Simple UV/UV-visible method for nitrogen and phosphorus measurement in wastewater

A simple UV/UV-visible method is described for the determination of global nitrogen and total phosphorus in wastewater. This method includes two steps: first, the photo-oxidation of nitrogen and phosphorus forms into nitrate and orthophosphate ions, and their quantification by UV-visible spectrophotometry. Potassium peroxodisulfate is used as oxidant. The developed system consists of on-line association of UV photo-oxidation reactor with UV-visible detector. The conversion yields vary between 80 and 100% for both nitrogen compounds (ammonium, urea, amino acids, and other N-containing compounds), and phosphorus compounds (ADP, ATP, and other P-containing compounds). The time requires for nitrogen and phosphorus forms determination is no longer than 20 min.     

Uncertainty of the result of TOC determination in water samples

It is becoming increasingly important to have a reliable and rapid technique for determining total organic carbon (TOC) in wastewater as procedures for wastewater purification could be better applied by knowing the amount of TOC in the wastewater. We describe here an evaluation of the uncertainties associated with TOC determinations in wastewater. TOC was determined by combustion and an infrared (IR) detection method, as described in the standard procedures of the International Organization for Standardization (1999; no. 8245). The major sources of uncertainty in the measurements were identified as being contributions from the linear least square calibration, repeatability, recovery and stability of the sample (storage conditions). A 10% relative expanded uncertainty of TOC measurement in the range of 0.2 to 500 mg L⁻¹ TOC was calculated, which also includes the uncertainty due to sampling.     

Rapid estimation of TOC in a marine urban sewage area by UV spectral deconvolution

A simple and rapid procedure for on-site qualitative and quantitative analysis of organic matter from discharges of municipal wastewater in seawater has been developed. This method is based on the knowledge of the UV signal of both seawater and anthropogenic absorbing matter and on the mathematical deconvolution of the sample spectrum using reference spectra. The main application is the estimation of TOC at the direct outlet of the discharge. This quantitative application is obviously limited by the nature of organic compounds, but the UV estimation allowed us to have an overview of the composition and evolution of organic matter into the polluted area. The application of this procedure has been carried out to study the wastewater dilution into an area receiving urban discharges. Experiments showed satisfactory analytical features with a range of TOC values from 75 to 1500?µM C, and the comparison of the results with those obtained by reference method presented a reasonable correlation (r ²?=?0.9636) in the marine discharge. The results have also allowed us to quickly estimate the plume evolution at the sea surface and in depth. This alternative method could be integrated in a portable device for on-site analysis and multiplication of measurements for relevant results, or in a continuous flow analyser.     

Photocatalytic degradation of actual textile industrial wastewater in aqueous suspensions of polycrystalline TiO2

Heterogeneous photocatalytic oxidation of contaminants present in wastewater produced by a textile industry was carried out. The samples were withdrawn from the plant before and after a traditional biological treatment. The effluents were named A and A' (before the biological treatment), B and B' (after the biological treatment). Polycrystalline TiO2 (Degussa P25) was used as the catalyst in a batch photoreactor with immersed lamp. An almost complete decolorization was observed after about 0.5 divided by 1 hours for both kinds of effluents, but the decrease of the total organic carbon (TOC) concentration occurred more slowly. The influence of some chemical oxidants, i.e. ozone, hydrogen peroxide and peroxydisulfate on the photo-oxidation rate was also investigated. After addition of H2O2 or S2O8(2-) TOC decreased more quickly only for B and B'. The runs performed by using O3 as bubbling gas showed a mineralization rate higher than that observed in the presence of O2.     

丙烯酸生产外排废水化学需氧量与总有机碳相关性研究

化学需氧量（COD_Cr）与总有机碳（TOC）指标均可用来表征废水的有机物污染程度.不过,以COD_Cr表征有机物污染程度一般只能反映水中部分有机物的量,而TOC能更全面地反映废水中有机物的含量.以丙烯酸生产外排废水为研究对象,分析结果表明：在一定范围内,废水中COD_Cr与TOC满足关系式y=1.147 4x+74.75（R²=0.955 26）,回收率范围98%~115%,TOC测定结果的精密度高、可靠、准确,在一定条件下,可使用TOC来间接换算COD_Cr.     

