Biomedical subjects

M Jekel

Publications and source records attributed to M Jekel.

At least 19 recordsLinked to original sources

PubMed2006

Impact of colloidal and soluble organic material on membrane performance in membrane bioreactors for municipal wastewater treatment.

Two parallel membrane bioreactors (2 m3 each) were operated over a period of 2 years. Both pilots were optimised for nitrification, denitrification, and enhanced biological phosphorous elimination, treating identical municipal wastewater under comparable operating conditions. The only constructional difference between the pilots was the position of the denitrification zone (pre-denitrification in pilot 1 and post-denitrification in pilot 2). Despite identical modules and conditions, the two MBRs showed different permeabilities and fouling rates. The differences were not related to the denitrification scheme. In order to find an explanation for the different membrane performances, a one-year investigation was initiated and the membrane performance as well as the operating regime and characteristics of the activated sludge were closely studied. MLSS concentrations, solid retention time, loading rates, and filtration flux were found not to be responsible for the different performance of the submerged modules. These parameters were kept identical in the two pilot plants. Instead, the non-settable fraction of the sludges (soluble and colloidal material, i.e. polysaccharides, proteins and organic colloids) was found to impact fouling and to cause the difference in membrane performance between the two MBR. This fraction was analysed by spectrophotometric and size exclusion chromatography (SEC) methods. In a second step, the origin of these substances was investigated. The results point to microbiologically produced substances such as extracellular polymeric substances (EPS) or soluble microbial products (SMP).

Bioreactors↗

PubMed2005

Correlation between membrane fouling and soluble/colloidal organic substances in membrane bioreactors for municipal wastewater treatment.

Two similar membrane bioreactors of 2 m3 each were operated in parallel over two years under the same operational conditions, fed with the same municipal wastewater. The only process and operational difference between both pilot plants was the position of the denitrification zone (pre-denitrification in pilot 1 and post-denitrification in pilot 2). Despite parallel operation, the two MBRs exhibited different fouling rates and decreases in permeability. These differences could not be accounted for by MLSS concentrations, loading rates, or filtration flux. In a one-year investigation, soluble and colloidal organic material in the activated sludge of both MBR was regularly analysed by spectrophotometric and Size Exclusion Chromatography (SEC) methods. The larger organic molecules present in the sludge water phase (i.e. polysaccharides, proteins and organic colloids) originating from microbial activity (extracellular polymeric substances) were found to impact on the fouling and to explain the difference in membrane performance between the two MBR units. In both pilot plants, a linear relationship could be clearly demonstrated between the fouling rate of the membrane and the concentration of polysaccharides in the sludge water phase during a 5 month operational period at an SRT of 8 days.

Animals↗

PubMed2005

Planning, modelling and assessing source control concepts on catchment scale.

Today's water management practice was identified often not to be consistently structured. Usually the decision space is not clearly depicted and then systematically explored. Often stakeholders are involved too late and many objectives are neglected. An adaptive DSS is being developed to help overcoming these problems. Core of the DSS is a "decision matrix", which has been implemented as a web based application (www.wsm300.de). The management objectives are represented by the indicators labelling the rows. They will be the result of a discussion of the objectives and problems in the specific sub-basin, which is supported by the catalogue of indicators. The columns of the matrix are specified by the scenarios whose development is supported by the database of measures and a Geographical Information System (GIS). The matrix, once the labels are defined, serves as a plot for the planning process, defining clearly which objectives have to be considered and which indicator-values have to be calculated. The DSS further includes a concept and tools for the combination of existing software components and supports the processing of model-outputs to indicator-values. Filled with the indicator-values the matrix allows a comparison of the scenarios and provides a good base for a decision. Multi-criteria decision aid methods can (if desired) further help to find the optimal scenario and to mediate between stakeholders. Finding the optimal scenario will likely be an iterative process.

Databases, Factual↗

PubMed2004

Ozonation of persistent DOC in municipal WWTP effluent for groundwater recharge.

