removal CHAPTER 8 – biodegradation of pesticides

Biotreatment of industrial effluents CHAPTER 7 – fluoride removal CHAPTER 8 – biodegradation of pesticides Biotreatment of industrial effluents CHAPTER 7 – fluoride removal CHAPTER 8 – biodegradation of pesticides Biotreatment of industrial effluents CHAPTER 7 – fluoride removal CHAPTER 8 – biodegradation of pesticides Biotreatment of industrial effluents CHAPTER 7 – fluoride removal CHAPTER 8 – biodegradation of pesticides Biotreatment of industrial effluents CHAPTER 7 – fluoride removal CHAPTER 8 – biodegradation of pesticides

C H A P T E R 7

Fluoride Removal

Introduction

Fluoride exists in the environment as a result of both natural and anthro- pogenic causes The natural contamination of groundwater by fluoride ions

is due to leaching of fluoride from rocks (soil) into the aquifers, while the wide use of fluorinated compounds by industry is the major anthropogenic cause In the former situation, the fluoride is in an ionic form, while in the latter it may be present in a covalent form This chapter deals with the removal of both these types of fluorine

Organofluorine Compounds

The synthetic diversity of nature is also reflected in a large number of naturally produced halogenated compounds discovered in many different organisms Until today, more than 3,500 halogenated metabolites have been isolated from bacteria, fungi, marine algae, lichens, higher plants, mammals, and insects Whereas brominated metabolites are predominant in the marine environment, chlorine-containing metabolites are preferentially produced

by terrestrial organisms Although fluorine is the most abundant halogen in the earth's crust, biologically produced fluorinated metabolites are quite rare,

as is the case of iodated metabolites Hence, many fluorinated compounds

in the environment are of anthropogenic origin, making them recalcitrant

to degradation

The chemicals of humanmade origin that are used as refrigerants, fire retardants, paints, solvents, herbicides, and pesticides are predominantly halogenated organic compounds and cause considerable environmental pol- lution and human health problems as a result of their persistence and toxicity (Mohn and Tiedje, 1992) They also transform into hazardous metabolites

As a general rule, the strength of resistance to enzymatic cleavage of carbon- halogen bonds is observed to increase with the electronegativity of the substituents, in the order F C>C1-C>Br-C>I C

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84 Biotreatment of Industrial Effluents

Sodium monofluroacetate is highly toxic to most endothermic ver- tebrates and many invertebrates Plant species belonging to the genus

Gastrolobium are known to produce fluoroactates Several genera of soil fungi (Fusarium and Pencillium) and bacteria (Pseudomonas and Bacillus)

are known to degrade fluoroactates (Twigg and Socha, 2001)

Because of the concern over the depletion of stratospheric ozone by chlorofluorocarbons (CFCs), the use of hydrochlorofluorocarbons (HCFCs) such as HCFC-123 (2,2-dicloro-1,1,1-trifluoroethane) and HCFC-141 (B)(1,1- dichloro-1-fluoroethane) are banned (Fig 7-1 ) Halothane (1-bromo-1-chloro- trifluoroethane) is used as an anesthetic gas These compounds have many

of the physical properties of the corresponding chloroflurocarbons (CFCs) The presence of C m H bond makes this group of compounds susceptible to hydroxylation by monooxygenases (Anders, 1991) There are at least two pathways by which these compounds are biodegradedmthe reductive and the oxidative derivatives The reductive pathway proceeds through a free radical (Fig 7-2), while the oxidative pathway proceeds through the corresponding hydroxylated compound, which is further degraded to an acid derivative in the presence of water (Urban and Dekant, 1994)(Fig 7-3)

