Incorporating membrane gas diffusion into a membrane bioreactor for hydrogenotrophic denitrification of groundwater

Abstract

A hydrogenotrophic denitrification system, comprising a suspended growth membrane bioreactor (MBR) with membrane hydrogen gas diffusion, was developed to remove nitrate from groundwater. A hollow fiber gas permeable membrane module was designed for hydrogen delivery and a commercially available hollow fiber membrane module was used for solid/liquid separation. The MBR was operated at an SRT of 20 days and at room temperature. Four nitrate loading rates of 24, 48, 96 and 192 NO3(-)-N mg I(-1) d(-1) were applied to the system. As the nitrate loading was raised, pH increased due to increased denitrification and release of OH- ions. The oxidation reduction potential (ORP) remained fairly stable when full denitrification was achieved, but increased when nitrate loading rates reached 192 NO3(-)-N mg I(-1) d(-1) and residual nitrate was present in the reactor. Nitrate removal was complete (100%) in the first three nitrate loadings and 72% in the system with 192 NO3(-)-N mg I(-1) d(-1). Nitrate utilization rates of 30.6, 23.4, and 37.7 g NO3(-)-N m(-3) d(-1) were achieved in the first three loadings. Average effluent dissolved organic carbon (DOC) concentration of approximately 8 mg l(-1) was observed in all four nitrate loading regimes, possibly owing to the generation and release of soluble microbial bi-products (SMP).

Hydrogenotrophic denitrification of potable water: A review

“…In addition, the growth rate of autotrophic denitrifying bacteria ensures low biomass build-up and limited operating problems. Thus, hydrogenotrophic bacteria have been successfully used for drinking water nitrate elimination to acceptable levels either in pure [4][5][6][7] or in mixed-cultures [8][9][10][11][12][13][14][15].…”

Experimental and modelling study of drinking water hydrogenotrophic denitrification in packed-bed reactors

“…In recent years, many different technologies for hydrogenotrophic denitrification have been developed in an effort to solve the problem of NO 3 − in drinking water or wastewater, e.g., membrane reactors [3][4][5][6][7], bio-electrochemical systems [8], fluidized-bed reactors [9,10] and fixed-bed reactors [11,12]. Packed-bed reactors, provide a support medium for biofilm growth (higher biomass concentration), thus allowing the possibility of maintaining bacteria at high hydraulic and nitrogen loadings.…”

Evaluation of Performance and Microbial Community of NH4-N and NO3-N Bioreactors

“…Therefore, NO 3 -N was removed by hydrogenotrophic denitrification, as presented in Equation 4 [23]). From the results, it can be concluded that the NO 3 -N bioreactor can remove NO 3 -N from groundwater at a very high efficiency, and moreover, this system has advantages of being simple, easy to operate and requiring less H 2 comparing to the reactors used in previous studies [24,25] …”