BIOREMEDIATION FOR HAZARDOUS WASTES INTRODUCTION For thousands of

BIOREMEDIATION FOR HAZARDOUS WASTES INTRODUCTION ❑ For thousands of years, human civilization has benefited from biologically medicated processes ❑ Rapid industrialization and urbanization have resulted in soil, surface and ground water contamination involving a wide variety of natural and anthropogenic chemicals. ❑ Remediation: biological, physicochemical, or thermal ( ascending order of cost) ❑ Either singly or in combination ❑ Bioremediation is the least expensive ❑ Bioremediation is a general term used to describe the use of biological contaminants to destroy, transform, or immobilize environmental contaminants to protect potential sensitive receptors ❑ The acceptance of bioremediation has followed from biotechnological advances that provide and increasingly through knowledge of the system and knowledge about optimizing the process to achieve not only high removal efficiencies but also to achieve these treatment efficiencies over long periods of time with minimal maintenance. ❑ Bioremediation processes are currently used to treat a wide range of chemicals in ground water, soils, and sediments. BIOREMEDIATION Biology “Remediate” = To solve a problem Bio-Remediate = to use biological organisms to solve an environmental problem

PRINCIPLES OF BIOREMEDIATION Bioremediation is based on the idea that organisms are capable to take in things from the environment and use it to enhance their growth and metabolism. With this unique characteristic lay the fundamental principle of Bioremediation, to use microorganism to take in contaminated substances from the environment or convert it to a nontoxic form. Bacteria, Protista, and fungi are well known for degrading complex molecules and transform the product into part of their metabolism. PROCESS OF BIOREMEDIATION 1. Microbes releases enzyme to break down the contaminant into digestible pieces 2. The contaminant of organic substances is ingest and digest as food along with other energy source by the cell. Bioremediation is beneficial because: Consume organic waste ❑ Grow and reproduce rapidly in selected environment ❑ Digest the waste quickly and completely ❑ Work without causing odors or poisonous compounds ❑ Non-pathogenic - (Does not cause disease in humans or animals) ❑ Generate environment friendly and less toxic substances such as: ❑ Carbon dioxide ❑ Water ❑ Smaller, less toxic organic compounds Where can apply bioremediation Bioremediation can be used to decompose or degrade: ❑ Crude oil spills ❑ Sewage effluent ❑ Chlorinated and non-chlorinated solvents in the industrial areas ❑ Coal Products: phenols and cyanide ❑ BTEX compounds ❑ Soils, lagoons, sludges, and process-waste streams

❑ ❑ Agricultural chemicals and pesticides in groundwater and rivers Gasoline and fuel oil contamination Creosote contaminants(wood preservatives) Ethylene glycol (antifreeze), methanol, methylketone (MEK), ether Where bioremediation is less effective Biodegradation is not very effective at sites with high concentrations of the following materials which are toxic to microorganisms. ❑ Metals - solidification/stabilization is the usual treatment process ❑ Highly chlorinated organics such as Inorganic salts Heavy metals are not biodegradable, but bacteria can be used to concentrate them into a more easily disposable form. ❑ Mercury: experiments with bacteria are on-going ❑ Uranium: iron-eating bacteria can remove low levels of radioactive waste from water. Other metals may be Ag, Al, As, Be, Cd, Cu, Fe, Ni, Pb, Se, Zn & Radioactive elements and there derivatives* (Meagher 2000, Allen 2002) On the basis of metabolic reaction pathway bioremediation can be classified as : Aerobic (with oxygen) - Microorganisms use available atmospheric oxygen to function. Food sources are converted to energy by the transfer of electrons to oxygen, which is an electron acceptor. Anaerobic(without oxygen) - Microorganisms break down chemical compounds to release the energy required to function. As electron acceptors, they utilize: - nitrates - sulfates - carbon dioxide - ferrous metals (such as iron) How bioremediation proceed (Mechanism): Bioremediation is based on the idea that organisms are capable to take in things from the environment and use it to enhance their growth and metabolism. With this unique characteristic lay the fundamental principle of Bioremediation, to use microorganism to take in contaminated substances from the environment or convert it to a nontoxic form. Bacteria, Protista, and fungi are well known for degrading complex molecules and transform the product into part of their metabolism. - Microbes releases enzyme to break down the contaminant into digestible piece - The contaminant of organic substances is ingest and digest as food along with other energy source by the cell. What are the optimum conditions for the better bioremediation? To optimize and accelerate the bioremediation of contaminants follow some conditions, such as: -

