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1.
Strategies are proposed for the anaerobic treatment of lipid and phenolic-rich effluents, specifically the raw olive mill wastewater (OMW). Two reactors were operated under OMW influent concentrations from 5 to 48 g COD L−1 and Hydraulic Retention Time between 10 and 5 days. An intermittent feeding was applied whenever the reactors showed a severe decay in the methane yield. This strategy improved the mineralization of oleate and palmitate, which were the main accumulated Long-Chain Fatty Acids (LCFA), and also promoted the removal of resilient phenolic compounds, reaching remarkable removal efficiencies of 60% and 81% for two parallel reactors at the end of a feed-less period. A maximum biogas production of 1.4 m3 m−3 d−1 at an Organic Loading Rate of 4.8 kg COD m−3 d−1 was obtained. Patterns of individual LCFA oxidation during the OMW anaerobic digestion are presented and discussed for the first time. The supplementation of a nitrogen source boosted immediately the methane yield from 21 and 18 to 76 and 93% in both reactors. The typical problems of sludge flotation and washout during the anaerobic treatment of this oily wastewater were overcome by biomass retention, according to the Inverted Anaerobic Sludge Blanket (IASB) reactor concepts. This work demonstrates that it is possible to avoid a previous detoxification step by implementing adequate operational strategies to the anaerobic treatment of OMW.  相似文献   

2.
Irene Jubany 《Water research》2009,43(11):2761-2772
Partial nitrification (ammonium oxidation to nitrite) has gained a lot of interest among researchers in the last years because of its advantages with respect to complete nitrification (ammonium oxidation to nitrate): decrease of oxygen requirements for nitrification, reduction of COD demand and CO2 emissions during denitrification and higher denitrification rate and lower biomass production during anoxic growth.In this study, an extremely high-strength ammonium wastewater (3000-4000 mg N L−1) was treated in a continuous pilot plant with a configuration of three reactors in series plus a settler. The system was operated under the maximum possible volumetric nitrogen loading rate, at mild temperature (around 25 °C), with high sludge retention time (around 30 d) and significant nitrifying biomass concentration (average of 1800 ± 600 mg VSS L−1). The implemented control loops transformed the system, which was operating with complete nitrification, into a continuous partial nitrification system. Nitrite oxidizing bacteria (NOB) washout was accomplished with local control loops for pH and dissolved oxygen (DO) with proper setpoints for NOB inhibition (pH = 8.3 and DO = 1.2-1.9 mg O2 L−1) and with an inflow control loop based on Oxygen Uptake Rate (OUR) measurements, which allowed working at the maximum ammonium oxidation capacity of the pilot plant in each moment. This operational strategy maximized the difference between ammonia oxidizing bacteria (AOB) and NOB growth rates, which is the key point to achieve a fast and stable NOB washout. The results showed a stable operation of the partial nitrification system during more than 100 days and NOB washout was corroborated with fluorescence in-situ hybridization (FISH) analysis.  相似文献   

3.
Tao Yu 《Water research》2010,44(9):2823-2830
Three submerged membrane bioreactors (MBRs) were operated continuously for 230 days by feeding with synthetic inorganic wastewater (NH4+-N, 100 mg L−1) under different solids retention times (SRTs. M30d, 30 days; M90d, 90 days; Minfinite, no sludge purge) to examine the influence of SRT on nitrification performance and microbial characteristics. All the reactors could oxidize NH4+-N to NO3-N effectively without accumulation of NO2-N. M30d with the shortest SRT showed significantly higher specific ammonium oxidizing rate (SAOR, 0.22 kg NH4+-N kg−1 MLSS day−1) and specific nitrate forming rate (SNFR, 0.13 kg NO3-N kg−1 MLSS day−1) than the other two MBRs (0.12-0.14 kg NO3-N kg−1 MLSS day−1 and 0.042-0.068 kg NO3-N kg−1 MLSS day−1, respectively). Short SRT led to low extracellular polymeric substances (EPS) concentration and long operating cycle. The nitrite oxidizing bacteria (NOB) ratios by both the fluorescence in situ hybridization (FISH) (3.6% for M30d and 2.1-2.2% for M90d and Minfinite) and MPN (1.4 × 107 cells g−1 MLSS for M30d and 6.2 × 105 and 2.7 × 104 cells g−1 MLSS for M90d and Minfinite) analyses showed that M30d favored the accumulation of NOB, which was in accordance with the SNFR result. However, the ammonia oxidizing bacteria (AOB) ratios (3.5%, 3.2% and 4.9% for M30d, M90d and Minfinite) were not in accordance with the SAOR result. PCR-DGGE, clone library and FISH results showed that the fast-growing Nitrosomonas and Nitrobacter sp. were the dominant AOB and NOB, respectively for M30d, while considerable slow-growing Nitrosospira and Nitrospira sp. existed in Minfinite, which might be an important reason why Minfinite had a low SAOR and SNFR.  相似文献   

