In this essay we will discuss about Environmental Biotechnology. After reading this essay you will learn about: 1. Introduction to Environmental Biotechnology 2. Key Points of Environment Biotechnology 3. Bioremediation 4. Microbes and Plants in Environmental Remediation 5. Solid Waste Bio-Treatment 6. Biodegradation of Hydrocarbons 7. Biodegradation of Refractory Pollutants and Waste and Other Details.

Contents:

  1. Essay on the Introduction to Environmental Biotechnology
  2. Essay on the Key Points of Environmental Biotechnology
  3. Essay on Bioremediation
  4. Essay on the Microbes and Plants in Environmental Remediation
  5. Essay on the Solid Waste Bio-Treatment
  6. Essay on the Biodegradation of Hydrocarbons
  7. Essay on the Biodegradation of Refractory Pollutants and Waste
  8. Essay on Environmental Biotechnology in Pollution Detecting and Monitoring
  9. Essay on Environmental Biotechnology for Pollution Prevention and Cleaner Production
  10. Essay on Environmental Biotechnology Challenges and Perspectives

Essay # 1. Introduction to Environmental Biotechnology:

The most important topics at the threshold of the 21st century are the environment and bio­technology. Environmental biotechnology can be defined as the marriage of environmental issues with the advances in biotechnology.

It is concerned with the application of biotech­nology as an emerging technology in the con­text of environmental protection, since rapid industrialization, urbanization and other de­velopments have resulted in a threatened clean environment and depleted natural resources.

It is not a new area of interest, because some of the issues of concern are familiar examples of “old” technologies, such as: composting, wastewater treatment, etc. In its early stage, environmental biotechnology has evolved from chemical engineering, but later, other disci­plines (biochemistry, environmental engineer­ing, environmental microbiology, molecular biology, ecology) also contribute to environ­mental biotechnology development. The development of multiple human activities in the sector of industry, transport, agriculture, do­mestic space, etc. have amplified the pollution of air, water and soil.

Studies and researches demonstrated that some of these pollutants can be readily degraded or removed by means of biotechnological solutions.

Advanced techniques are available to treat waste and degrade pollutants assisted by liv­ing organisms or to develop products and pro­cesses that generate less waste and preserve the natural non-renewable resources and en­ergy as a result of the followings:

1. Improved treatments for solid waste and wastewater

2. Bioremediation: cleaning up contamination and phytoremediation

3. Ensuring the health of the environment through bio monitoring

4. Cleaner production: manufacturing with less pollution or less raw materials

5. Energy from biomass

6. Genetic engineering for environmental pro­tection and control.

Essay # 2. Key Points of Environment Biotechnology:

At least three key points are considered for environmental biotechnology. These are as fol­lows:

1. To detect the pollution and any other en­vironmental changes by means of biosensors and bio monitoring.

2. To prevent the unfavorable environmen­tal changes in the manufacturing process by substitution of traditional processes.

3. To control and remediate the emission of pollutants into the environment.

By considering all these issues, biotechnol­ogy may be regarded as a driving force for in­tegrated environmental protection by environ­mental bioremediation, waste minimization, environmental bio monitoring, bio maintenance.

Essay # 3. Bioremediation:

Environmental hazards and risks that occur as a result of accumulated toxic chemicals or other waste and pollutants could be reduced or eliminated through the application of bio­technology in the form of bioremediation. Bioremediation methods are almost typical processes which are applied to remove, de­grade, or detoxify pollution in environmental media, including water, air, soil, and solid waste.

Four processes can be considered as acting on the contaminant:

1. Removal:

A process that physically re­moves the contaminant or contaminated medium from the site without the need for separation from the host medium.

2. Separation:

A process that removes the contaminant from the host medium (soil or water).

3. Degradation:

A process that chemically or biologically destroys or neutralizes the contaminant to produce less toxic com­pounds.

4. Immobilization:

A process that impedes or immobilizes the surface and subsurface migration of the contaminant.

Removal, separation, and destruction are processes that reduce the concentration or remove the contaminant. Containment,on the other hand, controls the migration of a contaminant to sensitive receptors without reduc­ing or removing the contaminant.

Removal of any pollutant from the environment can take place on following two routes: degradation and immobilization by a process which causes it to be biologically unavailable for degradation and so is effectively removed.

Immobilization can be carried out by chemicals released by organ­isms or added in the adjoining environment, which catch or chelate the contaminant, mak­ing it insoluble, thus unavailable in the envi­ronment as an entity.

Sometimes, immobili­zation can be a major problem in remediation because it can lead to aged contamination and a lot of research effort needs to be applied to find methods to turn over the process.

