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1.
The study focused on the feasibility of high NH4 +–N (400–600 mg/L) and COD load at two different hydraulic retention times (HRTs = 36 and 24 h) in two identical aerobic–anoxic sequencing bioreactors which were constructed in series in a single system using a specifically designed single biomass containing autotrophic nitrifying and heterotrophic denitrifying bacteria. Internal recirculation of synthetic wastewater from one tank to other was not carried out like the conventional aerobic–anoxic processes. Cycles of 15 days under sequences of aerated and non-aerated periods of three hour each were repeated during each continuous flow experiment conducted. Sodium bicarbonate and sodium acetate were selected as the appropriate inorganic and organic carbon sources. The results showed that the HRT may not affect the simultaneous nitrification and denitrification processes. Average nitrification ratio was obtained to be above 20 mg/L NH4 +–N/h daily. Results of 90 days’ operation also showed high removal efficiencies of ammoniacal nitrogen of about 83% daily. The main advantage of this process includes efficient ammoniacal nitrogen removal without separated aerobic and anoxic tanks, decrease operating costs due to the lesser oxygen concentration requirement in the bioreactors.  相似文献   

2.
The potential mineralization and immobilization of soil nitrogen (N), phosphorus (P) and sulfur (S) are relatively high in natural ecosystems. This study was conducted to investigate the changes in essential plant macronutrients; N, P, and S status in response to different soil depth in rangeland ecosystems in vitro. The net nutrient mineralization was measured during 90 days at different depths (0–15, 15–30, 30–45 and 45–60 cm), using kinetic models to estimate the release rate. The net ammonification and mineralization of P and S were described using parabolic diffusion equation, while the power function equation was used to describe the net nitrification. The results indicated that the amount of released ammonium (NH4 +) decreased with time and depth and the rates of net ammonification were negative in all samples. Conversely, nitrification increased with time and depth and the rates were all positive. The net mineralization for both P and S reduced with time. The concentration of mineralized SO4 2? increased with depth like nitrate (NO3 ?). Accumulation of SO4 2? and NO3 ? in subsurface soils and NH4 + and P at surface horizons can increase the potential of their loss by leaching or volatilization.  相似文献   

3.
The experiment was conducted to ascertain net production and consumption rates of 15NH4 + and 15NO3 ? for water and sediment in a wetland. This was done using 15N isotope pool dilution methodology under ambient and elevated atmospheric CO2 concentrations in experimental riparian wetlands to obtain the gross N transformation rates. The 15N budget for sediment was also estimated. The results suggested that the differences in high proportion of 15N concentration in the overlying water body under elevated CO2 could be attributed to the low production and high consumption rates of 15NH4 + in sediment. The elevated CO2 effect on production and consumption of NH4 + decreased by 144 % (P = 0.014) and increased by 153 % (P = 0.009), respectively. Thereby, 15NH4 + production rates are negatively related with 15NO3 ? consumption rates and this accounted for the decreases in net 15NO3 ? consumption under CO2 enrichment in the wetland sediment by 11 % (P = 0.528). Therefore, 15NO3 ? production and consumption rates may strongly depend on NH4 + production. Inorganic 15N and total 15N exported from sediment to overlying water body by the effect of CO2 were 41 % (P = 0.071) and 18 % (P = 0.000), respectively. Therefore, low net 15NH4 + production and high 15NH4 + consumption rates under elevated CO2 may partly explain the significant reduction of N from the sediment.  相似文献   