4.
This work proposes an efficient combined treatment for the decontamination of a pesticide-containing wastewater resulting from phytopharmaceutical plastic containers washing, presenting a moderate organic load (COD = 1662-1960 mg O2 L−1; DOC = 513-696 mg C L−1), with a high biodegradable organic carbon fraction (81%; BOD5 = 1350-1600 mg O2 L−1) and a remaining recalcitrant organic carbon mainly due to pesticides. Nineteen pesticides were quantified by LC-MS/MS at concentrations between 0.02 and 45 mg L−1 (14-19% of DOC). The decontamination strategy involved a sequential three-step treatment: (a) biological oxidation process, leading to almost complete removal of the biodegradable organic carbon fraction; (b) solar photo-Fenton process using CPCs, enhancing the bio-treated wastewater biodegradability, mainly due to pesticides degradation into low-molecular-weight carboxylate anions; (c) and a final polishing step to remove the residual biodegradable organic carbon, using a biological oxidation process. Treatment performance was evaluated in terms of mineralization degree (DOC), pesticides content (LC-MS/MS), inorganic ions and low-molecular-weight carboxylate anions (IC) concentrations. The estimated phototreatment energy necessary to reach a biodegradable wastewater, considering pesticides and low-molecular-weight carboxylate anions concentrations, Zahn-Wellens test and BOD5/COD ratio, was only 2.3 kJUV L−1 (45 min of photo-Fenton at a constant solar UV power of 30 W m−2), consuming 16 mM of H2O2, which pointed to 52% mineralization and an abatement higher than 86% for 18 pesticides. The biological oxidation/solar photo-Fenton/biological oxidation treatment system achieved pesticide removals below the respective detection limits and 79% mineralization, leading to a COD value lower than 150 mg O2 L−1, which is in agreement with Portuguese discharge limits regarding water bodies.  相似文献   

5.
The multi-annual carbon budget of a peat-covered catchment   总被引:1,自引:0,他引:1  
This study estimates the complete carbon budget of an 11.4 km2 peat-covered catchment in Northern England. The budget considers both fluvial and gaseous carbon fluxes and includes estimates of particulate organic carbon (POC); dissolved organic carbon (DOC); excess dissolved CO2; release of methane (CH4); net ecosystem respiration of CO2; and uptake of CO2 by primary productivity. All components except CH4 were measured directly in the catchment and annual carbon budgets were calculated for the catchment between 1993 and 2005 using both extrapolation and interpolation methods. The study shows that: Over the 13 year study period the total carbon balance varied between a net sink of − 20 to − 91 Mg C/km2/yr. The biggest component of this budget is the uptake of carbon by primary productivity (− 178 Mg C/km2/yr) and in most years the second largest component is the loss of DOC from the peat profile (+ 39 Mg C/km2/yr). Direct exchanges of C with the atmosphere average − 89 Mg C/km2/yr in the catchment. Extrapolating the general findings of the carbon budget across all UK peatlands results in an approximate carbon balance of − 1.2 Tg C/yr (± 0.4 Pg C/yr) which is larger than previously reported values. Carbon budgets should always be reported with a clear statement of the techniques used and errors involved as this is significant when comparing results across studies.  相似文献   

