Biopurification prototype removes 90% of indoor VOCs and PAHs

Researchers in Chile have designed a prototype indoor air purification system which uses microorganisms to capture and degrade pollutants, with efficiencies above 90%.

The study focused on the removal of volatile organic compounds (VOCs) from household products such as paint, and polycyclic aromatic hydrocarbons (PAHs) from wood-burning. Research in Athens, Greece has found that a third (31%) of PAH urban air pollution is caused by wood-burning.

The problem faced in the removal of such pollutants is that, in the drive to make buildings more energy efficient, air flow – which would other wise diminish the threat of VOCs and PAHs – is reduced in order to keep warm air indoors. 

Currently adsorption methods – which use an activated carbon filter to capture the impurities – represent the popular current solution but the activated carbon itself eventually needs replacing.

Alberto Vergara-Fernández, Founder of Green Technologies Research Group at Universidad de los Andes in Chile and corresponding author of the study said: ‘The first motivation was the search for a treatment system that was easy to install and did not depend on new pipes and installations for its use. In addition, it can be applied in different confined environments, from domestic to industrial under the same principle.’

The prototype uses a biofiltration system which pass air through a thin film containing immobilised bacteria and fungi. 

An initial microbial population for the system was grown from the fungus fusarium solani and the bacterium rhodococcus erythropolis. After eight months of continuous performance, further species were captured from the air, demonstrating the potential of the prototype for retaining airborne bacteria and fungi.

Vergara-Fernández explained how the high specialisation of the microbial flora developed in the bioreactor contributed to the efficiency of the purification system. ‘One of the main findings was the possibility of developing a highly specialised microbial consortium, which allows obtaining high elimination capacities in very short periods of operation time, maintaining good elimination capacities.

‘The main difference is related to the destruction capacity of the contaminants rather than the transfer of them to another phase, from which they must also be eliminated. Given the degradation of the contaminants and not just adsorption, the lifetime of the support is much longer, maintaining its high removal efficiency.’

The challenge that remains is to develop such a system that is small enough to be practical:  ‘The main challenges and limitations of the biopurification system, on which we are currently working, is the reduction in the dimensions of the equipment that makes up the system. We are developing a hybrid system that combines physical-chemical and biological technology, with the aim of reducing the inlet flows to the biological system’.