Composting Applied To Contaminated Applied To Contaminated Soil ... evaluation, as is the soil ... • Laboratory and/or field treatability studies

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<ul><li><p>Composting Applied To Contaminated Sites </p><p> Presented To: Dr. Michael Broaders </p><p> 1 </p></li><li><p>The Project Is Submitted In Part Fulfillment Of The BSc.(Year 4) In </p><p>Environmental Science &amp; Technology Requirement For Waste </p><p>Management </p><p>"Composting Applied To Contaminated Soil" </p><p>Was Undertaken By: </p><p>Nevin Traynor, </p><p>Martina Mulligan, </p><p>And </p><p> Oliver Fitzsimmons </p><p> Table Of Contents: </p><p> 2 </p></li><li><p>Section Contents 1.0 Introduction 2.0 Main Types Of Composting </p><p>2.1 Landfarming 2.2 Biopiles 2.3 Windrow 2.4 Bioventing 3.0 Type Of Co-Composting </p><p> 3.1 Slurry-phase Bioremediation </p><p> 4.0 Addational Methods Of Composting </p><p>4.1 Injection Of Hydrogen Peroxide 4.2 PX-700 4.3 Bioslurping 4.4 Hydronamic In-situ Treatment (injection tm) </p><p> 5.0 Conclusion 6.0 References 1.0 Introduction </p><p> 3 </p></li><li><p> A problem that many landowners are faced with in today's environmentally conscious </p><p>society is the cleanup of contaminated soils. Often, with contaminated soil, petroleum </p><p>based products are the type of contaminant which is found. There are a number of </p><p>process designs used in composting. </p><p> Composting is defined as a controlled biological process by which organic </p><p>contaminants (e.g., PAHs) are converted by microorganisms (under aerobic and </p><p>anaerobic conditions) to innocuous, stabilised byproducts. Typically, thermophilic </p><p>conditions of 54 to 65 C must be maintained to properly compost soil contaminated </p><p>with hazardous organic contaminants. The increased temperatures result from heat </p><p>produced by microorganisms during the degradation of the organic material in the </p><p>waste. In most cases, this is achieved by the use of indigenous microorganisms. </p><p>Maximum degradation efficiency is achieved through maintaining oxygenation (e.g., </p><p>daily windrow turning), irrigation as necessary, and closely monitoring moisture </p><p>content, and temperature. These hydrocarbon contaminated soils may be cleaned in </p><p>several ways. If Volatile Organic Compounds (VOC) or Semi Volatile Organic </p><p>Compounds (SVOC) contaminants are present in soils, off-gas control may be </p><p>required. </p><p> Bioremediation, the process of using living organisms (usually bacteria, fungi, </p><p>actinomycetes, cyanobacteria and to a lesser extent, plants) to reduce or eliminate </p><p>toxic pollutants. These organisms may be naturally occurring or laboratory cultivated. </p><p>Certain microorganisms can digest organic substances such as fuels or solvents that </p><p>are hazardous to humans. The microorganisms break down the organic contaminants </p><p>into harmless products, mainly carbon dioxide and water. </p><p> Once the contaminants are degraded, the microorganism population is reduced </p><p>because they have used their entire food source. Dead microorganisms or small </p><p>populations in the absence of food pose no contamination risk. </p><p>Bioremediation harnesses this natural process by promoting the growth and/or rapid </p><p>multiplication of these organisms that can effectively degrade specific contaminants </p><p> 4 </p></li><li><p>and convert them to non-toxic by-products. Importantly, bioremediation can also be </p><p>used in conjunction with a wide range of traditional physical and chemical </p><p>technologies to enhance their efficiency. </p><p> Bioremediation results vary depending on the level, type and age of contaminants </p><p>involved as well as the site conditions, such as temperature, weather, and soil or water </p><p>chemistry. Total Petroleum Hydrocarbon reduction requires a period of between 90 </p><p>and 150 days, but it could take up to 18 months. </p><p> There are two methods of bioremediation: Augmented and Non-augmented. </p><p>Augmented bioremediation involves adding microbes that break down contaminants </p><p>to the soil. Non-augmented bioremediation uses chemicals to activate the local </p><p>microbes already present in the soil to breakdown the unwanted elements. </p><p> Before implementing any bioremediation scheme, you would need to conduct an </p><p>environmental audit of the site to determine the type of contaminant and whether </p><p>biotechnology would offer a suitable cure. At the moment, treatable contaminants </p><p>include: grease, hydraulic and lubricating fluids, petrol, antifreeze, brake fluids, oil, </p><p>diesel and paint thinner. The scale and levels of contamination are critical to a site </p><p>evaluation, as is the soil condition and the target standard. Also, this audit would </p><p>establish whether the soil needed to be removed, to be treated, or whether everything </p><p>could be sorted out on site. </p><p> The microbes' necessary must be dispersed throughout the soil. These microbes have </p><p>to be activated before being applied; usually by being mixed with water. This </p><p>solution is then added to the soil by a variety of techniques. Methods range from </p><p>simply spraying it on