Phytoremediation
Byproducts that are produced from our daily activities and not disposed of properly lead to contaminated soils and waters which pose a major environmental and human health problem can be treated with a process called “phytoremediation”. Phytoremediation is the the innovative use of green plants that can detoxify, or renew, soil or water that was contaminated with heavy metals or excess minerals. When the plants come into contact with the contaminants, they use many different physical and physiological mechanisms to remove or limit the effect of the contaminants so that the safety of our soils, waters, and air can be improved for human use. Various plants contain special “transporter” proteins, that are responsible for taking in micronutrients, allow for the plant to absorb mineral nutrients from the soil.
Eventually, these “transporter” proteins slow down and turn off as the nutrients build up to significant levels in the plant. The advantage to using phytoremediation is that it does not involve the very disruptive and expensive process of removing soil and physically extracting the contaminants, but the research is a slow, complicated, and painstaking process; however, if the process is successful, it provides an inexpensive “green” technology for cleaning up soil which can be used easily anywhere without needing special training or equipment. When the process is completed, the plants act as a ready-made storage containers for the contaminants during the process of shipping and treatment.
Bioleaching
Bioleaching is the process of extracting precious and base metals from hard-to-treat ores with the aid of bacterial microorganisms. It is considered to be an efficient and an ecologically friendly process commonly used by miners as an alternative to roasting or smelting, especially when there are lower concentrations of metal in the ore. The benefit of bioleaching is that it produces no offensive gases since it is a hydro-metallurgical form of treatment. On the other hand, the conventional smelting process releases large amounts of carbon dioxide, sulfur dioxide, and various toxic substances such as arsenic into the environment. The process works by having bacteria feed on the nutrients in the ore, thereby isolating the metal which can be collected from the bottom of the solution. This is possible because of the unique microorganism’s ability to react to and breakdown the mineral deposits in the ore. The bacteria tolerate acids
and metabolize sulphur, acting as a catalyst to accelerate the natural processes inside the ore. The use of a particular chemical reaction known as “oxidation reaction” to convert metal sulphide crystals into sulphates and sheer metals. In this reaction, the substance loses its electrons as it is separated into precious metals and unused sulphur and other acidic chemicals. At the end of the process, adequate materials accumulate at the bottom of the waste solution, which is then filtered to get to the pure metal. Unfortunately, bioleaching can only be used on ores that contain sulphur because the bacteria feed on sulphur. For certain types of metals, bioleaching is the primary method because it is very low in expenses, although it is a relatively slow process when compared to smelting. Bioleaching provides an alternative solution to conventional methods of extracting metals since it is an environment-friendly, effective and economical procedure.
Bioventing
Bioventing is an in-situ remediation technology that uses microorganisms to biodegrade organic constituents adsorbed on soils in the unsaturated zone. Bioventing enhances the activity of indigenous bacteria and simulates the natural in-situ biodegradation of hydrocarbons in soil by inducing air or oxygen flow into the unsaturated zone through a direct injection of air into residual contamination in soil and by adding nutrients if necessary. The process primarily assists in the degradation of adsorbed fuel residuals, but also assists in the degradation of volatile organic compounds as vapors move slowly through biologically active soil. Generally, the rate of natural degradation is limited by the lack of oxygen and other electron acceptors rather than by the natural lack of nutrients. Bioventing systems use low airflow rates to provide only enough oxygen to sustain microbial activity. The airflow
can be controlled with a one-way valve, installed on a vent well, which allows air to enter the well when the pressure inside is lower than atmospheric pressure, but closes when the atmospheric pressure drops below the subsurface pressure, trapping the air in the well and leading to an increase in oxygen to the soil surrounding the well.
Landfarming
Landfarming is a bioremediation treatment process that is performed in the upper soil zone or in biotreatment cells. The process works by incorporating the contaminated soils, sediments, or sludges into the soil surface and periodically turning over or tilled to aerate the mixture. The contaminants are degraded, transformed, and immobilized by microbiological processes and by oxidation. The in situ systems have been used to treat near surface soil contamination for hydrocarbons and pesticides. Soil conditions such as: moisture content, frequency of aeration, and pH are conditions that may be controlled. The equipment used is typically the same as those used in agricultural operations. These landfarming activities cultivate and enhance the microbial degradation of hazardous compounds. Generally, the higher the molecular weight, the slower the degradation rate, and the more chlorinated or nitrated the compound,
the more difficult it is to degrade. The effectiveness of landfarming can be limited by factors such as: large space requirements; uncontrollable advantageous conditions for biological degradation of contaminants; inorganic contaminants are not biodegraded; the potential of large amounts of particulate matter released by the process; and the presence of metal ions may be toxic to microbes and may leach from the contaminated soil into the ground.
