BIOTECHNOLOGICAL ASPECTS - Kopykitab

Anuradha Prakashan, New Delhi

BIOTECHNOLOGICAL ASPECTS

OF

PHYTOREMEDIATION

Associate Professor

Department of Botany

Sri Aurobindo College

University of Delhi

Dr. Payal Mago

All rights reserved.

AuthorDr. Payal

ISBN No.: 978-93-82339-71-7

First Impression, March, 2014

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BIOTECHNOLOGICAL ASPECTS

OF

PHYTOREMEDIATION

DEDICATEDTO

MY FATHER

SRI V. M. MAGO

PAPATHANKS FOR BEING THERE FOR ME…..

FOR SHOWING ME THE WAY…

FOR BEING PATIENT WITH ME WHEN I MADE IT DIFFICULT FOR YOU….

FOR BELIEVING IN ME AND ENCOURAGING ME TO DREAM…

AND BEING SUCH AN INSPIRING PRESENCE IN MY LIFE.

PREFACE

Phytoremediation is the use of living green plants for insitu risk reduction and/or removal of contaminants fromcontaminated soil, water, sediments, and air. Speciallyselected or engineered plants are used in the process.Risk reduction can be through a process of removal,degradation of, or containment of a contaminant or acombination of any of these factors. Phytoremediationis an energy efficient, aesthetically pleasing method ofremediating sites with low to moderate levels ofcontamination and it can be used in conjunction withother more traditional remedial methods as a finishingstep to the remedial process.

One of the main advantages of phytoremediation is thatof its relatively low cost compared to other remedialmethods such as excavation. The cost ofphytoremediation has been estimated as $25 - $100 perton of soil, and $0.60 - $6.00 per 1000 gallons ofpolluted water with remediation of organics beingcheaper than remediation of metals. In many casesphytoremediation has been found to be less than halfthe price of alternative methods. Phytoremediation alsooffers a permanent in situ remediation rather thansimply translocating the problem. Howeverphytoremediation is not without its faults, it is a processwhich is dependent on the depth of the roots and thetolerance of the plant to the contaminant. Exposure ofanimals to plants which act as hyperaccumulators canalso be a concern to environmentalists as herbivorousanimals may accumulate contaminate particles in theirtissues which could in turn affect a whole food web.

CONTENTS

Chapter - I 5

Chapter - II 21

Chapter - III 36

Chapter- IV 49

Biblography 74

Introduction

Phytoremediation of Soil Metals

Phytoremediation : Using Plants toCombat a Stressed Environment

Genetic Engineering andPhytoremediation

CHAPTER - I

INTRODUCTION

The quality of life on Earth is linked inextricably to theoverall quality of the environment. In early times, webelieved that we had an unlimited abundance of landand resources; today, however, the resources in theworld show, in greater or lesser degree, ourcarelessness and negligence in using them. Theproblems associated with contaminated sites nowassume increasing prominence in many countries.

Contaminated lands generally result from pastindustrial activities when awareness of the health andenvironmental effects connected with the production,use, and disposal of hazardous substances were lesswell recognized than today. The problem is worldwide,and the estimated number of contaminated sites issignificant (Cairney 1993). It is now widely recognizedthat contaminated land is a potential threat to humanhealth, and its continual discovery over recent yearshas led to international efforts to remedy many of thesesites, either as a response to the risk of adverse healthor environmental effects caused by contamination or toenable the site to be redeveloped for use.

The conventional techniques used for remediation havebeen to dig up contaminated soil and remove it to alandfill, or to cap and contain the contaminated areas ofa site. The methods have some drawbacks. The firstmethod simply moves the contamination elsewhere and

Biotechnological Aspects of.......5

may create significant risks in the excavation, handling,and transport of hazardous material. Additionally, it isvery difficult and increasingly expensive to find newlandfill sites for the final disposal of the material. Thecap and contain method is only an interim solution sincethe contamination remains on site, requiring monitoringand maintenance of the isolation barriers long into thefuture, with all the associated costs and potentialliability.