Destruc­tion (biodegradation and biotransformation) is carried out by an organism or a combination of organisms (consortia) and is the core of en­vironmental biotechnology, since it forms the major part of applied processes for environ­mental clean-up. Biotransformation processes use natural and recombinant microorganisms (yeasts, fungi, bacteria), enzymes, whole cells.

Biotransformation plays a key role in the area of foodstuff, pharmaceutical industry, vita­mins, specialty chemicals, animal feed stock. Metabolic pathways operate within the cells or by enzymes either provided by the cell or added to the system after they are isolated and often immobilized.

Biological processes rely on useful microbial reactions including degrada­tion and detoxification of hazardous organics, inorganic nutrients, metal transformations, applied to gaseous, aqueous and solid waste.

A complete biodegradation results in detoxification by mineralizing pollutants to carbon dioxide, water and harmless inorganic salts. Incomplete biodegradation will yield breakdown products which may or may not be less toxic than the original pollutant and com­bined alternatives have to be considered, such as: dispersion, dilution, bio sorption, volatiliza­tion and the chemical or biochemical stabili­zation of contaminants.

In addition, bio augmentation involves the deliberate addi­tion of microorganisms that have been cul­tured, adapted, and enhanced for specific con­taminants and conditions at the site. Bio refining entails the use of microbes in min­eral processing systems.

It is an environment-friendly process and, in some cases, enables the recovery of minerals and use of resources that otherwise would not be possible. Current research on bioleaching of oxide and sulfide ores addresses the treatment of manganese, nickel, cobalt, and precious metal ores.

Biological treatment processes are com­monly applied to contaminants that can be used by organisms as carbon or energy sources, but also for some refractory pollutants, such as:

1. Organics (petroleum products and other carbon-based chemicals),

2. Metals (arsenic, cadmium, chromium, cop­per, lead, mercury, nickel, zinc), and

3. Radioactive materials.

Essay # 4. Microbes and Plants in Environmental Remediation:

All forms of life can be considered as having a potential function in environmental biotech­nology. However, microbes and certain plants are of interest even as normally present in their natural environment or by deliberate introduction. The generic term “microbe” in­cludes prokaryotes (bacteria or arcaea) and eukaryotes (yeasts, fungi, protozoa, and uni­cellular plants, rotifers).

Some of these organ­isms have the ability to degrade most of the hazardous and recalcitrant chemicals, since they have been discovered in unfriendly envi­ronments where the needs for survival affect their structure and metabolic capability.

Mi­croorganisms may live as free individuals or as communities in mixed cultures (consortia), which are of particular interest in many re­levant environmental technologies, like acti­vated sludge or biofilm in wastewater treat­ment.

One of the most significant key aspects in the design of biological wastewater treat­ment systems is the microbial community structures in activated sludge’s, constituted from activated sludge floes, which enclose vari­ous microorganism types.

The role of plants in environmental clean-up is exerted during the oxygenation of a microbe-rich environment, filtration, solid-to­gas conversion or extraction of contaminants. The use of organisms for the removal of con­tamination is based on the concept that all or­ganisms could remove substances from the environment for their own growth and metabo­lism.  

1. Bacteria and fungi are very good at degrad­ing complex molecules, and the resultant wastes are generally safe,

2. Protozoa, and

3. Algae and plants proved to be suitable to absorb nitrogen, phosphorus, sulphur, and many minerals and metals from the envi­ronments.

Micro-organisms used in bioremediation include aerobic (which use free oxygen) and anaerobic. Some have been isolated, selected, mutated and genetically engineered for effec­tive bioremediation capabilities, including the ability to degrade recalcitrant pollutants, gua­rantee better survival and colonization and achieve enhanced rates of degradation in tar­get polluted niches.

They are functional in ac­tivated sludge processes, lagoons and ponds, wetlands, anaerobic wastewater treatment and digestion, bioleaching, phytoremediation, land-farming, slurry reactors, trickling filters.

Factors Affecting Bioremediation:

Two groups of factors can be identified that determine the success of bioremediation pro­cesses:

1. Nature and character of contaminant, which refers to the chemical nature of con­taminants and their physical state.

2. Environmental conditions:

This includes the temperature, pH, water/air/soil char­acteristics, presence of toxic or inhibiting substances to the microorganism, sources of energy, sources of carbon, nitrogen, trace compounds, temperature, pH, moisture content.

Also, bioremediation tends to rely on the natural abilities of microorganisms to develop their metabolism and to optimize enzymes ac­tivity. The prime controlling factors are air (oxygen) availability, moisture content, nutrient levels, matrix pH, and ambient tempera­ture.

