Irradiation conditions required in combined radiation-microbial process for landfill leachate

A landfill leachate, which contains large amounts of microbially refractory humic substances, was irradiated with 60Co gamma-rays under several conditions and the modification of its biodegradability was examined. The effects of initial pH and dose rate on the modification were found to be insignificant. The apparent effect was observed for the initial concentration of the humic substances. High biochemical oxygen demand (BOD) value was obtained as the initial concentration was higher. As the initial concentration was lower, in contrast, the decreasing rates of total organic carbon (TOC) and chemical oxygen demand (COD) were high. Therefore two possible designs of the combined radiation-microbial processes with and without dilution are proposed. Both processes require only about 30% of the irradiation dose, compared with a simple radiation process.     

Radiolysis and ozonolysis of a landfill leachate

A landfill leachate sample was radiolyzed with ??-rays at 12.5, 25, 50, 100, 200 and 400?kGy. The radiolyzed solutions were studied by UV?CVIS?CNIR spectroscopy to measure the color change, by chemical oxygen demand (COD) analysis to check the degree of mineralization of the soluble organic matter present in the leachate and by FT?CIR spectroscopy of the humic substance of the leachate. The results have shown that the humic substance present in the landfill leachate is extremely refractory to radiolysis: even at 400?kGy it was detected and recovered only with minor changes. It is shown that the radiolysis followed by ozonolysis is able to cause important improvements of the leachate color and important reduction on the COD. However, the results in terms of bleaching and COD abatement after radiolysis and ozonolysis of the leachate can be achieved directly by a simple exhaustive ozonolysis of the leachate. The structural changes occurring in the humic substances and in the humic acids present in the leachate after radiolysis and ozonolysis were analyzed by FT?CIR spectroscopy.     

Municipal Solid Waste Landfill Leachate Treatment and Electricity Production Using Microbial Fuel Cells

Microbial fuel cells were designed and operated to treat landfill leachate while simultaneously producing electricity. Two designs were tested in batch cycles using landfill leachate as a substrate without inoculation (908 to 3,200 mg/L chemical oxygen demand (COD)): Circle (934 mL) and large-scale microbial fuel cells (MFC) (18.3 L). A total of seven cycles were completed for the Circle MFC and two cycles for the larger-scale MFC. Maximum power densities of 24 to 31 mW/m² (653 to 824 mW/m³) were achieved using the Circle MFC, and a maximum voltage of 635 mV was produced using the larger-scale MFC. In the Circle MFC, COD, biological oxygen demand (BOD), total organic carbon (TOC), and ammonia were removed at an average of 16%, 62%, 23%, and 20%, respectively. The larger-scale MFC achieved an average of 74% BOD removal, 27% TOC removal, and 25% ammonia reduction while operating over 52 days. Analysis of the microbial characteristics of the leachate indicates that there might be both supportive and inhibiting bacteria in landfill leachate for operation of an MFC. Issues related to scale-up and heterogeneity of a mixed substrate remain.     

Landfill leachate treatment using the sequencing batch biofilm reactor method integrated with the electro-Fenton process

A study was conducted on the treatment of landfill leachate by combining the sequencing batch biofilm reactor (SBBR) method with the electro-Fenton method. The reduction of chemical oxygen demand (COD), biological oxygen demand (BOD₅), and ammonia nitrogen (NH ₄ ⁺ -N) from the leachate by the SBBR method was investigated. For the electro-Fenton experiment, the changes in COD and total organic carbon (TOC) with the increase in H₂O₂ dosage and electrolysis time under optimal conditions were also analysed. The results showed that the average efficiencies of reduction of COD, BOD₅, and NH ₄ ⁺ -N achieved using the SBBR method were 21.6 %, 54.7 %, and 56.1 %, respectively. The bio-effluent was degraded by the subsequent electro-Fenton process, which was rapid over the first 30 min then subsequently slowed. After 60 min of the electro-Fenton treatment, the efficiencies of reduction of TOC, COD, and BOD₅ were 40.5 %, 71.6 %, and 61.0 %, respectively. There is a good correlation between the absorbance of leachate at 254 nm (UV₂₅₄) and COD or TOC during the electro-Fenton treatment.     