H H

FIGURE 7-1 Structures of common organofluorine compounds

CI- Br

CI

H " ~ ~ F

F

CI- Br 7

l - B r -

OI

H

FIGURE 7-2 Reductive degradation of halothane

Fluoride Removal 85

- H C I CI

O / +H20

FIGURE 7-3 Oxidative degradation of HCFC-123

New et al (2000)reported the degradation of 4-fluorocinnamic acid (a common reagent in the synthesis of pharmaceuticals) to 4-fluorbenzoic acid using activated sludge Fluorine is isosteric to hydrogen; hence most

of the enzymes bringing about transformation of aromatic compounds will transform fluorinated aromatic compounds, too In general, the isosteric

replacement, even though it represents a subtle structural change, results in

a modified profile: some properties of the parent molecule remain unaltered while others will be changed The similar shape and polarity within a series

of substrates of different reactivity ( b i o i s o s t e r e s ) e l i m i n a t e s effects due to differences in enzyme-substrate binding [ES] and h e n c e is a good m e t h o d of

e x t e n d i n g the range of substrates that can be chosen for the transformation

A number of instances can be cited from the literature wherein the

isosteres had similar transformations The isosteres, 1,2-dihydro naphtha- lene, 2,3-dihydro benzothiophene, and 2,3-dihydro benzofuran, gave similar corresponding diol products on incubation with P s e u d o m o n a s p u t i d a UV4 Microbes, which possess the metabolic pathways to metabolize benzene, substituted benzenes, and phenols were found to metabolize fluorinated benzenes (isosteres)in a similar manner (Fig 7-4)

eutrophus ~ ' " H

FIGURE 7-4 Degradation of benzoic acid isosteres

86 Biotreatment of Industrial Effluents

Fluorobenzoic acids have been reported to degrade under both aerobic and anaerobic conditions (Vargas et al., 2000) Several pathways have been identified under aerobic conditions, but two are most widely reported One pathway involves the degradation of fluorobenzoic acids into the correspond- ing fluorocatechol; in the other pathway, fluorobenzoic acid is transformed into hydroxyl benzoic acid

Fluoride Contamination of Water and Treatment

Water gets contaminated by dissolving the pollutants in the lithosphere and also from anthropogenic causes Fluorine is the thirteenth most abundant element in the earth's crust and is available in combined form as fluorspar (CaF2), cryolite (NagA1F6), fluoroapatite [Ca5F(PO4)3], topaz [A12SiO4 (OH, F)2], sellaite (MgF2), villiamite (NaF), bastnaesite (CoF2), and fluorine hydrosilicates Geological formation is the main source of fluoride in the groundwater Fertilizers and pesticides, which contain about 1 to 3% fluo- ride, also contribute to its presence in the groundwater (Mariappan, 1996) The presence of fluoride ion in drinking water may be beneficial or detrimen- tal to public health, depending on the concentration in which it is found Fluoride intake beyond the limit of 1.5 mg/L causes dental and skeletal flu- orosis and nonskeletal manifestations (Chen et al., 1995) Excess fluoride in drinking water is a major environmental problem in over 21 nations About

15 million people are living in 3,500 endemic habitations of 16 states of India (Mariappan et al., 2000)

Because of the proven health danger of excess fluoride ion, governments routinely monitor the environment for its presence In cases where control strategies have been implemented, there have been significant decreases in environmental metal levels

Several methods have been advocated for defluoridation of drinking water They can be broadly divided into two categories, viz., those based upon the addition of some material to the water during the softening or coagulation process and those based upon ion-exchange or adsorption pro- cesses Adsorption or ion-exchange processes are recommended for low concentration treatment These processes are performed by using lime and alum, bone char and synthetic bone, activated carbon and bauxite, ion-exchange, activated alumina, and reverse osmosis Among these materi- als, activated alumina is supposed to be the most effective and economic adsorbent for removal from drinking water of fluoride in the lower con- centration range But so far most of the methods developed could not find any practical application because of high capital and operating cost and complexity of operating procedure Even the Nalagonda Technique, involving the addition of aluminium salts, lime, and bleaching powder, has its shortcomings in the form of sludge disposal problems (Nawlakhe and Rao, 1990)

