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1.
Many industrialized regions in the world are faced with local overproductions of animal manure requiring processing in an economic sound manner. Intensive animal production in Flanders and the Netherlands has resulted in a considerable overproduction of animal manure. Spreading the excess manure over arable land has resulted in contamination and eutrophication of groundwater and surface waters. Over the last 4 years, research was conducted towards the potential of more economic constructed wetlands for the final treatment step. Although, initial results with laboratory flow field experiments were insufficient to reach stringent discharge criteria (Meers et al., Water Air Soil Pollut 160:15–26, 2005a), progressive optimisation of the tertiary treatment as well as of the preceding conditioning has resulted in a consistently performing pilot scale system (1,000 m3 year?1 capacity) with effluent concentrations below the discharge criteria of 15 mg l?1 N, 2 mg l?1 P and 125 mg l?1 COD (chemical oxygen demand), at a cumulated cost (operational plus investment) of 3–4 € m?3 of pre-treated pig manure. Construction of full-scale installations with annual capacity of 10,000–25,000 m3 based on this pilot model are scheduled, with the first installation currently under way. The concept has the potential to provide a low cost, in situ treatment system allowing animal farmers to process excess animal manure themselves without the requirement of expensive ex situ treatment based on industrial scale membrane technology facilities. This paper presents the research findings of the first year of the pilot scale installation.  相似文献   

2.
As an alternative to thermal pasteurization, pulsed electric fields (PEF) were applied to apple juices on laboratory and pilot plant scale, investigating the effects on juice quality. PEF application still falls under the EU Novel Food Regulation. Consequently, extensive investigation of quality parameters is a prerequisite to prove substantial equivalence of juices resulting from the novel process and conventional production, respectively. Juice composition was not affected by PEF treatment. However, browning of the juices provided evidence of residual enzyme activities. On laboratory scale, complete deactivation of peroxidase (POD) and polyphenoloxidase (PPO) was achieved when PEF treatment and preheating of the juices to 60 degrees C were combined. Under these conditions, a synergistic effect of heat and PEF was observed. On pilot plant scale, maximum PPO deactivation of 48% was achieved when the juices were preheated to 40 degrees C and PEF-treated at 30 kV/cm (100 kJ/kg). Thus, minimally processed juices resulted from PEF processing, when applied without additional conventional thermal preservation. Since this product type was characterized by residual native enzyme activities and nondetectable levels of 5-hydroxymethylfurfural, also when preheating up to 40 degrees C was included, it ranged between fresh and pasteurized juices regarding consumers' expectation of freshness and shelf life. Consistent with comparable iron contents among all juice samples, no electrode corrosion was observed under the PEF conditions applied.  相似文献   

3.
This paper presents the main results obtained using the heterogeneous photocatalysis with TiO2 technology in the removal of the emerging contaminant benzophenone-3 at pilot plant scale in a cylinder parabolic solar collector. In this sense, the effects of the operational parameters, pH and catalyst concentration, were analyzed, and after the use of the response surface methodology, the conditions that, under the experimental range, conduct to a higher removal of the analyte were selected. Additionally, analysis of the total organic carbon content and the biodegradability index (relationship between BDO5 and COD) of the treated samples were carried out. In general, results allowed us to infer that this kind of treatment is effective in removing a considerable percentage of the substrate, and that it could become an effective alternative to water treatment and decontamination.  相似文献   

4.
This paper presents a comparative study of the performance of ferrate(VI), FeO 4 2? , and ferric, Fe(III), towards wastewater treatment. The ferrate(VI) was produced by electrochemical synthesis, using steel electrodes in a 16 M NaOH solution. Domestic wastewater collected from Hailsham North Wastewater Treatment Works was treated with ferrate(VI) and ferric sulphate (Fe(III)). Samples were analysed for suspended solids, chemical oxygen demand (COD), biochemical oxygen demand (BOD) and P removal. Results for low doses of Fe(VI) were validated via a reproducibility study. Removal of phosphorous reached 40% with a Fe(VI) dose as low as 0.01 mg/L compared to 25% removal with 10 mg/L of Fe(III). For lower doses (<1 mg/L as Fe), Fe(VI) can achieve between 60% and 80% removals of SS and COD, but Fe(III) performed even not as well as the control sample where no iron chemical was dosed. The ferrate solution was found to be stable for a maximum of 50 min, beyond which Fe(VI) is reduced to less oxidant species. This provided the maximum allowed storage time of the electrochemically produced ferrate(VI) solution. Results demonstrated that low addition of ferrate(VI) leads to good removal of P, BOD, COD and suspended solids from wastewater compared to ferric addition and further studies could bring an optimisation of the dosage and treatment.  相似文献   