4.
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5.
Eutrophication of lakes and reservoirs has become a worldwide environmental problem, and nitrogen (N) has been recognized as one of the key factors responsible for eutrophication. Nitrogen adsorbed on sediments may be released via chemical and biological processes under changing environmental conditions. Spatial distributions of concentrations of ammonia nitrogen (NH4 +–N), nitrate nitrogen (NO3 ?–N) and total nitrogen (TN) were investigated in sediments and overlying water of Dongting Lake, the second largest freshwater lake in China. The concentration of TN in the sediments exhibited strong spatial variation with relatively high values in the eastern part and relatively low values in the southern part of the lake. The TN concentration in the water of different regions of Dongting Lake was affected by the internal load of sediment N. The vertical distribution of TN in sediment cores showed a decreasing trend with an increase in depth. Concentrations of NH4 +–N in the sediment cores decreased with the depth increase until 6–8 cm and then increased slowly. However, concentrations of NO3 ?–N in the sediment cores showed an opposite trend from those of NH4 +–N. A kinetic release experiment of NH4 +–N showed that the maximum release rate occurred in the first 5 min and the amount of NH4 +–N release reached 77.93–86.34 % of the total amount in 0–10 min. The release of NH4 +–N in the surface sediments of Dongting Lake fits a first-order kinetics function.  相似文献   

6.
Quantifying Sediment Nitrogen Releases Associated with Estuarine Dredging   总被引：1，自引：0，他引：1  
Experimental studies of sediment pore water NH4 + chemistry, adsorbed NH4 + concentrations, sediment?Cwater NH4 + exchange and N2?CN flux were carried out to quantify the mass of labile N that can be released during large-scale dredging activities. Pore water NH4 + concentrations below 0.5-m sediment depth averaged 5 ± 2 mmol L?1 with average adsorbed NH4 + concentrations of 11 ??mol g?1. Elevated NH4 + concentrations found in rapidly accreting dredge channels are partly a result of the rapid advective burial of both reactive organic matter and pore water. Elutriate tests, a dilution of sediment with site water, yielded adsorbed NH4 + concentrations very similar to those using the more typical KCl extraction. Intact deep sediment sections exposed to overlying water, used to simulate postdredging conditions, showed high initial fluxes of ammonium and no development of coupled nitrification?Cdenitrification under the cold incubation conditions. Despite high concentrations and effluxes of NH4 + during dredging, the amount of NH4 + release during dredging was <0.5% of northern Chesapeake Bay sediment fluxes. The likelihood of large environmental effects of nitrogen release during the dredging of navigational channels in the Chesapeake Bay is low.  相似文献   

7.
A combined ABR–MBR process consisting of an anaerobic baffled reactor (ABR) combined with an aerobic membrane bioreactor (MBR) treating municipal wastewater was investigated at controlled pH range 6.5–8.5 and at constant temperature 25 ± 1 °C. Total nitrogen (TN), ammonia (NH4 +–N), total phosphorus (TP), and chemical oxygen demand (COD) removal performances were evaluated by analyzing the mechanism for efficient nutrient removal. The results showed that the average removal rates of COD, NH4 +–N, TN, and TP reached 93, 99, 79, and 92 %, respectively, corresponding with the COD, NH4 +–N, TN, and TP effluent of 24 (18–31), 0.4 (0–0.8), 10.6 (8.8–12.9), and 0.31 (0.1–0.5) mg/L under the operational condition of hydraulic retention time (HRT) 7.5 h, recycle ratio 200 %, and dissolved oxygen 3 mg/L. The MBR enhanced NH4 +–N, TN, and TP removal rates of 13, 10, and 18 %, respectively, and the membrane retention reduced TP 0.17 mg/L. The process was able to maintain a stable performance with high-quality effluent. Analysis of the results by fluorescence in situ hybridization showed that the abundance of ammonia-oxidizing bacteria, nitrite-oxidizing bacteria, and phosphorus accumulating organisms as percentages of all bacteria in each compartment was stable. The enriched microorganisms in the system appear to be the main drivers of the process efficient for nutrient removal.  相似文献   

