Nitrate removal by simultaneous sulfur utilizing autotrophic and heterotrophic denitrification under different organics and alkalinity conditions: batch experiments

The effect of various organic compounds were tested using lab-scale batch reactors. At sufficient alkalinity, the initial nitrate nitrogen concentration of 100 mg/L was completely reduced in all batch reactors. Sulfate production decreased by the addition of organics. The concentration range of organics used in this experiment did not inhibit autotrophic denitrification except for propionate. Propionate inhibited autotrophic denitrification a little, indicated by a lower sulfate production rate. Biomass in suspension increased with higher initial organic concentrations, showing higher DOC consumption. As the concentration of organics increased, alkalinity increased accordingly. Under the conditions of low alkalinity, in the case of a control reactor without organics, only about 30% of the initial nitrate was reduced. With half the theoretically required dosage of methanol, the denitrification rates increased slightly. When ethanol, acetate, and propionate were used, denitrification went to completion. When excess organics was added, however, sulfate production was significantly decreased. Interestingly, even when small amounts of organics were added, autotrophic denitrification was promoted as indicated by the sulfate production.

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Experimental effect of medium ratio on removal efficiency of nitrate nitrogen in groundwater by zero-valent iron, activated carbon and zeolite

Water Science & Technology Water Supply ◽

10.2166/ws.2019.036 ◽

2019 ◽

Vol 19 (6) ◽

pp. 1636-1642

Author(s):

Sizhi Cao ◽

Peigui Liu ◽

Mingchao Liu ◽

Gang Wang ◽

Zaili Li ◽

...

Keyword(s):

Activated Carbon ◽

Nitrate Nitrogen ◽

Nitrogen Concentration ◽

Nitrate Removal ◽

Ammonia Nitrogen ◽

Coarse Sand ◽

Zero Valent Iron ◽

Nitrite Nitrogen ◽

Rich Solution ◽

Set Up

Abstract In this study, column experiments in the laboratory were set up to examine how the concentrations of nitrate nitrogen, nitrite nitrogen, and ammonia nitrogen changed when a nitrate-rich solution was passed through a medium comprising zero-valent iron, activated carbon, zeolite, and coarse sand. We varied the proportions of the components of the medium to determine how it influenced the nitrate removal and nitrogen fractions. Three different scenarios were used, with: (1) iron, activated carbon, and coarse sand at a ratio of 3:1:6; (2) iron, activated carbon, and zeolite at a ratio of 3:1:6; and (3) iron, activated carbon, and zeolite at a ratio of 3:3:4. The nitrate nitrogen concentration decreased from 25 mg/L to 2 mg/L in the first scenario. Removal was better when zeolite was added to the medium as most of the nitrate nitrogen broke down to ammonia nitrogen, with nitrite nitrogen as an intermediate product. The results of the tests showed that nitrate removal was best when the medium was iron, activated carbon, and zeolite, mixed at a ratio of 3:1:6. This study provides a scientific reference for in situ remediation of nitrate pollution in groundwater.

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Nitrate Removal from Actual Wastewater by Coupling Sulfur-Based Autotrophic and Heterotrophic Denitrification under Different Influent Concentrations

Water ◽

10.3390/w13202913 ◽

2021 ◽

Vol 13 (20) ◽

pp. 2913

Author(s):

Feng Liu ◽

Suqin Wang ◽

Xuezhi Zhang ◽

Feiyue Qian ◽

Yaobing Wang ◽

...

Keyword(s):

