Nitrate Nitrogen Removal Efficiencies Research Articles

Optimizing stormwater runoff treatment: The role of two-stage tandem rain gardens

Regarded as a superior urban stormwater management solution, rain gardens can effectively store rainfall runoff and purify water quality. However, the efficiency of traditional rain gardens (TRG) in regulating runoff and removing nitrogen and phosphorus varies under different hydrological conditions. In this study, the TRG was retrofitted to construct a two-stage tandem rain garden (TTRG). Based on the experimental monitoring of rain gardens under natural rainfall from 2011 to 2013, results indicated a significantly higher runoff reduction capacity for the TTRG compared to the traditional garden (p < 0.05), with average runoff and peak flow reduction rates increasing by 42.8% and 36.2%, respectively. Rainfall characteristics significantly impacted the runoff reduction of the TRG (p < 0.05), but not the TTRG (p > 0.05), demonstrating the enhanced control and stability of the TTRG in managing rainfall runoff. The concentration removal efficiency of nitrate nitrogen (NO3--N) was significantly improved (p < 0.05), whereas the total phosphorus (TP), ammonium nitrogen (NH3-N) and total nitrogen (TN) were not significantly changed (p > 0.05). The first-order kinetic model was used to fit the removal effect of different pollutants before and after retrofitting the rain garden, and the removal of NO3--N by the TTRG was better than that of the TRG. The TTRG showed significantly higher load removal efficiencies for TP, NO3--N, and NH3-N compared to TRG (p < 0.05), with average load removal rates increasing by 49.92%, 75.02%, and 14.81%, respectively. The TTRG can regulate urban rainfall runoff more efficiently and stably. By changing the water flow path in the rain garden, the TTRG has a better runoff reduction ability and pollutant purification effect.

Action Mechanism of Bacillus on Microalgae During Nitrogen Metabolism in Urban Tailwater

To improve deep denitrification of black and odorous water and improve the quality of surface water, we studied the characteristics of nitrogen metabolism and denitrification of urban tailwater by microalgae (Z), Bacillus (Y), and Bacillus microalgae (ZY). The results showed that there was a good removal effect of ammonia nitrogen of group Z and group ZY in urban tailwater. The degradation rate of both groups reached 95%. The best effect on the removal of nitrite nitrogen was of group Z in urban tailwater. The combined action of Bacillus and Micrococcus played a relatively strong and stable effect on the conversion of nitrite nitrogen to nitrate nitrogen in the nitrogen cycle reaction. Bacillus could effectively remove nitrate nitrogen and improve the removal efficiency of nitrate nitrogen by microalgae. Best removal effect of nitrate nitrogen was observed in group ZY in urban tailwater, with a degradation rate as high as 99%, in which the nitrate nitrogen was removed almost completely. The Bacteria with high proportions in Z were Chroococcidiopsis_PCC_7203 (24.38%), uncultured_bacterium-g_norank_f_A4b (23.65%), Exiguobacteriu (7.09%), Leptolyngbya_PCC-6306(9.41%), and Bacillus (1.99%). The bacteria with high proportions in ZY were Brevibacillus (22.94%), Clostridium (8.78%), and Bacillus (4.88%), and the proportion of Chroococcidiopsis_PCC_7203 was only 7.84% in ZY, which was considerably lower than that in Z samples. The conclusions were as follows:microalgae could effectively remove ammonia nitrogen in the system. Bacillus and microalgae had very good removal effect of ammonia nitrogen and nitrate nitrogen. During the nitrogen removal of black and odorous water by algae, the Bacillus inhibited the excessive growth of microalgae and prevented eutrophication and black odor in water. This study can provide data support for the deep treatment of urban tail water and prevention of surface water eutrophication.

Comparative investigation on heterotrophic denitrification driven by different biodegradable polymers for nitrate removal in mariculture wastewater: Organic carbon release, denitrification performance, and microbial community.