6.
Anaerobic wastewater treatment plants discharge dissolved methane, which is usually not recovered. To prevent emission of methane, which is a greenhouse gas, we utilized an encapsulated down-flow hanging sponge reactor as a post-treatment to biologically oxidize dissolved methane. Within 3 weeks after reactor start-up, methane removal efficiency of up to 95% was achieved with a methane removal rate of 0.8 kg COD m−3 day−1 at an HRT of 2 h. After increasing the methane-loading rate, the maximum methane removal rate reached 2.2 kg COD m−3 day−1 at an HRT of 0.5 h. On the other hand, only about 10% of influent ammonium was oxidized to nitrate during the first period, but as airflow was increased to 2.5 L day−1, nitrification efficiency increased to approximately 70%. However, the ammonia oxidation rate then decreased with an increase in the methane-loading rate. These results indicate that methane oxidation occurred preferentially over ammonium oxidation in the reactor. Cloning of the 16S rRNA and pmoA genes as well as phylogenetic and T-RFLP analyses revealed that type I methanotrophs were the dominant methane oxidizers, whereas type II methanotrophs were detected only in minor portion of the reactor.  相似文献   

7.
In this study, we investigated the efficiency of dissolved methane (D-CH4) collection by degasification from the effluent of a bench-scale upflow anaerobic sludge blanket (UASB) reactor treating synthetic wastewater. A hollow-fiber degassing membrane module was used for degasification. This module was connected to the liquid outlet of the UASB reactor. After chemical oxygen demand (COD) removal efficiency of the UASB reactor became stable, D-CH4 discharged from the UASB reactor was collected. Under 35 °C and a hydraulic retention time (HRT) of 10 h, average D-CH4 concentration could be reduced from 63 mg COD L−1 to 15 mg COD L−1; this, in turn, resulted in an increase in total methane (CH4) recovery efficiency from 89% to 97%. Furthermore, we investigated the effects of temperature and HRT of the UASB reactor on degasification efficiency. Average D-CH4 concentration was as high as 104 mg COD L−1 at 15 °C because of the higher solubility of CH4 gas in liquid; the average D-CH4 concentration was reduced to 14 mg COD L−1 by degasification. Accordingly, total CH4 recovery efficiency increased from 71% to 97% at 15 °C as a result of degasification. Moreover, degasification tended to cause an increase in particulate COD removal efficiency. The UASB reactor was operated at the same COD loading rate, but different wastewater feed rates and HRTs. Although average D-CH4 concentration in the UASB reactor was almost unchanged (ca. 70 mg COD L−1) regardless of the HRT value, the CH4 discharge rate from the UASB reactor increased because of an increase in the wastewater feed rate. Because the D-CH4 concentration could be reduced down to 12 ± 1 mg COD L−1 by degasification at an HRT of 6.7 h, the CH4 recovery rate was 1.5 times higher under degasification than under normal operation.  相似文献   

