Risk minimisation of FGD gypsum leachates by incorporation of aluminium sulphate

The incorporation of aluminium sulphate to (flue gas desulphurisation) FGD gypsum before its disposal was investigated as a way to minimise the risk supposed by the high fluoride content of its leachates. Using a bath method the kinetic and equilibrium processes of fluoride removal by aluminium sulphate were studied at fluoride/aluminium molar concentration (F/Al) ratios in the range 1.75 10(-2)-1.75 under the pH conditions (about 6.5) of FGD gypsum leachates. It was found that fluoride removal was a very fast process at any of the (F/Al) ratios subject of study, with equilibrium attained within the first 15 min of interaction. High decreases in solution fluoride concentrations (50-80%) were found at the equilibrium state. The use of aluminium sulphate in the stabilization of FGD gypsum proved to greatly decrease its fluoride leachable content (in the range 20-90% for aluminium sulphate doses of 0.1-5%, as determined by the European standard EN 12457-4). Such fluoride leaching minimisation assures the characterization of this by-product as a waste acceptable at landfills for non-hazardous wastes according to the Council Decision 2003/33/EC on waste disposal. Furthermore, as derived from column leaching studies, the proposed stabilization system showed to be highly effective in simulated conditions of disposal, displaying fluoride leaching reduction values about 55 and 80% for aluminium sulphate added amounts of 1 and 2%, respectively.     

Detection of tannic acid at trace level in industrial wastewaters using a highly sensitive chemiluminescence method

A novel flow injection procedure was developed for the determination of tannic acid in industrial wastewaters based on the enhancement by tannic acid of the chemiluminescence from luminol-K3Fe(CN)6-OH- system. The method has the merits of higher sensitivity, higher selectivity, wider linear range, simpler instrumentation. It is applicable for the determination of tannic acid in the range of 3.0 x 10(-10)-1.0 x 10(-7) mol/L with a detection limit of 1.0 x 10(-10) mol/L. The relative standard deviation is 2.7% for the determination of 1.0 x 10(-8) mol/L tannic acid (n = 11). The method has been successfully used to determine tannic acid at trace level in industrial wastewaters from brewery and tannery.     

Optimisation of sulphate reduction in a methanol-fed thermophilic bioreactor

Several methods were tested to optimise sulphate reduction and minimise methane formation in thermophilic (65 degrees) expanded granular sludge bed reactors fed with a medium containing sulphate and methanol. Lowering the pH from 7.5 to 6.75 resulted in a rapid decrease of methane formation and a concomitant increase in sulphate reduction. The inhibition of methane formation was irreversible on the short-term. Lowering the COD/SO4(2-) ratio (COD: chemical oxygen demand) from 6 to 0.34 (g/g) rapidly favoured sulphate reduction over methanogenesis. Continuous addition of 2 g L(-1) 2-bromoethanesulphonate was ineffective as complete inhibition of methanogenesis was obtained only for two days. Inhibition of methanogens by sulphide at pH 7.5 was only effective when the total sulphide concentration was above 1200 mg S L(-1). For practical applications, a relatively short exposure to a slightly acidic pH in combination with operating the reactor at a volumetric methanol-COD loading rate close to the maximum volumetric sulphide-COD formation rate.     

Sulphate reduction and the removal of carbon and ammonia in a laboratory-scale constructed wetland

Sulphate is a normal constituent of domestic wastewater and reduced sulphur compounds are known to be potent inhibitors of plant growth and certain microbial activities. However, the knowledge about sulphate reduction and the effect on the removal of C and N in constructed wetlands is still limited. Investigations in laboratory-scale constructed wetland reactors were performed to evaluate the interrelation of carbon and nitrogen removal with the sulphate reduction by use of artificial domestic wastewater. Carbon removal was found to be only slightly affected and remained at high levels of efficiency (75-90%). Only at sulphate reduction intensities above 75 mgl(-1) (50% removal), a decrease of carbon removal of up to 20% was observed. A highly contrary behaviour of ammonia removal was found in general, which decreased exponentially from 75% to 35% related to a linear increase of sulphate reduction up to 75 mgl(-1) (50% removal). Since sulphate removal is considered to be dependant on the load of electron donors, the carbon load of the system was varied. Variation of the load changed the intensities of sulphate reduction immediately, but did not influence the carbon removal effectiveness. Doubling of the carbon concentration of 200 mgl(-1) BOD(5) for domestic wastewater usually led to sulphate reduction of up to 150 mgl(-1) (100% removal). The findings show that, particularly in constructed wetland systems, the sulphur cycle in the rhizosphere is of high importance for performance of the waste water treatment and may initiate a reconsideration of the amount of sulphate present in the tap water systems.     

