BIOREMEDIATION; A SOLUTION TO ENVIRONMENTAL HAZARDS

BIOREMEDIATION:

SOLUTION TO ENVIRONMENTAL HAZARDS

A SEMINAR PRESENTED

BY

IKECHUKWU CHUKWUEMEKA K.

INTERN MEDICAL LABORATORY SCIENTIST

DEPT. OF MEDICAL MICROBIOLOGY

NNAMDI AZIKIWE UNIVERSITY TEACHINGHOSPITAL, NNEWI.

7TH MARCH, 2012.

Bioremediation; solution to environmental hazards. Page 1

INTRODUCTION

“Environment” refers to the physical surroundings of man, ofwhich he is part, and on which he depends for his activities,like physiological functioning, production, and consumption(Bankole, 2008). His physical environment stretches from air,water and land to natural resources like metals, energycarriers, soil and plants, animals and ecosystems. A healthyenvironment is one that provides vital goods and services forthe existence of both man and other biotic organisms withinits ecosystem. The degree of sustainability of the physicalenvironment is an index of the survival and well being of theentire components in it (Onwurah et al, 2007).

Environmental hazard is a generic term for any situation orstate of events which poses a threat to the surroundingnatural environment and adversely affect people's health.Environmental hazards can be categorized in five types viz;chemical, physical, mechanical, biological, psychosocial(Vidali, 2001).

Waste products resulting from human life have always been aserious problem. Enormous quantities of organic and inorganiccompounds are released into the environment each year as aresult of human (anthropogenic) or natural activities. In somecases, these releases are deliberate and well regulated (e.g.,industrial emissions) while in other cases they are accidental(e.g., chemical or oil spills). Many of these compounds areboth toxic and persistent in terrestrial and aquaticenvironments. The contamination of soil, surface andgroundwater is simply the result of the accumulation of thesetoxic compounds in excess of permissible levels.


A lot of problems associated with conventional/traditionalphysical and chemical methods of pollutant treatment byincineration or landfills, has given the impetus on the needfor alternative, economical and reliable biological methods ofpollution treatments (Dua et al, 2002). These problems have ledto modern-day bioremediation which involves the use of livingorganisms or ecological processes to deal with a givenenvironmental problem. Although, this novel and recenttechnology is a multidisciplinary approach, its central thrustdepends on microbiology.

Given the challenges of population increase and its attendantproblems of pollution increase, biotechnology remains the mostreliable means of environmental sustenance. Africa generallyand Nigeria in particular have not imbibed maximally thebenefit of using bioremediation in maintenance of thebeautiful environment (Onwurah et al, 2007). This seminar aims toaddress the issues relating to the use of bioremediationmethods vis-à-vis bio-tools in solving the problems ofenvironmental degradation, with a view to encourage itsadoption in Nigeria, Africa and other countries where wastehas been a menace to the environments.

THE NIGERIAN ENVIRONMENT

Nigeria has one of the worst environmental records in theworld (Onwurah et al, 2007). In late 1995, Nigeria’s execution ofeight environmental activists, notable Nobel Peace Prizenominee Ken Saro Wiwa, made international headlines andbrought worldwide recognition of the serious environmentaldegradation of Nigeria. The problems of environmentaldegradation have continued to plague Nigeria and they havedefied proffered solutions mainly due to improper applicationsand also the lack of proper waste control and environmentalmaintenance.


The undesirably increased prevalence of toxic pollutant-induced disorders such as cancers, organ toxicity,neurotoxicity, behavioural disturbances and even death hasbeen linked to the neglected polluted environment that hasaccumulated over time.

The major causes of environmental degradation problems wereidentified by the vision 2010 committee set up by the FederalGovernment (Onwurah et al, 2007), and the following pollutantswere implicated in Nigerian environment:

Crude oil spills

Oil spills are a common event in Nigeria and occur due toa number of causes, including: corrosion of pipelines andtankers (accounting for 50% of all spills), sabotage(28%), and oil production operations (21%), with 1% ofthe spills being accounted for by inadequate or non-functional production equipment (Okpokwasili, 2007). Mostof these spills occurred off-shore (69%), a quarter wasin swamps and 6% spilled on land. In the early 2000s, itseemed more spills were due to sabotage than by accidents(Okpokwasili, 2007).