Food: - organic waste containing water (moisture content between 30 -80%) & added nutrients (Nitrogen, Phosphorous, Sulfur) present organic matter content in waste serves as a source of carbon, nutrients & energy for the metabolic reactions during bioremediation process. Micronutrients in addition to N, P & S many other micronutrients are needed to a lower concentration such as K, Ca, Mg, Fe, Ni & others Oxygen if required (aerobic types): - 3 -5 pounds of oxygen per pound of hydrocarbon to be converted Moderate p. H: - between 6 -9, neither too acidic nor too alkaline Moderate Temperatures: - 50 o to 100 o F Enzymes: - Chemical catalysts to break waste materials into smaller pieces SOME MICROORGANISMS USED IN BIOREMEDIATION Microorganism Yeast Cyanobacteria Characteristics Significance aerobic/ micro-aerophilic Degrades complex compounds aerobic/ micro-aerophilic/ anaerobic Self-sustaining, light is primary energy source Oligotrophs aerobic Removes TRACE concentrations of organic substances EXAMPLES OF MICROBES USED FOR SPECIFIC CHEMICALS Compound Name Aliphatics (non-halogenated) Ex. Acrylonitrile Aliphatics (halogenated) Ex. Trichloroethane Aromatic compounds Ex. BTEX, creosol, phenol Microorganisms Mixed culture and activated sludge Marine bacteria, sewage sludge, soil bacteria, methanogens Pseudomonas spp. , Bacillus spp. , Rhodococcus spp. , Mycobacterium Typical Bact eria Species inclu de: spp. (in descending order of occurrence) Conditions Aerobic + Anaerobi c Aerobic + Anaerobic

Flavobacterium, Pseudomas, Arthobacter, Alcaligenes, Corynbacterium, Achrombacter, Acinetobacter, Micrococcus, Nocardia, Mycobacterium Summary of Metabolism Reactions Various Bioremediation Methods Bioremediation in situ Engineered Biostimulation Adding Oxygen -Bioventing -Biosparging Adding. Oxygen and Nutrients exsitu Intrinisic Landfarming Bioreactor Bioaugmentation Adding. Oxygen, Nutrientsand Bacteria Bioremediation methods Bioremediation technologies can be broadly classified as ex situ and in situ. Ex situ technologies are those treatments which involve the physical removal of the contaminated material for treatment process. In situ in situ means to examine the phenomenon exactly in place where it occurs (without removing it in some special medium etc. ) so this techniques involve treatment of the contaminated material on site.

Source http: //www. envirotools. org/factsheets/images/bioremediation 2. gif Some of the bioremediation methods are as follows: ❑ Land farming : Solid-phase treatment system for contaminated Soils. ❑ Composting: Aerobic, thermophilic treatment process in which contaminated material is mixed with a bulking agent; can be done using static piles or aerated piles. ❑ Bioreactors: Biodegradation in a container or reactor; may be used to treat liquids or slurries. ❑ Bioventing: Method of treating contaminated soils by drawing oxygen through the soil to stimulate microbial activity. ❑ Biofilters: Use of microbial stripping columns to treat air emissions. ❑ Bioaugmentation: Addition of bacterial cultures to a contaminated medium; frequently used in both in situ and ex situ systems. ❑ Biostimulation: Stimulation of indigenous microbial populations in soils or ground water by providing necessary nutrients. ❑ Intrinsic bioremediation: Unassisted bioremediation of contaminant; only regular monitoring is done. ❑ Pump and treat: Pumping ground water to the surface, treating, and reinjecting.

Phytoremediation comprise growing plants on contaminated sites so that polluting components percolate through the radical system of the plants and accumulate in various parts of plants. Plants have a natural capicity to accumulate essential heavy metals (Fe, Mn, Zn, Mg, Mo and Ni) from soil or water for their growth and development. Organics Organic contaminants like pesticides, organ chlorines, polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), synthetic dyes, wood preservatives, munitions waste and synthetic polymers can be either degraded or converted into less toxic forms by bioremediation. Fungal bioremediation Synthetic dyes/pesticides/PCBs are introduced into the environment by the agricultural, sanitization, textile, dying, paint, refinery, and electrical industries. Fortunately, bacteria and several soil fungi (e. g. fusarium, Penicillium) are now known to degrade pesticides, with greater efficacy. Biosparging is an in situ remediation technology that exploits and stimulates indigenous microorganisms to degrade organic contaminants in saturated soil. Via borehoes, air is injected into the saturated zone (below the water table) to increase the activity of the soils indigenous microorganisms through increased oxygen dissolution. The increased oxygen enhances aerobic biodegradation of the contaminants present in the soil or groundwater. Biosparging can be used to reduce petroleum constituents that are adsorbed to soil within the capillary fringe, below the water table or dissolved in groundwater. Biosparging is commonly used at sites with mid-weight petroleum products such as diesel fuel; lighter petroleum products tend to volatilise swiftly and are removed very rapidly through sparging. Soil permeability is a key factor in the effectiveness of the technology. Bioventing is a promising new technology that stimulates the natural in situ biodegradation of petroleum hydrocarbons in soil by providing oxygen to existing soil microorganisms. In contrast to soil vapor vacuum extraction, bioventing uses low air flow rates to provide only enough oxygen to sustain microbial activity. Oxygen is commonly supplied through direct air injection into residual contamination in soil. In addition to degradation of adsorbed fuel residuals, volatile compounds are biodegraded as vapors move slowly through biologically active soil. Two basic criteria must be satisfied for successful bioventing. First, air must be able to pass through the soil in sufficient quantities to maintain aerobic conditions; second, natural hydrocarbon-degrading microorganisms must be present in concentrations large enough to obtain reasonable biodegradation rates. Bioventing techniques have been successfully used to remediate soils contaminated by petroleum hydrocarbons, nonchlorinated solvents, some pesticides, wood preservatives, and other organic chemicals. BIOAUGMENTATION can be defined as The addition of pregrown microbial cultures to enhance microbial populations at a site to improve contaminant clean up and reduce clean up time and cost. ❑