A better approach than these traditional methods is tocompletely destroy the pollutants if possible, or at leastto transform them to innocuous substances. Sometechnologies that have been used are high-temperature incineration and various types of chemicaldecomposition (e.g., base-catalyzed dechlorination,UV oxidation). They can be very effective at reducinglevels of a range of contaminants, but have severaldrawbacks, principally their technological complexity,the cost for small-scale application, and the lack ofpublic acceptance, especially for incineration that mayincrease the exposure to contaminants for both theworkers at the site and nearby residents.

Bioremediation is an option that offers the possibility todestroy or render harmless various contaminants usingnatural biological activity.As such, it uses relatively low-cost, low-technology techniques, which generally havea high public acceptance and can often be carried outon site. It will not always be suitable, however, as therange of contaminants on which it is effective is limited,the time scales involved are relatively long, and theresidual contaminant levels achievable may not alwaysbe appropriate. Although the methodologies employed


are not technically complex, considerable experienceand expertise may be required to design and implementa successful bioremediation program, due to the needto thoroughly assess a site for suitability and to optimizeconditions to achieve a satisfactory result.

Because bioremediation seems to be a good alternativeto conventional clean-up technologies research in thisfield is rapidly increasing. Bioremediation has beenused at a number of sites worldwide, including Europe,with varying degrees of success. Techniques areimproving as greater knowledge and experience aregained, and there is no doubt that bioremediation hasgreat potential for dealing with certain types of sitecontamination.

Unfortunately, the principles, techniques, advantages,and disadvantages of bioremediation are not widelyknown or understood, especially among those who willhave to deal directly with bioremediation proposals,such as site owners and regulators. Here, we intendedto assist by providing a straightforward, pragmatic viewof the processes involved in bioremediation, the prosand cons of the technique, and the issues to beconsidered when dealing with a proposal forbioremediation. Some tests make an exhaustiveexamination of the literature of bioremediation oforganic (King etal 1997, National Research Council1993, Norris etal 1993) and inorganic pollutants(Hinchee 1995), and another test takes a look atpertinent field application case histories (Flathman, etal1993)


1.1 Principles of bioremediation

Environmental biotechnology is not a new field;composting and wastewater treatments are familiarexamples of old environmental biotechnologies.However, recent studies in molecular biology andecology offer opportunities for more efficient biologicalprocesses. Notable accomplishments of these studiesinclude the clean-up of polluted water and land areas.

Bioremediation is defined as the process wherebyorganic wastes are biologically degraded undercontrolled conditions to an innocuous state, or to levelsbelow concentration limits established by regulatoryauthorities (Mueller 1996). By definition, bioremediationis the use of living organisms, primarily microorganisms,to degrade the environmental contaminants into lesstoxic forms. It uses naturally occurring bacteria andfungi or plants to degrade or detoxify substanceshazardous to human health and/or the environment.The microorganisms may be indigenous to acontaminated area or they may be isolated fromelsewhere and brought to the contaminated site.Contaminant compounds are transformed by livingorganisms through reactions that take place as a part oftheir metabolic processes. Biodegradation of acompound is often a result of the actions of multipleorganisms. When microorganisms are imported to acontaminated site to enhance degradation we have aprocess known as bioaugmentation.

For bioremediation to be effective, microorganismsmust enzymatically attack the pollutants and convertthem to harmless products. As bioremediation can be


effective only where environmental conditions permitmicrobial growth and activity, its application ofteninvolves the manipulation of environmental parametersto allow microbial growth and degradation to proceed ata faster rate. Like other technologies, bioremediationhas its limitations. Some contaminants, such aschlorinated organic or high aromatic hydrocarbons, areresistant to microbial attack. They are degraded eitherslowly or not at all, hence it is not easy to predict therates of clean-up for a bioremediation exercise; thereare no rules to predict if a contaminant can bedegraded.

Bioremediation techniques are typically moreeconomical than traditional methods such asincineration, and some pollutants can be treated onsite, thus reducing exposure risks for clean-uppersonnel, or potentially wider exposure as a result oftransportation accidents. Since bioremediation isbased on natural attenuation the public considers itmore acceptable than other technologies. Mostbioremediation systems are run under aerobicconditions, but running a system under anaerobicconditions (Colberg and Young 1995) may permitmicrobial organisms to degrade otherwise recalcitrantmolecules.

