Bioremediation is a treatment method that uses microscopic organisms to break down hazardous wastes into harmless natural products, such as carbon dioxide. Bioremediation is one of the major treatment processes considered at hazardous waste sites. It is less expensive than many other treatment processes, including incineration (burning). Bioremediation first became an important waste treatment method in the late 1980’s.
Successful application of bioremediation requires an understanding of many factors about the microorganisms to be used in the breakdown of waste. Such factors include their nutrient needs, the environmental conditions that enhance their growth, and their relationship with other organisms in the environment. Engineers involved in bioremediation draw on knowledge from many scientific disciplines, including biochemistry, chemistry, ecology, hydrology, microbiology, physics, and soil science.
Microorganisms can grow under a variety of conditions, and they use various processes to obtain energy for growth. Growth that requires oxygen is referred to as aerobic. Some microorganisms require no oxygen. Instead, they use other substances—such as nitrate, sulfate, iron, and carbon dioxide—to break down energy sources in order to use them for growth. Growth that does not use oxygen is called anaerobic. Anaerobic microorganisms can be used to treat wastes in environments where oxygen levels are low, as in soils and ground water.
To stimulate growth of the specific microorganisms capable of removing the wastes present in a particular environment, engineers work to control that environment. Sometimes they remove the waste and put it into enclosures called surface reactors. Engineers can control many features of the environments within these reactors.
Many types of pollution are widespread, and waste removal is not possible. In such cases, engineers use in situ << ihn SY too >> bioremediation. In this process, oxygen, nutrients, or other materials that contribute to growth are added to the polluted area. The engineers then monitor the rate of waste breakdown. In situ bioremediation is used in such environments as polluted ponds or lagoons, soils, ground water, and areas contaminated by marine fuel spills. In some cases, no additives are required for in situ treatment because the environment already provides everything that organisms need to break down pollutants. In such instances, the process is called intrinsic bioremediation.