Usually, for ensuring the greatest effi­ciency, the ideal range of temperature is 20- 30°C, a pH of 6.5-7.5 or 5.9-9.0 (dependent on the microbial species involved). Other circum­stances, such as nutrient availability, oxygen­ation and the presence of other inhibitory con­taminants are of great importance for bioremediation suitability, for a certain type of contaminant and environmental compart­ment, the required remediation targets and the availability of required time.

The selection of a certain remediation method entails non-en­gineered solutions (natural attenuation/intrin­sic remediation) or an engineered one, based on a good initial survey and risk assessment.

A number of interconnected factors affect this choice:

1. Contaminant concentration

2. Contaminant characteristics and type

3. Scale and extent of contamination

4. The risk level posed to human health or environment

5. The possibility to be applied in situ or ex situ

6. The subsequent use of the site

7. Available resources.

Bioremediation technologies offer a num­ber of advantages even when bioremediation processes have been established for both in situ and ex situ treatment, such as:

1. Operational cost savings comparative to other technologies

2. Minimal site disturbance

3. Low capital costs

4. Destruction of pollutants, and not trans­ferring the problem elsewhere

5. Exploitation of interactions with other technologies.

These advantages are counterbalanced by some dis-remediation targets and how much time is available. The selection of a certain remediation method entails non-engineered solutions (natural attenuation/intrinsic remediation) or an engineered one, based on a good initial survey and risk assessment.

A number of interconnected factors affect this choice:

a. Contaminant concentration

b. Contaminant characteristics and type

c. Scale and extent of contamination

d. The risk level posed to human health or environment

e. The possibility to be applied in situ or ex situ

f. The subsequent use of the site

g. Available resources.

Bioremediation technologies offer a num­ber of advantages even when bioremediation processes have been established for both in situ and ex situ treatment, such as:

a. Operational cost savings comparative to other technologies

b. Minimal site disturbance

c. Low capital costs

d. Destruction of pollutants, and not trans­ferring the problem elsewhere

e. Exploitation of interactions with other technologies.

These advantages are counterbalanced by some disadvantages:

a. Influence of pollutant characteristics and local conditions on process implementation

b. Viability needs to be improved (time con­suming and expensive)

c. Community distress for safety of large-scale on-site treatment

d. Other technologies should be necessary

e. May have long time-scale.

Waste Water Bio-Treatment:

The use of microorganisms to remove contami­nants from waste water is largely dependent on wastewater source and characteristics.

Waste water is typically categorized into one of the following groups:

a. Municipal waste water (domestic waste water mixed with effluents from commer­cial and industrial works, pre-treated or not pre-treated),

b. Commercial and industrial waste water (pre-treated or not pre-treated), and

c. Agricultural waste waters.

The effluent components may be of chemi­cal, Cal physical or biological nature and they can induce an environmental impact, which in­cludes changes in aquatic habitats and spe­cies structure as well as in biodiversity and water quality.

It is evident that the quality parameters are very diverse, so that the bio­logical waste water treatment has to be ad­equate to pollution loading. Therefore, it is a difficult task to find the most appropriate mi­croorganism consortia and treatment scheme for a certain type of waste water, in order to remove the non-settle-able colloidal solids and to degrade specific pollutants such as organic, nitrogen and phosphorus compounds, heavy metals and chlorinated compounds contained in waste water. Since many of these com­pounds are toxic to microorganisms, pre-treatment may be required.

Biological treatment requires that the ef­fluents be rich in unstable organic matter, so that microbes break up these unstable organic pollutants into stable products like CO2, CO, NH3, CH4, H2S, etc.

To an increasing extent, waste water treat­ment plants have changed from “end-of-pipe” units toward module systems, most of them fully integrated into the production process.

The three major groups of biological pro­cesses: aerobic, anaerobic, combination of aero­bic and anaerobic can be run in combination or in sequence to offer greater levels of treat­ment.

The main objectives of waste water treatment processes can be summarized as:

a. Reduction of biodegradable organics con­tent (BOD5)

b. Reduction of recalcitrant organics

c. Removal of heavy/toxic metals

d. Removal of compounds containing p and n (nutrients)

e. Removal and inactivation of pathogenic microorganisms and parasites

1. Aerobic Bio-Treatment:

Aerobic processes are often used for munici­pal and industrial waste water treatment.

Easily biodegradable organic matter can be treated by this system.

The basic reaction in aerobic treatment plant is represented by the reactions (1, 2):

Microbial cells undergo progressive auto- oxidation of the cell mass:

Cells + O2 → CO2 + H2O + NH3 (2)

Lagoons and low rate biological filters have only limited industrial applications. The pro­cesses can be exploited as suspended (activate sludge) or attached growth (fixed film) sys­tems.

