THE UTILIZATION OF MICROORGANISMS AND HIGHER ORGANISMS FOR ARSENIC REMOVAL FROM CONTAMINATED WATER AND SOIL
Abstract
The biological treatment methods of waste water and wastes containig toxic metals are very interesting at present time. The advantages of these methods are low operating cost, energy consumption and low or no impact on the environment. In this article arsenic removal from environment by living organisms is described. This ability depends on the metabolism and the mechanism of detoxication in given type of organism. It is possible to consider four types of mechanisms: 1.reduction of sulphates, 2.biometylation, 3.biosorption and 4. accumulation by plants and animals.
The principle of the first method is reduction of sulphates to H2S which reacts with metallic ions forming insoluble sulfides. Biometylation is the basic reaction for arsenic detoxication in organisms. Methylated arsenic compounds are less toxic for organisms. Biosorption is an ability of different organisms to accumulate toxic metal ions in higher concentration than in surrouding water. Live organisms are able to accumulate metals from environment and store them in their own tissues. Arsenic stored in the fish, which are eatten by humans, is not biotransformed in human body, thus, it is not detrimental. Plants which are able to accumulate arsenic from soil are used for soil
cleaning.
There are different biochemical processes which take place in organisms in the presence of toxic metal. Some of them are dependent on metabolism and some are not, but they are often connected. If the detoxication process does not depend on the metabolism of cells, it is possible to use immobilized cells. These cells have very suitable characteristics for application the bioreactors and cleaning up of industial wastewater with high concentration of heavy metals.
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