Influent NO3-N Research Articles

Desitrificación en simulación de agua subterránea usando lignito como fuente de carbono orgánico en fase sólida

To ensure safety standards of drinking water, it is essential to perform NO3 remediation in groundwater. Owing to the lack of organic carbon in groundwater, heterotrophic denitrification is not quite effective in groundwater. Few studies have reported about how Chinese lignite can be used as an organic carbon source for denitrification. In simulated conditions of groundwater, we determined whether the four lignite types (Lignite was obtained from Sanjitun, Lingshi, Wangniutan, and Zhaotong in China.) could be used as a solid-phase organic carbon source for denitrification; the analyses were performed in a test water column. For denitrification, the most effective carbon source was the lignite obtained from Wangniutan. It showed the highest efficacy of 34% in nitrate (NO3) removal for an influent NO3-N concentration of 30 mg• L−1. The effluent NO3-N concentrations below 20 mg L−1 and the water samples showed no acute toxicity when they were subjected to luminescent bacteria test. We performed static carbon release test and infrared spectral analysis on all the four lignite types, and we found that there was a direct relation between NO3 removal and the lignite’s ability for static carbon release. When NO3 concentrations were high and the rate of static carbon release was low, the efficacy of denitrification was greater. This effect was achieved when the molecular structure of lignite contained small molecular organic compounds in free states; these compounds primarily included the following functional groups: alcohols, phenols, and organic acids. These compounds were primarily used by the denitrifying bacteria.

Biological nitrate removal in a laboratory-scale slow sand filter

This research evaluated removal of nitrates from drinking waters in a slow sand filter (SSF). Batch experiments were performed to determine optimum carbon to NO3-N (C/N) ratio for the filtration experiments. The filter column was filled with filter sand of an effective diameter of 0.5 mm and uniformity coefficient of 1.23. The filter was operated at filtration rates of between 0.02 to 0.120 m/h and 0.01 to 0.25 m/h with concentrations of 22.6 and 45.2 mg NO3-N/l, respectively, and effluent samples of the SSF were taken at 6 depths of 10, 15, 20, 40, 60, 80 cm, and the bottom. Optimum C/N ratio was found to be 1.5 when using ethanol in batch tests when the removal efficiencies of NO3-N and C were higher than 90%. Although increasing filtration rates decreased NO3-N removal, effluent NO3-N concentration at the effluent port of the SSF was lower than the limit value. Most off the NO3-N removal was carried out at the upper layer of (10 cm) the filter bed. Concentration of NO3-N, NO2-N, and C were not detected at the 60 cm depth of the SSF through the study for the inlet concentrations of 22.6 mg NO3-N/l. As expected, increasing influent NO3-N concentration to 45.2 mg/l increased NO3-N, NO2-N, and C concentrations in the effluent water. The SSF process was unable to provide NO3-N removal rate of more than 228 g N/m3·d (0.2 m/h flow rate, 217g N/m2·d of surface loading rate). The NO3-N removal efficiency dropped slightly from 96 to 95% when the loading rate increased from 228 to 285 g/m3·d, but the effluent water contained higher concentrations of NO2-N (8.4 mg/l) than the standard value. The results of the SSF experiment demonstrated that averaged nitrogen conversion to volatile solids was about 0.77 mg VS/mg NO3-N.

Bacterial community dynamics in a biodenitrification reactor packed with polylactic acid/poly (3-hydroxybutyrate-co-3-hydroxyvalerate) blend as the carbon source and biofilm carrier

While heterotrophic denitrification has been widely used for treating such nitrogen-rich wastewater, it requires the use of additional carbon sources. With fluctuations in the nitrate concentration in the influent, controlling the C/N ratio to avoid carbon breakthrough becomes difficult. To overcome this obstacle, solid-phase denitrification (SPD) using biodegradable polymers has been used, where denitrification and carbon source biodegradation depend on microorganisms growing within the reactor. However, the microbial community dynamics in continuous-flow SPD reactors have not been fully elucidated yet. Here, we aimed to study bacterial community dynamics in a biodenitrification reactor packed with a polylactic acid/poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PLA/PHBV) blend as the carbon source and biofilm carrier. A lab-scale denitrifying reactor filled with a PLA/PHBV blend was used. With 85mg/L of influent NO3-N concentration and a hydraulic retention time (HRT) of 2.5h, more than 92% of the nitrate was removed. The bacterial community of inoculated activated sludge had the highest species richness in all samples. Bacterial species diversity in the reactor first decreased and then increased to a stable level. Diaphorobacter species were predominant in the reactor after day 24. In total, 178 clones were retrieved from the 16S rRNA gene clone library constructed from the biofilm samples in the reactor at 62 days of operation, and 80.9% of the clones were affiliated with Betaproteobacteria. Of these, 97.2% were classified into phylotypes corresponding to Diaphorobacter nitroreducens strain NA10B with 99% sequence similarity. Diaphorobacter, Rhizobium, Acidovorax, Rubrivivax, Azospira, Thermomonas, and Acidaminobacter constituted the biofilm microflora in the stably running reactor.