Heterotrophic denitrification is widely studied to purify freshwater wastewater, but its application to seawater wastewater is rarely reported. In this study, two types of agricultural wastes and two types of synthetic polymers were selected as solid carbon sources in denitrification process to explore their effects on the purification capacity of low-C/N marine recirculating aquaculture wastewater (NO3 --N 30 mg/L, salinity 32‰). The surface properties of reed straw (RS), corn cob (CC), polycaprolactone (PCL) and poly3-hydroxybutyrate-hydroxypropionate (PHBV) were evaluated by Brunauer-Emmett-Teller, Scanning electron microscope and Fourier-transform infrared spectroscopy. Short-chain fatty acids, dissolved organic carbon (DOC), and chemical oxygen demand (COD) equivalents were used to analyze the carbon release capacity. Results showed that agricultural waste had higher carbon release capacity than PCL and PHBV. The cumulative DOC and COD of agricultural waste were 0.56-12.65 and 1.15-18.75 mg/g, respectively, while those for synthetic polymers were 0.07-1.473 and 0.045-1.425 mg/g, respectively. The removal efficiency of nitrate nitrogen (NO3 --N) was CC 70.80%, PCL 53.64%, RS 42.51%, and PHBV 41.35%. Microbial community analysis showed that Proteobacteria and Firmicutes were the most abundant phyla in agricultural wastes and biodegradable natural or synthetic polymers. Quantitative real-time PCR indicated the conversion from nitrate to nitrogen was achieved in all four carbon source systems, and all six genes had the highest copy number in CC. The contents of medium nitrate reductase, nitrite reductase and nitrous oxide reductase genes in agricultural wastes were higher than those in synthetic polymers. In summary, CC is an ideal carbon source for denitrification technology to purify low C/N recirculating mariculture wastewater.

Enhanced nutrient removal of agricultural waste-pyrite bioretention system for stormwater pollution treatment

Pyrite as filler applied to bioretention cells has the potential for simultaneous nitrogen and phosphorus removal, but its low electron supply rate cannot adapt to the demand for nitrogen and phosphorus removal under high rainfall intensity and continuous rainfall conditions. In this study, novel pyrite-based bioretention cells with agricultural waste amendment (corn cobs, rice husks, wood chips) were developed, and the pollution removal of each cell was evaluated under simulated complex rainfall conditions. The bioretention cell amended with woodchips achieved significantly higher efficiency and stability for dissolved nutrient removal compared with the pyrite bioretention cell. Its average removal efficiency of nitrate nitrogen, total nitrogen, and phosphate phosphorus was 69.39%, 45.60%, and 60.01% higher than that of the control group. The average chemical oxygen demand (COD) and total iron (TFe) concentrations in the effluent were slightly higher than those from the pyrite bioretention cell but were significantly lower than those from the corn cob and the rice husk-pyrite bioretention cell. Microbiological analysis revealed that the addition of woodchips significantly increased the relative abundance of Thiobacillus (the main functional genus of autotrophic denitrification) and Thauera (the main functional genus of heterotrophic denitrification) in the bioretention cell to 25.17% and 3.06%. The results indicated that woodchips promoted the proliferation of both heterotrophic and autotrophic microorganisms, therefore enhancing the nitrogen removal efficiency of mixotrophic denitrification.

Salt-tolerant heterotrophic nitrification and aerobic denitrification (HNAD) bacterium enhancing a pilot-scale moving bed biofilm reactor (MBBR) treating mariculture wastewater treatment with different COD/TN ratios

Efficient nitrogen (N) removal from mariculture wastewater is one of the important measures to protect the marine ecological environment. A moving bed biofilm reactor (MBBR) inoculating heterotrophic nitrification and aerobic denitrification (HNAD) bacteria was set and the effects of chemical oxygen demand (COD) and total nitrogen (TN) (COD/TN) ratios on N removal performance, enzymatic activity, biofilm characteristics and microbial community were discussed. Results showed that a more stable N removal performance was obtained in the MBBR process inoculating HNAD bacteria under low COD/TN ratio compared with the conventional MBBR. The removal efficiency of nitrate nitrogen (NO3−-N) declined with COD/TN ratio decrease, and protein (PN) and polysaccharide (PS) concentration decreased from 284.3 and 37.1 mg (g VSS)−1 to 42.9 and 14.4 mg (g VSS)−1 with low ammonia monooxygenase (AMO), nitrite reductase (NIR) and nitrate reductase (NR) activities. Sequencing analysis revealed that strain Zobellella B307 became the dominant microorganism (the relatively abundance is 2.33–5.60 %), and its relatively abundance and the functional genes related to N metabolism reduced from 15.38 % to 9.66 % and 0.61 % to 0.55 % with COD/TN ratio decrease to explain the reason for the decrease of N removal efficiency. This study can provide a deep insight into N removal mechanism of the reactor inoculating HNAD bacteria under different COD/TN ratios.

