Toxicity of copper to acetoclastic and hydrogenotrophic activities of methanogens and sulfate reducers in anaerobic sludge

Heavy metals could potentially negatively impact microorganisms in anaerobic sulfate reducing bioreactors. The objective of this is study was to evaluate the inhibitory effect of copper to acetoclastic and hydrogenotrophic activities of methanogens and sulfate reducers in sludge obtained from a full-scale sulfate reducing bioreactor. The 50% inhibiting concentration (50%IC) of Cu(2+) to acetoclastic and hydrogenotrophic methanogens was 20.7 and 8.9 mg l(-1), respectively. The 50%IC of Cu(2+) to acetoclastic sulfate reduction was 32.3 mg l(-1). The hydrogenotrophic sulfate reducers were only inhibited by 27% at the highest concentration of Cu(2+) tested, 200 mg l(-1), indicating a high level of tolerance. The soluble Cu(2+) was observed to decrease rapidly in both the methanogenic and sulfate reducing assays. The highest level of decrease was observed in the hydrogenotrophic sulfate reducing assay which was over 99% in 5h. The results of this study indicate that sulfate reducing biotechnologies would be robust at relatively high inlet concentrations of Cu(2+).     

Comparative effectiveness of mixed organic substrates to mushroom compost for treatment of mine drainage in passive bioreactors

Bioreactors are one possible best sustainable technology to address the mine-impacted water problems. Several prospective substrates (mushroom compost, cow manure, sawdust, wood chips, and cut rice straw) were characterized for their ability to serve as a source of food and energy for sulfate-reducing bacteria. Twenty bench-scale batch bioreactors were then designed and set up to investigate relative effectiveness of various mixtures of substrates to that of mushroom compost, the most commonly used substrate in field bioreactors, for treating mine drainage with acidic (pH 3) and moderate pH (pH 6). Overall, reactive mixtures showed satisfactory performances in generating alkalinity, reducing sulfate and removing metals (Al>Fe>Mn) (up to 100%) at both pH conditions, for all substrates. The mixture of sawdust and cow manure was found as the most effective whereas the mixture containing 40% cut rice straw gave limited efficiency, suggesting organic carbon released from this substrate is not readily available for biodegradation under anaerobic conditions. The mushroom compost-based bioreactors released significant amount of sulfate, which may raise a more concern upon the start-up of field-scale bioreactors. The correlation between the extent of sulfate reduction and dissolved organic carbon/SO(4)(2-) ratio was weak and this indicates that the type of dissolved organic carbon plays a more important role in sulfate reduction than the absolute concentration and that the ratio is not sensitive enough to properly describe the relative effectiveness of substrate mixtures.     

氯代有机污染物在厌氧条件下还原脱氯的研究进展

对氯代有机污染物在产甲烷和硫酸盐还原条件下还原脱氯的研究成果进行了综述 ,并介绍了国内外加速厌氧条件下还原脱氯的方法与成果以及缓释氢物质 (hydrogenreleasecompounds ,HRC)的工作原理与工程应用。此外 ,作者还对厌氧还原脱氯的机理和未来的研究方向进行了讨论和展望     

Effects of aeration frequency on leachate quality and waste in simulated hybrid bioreactor landfills

Research has been conducted to investigate the effects of daily aeration frequency on leachate quality and waste settlement in simulated hybrid landfill bioreactors. Four laboratory-scale reactors were constructed and operated for about 10 months to simulate different bioreactor operations, including one anaerobic bioreactor and three hybrid bioreactors with different aeration frequencies (one, two, and four times per day). Chemical oxygen demand (COD) and biochemical oxygen demand (BOD₅) reduced more than 96% of the initial concentrations in all aerated bioreactors. The differences of COD and BOD₅ reductions among tested aeration frequencies were relatively small. For ammonia nitrogen, the higher aeration frequency (two or four times per day) resulted in the quicker reduction. Overall, the concentrations of heavy metals (Cr, Co, Cu, Mn, Ni, and Zn) decreased over time except Cd and Pb. The reduction of redox-sensitive metal concentrations (Mn, Co, Ni, and Cu) was greater in aerated bioreactors than in anaerobic bioreactor. Settlement of municipal solid waste (MSW) was enhanced with higher frequency of aeration events (four times per day).

