Effect of toluene on siloxane biodegradation and microbial communities in biofilters.

The removal of volatile methyl siloxanes (VMS) from landfill biogas is crucial for clean energy utilization. VMS are usually found together with aromatic compounds in landfill biogas of which toluene is the major representative. In the present study, two biofilters (BFs) packed with either woodchips and compost (WC) or perlite (PER) were used to study the (co-) removal of octamethyltrisiloxane (L3) and octamethylcyclotetrasiloxane (D4) from gas in presence and absence of toluene, used as a representative aromatic compound. The presence of low inlet toluene concentrations (315 ± 19 - 635 ± 80 mg toluene m-3) enhanced the VMS elimination capacity (EC) in both BFs by a factor of 1.8 to 12.6. The highest removal efficiencies for D4 (57.1 ± 1.1 %; EC = 0.12 ± 0.01 gD4 m-3 h-1) and L3 (52.0 ± 0.6 %; EC = 0.23 ± 0.01 gL3 m-3 h-1) were observed in the BF packed with WC. The first section of the BFs (EBRT = 9 min), where toluene was (almost) completely removed, accounted for the majority (87.7 ± 0.6 %) of the total VMS removal. Microbial analysis revealed the impact of VMS and toluene in the activated sludge, showing a clear selection for certain genera in samples influenced by VMS in the presence (X2) or absence (X1) of toluene, such as Pseudomonas (X1 = 0.91 and X2 = 12.0 %), Sphingobium (X1 = 0.09 and X2 = 4.04 %), Rhodococcus (X1 = 0.42 and X2 = 3.91 %), and Bacillus (X1 = 7.15 and X2 = 3.84 %). The significant maximum EC values obtained by the BFs (0.58 gVMS m-3 h-1) hold notable significance in a combined system framework as they could enhance the longevity of traditional physicochemical methods to remove VMS like activated carbon in diverse environmental scenarios.

Biofiltration of gaseous mixtures of dimethyl sulfide, dimethyl disulfide and dimethyl trisulfide: Effect of operational conditions and microbial analysis.

The efficient removal of volatile sulfur compounds (VSCs), such as dimethyl sulfide (DMS), dimethyl disulfide (DMDS) and dimethyl trisulfide (DMTS), is crucial due to their foul odor and corrosive potential in sewer systems. Biofilters (BFs) offer promise for VSCs removal, but face challenges related to pH control and changing conditions at full scale. Two BFs, operated under acidophilic conditions for 78 days, were evaluated for their performance at varying inlet concentrations and empty bed residence times (EBRTs). BF1, incorporating 4-6 mm marble limestone for pH control, outperformed BF2, which used NaHCO3 in the nutrient solution. BF1 displayed better resilience, maintained a stable pH of 4.6 ± 0.6, and achieved higher maximum elimination capacities (ECmax, 41 mg DMS m-3 h-1 (RE 38.3%), 146 mg DMDS m-3 h-1 (RE 83.1%), 47 mg DMTS m-3 h-1 (RE 93.1%)) at an EBRT of 56 s compared to BF2 (9 mg DMS m-3 h-1 (RE 7.1%), 9 mg DMDS m-3 h-1 (RE 4.8%) and 11 mg DMTS m-3 h-1 (RE 26.6%)). BF2 exhibited pH stratification and decreased performance after feeding interruptions. The biodegradability of VSCs followed the order DMTS > DMDS > DMS, and several microorganisms were identified contributing to VSCs degradation in BF1, including Bacillus (14%), Mycobacterium (11%), Acidiphilium (7%), and Acidobacterium (3%).

Auxin, Abscisic Acid and Jasmonate Are the Central Players in Rice Sheath Rot Caused by Sarocladium oryzae and Pseudomonas fuscovaginae.

Sheath rot is an emerging rice disease that causes severe yield losses worldwide. The main causal agents are the toxin producers Sarocladium oryzae and Pseudomonas fuscovaginae. The fungus S. oryzae produces helvolic acid and cerulenin and the bacterium P. fuscovaginae produces cyclic lipopeptides. Helvolic acid and the lipopeptide, fuscopeptin, inhibit membrane-bound H+-ATPase pumps in the rice plant. To manage rice sheath rot, a better understanding of the host response and virulence strategies of the pathogens is required. This study investigated the interaction of the sheath rot pathogens with their host and the role of their toxins herein. Japonica rice was inoculated with high- and low-helvolic acid-producing S. oryzae isolates or with P. fuscovaginae wild type and fuscopeptin mutant strains. During infection, cerulenin, helvolic acid and the phytohormones abscisic acid, jasmonate, auxin and salicylic acid were quantified in the sheath. In addition, disease severity and grain yield parameters were assessed. Rice plants responded to high-toxin-producing S. oryzae and P. fuscovaginae strains with an increase in abscisic acid, jasmonate and auxin levels. We conclude that, for both pathogens, toxins play a core role during sheath rot infection. S. oryzae and P. fuscovaginae interact with their host in a similar way. This may explain why both sheath rot pathogens cause very similar symptoms despite their different nature.