the surface of the contaminated area to dispersing it by </p><p>perforated plastic tubes sunk in the ground. </p><p>In order to sustain efficient rates of hydrocarbon degradation, the biopile environment </p><p>must provide certain essential elements to promote bacterial population growth. </p><p> 5 </p></li><li><p>The most efficient form of hydrocarbon degradation is accomplished by aerobic </p><p>bacteria. To survive, aerobic bacteria need oxygen, moisture and nutrients. </p><p> Bioremediation is estimated to cost 30-50% less than conventional cleanup </p><p>techniques, such as landfill or incineration. Environmentally, bioremediation offers a </p><p>better solution as the contaminants are broken down completely rather than simply </p><p>transported to another site or released into the atmosphere. </p><p> There is a number of steps in preparing a sound design for bio-treatment of </p><p>contaminated soil, these include: </p><p>Site characterisation. </p><p> Soil sampling and characterisation. </p><p> Contaminant characterisation. </p><p> Laboratory and/or field treatability studies. </p><p> Pilot testing and/or field demonstrations. </p><p>Site, soil, and contaminant characterisations will be used to: </p><p> Identify and quantify contaminants. </p><p> Determine requirements for organic and inorganic amendments. </p><p> Identify potential safety issues. </p><p> Determine requirements for excavation, staging, and movement of contaminated soil. </p><p> Determine availability and location of utilities (electricity and water). </p><p>Laboratory or field treatability studies are needed to identify: </p><p> Amendment mixtures that best promote microbial activity. </p><p> Potential toxic degradation byproducts. </p><p> Percent reduction and lower concentration limit of contaminant achievable. </p><p> The potential degradation rate. </p><p> Bioremediation applications fall into two broad categories: In-situ and Ex-situ. </p><p> 6 </p></li><li><p>In-situ techniques does not require excavation of the contaminated soils so it may be </p><p>less expensive, create less dust, and cause less release of contaminants than ex-situ </p><p>techniques. Also, it is possible to treat a large volume of soil at once. However In- </p><p>situ techniques, may be slower than ex situ techniques, it may be difficult to manage, </p><p>and are most effective at sites with permeable (sandy or uncompacted) soil. </p><p>In most cases, indigenous bacteria present in petroleum contaminated soil break down </p><p>petroleum hydrocarbons, which are a source of energy for the bacteria. </p><p>The advantage of treating petroleum contaminated soils using ex-situ techniques is the </p><p>ability to amend the contaminated soil with nutrients, bacteria and bulking agents. </p><p>By amending the contaminated soil, it is possible to construct a biopile with a more </p><p>conducive environment for bacterial growth, thus accelerating the breakdown of </p><p>petroleum compounds in the soil as compared to natural attenuation in-situ. </p><p> Petroleum compounds alone do not supply all the nutrients required by soil bacteria. </p><p>Nutrients already present in the soil vary from one soil type to another. </p><p>A common ratio to determine appropriate nutrient requirements is 100 parts total </p><p>carbon to 10 parts nitrogen to 1 part phosphorus. </p><p> Bacterial degradation occurs through a range of moisture field capacities of </p><p>approximately 20 to 80 percent. The optimum moisture field capacity for biopiles is </p><p>approximately 40 percent. This concentration represents a balance between having an </p><p>adequate supply of water in the soil matrix pore spaces without preventing effective </p><p>diffusion of oxygen. </p><p>2.0 Main Composting Methods Used In Bioremediation </p><p> 7 </p></li><li><p> 2.1 Landfarming </p><p> Landfarming, also known as land treatment or land application, is an aboveground remediation technology for soils that reduces concentrations of petroleum constituents </p><p>through biodegradation. This technology usually involves spreading excavated </p><p>contaminated soils in a thin layer on the ground surface and stimulating aerobic </p><p>microbial activity within the soils through aeration and/or the addition of minerals, </p><p>nutrients, and moisture. The enhanced microbial activity results in degradation of </p><p>adsorbed petroleum product constituents through microbial respiration. If </p><p>contaminated soils are shallow (i.e., less than 3 feet below ground surface), it may be </p><p>possible to effectively stimulate microbial activity without excavating the soils. If </p><p>petroleum-contaminated soil is deeper than 5 feet, the soils should be excavated and </p><p>reapplied on the ground surface </p><p> Application </p><p>Landfarming has been proven effective in reducing concentrations of nearly all the </p><p>constituents of petroleum products typically found at underground storage tank (UST) </p><p>sites. Petroleum products generally encountered at Underground Storage Tank sites </p><p>range from those with a significant volatile fraction, such as gasoline, to those that are </p><p>primarily nonvolatile, such as heating and lubricating oils. </p><p>Petroleum products generally contain more