Solid waste

The Nigerian cities such as Aba, Enugu, Onitsha, Kano,Ibadan, and Lagos are characterised by huge mounds ofsolid waste dumps generated from households, industries,markets, schools and street trading. This can beattributed to migration, population increase,urbanization, constructions and industrialization coupledwith inefficient, improper and sometimes non disposal ofwastes. Solid waste dumps are indiscriminately formed onstreets, homes, road side, markets and other places wherehuman activities take place in the cities. Solid waste isdivided into biodegradables and non-biodegradables.


http://en.wikipedia.org/wiki/Pipeline_transport

http://en.wikipedia.org/wiki/Oil_spill

The Biodegradables (Biowastes)

These include those solid wastes generated, which couldbe decomposed by micro-organisms and does not constitutemajor sources of pollution for a long period of time.They include; paper products (such as printing papers,waste books, newspapers, carton, toilet paper, cardboards etc) wastes of plant origin (fruits, stems,roots, vegetables, leaves, food remains and garden solidwastes etc), wastes of animal origin (faecal matter,carcass, droppings and poultry waste products). Thesegroups of solid waste even though they are easilydegraded by micro-organism in minimal time, give offoffensive odour and constitute nuisance to the aestheticenvironment more than the non-biodegradable solid wastes.They can also constitute a good habitat for the thrivingof pathogenic micro organisms which could easily pollutefresh food product and sources of fresh water in theurban cities in Nigeria (Onwurah et al, 2007).

Non-Biodegradable (Rubbish/Garbage)

These groups of solid wastes are not degradable or hardlydegraded by micro organisms. Hence, other means oftreatment such as incineration, land refill, andrecycling are currently employed in Nigeria as ways ofdisposing them (Onwurah et al, 2007). Examples of this groupof solid wastes are: solid wastes of metallurgical andsmelting industries(abandoned vehicles, motor cycles,vehicle part and scrap metals, iron, zinc, aluminiumsheets and other metals, machine parts); solid wastes ofconstruction industries (sand, gravel, bitumen wastes,concrete and waste building materials); solid waste ofplastic industries (plastic buckets, cable insulators,tyres, chairs, tables, cellophane bags, plastic bottles,cutleries, sachet water containments etc) and glassproducts. These might not give out offensive odour but


they are even worse nuisance to the environment sincetheir disposal has become a ‘Herculean’ and nearimpossible task in Nigeria.

Toxic heavy metals

Municipal waste contains such heavy metals as As, Cd, Co,Cu, Fe, Hg, Mn, Pb, Ni, and Zn which end up in the soilwhen they are leached out from the dump sites(Okpokwasili, 2007). However, no consistent miningregulatory law is enforced in the country. Naturallyoccurring radioactive and heavy metals can be found inthe soil and water used for domestic purposes aftermining activities. Nigerian environmentalists have agreedthat mining activities such as tin (Jos), Coal (Enugu)and others has done great damages to the environmentwhich will need a concerted effort especially adoption ofbetter mining practices in order to remediate.

Chlorinated solvents (such as; trichloroethylene,perchloroethylene) generated by drycleaners and chemicalmanufacturing industries.

Pesticides and agricultural chemicals (such as atrazine,parathion, glycophosphate, propham) resulting from timbertreatment plants, landfills, pesticide manufacture,recreational areas and agricultural activities.

Wood processing contaminants (such as pentachlorophenol)generated by timber treatment and landfills.

Radioactive metals such as uranium (U), strontium (Sr),plutonium (Pu), cesium (Cs) and technetium (Te).

BTEX chemicals (benzene, tuolene, ethylbenzene, xylene)resulting from oil production and storage, gas worksites, paint and chemical manufacture and portfacilities.


BIOREMEDIATION

Bioremediation is the use of living organisms (especiallymicroorganisms) under controlled conditions to transform ordegrade environmental pollutants into non-hazardous or lesshazardous products (Vallero, 2010). Bacteria are generallyused for bioremediation, but fungi, algae, actinomycetes andplants have also been used. Thus, the goal of bioremediationis the employment of bio-systems such as microbes, higherorganisms like plants (phytoremediation) and animals to reducethe potential toxicity of chemical contaminants in theenvironment by degrading, transforming and immobilizing theseundesirable compounds. Microorganisms used to perform thefunction of bioremediation are known as bioremediators(Vidali, 2001).