Flow injection determination of p-aminophenol at trace level using inhibited luminol-dimethylsulfoxide-NaOH-EDTA chemiluminescence

A novel flow injection procedure was developed for the determination of p-aminophenol (PAP) based on the inhibition by PAP of the chemiluminescence from luminol-dimethylsulfoxide (DMSO)-NaOH-EDTA system. The method has merits of higher sensitivity, wider linear range, simpler procedure, and a more rapid analyzing speed. It is applicable for the determination of PAP in the range of 2.5 x 10(-10)-5.0 x 10(-8) g mL(-1) with a detection limit of 1.9 x 10(-10) g mL(-1). The relative standard deviation (RSD) for 5.0 x 10(-9) g mL(-1) PAP is 0.78% (n=15). The method has been successfully used to determine PAP in industrial wastewaters and environmental waters. Additionally, the inhibition mechanism was also discussed briefly.     

Atomic-absorption determination of barium in natural waters

We have developed the technique of the atomic-absorption determination of barium in drinking and natural waters including its concentration by coprecipitation with lead chromate, dissolution of deposits and measuring atomic adsorption in the acetylene-dinitroxide flame. The concentration coefficient is equal to 1 × 10² at the sample volume of 1 dm³, the degree of barium extraction at the concentration 0.05–0.2 mg/dm² constitutes from 90 to 100%.     

The treatment and reuse of wastewater in the textile industry by means of ozonation and electroflocculation

Two different oxidation treatments, ozonation and electroflocculation, were experimented on a pilot scale to test their efficiency in removing polluting substances from wastewaters of textile industries. Both pilot plants used reproduced very closely a full-scale treatment in order to obtain indications about the feasibility of a transfer on industrial scale. By means of ozone treatment very high colour removal (95-99%) was achieved and treated waters were reused satisfactorily in dyeing even with light colours. This evidence despite the fact that the chemical oxygen demand of treated waters was still in a range (75-120 mg/l, a decrease up to 60%) that was usually considered to be too high for recycling purposes, especially for dyeing light colours. Treating plants working at the above-mentioned conditions should guarantee low operating costs. A biological pre-treatment and a sand filtration are absolutely essential. The transfer on industrial scale of the treatment is currently under development under an already financed European project. Electrochemical treatment showed to be very efficient in removing colour (80-100%) and chemical oxygen demand (70-90%). Moreover, a sensible decrease of chloride and sulphate ions was detected. Removal of flocculated material (post-treatment) must be, however, perfected in order to establish a correct costs-to-benefits ratio and therefore, propose an implementation of the technique on an industrial scale.     

Electricity generation from swine wastewater using microbial fuel cells

Microbial fuel cells (MFCs) represent a new method for treating animal wastewaters and simultaneously producing electricity. Preliminary tests using a two-chambered MFC with an aqueous cathode indicated that electricity could be generated from swine wastewater containing 8320 +/- 190 mg/L of soluble chemical oxygen demand (SCOD) (maximum power density of 45 mW/m2). More extensive tests with a single-chambered air cathode MFC produced a maximum power density with the animal wastewater of 261 mW/m2 (200 omega resistor), which was 79% larger than that previously obtained with the same system using domestic wastewater (146 +/- 8 mW/m2) due to the higher concentration of organic matter in the swine wastewater. Power generation as a function of substrate concentration was modeled according to saturation kinetics, with a maximum power density of P(max) = 225 mW/m2 (fixed 1000 omega resistor) and half-saturation concentration of K(s) = 1512 mg/L (total COD). Ammonia was removed from 198 +/- 1 to 34 +/- 1 mg/L (83% removal). In order to try to increase power output and overall treatment efficiency, diluted (1:10) wastewater was sonicated and autoclaved. This pretreated wastewater generated 16% more power after treatment (110 +/- 4 mW/m2) than before treatment (96 +/- 4 mW/m2). SCOD removal was increased from 88% to 92% by stirring diluted wastewater, although power output slightly decreased. These results demonstrate that animal wastewaters such as this swine wastewater can be used for power generation in MFCs while at the same time achieving wastewater treatment.     

