Hot Microbes Cause Groundwater Cleanup Rethink in Australia

Engineering - Remediation, Mining - Environmental

Date posted: 08/05/16

CSIRO researchers have discovered that micro-organisms that help break down contaminants under the soil can actually get too hot for their own good. While investigating ways of cleaning up groundwater contamination, geoscientists examined how microbes break down contaminants under the soil surface and found that subsurface temperatures associated with microbial degradation can become too hot for the microbes to grow and consume the groundwater contaminants. This can slow down the clean up of the groundwater and even continue the spread of contamination. The new findings mean that researchers now have to rethink the way groundwater remediation systems are designed. CSIRO Colin Johnston, who is based in Perth, Western Australia, said the researchers were investigating how temperatures below the soil surface could be used as an indicator of the microbial degradation process associated with biosparging. Biosparging is a technique that injects air into polluted groundwater to enhance the degradation of contaminants. The contaminants are food to the microbes and the oxygen in the air helps the microbes unlock the energy in the food so that they metabolise and grow, consuming more contaminants and stopping the spread of the contamination. Observations of diesel fuel contamination showed that, at 3.5 meters below the ground surface, temperatures reached as high as 47 degrees C, Mr Johnston said. This is close to the 52 degrees C maximum temperature tolerated by the community of micro-organisms that naturally live in the soil at this depth and within the range where the growth of the community was suppressed. The growth of the soil micro-organism community can also be helped by adding nutrients. However, computer modelling confirmed that any attempts to further increase degradation of the contamination through the addition of nutrients had the potential to raise temperatures above the maximum for growth. Read on ..