8.
The physicochemical properties and major ion chemistry of the groundwater sources from alluvial aquifers along the stretch (60 km) of Jhelum River in Kashmir Himalaya were determined in order to identify hydro-geochemical processes and their suitability for drinking purposes. The data depicted that calcium and bicarbonates were dominating among the cations and anions. The results indicate the trend of cation dominance as Ca2+ > Na+ > Mg2+ > K+, whereas anion dominance was in the order of HCO3 ? > Cl? > SO4 2?. Ratio of calcium to magnesium indicated the dissolution of Ca2+ from CaCO3, which results in an increased levels of Ca2+ in the groundwater. Interpretation of Piper Trilinear plot understands the various geochemical processes affecting the groundwater quality and shows groundwater was dominated by Ca–HCO3 type. The pH was recorded in the slightly alkalinity range 7.2–7.8 and was showing positive correlation with HCO3 ?. The chloro-alkaline indices revealed 86% of the sources exchange by a type of base-exchange reactions, rest by cation–anion exchange. Gibbs diagram revealed groundwater sources fall in the category of rock dominance. The concentration of the nitrogen compounds was in the progression of NO3–N > NH4–N > NO2–N, and the PO4 ? fluctuated from 0.12 to 0.22 mg/L. Moreover, corrosivity ratio indicated that water from the majority of sources (71%) is safe to supply using pipes without any corrosive effects, while 29% of sources are corrosive in nature and need non-corrosive pipes for transporting and lifting of groundwater. The results revealed, groundwater samples were within permissible limits as prescribed by International and National standards, for drinking purposes. The State government and NGO’s can show their interest in utilizing such water resources to overcome the shortage of drinking water in a sustainable way for the daily consumption of the people living in the vicinity of Jhelum River.  相似文献   

9.
《Applied Geochemistry》1995,10(2):207-214
The importance of adsorption on peat for decreasing NH4+ was estimated in four overland flow areas (OFA) in northern Finland, where peat mining water is purified by conducting it across a natural mire of a given size. The effective cation exchange capacity (ECEC) values of peat in the OFAs ranged from 21.4 to 92.7 meq per 100g, being generally highest in the surface 0–15 cm. It was estimated that about 4.6–5.8% of the peat cation exchan e sites could be occupied by NH4+, corresponding to a NH4+ retention capacity of about 0.18 to 0.77 g kg−1 dry peat. Assuming that the retention was attributable to the 0–15 cm surface peat layer alone, the calculated NH4+ retention potential of OFA peat should have lasted under 6 months with the loadings imposed on the OFAs and the decreases in NH4+ amounts in peat mining water considered here. The actual duration of peat capacity to retain NH4+ in the OFAs has, however, already been shown in this research to be longer, and apparently will be so also in future, probably as a result of two processes: nitrification and subsequent N loss through denitrification, and biological assimilation. Hence, cation exchange capacity of OFA was an important property that contributed to surface water protection against eutrophication by N.  相似文献   

10.
Tidal marshes act as a buffer system for nutrients in the pore water and play important roles in controlling the budget of nutrients and pollutants that reach the sea. Spatial and seasonal dynamics of pore water nutrients were surveyed in three tidal marshes (Chongming Island, Hengsha Island, and Fengxian tidal flat) near the Yangtze Estuary and Hangzhou Bay from August 2007 to May 2008. Nutrient variations in pore water closely followed seawater quality in the estuaries, while the average concentration of NH4 +–N, the main form of inorganic nitrogen in pore water, was over two orders of magnitude higher than that in seawater which was dominated by nitrate. NH4 +–N export (13.81 μmol m?2 h?1) was lower than the import of (NO3 ?+NO2 ?)–N (?24.17 μmol m?2 h?1) into sediment over the 1-year period, hence reducing N-eutrophication in coastal waters. The export of SiO3 2?–Si and PO4 3?–P from tidal marshes regulated nutrient level and composition and lifted the ratio beyond potentidal element limitation in the coastal system. Moreover, macrophyte plants (Spartina alterniflora and Phragmites australis) played significant roles in controlling nutrient concentration in pore water and its exchange between marshes and estuaries. Fengxian marsh was characterized by higher nutrient concentrations and fluxes than other marshes in response to the more serious eutrophication in Hangzhou Bay than in the Yangtze Estuary.  相似文献   