Implications: In recent years, hybird bioreactor landfill technology has gained a lot of attention. Appropriate aeration rate is crucial for hybrid bioreactor operation, but few studies have been done and different results were obtained. Research was conducted to investigate the effects of daily aeration frequency on leachate quality and waste settlement. Results indicated that aeration can effectively accelerate waste stabilization and remove organic carbon concentration and total nitrogen in the leachate.     

Aerobic inhibition assessment for anaerobic treatment effluent of antibiotic production wastewater

Biological treatment of antibiotic production effluents is an economical approach; however, there are still difficulties to overcome because of the recalcitrant characteristics of these compounds to biodegradation. This study aims to reveal that anaerobic treatment technology can be an option as pretreatment before the activated sludge system treatment to treat antibiotic production effluents. The ISO 8192 method was chosen to test the inhibitory effect of raw and treated antibiotic production effluents in this work. Inhibition tests, which were applied according to ISO 8192, highlighted that the anaerobic treatment effluent is less inhibitory than antibiotic production effluent for activated sludge system. Early EC₅₀ concentrations (30-min values) of raw and treated wastewaters were lower than 180-min values. Also, triple effects (sulfamethoxazole–erythromycin–tetracycline) of antibiotics are more toxic than dual effects (sulfamethoxazole–tetracycline). In light of the experimental results obtained and their evaluation, it can be concluded that anaerobic digestion can be applied as a biological pretreatment method for pharmaceutical industry wastewater including antibiotic mixtures prior to aerobic treatment.     

Sediments as a sink for UV filters and benzotriazoles: the case study of Upper Iguaçu watershed,Curitiba (Brazil)

Ingredients in home and personal care products, including UV filters and benzotriazoles, are high production volume chemicals extensively used in our daily life, despite several studies revealed their potential eco-toxicity and endocrine-disrupting capacity. Due to some features, such as high lipophilicity, low degradability, and persistence of many of these compounds, sediments can be considered a sink for them in the aquatic environment. In the present study, nine organic UV filters and three benzotriazoles were investigated for the first time in sediments from four urban rivers in Brazil. The contaminants were analyzed by liquid chromatography-tandem mass spectrometry (LC-MS/MS). The results revealed that octocrylene (OC), etylhexyl-methoxycinnamate (EHMC), benzophenone-3 (oxybenzone, BP3), and benzotriazole (BZT) were the predominant compounds adsorbed on the sediments, with concentrations ranging from 5.6 to 322.2 ng g⁻¹ dry weight. The results reported in this work constitute the first data on the accumulation of polar benzotriazoles and lipophilic organic UV filters in sediments from Brazil.

     

Comparison of the removal efficiency of endocrine disrupting compounds in pilot scale sewage treatment processes

The removal efficiency of endocrine disrupting compounds from effluents using pilot scale sewage treatment processes, including various treatment technologies, such as membrane bioreactors (MBR), nanofiltration (NF) and reverse osmosis (RO) for the purpose of water reuse, were estimated and compared. The calculated estrogenic activity, expressed in ng-EEQ/l, based on the concentration detected by GC/MS, and relative potencies for each target compound were compared to those measured using the E-screen assay. The removal efficiencies for nonylphenol, was within the range of 55-83% in effluents. High removal efficiencies of approximately >70% based on the detection limits were obtained for bisphenol A, E1, EE2 and genistein with each treatment processes, with the exception of E1 ( approximately 64%) using the MBR process. The measured EEQ values for the effluents from the MBR, NF and RO processes also indicated low estrogenic activities of 0.65, 0.23 and 0.05 ng-EEQ/l, respectively. These were markedly reduced values compared with the value of 1.2 ng-EEQ/l in influent. Consequently, the removals of EDCs in terms of the EEQ value from the biological and chemical determinations were sufficiently achieved by the treatment process applied in this study, especially in the cases of the NF and RO treatments.     