Groundwater recharge is becoming common in areas where the withdrawal of groundwater exceeds its natural recharge. Wastewater treatment plant (WWTP) effluent can be used for this purpose, but persistent organic compounds can only be partly removed during soil passage. This point was confirmed in degradation tests using soil columns in which the DOC of a membrane bioreactor (MBR) permeate could only be reduced by 15% and adsorbable organic iodine (AOI) by 2%. However, ozonation was found to improve biodegradation and at the maximum formation of biodegradable DOC at 2.5 mg O3/mg DOC0, the DOC values of MBR permeate (11-13 mg/L) could be reduced in aerobic degradation batch tests to the DOC of Berlin drinking water (3-5 mg/L). A combination of ozonation at 1.9 g O3/g DOC0 with soil passage could adjust DOC, UVA254, colour (436 nm) and the molecular DOC size distribution to drinking water ranges, but AOI was only reduced from 143 microg/L to 92 microg/L and remained high compared to tap water (2.2 microg/L). The extremely persistent X-ray contrast compound iopromide, which represents part of AOI, was spiked into MBR permeate at a low concentration. Iopromide was reduced by 88% during ozonation, but AOI only decreased by 23% indicating that a transformation, but not a mineralization, of iodinated organic compounds occurs.

Absorption↗

PubMed2004

Occurrence of benzothiazoles in municipal wastewater and their fate in biological treatment.

A number of 2-substituted benzothiazoles that are known to be used as fungicides, corrosion inhibitors and vulcanization accelerators in industry have been analyzed in municipal wastewater and the effluents of activated sludge and membrane bioreactor (MBR) treatment over a three month period. All six analytes were regularly detected in the municipal wastewater by liquid chromatography-mass spectrometry and amount to a total concentration of 3.4 microg/L. Of these compounds benzothiazole-2-sulfonic acid (1,700 ng/L), benzothiazole (850 ng/L) and 2-hydroxybenzothiazole (500 ng/L) were most prominent. The source of the benzothiazole emission is yet unknown. Activated sludge treatment did not reduce total benzothiazole concentration significantly. Removals of the individual compounds ranged from 90% for 2-mercaptobenzothiazole and 70% for hydroxybenzothiazole to 40% for benzothiazole. The concentration of benzothiazole-2-sulfonic acid increased by 20%, whereas 2-methylthiobenzothiazole increased by 160% during activated sludge treatment, likely due to the methylation of mercaptobenzothiazole. Total benzothiazole removal in two parallely operated MBRs was significantly better (43%) than in the conventional activated sludge treatment. Namely benzothiazole and benzothiazole-2-sulfonic acid were more effectively removed. This first systematic study on the occurrence of benzothiazoles in municipal wastewater has shown that this is a relevant class of trace contaminants in municipal wastewater which is only incompletely removed in biological wastewater treatment. Emission from sewage treatment is dominated by the most polar benzothiazole-2-sulfonic acid. MBR treatment may reduce but cannot avoid this emission.

Benzothiazoles↗

PubMed2004

Bank filtration: a suitable process for the removal of iodinated X-ray contrast media?

After bank filtration, effluent influenced surface waters are often used as raw drinking water. It is known that high concentrations of iodinated X-ray contrast media are detectable in such surface waters and thus, more knowledge about the behaviour of the contrast media during bank filtration is necessary and the subject of investigations in this study. The adsorbable organic iodine (AOI), four widely used iodinated X-ray contrast media and four possible transformation products were quantified in an influenced lake, five groundwater wells and a drinking water well. Under anoxic conditions the AOI as well as the concentration of the contrast media are decreased by bank filtration, whereby the AOI is decreased by 64% and the contrast media concentration can be reduced up to 95%, depending on the compound. In the raw drinking water the following average concentrations were determined: lopromid < 20 ng/L, Diatrizote 166 ng/L, lopamidol 166 ng/L and lohexol 34 ng/L. Instationary conditions during the sampling period indicate that, at least under anoxic conditions, a large part of the contrast media and transformation products, which are still iodinated, may be associated to colloids and/or humic material.