5.
Constructed wetlands have been recognized as offering a removal treatment option for high concentrations removal of chemical and biological contaminants in domestic wastewater. The enteric protozoan parasite Cryptosporidium is considered one of the highly resistant to treatment and highly infectious organisms to humans and animals. Moreover, some species of Cryptosporidium are known to have a zoonotic nature. In this investigation a pilot scale for domestic wastewater treatment system was used, consisting of the following steps in series: (1) up-flow anaerobic sludge blanket (UASB) reactor, (2) free water surface (FWS) wetland unit, and (3) sub-surface flow (SSF) wetland unit. This treatment system was fed with domestic wastewater to assess its efficiency in removing Cryptosporidium oocysts. The obtained Cryptosporidium oocysts were detected and enumerated by two different staining techniques ‘acid fast trichrome (AFT) and modified Ziehl Neelsen (MZN) stains’. Polymerase chain reaction (PCR) technique was also used to detect Cryptosporidium DNA in wastewater samples. Results revealed that anaerobic treatment (using UASB reactor) could remove about 53.1% of Cryptosporidium oocysts present in raw wastewater. The in-series connection between the two wetland units allowed complete elimination of Cryptosporidium oocysts as the first (FWS) wetland unit removed 95.9% of the oocysts present in anaerobically treated wastewater and the remaining portion of oocysts was completely removed by the second (SSF) wetland unit. Cryptosporidium oocysts were detected in 95.8% of raw wastewater samples with a mean count of 43.8 oocysts/l when AFT stain was used while they were detected in only 87.5% of raw wastewater samples with a mean count of 35.6 oocysts/l when MZN stain was used. Polymerase chain reaction (PCR) technique was able to detect Cryptosporidium DNA in only 45.8% of raw wastewater samples. Positive PCR results were only achieved in wastewater samples containing 52 oocysts or more per liter.  相似文献   

6.
This paper presents the results of using a pilot-scale-constructed wetland as a tertiary system to simulate the treatment conditions of wastewater effluents from the metal-mechanical industry, aiming to achieve the Brazilian legal standards of phosphorus and nitrogen emission. The macrophytes were placed in 1 m3 polyethylene tanks, daily estimating the treatment of 2 m3 of effluents. The effluents were circulated in a horizontal subsurface flow through a porous matrix of thick sand and gravel, in which the roots of the macrophytes of the species Reed (Scirpus sp.) and Cattail (Typha sp.) were fixed. Monitoring of the pilot plant was performed through a battery of physical?Cchemical and biological analyses. Despite the load variations and operational problems, the system presented a positive degree of pollutant efficiency removal, especially for phosphorus (73% medium), TKN (61% medium), and NH4?CN (56% medium). Peak results were achieved during the last 3 months of monitoring. The chemical analysis of the support layer, plus the root system and aerial portion of the plants, revealed that these wastes could be used as fertilizer.  相似文献   

7.
植物化感作用及其在草地农业生态系统中的应用   总被引：1，自引：0，他引：1  
植物化感作用作为一种自然的生态现象,在自然界中普遍存在.目前对植物化感作用的研究主要集中在化感物质的分离、鉴定、释放途径、作用机理及化感作用对农、林、牧等草地农业生态系统持续发展的应用潜力等方面.但化感作用在草地农业中的具体作用和应用还缺乏深入系统地概述.为探明化感作用在草地农业生态系统的作用,本文从植物化感作用的物质...  相似文献   