Removal of vaporous naphthalene using polyoxyethylenated nonionic surfactants

Previous research has demonstrated that an anionic surfactant can increase the solubility of the vapor phases of both naphthalene and sulfur dioxide in water. This study examines the feasibility of removing polycyclic aromatic hydrocarbons (PAHs) during gas absorption by adding the polyoxyethylenated nonionic surfactants tetraethylene glycol monodecyl ether (C10E4), octaethylene glycol monodecyl ether (C10E8), and octaethylene glycol monotetradecyl ether (C14E8), to water. The apparent solubility and absorption rates of naphthalene in surfactant solution were slightly higher than in pure water at a concentration lower than the critical micelle concentration (CMC). However, the apparent equilibrium naphthalene solubility increased linearly in proportion to the concentrations of nonionic surfactants because of the solubilization effect of micelles at concentrations above the CMC. The solubilization effect exceeded that of the reduced mass transfer coefficient, increasing the rate of absorption of vaporous naphthalene. For the four surfactants, the capacity to solubilize naphthalene was in the order C10E4 > C14E8 > C10E8 > sodium dodecyl sulfate (SDS) and was related to the hydrophile-lipophile balance values of the surfactants. The enrichment factors, which can express the degree of naphthalene solubility in solution, were 6.09-14.2 at a surfactant concentration of 0.01 M for the three polyoxyethylenated nonionic surfactants. Empirical findings confirm that adding nonionic surfactants increases the absorption efficiency of hydrophobic organic compounds (HOCs) using spray or packed tower.     

Identification of relevant micropollutants in Austrian municipal wastewater and their behaviour during wastewater treatment

The European Union has defined environmental quality standards (EQSs) for surface waters for priority substances and several other pollutants. Furthermore national EQSs for several chemicals are valid in Austria. The study investigated the occurrence of these compounds in municipal wastewater treatment plant (WWTP) effluents. In a first screening of 15 WWTPs relevant substances were identified, which subsequently were monitored in 9 WWTPs over 1 year (every 2 months). Out of 77 substances or groups of substances (including more than 90 substances) 13 were identified as potentially relevant in respect to water pollution and subjected to the monitoring, whereas most other compounds were detected in concentrations far below the respective EQS for surface waters and therefore not further considered. The preselected 13 compounds for monitoring were cadmium (Cd), nickel (Ni), copper (Cu), selenium (Se), zinc (Zn), diuron, polybrominated diphenyl ethers (PBDEs), di(ethyl-hydroxyl)phthalate (DEHP), tributyltin compounds (TBT), nonylphenoles (NP), adsorbable organic halogens (AOX) and the complexing agents ethylenediaminetetraacetic acid (EDTA) as well as nitrilotriacetic acid (NTA). In the effluents of WWTPs the concentrations of the priority substances Cd, NP, TBT and diuron frequently exceeded the respective EQS, whereas the concentrations for DEHP and Ni were below the respective EQS. The effluent concentrations for AOX, EDTA, NTA, Cu, Se and Zn frequently are in the range or above the Austrian EQS for surface waters. Besides diuron and EDTA all compounds are removed at least partially during wastewater treatment and for most substances the removal via the excess sludge is the major removal pathway. For the 13 compounds which were monitored in WWTP effluents population equivalent specific discharges were calculated. Since for many compounds no or only few information is available, these population equivalent specific discharges can be used to assess emissions from municipal WWTPs to surface waters as well as to make a first assessment of the impact of a discharge on surface waters chemical status. Comparing discharges and river pollution on a load basis, the influence of diffuse sources becomes obvious and therefore should also be taken into consideration in river management.     

