Denitrifying bioreactors are an approach where solid carbon substrates are added into the flow path of contaminated water. These carbon (C) substrates (often fragmented wood-products) act as a C and energy source to support denitrification; the conversion of nitrate (NO3−) to nitrogen gases. Denitrifying bioreactors that employ a lignocellulosic wood chip medium contained within a saturated (anoxic) zone are relatively new technology that can be implemented at the local level to manage residential non-point nitrogen sources. In these systems, wood chips serve as a microbial biofilm support and provide a constant source of organic substrate required for denitrification. Denitrifying wood chip bioreactors for stormwater management include biofilters and bioretention systems modified to include an internal water storage zone; for on-site wastewater, they include upflow packed bed reactors, permeable reactive barriers, and submerged wetlands. Laboratory studies have shown that these bioreactors can achieve nitrate removal efficiencies as high as 80–100% but could provide more fundamental insight into system design and performance. Denitrifying bioreactors enhance the natural process of denitrification in a practical way to treat nitrate-nitrogen (N) in a variety of N-laden water matrices. The design and construction of bioreactors for treatment of subsurface drainage. Denitrifying woodchip bioreactors are capable of removing sediment via the physical process of filtration, but this capability can eventually hinder N removal performance.

Nitrification in a completely stirred tank reactor treating the liquid phase of digestate: The way towards rational use of nitrogen. The continuous stirred tank bioreactor (CSTB) is the other suspended growth process and is based on a conventional mixed-flow reactor (MFR) or continuous stirred tank reactor (CSTR). Stirred tank bioreactors (STBRs) are the reactors most widely employed for culturing of biological agents such as cells, enzymes, or antibodies. They are contactors where the well-mixed among phases is obtained mainly by internal mechanical agitation. The impeller must provide sufficiently rapid agitation to disperse all compounds and achieve an effectively homogeneous concentration inside the bioreactor

Morvarid Larijani , brief answers to your questions:

1) Continuous denitrification in bioreactors is better than the batch process (vials, flasks) for several reasons, e.g., a) it provides operational control over bioprocess (optimal pH, T, removal of toxic byproducts), b) it is faster (no lag-time as in batch process ), and c) deeper cleaning of wastewater from NO3.

2) Contrary to anaerobic denitrification, nitrification is the aerobic process of NH4 oxidation to NO2/NO3 by autotrophic bacteria. There is also the heterotrophic nitrification recently discovered in the wastewater process. Mechanisms are different, see textbooks, e.g., Brocks Biology of Microorganisms.

Continuous denitrification is definitely the better way than the discontinuous system. The following article might help you on this aspect:

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