Colloids↗

PubMed2004

Organic colloids and their influence on low-pressure membrane filtration.

Wastewater treatment by low-pressure membrane filtration (MF and UF) is affected to a large extent by macromolecules and colloids. In order to investigate the influence of organic colloids on the membrane filtration process, colloids were isolated from a wastewater treatment plant effluent using a rotary-evaporation pre-concentration step followed by dialysis. Stirred cell tests were carried out using redissolved colloids, with and without additional glass fiber filtration. After constant pressure membrane filtration of 190 L/m2, the initial flux had declined by 50% for colloids > 6-8 kD (glass fiber filtered) with a hydrophilic MF membrane and for colloids > 12-14 kD (glass fiber filtered) with a hydrophobic MF membrane. For the non-filtered colloidal solutions, the flux decline was even steeper with the flux being below 10% of the initial flux after 190 L/m2 were passed through the membranes. As with larger particles, colloids form a filtration cake layer on top of the membrane surface when used as isolates without prior filtration. This filtration cake is easily removed during backwashing. However, polysaccharides as a macromolecular component of the colloid isolate cause severe fouling by the formation of a gel layer on the membrane surface that is difficult to remove completely.

Colloids↗

PubMed2003

Kinetic study of reactions between ozone and benzothiazole in water.

Benzothiazoles are frequently present in wastewater from rubber related applications, and may be found in surface and underground water bodies causing significant environmental impact. Cost effective treatment processes to deal with such contaminants are needed in both small and large-scale applications. These compounds are poorly biodegradable and could be removed by ozone oxidation before discharge to recipient water courses. Unfortunately, there is limited experimental data reported in the literature on such processes involving benzothiazoles. This article presents experimental data on ozone treatment of benzothiazole (BT), with a view to process design. The effects of pH and radical scavengers on process rate and removal efficiency were assessed at bench scale. Experimental results show that BT could be effectively removed using ozonisation, particularly at pH above 4. The presence of free radical scavengers drastically reduced the BT removal rate even at very low concentrations. Both direct and indirect reactions between ozone and BT were adequately described by second order kinetic schemes, with rate constants estimated at 20 degrees C: kD = 2.3 mol l(-1) s(-1) and kI = 6 x 10(9) mol l(-1) s(-1), respectively. The free radical mechanism accounted for 83-96% of BT removal rate within the pH range 2-9, at 20 degrees C.

Free Radical Scavengers↗

PubMed2002

Ozonation of 1-naphthalene, 1,5-naphthalene, and 3-nitrobenzene sulphonic acids in aqueous solutions.

Ozone oxidation kinetics of 1-naphthalene (INS), 1,5-naphthalene (1,5NDS), and 3-nitrobenzene (3NBS) sulphonic acid is reported here. The contribution of indirect free-radical pathways and direct ozone reactions are accounted for in the proposed model. Second order kinetic constants of direct reactions were estimated at around 252 (M(-1)s(-1)), 41 (M(-1)s(-1)) and 22 (M(-1)s(-1)), for INS, 1,5NDS, and 3NBS sulphonic adds, respectively. At pH 3, the indirect reaction accounted for 2%, 15% and 4% of total primary oxidation of 1NS, 1,5NBS, and 3NBS sulphonic acids, respectively. At pH 9, indirect reaction contribution increased to 73%, 84% and 48%, respectively. C4 compounds (maleic and fumaric acids), C2 (oxalic), C1 (formic) and sulphate were identified as oxidation by-products in all cases. TOC slowly decreased throughout ozonation, reaching around 40-60% and 60-70% reduction over 90 min, at pH 7 and 3, respectively.

Kinetics↗

PubMed2002

Adsorption of reactive dyes to granulated iron hydroxide and its oxidative regeneration.

