SENSE Ph.D. award for Nora Sutton
Former ETE Ph.D. student Dr. Nora Sutton received the 2015 SENSE Ph.D. award for her thesis Microb biological and geochemical dynamics of the sub-subsurface:chemical oxidation and bioremediation of organic contaminants’ during the yearly SENSE summer symposium.
The jury particularly appreciated her fundamental scientific approach on the very practical problem of soil pollution. In addition, the Jury valued her international collaborations with both scientists and local authorities, thereby bridging gaps between engineering and practice.
Cleaning contaminated soil
Soil polluted with organic contaminants poses a serious health and environmental risk. People may be exposed to these chemicals by inhalation or direct contact. In addition, these compounds may disperse in the environment, contaminating groundwater and water supplies, while seriously impacting the ecosystem. Therefore, many governments prioritize soil cleaning. Traditional methods to clean soil focus on excavation and disposal of the polluted soil. Recently, advances have been made in in situ techniques which clean the soil in place without excavation. During her Ph.D. research, Sutton researched chemical and biological soil treatment. She combined these methods and developed a new procedure using both chemicals and microorganisms. This resulted in a quicker, more efficient and more environmental friendly cleaning method.
Organic pollutants in soils can effectively be removed using chemical oxidants. The process is quick, but relatively expensive. In addition, chemical oxidants kill bacteria and may degrade soil organic matter, resulting in a clean, but poor soil. Sutton investigated the possibility to clean soil, using microorganisms following chemical oxidation. This combined approach could iimprove overall soil-cleaning procedures, because fewer chemicals are needed: chemical oxidants only have to degrade part of the contaminants, while bacteria may degrade remaining pollutants. A challenging and ‘out of the box’ idea, since the general idea has always been that oxidizing chemicals and microorganisms do not mix. ‘Some chemical treatments result in very acidic or alkaline groundwater, incompatible with bacterial growth’, Sutton explains. ‘Also, chemicals damage the bacterial cell walls, thereby killing them.’
Best of two worlds
During her search for a combined chemical-biological cleaning procedure, Sutton first treated contaminated soil with strong oxidizers. When the oxidative reaction had stopped, bacteria recovered remarkably quickly. ‘Many bacteria proved to be surprisingly resilient towards chemical oxidation’, Sutton explains. ‘In some cases the oxidant degraded organic matter and released nutrients, creating favorable growth conditions for bacteria.’ Her results proved that chemical and bacterial soil cleaning can effectively be combined, resulting in a relatively quick soil cleaning, using fewer chemicals. As a result, soil damage is limited and costs for chemicals are reduced. Sutton truly succeeded in combining the best of two worlds.
Sutton is continuing her work on cleaning of pollutants with bacteria. She now works as a postdoc researching the use of bacteria to remove micropollutants such as pesticides and pharmaceuticals in different portions of the water cycle.