Aeration tanks used for the activated sludge process allows suspended growth of bacterial biomass to occur during biological (secondary) waste water treatment, while trickling filters support attached growth of bio- mass.

Advanced types of activated sludge sys­tems use pure oxygen instead of air and can operate at higher biomass concentration. Biofilm reactors are applied for waste water treatment in variants such as: trickle filters, rotating disk reactors, air-lift reactors.

Domes­tic waste waters are usually treated by aero­bic activated sludge process, since they are composed mainly of proteins (40-60%), carbohydrates (25-50%), fats and oils (10%), urea, a large number of trace refractory organics (pes­ticides, surfactants, phenols).

2. Anaerobic Bio-Treatment:

Anaerobic treatment of wastewater does not generally lead to low pollution standards, and it is often considered a pre-treatment process, devoted to minimization of oxygen demand and excessive formation of sludge.

Highly concen­trated wastewaters should be treated anaerobically due to the possibility to recover energy as biogas and low quantity of sludge. Research and practices have demonstrated that high loads of waste water treated by anaerobic tech­nologies generates low quantities of biological excess sludge with a high treatment efficiency, low capital costs, no oxygen requirements, methane production, low nutrient require­ments.

3. Advanced Bio-Treatment:

Advanced waste water bio-treatment must be considered in accordance with various benefi­cial reuse purposes as well as the aspect of human and environmental health. This is es­pecially important when the treated wastewa­ter is aimed to use for the rehabilitation of urban creak and creation of water environment along it.

Membrane technology is considered one of the innovative and advanced technolo­gies which rationally and effectively satisfy the above mentioned needs in water and waste water treatment and reuse, since it combines biological with physical processes.

In combi­nation with biological treatment, it is reason­ably applied to organic waste waters, a large part of which is biodegradable. In fact, this is the combination of a membrane process like microfiltration or ultrafiltration with a sus­pended growth bioreactor.

It is widely and successfully applied in an ever increasing number of locations around the world for municipal and industrial waste wa­ter treatment with plant sizes up to 80,000 population equivalent (Membrane Separation Activated Sludge Process, MSAS). The process efficiency is dependent on several factors, such as membrane characteristics, sludge charac­teristics, operating conditions.

A new genera­tion of MSAS is the submerged type where membrane modules are directly immersed in an aeration tank. This aims to significantly reduce the energy consumption by eliminat­ing a big circulation pump typically installed in a conventional MSAS.

Membrane bioreactors (MBR) can be applied for removal of dissolved organic substances with low mo­lecular weights, which cannot be eliminated by membrane separation alone, can be taken up, broken down and gasified by microorgan­isms or converted into polymers as constitu­ents of bacterial cells, thereby raising the qual­ity of treated water.

Also, polymeric substances retained by the membranes can be broken down if they are still biodegradable, which means that there will be no endless accumu­lation of the substances within the treatment process. This, however, requires the balance between the production and degradation rates, because the accumulation of intermediate metabolites may decrease the microbial activi­ties in the reactor.

MBRs can be operated aerobically or anaerobically for organic compounds and nu­trients removal. Due to its hybrid nature, MBRs offer advantages and gain merits.

The main advantages of biological processes in comparison with chemical oxidation are:

a. No need to separate colloids and dispersed solid particles before treatment.

b. Lower energy consumption, the use of open reactors, resulting in lower costs.

c. No need for waste gas treatment.

4. Molecular Techniques in Waste Water Treatment:

Although molecular technique applications in waste water bio-treatment are quite new, be­ing developed during the 1990s and not ap­pearing to be more economical than the estab­lished technologies, major applications may include the enhancement of xenobiotics re­moval in wastewater treatment plants and the use of nucleic acid probes to detect pathogens and parasites.

Among these techniques, clon­ing and creation of gene library, denaturant gradient cell electrophoresis (DGGE), fluores­cent in situ hybridization with DNA probes (FISH) were proved to be most interesting. Waste water treatment, processes can be im­proved by selection of novel microorganisms in order to perform a certain action.

However, the use of DNA technology in pollution control showed to have some disadvantages and limi­tations such as:

a. Multistep pathways in xenobiotics biodeg­radation

b. Limited degradation, instability of the re­combinant strains of interest in the en­vironment, public concern about deliber­ate or accidental release of genetic modi­fied microorganisms, etc.

5. Metals Removal by Microorganisms from Waste Waters:

Heavy metals come in waste water treatment plants from industrial discharges, storm wa­ter, etc. Toxic metals may damage the biologi­cal treatment process, being usually inhibitory to both aerobic and anaerobic processes.

