Quantifying inorganic fouling in a membrane bioreactor treating nitrate-contaminated groundwater using hydrogen as energy source

A hydrogenotrophic denitrification system, which consisted of a sequencing batch membrane bioreactor, was evaluated for removal of nitrate from a synthetic groundwater feed. A hollow fiber microporous membrane diffuser was used for bubble-less diffusion of hydrogen into the bioreactor, and a membrane filter was used for separating the biomass from treated water. The nitrate loading of 0.328 kg N m⁻³ d⁻¹ was completely denitrified to below detectable levels; however, inorganic fouling of both membrane filter and diffuser occurred. The increase in pH during denitrification caused inorganic precipitation and clogging of the membranes. The foulant material was quantified as beta three calcium phosphate βCa₃ (PO₄)₂.