Application of Catalytic Wet Air Oxidation to Treatment of Landfill Leachate on Co／Bi Catalyst

Catalytic wet air oxidation(CWAO) was employed to reduce the organic compounds in landfill leachate and the effects of temperature, oxygen pressure, catalyst dosage, and concentration of the organic compounds on the TOC and CODcr removal rates were studied. The degradation kinetics of landfill leachate was also investigated and an exponential experiential model consisting of four influential factors was established to describe the reduction of the organic compounds in the landfill leachate. Meanwhile, the GC-MS technique was used to detect the components of the organic intermediates for the inference of the decomposition mechanisms of the organic compounds in landfill leachate. The results reveal that the reaction temperature and the catalyst dosage are the most important factors affecting the degradation reaction of the organic compounds and that the principal intermediates confirmed by GC-MS are organic acids at a percentage of more than 88% with no aldehydes or alcohols detected. The decomposition mechanisms of the organic compounds in landfill leachate were inferred based on the GC-MS information as follows;the activated gas phase O2 captured the hydrogen of the organic pollutants to produce free radicals, which then initiated the catalytic reaction. So most of the organic compounds were oxidized into CO2 and H2O ultimately. In general, catalytic wet air oxidation over catalyst Co3O4/Bi2O3 was a very promising technique for the treatment of landfill leachate.     

Simulation of aerobic landfill in laboratory scale lysimeters — effect of aeration rate

Aeration of municipal landfills contributes to the acceleration of organic matter degradation and to the decrease of pollutant emission into air, water, and soil. Biodegradation of organic matter present in municipal waste, deposited in a landfill, by microorganisms under anaerobic conditions is a slow process. The aim of the study was to carry out simulations of an aerobic landfill in lysimeters, to determine the influence of aeration rate on the degradation of organic matter present in landfills, and to formulate a mathematical model defining the changes of carbon content in leachate and in gas produced. In this work, simulation of aerobic landfill leachate degradation was carried out in laboratory scale lysimeters with the working volume of 15 L. The changes of BOD5, COD, and ammonium nitrogen concentration during aeration were similar for all aeration rates. During aeration, the BOD5 index decreased by 99.9 %, COD decreased by 95.1 %, and ammonium nitrogen concentration by 93 %. The proposed kinetic model defines the processes of organic carbon content changes in simulated leachate and the quantity of carbon dioxide for aerobic landfill simulation quite well.     

Photocatalytic degradation of 1,5-naphthalenedisulfonate on colloidal titanium dioxide

Photocatalytic degradation of 1,5-naphthalenedisulfonate (NDS) was investigated by monitoring the absorption and emission spectral changes, chemical oxygen demand, total organic carbon (TOC) content as well as pH and sulfate concentration. Intermediates formed during the irradiation were also detected by liquid chromatographic-mass spectrometric analysis. The results obtained by the applied analytical techniques clearly indicate that the initial step of degradation is oxygenation (hydroxylation) of the starting surfactant resulting in the formation of an 8-hydroxy derivative, although desulfonation and some mineralization, that is, decrease of TOC indicating carbon dioxide generation, also take place at this stage. Further oxygenation and desulfonation lead to the destruction of the diaromatic naphthalene system, then to ring fission, producing diols, aldehydes, and carboxylic acids on the side-chains. A tentative scheme involving possible pathways of degradation is proposed, taking the intermediates detected by mass spectrometry into consideration. On the basis of the results of quantum chemical calculations, the most possible points of attack by HO radical were identified, supplementing the MS results, and elucidating the initial oxidation step in the degradation of NDS and the benzenesulfonate (BS) intermediate. Thus, in the case of NDS para position is favored for hydroxylation, while for BS, formation of the ortho-hydroxy derivative is preferred.     