11.
We measured fluxes of NH4+ and NO3− and δ15N of NH4+, sediment, and porewater NH4+ from incubated sediment cores along a nitrate gradient and in different seasons from Childs River, MA. NH4+ flux was low at the downstream site with the lowest concentration of organic matter (high salinity) but otherwise did not differ along the estuary. The δ15N of regenerated NH4+ ranged from +6.1‰ to +15.3‰ but did not vary significantly with season or salinity; the mean for the entire estuary was +10.4 ± 0.5‰. Based on differences between the δ15N of regenerated NH4+ and sediment, and expected isotopic fractionation due to remineralization, we concluded that nitrification occurred after remineralization of NH4+. Differences between the δ15N of regenerated NH4+ and the δ15N of porewater NH4+ provided further evidence of nitrification. We estimated that 11% to 48% of remineralized NH4+ underwent coupled nitrification–denitrification before release into the water column. In spite of losses to denitrification, NH4+ flux released 1.4 mol N m−2 year−1 to the water column and could provide 42% of phytoplankton nitrogen requirements.  相似文献   

12.
The concentrations and isotopic compositions of the various forms of nitrogen in silty clay sediments from the Bay of Quinte (Lake Ontario) have been determined. The total organic-N content is high throughout the sediment profiles and generally decreases with depth. On the contrary, exchangeable NH+4-N concentration is quite low and tends to increase with depth in two out of three sediment cores examined. The concentration of non-exchangeable NH+4-N and the 6 N HCl hydrolyzable NH+4-N are relatively constant with depth. Among the N fractions analyzed, the exchangeable NH+4-is most enriched in 15N. In most cases, the δ 15 N values of the N fractions remain relatively constant with sediment depth. There is no apparent correlation of δ 15 N values with the N concentration for any of the individual N fractions. The observed ranges in the δ 15 N values are: exchangeable NH+4, + 5–+10‰; 6 N HCl hydrolyzable total N and 6 N HCl hydrolyzable NH+4-N, + 3.5–+5.5‰.  相似文献   

13.
Balram Ambade 《Natural Hazards》2014,70(2):1535-1552
In the present work, chemical characterization and sources of fog water contaminants in the most polluted area of central India, Raipur, and its surroundings are described. The fog water (n = 22) was collected during 2010–2011 from six sites. The physical (i.e., pH, fog amount, electrical conductivity and TDS) and chemical (i.e., F?, Cl?, NO3 ?, SO4 2?, NH4 +, Na+, K+, Mg2+, Ca2+, Al, Mn, Fe, Cu, Zn, Pb and Hg) parameters of the fog water were investigated. The effect of meteorology, i.e., temperature, humidity and wind speed, on the precipitation of the fog water contaminants is discussed. The cluster and factor analysis are used to apportion the sources of the contaminants in the fog water.  相似文献   

14.
Nowadays, natural resources are under increasing stress which fosters wastewater reuse planning and emphasizes on the decentralized wastewater treatment. Vermifiltration has been described as a viable alternative to treat domestic and urban wastewater, but few studies have focused on the impact of different filter packings on vermifiltration performance. This study evaluates the effect of vermicompost and sawdust in a single-stage vermifilter (VF) for urban wastewater treatment. After an acclimation period of 45 days, urban wastewater from a combined sewage collection system was applied continuously for 24 h. Earthworm stock density was of 20 g L?1, HRT of 6 h, HLR of 0.89 m3 m?2 day?1 and OLR of 7.38 g BOD5 day?1. System performance was assessed by the removal efficiencies of BOD5, COD, TSS, NH4 +, TN and TP, and fecal coliforms and helminth eggs elimination. Vermicompost (VE) and sawdust (SE) were tested, using an earthworm abundance of 20 g L?1. Treatment efficiencies were 91.3% for BOD5, 87.6% for COD, 98.4% for TSS and 76.5% for NH4 + in VE, and 90.5% for BOD5, 79.7% for COD, 98.4% for TSS and 63.4% for NH4 + in SE. Earthworms contributed to reduce NH4 + and TN removal and to increase NO3 ? concentration. No treatment was able to eliminate fecal coliforms down to guidelines values for wastewater irrigation as helminth eggs were completely eliminated. Single-stage vermifiltration system using both filter packings is inconsistent and cannot meet EU guideline values for discharge in sensitive water bodies and WHO guidelines for irrigation with treated wastewater.  相似文献   