Evaluation on applying Condensate from Food Waste Dry Process as External Carbon Source to Biological Denitrification Process

Objectives:In this study, the applicability of dry condensate generated from food waste dry feed conversion process was evaluated as an external carbon source to increase the efficiency of the biological denitrification process.Methods:The experiment was carried out in the form of a batch test, and dry condensate was injected into each reactor according to the COD and T/N ratio (C/N ratio). Then, the reactor was operated under anoxic conditions for 5 hours, and nitrate nitrogen was analyzed at intervals of 1 hour.Results and Discussion:The dry condensate from food waste showed a low nitrogen content (T-N 220 mg/L) compared to a high organic matter content (TCOD 21,863 mg/L), and was analyzed to satisfy the conditions of an external carbon source in the denitrification process. And as a result of the experiment, it was found that the nitrate nitrogen removal efficiency was up to 76% after 5 hours at a C/N ratio 7.50:1, which was significantly increased compared to the control which was without condensed water (removal efficiency 4%). Moreover, the removal efficiency of 28% was exhibited even at the C/N ratio 0.95:1, which exhibited the lowest efficiency. In addition, as a result of calculating the specific denitrification rate (SDNR) for each C/N ratio, 7.50:1 was found to be as 0.0726 mg NO3-/mg VSS/d, which was significantly increased than that of control as 0.0038mg NO3-/mg VSS/d.Conclusion:Based on these results, it is judged that it is possible to utilize the dried condensate of food waste as an external carbon source in the denitrification process.

Sewage denitrification performance and sludge properties variation with the addition of liquid from perishable organic anaerobic fermentation

The organics in the classified wet waste were deficiently utilized while sewage denitrification requires abundant carbon sources. Herein, the fermentation of perishable organic waste (POW) and the denitrification process with obtained liquid were investigated. The most volatile fatty acids (VFAs) production was realized with the fermentation liquid of food waste (FL-FW). Increasing substrate tended to lower the proportion of VFAs and acetic acid in FL-FW. Under the optimum conditions of FL-FW carbon source, carbon to nitrogen ratio 7, and temperature 30 ℃, the removal efficiency of nitrate nitrogen reached 99.23% within 4 h. The sludge settleability and microbial activity were significantly enhanced, contributing to the actual sewage a promotional removal of organics (95.84%) and nitrogen (70.31%) with the supplementation of FL-FW. High addition ratio would cause more degradation of refractory organics, which confirmed the feasibility of using FL-FW as a cost-efficient carbon source for the denitrification.

Nitrogen removal and abundances of associated functional genes in rhizosphere and non-rhizosphere of a vertical flow constructed wetland in response to salinity

It investigated the nitrogen removal performance and the abundances of nitrogen functional genes in the rhizosphere and non-rhizosphere when vertical flow constructed wetland (VFCW) was used to treat brackish eutrophic water. The results demonstrated that both total nitrogen (TN) and ammonia nitrogen (NH4-N) removal efficiencies decreased with the salinity increasing from 0.05% to 1.0%. However, the removal efficiency of nitrate nitrogen (NO3-N) remained more than 93%. It was found by quantitative real-time polymerase chain reaction (qPCR) that abundances of amoA, nosZ, napA, nirK and nirS were greater in the rhizosphere than in the non-rhizosphere at the salinities of 0.05%, 0.5% and 1.0%. As the salinity increased, the abundance of amoA reduced. It indicated that the salinity inhibited the growth of ammonia oxidizing bacteria (AOB) and further hindered the nitrification, which resulted in the deterioration of TN removal performance. The abundances of nosZ, napA, nirK and nirS in the rhizosphere and non-rhizosphere were the highest at 1.0% salinity. The denitrifying bacteria might adapt to the salinity stress, which guaranteed high NO3-N removal efficiency.

Effect of pre-treatment of wastewater in HRAP on nitrogen removal in subsurface flow gravel bed constructed wetland

This study discusses the effect of application of High Rate Algal Pond (HRAP) as a pre-treatment unit on nitrogen transformation and removal in Sub-surface flow Gravel bed Constructed Wetland (SGCW). Experiments were carried out at the University of Dar es Salaam main campus wastewater treatment facility in two different settings. In Phase I, effluent from primary facultative pond was fed directly to unplanted gravel bed SGCW, with a discharge of 0.69 m3/d. During Phase II, the HRAP with 0.6 m depth, received effluent from primary facultative pond at a flow rate of 1.2 m3/d and discharged it to unplanted gravel bed SGCW with 0.8 m deep, filled to 10 cm above water level with 20 mm diameter aggregates, at a flow rate of 0.69 m3/d. Both HRAP and SGCW were operated at a retention time of 5 days. The results showed that improved nitrogen removal occurred with inclusion of HRAP unit. In Phase I, an average nitrogen removal of 41.3% was achieved, while in Phase II total nitrogen reduction in SGCW improved to 57.3%. These results show the significance of HRAP for better performance of nitrogen removal in gravel bed SGCW. It was further observed that the removal efficiency of nitrate-nitrogen was superior in SGCW phase II (68.2%) compared to SGCW phase I (20.7%). Hence this research proved that provided the influent is fully nitrified in the pre-treatment system such as HRAP, denitrification becomes the major contributor to the nitrogen removal process in SGCW.

