Electron donors for autotrophic denitrification

This article summarizes several developed and industrial technologies for nitrate removal from drinking water, including physicochemical and biological techniques, with a focus on autotrophic nitrate removal Approaches are primarily classified into separation-based and elimination-based methods according to the fate of the nitrate in water treatment Biological denitrification as a cost-effective and promising method of biological nitrate elimination is reviewed in terms of its removal process, applicability, efficiency, and associated disadvantages The various pathways during biological nitrate removal, including assimilatory and dissimilatory nitrate reduction, are also explained A comparative study was carried out to provide a better understanding of the advantages and disadvantages of autotrophic and heterotrophic denitrification Sulfur-based and hydrogen-based denitrifications, which are the most common autotrophic processes of nitrate removal, are reviewed with the aim of presenting the salient features of hydrogenotrophic denitrification along with some drawbacks of the technology and research areas in which it could be used but currently is not The application of algae-based water treatment is also introduced as a nature-inspired approach that may broaden future horizons of nitrate removal technology

Nitrate removal from drinking water with a focus on biological methods: a review

High sulfide concentrations in biogas are a major problem associated with the anaerobic treatment of sulfate-rich substrates. It causes the corrosion of concrete and steel, compromises the functions of cogeneration units, produces the emissions of unpleasant odors, and is toxic to humans. Microaeration, i.e. the dosing of small amounts of air (oxygen) into an anaerobic digester, is a highly efficient, simple and economically feasible technique for hydrogen sulfide removal from biogas. Due to microaeration, sulfide is oxidized to elemental sulfur by the action of sulfide oxidizing bacteria. This process takes place directly in the digester. This paper reviews the most important aspects and recent developments of microaeration technology. It describes the basic principles (microbiology, chemistry) of microaeration and the key technological factors influencing microaeration. Other aspects such as process economy, mathematical modelling and control strategies are discussed as well. Besides its advantages, the limitations of microaeration such as partial oxidation of soluble substrate, clogging the walls and pipes with elemental sulfur or toxicity to methanogens are pointed out as well. An integrated mathematical model describing microaeration has not been developed so far and remains an important research gap.

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Microaeration for hydrogen sulfide removal during anaerobic treatment: a review

This paper reviews both heterotrophic and autotrophic processes for the removal of nitrate from water supplies. The most commonly used carbon sources in heterotrophic denitrification are methanol, ethanol and acetic acid. Process performance for each feed stock is compared with particular reference nitrate and nitrite residual and to toxicity potential. Autotrophic nitrate removal has the advantages of not requiring an organic carbon source; however the slow growth rate of autotrophic bacteria and low nitrate removal rate have contributed to the fact that relatively few full scale plants are in operation at the present time.

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Biological nitrate removal processes from drinking water supply-a review

Chemolithotrophic denitrification in biofilm reactors

Sulfur-limestone was used in the autotrophic denitrification process to remove the nitrate and nitrite in a lab scale upflow biofilter. Synthetic water with four levels of nitrate and nitrite concentrations of 10, 40, 70 and 100 mg N/L was tested. When treating the low concentration of nitrate- or nitrite-contaminated water (10, 40 mg N/L), a high removal rate of about 90% was achieved at the hydraulic retention time (HRT) of 3 hr and temperature of 20–25°C. At the same HRT, 50% of the nitrate or nitrite could be removed even at the low temperature of 5–10°C. For the higher concentration nitrate and nitrite (70, 100 mg N/L), longer HRT was required. The batch test indicated that influent concentration, HRT and temperature are important factors affecting the denitrification efficiency. Molecular analysis implied that nitrate and nitrite were denitrified into nitrogen by the same microorganisms. The sequential two-step-reactions from nitrate to nitrite and from nitrite to the next-step product might have taken place in the same cell during the autotrophic denitrification process.

Yue Zhang

Papers

Autotrophic denitrification for nitrate and nitrite removal using sulfur-limestone.