Gamma ray decomposition of dissolved organic substances in river water without compositional change of metallic elements

A river water sample was irradiated with 60Co gamma-rays under aerobic conditions, and the changes of the organic substances in the sample were examined by the analyses of the dissolved organic carbon (DOC), organic composition, UV spectrum and molecular-weight distribution. By the irradiation, the DOC decreased with irradiation dose following the first-order kinetics. In addition, the changes of UV absorption and molecular-weight distribution showed that the considerable decomposition of polymeric aromatic structure, which is the characteristic of humic substances, took place by irradiation of relatively low dose. Since the gamma-ray decomposition does not require any oxidizing agents and pH control, it will cause no compositional change of metallic elements in the water samples and has less chance of contamination. Therefore the method will be useful in, for example, geochemical studies of trace metals in natural waters.     

The effect of gamma radiation on biodegradability of morpholine in aqueous solution

The effect of -radiation on the aqueous solution of morpholine was studied on the basis of UV spectrum measurement, COD /chemical oxygen demand/, TOC /total organic carbon/ and STOD /short-term oxygen demand/ determination and Pitter's kinetic test of biodegradation. The biodegradability of the model solution after irradiation became substantially worse.     

Development and application of an analytical protocol for evaluation of treatment processes for landfill leachates. II. Evaluation of leachate treatment efficiency of different steps in a constructed pilot plant

Different methods for treatment of leachate from a municipal solid waste (MSW) landfill were tested in a pilot plant. Raw leachate was pre-treated with aeration and sedimentation, followed by several parallel individual steps such as bioremediation, chemical oxidation, ozonation, and geo-bed filters. The efficiency of different treatment steps was evaluated according to one previously developed protocol, which includes measurements of several parameters such as conductivity, pH, nutrients, chloride, metals, organic compounds, and acute toxicity before and after a treatment step. The treatment steps which showed the highest efficiency towards organic pollutants in leachate were ozone treatment and chemical oxidation. The use of an adsorption filter, a geo-bed with a mixture of peat and bottom ash with ca 10% remaining carbon, also had good effects. A combination of pre-treatment and a geo-bed filter with peat and carbon ash gave the best overall treatment results when water-quality parameters such as total organic carbon and ammonia-nitrogen were also considered.     

Determinations of humic substances and other dissolved organic matter and their effects on the increase of COD in Lake Biwa.

Humic substances and other dissolved organic matter (DOM) in Lake Biwa and the surrounding rivers were investigated to elucidate their origins and behavior. An annual increase in chemical oxygen demand (COD) has been observed in the northern basin of Lake Biwa since 1985. The concentrations of dissolved organic carbon (DOC) in the northern and southern basins of Lake Biwa were 1.7-2.4 mgC/l and 1.9-2.6 mgC/l, respectively. The DOC concentrations tended to be high in summer and low in winter, and the seasonal changes in the concentrations of humic substances were small. The humic substances content of DOM was considered to be comparatively small because the ratio of the concentration of humic substances to DOC was in the range of 0.14-0.32. From the results of the fractionation of DOM in lake waters, it was estimated that hydrophobic acids, such as humic substances and hydrophilic acids, were about 25% and 45%, respectively. The main origin of hydrophobic acids in Lake Biwa may be humic substances from soils around the rivers that flow into Lake Biwa, while hydrophilic acids may be due to the inner production by phytoplankton. Therefore, the increase of COD in the northern basin of Lake Biwa may be attributed to the contributions of not only humic substances but also hydrophilic acids.     

Degradation of organic pollutants by visible light synergistic electro-Fenton oxidation process

Visible light irradiation combined with homogeneous iron and/or hydrogen peroxide to degrade organic dye rhodamine B (RhB) and small molecular compound 2,4-dichlorophenol (2,4-DCP) in a home-made bottle reactor was assessed. The concen-tration of oxidize species, Fe3+ and Fe2+ were determined during the degradation process. The results demonstrated that visible light irradiation combined with electro-Fenton improved the degradation efficiency. Moreover, both RhB and 2,4-DCP were mineralized during visible light synergistic electro-Fenton oxidation process. 95.0% TOC (total organic carbon) removal rate of RhB occurred after 90 min and 96.7% of COD (chemical oxygen demand) removal rate after 65 min of irradiation. 91.3% TOC removal rate of 2,4-DCP occurred after 16 h of irradiation and 99.9% COD removal rate occurred after 12 h of illumination. The degradation and oxidation process was dominated by the hydroxyl radical ( · OH) generated in the system. Both the impressed electricity and dye sensitization by visible light facilitated the conversion between Fe3+ and Fe 2+ , thus, improving Fenton reaction efficiency.     