The control and optimization of bioremediationprocesses is a complex system of many factors. Thesefactors include: the existence of a microbial populationcapable of degrading the pollutants; the availability of

1.2 Factors of bioremediation


contaminants to the microbial population; theenvironment factors (type of soil, temperature, pH, thepresence of oxygen or other electron acceptors, andnutrients).

Microorganisms can be isolated from almost anyenvironmental conditions. Microbes will adapt and growat subzero temperatures, as well as extreme heat,desert conditions, in water, with an excess of oxygen,and in anaerobic conditions, with the presence ofhazardous compounds or on any waste stream. Themain requirements are an energy source and a carbonsource. Because of the adaptability of microbes andother biological systems, these can be used to degradeor remediate environmental hazards.

In the presence of oxygen - Examples of aerobicbacteria recognized for their degradative abilities are

These microbeshave often been reported to degrade pesticides andhydrocarbons, both alkanes and polyaromaticcompounds. Many of these bacteria use thecontaminant as the sole source of carbon and energy.

In the absence of oxygen - Anaerobic bacteria are not

1.3 Microbial populations forbioremediation processes

These microorganisms can be divided intothe following groups:

Aerobic

Anaerobic:

:

Pseudomonas, Alcal igenes, Sphingomonas,Rhodococcus, and Mycobacterium.


as frequently used as aerobic bacteria. There is anincreasing interest in anaerobic bacteria used forbioremediation of polychlorinated biphenyls (PCBs) inriver sediments, dechlorination of the solventtrichloroethylene (TCE), and chloroform.

Fungi such as the white rot fungushave the ability to degrade an extremely

diverse range of persistent or toxic environmentalpollutants. Common substrates used include straw, sawdust, or corn cobs.

Methylotrophs. Aerobic bacteria that grows utilizingmethane for carbon and energy. The initial enzyme inthe pathway for aerobic degradation, methanemonooxygenase, has a broad substrate range and isactive against a wide range of compounds, including thechlorinated aliphatic trichloroethylene and 1,2-dichloroethane.

For degradation it is necessary that bacteria and thecontaminants be in contact. This is not easily achieved,as neither the microbes nor contaminants are uniformlyspread in the soil. Some bacteria are mobile and exhibita chemotactic response, sensing the contaminant andmoving toward it. Other microbes such as fungi grow ina filamentous form toward the contaminant. It ispossible to enhance the mobilization of the contaminantutilizing some surfactants such as sodium dodecylsulphate (SDS) (http://www.clu-in.org).

Different techniques are employed depending on thedegree of saturation and aeration of an area.

Ligninolytic fungi:

1.4 Bioremediation strategies

Phanaerochaetechrysosporium


In situ techniques

Ex situ techniques

Bioaugmentation techniques

1.6.1 Bioventing

are defined as those that are appliedto soil and groundwater at the site with minimaldisturbance.

are those that are applied to soiland groundwater at the site which has been removedfrom the site via excavation (soil) or pumping (water).

involve the addition ofmicroorganisms with the ability to degrade pollutants.

These techniques (U.S. EPA Seminars, 2001, U.S.EPA. Handbook 2002 ) are generally the most desirableoptions due to lower cost and less disturbance sincethey provide the treatment in place avoiding excavationand transport of contaminants. In situ treatment islimited by the depth of the soil that can be effectivelytreated. In many soils effective oxygen diffusion fordesirable rates of bioremediation extend to a range ofonly a few centimeters to about 30 cm into the soil,although depths of 60 cm and greater have beeneffectively treated in some cases.

is the most common in situ treatmentand involves supplying air and nutrients through wells tocontaminated soil to stimulate the indigenous bacteria.Bioventing employs low air flow rates and provides onlythe amount of oxygen necessary for the biodegradationwhile minimizing volatilization and release of

1.5 In situ bioremediation

1.6 The most important land treatments are:


Biotechnological Aspects OfPhytoremediation

Publisher : Anuradha Prakashan ISBN : 9789382339717 Author : Dr. Payal Mago

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