绿化用有机基质中总汞和总砷测定方法的研究

建立了一种联用王水水浴消解和原子荧光分光光度计(AFS)测定绿化用有机基质中总汞和总砷的测定方法。对比了传统消解和王水水浴消解两种样品前处理方法对有机基质重金属元素的消解效果。结果表明:(1)王水水浴消解法对总砷和总汞的检出限为0.624 mg/kg和0.024 mg/kg;方法对3种有机基质中总汞和总砷测定的相对标准偏差(RSD)为1.68%~3.02%和2.27%~2.42%,加标回收率为90.2%~109.6%,具有较高精密度;(2)王水水浴消解与传统消解测定结果的相对偏差在0.49%~12.3%,满足标准要求;(3)采用标准物质GBW07603、GBW07408、GBW07447和GBW07452对方法的准确度进行评价,测定结果与标准值相符。综上,该方法可快速准确测定绿化用有机基质中总汞和总砷含量。     

Application of the photo-Fenton process to the treatment of wastewaters contaminated with diesel

The application of the photo-Fenton process for the treatment of wastewaters contaminated with diesel oil was investigated. This particular process has been widely studied for the photochemical degradation of highly toxic organic pollutants. Experiments were performed according to a factorial experimental design at two levels and two variables: H(2)O(2) concentration (5-200 mM) and Fe(2+) concentration (0.01-1 mM). Experimental results demonstrated that the photo-Fenton process is technically feasible for the treatment of wastewaters containing diesel oil constituents, with total mineralization. A combination of factorial experimental design and gradient descent techniques was employed to optimize the amount of the Fenton reagents, resulting in Fe(2+) (0.1 mM) and H(2)O(2) (50 mM). These optimized levels did not exceed the limit for disposal of ferrous ions (0.27 mM) proposed at the local environmental legislation.     

Stimulation of microbial sulphate reduction in a constructed wetland: microbiological and geochemical analysis

Microbial sulphate reduction was stimulated successfully in enclosures installed in a constructed wetland. When sucrose (2.4mM) and NH(4)Cl (600 microM) were added to water in the test enclosures, the indigenous microbial community was able to remove over 90% of the sulphate, present as a contaminant from nearby mining activity at a concentration of 384 mg x l(-1) (4mM), over 50 days. Over 90% of the sucrose was also removed. Sulphate was not reduced in control enclosures containing no added sucrose or NH(4)Cl. Fermentation of sucrose by obligate anaerobes including Clostridium sp. and Bacteriodes sp. preceded sulphate reduction in the test enclosures. Sulphate reduction was biphasic, with maximum rates noted between 2-5 and 23-27 days after the addition of the growth substrates. Relatively unbiased 16S rDNA analysis suggested that nitrogen-fixing bacteria were important constituents of the microbial community in the test enclosures at day 23, suggesting that soluble nitrogen was limiting in the amended test enclosures during the experiment.     

Wet peroxide oxidation of chlorophenols

This study evaluates the application of Wet Peroxide Oxidation (WPO) for the treatment of solutions containing 4-chlorophenol (4-CP) and 2,4-dichlorophenol (2,4-DCP). These compounds are of special interest due to their high toxicity and low biodegradability. WPO is included in the Advanced Oxidation Processes, which are technologies based on an initial formation of hydroxyl radicals that further oxidize the organic matter. The influence of some operating conditions such as temperature, dosage of hydrogen peroxide and initial concentration of the chlorophenols was studied in absence of a catalyst. The results of this study prove that 4-CP and 2,4-DCP can be completely removed from wastewaters by means of WPO. Total Organic Carbon (TOC) and 4-CP removals of 72.3% and 100%, respectively, were achieved working at 100 degrees C with 2.5 mL of H(2)O(2) and an initial concentration of 500 ppm of 4-CP after 90 min of reaction. Under the same conditions but with an initial concentration of 500 ppm of 2,4-DCP a TOC removal of 59% and a complete removal of the target compound were achieved.     