Removal Efficiency ◽

Nitrate Removal ◽

Operating Conditions ◽

Coupled Systems ◽

Polluted Water ◽

Sequencing Analysis ◽

Autotrophic Denitrification ◽

Actual Wastewater ◽

Denitrification Process ◽

Heterotrophic Denitrification

Contamination of wastewater with organic-limited nitrates has become an urgent problem in wastewater treatment. The cooperating heterotrophic with sulfur autotrophic denitrification is an alternative process and the efficiency has been assessed in many studies treating simulated wastewater under different operating conditions. However, due to the complex and diverse nature of actual wastewater, more studies treating actual wastewater are still needed to evaluate the feasibility of collaborative denitrification. In this study, lab-scale experiments were performed with actual nitrate polluted water of two different concentrations, with glucose and sodium thiosulfate introduced as mixed electron donors in the coupling sulfur-based autotrophic and heterotrophic denitrification. Results showed that the optimum denitrification performance was exhibited when the influent substrate mass ratio of C/N/S was 1.3/1/1.9, with a maximum denitrification rate of 3.52 kg NO3−-N/(m3 day) and nitrate removal efficiency of 93% in the coupled systems. Illumina high-throughput sequencing analysis revealed that autotrophic, facultative, and heterotrophic bacteria jointly contributed to high nitrogen removal efficiency. The autotrophic denitrification maintained as the predominant process, while the second most prevalent denitrification process gradually changed from heterotrophic to facultative with the increase of influent concentration at optimum C/N/S ratio conditions. Furthermore, the initiation of dissimilatory nitrate reduction to ammonium (DNRA) was very pivotal in promoting the entire denitrification process. These results suggested that sulfur-based autotrophic coupled with heterotrophic denitrifying process is an alternative and promising method to treat nitrate containing wastewater.

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Groundwater denitrification with alternative carbon sources

Water Science & Technology ◽

10.2166/wst.1998.0257 ◽

1998 ◽

Vol 38 (6) ◽

pp. 237-243 ◽

Cited By ~ 22

Author(s):

A. Mohseni-Bandpi ◽

D. J. Elliott

Keyword(s):

Acetic Acid ◽

Carbon Source ◽

Nitrate Nitrogen ◽

Nitrogen Concentration ◽

Nitrate Removal ◽

Carbon Sources ◽

Pilot Scale ◽

Rotating Biological Contactor ◽

Nitrogen Ratio ◽

Biological Nitrate Removal

A pilot scale rotating biological contactor (RBC) was used to investigate the removal of nitrate-nitrogen from groundwater using three different carbon sources, i.e., methanol, ethanol and acetic acid. Optimum carbon sources to influent nitrate-nitrogen ratio were established by varying the influent concentration of carbon sources. The optimum ratio of methanol, ethanol and acetic acid to nitrate-nitrogen ratios were found to be 2.9, 2.35 and 4.3 respectively. The nitrate-nitrogen removal efficiency averaged 93, 91 and 98 for methanol, ethanol and acetic acid respectively at a loading rate of 76 mg/m2.h. The results of this study show that the acetic acid is the most efficient carbon source for removal of nitrate-nitrogen. Effluent nitrite-nitrogen concentration was minimum for acetic acid as compared with ethanol and methanol. The effluent contained minimum suspended solids and turbidity for methanol as a carbon source. The results of this study indicate that biological nitrate removal using a RBC is a reliable and stable system under all the three carbon sources. The denitrified water in all cases requires some post treatment to oxidise the residual carbon source and remove biomass before distribution.

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Nitrate removal from wastewater generated in wet Flue Gas Desulphurisation Systems (FGD) in coal-fired power generation using the heterotrophic denitrification method

Ochrona Srodowiska i Zasobów Naturalnych ◽

10.2478/oszn-2020-0012 ◽

2020 ◽

Vol 31 (3) ◽

pp. 27-34

Author(s):

Krzysztof Iskra ◽

Łukasz Krawczyk ◽

Jan M. Miodoński ◽

Dominika Wierzbicka-Kopertowska

Keyword(s):

Flue Gas ◽

Nitrate Nitrogen ◽

Nitrate Removal ◽

Oxygen Demand ◽

Active Surface ◽

Adaptation Period ◽

Technological Parameters ◽

Rate Test ◽

High Degree ◽

Heterotrophic Denitrification

Abstract The article presents an assessment of the possibilities of using the heterotrophic denitrification process to remove nitrates from wastewater produced in wet flue gas desulphurisation (FGD) installations and also its optimization in the scope of basic technological parameters. This kind of wastewater is characterized by high salinity (even up to 40,000 g/m3), high temperature (up to 50°C) and low biodegradability, which is expressed by the biochemical oxygen demand (BOD5). The experimental rig consisted of a storage tank and a bioreactor in the form of a bed with an apparatus for measuring basic parameters (temperature, pH, nitrate nitrogen). After an initial adaptation period, a high degree of nitrate nitrogen removal from wastewater (exceeding 95% reduction) was obtained with a reaction time of 180 minutes during the denitrification rate test (NUR). It was also determined that the optimal loading range of the active surface of the bed of 300 m2/m3 should be between 1.5–2.5 gN-NO3/m2·d. The results of the study show that when the required conditions for the development of microorganisms are provided, it is possible to fully adapt the denitrification biomass to the adverse composition of wastewater from wet FGD unit.