185 nm UV降解水中4-CP、4-NP和Rh B的研究

本文以对氯苯酚(4-CP)、对硝基苯酚(4-NP)和罗丹明B(Rh B)为模型有机物(以4-CP和4-NP为小分子模型有机物,以Rh B为大分子模型有机物),分别研究了185 nm UV对水中这3种模型有机物的降解规律、性能和效果.研究结果表明,185 nm UV直接对水中4-CP、4-NP和Rh B有很好的降解效果.研究内容包括:185 nm UV降解模型有机物的浓度、TOC(Total organic carbon)浓度、185 nm UV降解模型有机物过程中溶液pH及电导率变化、以及降解模型有机物过程中产生的无机离子等几个方面.     

Spectroscopic study of dissolved organic sulfur (DOS): a case study of mercaptans

Sulfur compounds are often present in petrochemical wastewater and can be detected by UV spectrophotometry. This technique allows to point out specific absorptions of mineral sulfide and mercaptans and can be used for the determination of acidity constants. From a quantitative point of view, using a spectral deconvolution method, a specific determination of some mercaptans is obtained. Detection limits for ethanethiol and thiophenol are 0.7 and 2.5 mg l(-1), respectively.     

Fe(0)/Cu双金属还原与Fenton氧化集成工艺处理印染生化尾水树脂脱附液的研究

通过比较Fe(0)和Fe(0)/Cu还原工艺处理印染生化尾水树脂脱附液的效果,发现Fe(0)/Cu双金属还原对脱附液TOC和UV254去除率均优于Fe(0)。若将Fe(0)/Cu双金属还原与Fenton氧化工艺集成可以进一步提高处理效果。该组合工艺处理后,TOC去除率高达66%,UV254去除率高于90%,脱附液的BOD5/CODcr从低于0.1升高至0.38左右。由此可见,该组合工艺对复合功能树脂碱脱附液具有良好的处理效果,处理后废水的毒性降低,可生化性显著提高,为其返回生物系统进一步生化降解提供了较好的保证。     

Photocatalytic activity of sea water using TiO₂ catalyst under solar light

Wastewater is generally released into the rivers and streams in developing countries. Industrial wastewater usually contains highly toxic pollutants, cyanides, chlorinated compounds. Ultraviolet (UV) radiation from sunlight also decomposes organic compounds by oxidation process. However, the process is less effective due to large amount of toxic effluent entering in the main stream of water. The solar radiation can effectively be applied to accelerate the process by using suitable catalyst for economically cleaning the water sources. This paper describes the photocatalytic degradation of the sea water using novel approach of photoelectrochemical (PEC) reactor module consisting of nine photoelectrochemical cells equipped with spray deposited TiO? catalysts under solar light. The resulted water samples were studied for physicochemical and bacteriological analysis. The complete mineralization of degraded sample was confirmed by total organic carbon (TOC) analysis, COD measurement and estimation of the formation of inorganic ions such as NH?(+), NO??, Cl? and SO2??. Microbiological examinations are performed to determine the bacterial analysis. This implies that photoelectrocatalysis could be a promising way for improving water quality in developing countries with low cost and clean energy reliable resource.     

Sequential injection system for on-line analysis of total nitrogen with UV-mineralization

An automatic method for the determination of total nitrogen in wastewater by sequential injection analysis and mineralization with UV radiation has been developed. The method is based on the mineralization of the samples with sodium persulphate in basic medium under UV radiation. Small volumes of sample and reagents are firstly aspirated into a single channel and then propelled by flow reversal to the UV reactor and then to the detector. The organic and inorganic nitrogen compounds are oxidized to nitrate that is then measured at 226 nm. The sequential injection procedure has been optimized and the factors affecting the efficiency of the oxidation have been studied with a number of test substances with different chemical structures and properties. Solutions in the concentration range 1-56 g l⁻¹ of nitrogen can be analyzed with the described procedure. The sample rate is of 30-40 samples h⁻¹. The LOD is 0.6 mg l⁻¹ N and the reproducibility is 1.8% (28 mg l⁻¹ N). Organic carbon in the form of glucose was added to a number of test solutions to study the potential interference of organic matter.The method was compared with the Kjeldahl digestion method by analyzing 15 wastewater samples with both methods. The nitrate and nitrite content of the non-oxidized samples were subtracted from the corresponding nitrogen content determined after photo-oxidation and the value compared with the Kjeldahl nitrogen content.     