Bioremediation is not a new technology. There has beenevidence that compost piles existed as far back as 6000 BC,and in 1891 the first biological sewage treatment plant wascreated in Sussex, UK. However, the word “bioremediation” didnot appear in peer-reviewed scientific literature until 1987(Vidali, 2001).

PRINCIPLES OF BIOREMEDIATION

Living organisms need the right combination of temperature,nutrients and oxygen to grow and multiply. Many microorganismscan adapt their catabolic machinery to utilize certainenvironmental pollutants as growth substrates and as the solesource of energy and carbon, thereby bioremediating theenvironment. Some microorganisms in carrying out their normalmetabolic function may fortuitously degrade certain pollutantsas well. This process termed cometabolism obviously requiresadequate growth substrates. The environmental and nutritional


http://en.wikipedia.org/wiki/Microorganism

conditions of polluted lands, surface and ground water can beadequately controlled to enhance the growth of both indigenousand inoculated organisms ultimately resulting in a cleaner,safer and economically better environment (Tang et al, 2007).

These organisms either enzymatically eat up the pollutants orassimilate within them all harmful compounds from thesurrounding area, thereby, rendering the region virtuallypollutant-free. Generally, the substances that areenzymatically eaten up are organic compounds, while those,which are assimilated within the organism, are the inorganicheavy metals.

The pollutants can undergo any of the following detoxifyingprocesses (Vidali, 2001):

Biotransformation: the alteration of contaminantmolecules into less or non-hazardous molecules.

Biodegradation: the breakdown of toxic organic substancesinto less toxic smaller organic or inorganic molecules.

Mineralization: is the complete biodegradation of organicmaterials into harmless inorganic constituents such as CO2

or H2O.

Biosorption: is the binding of the contaminant moleculesto cell surface structures of microorganisms and plantroots.

According to Dua et al (2002), bioremediation can be achievedusing two approaches viz:

Bioaugmentation: means introduction of specific blends oflaboratory-cultivated microorganisms that can biotransform orbiodegrade contaminants into a contaminated environment orinto a bioreactor to initiate the bioremediation process. Themicroorganisms added can be a completely new species or moremembers of a species that already exists at the site.


Genetically engineered microbes and plants (GEM) that areresistant to the extreme conditions of the contaminated siteand also have bioremediary properties have been developed fordiverse pollutants and polluted sites.

Biostimulation: provides nutrients and suitable physiologicalconditions (oxygen or other electron donors and acceptors) forthe growth of the indigenous microbial populations. Thispromotes increased metabolic activity, which then degrades thecontaminants.

Life-chemical Dynamics (Biochemodynamics) of Bioremediation

The control and optimization of bioremediation processes is acomplex system of many factors (Vidali, 2001). These factorsinclude:

The existence of a microbial population capable ofdegrading the pollutants

The availability of contaminants to the microbialpopulation

The environmental factors (type of soil, temperature, pH,the presence of oxygen or other electron acceptors, soilmoisture and nutrients).

BIOREMEDIATION TECHNOLOGIES

Bioremediation technologies can be generally classified as insitu or ex situ. In situ bioremediation involves treating thecontaminated material at the site, while ex situ involves theremoval of the contaminated material to be treated in acontained environment elsewhere. According to Dua et al (2002),the selection of appropriate technology among the wide rangeBioremediation; solution to environmental hazards. Page 9

http://en.wikipedia.org/wiki/Ex_situ

http://en.wikipedia.org/wiki/In_situ

http://en.wikipedia.org/wiki/In_situ

of bioremediation technologies developed to treat contaminantsdepends on three basic principles viz;

The amenability of the pollutant to biologicaltransformation (Biochemistry)

The accessibility of the contaminant to microorganisms(Bioavailability)

The opportunity for optimization of biological activity(Bioactivity)

In-Situ technologies

Biosparging

Biosparging involves the injection of air under pressure belowthe water table to increase groundwater oxygen concentrationsand enhance the rate of biological degradation of contaminantsby naturally occurring bacteria. Biosparging increases themixing in the saturated zone and thereby increases the contactbetween soil and groundwater (Keshav et al, 2010). The ease andlow cost of installing small-diameter air injection pointsallows considerable flexibility in the design and constructionof the system.