How­ever, there are microorganisms with metabolic activity resulting in solubilisation, precipitation chelation, bio methylation, volatilization of heavy metals. Metals from waste water such as iron, copper, cadmium, nickel, uranium can be mostly complexed by extracellular polymers produced by several types of bacteria (B. licheniformis, Zooglearamigera).

Subse­quently, metals can be accumulated and then released from biomass by acidic treatment. Non-living immobilized bacteria, fungi, algae are able to remove heavy metals from waste water.

The mechanisms involved in metal re­moval from waste water include:

a. Adsorption to cell surface

b. Complexation and solubilisation of metals

c. Precipitation

d. Volatilization

e. Intracellular accumulation of metals

f. Redox transformation of metals

g. Use of recombinant bacteria.

For example, Cd2+ can be accumulated by bacteria, such as E. coli, B. cereus, fungi (As­pergillusniger). The hexavalent chromium (Cr6+) can be reduced to trivalent chromium (Cr3+) by the Enterobacter cloacae strain; sub­sequently Cr3+ precipitates as a metal hydroxide.

Some microorganisms can also transform Hg2+ and several of its organic com­pounds (methyl mercury, ethyl mercuric phos­phate) to the volatile form HgO, which is in fact a detoxification mechanism. The metabolic activity of some bacteria (Aero monas, Flavobacterium) can be exploited to transform selenium to volatile alkylselenides as a result of methylation.

Essay # 5. Solid Waste Bio-Treatment:

The implementation of increasingly stringent standards for the discharge of wastes into the environment, as well as the increase in cost of habitual disposal or treatment options, has motivated the development of different pro­cesses for the production of goods and for the treatment and disposal of wastes.

These pro­cesses are developed to meet one or more of the following objectives:

1. To improve the efficiency of utilization of raw materials, thereby conserving re­sources and reducing costs

2. To recycle waste streams within a given facility and to minimize the need for efflu­ent disposal

3. To reduce the quantity and maximize the quality of effluent waste streams that are created during production of goods

4. To transform wastes into marketable prod­ucts.

The multitudes of ways in which the trans­formation of wastes and pollutants may be car­ried out can be classified as being chemical or biological in nature. Bio-treatment can be used to detoxify waste streams at the source-before they contaminate the environment-rather than at the point of disposal.

In fact, waste represents one of the key intervention points of the potential use of environmental biotech­nology. Bio-waste is generated from various anthropogenic activities (households, agricul­ture, horticulture, forestry, waste water treat­ment plants), and can be categorized as: ma­nures, raw plant matter, process waste.

Bio­logical waste treatment aims to the decompo­sition of bio-waste by organisms in more stable, bulk-reduced material,which contributes to:

a. Reducing the potential for adverse effects to the environment or human health

b. Reclaiming valuable minerals for reuse

c. Generating a useful end product.

Advantages of the biological treatment in­clude:

a. Stabilization of the waste

b. Reduced volume in the waste material

c. Destruction of pathogens in the waste ma­terial

d. Production of biogas for energy use.

The end products of the biological treat­ment can, depending on its quality, be recycled as fertilizer and soil amendment, or disposed. Solid waste can be treated by biochemical means, either in situ or ex situ . The treat­ments could be performed as aerobic or anaero­bic depending on whether the process requires oxygen or not.

1. Anaerobic Digestion:

Anaerobic digestion of organic waste acceler­ates the natural decomposition of organic ma­terial without oxygen by maintaining the tem­perature, moisture content and pH close to their optimum values. Generated CH4 can be used to produce heat and electricity.

The most common applications of solid-waste bio-treatment include:

a. The anaerobic treatment of biogenic waste from human settlements

b. The co-fermentation of separately collected biodegradable waste with agricultural and/or industrial solid and liquid waste

c. Co-fermentation of separately collected biodegradable waste in the digesting tow­ers of municipal waste treatment facilities

d. Fermentation of the residual mixed waste fraction within the scope of a mechanical- biological waste-treatment concept.

Anaerobic processes consume less energy, produce low excess sludge, and maintain enclosure of odour over conventional aerobic pro­cess. This technique is also suitable when the organic content of the liquid effluent is high. The activity of anaerobic microbes can be tech­nologically exploited under different sets of conditions and in different kinds of processes, all of which, however, rely on the exclusion of oxygen.

2. Composting:

The biological decomposition of the organic compounds of wastes under controlled aerobic conditions by composting is largely applied for waste bio-treatment. The effective recycling of bio-waste through composting or digestion can transform a potentially problematic ‘waste’ into a valuable ‘product’ compost.

Almost any organic waste can be treated by this method, which results in end products as biologically stable humus-like product for use as a soil con­ditioner, fertilizer, bio-filter material, or fuel. Degradation of the organic compounds in waste during composting is initiated predomi­nately by a very dissimilar community of mi­croorganisms: bacteria, actinomyctes, and fungi.