8.
The present study aims to investigate the performance of potassium ferrate(VI) in treating decentralized domestic sewage from a rural scattered residential area. Major results were that around 90% of total phosphorus (TP) and 40% of chemical oxygen demand (COD) could be reduced when 25 mg L?1 of ferrate(VI) was applied. The removal of ammonia and total nitrogen (NH3–N and TN) was also monitored. However, the nitrogen removal during the chemical dosing was rather low. Big fluctuations of removal rates were observed against shock pollutants concentrations. Considering its strong ability in removing emerging organic pollutants and P, ferrate(VI) is competitive in the treatment of decentralized domestic sewage as an advanced treatment unit following some traditional treatment units.  相似文献   

9.
The starch manufacturing industrial units, such as sago mills,both in medium and large scale, suffer from inadequate treatment and disposal problems due to high concentration of suspended solids present in the sludge. A laboratory scale study was conducted to investigate the viability of anaerobic treatment of sago waste sludge, enriched in particulate organicmatter, using a fluidized bed reactor. The start-up of the reactor was carried out using a mixture of digested supernatantsewage sludge and cow dung slurry in different proportions. The effect of operating variables such as COD of the effluent, bed expansion, minimum fluidization velocity on efficiency oftreatment and recovery of biogas was investigated. The maximum efficiency of treatment was found to be 82% and the nitrogen enriched digested sludge was recommended for agricultural use. A kinetic model was developed for the degradation of particulate organic matter using the general kinetic equation [dS/dt = K HC SXC] which allowed for a more accurate mathematical representation of the hydrolysis process. Analysing data from a series of batch tests, the best fit value of C was found to be in the range 0.43 to 0.62.  相似文献   

10.
Diversity of plant species and the species composition (identity) are known to influence below-ground diversity. In this paper we examine the effects of plant species diversity (richness and evenness), rates of nitrogen application and planting density, on earthworm community structure in grassland. The study was carried out at three sites in Ireland using a Simplex experimental design to define the compositions of the experimental plant communities used.A negative relationship was detected between diversity (evenness) of plant species and diversity of earthworms in the soils. However, plant species identity also affected the structure of the earthworm assemblage. In particular, the legume, Trifolium repens had a strong effect but this was conditional on the rate of nitrogen application. No earthworm species favoured communities dominated by slow growing grasses (Phleum pratense and Dactylis glomerata) (P = 0.02).Higher N inputs reduced earthworm abundance and biomass under T. repens. Earthworm richness, was negatively influenced by elevated amounts of N inputs. No effect of planting density was detected but this factor also did not affect plant biomass production.  相似文献   

11.
Lime-N (calcium cyanamide, CaCN2) acts as both fertilizer and pesticide. Lime-N may reduce nitrous oxide (N2O) emission from soil, although its effectiveness and the relative mechanisms are not well understood. The aim of the study was to quantify the effect of lime-N on N2O emission from the acidic soil of tea fields. The study design consisted of two treatments: conventional fertilizer (CF) (application of conventional organo-chemical fertilizer) and lime-N (LN) (application of approximately 53 % of the applied N as lime-N and the remaining as conventional organo-chemical fertilizer). Both treatments had the same amount of N, P2O5, and K2O applied to soil between plant canopies; fertilizer was incorporated into soil. We measured N2O emissions and environmental and microbial parameters of soil between plant canopies and under the canopy of tea plants, including the concentrations of dicyandiamide and cyanamide derived from lime-N. Nitrous oxide emission from soil between plant canopies was lower in the LN treatment than in the CF treatment, and soil ammonium oxidation activity and soil denitrification rate decreased after lime-N application. We applied the acetylene inhibition technique and analyzed isotopomer ratios of N2O; the results of both techniques suggested that denitrification was the major process of N2O production in the soil between plant canopies, despite relatively low water-filled pore space. Cumulative N2O emission over the 366 days of the experiment was 36.0 % lower in the LN treatment than in the CF treatment (P?<?0.05). Our results suggest that lime-N application decreases N2O emission by inhibiting both nitrification and denitrification processes in the acidic soil.  相似文献   