Biological Denitrification Using Slow-Release Carbon Source Composite Materials as Solid Carbon Source and Biofilm Carrier

As lack of organic carbon source is a key problem for biological denitrification, hemp fiber, PBS, PLA and PE were selected as raw materials, then four kinds of slow-release carbon source composite materials were prepared by 35A-double-screw extruder and used for biological denitrification. Their performan- ces were detected through static and continuous experiments. The results showed that in the static experiments, release carbon abilities of HB20 and HB40 were both not good, their CODMnwere 5.42 and 12.83mg/L respectively; In the continuous experiments, NO3-N removal rate of HLE decreased from 57.9% to 13.1% within 30 days. HBE could cause a continuous release of dissolved organic compound. In the operation of 66 days, above 96.0% NO3-N was removed and NO2-N level was below 0.02mg/L when influent NO3-N =30.0mg/L and HRT=24h. HBE was the most suitable carbon source carrier material for biological denitrification.

Slow-Release Carbon Source Composite Materials’ Preparation and Used for Denitrification in Groundwater

Four kinds of slow-release carbon source composite materials were prepared and used as carbon source and biofilm attachment carrier for groundwater nitrate pollution bioremediation. Their performances were detected through static and continuous experiments. The results showed that: In the static experiments, HB20 and HB40 had general release carbon ability, their CODMn were 5.42 and 12.83 mg/L respectively; In the continuous experiments, NO3-N removal rate of HLE decreased from 57.9% to 13.1% within 30 days, the denitrification endurance was not good. Organic carbon source can be released continuously by HBE which had the best denitrifying effect. In the operation of 66 days, above 96.0% NO3-N was removed and NO2-N level was below 0.02mg/L when influent NO3-N =30.0mg/L and HRT=24h. HBE was the most suitable carbon source carrier material which was used in groundwater nitrate pollution bioremediation.

In‐Stream Bioreactor for Agricultural Nitrate Treatment

Nitrate from agricultural activity contributes to nutrient loading in surface water bodies such as the Mississippi River. This study demonstrates a novel in-stream bioreactor that uses carbonaceous solids (woodchips) to promote denitrification of agricultural drainage. The reactor (40 m3) was trenched into the bottom of an existing agricultural drainage ditch in southern Ontario (Avon site), and flow was induced through the reactor by construction of a gravel riffle in the streambed. Over the first 1.5 yr of operation, mean influent NO3-N of 4.8 mg L(-1) was attenuated to 1.04 mg L(-1) at a mean reactor flow rate of 24 L min(-1). A series of flow-step tests, facilitated by an adjustable height outlet pipe, demonstrated that nitrate mass removal generally increased with increasing flow rate. When removal rates were not nitrate-limited, areal mass removal ranged from 11 mg N m(-2) h(-1) at 3 degrees C to 220 mg N m(-2) h(-1) at 14 degrees C (n = 27), exceeding rates reported for some surface-flow constructed wetlands in this climatic region by a factor of about 40. Over the course of the field trial, reactor flow rates decreased as a result of silt accumulation on top of the gravel infiltration gallery. Design modifications are currently being implemented to mitigate the effects of siltation. In-stream reactors have the potential to be scaled larger and could be more manageable than attempting to address nitrate loading from individual tile drains. They could also work well in combination with other nitrate control techniques.

Denitrification of a Nitrate-Rich Synthetic Wastewater Using Various Wood-Based Media Materials

This laboratory study examined the use of various wood materials as a carbon source in horizontal flow filters to denitrify nitrate-nitrogen (NO3-N) from a synthetic wastewater. The filter materials were: sawdust (Pinus radiata), sawdust and soil, sawdust and sand, and medium-chip woodchippings and sand. Two influent concentrations of NO3-N, 200 mg L−1 and 60 mg L−1, loaded at 2.9 to 19.4 mg NO3-N kg−1 mixture, were used. The horizontal flow filter with a woodchippings/sand mixture and an influent NO3-N concentration of 60 mg L−1, which operated over a study duration of 166 days, performed best, yielding a 97% reduction in NO3-N at steady-state conditions.