8.
Biological ammoniacal-nitrogen (NH4+-N) and organic carbon (TOC) treatment was investigated in replicated mesoscale attached microbial film trickling filters, treating strong and weak strength landfill leachates in batch mode at temperatures of 3, 10, 15 and 30 °C. Comparing leachates, rates of NH4+-N reduction (0.126-0.159 g m− 2 d− 1) were predominantly unaffected by leachate characteristics; there were significant differences in TOC rates (0.072-0.194 g m− 2 d− 1) but no trend relating to leachate strength. Rates of total oxidised nitrogen (TON) accumulation (0.012-0.144 g m− 2 d− 1) were slower for strong leachates. Comparing temperatures, treatment rates varied between 0.029-0.319 g NH4+-N m− 2 d− 1 and 0.033-0.251 g C m− 2 d− 1 generally increasing with rising temperatures; rates at 3 °C were 9 and 13% of those at 30 °C for NH4+-N and TOC respectively. For the weak leachates (NH4+-N < 140 mg l− 1) complete oxidation of NH4+-N was achieved. For the strong leachates (NH4+-N 883-1150 mg l− 1) a biphasic treatment response resulted in NH4+-N removal efficiencies of between 68 and 88% and for one leachate no direct transformation of NH4+-N to TON in bulk leachate. The temporal decoupling of NH4+-N oxidation and TON accumulation in this leachate could not be fully explained by denitrification, volatilisation or anammox, suggesting temporary storage of N within the treatment system. This study demonstrates that passive aeration trickling filters can treat well-buffered high NH4+-N strength landfill leachates under a range of temperatures and that leachate strength has no effect on initial NH4+-N treatment rates. Whether this approach is a practicable option depends on a range of site specific factors.  相似文献   

9.
We analyzed benthic fluxes of inorganic nitrogen, denitrification and dissimilatory nitrate reduction to ammonium (DNRA) rates in hypolimnetic sediments of lowland lakes. Two neighbouring mesotrophic (Ca' Stanga; CS) and hypertrophic (Lago Verde; LV) lakes, which originated from sand and gravel mining, were considered. Lakes are affected by high nitrate loads (0.2-0.7 mM) and different organic loads. Oxygen consumption, dissolved inorganic carbon, methane and nitrogen fluxes, denitrification and DNRA were measured under summer thermal stratification and late winter overturn.Hypolimnetic sediments of CS were a net sink of dissolved inorganic nitrogen (−3.5 to −4.7 mmol m−2 d−1) in both seasons due to high nitrate consumption. On the contrary, LV sediments turned from being a net sink during winter overturn (−3.5 mmol m−2 d−1) to a net source of dissolved inorganic nitrogen under summer conditions (8.1 mmol m−2 d−1), when significant ammonium regeneration was measured at the water-sediment interface. Benthic denitrification (0.7-4.1 mmol m−2 d−1) accounted for up to 84-97% of total NO3 reduction and from 2 to 30% of carbon mineralization. It was mainly fuelled by water column nitrate. In CS, denitrification rates were similar in winter and in summer, while in LV summer rates were 4 times lower. DNRA rates were generally low in both lakes (0.07-0.12 mmol m−2 d−1). An appreciable contribution of DNRA was only detected in the more reducing sediments of LV in summer (15% of total NO3 reduction), while during the same period only 3% of reduced NO3 was recycled into ammonium in CS.Under summer stratification benthic denitrification was mainly nitrate-limited due to nitrate depletion in hypolimnetic waters and parallel oxygen depletion, hampering nitrification. Organic enrichment and reducing conditions in the hypolimnetic sediment shifted nitrate reduction towards more pronounced DNRA, which resulted in the inorganic nitrogen recycling and retention within the bottom waters. The prevalence of DNRA could favour the accumulation of mineral nitrogen with detrimental effects on ecosystem processes and water quality.  相似文献   

10.
This study was aimed to understand the spatial variation of CH4 emissions from alpine wetlands in Southwest China on a field-scale in two phenological seasons, namely the peak growing season and the spring thaw. Methane emission rates were measured at 30 plots, which included three kinds of environmental types: dry hummock, Carex muliensis and Eleocharis valleculosa sites. There were highly spatial variations of methane emissions among and within different environmental types in both phenological seasons. Mean methane emission rates ranged from 1.1 to 37.0 mg CH4 m− 2 h− 1 in the peak growing season and from 0.004 to 0.691 mg CH4 m− 2 h− 1 in the spring thaw. In the peak growing season, coefficients of variation (CV) averaged 38% among environmental types and 64% within environmental types; while in the spring thaw, CV were on the average 61% among environmental types and 96% within environmental types. The key influencing factors were the standing water table and the plant community height in the peak growing season, while in the spring thaw, no significant correlations between factors and methane emissions were found.  相似文献   