15.
This paper aims to reveal the reciprocal influence of Kürtün Dam and wastewaters from the settlements on the water quality in the stream Har?it, NE Turkey. Several key water-quality indicators were measured: water temperature (T), pH, dissolved oxygen (DO), electrical conductivity, water hardness, chemical oxygen demand (COD), ammonium nitrogen (NH4 +–N), nitrite nitrogen (NO2 ?–N), nitrate nitrogen (NO3 ?–N), total Kjeldahl nitrogen (TKN), total nitrogen (TN), orthophosphate phosphorus (PO4 3?–P), and methylene blue active substances (MBAS). The monitoring and sampling studies were conducted every 15 days from March 2009 to February 2010 at two stations selected in the upstream and downstream of the Kürtün Dam. It was concluded that the Kürtün Dam Lake had a high-quality water in terms of T, pH, DO, COD, NH4 +–N, NO2 ?–N and NO3 ?–N values, but slightly polluted water with respect to TKN, PO4 3?–P, and MBAS according to the Turkish Water Pollution Control Regulation. The dam improved the stream water quality by increasing the DO concentration, and decreasing the NO2 ?–N and PO4 3?–P concentrations thanks to its hydraulic residence time despite the wastewater discharge by the nearby settlements. However, the wastewater discharge deteriorated the stream water quality increasing the COD, NH4 +–N, NO3 ––N, and TN concentrations.  相似文献   

16.
Increased nitrogen (N) input to ecosystems could alter soil organic carbon (C) dynamics, but the effect still remains uncertain. To better understand the effect of N addition on soil organic C in wetland ecosystems, a field experiment was conducted in a seasonally inundated freshwater marsh, the Sanjiang Plain, Northeast China. In this study, litter production, soil total organic C (TOC) concentration, microbial biomass C (MBC), organic C mineralization, metabolic quotient (qCO2) and mineralization quotient (qmC) in 0–15 cm depth were investigated after four consecutive years of N addition at four rates (CK, 0 g N m?2 year?1; low, 6 g N m?2 year?1; moderate, 12 g N m?2 year?1; high, 24 g N m?2 year?1). Four-year N addition increased litter production, and decreased soil organic C mineralization. In addition, soil TOC concentration and MBC generally increased at low and moderate N addition levels, but declined at high N addition level, whereas soil qCO2 and qmC showed a reverse trend. These results suggest that short-term N addition alters soil organic C dynamics in seasonally inundated freshwater marshes of Northeast China, and the effects vary with N fertilization rates.  相似文献   

17.
Ammonia is a major environmental factor influencing biomethanation in full-scale anaerobic digesters. In this study, the effect of different ammonia levels on methanogenic pathways and methanogenic community composition of full-scale biogas plants was investigated. Eight full-scale digesters operating under different ammonia levels were sampled, and the residual biogas production was followed in fed-batch reactors. Acetate, labelled in the methyl group, was used to determine the methanogenic pathway by following the 14CH4 and 14CO2 production. Fluorescence in situ hybridisation was used to determine the methanogenic communities’ composition. Results obtained clearly demonstrated that syntrophic acetate oxidation coupled with hydrogenotrophic methanogenesis was the dominant pathway in all digesters with high ammonia levels (2.8–4.57 g NH4 +-N L?1), while acetoclastic methanogenic pathway dominated at low ammonia (<1.21 g NH4 +-N L?1). Thermophilic Methanomicrobiales spp. and mesophilic Methanobacteriales spp. were the most abundant methanogens at free ammonia concentrations above 0.44 g NH3-N L?1 and total ammonia concentrations above 2.8 g NH4 +-N L?1, respectively. Meanwhile, in anaerobic digesters with low ammonia (<1.21 g NH4 +-N L?1) and free ammonia (<0.07 g NH3-N L?1) levels, mesophilic and thermophilic Methanosaetaceae spp. were the most abundant methanogens.  相似文献   