Photochemical behavior of inorganic and organic selenium compounds in various aqueous solutions

Selenium possesses interesting chemical, biochemical and geochemical behaviors. However, studies of its photochemical properties in aqueous systems are scarce. A better understanding of these phenomena is of great importance for further application of such properties to selenium speciation. In this work, the photochemical behavior of selenium and some of its organic compounds have been systematically studied in various aqueous matrices under UV irradiation at 300 nm. It was observed that the photochemical oxidation rate of Se(IV) to Se(VI) was greatly enhanced in the presence of HN0₃ at ≥1 × 10⁻³ M, but not by NaNO₃. However this photo-oxidation could be inhibited by the presence of Cl⁻. Under UV irradiation, organoselenium compounds went through two successive photochemical reactions in pure water: a direct photolysis (photo-cleavage) followed by a photo-oxidation to form Se(VI). These two steps could also be greatly accelerated in presence of NO₃⁻ although the second step required an acidic condition. The photo cleavage rates varied from one organic compound to another and 10-fold differences were observed. Similarly to Se(IV), the further oxidation to Se(VI) could be prevented by Cl⁻ for all studied organoselenium compounds. Detailed reaction mechanisms involving OH radicals are proposed to explain Se photochemical behaviors in different matrices.     

Polydisperse adsorbability composition of several natural and synthetic organic matrices

The polydisperse composition of nine dissolved organic materials (DOMs) from two river water sources, one ground water source, two biologically treated wastewater sources, and two commercial sources was analyzed based on their adsorbabilities by activated carbon. For each DOM, batch adsorption isotherms measured for both TOC and UV260 were analyzed using an overall isotherm model derived from the IAST-Freundlich expression. By accounting for the heterogeneity of each DOM with a log-normal distribution of the Freundlich parameter (K), its adsorption behavior was characterized with only four parameters (including three fitting ones). The average adsorptive strength (KM) and heterogeneity (sigma) determined for all DOMs, which were defined by the mean value and the standard deviation of the log-normal distribution of the Freundlich K, changed over the ranges 2.5-62.2 and 0.22-0.97 (mg/g)/(mg/l)(1/n), respectively, when the TOC index was used. Among all DOMs studied, a river water DOM at the upper stream was found least heterogeneous: the Freundlich K of its organic constituents varied in the range 10.8-190 (mg/g)/(mg/l)(1/n), as compared to a commercial humic acid that exhibited the broadest Freundlich K distribution of 0.01-1494.3 (mg/g)/(mg/l)(1/n). KM and sigma, along with other two parameters (the Freundlich exponent 1/n and the nonadsorbable organic fraction parameter Cnon/CT0), changed with both indices of TOC and UV260 in a regular manner, indicating that UV-absorbing organic molecules possessed adsorbabilities different from non-UV-absorbing ones. Also based on HPSEC chromatograms measured for solutions before adsorption, the molecular weight composition of all DOMs was also assessed and the molecular size impacts on adsorption characteristics of DOMs were briefly discussed.     

Multi-pumping flow system for the determination of dissolved orthophosphate and dissolved organic phosphorus in wastewater samples

A multi-pumping flow system (MPFS) for the spectrophotometric determination of dissolved orthophosphate and dissolved organic phosphorus in wastewater samples is proposed. The determination of orthophosphate is based on the vanadomolybdate method. In-line ultraviolet photo-oxidation is employed to mineralise organic phosphorus to orthophosphate prior to detection. A solenoid valve allows the deviation of the flow towards the UV-lamp to carry out the determination of organic phosphorus.Calibration was found to be linear up to 20 mg P L⁻¹, with a detection limit (3s_b/S) of 0.08 mg P L⁻¹, an injection throughput of 75 injections h⁻¹ and a repeatability (R.S.D.) of 0.6% for the direct determination of orthophosphate. On the other hand, calibration graphs were linear up to 40 mg P L⁻¹, with a detection limit (3s_b/S) of 0.5 mg P L⁻¹, an injection throughput of 11 injections h⁻¹ and a repeatability (R.S.D.) inferior to 2.3% for the procedures involving UV photo-oxidation.     