11.
Lousal mine is a typical “abandoned mine” with all sorts of problems as consequence of the cessation of the mining activity and lack of infrastructure maintenance. The mine is closed at present, but the heavy metal enriched tailings remain at the surface in oxidizing conditions. Surface water and stream sediments revealed much higher concentrations than the local geochemical background values, which the “Contaminated Sediment Standing Team” classifies as very toxic. High concentrations of Cu, Pb, Zn, As, Cd and Hg occurred within the stream sediments downstream of the tailings sites (up to: 817 mg kg−1 As, 6.7 mg kg−1 Cd, 1568 mg kg−1 Cu, 1059 mg kg−1 Pb, 82.4 mg kg−1 Sb, 4373 mg kg−1 Zn). The AMD waters showed values of pH ranging from 1.9 to 2.9 and concentrations of 9249 to 20,700 mg L−1 SO4−2, 959 to 4830 mg L−1 Fe and 136 to 624 mg L−1 Al. Meanwhile, the acid effluents and mixed stream waters also carried high contents of SO42−, Fe, Al, Cu, Pb, Zn, Cd, and As, generally exceeding the Fresh Water Aquatic Life Acute Criteria. Negative impacts in the diatom communities growing at different sites along a strong metal pollution gradient were shown through Canonical Correspondence Analysis: in the sites influenced by Acid Mine Drainage (AMD), the dominant taxon was Achnanthidium minutissimum. However, Pinnularia acoricola was the dominant species when the environmental conditions were extremely adverse: very low pH and high metal concentrations (sites 2 and 3). Teratological forms of Achnanthidium minutissimum (Kützing) Czarnecki, Brachysira vitrea (Grunow) Ross in Hartley, Fragilaria rumpens (Kützing) G. W. F. Carlson and Nitzschia hantzschiana Rabenhorst were found. A morphometric study of B. vitrea showed that a decrease in size was evident at the most contaminated sites. These results are evidence of metal and acidic pollution.  相似文献   

12.
The application of microelectrodes to measure oxygen and nitrite concentrations inside granules operated at 20 °C in a CANON (Complete Autotrophic Nitrogen-removal Over Nitrite) reactor and the application of the FISH (Fluorescent In Situ Hybridization) technique to cryosectioned slices of these granules showed the presence of two differentiated zones inside of them: an external nitrification zone and an internal anammox zone. The FISH analysis of these layers allowed the identification of Nitrosomonas spp. and Candidatus Kuenenia Stutgartiensis as the main populations carrying out aerobic and anaerobic ammonia oxidation, respectively.Concentration microprofiles measured at different oxygen concentrations in the bulk liquid (from 1.5 to 35.2 mg O2 L−1) revealed that oxygen was consumed in a surface layer of 100-350 μm width. The obtained consumption rate of the most active layers was of 80 g O2 (Lgranule)−1 d−1. Anammox activity was registered between 400 and 1000 μm depth inside the granules. The nitrogen removal capacity of the studied sequencing batch reactor containing the granular biomass was of 0.5 g N L−1 d−1. This value is similar to the mean nitrogen removal rate obtained from calculations based on in- and outflow concentrations.Information obtained in the present work allowed the establishment of a simple control strategy based on the measurements of NH4+ and NO2 in the bulk liquid and acting over the dissolved oxygen concentration in the bulk liquid and the hydraulic retention time of the reactor.  相似文献   