12.
We studied the effects of in situ remediation of a heavy metal (HM) contaminated soil on some soil chemical properties, microbial function and microbial structural diversity after 18 months. The experiment was carried out at semifield scale in containers filled with HM contaminated soil from the Aznalcóllar mine accident (Southern Spain, 1998). The remediation measures consisted of the application of different amendments and/or establishment of a plant cover (Agrostis stolonifera L.). Seven treatments were established: four organic treatments (municipal waste compost (MWC), biosolid compost (BC), leonardite (LEO) and litter (LIT)), one inorganic treatment (sugar beet lime (SL)) and two controls (control with plant cover (CTRP) and control without plant cover (CTR)). Several soil chemical (pH, soluble HM, total organic C (TOC), water-soluble C (WSC) and available-P) and biochemical properties (microbial biomass C (MBC), MBC/TOC ratio and enzyme activities) were determined. Microbial community structure was studied by means of ARDRA (amplified ribosomal DNA restriction analysis). The SL, MWC and BC treatments were the most efficient to raise soil pH and decrease soluble HM concentrations. Total organic C was increased in the organic treatments by 2 to 4-fold, whereas water-soluble C was statistically similar in the CTRP, SL and the organic treatments, probably due to the presence of a root system in all these treatments. Available-P was also increased in the BC, SL and MWC treatments due to the higher P content of the amendments applied in these treatments. Soil microbial function was generally enhanced in the amended and CTRP treatments. The MWC, BC and SL treatments were particularly efficient to increase microbial biomass C, the MBC/TOC ratio and the dehydrogenase and aryl-sulphatase enzyme activities. These results could be attributed to the amelioration of some of the soil chemical properties: increase in soil pH and water-soluble C and decrease of HM soluble concentrations. ARDRA analyses showed changes in structural diversity in both the bacterial and fungal community under the different treatments. Fingerprinting patterns of the 16S rDNA obtained with Hinf-I and of the 18S rDNA with Hpa-II revealed higher similarity percentages among samples from the same treatment compared with samples from the other treatments. In addition, a higher similarity was found between samples from all treatments under the Agrostis influence. The use of certain amendments and/or a plant cover is important for in situ remediation of HM contaminated soils, since these practices can affect soil chemical properties, as well as the microbial community function and structure.  相似文献   

13.
针对目前厌氧发酵中沼液沼渣量大难处理、原料预处理难、耗水量大、原料适应性差等问题,导致沼气工程运行成本高、效率低、劳动强度大、费工费时,该文设计一种柔性膜覆盖车库式厌氧干法发酵系统,可适用于多元有机物料混合厌氧发酵。该系统是将国外车库式干发酵技术和国内柔性膜覆盖技术耦合研制而成,根据厌氧干发酵生产工艺要求,确定了该发酵系统关键结构参数和运行工作参数,进行了干发酵库体的结构设计、冬季发酵增温系统设计、喷淋强化传质传热系统设计与试验。通过生产应用表明:干发酵库体的结构设计合理,增温系统设计能够满足干发酵工程冬季增温工艺要求,喷淋系统能够达到传质传热目的,发酵系统运行状况良好,产气率为0.81 m~3/(m~3·d),CH_4体积分数为67%,原料降解率为48%,该发酵系统运行稳定、可靠,大大提升了处理农村有机废弃物的能力,促进了厌氧干发酵技术的持续、健康、快速发展。  相似文献   

14.

Background, aim, and scope

An innovative stabilization/solidification (S/S) process using high-performance additivated concrete technology was developed for remediating soil contaminated by metals from abandoned industrial sites. In order to verify the effectiveness of this new ex situ S/S procedure, an area highly contaminated by metallic pollutants (As, Cd, Hg, and Pb), due to the uncontrolled discharge of waste generated from artistic glass production on the island of Murano (Venice, Italy), was selected as a case study. The technique transforms the contaminated soil into an aggregate material suitable for reuse as on-site backfill. This paper reports the main results of the demonstration project performed in collaboration with the local environmental protection agency (ARPAV).