Diuron mobility through vineyard soils contaminated with copper

The herbicide diuron is frequently applied to vineyard soils in Burgundy, along with repeated treatments with Bordeaux mixture (a blend of copper sulfate and calcium hydroxide) that result in elevated copper concentrations. Cu could in principle affect the fate and transport of diuron or its metabolites in the soil either directly by complexation or indirectly by altering the populations or activity of microbes involved in their degradation. To assess the effect of high Cu concentrations on diuron transport, an experiment was designed with ten undisturbed columns of calcareous and acidic soils contaminated with 17--509 mg kg(-1) total Cu (field-applied). Grass was planted on three columns. Diuron was applied to the soils in early May and in-ground lysimeters were exposed to outdoor conditions until November. Less than 1.2% of the diuron applied was found in the leachates as diuron or its metabolites. Higher concentrations were found in the effluents from the grass-covered columns (0.1--0.45%) than from the bare-soil columns (0.02--0.14%), and they were correlated with increases in dissolved organic carbon. The highest amounts of herbicide were measured in acidic-soil column leachates (0.98--1.14%) due to the low clay and organic matter contents of these soils. Cu also leached more readily through the acidic soils (32.8--1042 microg) than in the calcareous soils (9.5--63.4 microg). Unlike in the leachates, the amount of diuron remaining in the soils at the end of the experiment was weakly related to the Cu concentrations in the soils.     

Toxicity of municipal wastewater effluents contaminated by pentachlorophenol in Southwest Missouri

Toxicity of effluents from two sewage treatment plants in Joplin, Missouri, was tested using Ceriodaphnia dubia and Pimephales promelas. No test organisms survived in effluents from either plant, in effluents diluted with water from Turkey Creek (the receiving stream), or in water from Turkey Creek. Mortality was complete in all but the most dilute treatments of effluents, in which reconstituted water was used as the diluent. High concentrations of pentachlorophenol (130-970 microg liter(-1)) in effluents and the receiving stream likely caused mortality during the 7-day tests. Detectable concentrations of other phenolic compounds indicated the presence in Turkey Creek of other toxic by-products of pentachlorophenol manufacture. This study demonstrated the utility of biological tests of whole effluents to determine toxicity of wastewater effluents.     

Removal of organic compounds during treating printing and dyeing wastewater of different process units

Wastewater in Shaoxing wastewater treatment plant (SWWTP) is composed of more than 90% dyeing and printing wastewater with high pH and sulfate. Through a combination process of anaerobic acidogenic [hydraulic retention time (HRT) of 15h], aerobic (HRT of 20h) and flocculation-precipitation, the total COD removal efficiency was up to 91%. But COD removal efficiency in anaerobic acidogenic unit was only 4%. As a comparison, the COD removal efficiency was up to 35% in the pilot-scale upflow anaerobic sludge bed (UASB) reactor (HRT of 15h). GC-MS analysis showed that the response abundance of these wastewater samples decreased with their removal of COD. A main component of the raw influent was long-chain n-alkanes. The final effluent of SWWTP had only four types of alkanes. After anaerobic unit at SWWTP, the mass percentage of total alkanes to total organic compounds was slightly decreased while its categories increased. But in the UASB, alkanes categories could be removed by 75%. Caffeine as a chemical marker could be detected only in the effluent of the aerobic process. Quantitative analysis was given. These results demonstrated that GC-MS analysis could provide an insight to the measurement of organic compounds removal.     

Bioremediation of trace organic compounds found in precious metals refineries' wastewaters: a review of potential options

Platinum group metal (PGM) refining processes produce large quantities of wastewater, which is contaminated with the compounds that make up the solvents/extractants mixtures used in the process. These compounds often include solvesso, beta-hydroxyxime, amines, amides and methyl isobutyl ketone. A process to clean up PGM refinery wastewaters so that they could be re-used in the refining process would greatly contribute to continual water storage problems and to cost reduction for the industry. Based on the concept that organic compounds that are produced biologically can be destroyed biologically, the use of biological processes for the treatment of organic compounds in other types of waste stream has been favoured in recent years, owing to their low cost and environmental acceptability. This review examines the available biotechnologies and their effectiveness for treating compounds likely to be contained in precious metal extraction process wastewaters. The processes examined include: biofilters, fluidized bed reactors, trickle-bed bioreactors, bioscrubbers, two-phase partitioning bioreactors, membrane bioreactors and activated sludge. Although all processes examined showed adequate to excellent removal of organic compounds from various gaseous and fewer liquid waste streams, there was a variation in their effectiveness. Variations in performance of laboratory-scale biological processes are probably due to the inherent change in the microbial population composition due to selection pressure, environmental conditions and the time allowed for adaptation to the organic compounds. However, if these factors are disregarded, it can be established that activated sludge and membrane bioreactors are the most promising processes for use in the treatment of PGM refinery wastewaters.     