Prevention of volatile fatty acids production and limitation of odours from winery wastewaters by denitrification

The effect of the addition of nitrate to winery wastewaters to control the formation of VFA in order to prevent odours during storage and treatment was studied in batch bioreactors at different NO(3)/chemical oxygen demand (COD) ratios and at full scale in natural evaporation ponds (2 x 7000 m(2)) by measuring olfactory intensity. In the absence of nitrate, butyric acid (2304 mgL(-1)), acetic acid (1633 mgL(-1)), propionic acid (1558 mgL(-1)), caproic acid (499 mgL(-1)) and valeric acid (298 mgL(-1)) were produced from reconstituted winery wastewater. For a ratio of NO(3)/COD=0.4 gg(-1), caproic and valeric acids were not formed. The production of butyric and propionic acids was reduced by 93.3% and 72.5%, respectively, at a ratio of NO(3)/COD=0.8, and by 97.4% and 100% at a ratio of NO(3)/COD=1.2 gg(-1). Nitrate delayed and decreased butyric acid formation in relation to the oxidoreduction potential. Studies in ponds showed that the addition of concentrated calcium nitrate (NITCAL) to winery wastewaters (3526 m(3)) in a ratio of NO(3)/COD=0.8 inhibited VFA production, with COD elimination (94%) and total nitrate degradation, and no final nitrite accumulation. On the contrary, in ponds not treated with nitrate, malodorous VFA (from propionic to heptano?c acids) represented up to 60% of the COD. Olfactory intensity measurements in relation to the butanol scale of VFA solutions and the ponds revealed the pervasive role of VFA in the odour of the untreated pond as well as the clear decrease in the intensity and not unpleasant odour of the winery wastewater pond enriched in nitrates. The results obtained at full scale underscored the feasibility and safety of the calcium nitrate treatment as opposed to concentrated nitric acid.     

Trace determination of 1-aminopropanone, a potential marker for wastewater contamination by liquid chromatography and atmospheric pressure chemical ionization-mass spectrometry

1-Aminopropanone (APR) is a volatile aminoketone of human origin that has been identified in raw sewage and surface waters. However, the traditional methodology for the determination of APR is extremely complicated and requires a skilled chemist to achieve consistent results. This investigation presents a novel and simple method for the analysis of APR by direct derivatization in aqueous media. APR is synthesized as its hydrochloride and derivatized using mercaptoethanol and o-phthalaldehyde. The product of reaction is separated on a 15 cm x 4.6 mm Luna C-18 column (1 mL/min, 45:55 acetonitrile: Water) and detected using a single quadrupole mass spectrometer detector operated in atmospheric pressure chemical ionization (APCI) mode. Method detection limits as low as 100 nM were routinely obtained with a precision of 1.7%. Recoveries of APR were always found to be greater then 88% in surface and wastewater samples fortified at three different levels. However, despite the robustness of the method and the fact that APR was consistently detected in urine it was not present in a variety surface or wastewaters analyzed during the course of the study. These results pose a critical question on the use of APR as a tracer for human derived wastewaters.     

Determination of organochlorine pesticides and their derivations in water after HS-SPME using polymethylphenylvinylsiloxane-coated fiber by GC-ECD

A porous sol-gel polymethylphenylvinylsiloxane-coated fiber was applied to optimize the headspace solid-phase microextraction (HS-SPME) conditions for the analysis of 11 organochlorine pesticides (OCPs) and their derivations in water. Their determination was carried out using gas chromatography (GC) with electron capture detector (ECD). The method developed was applied to the analysis of lake water samples. Detection limits varied from 0.835 to 13.0 ng/l and relative standard deviations (RSD相似文献   

Cucurbituril for water treatment. Part I: Solubility of cucurbituril and sorption of reactive dyes

Cucurbituril was investigated regarding its potential as a sorbent for the removal of reactive dyes from model solutions and authentic wastewaters. The solubility of cucurbituril is low in pure water but increases in the presence of salts. When dyes sorbing onto cucurbituril are present, solubility is drastically decreased compared to dye-free media. Sorption efficiency depends on salt concentration and salt species. Moderate salt concentrations favor sorption, high concentrations lead to cucurbituril dissolution. Divalent ions have a stronger effect than monovalent ions and larger ions more than smaller ones. In tests with authentic wastewaters cucurbituril was partially (20-100%) dissolved and contaminant removal was inefficient. Because of its solubility, cucurbituril is not feasible as a sorbent in wastewater treatment unless it could be covalently fixed onto a suitable support material.     

Potential of freezing in wastewater treatment: soluble pollutant applications

When wastewater containing only soluble pollutants is frozen gradually, ice crystals grow from the pure water only, while pollutants are rejected into the liquid phase thus increasing their concentration. In this way, pure water can be removed from various wastewaters. Two kinds of wastewater were studied: synthetic wastewater containing water and one or more soluble pollutants, and industrial wastewaters (urban wastewater and cutting oil wastewater). In most cases, separation efficiency close to 100% was achieved. A large range of pollutant concentrations was studied in order to determine the limits of freezing separation.     