EFFECTS OF ORGANIC COLORANTS ON PHOTO-INITIATED CROSSLINKING AND PHOTO-OXIDATION DEGRADATION OF POLYETHYLENE AND RELATED MECHANISM

The effects of three organic colorants on photo-initiated crosslinking and photo-oxidation degradation of polyethylene (PE) samples irradiated by microwave excited (MWE) UV lamp in the melt and the related mechanism have been studied by gel content and thermal extension rate determinations,X-ray photoelectron spectroscopy (XPS),mechanical property tests,UV spectroscopy,and light microscope.The data from the gel content and thermal extension rate determinations of photo-crosslinked polyethylene (XLPE) sam...     

An anion-exchange high-performance liquid chromatography method coupled to total organic carbon determination for the analysis of water-soluble organic aerosols

The chemical composition of water-soluble organic carbon (WSOC) in atmospheric aerosol particles is largely unexplored, due to the myriad of individual compounds, which has hampered attempts to attain a full characterization at the molecular level. An alternative approach, focusing on the analysis of a few main chemical classes, allowed the quantitative fractionation of WSOC into neutral compounds (NC), mono- and di-acids (MDA) and polyacids (PA) through an anion-exchange liquid chromatographic method. Previous attempts to quantify NC, MDA and PA relied on a low-pressure chromatographic technique using a volatile buffer, followed by total organic carbon (TOC) analysis of the fractions, or alternatively on a faster HPLC-UV method which provided a quantification of the fractions based on empirical relationships between UV signal and TOC concentration. Here, we report an upgraded anion-exchange HPLC technique, allowing direct TOC analysis of the eluted fractions, without any pre-treatment, thus permitting a great simplification of quantitative analysis and preventing sample losses. The new HPLC-TOC methodology, employing completely inorganic eluents shows the same efficiency of the former HPLC-UV method employing organic additives, with the exception of phenolic compounds, which are retained on the column by secondary interactions, and low-molecular weight tricarboxylic acids, which are recovered among MDA. The new anion-exchange liquid chromatographic method can recover a substantial amount (86-100%) of water-soluble organic carbon from atmospheric aerosol extracts, thus allowing a higher retention and fractionation capacity with respect to alternative techniques, like solid phase extraction.     

Statistical Model for Organic Chromatographic Trace Analysis of Complex Samples. A Case Study: Plant Extracts

Abstract

The use of pooled plant extracts is described in the estimation of matrix interference in HPLC (UV and EC) determinations of organic compounds in plant extracts. An extract from freeze dried leaves of 134 different plant species was used for this purpose. It was split in different subgroups with solid extraction clean-up procedures. UV, EC and chromatographic data of the subgroups were used in the calculation of minimum concentrations of organic compounds which are still accurately determinable in plant samples with HPLC methods. The UV and/or EC characteristics of the compound must be known. The contribution of the solid phase extraction procedures and of the analytical system to the selectivity of the method can be estimated. Information is also supplied which allows rapid comparison of the selectivity of the UV and EC (single, or dual parallel) detectors for the determination of a specified compound.     

Analysis of organics in highly radioactive nuclear wastes

Analytical methods are being developed at Pacific Northwest Laboratory (PNL) for the organic analysis of nuclear wastes. In this study our laboratory analyzed the organic content of two highly radioactive wastes, a neutralized cladding removal waste (NCRW) and a volume reduction, double-shell slurry (DSS) waste. In-house methods were developed and U.S. Environmental Protection Agency (EPA) methods were modified for isolating and analyzing volatile, semivolatile and hydrophilic organics in the hot cell and radiation hood. The procedures worked well, particularly for the NCRW, in which 94.9% of the waste's total organic carbon (TOC) has been characterized. In contrast, only 1.2% of the DSS waste's TOC has been identified to date. Quite a variety of volatile, semivolatile and hydrophilic organics, e.g., chelating agents, were identified in the wastes, occasionally at relatively high mM, or mg/g, concentrations. Most of the compounds are either source-term organics associated with nuclear operations or their degradation products, indicating that organic diagenesis in nuclear wastes can be quite vigorous and extensive.     