Fluoride Removal 87

Defluoridation methods involving adsorption have been developed Charred coconut shells or dry fibrous plant material have been used These methods have the obvious problem of leachates that might alter the water quality, making it unsuitable for drinking purposes

Pollutants that continue to be of enormous practical and economic importance are of heavy metals, such as lead, mercury, and cadmium; and inorganic anions such as fluoride, nitrate, and carbonate These natural elements and compounds, found in the earth's crust, are utilized in many industrial processes and products, a use which has resulted in their release in higher concentrations and in more accessible form than is typical in natural systems Incorporation of heavy metals into inorganic and organometallic complexes and anions into organic compounds (fluorocitrates)often alters their biological activity; such changes are just as likely to increase toxi- city because of increased bioavailability as they are to decrease toxicity Furthermore, depending on conditions of pH, increased temperature, etc., natural cycles may intervene to convert or mobilize relatively benign inor- ganic species to more toxic organic complexes (e.g., conversion of elemental mercury to methylmercury and fluoride to fluorocitrate)

Unlike organic pollutants, the toxicity of fluoride ion is inherent in its atomic structure, and it cannot be further transmuted or mineralized

to a totally innocuous form Its oxidation state, solubility, and association with other inorganic and organic molecules can vary, however; microbes as well as higher organisms may play a bioremediative role by transforming and concentrating these anions so that they are less available and less dangerous Many plants and bacteria have evolved various means of extracting essential nutrients, including anions, from their environment Such organ- isms may provide the opportunity to make fluoride less available However, a practical phytoremedial technology remains to be developed Anion binding can be brought about by any of the following three methods, viz:

9 Hydrogen bonding interaction

9 Electrostatic interaction

9 Hydrogen bonding with electrostatic interaction

Many microorganisms secrete high-affinity anion-binding compounds called ionophores (e.g., valinomycin, which binds to halides) The ionophores bind specific chemical forms of anions, and the anion-ionophore complex is then absorbed back into the organism for utilization A bioremediation tech- nology using native and chemically modified ionophores attached to inert support media would give good results

In a recent study conducted on the ability of amino acids to bind and defluoridate water, the basic amino acids (lysine, arginine, and asparagine) were found to be effective (Kumar et al., unpublished work) Extension of this study led to the understanding that proteins are capable of selectively binding

to fluoride and are therefore suitable for bringing about defluoridation of

88 B i o t r e a t m e n t of I n d u s t r i a l Effluents

water Microorganisms and plants exude a number of enzymes (proteins) that may have this ability of binding to fluoride, thus making it less available

In the last decade, hairy roots have helped markedly in phytoremedia- tion The root zone is the part of the plant that is in intimate contact with the contaminant; hence this part should be targeted for the expression of foreign genes with a view toward enhancing the uptake, bioaccumulation, or bio- transformation of specific compounds Alongside roots of higher plants, the subterranean complex of mycelia associated with mushroom growth would appear to offer a number of possibilities in the field of remediation

Existing technologies for defluoridation of drinking water are not prac- tical; hence, a concerted effort to develop a bioremediation method is needed Plants or microorganisms capable of transforming or accumulating fluoride ions are the only viable solutions to this vexing problem

R e f e r e n c e s

Anders, M W., 1991 Environ Health Perspect 96:185-191

Chen, H S., S T Huang, and H R Chen 1995 Bull Environ Contamin Toxic 55:709-715

Kumar, A K., Ch Janardhana, and S Sateesh, unpublished work, Department of Chemistry, Sri Satya Sai Institute of Higher Learning, PN, A P., India

Maraippan, P., V Yegnaraman, and T Vasudevan 2000 Poll Res 19(2): 165-177

Mariappan, P 1996 J IWWA XXVIII(3): 184

Mohn, W W., and J M Tiedje 1992 Microbiol Revs 56:482-507

Nawlakhe, W G., and A V Jagannadha Roa 1990 J IWWA XX(2): 287-291

New, A P., L M Freitas dos Santos, G lo Biundo, and A Spicq 2000 J Chromat (A)