13.
The feasibility of long-term (>3 years), low-temperature (4-15 °C) and anaerobic bioreactor operation, for the treatment of acidified wastewater, was investigated. A hybrid, expanded granular sludge bed-anaerobic filter bioreactor was seeded with a mesophilic inoculum and employed for the mineralization of moderate-strength (3.75-10 kg chemical oxygen demand (COD) m−3) volatile fatty acid-based wastewaters at 4-15 °C. Bioprocess performance was assessed in terms of COD removal efficiency (CODRE), methane biogas concentration, and yield, and biomass retention. Batch specific methanogenic activity assays were performed to physiologically characterise reactor biomass.Despite transient disimprovements, CODRE and methane biogas concentrations exceeded 80% and 65%, respectively, at an applied organic loading rate (OLR) of 10 kg COD m−3 d−1 between 9.5 and 15 °C (sludge loading rate (SLR), 0.6 kg COD kg[VSS]−1 d−1). Over 50% of the granular sludge bed was lost to disintegration during operation at 9.5 °C, warranting a reduction in the applied OLR to 3.75-5 kg COD m−3 d−1 (SLR, c. 0.4-0.5 kg COD kg[VSS]−1 d−1). From that point forward, remarkably stable and efficient performance was observed during operation at 4-10 °C, with respect to CODRE (≥82%), methane biogas concentration (>70%) and methane yields (>4 lMethane d−1), suggesting the adaptation of our mesophilic inoculum to psychrophilic operating conditions.Physiological activity assays indicated the development of psychroactive syntrophic and methanogenic populations, including the emergence of putatively psychrophilic propionate-oxidising and hydrogenotrophic methanogenic activity. The data suggest that mesophilic inocula can physiologically adapt to sub-optimal operational temperatures: treatment efficiencies and sludge loading rates at 4 °C (day, 1243) were comparable to those achieved at 15 °C (day 0). Furthermore, long-term, low-temperature bioreactor operation may act as a selective enrichment for psychrophilic methanogenic activity from mesophilic inocula. The observed efficient and stable bioprocess performance highlights the potential for long-term, low-temperature bioreactor operation.  相似文献   

14.
A bench-scale sequencing batch reactor was used to study factors affecting the endogenous decay of the ammonium oxidizing biomass (AOB) in different operating conditions. AOB decay was very sensitive to oxygen concentration, and increased up to 0.4 d−1 for oxygen concentration of 7 mg O2 L−1. The decay in anaerobic conditions was shown to be very low (0.03 d−1) when compared to literature data.The effect of nitrite and nitrate on AOB decay was also studied. The correlation was quite weak suggesting that both nitrate and nitrite absence had little impact on decay which is contrary to what is typically assumed in some of the existing process models. A simple expression for the decay of AOB was proposed, calibrated and validated using the results of batch kinetic tests and of the continuous sequencing batch reactor monitoring.  相似文献   

15.
Addition of different forms of nitrogen fertilizer to cultivated soil is known to affect carbon dioxide (CO2) and nitrous oxide (N2O) emissions. In this study, the effect of urea, wastewater sludge and vermicompost on emissions of CO2 and N2O in soil cultivated with bean was investigated. Beans were cultivated in the greenhouse in three consecutive experiments, fertilized with or without wastewater sludge at two application rates (33 and 55 Mg fresh wastewater sludge ha− 1, i.e. 48 and 80 kg N ha− 1 considering a N mineralization rate of 40%), vermicompost derived from the wastewater sludge (212 Mg ha− 1, i.e. 80 kg N ha− 1) or urea (170 kg ha− 1, i.e. 80 kg N ha− 1), while pH, electrolytic conductivity (EC), inorganic nitrogen and CO2 and N2O emissions were monitored. Vermicompost added to soil increased EC at onset of the experiment, but thereafter values were similar to the other treatments. Most of the NO3 was taken up by the plants, although some was leached from the upper to the lower soil layer. CO2 emission was 375 C kg ha− 1 y− 1 in the unamended soil, 340 kg C ha− 1 y− 1 in the urea-amended soil and 839 kg ha− 1 y− 1 in the vermicompost-amended soil. N2O emission was 2.92 kg N ha− 1 y− 1 in soil amended with 55 Mg wastewater sludge ha− 1, but only 0.03 kg N ha− 1 y− 1 in the unamended soil. The emission of CO2 was affected by the phenological stage of the plant while organic fertilizer increased the CO2 and N2O emission, and the yield per plant. Environmental and economic implications must to be considered to decide how many, how often and what kind of organic fertilizer could be used to increase yields, while limiting soil deterioration and greenhouse gas emissions.  相似文献   