An additional inoculum for the composting process is not generally necessary, because of the high number of microorganisms in the waste itself and their short generation time. A large fraction of the degradable organic car­bon (DOC) in the waste material is converted into carbon dioxide (CO2). CH4 is formed in anaerobic sections of the compost, but it is oxi­dized to a large extent in the aerobic sections of the compost.

The estimated CH4 released into the atmosphere ranges from less than 1% to a few per cent of the initial carbon content in the material .Composting can lead to waste stabilization, volume and mass reduction, drying, elimination of phytotoxic substances and undesired seeds and plant parts, and sanita­tion.

Composting is also a method for restora­tion of contaminated soils. Source separated bio-wastes can be converted to a valuable re­source by composting or anaerobic digestion.

In recent years, both processes have seen re­markable developments in terms of process design and control. In many respects, composting and digestion differ from other waste management processes in that they can be carried out at varying scales of size and com­plexity. Therefore, this enables regions to implement a range of different solutions: large and small-scale systems, a centralized or de­centralized approach.

Essay # 6. Biodegradation of Hydrocarbons:

Hydrocarbons can generate significant pollu­tion because they are among the most com­mon contaminants of groundwater, soil and sea when oil is spilled (Mohn 1997). The damage caused by oil spills in marine or freshwater systems is usually caused by the water-in-oil emulsion.

Various types of microorganisms can degrade hydrocarbons: bacteria, yeasts, filamentous fungi, but none of them degrade all of the possible hydrocarbon molecules at the same rate.

Each organism may have a differ­ent spectrum of activity and a definite prefer­ential use of certain chain lengths hydrocar­bon structures. Almost all petroleum hydro­carbons can be oxidized to mainly water and carbon dioxide, but the rate at which the pro­cess takes place is dependent on their nature, amount and the physical and chemical prop­erties that influence their persistence and bio- degradability.

Hydrocarbons are subject to both aerobic and anaerobic oxidation. Usually, the first stage of biodegradation of insoluble hydrocarbons is predominantly aerobic, while the organic carbon content is reduced by the action of anaerobic organisms. The prevailing environmental factors and the types, numbers and capabilities of the mi­croorganisms present affect the biodegradation occurrence and rate.

Factors affecting hydro­carbon biodegradation in contaminated soils can be:

a. The occurrence of optimal environmental conditions to stimulate bio-degradative ac­tivity

b. The predominant hydrocarbon types in the contaminated matrix; the bioavailability of the contaminants to microorganisms

c. Dispersion and emulsification enhancing rates in aquatic systems and absorption by soil particulates.

Hydrocarbons have different solubility in water where they are only degraded. Due to different hydrophobicity and low solubility in water of the hydrocarbons, the process should be intensified by enhancing physical contact between microorganisms and oil by adding adjuvants to improve the contact areas or by injecting of mixtures of microorganisms, dur­ing the so-called bio-augmentation.

It is also known that the activity of bacte­ria and fungi able to oxidize hydrocarbons could be improved by supplementation with various nutrients (sources of nitrogen and phosphorous). Different organisms need dif­ferent types of nutrients. Bio-enhancement is applied to stimulate the activity of bacteria already present in the soil at a waste site by adding different nutrients).

Bio-Sorption:

Bio-sorption is a fast and reversible process for the removal of toxic metal ions from waste water by live or dried biomass, which re­sembles adsorption and in some cases ion ex­change. The bio-sorption offers an alternative to the remediation of industrial effluents as well as the recovery of metals contained in other media.

Bio-sorbents are prepared from naturally abundant and waste biomass. Due to the high uptake capacity and very cost-ef­fective source of the raw material, bio-sorption is a progression towards a perspective method.

It has been demonstrated that both living and non-living biomass may be utilized in biosorptive processes, as they often exhibit a marked tolerance towards metals and other adverse conditions. Metal ions can bind to cells by different physiochemical mechanisms, de­pending on the bacterial strain and environ­mental conditions.

Because of this variability, current knowledge of these processes is incom­plete. In general, bacterial cell walls are poly- electrolytes and interact with ions in solution so as to maintain electro neutrality.

The mecha­nisms by which metal ions bind onto the cell surface most likely include electrostatic inter­actions, van der Waals forces, covalent bond­ing, redox interactions, and extracellular pre­cipitation, or some combination of these pro­cesses.

Bio-sorption of heavy metals by algal biomass is an advantageous alternative, an ap­propriate and economically feasible method used for wastewater and waste clean-up, be­cause it uses algal biomass sometimes consid­ered waste from some biotechnological pro­cesses or simply its high availability in coastal areas makes it suitable for developing new by-­products for waste water treatment plants.