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

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.

Assessing the Integration of Wetlands along Small European Waterways to Address Diffuse Nitrate Pollution

Nitrate concentrations in numerous European fresh watercourses have decreased due to end-of-pipe measures towards manure and fertilization management, but fail to meet the environmental objectives. The implementation of complementary measures to attenuate diffuse nitrate pollution in densely populated regions characterised by limited available area has been barely studied. To tackle this issue, this study evaluates the feasibility of integrating Constructed Wetlands (CWs) along waterways as a promising tool to facilitate compliance with the nitrate regulations. The aim is to calculate the required area of land alongside a specific watercourse to integrate CWs to reduce nitrate concentrations consistently below the 11.3 and 5.65 mgNO3-N/L levels, according to the Nitrates Directive and the Flemish Environmental Regulations. Nitrate-nitrogen removal efficiencies achieved at case study CWs were compared and validated with reported values to estimate the needed wetland areas. In addition, the removal efficiencies and areas needed to meet the standards were calculated via the kinetic model by Kadlec and Knight. The predicted areas by both methods indicated that CWs of 1.4–3.4 ha could be implemented in certain regions, such as Flanders (Belgium), with restricted available land. To conclude, three designs for ICWs (Integrated Constructed Wetlands) are proposed and evaluated, assessing the feasibility of their implementation.

Application of light-weight filtration media in an anoxic biofilter for nitrate removal from micro-polluted surface water.

The research investigated nitrate removal from micro-polluted surface water by the single-stage process of anoxic biofilter using light-weight polystyrene beads as filtration media. In this study, sodium acetate was used as an external carbon source and the nitrate removal efficiency under different regimes of hydraulic loading rate (HLR), water temperature, and C/N ratio was studied. In addition, the effect of backwash on denitrification efficiency was investigated. The results show that the biofilter achieved a high nitrate removal efficiency in 2 weeks at water temperatures ranging between 22 and 25 °C at a C/N ratio (COD:NO3(-)-N) of 6:1. Besides, the average removal efficiency of nitrate at HLRs of 5.66, 7.07 and 8.49 m(3) m(-2) h(-1) were 87.5, 87.3 and 87.1%, respectively. The average removal efficiency of nitrate nitrogen was 13.9% at a HLR of 5.66 m(3) m(-2) h(-1) at water temperatures of 12-14 °C, then it increased to 93.7% when the C/N ratio increased to 10. It suggests that the optimal hydraulic retention time is at water temperatures of 8-10 °C. The water consumption rate of backwash was about 0.2-0.3%, and denitrification efficiency returned to the normal level in 12 h after backwash.

Effect of Nitrite and Nitrate Concentrations on the Performance of AFB-MFC Enriched with High-Strength Synthetic Wastewater.

In order to study the effect of nitrite and nitrate on the performance of microbial fuel cell, a system combining an anaerobic fluidized bed (AFB) and a microbial fuel cell (MFC) was employed for high-strength nitrogen-containing synthetic wastewater treatment. Before this study, the AFB-MFC had been used to treat high-strength organic wastewater for about one year in a continuous flow mode. The results showed that when the concentrations of nitrite nitrogen and nitrate nitrogen were increased from 1700 mg/L to 4045 mg/L and 545 mg/L to 1427 mg/L, respectively, the nitrite nitrogen and nitrate nitrogen removal efficiencies were both above 99%; the COD removal efficiency went up from 60.00% to 88.95%; the voltage was about 375 ± 15 mV while the power density was at 70 ± 5 mW/m2. However, when the concentrations of nitrite nitrogen and nitrate nitrogen were above 4045 mg/L and 1427 mg/L, respectively, the removal of nitrite nitrogen, nitrate nitrogen, COD, voltage, and power density were decreased to be 86%, 88%, 77%, 180 mV, and 17 mW/m2 when nitrite nitrogen and nitrate nitrogen were increased to 4265 mg/L and 1661 mg/L. In addition, the composition of biogas generated in the anode chamber was analyzed by a gas chromatograph. Nitrogen gas, methane, and carbon dioxide were obtained. The results indicated that denitrification happened in anode chamber.