16.
Gross CO2 and CH4 emissions (degassing and diffusion from the reservoir) and the carbon balance were assessed in 2009-2010 in two Southeast Asian sub-tropical reservoirs: the Nam Ngum and Nam Leuk Reservoirs (Lao PDR). These two reservoirs are within the same climatic area but differ mainly in age, size, residence time and initial biomass stock. The Nam Leuk Reservoir was impounded in 1999 after partial vegetation clearance and burning. However, GHG emissions are still significant 10 years after impoundment. CH4 diffusive flux ranged from 0.8 (January 2010) to 11.9 mmol m− 2 d− 1 (April 2009) and CO2 diffusive flux ranged from - 10.6 (October 2009) to 38.2 mmol m− 2 d− 1 (April 2009). These values are comparable to other tropical reservoirs. Moreover, degassing fluxes at the outlet of the powerhouse downstream of the turbines were very low. The tentative annual carbon balance calculation indicates that this reservoir was a carbon source with an annual carbon export (atmosphere + downstream river) of about 2.2 ± 1.0 GgC yr− 1.The Nam Ngum Reservoir was impounded in 1971 without any significant biomass removal. Diffusive and degassing CO2 and CH4 fluxes were lower than for other tropical reservoirs. Particularly, CO2 diffusive fluxes were always negative with values ranging from - 21.2 (April 2009) to - 2.7 mmol m−2 d−1 (January 2010). CH4 diffusive flux ranged from 0.1 (October 2009) to 0.6 mmol m−2 d−1 (April 2009) and no degassing downstream of the turbines was measured. As a consequence of these low values, the reservoir was a carbon sink with an estimated annual uptake of - 53 ± 35 GgC yr−1.  相似文献   

17.
Chlorophenols are used worldwide as broad-spectrum biocides and fungicides. They have half-life times in water from 0.6 to 550 h and in sediments up to 1700 h and, due to their numerous origins, they can be found in wastewaters, groundwaters or soils. Moreover, chlorophenols are not readily biodegradable.Recently, classic Advanced Oxidation Processes (AOP) have been proposed for their abatement in an aqueous solution. This paper investigates the oxidation of 2,4-dichlorophenol and 3,4-dichlorophenol, at starting concentrations of 6.1 · 10−5 mol L−1, in aqueous solutions through Fe(III)/O2 homogeneous photocatalysis under UV light (303 ÷ 366 nm). The Fe(III)/O2 homogeneous photocatalysis is less expensive than using H2O2 due to the capability of Fe(III) to produce OH radicals, if irradiated with an UVA radiation, and of oxygen to re-oxidize ferrous ions to ferric ones when dissolved in solution. The results show that the best working conditions, for both compounds, are found for pH = 3.0 and initial Fe(III) concentration equal to 1.5·10−4 mol L−1 although the investigated oxidizing system can be used even at pH close to 4.0 but with slower abatement kinetics. Toxicity assessment on algae indicates that treated solutions of 2,4-dichlorophenol are less toxic on algae Pseudokirchneriella subcapitata if compared to not treated solutions whereas in the case of 3,4-dichlorophenol only the samples collected during the runs at 20 and 60 min are capable of inhibiting the growth of the adopted organism.The values of the kinetic constant for the photochemical re-oxidation of iron (II) to iron (III) and for HO attack to intermediates are evaluated by a mathematical model for pH range of 2.0-3.0 and initial Fe(III) concentrations range of 1.5 · 10−5-5.2 · 10−4 mol L−1.  相似文献   

