Hydrogenotrophic denitrification of drinking water using a hollow fibre membrane bioreactor

The objective of this research was to investigate the performance of a holl ow fibre membrane bioreactor (HFMB) for hydrogenotrophic denitrification of contaminated drinking water. in the HFMB, H-2 flows through the lumen of t he hydrophobic hollow fibres and diffuses to an attached H-2 oxidizing biof ilm. Nitrate in the contaminated water serves as an electron acceptor. A hy drogenotrophic denitrifying culture was enriched from a wastewater seed. Ba tch culture experiments were conducted to compare heterotrophic (methanol a s electron donor) and hydrogenotrophic denitrification rates and to investi gate the conditions required for the HFMB studies. The batch cultures demon strated mixotrophy, with denitrification rates of 30 g NO3--N m(-3) d(-1) f or heterotrophic and 18 g NO3--N m(-3) d(-1) for hydrogenotrophic condition s. A laboratory-scale HFMB was constructed that utilized 2,400 polypropylen e hollow fibres with an inner diameter of 200 mum, an outer diameter of 250 mum and a 0.05 mum pore size. After a 70-day start-up period, the NO3- loa ding rate was gradually increased over a three-month period. The NO, utiliz ation rate reached a maximum of 770 g NO3--N m(-3) d(-1) at an influent NO3 - concentration of 145 mg NO3--N l(-1) and a hydraulic residence time of 4. 1 hours. Influent NO3- concentrations of up to 200 mg NO3--N l(-1) were alm ost completely denitrified. Tests with contaminated water from the Cape Cod aquifer resulted in an increase in product water turbidity and dissolved o rganic carbon (DOC) concentrations.