Granulated iron hydroxide (beta-FeOOH) is used as a regenerable sorbent and catalyst for reactive dye removal in textile wastewater treatment. In oxidative regeneration the previously sorbed reactive dye is catalytically oxidized after activation of hydrogen peroxide to hydroxyl radicals on the FeOOH surfaces to regain adsorption capacity and reuse the sorbents. A high initial H2O2 concentration is needed for an efficient mass transfer water/solid but its consumption per oxidized dye results only in 7-25 mg mg(-1). At room temperature a regeneration time of 3.5 h is necessary for decolorization and 6 h for further decomposition of the formed oxidation products to enable a reloading without any loss in adsorption capacity. Compared to Fenton's reagent, this oxidation process takes advantage of pH-independence between 4 and 8 and additionally no sludge is produced. Salts are commonly used in textile dying processes. While chloride improves the dye sorption, the presence of sulfate results in deteriorating sorption. Carbonate reacts as a scavenger of hydroxyl radicals resulting in a higher hydrogen peroxide consumption, but the efficiency of dye oxidation is only slightly affected. Nearly 20% of DOC of the sorbed dye can be attributed to short chain organic acids (formate, acetate, oxalate) indicating the far-reaching catalytic oxidation and enabling biological post-treatment.

Adsorption↗

PubMed2001

Quantification of triiodinated benzene derivatives and X-ray contrast media in water samples by liquid chromatography-electrospray tandem mass spectrometry.

A method for the analysis of iodinated X-ray contrast media and possible metabolites in environmental water samples is presented. The method consists of a sequential solid-phase extraction followed by high-performance liquid chromatography coupled with tandem mass spectrometry for detection. The recoveries for the analytes in tap water varies between 70 and 100%. For matrix poor samples the detection limit is in the lower ng/l range. In case of native, complex samples the recoveries are lower and the parallel analysis of a spiked sample is necessary to obtain reliable data. With the presented method iodinated X-ray contrast media could be detected and quantified in a sewage treatment plant effluent, in a receiving channel and lake. In the receiving lake the concentrations are still high with values between 0.5 and 4 microg/l.

Benzene Derivatives↗

PubMed2001

Exact mass measurements on-line with high-performance liquid chromatography on a quadrupole mass spectrometer.

Exact mass measurements were performed on-line with high-performance liquid chromatography on a quadrupole mass spectrometer. Compounds with molecular weights from 98 to 797, mainly aromatic sulfonates and sulfonamides, were analyzed with electrospray ionization in positive or negative mode. Internal mass calibration compounds were continuously added after separation. A Gaussian fit of the mass errors of 808 individual measurements (concentrations of 1-10 mg/L, 20-200 ng absolute on column) resulted in a mean error of 0.1 mmu (0.45 ppm) and a standard deviation sigma of 1.5 mmu (5.4 ppm). The 99.7% confidence intervals (3sigma) were +/-4.5 mmu (+/-16.2 ppm) for single mass measurements. Averaging 10 measurements further reduced the errors to less than +/-1.5 mmu (+/-5 ppm). Isobaric interferences with ions resulting from the mass calibrants were avoided by the use of complementary mass calibrants. The results were verified (differences below +/-4.5 mmu) with a LC/ oa-TOFMS. Limited mass range chromatograms were used to enhance selectivity in the analysis of mixtures. The method was applied to determine the elemental composition of a potential dye metabolite detected in anaerobically treated textile wastewater.

Journal Article↗

PubMed2001

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.

Adsorption↗

PubMed2001

Cucurbituril for water treatment. Part II: Ozonation and oxidative regeneration of cucurbituril.