QSPR studies on the photoinduced-fluorescence behaviour of pharmaceuticals and pesticides

Fluorimetric analysis is still a growing line of research in the determination of a wide range of organic compounds, including pharmaceuticals and pesticides, which makes necessary the development of new strategies aimed at improving the performance of fluorescence determinations as well as the sensitivity and, especially, the selectivity of the newly developed analytical methods. In this paper are presented applications of a useful and growing tool suitable for fostering and improving research in the analytical field. Experimental screening, molecular connectivity and discriminant analysis are applied to organic compounds to predict their fluorescent behaviour after their photodegradation by UV irradiation in a continuous flow manifold (multicommutation flow assembly). The screening was based on online fluorimetric measurement and comprised pre-selected compounds with different molecular structures (pharmaceuticals and some pesticides with known ‘native’ fluorescent behaviour) to study their changes in fluorescent behaviour after UV irradiation. Theoretical predictions agree with the results from the experimental screening and could be used to develop selective analytical methods, as well as helping to reduce the need for expensive, time-consuming and trial-and-error screening procedures.     

Accurate quantification and transformation of arsenic compounds during wet ashing with nitric acid and microwave assisted heating

Arsenous acid, dimethylarsinic acid (DMA), methylarsonic acid (MA), arsenic acid, arsenobetaine bromide (AB), trimethylarsine oxide (TMAO), arsenocholine iodide (AC), and tetramethylarsonium iodide (TETRA) were heated in a microwave autoclave with nitric acid to 100-300 degrees C. The arsenic compounds in the digests were separated with anion- and cation-exchange chromatography and determined with an inductively coupled plasma mass spectrometer as arsenic-specific detector. Arsenous acid was completely oxidized to arsenic acid at 100 degrees C. For a complete oxidation of MA and DMA to arsenic acid temperatures > 220 degrees C and > 280 degrees C were necessary. AB decomposed to arsenic acid via TMAO. Complete conversion was only obtained after heating the sample for 90 min to 300 degrees C. For a complete conversion of TMAO similar harsh conditions were necessary. AC was already substantially degraded to TMAO, TETRA and two unknown compounds at 100 degrees C. The unknown arsenic compounds were found only in the digests up to 160 degrees C. Quantitative conversion of AC to arsenic acid went also via TMAO. At temperatures above 220 degrees C TETRA started to convert to TMAO, which then was further converted to arsenic acid. To investigate whether the results obtained for the arsenic standards are transferable to real samples, the certified reference material DORM-2 was also heated in nitric acid with variable digestion temperatures and times. For an almost complete conversion of the AB present in DORM-2 90 min at 300 degrees C were necessary. Total organic carbon (TOC) was less < 0.2% when DORM-2 was heated at temperatures > or = 260 degrees C for 60 min. UV photo-oxidation of DORM-2 was investigated as an alternative sample decomposition. Only 6% of AB was converted to arsenic acid when DORM-2 was irradiated for 2 h at 1000 W. In contrast to microwave heating substantial amounts of MA were observed as degradation product.     

Study on the Relationship between the Emission of Chlorine and UV/VIS Sensitive Organic Matter from Heating MSWI Baghouse Ash: Using an Optical UV/VIS Spectrometer as the On‐Line Monitoring Sensor

In this study the baghouse ash (fly ash) from municipal solid waste incineration (MSWI) plants was heated in a fixed bed reactor, from 25 °C to 800 °C. An optical fiber UV/VIS spectrometer was employed as the real‐time monitor to probe the emission behaviors of organic compounds. A two‐dimensional (2D) correlation technique was used to specify organic matter existing in exhausted gas. Three adsorbents, including water, acetone and cyclohexane, were used to adsorb the organic and molecular chlorine in the gas emitted from the reactor. Concentrations of molecular chlorine (Cl₂), total organic carbon (TOC), and total inorganic carbon (TIC) in these adsorbents were analyzed to evaluate the reactions occurring in fly ash. We have found that generation temperatures of molecular chlorine were found mainly at 200 °C and 750 °C, which are attributed to the dechlorination of chlorinated‐organic compounds and vaporization of heavy metal chlorides, respectively. 2D correlation UV/VIS spectra are useful to extract valuable information from the one‐dimensional UV/VIS of emitted gas. The identified organic species would be diethyl‐amine, dibenzo‐p‐dioxin, thioxanthone, 1,4‐dichloro‐anthraquinone, benzene, 1‐naphthalene azo, azulene, dibenzanthrone, 1‐chloro‐4‐notroso‐benzene and 4‐nitro‐toluene. The emission behaviors of dibenzo‐p‐dioxin, thioxanthone, azulene and dibenzanthrone were reported, and we concluded that the chlorine emission is almost always earlier than the release of these UV/VIS‐sensitive organic compounds.