Bioventing

Bioventing is the most common in situ treatment and involvessupplying air and nutrients through wells to contaminated soilto stimulate the indigenous bacteria. Bioventing employs lowair flow rates and provides only the amount of oxygennecessary for the biodegradation while minimizingvolatilization and release of contaminants to the atmosphere.It works for simple hydrocarbons and can be used where thecontamination is deep under the surface. A basic bioventingsystem includes a well and a blower, which pumps air throughthe well and into the soil (Lee et al, 2006).


Bioaugmentation

Bioremediation frequently involves the addition ofmicroorganisms indigenous or exogenous to the contaminatedsites. Two factors limit the use of added microbial culturesin a land treatment unit viz:

Nonindigenous cultures rarely compete well enough with anindigenous population to develop and sustain usefulpopulation levels.

Most soils with long-term exposure to biodegradable wastehave indigenous microorganisms that are effective anddegrade wastes if the land treatment unit is wellmanaged.

Phytoremediation

Plant-assisted bioremediation, or phytoremediation, iscommonly defined as the use of green or higher terrestrialplants for treating chemically or radioactively polluted soils(Keshav et al, 2010). Genetically engineered (transgenic) andnaturally occurring plants have been used for thephytoremediation of a wide variety of toxic contaminantsincluding polycyclic aromatic hydrocarbons, trichloroethylene,vinyl chloride, carbon tetrachloride, chloroform, benzene andherbicides (Hiroyuki, 2009).

Phytoremediation strategies include the following;

Phytoextraction

Phytoextraction (or phytoaccumulation) uses plants or algae toremove contaminants from soils, sediments or water intoharvestable plant biomass. Phytoextraction has been growingrapidly in popularity worldwide for the last twenty years orso (Cecile et al, 2007). Generally, this process has been triedmore often for extracting heavy metals than for organics.


The plants absorb contaminants through the root system andstore them in the root biomass and/or transport them up intothe stems and/or leaves. A living plant may continue to absorbcontaminants until it is harvested. After harvest, a lowerlevel of the contaminant will remain in the soil, so thegrowth/harvest cycle must usually be repeated through severalcrops to achieve a significant cleanup. After the process, thecleaned soil can support other vegetation.

Phytotransformation

In the case of organic pollutants, such as pesticides,explosives, solvents, industrial chemicals, and otherxenobiotic substances, certain plants, such as canas, renderthese substances non-toxic by their metabolism. In othercases, microorganisms living in association with plant rootsmay metabolize these substances in soil or water. Thesecomplex and recalcitrant compounds cannot be broken down tobasic molecules (water, carbon dioxide etc) by plantmolecules, and hence the term phytotransformation represents achange in chemical structure without complete breakdown of thecompound (Hiroyuki, 2009).

Rhizofiltration

Rhizofiltration is similar in concept to phytoextraction butis concerned with the remediation of contaminated groundwaterrather than the remediation of polluted soils. Thecontaminants are either adsorbed onto the root surface or areabsorbed by the plant roots. Plants used for rhizofiltrationare not planted directly in situ but are acclimated to thepollutant first. Plants are hydroponically grown in cleanwater rather than soil, until a large root system hasdeveloped. Once a large root system is in place, the watersupply is substituted for a polluted water supply toacclimatize the plant. After the plants become acclimatizedthey are planted in the polluted area where the roots uptake


the polluted water and the contaminants along with it. As theroots become saturated, they are harvested and disposed ofsafely. Repeated treatments of the site can reduce pollutionto suitable levels as was exemplified in sunflowers were grownin radioactively contaminated pools (Marcia et al, 1995).

Phytostabilisation

Phytostabilisation is the use of certain plants to immobilizesoil and water contaminants. Contaminant are absorbed andaccumulated by roots, adsorbed onto the roots, or precipitatedin the rhizosphere. This reduces or even prevents the mobilityof the contaminants preventing migration into the groundwateror air, and reduces the bioavailability of the contaminantthus preventing spread through the food chain (Meagher, 2000).