18.
Riparian wetlands bordering intensively managed agricultural fields can act as biological filters that retain and transform agrochemicals such as nitrate and pesticides. Nitrate removal in wetlands has usually been attributed to denitrification processes which in turn imply the production of greenhouse gases (CO2 and N2O). Denitrification processes were studied in the Salburua wetland (northern Spain) by using undisturbed soil columns which were subsequently divided into three sections corresponding to A-, Bg- and B2g-soil horizons. Soil horizons were subjected to leaching with a 200 mg NO3 L− 1 solution (rate: 90 mL day− 1) for 125 days at two different temperatures (10 and 20 °C), using a new experimental design for leaching assays which enabled not only to evaluate leachate composition but also to measure gas emissions during the leaching process. Column leachate samples were analyzed for NO3 concentration, NH4+ concentration, and dissolved organic carbon. Emissions of greenhouse gases (CO2 and N2O) were determined in the undisturbed soil columns. The A horizon at 20 °C showed the highest rates of NO3 removal (1.56 mg N-NO3 kg−1 DW soil day− 1) and CO2 and N2O production (5.89 mg CO2 kg−1 DW soil day− 1 and 55.71 μg N-N2O kg−1 DW soil day− 1). For the Salburua wetland riparian soil, we estimated a potential nitrate removal capacity of 1012 kg N-NO3 ha− 1 year− 1, and potential greenhouse gas emissions of 5620 kg CO2 ha− 1 year− 1 and 240 kg N-N2O ha− 1 year− 1.  相似文献   

19.
Pilot-scale struvite crystallization tests using anaerobic effluent from potato processing industries were performed at three different plants. Two plants (P1 & P2) showed high phosphate removal efficiencies, 89 ± 3% and 75 ± 8%, resulting in final effluent levels of 12 ± 3 mg PO43−-P L−1 and 11 ± 3 mg PO43−-P L−1, respectively. In contrast, poor phosphate removal (19 ± 8%) was obtained at the third location (P3). Further investigations at P3 showed the negative effect of high Ca2+/PO43−-P molar ratio (ca. 1.25 ± 0.11) on struvite formation. A full-scale struvite plant treating anaerobic effluent from a dairy industry showed the same Ca2+ interference. A shift in the influent Ca2+/PO43−-P molar ratio from 2.69 to 1.36 resulted in average total phosphorus removal of 78 ± 7%, corresponding with effluent levels of 14 ± 4 mg Ptotal L−1 (9 ± 3 mg PO43−-P L−1). Under these conditions high quality spherical struvite crystals of 2-6 mm were produced.  相似文献   

20.
The presence of 28 antibiotics in three hospital effluents, five wastewater treatment plants (WWTPs), six rivers and a drinking water storage catchment were investigated within watersheds of South-East Queensland, Australia. All antibiotics were detected at least once, with the exception of the polypeptide bacitracin which was not detected at all. Antibiotics were found in hospital effluent ranging from 0.01-14.5 μg L− 1, dominated by the β-lactam, quinolone and sulphonamide groups. Antibiotics were found in WWTP influent up to 64 μg L− 1, dominated by the β-lactam, quinolone and sulphonamide groups. Investigated WWTPs were highly effective in removing antibiotics from the water phase, with an average removal rate of greater than 80% for all targeted antibiotics. However, antibiotics were still detected in WWTP effluents in the low ng L− 1 range up to a maximum of 3.4 μg L− 1, with the macrolide, quinolone and sulphonamide antibiotics most prevalent. Similarly, antibiotics were detected quite frequently in the low ng L− 1 range, up to 2 μg L− 1 in the surface waters of six investigated rivers including freshwater, estuarine and marine samples. The total investigated antibiotic concentration (TIAC) within the Nerang River was significantly lower (p < 0.05) than all other rivers sampled. The absence of WWTP discharge to this river is a likely explanation for the significantly lower TIAC and suggests that WWTP discharges are a dominant source of antibiotics to investigated surface waters. A significant difference (p < 0.001) was identified between TIACs at surface water sites with WWTP discharge compared to sites with no WWTP discharge, providing further evidence that WWTPs are an important source of antibiotics to streams. Despite the presence of antibiotics in surface waters used for drinking water extraction, no targeted antibiotics were detected in any drinking water samples.  相似文献   

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