Changes in toxicity and genotoxicity of industrial sewage sludge samples containing nitro- and amino-aromatic compounds following treatment in bioreactors with different oxygen regimes

Goals, Scope and Background

From 2005, deposition of organic waste will be banned in Sweden. Likewise, in Germany and Austria, similar bans are being planned, and further countries will probably follow. Thus, there is a need to develop new methods and to refine established techniques for sludge management in the whole of the European Union. For this end, there is also an urgent need for appropriate ecotoxicological approaches to elucidate and assess the hazard potential of sewage sludge. Therefore, the present study was designed to assess the capacity of various established sludge treatment methods using different oxygen regimes to degrade recalcitrant nitro-substituted organic compounds and reduce their toxicity. Sewage sludge samples from a wastewater treatment plant in Sweden (Cambrex Karlskoga AB, industrial area Björkborn) receiving wastewater from industries manufacturing pharmaceutical substances, chemical intermediates and explosives were processed with different sludge treatment methods. Among other treatment methods, bioreactors (for anaerobic and aerobic sludge treatment) were used. In the present investigation, a battery ofin vitro bioassays was employed to compare the cytotoxic and genotoxic potentials of different fractions of sludge samples in order to elucidate whether the treatments were suitable to reduce the toxicity of the sludge.

Methods

In order to investigate the cytotoxicity of the extracts of treated and untreated sludge samples, the acute cytotoxicity test with the permanent cell line RTL-W1 was used. Genotoxicity was tested by means of the comet assay (single cell gel electro-phoresis) with RTL-W1cells, and mutagenicity was assessed with the Ames test using the Salmonella typhimurium strains TA98, TA98NR and TA100. Sludge toxicity was tested in different fractions of organic extracts produced by acetone and hexane extractions. The subsequent clean-up procedure (silica gel chro-matography and elution with hexane and dichloromethane) resulted in two fractions, a lipophilic hexane-fraction and a semi-lipophilic dichloromethane-fraction. For the genotoxicity and mutagenicity tests, these fractions were reunited at equal ratios.

Results and Discussion

The acute cytotoxicity test with RTL-Wl cells revealed a high cytotoxic potential for the semi-li-pophilic DM-fractions of all sludge samples with NR₅₀ values (= effective concentration for 50% cell death in the neutral red test) from 8.9 up to 20 mg sludge d.w./ml medium. A low cytotoxic potential for the hexane fractions of the untreated sludge samples (NR₅₀ 400 to < 400 mg sludge d.w./ml medium) was observed, whereas the hexane fractions of the treated sludge samples showed elevated cytotoxicity increasing further with treatment in the bioreactors. The comet assay indicated that three out of eight of the reunited fractions had a significant genotoxic potential. Whereas the genotoxic potential of one sample treated anaerobically was very high with an induction factor of 11.6, a similar sample (taken from the same anaerobic reactor four months later) and one untreated sample showed lower potentials. The samples treated in another anaerobic bioreactor as well as the samples treated aerobically showed no genotoxic potential. Results indicate that aerobic treatment was basically adequate for reducing the genotoxicity of the sludge, whereas anaerobic treatment was only partly useful for reduction of genotoxicity. The Ames test revealed a very high mutagenic potential for the reunited fractions of the untreated sludge samples with strain TA98 (maximum induction factors (IF_max up to 45) and a relatively high potential for one of the samples treated aerobically (S2, IF_max = 18 (TA98, S9-)), thus documenting the suitability of both anaerobic and aerobic treatments to reduce the mutagenicity of the samples, however, with the aerobic treatment being less effective. Conclusions. Overall, none of the microbiological treatments for wastewater sludge in bioreactors was found to be ideal for general toxicity reduction of the sludge samples. Whereas cytotoxicity of the sludge increased or levelled off in most cases following either treatment, genotoxicity both increased or decreased after anaerobic treatment, depending on the specific sample. However, mutagenicity could generally be reduced by anaerobic treatment and, to a lesser degree, by aerobic treatment. Recommendationsand Perspectives. The complex modification of the diverse damage potentials of sludge sample extracts by use of anin vitro biotest battery following treatment for toxicity reduction in bioreactors showed that considerations of different toxicological endpoints is essential for an adequate hazard assessment. Whereas in the case of cytotoxicity reduction, the reactors proved ineffective, mutagenicity could be reduced significantly at least in some cases in this case study.