Phytodegradation

Phytodegradation is the degradation or breakdown of organiccontaminants by internal and external metabolic processesdriven by the plant. Ex-planta metabolic processes hydrolyseorganic compounds into smaller units that can be absorbed bythe plant. Some contaminants can be absorbed by the plant andare then broken down by plant enzymes. These smaller pollutantmolecules may then be used as metabolites by the plant as itgrows, thus becoming incorporated into the plant tissues.Plant enzymes have been identified that breakdown ammunitionwastes, chlorinated solvents such as TCE (Trichloroethane),and others that degrade organic herbicides (Singh and Jain,2003).

Rhizodegradation

Rhizodegradation (also called enhanced rhizospherebiodegradation, phytostimulation, and plant assistedbioremediation) is the breakdown of organic contaminants inthe soil by soil dwelling microbes which is enhanced by therhizosphere's (highly complex symbiotic and synergistic


relationships) presence. Rhizodegradation is a symbioticrelationship that has evolved between plants and microbes.Plants provide nutrients necessary for the microbes to thrive,while microbes provide a healthier soil environment (Kudjo,2007).

Phytovolatilization

Phytovolatilization involves plant uptake of contaminants thatare water-soluble and release them into the atmosphere as theytranspire the water. The contaminant may become modified alongthe way, as the water travels along the plant's vascularsystem from the roots to the leaves, whereby the contaminantsevaporate or volatilize into the air surrounding the plant(Danika, 2005).

Ex-Situ technologies (Dua et al, 2002)

Land farming (Solid-phase treatment system)

Landfarming is a simple technique in which contaminated soilis excavated and spread over a prepared bed and periodicallytilled until pollutants are degraded. The goal is to stimulateindigenous biodegradative microorganisms and facilitate theiraerobic degradation of contaminants. In general, the practiceis limited to the treatment of superficial 10–35 cm of soil.Since landfarming has the potential to reduce monitoring andmaintenance costs, as well as clean-up liabilities, it hasreceived much attention as a disposal alternative.

Composting

Composting is a process by which organic wastes are degradedby microorganisms, typically at elevated temperatures intohumus-like material (Blanca et al, 2008).

Composting is a technique that involves combining contaminatedsoil with nonhazardous organic amendants such as manure or


agricultural wastes. The presence of these organic materialssupports the development of a rich microbial population andelevated temperature characteristic of composting.

Biopiles

Biopile treatment is a hybrid of landfarming and compostingand involves a full-scale technology in which excavated soilsare mixed with soil amendments, placed on a treatment area,and bioremediated using forced aeration. The contaminants arereduced to carbon dioxide and water.

The basic biopile system includes a treatment bed, an aerationsystem, an irrigation/nutrient system and a leachatecollection system. Moisture, heat, nutrients, oxygen, and pHare controlled to enhance biodegradation. Theirrigation/nutrient system is buried under the soil to passair and nutrients either by vacuum or positive pressure.Treatment time is typically 3 to 6 months (Wu and Crapper,2009).

Bioreactors

Slurry reactors or aqueous reactors are used for ex situtreatment of contaminated soil and water pumped up from acontaminated plume. Bioremediation in reactors involves theprocessing of contaminated solid material (soil, sediment,sludge) or water through an engineered containment system. Aslurry bioreactor may be defined as a containment vessel andapparatus used to create a three-phase (solid, liquid, andgas) mixing condition to increase the bioremediation rate ofsoil-bound and water-soluble pollutants. In general, the rateand extent of biodegradation are greater in a bioreactorsystem than in situ or in solid-phase systems because thecontained environment is more manageable and hence morecontrollable and predictable. Despite the advantages ofreactor systems, there are some disadvantages. Thecontaminated soil requires pre treatment (e.g., excavation) or


alternatively the contaminant can be stripped from the soilvia soil washing or physical extraction (e.g., vacuumextraction) before being placed in a bioreactor.