Upflow Reactors for Riparian Zone Denitrification

We used permeable reactive subsurface barriers consisting of a C source (wood particles), with very high hydraulic conductivities ( approximately 0.1-1 cm s(-1)), to provide high rates of riparian zone NO3-N removal at two field sites in an agricultural area of southwestern Ontario. At one site, a 0.73-m3 reactor containing fine wood particles was monitored for a 20-mo period and achieved a 33% reduction in mean influent NO3-N concentration of 11.5 mg L(-1) and a mean removal rate of 4.5 mg L(-1) d(-1) (0.7 g m(-2) d(-1)). At the second site, four smaller reactors (0.21 m3 each), two containing fine wood particles and two containing coarse wood particles, were monitored for a 4-mo period and were successful in attenuating mean influent NO3-N concentrations of 23.7 to 35.1 mg L(-1) by 41 to 63%. Mean reaction rates for the two coarse-particle reactors (3.2 and 7.8 mg L(-1) d(-1), or 1.5 and 3.4 g m(-2) d(-1)) were not significantly different (p > 0.2) than the rates observed in the two fine-particle reactors (5.0 and 9.9 mg L(-1) d(-1), or 1.8-3.5 g m(-2) d(-1)). A two-dimensional ground water flow model is used to illustrate how permeable reactive barriers such as these can be used to redirect ground water flow within riparian zones, potentially augmenting NO3- removal in this environment.

Denitrification Activity of a Poly-Hydroxybutirate (PHB) Embedded Soil-Column Reactor and Genomic Study of the Bacterial Community

Denitrification activity behavior and bacterial community structure in a poly-β-hydroxybutyrate (PHB) embedded soil-column reactor were investigated. The influent containing nitrate (NO3-N) was applied in a downward flow. The NO3-N concentration rapidly decreased only in the middle part of the column where PHB was embedded, which indicated that the denitrification activity in the reactor was related to PHB. Influent NO3-N was effectively removed in the reactor following 60 days of continuous operation. The total number of bacteria in the lower and middle parts of the column decreased after 30 days, and then increased again after 60 days; however, the number in the upper part continuously decreased with time. The number of PHB utilizing denitrifiers increased in both the middle and lower parts with time, contributing to denitrification activity in the reactor. From the result of PCR and denaturing gradient gel electrophoresis (PCR-DGGE), the presence of two denitrifing and a few other bacteria were determined, and which suggested of Ralstonia related species played an important role in the denitrification capability of the reactor.

WOOD-BASED FILTER FOR NITRATE REMOVAL IN SEPTIC SYSTEMS

The recognition that septic systems can generate groundwater plumes with nitrate concentrations exceeding thedrinking water limit has led to a need for improved nitrogen removal in septic systems. Long-term (3 to 5 year) monitoringresults are presented for four full-scale, on-site wastewater treatment systems using a novel porous media filter (Nitrex filter)for enhanced nitrogen removal. The filter removes nitrogen by denitrification of pretreated, nitrified, septic tank effluent usinga slowly soluble carbon source (wood byproduct material) incorporated into the filter. Results are presented for a house (sewageflow ~1 m3 d-1), a trailer park (7 m3 d-1), a communal residence (18 m3 d-1), and an inn (73 m3 d-1). In each case, theseptic tank effluent was pretreated using a sand filter, then flowed passively through the denitrification filter, and finally wasdispersed in a conventional tile bed. Influent (sand filter) NO3-N concentrations, averaging 14.2 to 37.7 mg L-1, weresignificantly attenuated in the denitrification filters at each site (p < 0.05) by amounts ranging between 87% and 98%.Reaction rates were temperature dependent, ranging from 7 to >10 mg N L-1 d-1, and showed no sign of deteriorating withsystem age at any of the sites. Results support previous mass balance calculations and pilot-scale field trials, suggesting thatsuch filters have the potential to operate for years without the need for media replenishment. These filters offer a practicalsolution to nitrate control in small to medium sized on-site wastewater treatment systems where simplicity of operation andlow maintenance are desirable.