Study on gamma-ray-induced degradation of polymer electrolyte by pH titration and solution analysis

Degradation process of polymer electrolyte was investigated by pH titration and solution analysis. Perfluorosulfonic acid, which is generally used for fuel cells and sensors, was irradiated with gamma-ray. Irradiated samples were immersed in distilled water, and the suspensions were titrated with NaCl solution while pH was monitored. Initial pH without any sodium ion decreased as increase in absorbed dose, indicating acid release from polymer electrolyte. To identify the chemical structure of dissolved species, solution analysis was performed by ion chromatography, total organic carbon (TOC) analyzer, and inductively-coupled plasma atomic emission spectrometry (ICP-AES). It was shown that proton, sulfide ion, fluorine ion and organic carbon were detected in the solution, and the ratio among these ions and atoms changed depending on the irradiation conditions. It shows that the solution analysis can identify the scission site by irradiation sensitively, and gives useful information for investigation of polymer degradation process.     

Two-stage irradiation study on propagation and termination in the γ-radiation-induced polymerization of ethylene in liquid carbon dioxide

The propagation and termination reaction in the γ-radiation-induced ethylene polymerization in liquid carbon dioxide were investigated by a two-stage irradiation. After irradiation at high dose rate, the polymerization occured at a considerable rate under the extremely low dose rate without initiation. The absolute propagation rate was determined in the second stage to be proportional to the square of ethylene fugacity and depended slightly on dose rate. The apparent activation energy for the propagation reaction is ?9 kcal./mole. From these observations which are the same as those in bulk polymerization, it is concluded that carbon dioxide acts as a diluent of ethylene monomer in the propagation reaction. Also, carbon dioxide was shown to be inactive to the growing radicals without irradiation, but oxygen which is produced by the radiolysis of carbon dioxide at high dose terminates the growing radicals with formation of carbonyl in the polymer.     

A calculation method to estimate the concentration and elemental composition of organic substances in natural Waters

The possibility of calculating the elemental composition and concentrations of organic substances in natural water based on the results of determining organic carbon and nitrogen and chemical oxygen demand is substantiated both theoretically and experimentally. Three types of substances differing in the electrochemical valence of carbon were among organic substances. The elemental composition of a number of water objects was analyzed. It was found that the concentrations of organic carbon, oxygen, hydrogen, and nitrogen are close to 50, 40, 4–5, and 2–5%, respectively.     

A pilot plant study on reclamation of sewage effluent by radiation treatment

A pilot plant was developed for the reclamation and reuse of secondary effluent from a sewage treatment plant. The plant system consists of sand filtration, gamma-irradiation, ozonation and ion-exchange. Gamma-irradiation showed effective organic contaminant decomposition and this resulted in the reduction of 5-day biochemical oxygen demand (BOD₅), color, chemical oxygen demand (COD_Cr) and total organic carbon (TOC). Ion-exchange significantly removed inorganic ions, and thus reduced total nitrogen (TN) and total phosphorus (TP). The average reduction in color, COD_Cr, BOD₅, TOC, TN and TP, which was obtained after 12 operations, was 64, 52, 67, 61, 95 and 92%, respectively. Irrespective of applied radiation dose, the treated water fully satisfied the quality requirements of household water that can be used for all home uses except for drinking and human contact uses. This revised version was published online in August 2006 with corrections to the Cover Date.     