BIOREMEDIATORS AND PLANTS USED FOR BIOREMEDIATION

Environmentalcontaminants

Bioremediators Phytoremediators

Oil Spills(Polyaromatichydrocarbons)

Azotobacter vinelandii,Rhodococcus spp.,Pseudomonas spp., Rhizobiumgalegae, Sphingomonasyanokuyae, Soil microflora

Alfalfa, Prairie grasses, Betulpendula, Galega orientalis,Lolium percurie

Chlorinatedsolvents

Dehalococcoides ethenogenes,Pseudomonas fluorescens.

Mixture of grasses,legumes, herbs andpines.

Pesticides andagriculturalchemicals

Rhizobium spp. Poplar, Corbicula fluminea,Rice (cv. Upriya)

Woodprocessingchemicals

Rhizobium spp. Astragalus chrysopteru

Toxic heavymetals

Deinococcus radiodurans,Geobacter sufurreducens,Micrococcus luteus,

Trangenie Arabidopsis,Indian mustard, Chineseladder ferns, cottonwood,


Azotobacter spp., Klebsiellaaerogenes, Streptomycesalbus, Bacillus spp.,Citrobacter spp., Arthrobacter,Serratia spp., Pseudomonasaeruginosa, Chlorella vulgaris.

sunflower, soybean, ragweed,Salix caprea.

Radioactivemetals

Deinococcus radiodurans,Geobacter metallireducens.

Sunflower

BTEX chemicals Arthrobacter spp., Bacillusspp., Pseudomonasboreopolis, Alcaligenesfaecalis.

Paspalum vaginatum, Galegaorientalis, Zoysia tenuifolia.

(SOURCE: Keshav et al, 2010)

COMPARATIVE ADVANTAGES AND DISADVANTAGES OF BIOREMEDIATION(Vidali, 2001)

ADVANTAGES

Works on a variety of organic and inorganic compounds

Can be done either on-site or off-site

Easy to implement and maintain

Low-cost compared to other treatment methods

Environmentally-friendly and aesthetically pleasing

Reduces the amount of wastes to be landfilled

It uses naturally occurring organisms and preserves thenatural state of the environment.

DISADVANTAGES


May take several years to remediate

May depend on climatic conditions

Restricted to sites with contamination near the roots ofplants

Harvested plants may be classified as hazardous waste

Consumption of contaminated plants may be harmful

MONITORING BIOREMEDIATION

The process of bioremediation can be monitored indirectly bymeasuring the Oxidation Reduction Potential or redox in soil andgroundwater, together with pH, temperature, oxygen content,electron acceptor/donor concentrations, and concentration ofbreakdown products (e.g. carbon dioxide). It is necessary tosample enough points on and around the contaminated site to beable to determine contours of equal redox potential. If allthe measurements of redox potential show that electronacceptors have been used up, it is in effect an indicator fortotal microbial activity (Vidali, 2001).

Chemical analysis and toxicity testing is also required todetermine when the levels of contaminants and their breakdownproducts have been reduced to below regulatory limits (Vidali,2001).

CONCLUSION

The Nigerian environment is greatly threatened by diversehighly toxic and hazardous pollutants generated by humanactivities. These environmental hazards have resulted in grossdegradation and contamination of soil, air, surface and groundwater leading to economic, social, agricultural and healthdamages. Recent advances in the field of environmentalbiotechnology which harnesses bio-tools such as genetic and


http://en.wiktionary.org/wiki/indicator

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http://en.wikipedia.org/wiki/Carbon_dioxide

http://en.wikipedia.org/wiki/Oxygen

http://en.wikipedia.org/wiki/PH

http://en.wikipedia.org/wiki/Soil

http://en.wikipedia.org/wiki/Redox

molecular engineering has led to the improved development ofhighly effective, eco-friendly and low-cost bioremediationtechnologies. The medical laboratory scientist has a crucial roleto play in the research, development, implementation andmonitoring of bioremediation technologies in order to ensure aclean, safe, healthy, fertile, sustainable and economically-viable environment.


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Cécile S., Gwenola G., Françoise B., Fabrice M., Abdelhak E.,Ivan C. (2007): Sucrose amendment enhancesphytoaccumulation of the herbicide atrazine inArabidopsis thaliana. Environmental Pollution. 145: 507-515.

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BIOREMEDIATION; A SOLUTION TO ENVIRONMENTAL HAZARDS