Biofiltration, bioremediation and compost — waging war against pollution
Naturally-occurring microorganisms (bacteria, fungi, protists, etc.) release enzymes during feeding activity. These enzymes break molecular bonds, reducing hazardous substances into less toxic and non-toxic compounds. This decay is biodegradation and, eventually, all organic material will break down into basic elements.
While this process can and does occur in nature (natural attenuation), it works most effectively through controlled applications of a bio-media that will encourage the growth of pollution-eating microbes.
The same basic process that results in compost can be modified and/or managed to shift processing goals away from compost production to pollution abatement, volume reduction, biological drying and other remediation objectives.
Biofiltration is one method of capturing and sequestering pollutants long enough to allow biology to work its magic. Once trapped in a filter media containing compost, pollutants are exposed to aerobic microorganisms. Microbes feed. Molecules break down. Biodegradation takes place.
Compost in the media mix delivers the microbial populations responsible for biodegradation, breaking down compounds that generate odors and/or contribute to other forms of pollution.
Eventually, all nutrition in the filter is exhausted and the microbes die. When this happens, biofilter media must be replenished. The spent media can be composted and returned to the soil to rebuild topsoil and reinoculate soil with beneficial microorganisms. The mechanism used to scrub air exhausted from composting facilities is a form of biofiltration, as well.
Compost socks, berms and blankets are erosion control devices. They may also be considered biofilters. But these biofiltration devices are (typically) intended to remain at the point of deployment and are not replaced or recharged. Instead, they are seeded and remain as permanent, vegetated elements of the landscape. For erosion control contractors, this eliminates labor costs (compared to removing silt fence) and landfill charges related to the disposal of non-degradable erosion control devices.
Bioremediation is a methodology used to mitigate pollutants in soil or water, also through the use of microorganisms. It is often used in connection with clean-up projects. Efficient and cost-effective, bioremediation is an ideal solution for soils and water that can be treated in situ or in place.
However, any time compost is incorporated into soil, bioremediation can occur, whether added to farmland, home garden, highway construction project or sports field.
Amending soils to the recommended 5 percent organic matter can increase water-holding capacity by thousands of gallons. This means there is degradation of pollutants, plus a reduced volume of pollutant-laden runoff. Other stormwater management strategies, like roof gardens, rain gardens and porous pavement, can be more than 8 times the cost per gallon stored compared to soil amendment.
In addition to improved water retention, increasing soil organic matter (SOM) also offers bonus benefits like reduced synthetic fertilizer requirement, improved nutrient uptake, disease resistance and more.
In situ bioremediation for highly-contaminated zones that were once industrial sites, munitions ranges and underground storage tanks areas can be less expensive than the traditional method of excavation followed by off-site treatment and disposal/incineration.
With in-situ remediation, large quantities of soil, sediment or water do not need to be dug up, pumped out or transported for treatment/disposal. Soil can be amended in place, or temporary composting facilities can be constructed to process contaminants faster under highly-controlled conditions. Clean, remediated soil is then returned to the ground.
Water from contaminated aquifers and surface waters can be similarly treated. Biofiltration, bioremediation and compost make a dynamic, cost-effective team for many types of clean-up projects.
Munitions contamination cleanup
Both composting and compost use have roles to play in soil remediation. Aside from significant environmental benefits, there are economic advantages, too. Contaminated soil (and water) can be excavated for composting at an on-site or permitted off-site facility, or soils can be amended with compost for in-situ treatment. Both rely on natural microbial activity to breakdown and neutralize target compounds, though not all contaminants can be treated this way.
A case study from the U.S. Environmental Protection Agency (EPA) showcases the success of bioremediation at the Umatilla Army Depot in Hermiston, Oregon, where years of chemicals leaching from contaminated soils resulted in Umatilla being placed on the Superfund list for hazardous waste cleanup.
The clean-up costs for disposing of contaminated soil was just shy of $8 million for 15,000 tons of soil through the conventional method of incineration. Looking for a better, more cost-effective solution, the Army opted for a composting-related solution and realized over $2 million in savings per 15,000 tons. An additional bonus came in the $150,000 in revenue generated by selling the newly-treated soil. The U.S. Army Corps of Engineers estimated that if this method were used to clean up the remaining U.S. munitions sites, $200 million would be saved. Read more about munitions cleanup from the EPA.
For information about how McGill expertise, technologies and products can be used in bioremediation, please contact us.