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The effects of pH and addition of an organic buffer (HEPES) on nitrate transformation in Fe0-water systems

Water Science & Technology ◽

10.2166/wst.1998.0283 ◽

1998 ◽

Vol 38 (7) ◽

pp. 107-115 ◽

Cited By ~ 21

Author(s):

Lara L. Zawaideh ◽

Tian C. Zhang

Keyword(s):

Nitrate Nitrogen ◽

Batch Reactor ◽

Nitrate Removal ◽

Zero Valent Iron ◽

Contaminated Water ◽

Batch Reactors ◽

Operational Parameters ◽

Wide Ph Range ◽

Effects Of Ph ◽

Ph Range

The feasibility of using zero-valent iron (Fe0) powder to remediate nitrate-contaminated water was studied using bench-scale batch reactors. Operational parameters, such as Fe0 dosage (w/v), initial concentration of nitrate-nitrogen, pH, and the use of an organic buffer (HEPES) were studied, specifically focusing on the effects of pH and the addition of HEPES on nitrate transformation using zero-valent iron powder. Nitrate-nitrogen was removed by 94% when 0.01M of HEPES was added to a non-shaking batch reactor containing 20 mg/l nitrate-nitrogen and 4% (w/v) of Fe0. Shaking was proved to be more efficient than no shaking. Using the response surface methodology it was found that nitrate removal was closely related to pH. At low pH (e.g., pH < 2), the nitrate removal was fast and efficient (95% to 100%). At high pH (e.g., pH > 11), the transformation of nitrate was fast and efficient only for low concentration of nitrate in the Fe0-H2O system. At normal pH range (pH = 6 to 8), nitrate removal was usually lower than 50% without buffer treatment. The addition of the organic buffer (HEPES) could greatly enhance the nitrate transformation in a wide pH range (e.g., pH = 2 to 11).

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Hydrilla verticillata–Sulfur-Based Heterotrophic and Autotrophic Denitrification Process for Nitrate-Rich Agricultural Runoff Treatment

International Journal of Environmental Research and Public Health ◽

10.3390/ijerph17051574 ◽

2020 ◽

Vol 17 (5) ◽

pp. 1574

Author(s):

Qianyu Hang ◽

Haiyan Wang ◽

Zan He ◽

Weiyang Dong ◽

Zhaosheng Chu ◽

...

Keyword(s):

Removal Efficiency ◽

Nitrate Removal ◽

Hydrilla Verticillata ◽

Agricultural Runoff ◽

Denitrification Rate ◽

Phase Iii ◽

Autotrophic Denitrification ◽

N Removal ◽

Significant Difference ◽

Heterotrophic Denitrification

Hydrilla verticillata–sulfur-based heterotrophic and autotrophic denitrification (HSHAD) process was developed in free water surface constructed wetland mesocosms for the treatment of nitrate-rich agricultural runoff with low chemical oxygen demand/total nitrogen (C/N) ratio, whose feasibility and mechanism were extensively studied and compared with those of H. verticillata heterotrophic denitrification (HHD) mesocosms through a 273-day operation. The results showed that the heterotrophic and autotrophic denitrification can be combined successfully in HSHAD mesocosms, and achieve satisfactory nitrate removal performance. The average NO3−-N removal efficiency and denitrification rate of HSHAD were 94.4% and 1.3 g NO3−-N m−3·d−1 in steady phase II (7–118 d). Most nitrate was reduced by heterotrophic denitrification with sufficient organic carbon in phase I (0–6 d) and II, i.e., the C/N ratio exceeded 4.0, and no significant difference of nitrate removal capacity was observed between HSHAD and HHD mesocosms. During phase III (119–273 d), sulfur autotrophic denitrification gradually dominated the HSHAD process with the C/N ratio less than 4.0, and HSHAD mesocosms obtained higher NO3−-N removal efficiency and denitrification rate (79.1% and 1.1 g NO3−-N m−3·d−1) than HHD mesocosms (65.3% and 1.0 g NO3−-N m−3·d−1). As a whole, HSHAD mesocosms removed 58.8 mg NO3−-N more than HHD mesocosms. pH fluctuated between 6.9–9.0 without any pH buffer. In general, HSHAD mesocosms were more stable and efficient than HHD mesocosms for NO3−-N removal from agricultural runoff during long-term operation. The denitrificans containing narG (1.67 × 108 ± 1.28 × 107 copies g−1 mixture-soil−1), nirS (8.25 × 107 ± 8.95 × 106 copies g−1 mixture-soil−1), and nosZ (1.56 × 106 ± 1.60 × 105 copies g−1 mixture-soil−1) of litter bags and bottoms in HSHAD were higher than those in HHD, which indicated that the combined heterotrophic and autotrophic denitrification can increase the abundance of denitrificans containing narG, nirS, and nosZ, thus leading to better denitrification performance.

