Biological nitrate removal from groundwater by an aerobic granular technology to supply drinking water at pilot-scale

Granular aerobic sludge systems have been a very efficient technology in urban and industrial wastewater treatment. In this research, a novel modification of aerobic granular sludge technology was developed for the treatment of nitrate-polluted groundwater, adding very low concentrations of a solution based on carbon and oligoelements in the groundwater to promote the growth of denitrifying microorganisms, avoiding expensive technologies to supply drinking water in small urban nuclei. The denitrification process was successfully reached at 0.15 g C2H3NaO2 L-1, meeting the Nitrate Directive of Europe for drinking water. The granular biomass was compact and dense with average values of mean size and settling velocity of 4.0 mm and 40 mh(-1), respectively. The prokaryotic and eukaryotic communities were studied by massive parallel sequencing techniques. The dominant prokaryotic phylotypes were related to influent composition, belonging to Comamonadaceae, Rhizobiales, Acinetobacter and Pseudomonas. The dominant eukaryotic phylotype was affiliated to Haematococcus microalgae. The diversity and evenness were high, regardless of influent composition. This study demonstrates support for the innovation of aerobic granular sludge technology application in terms of performance, operation, granular maturation and stability, as well as the role of denitrifying microorganisms to implement a low-cost, easy-to-use and maintain, environmental-friendly drinking water technology for rural populations.

Automated summary

A novel modification of aerobic granular sludge technology was developed in this research for the treatment of nitrate-polluted groundwater, achieving successful denitrification process. The study demonstrated high diversity and evenness in both prokaryotic and eukaryotic communities.