Nitrate removal from the effluent of a fertilizer industry using a bioreactor packed with immobilized cells of Pseudomonas stutzeri and Comamonas testosteroni

A bioreactor for the removal of nitrate nitrogen (NO3-N) from industrial effluent is described which is comprised of a glass column (60 cm × 6 cm) packed with alginate beads containing denitrifying organisms Pseudomonas stutzeri and Comamonas testosteroni. The effluent containing high concentrations of nitrate (600–950 mg l−1) from the fertilizer industry and fusel oil (methanol as a major component) as organic carbon were used in the process. The reactor is operated in the continuous mode by injecting the pretreated nitrate-containing effluent at the top of the column. The Hydraulic retention time (HRT) was adjusted by changing the flow rates. When nitrate-containing wastewater was treated with immobilized cells, the nitrate removal rate reached a maximum 1.66 ± 0.07 Kg NO3-N m−3d−1 at an influent NO3-N concentration of 850 mg NO3M-N l−1within 12 h. The denitrification activity of the immobilized cells was compared with that of the free cells.

生分解性プラスチックＰＨＢを活用する硝酸性窒素で汚染された地下水の脱窒

The addition of a hydrogen donor is essential for heterotrophic biological denitrification treatment. Experiments were conducted on the denitrification treatment of groundwater using biodegradable plastic poly-β-hydroxybutyrate (PHB) . Batch denitrification tests using denitrifying activated sludge and continuous treatment using a soil column were carried out. Results showed that denitrifying activity improved with time and that the surface of PHB pellets changed unevenly in the batch tests. The soil column with PHB could remove influent NO3-N completely, but the soil column without PHB could not remove influent NO3-N at all. Effluent TOC concentrations from the soil column, in which 342g of PHB pellets were buried, were high (max: 38mg-TOC/l), but effluent TOC concentrations from soil columns in which 171 and 86 of g-PHB pellets were low.

Denitrification in free water surface wetlands receiving carbon supplements

Wetlands may be used as fixed film reactors for removal of NO3-N in wastewater. Two 1 hectare free water surface wetlands were constructed for denitrification of nitrified effluent from intermittent sand filters in Connell, Washington. The wetlands were designed to remove NO3-N from wastewater prior to land application. The design flow as 5300 m3/d (1.4 mgd). Primary effluent from a potato processing facility was used as a carbon supplement for detnitrification. Addition of primary effluent (COD = 2800 mg/L) resulted in a COD:NO3-N mass load ratio that ranged from 10 to 25. The total hydraulic retention time in the two wetlands varied from 1-2 days in the summer and winter. The NO3-N load ranged from 10 to 110 kg/ha d. The NO3-N mass removal rate ranged from 50 to 99% of the influent load. During the five months of data presented, January to May 1998, average monthly effluent NO3-N was 1.6 mg/L; monthly average influent NO3-N was 20.5 mg/L. An average of >85% of the NO3-N influent load was removed. The NO3-N removal rate coefficient (K20 = 358 m/yr) was higher than that measured in wetlands without carbon supplements and was independent of temperature above 12 degrees C.

Nitrogen removal in seawater using nitrifying and denitrifying bacteria immobilized in porous cellulose carrier

Nitrogen compounds in seawater are now contributing to serious water pollution problems. In this study, continuous removal of nitrogen in seawater using nitrifiers and denitrifiers immobilized in macro-porous cellulose carrier “AQUACEL” was examined. In nitrification, the nitrite oxidation step becomes the rate limiting step unless an influent inorganic carbon (g) / influent NH4-N (g) ratio (IC/NH4-N) of 7.23 is maintained. This is equivalent to an influent alkalinity (g) / influent NH4-N (g) ratio (ALK/NH4-N) of 8.25. Nitrite oxidizers were also sensitive to change in NH4-N loading. Unlike other biological removal systems used for seawater, trace element solution (containing Mo, Cu, Mn, Co, Fe, etc.) was added only at a high NH4-N loading rate of 0.65 kg-N/m3/carrier/d (at NH4-N concentration of 40 g/m3) and acclimatizing period was short, i.e., about a week. The maximum NH4-N loading rate obtained which removed 99 to 100% of the nitrogen compounds, was 1.30 kg-N/m3/carrier/d. For completion of denitrification, an influent phosphorus (g) per influent NO3-N(g) ratio (P/NO3-N) of 0.03 was required. Trace element solution (containing Fe, Mn, Mo, etc.) was doubled to 0.02% at NO3-N concentration of 560 g/m3. In addition, methanol concentration must be maintained at 30% more of the theoretical value of carbon concentration requirements. Copper enhanced nitrite reduction at an influent Cu(g) per influent NO3-N(g) ratio (Cu/NO3-N) of 0.002. The maximum allowable NO3-N loading rate necessary to remove about 99 to 100% of the nitrogen compounds was 20.79 kg-N/m3/carrier/d. This study reveakls that the AQUACEL system has high nitrifying and denitrifying capacities. The nitrogen loading capacity of denitrification is about ten times that of nitrification and is comparable to that of freshwater which also employed the AQUACEL system. In contrast, nitrogen loading capacity of nitrification is about six times less than that of freshwater, which indicates a higher sensitivity of nitrifiers to salinity. This indficates high sensitivity of the immobilized nitrifying bacteria to salinity. Morphological observations show that the ammonia oxidizers are a mixed culture ofNitrosomonas spp . and Nitrosovibrio spp., while the nitrite oxidizer is a Nitrobacter spp. The immobilized denitrifying bacteria showed similar morphological characteristics to the Hyphomicrobium spp.