Materials and methods

An ex situ treatment for brownfield remediation, based on the transformation of contaminated soil into very dense, low porous, and mechanically resistant granular material, was set up and tested. Specific additives (water reducers and superplasticizers) to improve the stabilized material properties were developed and patented. A demonstration plant assembled on the study area to treat 6 m3 h–1was then tested. After excavation, the contaminated soil was screened to remove coarse material. The fraction Ø?>?4 mm (coarse fraction), mainly composed of glass, brick, concrete, and stone debris, was directly reused on site after passing through a washing treatment section. The highly polluted fraction Ø?≤?4 mm (fine fraction) was treated in the S/S treatment division of the plant (European patent WO/2006/097272). The fine fraction was mixed with Portland cement and additives defined on the basis of the high performance concrete technique. the mixture was then granulated in a rolling-plate system. After 28 days curing in an onsite storage area to allow for cement hydration, the stabilized material was monitored before its in situ relocation. The chemical, mechanical, and ecotoxicological reliability and performance of the treatment was checked. Metal leachability was verified according to four leaching test methods: Italian Environmental Ministry Decree (1998), EN 12457 (2002) tout court, amended only with MgSO4 and, lastly, with artificial sea water. The mechanical properties were measured according to BS (1990) and AASHTO (1999) to obtain the Aggregate Crushing Value and California Bearing Ratio, in that order. Moreover, leachate samples prepared with artificial seawater were assessed via the Crassostrea gigas embryotoxicity test and Vibrio fischeri bioluminescence inhibition test to discriminate the presence of potential ecotoxicological effects for the brackish and saltwater biota.

Results

Outcomes from all leachate samples highlighted the effectiveness of the remediation treatment, fully complying with the Italian legislation for non-hazardous material reuse under a physicochemical viewpoint. The stabilized granular material demonstrated high mechanical strength, low porosity, and leachability. Moreover, ecotoxicological surveys indicated the presence of low toxicity levels in leachate samples according to both toxicity tests.

Discussion

Remediated soil samples revealed a significant decrease in leachability of heavy metals as a consequence of the application of additivated cement that enhanced granular material properties, resulting in improved compactness due to the reduction in water content. The toxicity data confirmed this state-of-the-art technique, indicating that leachates could be deemed as minor acutely toxic.

Conclusions

The proposed S/S treatment proved to be able to remediate soil contaminated by heavy metals through trapping pollutants in pellet materials presenting adequate physicochemical, mechanical, and ecotoxicological properties in order to prevent leachability phenomena, their reclamation, and reuse being made easier by its granular form.

Recommendation and perspectives

This project foresees long-term monitoring activity over several years (until 2014) to consider treatment durability.  相似文献   

15.
A meso-scale pilot plant was set up to test the efficiency of a phytoremediation technique applied to slightly contaminated marine sediments dredged from the port of Livorno (central Italy). The technique applied involved the use of plants (a grass species, Paspalum vaginatum and a shrub species, Tamarix gallica) and earthworms (Eisenia foetida sp.) in order to recreate an active ecosystem in which plants, micro- and macroorganisms could interact with each other through the rhizosphere, for the adsorption, extraction and/or degradation of pollutants. This system enables plants to grow in a fine textured and salt medium highly unsuitable for plant species, and a physical, chemical and biological amelioration of the matrix was observed at the end of the experimentation (after 9 months). The sediment was bio-physically pre-conditioned by mixing it with calcareous material from excavating activities (5:1?v/v) and applying green compost. The presence of microorganisms in the rhizosphere and the earthworms produced a reduction by about 50% of the initial total petroleum hydrocarbon content. The use of a natural chelator with phyto-hormonal properties (humic substances) showed their capability of forming stable complexes, especially with Pb, and their contribution as an agronomic fertiliser. The combined effect of the P. vaginatum and T. gallica in the extraction of heavy metals from the sediment showed promisingly high percentages of metal effectively extracted in comparison with its available fraction (e.g. available Ni = 6.2%; Ni extracted = 15.7%). The technique proposed could be promising for an operational re-use of dredged marine sediments for agricultural purposes, a suitable final destination for the great majority of these contaminated materials from rivers and harbour docks.  相似文献   