18.
The long-term sustainability of an anaerobic ammonium oxidation (anammox) process in a moving bed biofilm reactor (MBBR) treating highly concentrated (mean of 740 mg NH4 +-N L?1) wastewater was demonstrated by 1600 days of efficient operation. A high maximum total nitrogen removal rate (TNRR) of 1.5 g N m?2 d?1 was achieved at the low temperature of 20 °C. For nitrogen removal recovery in cases of nitrite inhibition, anammox intermediate nitric oxide (NO) was tested in batch experiments as an N-removal accelerating agent. The effect of the addition of various NO dosages (8–72 mg NO-N L?1) was studied under inhibitory nitrite concentrations (>100 mg NO2 ?-N L?1) for anammox bacteria. Optimal maintained NO concentration was 58 mg NO-N L?1 and brought about the highest biofilm-specific anammox activity (SAA). Compared to a blank test, the minimum concentration of added NO of 40 mg NO-N L?1 showed a statistically significant (p < 0.05) accelerating effect on SAA. No inhibition of SAA by NO was observed, although at NO concentrations exceeding 72 mg NO-N L?1, the acceleratory effect upon SAA was decreased by 8%. Changes in the bacterial consortia involved in nitrogen conversion were determined concurrently for the different nitrogen removal rates and operational conditions. Quantities of Planctomycetales clone P4 strains, which are the closest (99% similarity) relative to Candidatus Brocadia fulgida, increased from 1 × 103 to 1 × 106 anammox gene copies per g total suspended solids during reactor operation days 568–1600, which was determined by quantitative polymerase chain reaction. During the operation of the MBBR, the abundance of ammonium-oxidizing bacteria (AOB) increased proportionally (up to 30%). The abundance of nitrite-oxidizing bacteria (NOB) did not increase (remaining below 10%) during days 232–860. AOB became predominant over NOBs owing to the inhibition of free ammonia spiking on NOBs.  相似文献   

19.
The co-treatment of landfill leachate (LFL) with municipal wastewater (MWW) using shortcut sequencing batch reactor combined with coagulation–settling process (SBR + CS) was investigated. Four ratios of LFL to MWW volume (v/v) were used during experiments including the ratios 1:9, 2:8, 3:7 and 5:5. The average quality of the LFL was chemical oxygen demand (COD) of 20,800 mg L?1 and NH4-N of 2,645 mg L?1. The SBR-treating LFL in six series where mixing aeration and settling phases were varied from 4 to 14 h was combined with coagulation (FeCl3, Al2(SO4)3) with an interval of 2 h. It was found that ratio (1:9) of leachate to MWW under aeration and mixing phase of 4 h with settling time of 1.5 h exhibited the highest ability to remove both COD and NH 4 + -N, 99% and 85%, respectively. The short-time sequential batch reactor was tested for the treatment of raw LFL, and only 47% and 23% removal of COD and NH 4 + -N, respectively, could be achieved.  相似文献   

20.
The regulatory effect of salinity on nitrogen dynamics in estuarine sediments was investigated in the Randers Fjord estuary, Denmark, using sediment slurries and intact sediment cores and applying 15N-isotope techniques. Sediment was sampled at three representative stations varying in salinity, and all experiments were run at 0‰, 10‰, 20‰, and 30‰. The sediment NH4 + adsorption capacity decreased markedly at all stations when salinity was increased from 0‰ to 10‰; further increase showed little effect. In situ nitrification and denitrification also decreased with increasing salinities, with the most pronounced reduction of approximately 50% being observed when the salinity was raised from 0‰ to 10‰. The salinity-induced reduction in NH4 + adsorption capacity and stimulation of NH4 + efflux has previously been argued to cause a reduction in nitrification activity since the nitrifying bacteria become limited by NH4 + availability at higher salinities. However, using a potential nitrification assay where NH4 + was added in excess, it was demonstrated that potential nitrification activity also decreased with increasing salinity, indicating that the inhibitory salinity effect may also be a physiological effect on the microorganisms. This hypothesis was supported by the finding that denitrification based on NO3 − from the overlying water (Dw), which is independent of the nitrification process, and hence NH4 + availability, also decreased with increasing salinity. We conclude that changes in salinity have a significant effect on nitrogen dynamics in estuarine sediments, which must be considered when nitrogen transformations are measured and evaluated.  相似文献   

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