than one hundred different constituents </p><p>that possess a wide range of volatility. In general, gasoline, kerosene, and diesel fuels </p><p>contain constituents with sufficient volatility to evaporate from a landfarm. Lighter </p><p>(more volatile) petroleum products (e.g., gasoline) tend to be removed by evaporation </p><p>during landfarm aeration processes (i.e., tilling or plowing) and, to a lesser extent, </p><p>degraded by microbial respiration. </p><p>The mid-range hydrocarbon products (e.g., diesel fuel, kerosene) contain lower </p><p>percentages of lighter (more volatile) constituents than does gasoline. Biodegradation </p><p>of these petroleum products is more significant than evaporation. Heavier (non-</p><p>volatile) petroleum products (e.g., heating oil, lubricating oils) do not evaporate </p><p> 8 </p></li><li><p>during landfarm aeration; the dominant mechanism that breaks down these petroleum </p><p>products is biodegradation. However, higher molecular weight petroleum constituents </p><p>such as those found in heating and lubricating oils, and, to a lesser extent, in diesel </p><p>fuel and kerosene, require a longer period of time to degrade than do the constituents </p><p>in gasoline. </p><p> Operation Principles </p><p>Soil normally contains large numbers of diverse microorganisms including bacteria, </p><p>algae, fungi, protozoa, and actinomycetes. In well-drained soils, which are most </p><p>appropriate for landfarming, these organisms are generally aerobic. Of these </p><p>organisms, bacteria are the most numerous and biochemically active group, </p><p>particularly at low oxygen levels. Bacteria require a carbon source for cell growth and </p><p>an energy source to sustain metabolic functions required for growth. Bacteria also </p><p>require nitrogen and phosphorus for cell growth. Although sufficient types and </p><p>quantities of microorganisms are usually present in the soil, recent applications of ex-</p><p>situ soil treatment include blending the soil with cultured microorganisms or animal </p><p>manure (typically from chickens or cows). Incorporating manure serves to both </p><p>augment the microbial population and provide additional nutrients. </p><p>The metabolic process used by bacteria to produce energy requires a terminal electron </p><p>acceptor (TEA) to ensymatically oxidize the carbon source to carbon dioxide. </p><p>Microbes are classified by the carbon and TEA sources they use to carry out </p><p>metabolic processes. Bacteria that use organic compounds (e.g., petroleum </p><p>constituents and other naturally occurring organic) as their source of carbon are </p><p>heterotrophic; those that use inorganic carbon compounds (e.g., carbon dioxide) are </p><p>autotrophic. Bacteria that use oxygen as their TEA are aerobic; those that use a </p><p>compound other than oxygen, (e.g., nitrate, sulfate), are anaerobic; and those that can </p><p>utilise both oxygen and other compounds as TEAs are facultative. For landfarming </p><p>applications directed at petroleum products, only bacteria that are both aerobic (or </p><p>facultative) and heterotrophic are important in the degradation process. </p><p> 9 </p></li><li><p>The effectiveness of landfarming depends on parameters that may be grouped </p><p>into three categories: </p><p>1. Soil characteristics </p><p>2. Constituent characteristics </p><p>3. Climatic conditions. </p><p>1.Soil Characteristics: </p><p>Soil texture affects the permeability, moisture content, and bulk density of the soil. To </p><p>ensure that oxygen addition (by tilling or ploughing), nutrient distribution, and </p><p>moisture content of the soils can be maintained within effective ranges, you must </p><p>consider the texture of the soils. For example, soils that tend to clump together (such </p><p>as clays) are difficult to aerate and result in low oxygen concentrations. It is also </p><p>difficult to uniformly distribute nutrients throughout these soils. They also retain </p><p>water for extended periods following a precipitation event. </p><p>2.Constituent Characteristics: </p><p>The volatility of contaminants proposed for treatment by landfarming is important </p><p>because volatile constituents tend to evaporate from the landfarm, particularly during </p><p>tilling or ploughing operations, rather than being biodegraded by bacteria. </p><p>Controlling of volatile organic compounds (VOCs) before they are emitted to the </p><p>atmosphere maybe required by passing them through an appropriate treatment process </p><p>before being vented to the atmosphere. Control devices range from erected structures </p><p>such as a greenhouse or plastic tunnel to a simple cover such as a plastic sheet. </p><p>Although nearly all constituents in petroleum products typically found at UST sites </p><p>are biodegradable, the more complex the molecular structure of the constituent, the </p><p>more difficult and less rapid, is biological treatment. Most low molecular weight </p><p>(nine carbon atoms or less) aliphatic and monoaromatic constituents are more easily </p><p>biodegraded than higher molecular weight aliphatic or polyaromatic organic </p><p>constituents. </p><p> 10</p></li><li><p>3.Climatic Factors: </p><p>Typical landfarms are uncover...</p></li></ul>