Bioremediation for the remediation of contaminated soils

Every year, agricultural runoff, industrial waste and industrial accidents contaminate surface water, soil, air, water streams and reservoirs. A new composting technique known as compost bioremediation is currently being used to restore contaminated soils, manage stormwater, control odors and break down volatile organic compounds.

Bioremediation of compost refers to the use of a biological system of microorganisms in mature compost to bind or destroy pollutants from water or soil. Microorganisms consume pollutants from the soil, ground and surface water and the air.

The pollutants are digested, metabolized and converted into humus and inert products such as carbon dioxide, water and salts. It has been shown to be effective in breaking down or modifying many types of pollutants, such as: B. chlorinated and non-chlorinated hydrocarbons, wood preservatives, solvents, heavy metals, pesticides, petroleum products and explosives. Composts used in bioremediation are referred to as tailored or grown, in the sense that they are made specifically to treat specific pollutants in specific locations.

The ultimate goal of any remediation project is to return the site to its pre-contamination condition. This often includes reforestation or greening to stabilize the treated soil. Compost not only reduces pollution but also furthers its goal by promoting plant growth. In this role, compost provides soil conditioning and provides nutrients to a variety of plants.

Soil bioremediation

Heavy metal pollution

Dr. Rufus Chaney, a senior agricultural researcher with the U.S. Department of Agriculture, is an expert in using compost methods to correct metal-contaminated sites. In Bowie, Maryland, for example, high levels of lead were found in soils next to houses painted with lead-based paint. To determine the effectiveness of compost in reducing lead bioavailability in these soils, Chaney fed rats contaminated soil and contaminated soil mixed with compost. Both compost and soil traps introduced lead and therefore reduced its bioavailability; Soil treated with compost was more effective than untreated soil. In fact, the rats showed no toxic effects when lead-contaminated soil was mixed with compost, whereas soil alone did.

In another study, Dr. Lee Daniels and PD Schroeder from Virginia Polytechnic Institute in Blacksburg, Virginia, a landfill contaminated with sand and sludge from a heavy metal mine.

By spreading compost, the soil was revitalized for agricultural use. For the Dr. Grano production was used at 20 tonnes per acre and peanuts at 120 tonnes per acre.

Organic contaminants

Dr. Michael Cole, an expert in the breakdown of pollutants in soil, remedied the soil containing 3,000 parts per million (ppm) kl of the dicamba herbicide to undetectable levels within 50 days. Cole mixed wood chips and mature compost into the soil to create the combined substrate, 10% (by volume) compost and wood chips and 90% contaminated soil. According to Dr. Cole dicamba eventually breaks down in the soil, but this process takes years rather than days. Using compost not only speeds up the bioremediation process but can also save money. The traditional remediation method through landfill and incineration can cost five times or more than composting technology. According to Dr. Cole, more than any other soil cleanup technique, compost bioremediation results in enriched soil and leaves it in better condition than before contamination.

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Petroleum hydrocarbon pollution

At Seymour Johnson Air Force Base near Goldsboro, North Carolina, the soil is contaminated by frequent jet fuel spills and excavations for underground fuel storage tanks. The base addresses a variety of petroleum contaminants including gasoline, kerosene, fuel oil, kerosene, hydraulic fluid and motor oil.

In 1994, the base implemented a bioremediation system using compost made from wood waste and turkey droppings. Previous remediation systems involved lifting contaminated soil and transporting it to a brick manufacturer where it was burned at high temperatures. Compared to the cost of lifting, burning and purchasing clean soil, bioremediation with compost saved $133,000 in the first year. Using compost also resulted in faster cleanup, with projects being completed in weeks instead of months.

Compost fungi produce a substance that breaks down petroleum hydrocarbons and allows compost bacteria to metabolize them. A typical ratio is 75% contaminated soil, 20% compost and 5% turkey manure. A mechanical shovel mixes and stirs the piles to aerate them. After mixing, the stacks are covered with vinyl nylon to protect them from wind and rain and maintain the proper humidity and temperature for optimal microbial growth.

Stormwater management

This is excess water that is not absorbed into the ground after heavy rainfall. Core on areas such as streets, parking lots, building roofs, fields and gardens. On their way to larger bodies of water (lakes, streams, rivers), these bodies of water can carry a variety of potential environmental pollutants such as metals, oils and fats, pesticides and fertilizers. These types of pollutants pollute rural waterways, harm recreational and commercial fisheries, and diminish the beauty of waterways. According to the U.S. Environmental Protection Agency, this water must be treated before being discharged into natural streams. To achieve this, many municipalities and industries are turning to solutions that utilize composting technologies instead of other much more expensive traditional treatments. For example, there is a filter system that uses compost and retains more than 90% of solids, 85% of fats and oils and around 85% of oils and fats.

Biofiltration vs. bioremediation

During biofiltration, particles are physically separated according to their size.

Bioremediation, on the other hand, is a biochemical change in which pollutants are metabolized by microorganisms and converted into harmless, stable components such as carbon dioxide, water and salts.

*Translated and summarized by Bioagro
Source: EPA 530-f-97-042 (United States Environmental Protection Agency)

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