16.
Cleome gynandra is one of the most promising African leafy vegetables consumed in most parts of Africa. The crop is a rich source of vitamins A and C and minerals such as calcium, iron, magnesium and protein. The leaves and seeds of spider plant are used in indigenous medicine in several countries. Despite the numerous nutritive benefits and ethnopharmacological uses of the plant, C. gynandra is still underutilized due to lack of awareness and promotion of production technologies and utilization. Available information is limited and short on several relevant and rudimentary components. Hence, this review focuses on the current knowledge on C. gynandra, with regards to its botany, ecology, cultivation systems, utilization, nutraceutical properties as well as the breeding avenues that will contribute to promoting the species, aimed at ensuring food and nutritional security and efficient management of its genetic resources. Breeding programmes aimed at minimizing the bitterness of the leaves so to arouse the interest of consumers, and the mechanisms involved in the responses and adaptation of C. gynandra as a C4 plant to salinity stress, were also explored.  相似文献   

17.
This study identifies the potential use of the combined application of hardwood-derived biochar (BC) and phytohormone-producing endophytes for enhancing crop production under heavy metal stress. For this purpose, the endophyte Galactomyces geotrichum WLL1 was isolated from Trapa japonica inhabiting a Korean river whose rainfall catchment area included an abandoned zinc mine. Pyrolyzed BC derived from pine hardwoods was obtained commercially. Under growth chamber conditions, the combined or individual application of G. geotrichum WLL1 and BC (15 % w/w) significantly improved soybean growth with or without excess Zn (5,253.6 mg kg?1). The beneficial effect of treatments was observed in the low uptake of Zn by different plant tissues and its immobilization in the soil. Biochar and G. geotrichum WLL1 shared their beneficial properties synergistically and improved plant growth characteristics with or without Zn heavy metal stress (HMS). Further, intensive root colonization of G. geotrichum WLL1 in the presence of BC was observed irrespective of HMS. Most interestingly, BC and G. geotrichum WLL1 had a priming effect by inducing systemic resistance in soybeans as revealed by significantly large amounts of jasmonic acid. These properties of BC could be exploited under abiotic and biotic stress. Here, for the first time, the combined application of hardwood-derived BC and phytohormone-producing endophytes is recommended for environmentally friendly and cost-effective crop production under HMS.  相似文献   

18.
-  Dedicated to Prof. Dr. Ulrich Förstner on his 65th birthdayBackground, Aims and Scope   Sediments in harbours and nearby shipyards demonstrate widespread contamination with tributyltin (TBT). Therefore, reuse and relocation of dredged material from these locations are prohibited. Even if the International Marine Organization (IMO) convention concerning TBT-based paints is ratified (Champ, 2003) the TBT problem in sediments will continue to remain for many years due to the persistence of TBT. Methods   An electrochemical process has been developed to treat polluted sediments. Dredged materials with high and low TBT-contents were studied on a technical and a pilot scale. The treatment process was assessed by chemical analysis and a biotest battery. Additionally, an economic analysis was performed to check the economic feasibility of the process to treat dredged material from two different locations at different operating conditions. Furthermore an up-scaling estimation was performed to evaluate treatment costs at a larger scale, i.e. for a plant having a capacity of 720 000 t/a.Results and Discussion   Butyltin species and polycyclic aromatic hydrocarbons (PAH) were decomposed due to electrochemically-induced oxidation, while the treatment did not alter heavy metal and PCB concentrations. The bacteria luminescence test indicated a reduced toxicity after the electrochemical treatment, while the algae growth inhibition test and bacteria contact test did not confirm these results. Based on a small consumer price of €0.12/kWh, treating the high-contaminated sediment in the pilot plant would cost €21/m3 and €31/m3 for the low contaminated sediment, respectively. Assuming an industrial consumer price of €0.06/kWh for electricity in an up-scaled process with a capacity of 720 000t/a, the total treatment costs for the low contaminated sediment would be €13/m3. Conclusion   The results of treating dredged material from Bremerhaven and the fine-grained fraction from the METHA plant show that the effectiveness of the process performance is more related to the binding form and sediment composition than to the initial concentration of TBT. The electrochemically treated material complies with chemical criteria for relocation of dredged material, but post-treatment, e.g. washing and/or reduction of remaining oxidants with Fe-II-salts, is needed to fulfil ecotoxicological criteria for relocation. Economic investigations have shown that the electrochemical treatment might be a technical option to treat TBT contaminated, dredged material. However, the technique is not fully developed and cannot remove all chemicals of concern, e.g. heavy metals. The decision as to whether this technique can be applied is site-specific and should be taken based on the case-by-case approach.Recommendation and Outlook   Since biotests integrate the effects of all contaminants present in a sample, process-accompanying evaluation procedures need additional assessment methods such as TIE (toxicity identification evaluation) as a second tier following ecotoxicological tests, in which the reasons for the effects are identified. For reasons of sustainability, a much more effect-oriented and long-term cost effective approach should be applied in future to avoid the release of harmful substances into the environment. Life cycle assessment should be carried out to identify and quantify impacts of sediment treatment processes in order to take into account both the distant effects of local actions and local effects of distant actions.  相似文献   