889:177-184

Twigg, L E., and L V Socha 2001 Soil Biology & Biochemistry 33:227-234

Urban, G., and W Dekant 1994 Xenobiotica 24:881-892

Vargas, C., B Song, M Camps, and M M Haggblom 2000 Appl Microbiol Biotechnol 53:342

C H A P T E R 8

Biodegradation of

Pesticides

Introduction

Pesticides are a group of chemicals used for the control and prevention

of pests such as fungi, insects, nematodes, weeds, bacteria, and viruses Depending on the class of pests they act against, they are broadly classified as:

Fungicides

Herbicides

Insecticides

Nematocides

Rodenticides

Algicides

Antifoulings

Biocides

Defoliants

Desiccants

Plant growth regulators

Miticides or acaricides

Kill fungi Classes include dithiocarbamates, copper, mercurials, etc

Kill weeds and other unwanted plants Classes include carbamates, triazines, phenylureas, phenoxyacetic acids, etc

Kill insects Classes include organophosphates, carbamates, organochlorines, pyrethrins, pyrethroids, etc

Kill nematodes

Kill rodents like mice

Control algae infestations in water channels and swimming pools

Control pests that affect underwater surfaces, like boats

Kill microorganisms

Cause leaves or other foliage to drop from plants Cause drying of living tissues

Alter growth, blooming, or reproductive rates of plants

Kill mites

Pesticides can also be broadly classified on the basis of their significant chemical properties and reported behavior in soils and water as ionic and

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90 Biotreatment of Industrial Effluents

nonionic The following list gives types of ionic pesticides and a few examples

9 A c i d i c ~ D i c a m b a , Ioxynil, 2,4,5-T, Dichlorprop, Mecoprop

9 Basic m Propazine, Cyanazine, Atrazine, Simazine

9 Cationic ~ Diquat, Paraquat, Chlormequat

9 O t h e r s ~ I s o c i l , Bromacil, cacodylic acid, MSMA

The categories of nonionic pesticides and some examples follow

9 A c e t a m i d e s ~ C D A A

9 Benzonitriles -Dichlobenil

9 E s t e r s ~ t h e methyl ester of Chloramben

9 T h i c a r b a m a t e s ~ D i a l l a t e , Nabam, M e t h a m

9 Dinitro a n i l i d e s ~ Nitralin, Isopropalin, Oryzalin

9 C a r b a n i l a t e s ~ S w e p , Barban, Prophan

9 Chlorinated hydrocarbons m D D T , Heptachlor, Endrin, Methoxychlor

9 O r g a n o p h o s p h a t e ~ E t h i o n , Methyl parathion, D e m e n t o n

9 A n i l i d e s ~ D i p h e n a m i d e , Solan, Propanil

9 C a r b o t h i o a t e s ~ M o l i n a t e

9 U r e a s ~ D i u r o n , Buturon, Norea, Siduron

9 Methyl c a r b a m a t e s ~ Z e c t r a n , Carbaryl, Terbutol

Pesticides are highly soluble in water and hence cannot be easily extracted

In addition they bind very strongly to soil Several methods have been employed to degrade pesticides and to reduce their toxic nature The main problem arises when the pesticides, which may be non-toxic, get degraded to toxic products The methods used for degradation of pesti- cides are:

9 Chemical treatment m A c o m m o n l y used method is alkaline hydrolysis, where the pesticide is neutralized with an aqueous alkaline solution

9 PhotodegradationmProcess by which pesticides are broken down by the action of light, particularly sunlight

9 E l e c t r o c h e m i s t r y ~ Effective degradation of chlorobenzoic and chlorophe- noxy herbicides has been reported using electrochemical cells at a pH

of 3.0

9 Incineration m This method is costly and requires long-distance transport

to a central facility, which may not be approved by the general public

9 B i o r e m e d i a t i o n m T h i s method uses microorganisms for degradation Major problems encountered in the use of bioremediation are compound specificity, slow rates of degradation, incomplete metabolism, biofilm maintenance, and the survivability of engineered strains in the presence

of natural populations

Biodegradation of Pesticides 91

Insecticides

Insecticides are among the most widely used compounds, finding application

in agriculture and disease control They may be broadly classified as follows:

Organochlorines - - They contain organic carbon, hydrogen, and chlorine They include compounds such as:

9 Diphenyl aliphatics - - Compounds like DDT (dichlorodiphenyl trichloro ethane) and hexchlorocyclohexane They act primarily by blocking synaptic transmission in the nervous system of insects and are the most successful insecticides ever produced

9 Cyclodienes - - Compounds like Aldrin, Deldrin, and Heptachlor Used in the soil to control termites

Organophosphates - - All insecticides containing phosphorus They are the most toxic of all pesticides to vertebrates; however, they are unsta- ble or nonpersistent They contain compounds like Malathion, Ethyl Parathion and Diazinon (Fig 8-1 )

O r g a n o s u l p h u r s - Tetradifon

Carbamates

Formamidines

Dinitrophenols

Organotins and several others

Although pesticides like DDT may not be directly harmful to humans, even

if the person is in close contact with the chemical, a phenomenon known as biomagnification or bioconcentration occurs, which is a very serious effect and affects organisms higher up in the food chain The concept of biomagni- fication is shown in Fig 8-2 Bioconcentration values of 58 to 5,100 were observed for Chlorpyrifos in fish There were similar findings for Diazi- non, where the numbers vary from 17.5 to 200 in fish For carbofuran, it

is ranges from 10 in snails to over 100 in fish The World Health Organi- zation estimates 3 million cases of acute severe poisonings, with 220,000 deaths, because of organochloro insecticides annually around the world

D D T

This compound comes under the class of compounds known as diphenyl aliphatics A gram-positive bacterium could degrade DDT, DDD (dichlorodiphenyl dichloro ethane), and DDE (dichlorodiphenyl e t h a n e ) i n the presence of biphenyl A consortium of the microorganisms (primarily

Serratia marcescens) degraded 25 ppm of DDT in 144 h under aerobic con-

ditions DDT degradation was extensive in the presence of white rot fungus,

Phanerochaete chrysosporium, which is a basidomycete

92 Biotreatment of Industrial Effluents

Ethyl parathion

s / - - \

CI

I

CI C CI

c,-C

H DDT

$

H3C O II ~p

Malathion

O

O

CH 3 CH3

FIGURE 8-1 Structures of various insecticides

TABLE 8-1

Strains and Reactor Systems Used for DDT Degradation

Various mutant strains of white rot

fungi

P chrysosprium pellets

P chrysosprium BKM-F 1767 or ME 446

Various mutant strains of white rot

fungi

P chrysosprium BKM-F 1767 and SC26

P chrysosprium BKM-F 1767

P chrysosprium ME 46, Inonotus

dryophilus, and Trametes versicolor

P chrysosprium I 1512

Nylon web and polyurethane inserted into bioreactor

Pilot scale stirred tank reactor Air-lift

Stirred tank Nylon sheet inserted into reactor Polyurethane inserted into stationary reactor

Polyurethane inserted into agitated reactor

Rotating biological contactors Stirred tank reactor

Hollow fiber reactor Silicon membrane reactor Rotating tube bioreactors

Nylon net inserted into reactor

Reactor Systems Different reactor s y s t e m s have been e m p l o y e d u n d e r varying conditions, and t h e y are s u m m a r i z e d in Table 8-1 One of the m o s t effective w a y s to treat D D T using the b a s i d i o m y c e t e is the use of a p a c k e d bed reactor using w o o d chips as a carrier for the biomass O p t i m u m degrada- tion occurred at 30~ and a pH of 4.5 w h e n kept for 30 days at low glucose levels (0.1%) and w i t h o u t any n i t r o g e n source I n t e r m e d i a t e s isolated in the