Essay # 7. Biodegradation of Refractory Pollutants and Waste:

The biodegradability of refractory pollutants was investigated and applied by numerous researchers, since this becomes more and more a stringent problem of the environment be­cause of previous or current pollution.

1. Cyanide Removal:

Effluents containing cyanide from various in­dustries must be treated before discharging into the environment. The conventional physicochemical processes for removal of cya­nides from waste water proved to present ad­vantages, but also disadvantages burdened with high reagent and liability costs.

Bio-removal was seen as an environment friendly alternative treatment process able to achieve high degradation efficiency at low costs.In biological treatment of cyanide, bac­teria convert free and metal-complex cyanides to bicarbonate and ammonia.

The free metals are further adsorbed or precipitated from solution.The microorganisms responsible for cyanide degradation could be bacteria or fungi, which use cyanide as a source of nitrogen and carbon.

2. Distillery Spent Wash:

This is a liquid waste generated during alco­hol production,which confers unpleasant odours for waste water, posing a serious threat to water quality. Disposal of distillery spent wash on land is moreover hazardous to the veg­etation, since it reduces soil alkalinity and manganese availability, thus inhibiting seed regeneration.

A number of clean-up technolo­gies are used to process this effluent efficiently and economically and novel bioremediation ap­proaches for treatment of distillery spent wash are being worked out.

3. Radionuclides:

Radionuclide like uranium or thorium are of particular concern in environmental impact and remediation researches due to their high toxicity and long half-lives, thus they are con­sidered severe ecological and public health hazards. Biosorptive accumulation of uranium and other radionuclides is of great interest for the development of microbe based bioremedia­tion strategies.

4. Heavy Metals:

The application of biotechnological processes for the effective removal of heavy metals from contaminated waste waters has emerged as an alternative to conventional remediation tech­niques. Heavy metal pollution is usually gene­rated from electroplating, plastics manufactur­ing, fertilizers, pigments, mining, and metal­lurgical processes.

The application of conven­tional treatments is sometimes restricted due to technological and economical constraints. Metal accumulation on biomass can be passive (biosorptive), when non-living biomass is used as bio sorbent, or bio accumulative, by apply­ing living cells.

Essay # 8. Environmental Biotechnology in Pollution Detection and Monitoring:

Environmental monitoring deals with the as­sessment of environmental quality, essentially by measuring a set of selected parameters on a regular basis. In general, two methods-physicochemical and biological are available for measuring and quantifying the extent of pollution.

In the past decades environmental moni­toring programmes concentrated on the mea­surement of physical and chemical variables, while biological variables were occasionally incorporated. Physicochemical methods in­volve the use of analytical equipment, having limitations regarding their cost (because of the complexity of the samples and the expertise of the operators needed to conduct the analysis) and the lack of hazard and toxicological infor­mation.

Environmental monitoring is of great importance for its protection. The harmful ef­fect of toxic chemicals on natural ecosystems has led to an increasing demand for early- warning systems to detect those toxicants at very low concentrations levels.

Typically contaminant monitoring involves the regular and frequent measurement of vari­ous chemicals in water, soil, sediment and air over a fixed time period, e.g., a year. Integration of environmental biotechnology with in­formation technology has revolutioned the ca­pacity to monitor and control processes at molecular levels “in order to achieve real-time information and computational analysis in complex environmental systems”.

Bio-Indicators (Biomarkers):

More recently, environmental monitoring programmes have, apart from chemical mea­surements in physical compartments, included the determination of contaminant levels in biota, as well as the assessment of various re­sponses of biological/ecological systems. Nowa­days, temporal and spatial changes in selected biological systems/parameters can and are used to reflect changes in environmental qual­ity through bio-monitoring.

In this context, some organisms or communities may react to an environmental effect by changing a mea­surable biological function and/or their chemi­cal composition. This way it is possible to in­fer significant environmental change and their responses are referred to as bio-indicators.

Biomarkers are thus used in bio-monitoring programmes to give biological information, i.e., the effects of pollutants on living organisms. Three main types of indications can be ob­tained on exposure, effect, and susceptibility.

Biomarkers that have potential for use in bio monitoring are:

a. Molecular (gene expression, DNA integ­rity)

b. Biochemical (enzymatic, specific proteins or indicator compounds)

c. Histo-cytopathological (cytological, histopathological)

d. Physiological

e. Behavioural.

Unfortunately, field application of biomarkers is subject to various constraints (e.g., the availability of living material) that can limit data acquisition and prevent the use of multivariate methods during statistical analysis.