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Optimal operations for groundwater denitrification of drinking water using heterotrophic biological denitrification process

Water Science & Technology Water Supply ◽

10.2166/ws.2006.060 ◽

2006 ◽

Vol 6 (2) ◽

pp. 125-130

Author(s):

C.-H. Hung ◽

K.-H. Tsai ◽

Y.-K. Su ◽

C.-M. Liang ◽

M.-H. Su ◽

...

Keyword(s):

Drinking Water ◽

Removal Efficiency ◽

Nitrate Removal ◽

Drinking Water Treatment ◽

Nitrate Content ◽

Source Water ◽

Nitrogen Gas ◽

Negative Effect ◽

Denitrification Process ◽

Heterotrophic Denitrification

Due to the extensive application of artificial nitrogen-based fertilizers on land, groundwater from the central part of Taiwan faces problems of increasing concentrations of nitrate, which were measured to be well above 30 mg/L all year round. For meeting the 10 mg/L nitrate standard, optimal operations for a heterotrophic denitrification pilot plant designed for drinking water treatment was investigated. Ethanol and phosphate were added for bacteria growing on anthracite to convert nitrate to nitrogen gas. Results showed that presence of high dissolved oxygen (around 4 mg/L) in the source water did not have a significantly negative effect on nitrogen removal. When operated under a C/N ratio of 1.88, which was recommended in the literature, nitrate removal efficiency was measured to be around 70%, sometimes up to 90%. However, the reactor often underwent severe clogging problems. When operated under C/N ratio of 1.0, denitrification efficiency decreased significantly to 30%. Finally, when operated under C/N ratio of 1.5, the nitrate content of the influent was almost completely reduced at the first one-third part of the bioreactor with an overall removal efficiency of 89–91%. Another advantage for operating with a C/N ratio of 1.5 is that only one-third of the biosolids was produced compared to a C/N value of 1.88.

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An equation for the empirical design of anoxic zones used to eliminate rising sludges at nitrifying activated sludge plants

Water Science & Technology ◽

10.2166/wst.1996.0070 ◽

1996 ◽

Vol 33 (3) ◽

pp. 185-194 ◽

Cited By ~ 1

Author(s):

M. Sarioglu ◽

N. Horan

Keyword(s):

Activated Sludge ◽

Empirical Equation ◽

Nitrate Nitrogen ◽

Critical Concentration ◽

Settling Tank ◽

Limited Information ◽

Batch Experiments ◽

Anoxic Zone ◽

Secondary Settling ◽

Anoxic Zones

Anoxic zones are designed for the removal of nitrogen in nitrifying activated sludge plants. This can be carried out either to achieve a nitrogen discharge consent or to eliminate the problem of rising sludges. The rising sludge problem is mostly encountered in medium and small size plants in warm conditions and there is limited information as to the appropriate design of anoxic zones to protect against rising sludges in the secondary sedimentation tanks. Therefore a series of batch experiments were undertaken in order to establish the critical concentration of nitrate-nitrogen which causes rising sludge in the secondary settling tank and the effect of environmental factors such as temperature (15°C to 30°C) and residual carbon source (100 to 600 mg/1 COD) were examined. Based on the results of these experiments an empirical equation was presented which can be used to size an anoxic zone to eliminate rising sludges. The application of this equation at full-scale plants is discussed.

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