생물환원전극 미생물연료전지에서 외부저항 및 유입부하에 따른 유기물 및 질소 제거와 전기생산에 미치는 영향

In order to remove the organic substances and the nitrate-nitrogen contained in wastewater, some researchers have studied the simultaneous removal of organics and nitrogen by using different biocathode microbial fuel cells (MFCs). The operating conditions for removing the contaminants in the MFCs are the external resistances, HRTs, the concentration of the influent wastewater, and other factors. This study aimed to determine the effect of the external resistors and organic loading rates, from the changing HRT, on the removal of the organics and nitrogen and on the production of electric power using the Denitrification Biocathode - Microbial Fuel Cell (DNB-MFC). As regards the results of the study, the removal efficiencies of did not show any difference, but the nitrate-nitrogen removal efficiencies were increased by decreasing the external resistance. The maximum denitrification rate achieved was in the external resistance , and the maximum power density was in . When the DNB-MFC was operated with increasing influent organic and nitrate loading by reducing the HRTs, the removal efficiencies were increased linearly, and the maximum nitrate removal rate was at HRT 0.6 h.

Effect of the solid carbon sources addition on performance of wastewater treatment efficiency in vertical flow constructed wetland

以垂直流人工湿地小试系统为研究对象,探讨了不同位置(表层、上层、中层和下层)添加固体碳源对系统氮、磷及COD_Cr去除效果的影响.结果表明:湿地下层硝态氮去除率低于中层,最适宜碳源添加位置为垂直流人工湿地中、下层.添加碳源系统中,碳源添加位置为表层的系统COD_Cr去除率最高,各系统出水COD_Cr浓度均低于进水,不引起系统出水中COD_Cr浓度的增加.添加碳源显著提高脱氮除磷效果,碳源添加位置为下层的系统TN去除率最高,碳源添加位置为表层的系统氨氧化作用明显,出水铵态氮浓度最高,各系统对亚硝态氮和硝态氮去除率差异不明显,但对硝态氮都表现出良好的去除效果.碳源添加位置为下层的系统硝化作用最完全,TP去除能力也显著优于其他各系统.添加碳源至垂直流人工湿地下层可以达到同步脱氮除磷的效果.;The optimum of carbon sources adding location and the effects of adding to different locations(surface, the upper, middle and lower layers) on the removal efficiency of nitrogen, phosphorus and COD_Cr were investigated in small-scale vertical flow constructed wetlands. The results showed that the removal efficiency of the nitrate nitrogen in the lower layer was lower than that in the middle layer, and the most suitable location for carbon sources supplement was the middle and lower layer of the vertical flow constructed wetlands. Among the systems with carbon sources added, the one which added the carbon sources to the surface layer exhibited the highest removal efficiency of COD_Cr, and the concentration of COD_Cr of the effluent of each system were lower than the influent, not causing the concentration of COD_Cr increasing of the effluent of the systems. Adding carbon sources can significantly improve the removal efficiency of nitrogen and phosphorus. The system which added the carbon sources to the lower layer showed the highest removal efficiency of total nitrogen. The system which added the carbon sources to the surface layer showed significant ammoxidation, and the concentration of ammonia nitrogen of the effluent was highest. The removal efficiency of each system showed no significant difference in the removal efficiency of nitrite and nitrate nitrogen, and all showed great removal efficiency of nitrate nitrogen. The system which added the carbon sources to the lower layer showed the most complete nitrification, and the removal efficiency of total phosphorus was also significantly better than that of other systems. Adding carbon sources to the lower layer of the vertical flow constructed wetland can achieve the effect of simultaneous removal of nitrogen and phosphorus.

Organic carbon and nitrogen removal from a strong wastewater using a denitrifying suspended growth reactor and a horizontal-flow biofilm reactor

Recirculation of fully nitrified effluent from a laboratory horizontal-flow biofilm reactor (HFBR) to a mixed pre-denitrification reactor (DR) was used to remove organic carbon and nitrogen from synthetic dairy wastewater. Three recirculation ratios of 2, 4, and 6 were examined in this study and the average filtered chemical oxygen demand (COD f) and total nitrogen (TN) removals were up to 97.4% and 85.5%, respectively, at 11 °C. In the DR, the nitrate nitrogen removal efficiencies and rates were 86–96% and 22–34 g N/m 3 d. In the HFBR, the ammonium nitrogen removal rates were 293–337 mg N/m 2 d.