Determination of Organic Compounds,Fulvic Acid,Humic Acid,and Humin in Peat and Sapropel Alkaline Extracts

Black, brown, and light peat and sapropel were analyzed as natural sources of organic and humic substances. These specific substances are applicable in industry, agriculture, the environment, and biomedicine with well-known and novel approaches. Analysis of the organic compounds fulvic acid, humic acid, and humin in different peat and sapropel extracts from Lithuania was performed in this study. The dominant organic compound was bis(tert-butyldimethylsilyl) carbonate, which varied from 6.90% to 25.68% in peat extracts. The highest mass fraction of malonic acid amide was in the sapropel extract; it varied from 12.44% to 26.84%. Significant amounts of acetohydroxamic, lactic, and glycolic acid derivatives were identified in peat and sapropel extracts. Comparing the two extraction methods, it was concluded that active maceration was more efficient than ultrasound extraction in yielding higher amounts of organic compounds. The highest amounts of fulvic acid (1%) and humic acid and humin (15.3%) were determined in pure brown peat samples. This research on humic substances is useful to characterize the peat of different origins, to develop possible aspects of standardization, and to describe potential of the chemical constituents.     

Identification of diffuse and point sources of dissolved organic carbon (DOC) in a small stream (Alb, Southwest Germany), using gel filtration chromatography with high-sensitivity DOC-detection

Using gel filtration chromatography and high-sensitivity UV and organic carbon (OC) detection, the quality and quantity of organic matter in a stream (the Alb, Southern Germany) has been studied in the winter season. In the catchment area and upstream of two sewage plant effluents the organic load has been low (below 1 mg/l TOC) and has been dominated by humic substances (more than 80%). Downstream of the sewage plants, TOC increased up to 5 mg/l while humic constituents decreased down to 30%. A detailed analysis showed that in the catchment area the humic fraction has been composed of fulvic acids with relatively high amounts of aliphatic structures. Downstream of the sewage plants, the humic fraction has been composed of fulvic acid precursors with associated non-humic matter. It is concluded that the quality and quantity of organic constituents in the stream has been dominated by the secondary effluents.Dedicated to Professor Dr. Dieter Klockow on the occasion of his 60th birthday     

Chemiluminescence method with potassium permanganate for the determination of organic pollutants in seawater.

A chemiluminescence method with potassium permanganate was developed for use as an indicator of organic pollutants in fresh water. This method could be applied to the determination of organic pollutants in seawater as well. However, the flow chemiluminescence method suffered from the interference of chloride ions at the same concentration of seawater because of the production of manganese dioxide in the oxidation of chloride ions with permanganate. The conditions (concentrations of potassium permanganate and sulfuric acid and sample volume, i.e. flow injection method) were chosen to minimize the interference of chloride ions. The chemiluminescence method shows a good correlation with the chemical oxygen demand method on fresh water added artificial sea salt and seawater samples. Natural seawater was analyzed by the chemiluminescence method. The results obtained were compared with those obtained by chemical oxygen demand under the alkaline condition and total organic carbon methods. The chemiluminescence method has higher sensitivity and reproducibility than the conventional chemical oxygen demand and total organic carbon methods.     

Efficient photoinduced conversion of an azo dye on hexachloroplatinate(IV)-modified TiO2 surfaces under visible light irradiation-A photosensitization pathway

The titanium dioxide photocatalyst is employed to examine the influence of chemisorbed hexachloroplatinate(IV) anions (PtCl(6) (2-)) on the surface of P-25 TiO(2) particles on the photoinduced conversion of the azo dye Ethyl Orange (EO) in visible light-illuminated Pt(IV)/TiO(2) dispersions. Spin-trap electron spin resonance (ESR) spectral results, measurement of quantities of organoperoxides formed, total organic carbon (TOC) and chemical oxygen demand (COD(Cr)) assays, together with XPS evidence show that the self-sensitized transformation dynamics of the EO dye mediated by Pt(IV)/TiO(2) are much faster than those occurring on naked TiO(2) under otherwise identical conditions of visible light irradiation. X-ray photoelectron spectral data also show that under the experimental conditions used, no Pt(0) formed on the titania particles during visible light irradiation. We propose a reaction mechanism in which the more rapid conversion of EO in the presence of PtCl(6) (2-) is caused principally by photoexcitation of the dye and not by localized excitation of the tetrachloroplatinate(IV)/TiO(2) particles.