Purification of chromium(VI) finishing wastewaters using calcined and uncalcined Mg-Al-CO3-hydrotalcite

The applicability of calcined and uncalcined hydrotalcite for the purification of industrial effluents has been studied using chromium finishing wastewaters. Using a batch method, the influence of the initial concentration of chromium (10-450mg/l), hydrotalcite (HT) dose (0.5-5g/l) and time (0.5-72h) has been evaluated. The process could be described by the Langmuir model and gave a maximum removal of chromium of 16.3mg Cr(VI)/g on uncalcined HT and 128mg Cr(VI)/g on calcined hydrotalcite (C-HT). Removal using the calcined product provided an effective system to treat chromium finishing wastewaters with the most stringent discharge limit for such industrial streams being achieved with between two and four consecutive removal cycles on C-HT at a dose of 2g/l.     

Distribution of rare earth elements in anionic,cationic and particulate fractions in boreal humus-rich streams affected by acid sulphate soils

The abundance, fractionation and physicochemical forms of rare earth elements (REEs) were determined in five boreal humus-rich streams (dissolved organic carbon, DOC = 14-40 mg/l) affected by acid sulphate soils. The sampling was carried out during high-water flow in autumn when the acid sulphate soils are extensively flushed. The analytical procedures included ion-exchange experiments in field and ICP-MS determination. There was a general decrease in pH (range 4.5-6.2) and increase in the REE concentrations (La range 0.82-23 microg/l) as the proportion of the catchment cover of acid sulphate soils increased, explained by high amounts of REEs in the acidic runoff from such soils. In each stream, four different REE fractions were identified: (1) A cationic fraction, which is dominant in the REE-rich runoff from the acid sulphate soils and which is depleted in HREEs due to hydrochemical and/or geochemical processes, (2) an anionic fraction identified as humus-REE complexes, which in general is more abundant the higher the DOC concentrations and which also becomes increasingly abundant across the lanthanide series, (3) a fraction having a well-developed MREE enrichment, presumably consisting of colloidal REEs, and (4) a minor uncharacterised particle-associated fraction. The REE pool in the streams thus consists of several coexisting and contrasting REE species. The identification and quantification of such species is a prerequisite for the precise and accurate characterisation of the REE hydrochemistry of the streams.     

Analysis of the antioxidant butylated hydroxytoluene (BHT) in water by means of solid phase extraction combined with GC/MS

The antioxidant 3,5-di-tert-butyl-4-hydroxy-toluene (BHT) is widely used as an additive to increase the tenability of food and plastics. BHT is degraded to 3,5-di-tert-butyl-4-hydroxybenzaldehyde (BHT-CHO) in mammals, as well as in the natural environment such as in water and soils. BHT-CHO has been studied extensively in terms of their potential toxicities. The present investigation was carried out to quantify BHT and BHT-CHO in river, ground, rain and drinking water obtained from several locations in Germany. Apart from the compounds mentioned above, 1,2-bis-(3,5-di-tert-butyl-4-hydroxyphenyl)ethane (2-BHT), which is a dimer of BHT, was also detected in the extracts of some ground water samples. The applied analytical method is based on solid phase extraction (SPE) to concentrate trace compounds from water samples followed by gas chromatography/mass spectrometry (GC/MS) of the extracts. A total of 51 of the respective water samples were used for extraction purposes and analyte recoveries were all > or = 80%. The determination limit for BHT was 5 ng l(-1) and for BHT-CHO 16 ng l(-1). The standard deviations for the analytical procedure were 6% for BHT and 10% for BHT-CHO. The use of the antioxidant BHT in Germany has resulted in water concentrations of 7-791 ng l(-1) in the rivers Rhine, Elbe, Main, Oder, Nidda and Schwarzbach. The degradation product BHT-CHO was also detected in the river water samples at concentrations between 29 and 223 ng l(-1). The concentrations of BHT measured in German rivers are lower compared to values measured in the USA and Japan 20 years ago. In ground water, levels for BHT varied from non-detectable up to 2156 ng l(-1) and for BHT-CHO from non-detectable up to 674 ng l(-1). Both compounds were also detected in rain water in Frankfurt/Main at a concentration of 1797 ng l(-1) for BHT and 59 ng l(-1) for BHT-CHO.