     

厌氧氨氧化反应过程的三维荧光光谱解析

采用三维荧光光谱表征了厌氧氨氧化UASB反应器启动过程中和有机冲击负荷条件下的出水样品,应用平行因子分析方法解析样品中各主成分的三维荧光光谱图。研究结果表明,反应器启动阶段,出水中含有类蛋白质、类富里酸和类腐殖酸物质,主要源于接种污泥的菌体自溶和残留有机物厌氧发酵。随着反应器的运行,出水中的类蛋白质,类富里酸物质和类腐殖酸荧光物质逐渐减少。在有机冲击负荷条件下,出水中的类蛋白质组分迅速增加并成为反应器出水中的主要荧光物质。该研究为厌氧氨氧化的启动及运行控制的监控表征提供了新的方法。     

Occurrence and distribution of organic trace substances in waters from the Three Gorges Reservoir, China

This study deals with the evaluation of water quality of the Three Gorges Reservoir (TGR) in order to assess its suitability as a raw water source for drinking water production. Therefore, water samples from (1) surface water, (2) tap water, and (3) wastewater treatment plant effluents were taken randomly by 2011–2012 in the area of the TGR and were analyzed for seven different organic contaminant groups (207 substances in total), applying nine different analytical methods. In the three sampled water sources, typical contaminant patterns were found, i.e., pesticides and polycyclic aromatic hydrocarbons (PAH) in surface water with concentrations of 0.020–3.5 μg/L and 0.004–0.12 μg/L, disinfection by-products in tap water with concentrations of 0.050–79 μg/L, and pharmaceuticals in wastewater treatment plant effluents with concentrations of 0.020–0.76 μg/L, respectively. The most frequently detected organic compounds in surface water (45 positives out of 57 samples) were the pyridine pesticides clopyralid and picloram. The concentrations might indicate that they are used on a regular basis and in conjunction in the area of the TGR. Three- and four-ring PAH were ubiquitously distributed, while the poorly soluble five- and six-ring members, perfluorinated compounds, polychlorinated biphenyls, and polybrominated diphenyl ethers, were below the detection limit. In general, the detected concentrations in TGR are in the same range or even lower compared to surface waters in western industrialized countries, although contaminant loads can still be high due to a high discharge. With the exception of the two pesticides, clopyralid and picloram, concentrations of the investigated organic pollutants in TGR meet the limits of the Chinese Standards for Drinking Water Quality GB 5749 (Ministry of Health of China and Standardization Administration of China 2006) and the European Union (EU) Council Directive 98/83/EC on the quality of water intended for human consumption (The Council of the European Union 1998), or rather, the EU Directive on environmental quality standards in the field of water policy (The European Parliament and The Council of the European Union 2008). Therefore, the suggested use of surface water from TGR for drinking water purposes is a valid option. Current treatment methods, however, do not seem to be efficient since organic pollutants were detected in significant concentrations in purified tap water.     