Composting
Composting is a simple way to resupply depleted soil with nutrient-rich humus which fuels plant growth and restores vitality. Composting is beneficial in that it: recycles kitchen and yard waste, introduces beneficial organisms to the soil, is a natural alternative to chemical fertilizers, and reduces landfill waste. Microorganisms such as bacteria, fungi, and actinomycetes account for most of the decomposition that takes place in a pile. They are considered chemical decomposers because they change the chemistry of organic wastes. The larger decomposers, or macroorganisms, are mites, centipedes, sow bugs, snails, millipedes, springtails, spiders, slugs, beetles, ants, flies, nematodes, flatworms, rotifers, and earthworms. They are considered physical decomposers because they grind, bite, suck, tear, and/or chew materials into smaller pieces. The most important organism out of
these are the aerobic bacteria. They are the most abundant and millions of aerobic bacteria could be found in a gram of soil or decaying organic matter. Aerobic bacteria are also the most nutritionally diverse and can eat nearly anything. The bacteria utilize carbon as a source of energy (to continue eating) and nitrogen to build protein in their bodies (for growth and reproduction). They obtain their energy by oxidizing organic material which heats up the compost pile from ambient air temperature. If the proper conditions are present, then the pile will heat up fairly rapidly due to the bacteria consuming readily decomposable materials.
Bioaugumentation
Bioaugmentation is the process of adding actively growing, specialized microbial strains into a microbial community to enhance the ability of the microbial community to respond to process fluctuations or to degrade certain compounds, resulting in improved treatment. By inserting specific microbes, the characteristics of the microbial community can be improved. Bioaugmentation offers a wide range of advantages over traditional methods like chemicals, equipments, or other consumables, and has been used in the treatment of secondary wastewater for many years. While traditional methods can increase the quality of the sewage released, they are often expensive, hard
to maintain, and cover problems in the microbial community. Bioaugmentation allows for effective treatment without the investments in plant expansions and equipment solutions. In wastewater treatment systems, using bioaugmentation enhances the biomass and ensures that the microbial population is operating properly which in turn helps reduce the cost of the systems. By making sure that the microbial population is healthy and optimized, money can be saved through the reduced use of consumables. Maintaining a healthy microbial population through the use of bioaugmentation helps relieve treatment plants and operators of trouble.
Mycoremediation
Mycoremediation refers to the ability of mushrooms and their enzymes to degrade environmental contaminants and transform industrial and agro-industrial wastes into products. This process can occur in one of three ways: biodegradation, biosorption, or bioconversion.
Biodegradation is the ultimate breakdown and recycling of complex molecules into their mineral constituents like carbon dioxide, water, and other inorganic compounds. Mushrooms are able to produce enzymes such as extracellular peroxidases, ligninase, cellulases, pectinases, xylanases, and oxidases which help oxidize difficult pollutants in an outside environment. These enzymes have been found to be able to degrade non-polymeric as well as polymers such as plastics within in vitro conditions. The mechanisms surrounding biodegradation is very complex due to the influence of other biochemical systems and the interactions of enzymes with cytochrome P450 monooxygenase system along with others which are produced by the mushrooms.
Biosorption is considered to be an alternative to the remediation of industrial waste or sewage as well as the recovery of metals within it. The process is based on the sorption of pollutants, metallic ions, and xenobiotics from industrial effluents with the aid of live or dried biomass. To do this, the mushrooms use a combination of two processes: bioaccumulation and biosorption. Bioaccumulation includes both the transportation of the contaminant into the cell and partitioning into intracellular components, and biosorption is the binding of the pollutants to the biomass without the requirement of metabolic energy which may involve several chemical process including adsorption, ion exchange processes and covalent binding. Biosorption is efficient because of its high uptake capacity and has a very cost-effective source of raw material.
Bioconversion is the conversion of industrial or agro-industrial sludges into other useful forms. Any lignocellulosic waste from industries can be used to cultivate mushrooms to be used as a product. Using mushrooms for bioconversion of industrial wastes can provide more mushrooms and help in solving the contamination because the wastes are transformed into protein rich mushroom carpophores.
