Summary
Pollutants' natural retention and degradation capacity is also known as "natural attenuation". Based on the assumption that natural self-purifying processes in water are not sufficient to satisfactorily limit the spread of refractory substances such as methyl tertiary butyl ether (MTBE), this approach is being called into question. MTBE is primarily used as an additive in petrol fuels and can therefore occur as a result of leaks at filling stations and get into the groundwater.
The aim of this subproject was to develop a cost-effective and practical in-situ method for modernisation of aquifers polluted with MTBE based on Enhanced Natural Attenuation (ENA). This was to be achieved by simultaneous adsorption of activated charcoal and anaerobic microbial degradation. The advantage of activated charcoal is that it not only enriches the pollutants, but also simultaneously provides a surface that can be colonised by the micro-organisms that degrade the pollutants. This concentrates adsorption and degradation of pollutants at a single point.
Results:
- Under denitrifying conditions, MTBE degradation was observed both in the laboratory and in the field. However, it is significantly slower than under aerobic conditions.
- It was observed that more easily utilisable carbon sources (e.g. BTEX: benzol, toluol, ethyl benzol, xoluole) cause inhibition of MTBE degradation.
- The adaptation phase can be very long, i.e. the time taken for the micro-organisms to adapt to the MTBE substrate under anaerobic conditions may be several months under some circumstances.
- In laboratory tests, abiotic MTBE degradation using catalysts (zeolites) is also possible under moderately acidic conditions (pH 3.4 - 4.7).
- The key factors influencing hydrolysis of MTBE are the pH value, the temperature and the composition of the water.