❑ Biodegradation is the major process affecting natural attenuation of contaminants. During the process contaminants are metabolized into less toxic or non-toxic compounds by naturally occurring organisms. PHYTOREMEDIATION: This technology typically involves the use of plants to remove, transfer, stabilize, or destroy contaminants in soil, sediment, or groundwater. The mechanisms of phytoremediation include enhanced rhizosphere biodegradation (takes place in soil or groundwater immediately surrounding plant roots). Phytoremediation applies to all biological, chemical, and physical processes that are influenced by plants (including the rhizosphere) and that aid in cleanup of the contaminated substances. Phytoremediation may be applied in situ or ex situ to soils, sludges, sediments, other solids, or groundwater Phytoextraction (also known as phytoaccumulation, the uptake of contaminants by plant roots and the translocation/accumulation of contaminants into plant shoots and leaves). Phytodegradation (metabolism of contaminants within plant tissues), and phytostabilization (production of chemical compounds by plants to immobilize contaminants at the interface of roots and soil). Phytotransformation - In this process, the plant absorbs and breaks down organic chemicals in contaminated soil and groundwater through its metabolic processes. MECHANISM FOR PHYTOREMEDIATION http: //www. itrcweb. org/PHYTO 2. pdf

COST ADVANTAGE OF PHYTOREMEDIATION

Biofiltration is a low-cost and highly effective air pollution control (APC) technology in which vapor-phase organic contaminants are passed through a bed of porous media and sorb to the media surface where they are degraded by microorganisms in the media. Specific strains of bacteria may be introduced into the filter and optimal conditions provided to preferentially degrade specific compounds. Typical Biofiltration Reactor EXAMPLES OF BIOFILTRATION INCLUDE ❑ Bioswales, Biostirps & biobags ❑ Constructed wetlands & natural wetlands ❑ Slow san filters ❑ Green belts ❑ Living walls ❑ Riparian zones, Riparian forests Applicability As with other biological treatment processes, biofiltration is highly dependent upon the biodegradability of the contaminants. Under proper conditions, biofilters can remove virtually all selected contaminants to harmless products. Biofiltration is used primarily to treat nonhalogenated VOCs and fuel hydrocarbons. Halogenated VOCs also can be treated, but the process may be less effective. Biofilters have been successfully used to control odors from compost piles. Gases where can apply the Biofiltration Rapidly degradable VOCs Alcohols Aldehydes Ketones Ethrs Esters Organic acids Amines Thiols Other molecules with O 2 N or S functional groups Rapidly Reactive VOCs H 2 S NOx SO 2 Slowly degradable VOCs Very Slowly degradable VOCs Hydrocarbons Halogenated hydrocarbons Phenols HCl NH 3 PH 3 Si. H 4 HF Methylene chloride Polyneric hydrocarbons CS 2

BIOREMEDIATION: A Choice to Make Advantages Why use bioremediation ❑ Minimal exposure of on site workers to the contaminant ❑ Long term protection of public health ❑ The Cheapest of all methods of pollutant removal ❑ The process can be done on site with a minimum amount of space and equipment ❑ Eliminates the need to transport of hazardous material ❑ Uses natural process ❑ Transform pollutants instead of simply moving them from one media to another ❑ Perform the degradation in an acceptable time frame Disadvantages Potential problems ❑ Cost overrun ❑ Failure to meet targets ❑ Poor management ❑ Climate Issue ❑ Regulatory compliance concern ❑ Release of contaminants to environment ❑ Unable to estimate the length of time it’s going to take, it may vary from site. It can takes a few month to as long as a few years. ❑ Not all organic compounds are biodegradable ❑ There are some concerns that the products of biodegradation many be more toxic then it’s parental form CONCLUSION Bioremediation offers a viable alternative to the regular use of physicochemical methods of decontamination, which are not generally cost effective. The bioremediation process is influenced by various factors- existence of a specific microbial population, bioavailability of contaminants, and environmental factors (Soil type, temperature, p. H, Nutrients and presence of oxygen or other electron acceptors). Although bioremediation may not completely detoxify inorganic pollutants (Metals & Radio nuclides), yet it can be alter the oxidation state, aiding in adsorption, uptake, accumulation and concentration in micro- or microorganisms.