19.
Electrochemistry can be a valuable instrument to preserve the aquatic environment, first, by elucidating the oxidation-reduction mechanisms of substances having toxicological potential at laboratory scale; second, by aiding through extrapolation to comprise the evolution and fate in the environment of these pollutants and, finally, by establishing the basis of some electrochemical deactivation processes at industrial scale. In this way, this paper deals on studies of a type of highly pollutant substances for the aquatic media such as the S-triazines. The first part of the paper is focused to show the electrochemical reduction behavior of some S-triazines (eleven compounds have been studied). Later, the probable consequences at natural scale of these electroreductive processes are evaluated. Thus, the electrochemical reduction of diluted solutions of s-triazine herbicides and parent compounds takes place at potentials of ?0.90 to ?1.20 V, at very acidic pH values. The electroreduction products generated in all cases have loss the aromaticity and, depending on the compound, the chlorine atom or the –SCH3 group. So, the resulting molecules present lower toxicity than the original compounds. For this reason, the electroreductive way can be an efficient option for the detoxification of S-triazine polluted waters. On the other hand, the natural deactivation of the s-triazines present in natural waters, in addition to the conventional photooxidative route taking place in well illuminated and oxygenated waters, could take place through the reductive process when the waters are essentially anoxic, acidic, and rich in suspended materials. This natural reduction, moreover, could favour the later oxidation or metabolization of the byproducts emanating of the original plaguicides. Finally, the reduction of S-triazines, both forced (industrial water depuration via electrochemical reduction) and no forced (natural aquatic media) requires more negative redox potentials, that is, more reductive environments as the molecules become more complex.  相似文献   

20.
This study has investigated how to simultaneously remove both heavy metals (Cu, Mn, and Zn) and natural organic matters (NOM; humic acid and fulvic acid) from river water using potassium ferrate (K2FeO4), a multipurpose chemical acting as oxidant, disinfectant, and coagulant. In water sample including each 0.1 mM heavy metal, its removal efficiency ranged 28–99% for Cu, 22–73% for Mn, and 18–100% for Zn at the ferrate(VI) doses of 0.03–0.7 mM (as Fe). The removal efficiency of each heavy metal increased with increasing pH, whereas an overall temperature did not make any special effect on the reaction between the heavy metal and ferrate(VI). A high efficiency was achieved on the simultaneous treatment of heavy metals (0.1 mM) and NOM (10 mg/l) at the ferrate(VI) doses of 0.03–0.7 mM (as Fe): 87–100% (Cu), 31–81% (Mn), 11–100% (Zn), and 33–86% (NOM). In the single heavy metal solution, the optimum ferrate dose for treating 0.1 mM Cu or Mn was 0.1 mM (as Fe), while that for treating 0.1 mM Zn was 0.3 mM (as Fe). In the mixture of three heavy metals and NOM, on the other hand, 0.5 mM (as Fe) ferrate(VI) was determined as an optimum dose for removing both 0.1 mM heavy metals (Cu, Mn, and Zn) and 10 mg/l NOM. Prior to the addition of ferrate(VI) into the solution of heavy metals and NOM (HA or FA), complexes were formed by the reaction between divalent cations of heavy metals and negatively charged functional groups of NOM, enhancing the removal of both heavy metals and NOM by ferrate(VI).  相似文献   

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