Besides, they should have the follow­ing attributes: be sensitive (so that it can act as an early-warning), specific (either to a single compound or a class of compounds), broad ap­plicable, easy to use, reliable and robust, good for quality control, able to be readily taught to the personnel, provide the data and informa­tion necessary.

Biosensors for Environmental Monitoring:

Research on bio-sensing techniques and devices for environment, together with that in genetic engineering for sensor cell development have expanded in the latest time. Environmental biosensors are analytical devices composed of a biological sensing element or biomarker (en­zyme, receptor antibody or DNA) in intimate contact with a physical transducer (optical, mass or electrochemical), which together re­late the concentration of an analyte to a mea­surable electrical signal.

The biosensors exploit biological specific­ity to produce signals that can be used to mea­sure pollution levels. Generally speaking, bio­sensor is a broad term that refers to any sys­tem that detects the presence of a substrate by use of a biological component which then provides a signal that can be quantified. The signal may be electrical or in the form of a dye that changes colour.

They comprise a biologi­cal recognition element such as an enzyme, antibody or cell that will react with the mate­rial to be detected. Biosensors based on a com­bination of a biological sensing element and an electronic signal-transducing element that offer high selectivity, high sensitivity, short- response time, portability and low cost, are ideal for monitoring pollutants in environment.

Biosensors can be applied for:

a. Toxicity screening of samples using bioluminescence or fluorescence,

b. Water quality monitoring,

c. Atmospheric quality bio-monitoring, and

d. Soil-contamination bio-monitoring.

Essay # 9. Environmental Biotechnology for Pollution Prevention and Cleaner Production:

Role of biotechnology in integrated environmental protection approach:

Biotechnology is regarded as the motor for in­tegrated environmental protection.

Comple­mentary to pollution control which struggles for the tail end of the processes and manages pollution once it has been generated, pollution prevention works to stop pollution at its source by applying a number of practices, such as:

a. Using more efficient raw materials,

b. Substituting less harmful substances for hazardous materials,

c. Eliminating toxic substances from produc­tion process, and

d. Changing processes.

The strengthening of concerns for the glo­bal environment is resulting in increased pres­sure for economical branches (industry, agri­culture, transport, market) to focus on pollu­tion prevention rather than end-of-pipe clean-up.

From an overall material consump­tion perspective, excessive quantities of waste in society result from inefficient production processes (on the industrial side), and unsus­tainable consumption patterns combined with low sustainability of goods. Modern environ­mental protection starts with the prevention of harmful substances prior to and during in­dustrial production processes.

Although environmental biotechnology has primarily focused on the development of tech­nologies to treat aqueous, solid and gaseous wastes at present, the basic information on how “biotechnology can handle these wastes has been gained and the focal point is now on the implementation of these processes as Best Available Technology Not Entailing Excessive Costs (BATNEEC) in the framework of strict and transparent environmental legislation”.

The application of biotechnology as an environment-friendly alternative in conventional manufacturing proves to be very useful for pollution prevention through source reduction, waste minimization, recycling and reuse. In most cases, this results in lower production costs, less pollution and resource conservation and may be considered as task force of biotech­nology for sustainability in industrial deve­lopment.

The main areas in which biotechnol­ogy contribution may be relevant fall into three broad categories: process changes, biological control, bio-substitutions. Because biotechnological processes, once set up, are considered cheaper than traditional methods and changes in production processes will not only contribute to environmental protection, but also help com­panies save money and continuously improve their public image.

In the context of pollution prevention practices, biotechnology can con­tribute to substitute multistep chemical pro­cesses with a one-step biological process us­ing genetically modified organisms (GMOs) as well. This action should have other beneficial results because land disposal of hazardous waste, waste water loadings, air emissions and production costs are greatly reduced.

Also, prevention practices assisted by environmen­tal biotechnology may prove instrumental in permitting procedural changes.

Essay # 10. Environmental Biotechnology Challenges and Perspectives:

New environmental challenges continue to evolve and new technologies for environmen­tal protection and control are currently under development.

Also, new approaches continue to gain more and more ground in practice, har­nessing the potential of microorganisms and plants as eco-efficient and robust clean-up agents in a variety of practical situations as mentioned below:

a. Enzyme engineering for improved biode­gradation.

b. Evolutionary and genomic approaches to biodegradation.

c. Designing strains for enhanced biodegra­dation.

d. Process engineering for improved biodeg­radation.

e. Re-use of treated waste water.

f. Bio-membrane reactor technology.

g. Design waste water treatment based on decentralized sanitation and re-use.

h. Implementation of anaerobic digestion to treat bio-waste.

i. Bio-development of bio-waste as an alter­native and renewable energy resource.

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