Effect of alkalinity on the performance of a simulated landfill bioreactor digesting organic solid wastes

This study investigated the effects of alkalinity on the anaerobic treatment of the organic solid wastes collected from the kitchen of Engineering Faculty in Dokuz Eylul University, Izmir, Turkey and the leachate characteristics treated in three simulated landfill anaerobic bioreactors. All of the reactors were operated with leachate recirculation. One reactor was operated without alkalinity addition. The second reactor was operated by the addition of 3 g l-1 d-1 of NaHCO3 alkalinity to the leachate and the third reactor was operated by the addition of 6 g l-1 d-1 NaHCO3 alkalinity to the leachate. After 65 d of anaerobic incubation, it was observed that the chemical oxygen demand (COD), volatile fatty acids (VFA) concentrations, and biochemical oxygen demand to chemical oxygen demand (BOD5/COD) ratios in the leachate samples produced from the alkalinity added reactors were lower than the control reactor while the pH values were higher than the control reactor. The COD values were measured as 18900, 3800 and 2900 mg l-1 while the VFA concentrations were 6900, 1400 and 1290 mg l-1, respectively, in the leachate samples of the control, and reactors containing 3 g l-1 NaHCO3 and 6 g l-1 NaHCO3 after 65 d of anaerobic incubation. The total nitrogen (TN), total phosphorus (TP) and ammonium nitrogen (NH4-N) concentrations in organic solid waste (OSW) significantly reduced in the reactor containing 6 g l-1 NaHCO3 by d 65. The values of pH were 6.54, 7.19 and 7.31, after 65 d of anaerobic incubation, respectively, in the aforementioned reactors results in neutral environmental conditions in alkalinity added reactors. Methane percentage of the control, reactors containing 3 g l-1 NaHCO3 and 6 g l-1 NaHCO3 were 37%, 64% and 65%, respectively, after 65 d of incubation. BOD5/COD ratios of 0.27 and 0.25 were achieved in the 3 and 6 g l-1 NaHCO3 containing reactors, indicating a better OSW stabilization. Alkalinity addition reduced the waste quantity, the organic content of the solid waste and the biodegradation time.     

Evaluation of the treatment efficiencies of paper mill whitewaters in terms of organic composition and toxicity

The efficiency of several lab scale treatments (aerobic, anaerobic and ozone or combination of these) was evaluated using two packaging board mill whitewaters. The effect of the different treatments on the elimination of the organic load, the chemical oxygen demand (COD) and the toxicity was tested as well as the relationship between these parameters. Biocides, phenolic compounds, surfactants, plasticiziers and wood extractives were identified in untreated and treated whitewaters by liquid chromatography coupled with mass spectrometry (LC-MS) or gas chromatography coupled with mass spectrometry (GC-MS). A strong dependency on the water type and treatment efficiency was observed, being the combination of anaerobic and aerobic treatments the best option to reduce the organic contaminants in these waters, although in some cases, the toxicity did not decrease. However, ozone as post-treatment permitted a further reduction of organic compounds, toxicity and COD.     

META V. A model of photodegradation for the prediction of photoproducts of chemicals under natural-like conditions.

Our goal was to create a photodegradation model based on the META expert system [G. Klopman, M. Dimayuga, J. Talafous, J. Chem. Inf. Comput. Sci. 34 (1994a) 1320-1325]. This requires the development of a dictionary of photodegradation pathways. Equipped with such a dictionary, we found that META successfully predicts degradation pathways of organic compounds under UV light. Our model was tested on a wide range of industrial compounds for which literature data exists. The results were excellent as the hit/miss ratio was better than 92%. This work complements our previous elaboration of equivalent mammal metabolism, aerobic and anaerobic biodegradation models.     

Photodegradation of surfactants. XV: Formation of SO4 ions in the photooxidation of sulfur-containing surfactants

Three types of surfactants and related reference compounds containing sulfonate (-SO₃Na), sulfate (-OSO₃Na) or thioether carboxylate (-S-Cn-COOK) group were photodecomposed in an aqueous heterogeneous dispersion system. The photomineralization to SO₄²⁻ions was examined for the surfactants with different chemical structures. The photocatalytic activities of TiO₂ and ZnO were compared for the sulfonates of dodecylbenzene sulfonate (DBS) and polystyrene sulfonate (PSS), the sulfates of sodium dodecyl sulfate (SDS), and the potassium salts of S-dodecylthioglycol acid (TGA), S-dodecylthiopropionic acid (TPA) and S-dodecylthiomalic acid (TMA). ZnO catalyst exhibited higher activity in the formation of SO₄²⁻ion than TiO₂ catalyst.