Doctoral defence: Sharvari Sunil Gadegaonkar "Microbial and environmental factors affecting the nitrate removal efficiency from water in bioelectrochemical systems"

On 23 August at 10:15 Sharvari Sunil Gadegaonkar will defend her doctoral thesis "Microbial and environmental factors affecting the nitrate removal efficiency from water in bioelectrochemical systems" for obtaining the degree of Doctor of Philosophy (in Environmental Technology).

Supervisors: Professor Ülo Mander (University of Tartu), Associate Professor Mikk Espenberg (University of Tartu)

Opponent: Dr Jamie Nivala (INRAE)

Summary
A large part of the pollution that resides in rural areas rely on groundwater for their water requirements, although this water remains unsafe to consume according to the standards set by EU. This is largely due to nitrate (NO3–), which contaminates water bodies and groundwater. Thus, it is essential to find ways to remediate this excessively contaminated water. NO3– is a difficult pollutant to eradicate due to its complex cycle and specific requirements essential for removal. Bioelectrochemical systems (BES) pose a special interest in removal of NO3 as they have displayed potential in treating NO3– successfully and completely remove it from the water. BES heavily rely on microbial activity in removal of NO3–, even though the BES design has been largely studied the knowledge on the role of microbiome remains limited. This study focused on NO3– removal capabilities and investigated the prevalent processes that are responsible for the NO3– transformation in two types of BES – a microbial electrochemical snorkel (MES) and a single-chambered carbon-deficient microbial electrosynthesis reactor (MESR). The current study focused on the microbes and related processes responsible for the NO3– removal. Likewise, the role of environmental factors and operational regimes has been analysed to suggest optimal design of BES for nitrate removal. This research states that BES support microbial process that can successfully eradicate NO3– removal and can also efficiently work by utilizing NO3– as fodder without relying on carbon. The BES microbiome structure shifts according to the NO3v concentrations and other substrates in the BES. It can be utilized for complete removal of NO3– with limited production of contaminants such as N2O, a potent greenhouse gas and stratospheric ozone depleter. The BES also aid microbial processes that can promote nitrogen removal from wastewater.