In Part I it was shown, that cucurbituril has high sorption capacities for the removal of reactive dyes from textile wastewater; despite the partial dissolution of this sorbent. Ozonation has been suggested as a regeneration step for loaded cucurbituril. Ozonation of loaded and pure cucurbituril was therefore evaluated. Dissolved cucurbituril reacts with ozone forming oxidation products like nitrite, nitrate, formate, acetate and oxalate. Oxidation is enhanced at alkaline pH. Dye-loaded cucurbituril suspended in water can be decolorized by ozone, but the ozone consumption is tip to seven times higher than for ozonation of the dissolved dyes without cucurbituril. Loaded columns can be regenerated by ozone gas, but dissolution of cucurbituril results in a higher DOC content than the initial one to be removed. Therefore oxidative regeneration does not seem to be a feasible approach in this case.

Bridged-Ring Compounds↗

PubMed2001

Membrane filtration of two sulphonamides in tertiary effluents and subsequent adsorption on activated carbon.

The adsorption behaviour of two polar organic micropollutants (N-n-butylbenzenesulphonamide and sulphmethoxazole) onto powdered activated carbon (PAC) under competitive conditions prior to and after filtration with a tight ultrafiltration membrane was examined. The sulphonamides were spiked into microfiltered tertiary municipal effluent in microg L(-1) quantities. Ultrafiltration of these effluents resulted in better adsorbability for both the micropollutants and the background organic matter in the permeates compared to the feed waters. This behaviour seems to be caused by a reduced blocking of micropores by lower concentrations of high molecular weight compounds in membrane filtrates. A combined treatment of ultrafiltration prior to adsorption can therefore reduce the carbon demand for potentially harmful micropollutants in effluents.

Adsorption↗

PubMed2001

Comparison of advanced oxidation processes in flow-through pilot plants (part I).

The advanced oxidation processes (AOPs) UV/H2O2, UV/O3 and O3/H2O2 were optimised to achieve a 90% degradation of the micropollutant atrazine in continuous-flow reactors. The experiments were performed with spiked Berlin tap-water. The comparison of mechanistically different oxidation systems needs a non-specific figure-of-merit to avoid influences by system-inherent parameters. The chosen figure-of-merit consists of the electrical energy per order of magnitude in oxidation per m3, EE/o. The combination O3/H2O2 proved to be the most efficient process by means of energy consumption.

Atrazine↗

PubMed2001

Comparison of advanced oxidation processes in flow-through pilot plants (part II).

Abstract The comparison of mechanistically different advanced oxidation processes (AOPS) UV/H2O2, UV/03 and O3/H2O2 needs a non-specific figure-of-merit to avoid influences by system-inherent parameters. The chosen figure-of-merit consists of the electrical energy per order of magnitude in oxidation per m3, EE/O. Results from own experiments were compared with data derived f rom the literature. Considered were batch-experiments, pilot-plants and full-scale plants. The combination O3/H2O2 proved to be the most efficient process by means of energy consumption irrespective of the size of the plant.

Equipment Design↗

PubMed2001

Kinetics of ozone reactions with 1-naphthalene, 1,5-naphthalene and 3-nitrobenzene sulphonic acids in aqueous solutions.

This paper describes the ozone oxidation kinetics of 1-naphthalene (1 NS), 1,5-naphthalene (1,5NDS), and 3-nitrobenzene (3NBS) sulphonic acid. The presence of hydroxyl radicals and their effect on the overall rate of reaction was studied. Second order kinetic constants of direct reactions were estimated at around 252 M(-1) s(-1), 41 M(-1) s(-1) and 22 M(-1) s(-1), for 1NS, 1,5NDS, and 3NBS sulphonic acids, respectively. At pH 3, the indirect reaction accounted for 2%, 15% and 4% of total primary oxidation of 1 NS, 1,5NBS, and 3NBS sulphonic acids, respectively. At pH 9, indirect reaction contribution increased to 73%, 84% and 48%, respectively. C4 compounds (maleic and fumaric acids), C2 (oxalic), C1 (formic) and sulphate were identified as oxidation by-products in all cases. TOC slowly decreased throughout ozonation, reaching around 40-60% and 60-70% reduction over 90 minutes at pH 7 and 3, respectively.

Benzenesulfonates↗