Nitrogen removal in seawater using nitrifying and denitrifying bacteria immobilized in porous cellulose carrier

Nitrogen compounds in seawater are now contributing to serious water pollution problems. In this study, continuous removal of nitrogen in seawater using nitrifiers and denitrifiers immobilized in macro-porous cellulose carrier "AQUACEL" was examined. In nitrification, the nitrite oxidation step becomes the rate limiting step unless an influent inorganic carbon (g) / influent NH4-N (g) ratio (IC/NH4-N) of 7.23 is maintained. This is equivalent to an influent alkalinity (g) / influent NH4-N (g) ratio (ALK/NH4-N) of 8.25. Nitrite oxidizers were also sensitive to change in NH4-N loading. Unlike other biological removal systems used for seawater, trace element solution (containing Mo, Cu, Mn, Co, Fe, etc.) was added only at a high NH4-N loading rate of 0.65 kg-N/m3/carrier/d (at NH4-N concentration of 40 g/m3) and acclimatizing period was short, i.e., about a week. The maximum NH4-N loading rate obtained which removed 99 to 100% of the nitrogen compounds, was 1.30 kg-N/m3/carrier/d. For completion of denitrification, an influent phosphorus (g) per influent NO3-N(g) ratio (P / NO3-N) of 0.03 was required. Trace element solution (containing Fe, Mn, Mo, etc.) was doubled to 0.02% at NO3-N concentration of 560 g/m3. In addition, methanol concentration must be maintained at 30% more of the theoretical value of carbon concentration requirements. Copper enhanced nitrite reduction at an influent Cu(g) per influent NO3-N(g) ratio (Cu/NO3-N) of 0.002. The maximum allowable NO3-N loading rate necessary to remove about 99 to 100% of the nitrogen compounds was 20.79 kg-N/m3/carrier/d. This study reveakls that the AQUACEL system has high nitrifying and denitrifying capacities. The nitrogen loading capacity of denitrification is about ten times that of nitrification and is comparable to that of freshwater which also employed the AQUACEL system. In contrast, nitrogen loading capacity of nitrification is about six times less than that of freshwater, which indicates a higher sensitivity of nitrifiers to salinity. This indficates high sensitivity of the immobilized nitrifying bacteria to salinity. Morphological observations show that the ammonia oxidizers are a mixed culture of Nitrosomonas spp. and Nitrosovibrio spp., while the nitrite oxidizer is a Nitrobacter spp. The immobilized denitrifying bacteria showed similar morphological characteristics to the Hyphomicrobium spp.

Production of Nitrous Oxide Gas during Denitrification of Wastewater

Laboratory-scale experiments were conducted to examine nitrous oxide (N2O) production during denitrification. Substrate containing acetate (909 mgl-1 as COD), yeast extract (91 mgl-1 as COD) and KNO3 with COD/NO3-N of 1.5, 2.5, 3.5 and 4.5 was continuously fed to 3 l mixed flow reactors with varied solid retention time (SRT). N2O in produced nitrogenous gas far exceeded 10% in some conditions, and up to 8% of influent NO3-N was transformed to N2O. Low COD/NO3-N, short SRT and low pH were favored conditions for N2O production. COD/NO3-N of 1.5 and 2.5 at an SRT shorter than 10 days, and COD/NO3-N of 3.5 or 4.5 at an SRT shorter than 1 day resulted in N2O production together with incomplete nitrate and nitrite removal. Lower COD/NO3-N caused higher production of N2O. N2O production at pH of 6.5 was significantly higher than that at pH of 7.5 although pH of 7.5 and 8.5 showed less difference. The mixed liquor from the continuous reactor producing N2O readily produced N2O even when substrate with high COD/NO3-N was dosed in batch experiments, which suggests that N2O producing species may be accumulated during continuous operation in favorable conditions.