Occurrence patterns of pharmaceutical residues in wastewater, surface water and groundwater of Nairobi and Kisumu city, Kenya.

Emerging organic contaminants have not received a lot of attention in developing countries, particularly Africa, although problems regarding water quantity and quality are often even more severe than in more developed regions. This study presents general water quality parameters as well as unique data on concentrations and loads of 24 pharmaceuticals including antibiotic, anti(retro)viral, analgesic, anti-inflammatory and psychiatric drugs in three wastewater treatment plants, three rivers and three groundwater wells in Nairobi and Kisumu. This allowed studying removal efficiencies in wastewater treatment, identifying important sources of pharmaceutical pollution and distinguishing dilution effects from natural attenuation in rivers. In general, antiretrovirals and antibiotics, being important in the treatment of common African diseases such as HIV and malaria, were in all matrices more prevalent as compared to the Western world. Wastewater stabilization ponds removed pharmaceuticals with an efficiency between 11 and 99%. Despite this large range, a different removal is observed for a number of compounds, as compared to more conventional activated sludge systems. Total concentrations in river water (up to 320 µg L(-1)) were similar or exceeded concentrations in untreated wastewater, with domestic discharges from slums, wastewater treatment plant effluent and waste dumpsites identified as important sources. In shallow wells situated next to pit latrines and used for drinking water, the recalcitrant antiretroviral nevirapine was measured at concentrations as high as 1-2 µg L(-1). Overall, distinct pharmaceutical contamination patterns as compared to the Western world can be concluded, which might be a trigger for further research in developing regions.

Germ-free sea bass Dicentrarchus labrax larval model: a valuable tool in the study of host-microbe interactions.

A thorough understanding of host-microbe interactions is crucial for more efficient disease management in the marine larviculture industry. As demonstrated in terrestrial animal research, gnotobiotic systems (involving animals cultured in germ-free conditions or inoculated with known microorganisms) are excellent tools to extend our understanding of the mechanisms involved in host-microbe interactions and allow the evaluation of new treatments for diseases. In this study, we introduce a germ-free European sea bass Dicentrarchus labrax larval model, independent of the continuous addition of antimicrobial agents. This model has an experimental set-up that allows addition of live feed to the larvae without compromising the germ-free status. This model will facilitate and render aquaculture research more effective in terms of mitigation fish larval diseases.

Parameter study on the efficiency of ozonation for biologically treated landfill leachate.

Ozonation was investigated as a potential post-treatment step for biologically treated landfill leachate to enhance the biodegradability and observe the influence of the initial organic matter concentration and pH. Changes in COD, UV absorption at 254 nm (UVA254) and BOD content were measured during and after ozonation, and the ozone utilisation efficiency at different conditions was calculated. The initial COD concentration was found to influence the absolute removal of UVA254 significantly, but especially changes in pH influenced the ozone reactions. Increased pH (pH 10) most probably increased the overall hydroxyl radical production leading to a higher COD removal and a much better ozone utilisation compared to lower pH. This in contrast to initial COD variations which had little influence on the determined ozone utilisation. Regardless of initial COD content or pH, on average 10% of the initial COD content was converted to BOD, next to 10% COD that was removed.

High-resolution time-of-flight mass spectrometry for suspect screening and target quantification of pharmaceuticals in river water.

The growing interest in screening and quantification of potential harmful pharmaceuticals in the environment requests multi-residue analytical techniques. Large-volume injection ultra performance liquid chromatography (LVI-UPLC) in combination with full-spectrum high-resolution mass spectrometry (HRMS) is a promising alternative for the state-of-the-art MS/MS instruments, because of its ability to analyse a virtually unlimited number of analytes thereby avoiding the time-consuming sample enrichment steps. We developed and fully validated an innovative analytical method for suspect screening and target quantification of a set of 69 pharmaceutical compounds in surface water based on LVI-UPLC coupled to a quadrupole time-of-flight (QTOF) MS. In a systematic research, we showed that optimal mass accuracy was obtained after centroiding the spectra. A novel suspect screening strategy was developed, assuring the detection of 95% of the pharmaceuticals spiked in surface water by modelling the variability of the signal intensity-dependent accurate mass error. A first screening of five Belgian river water samples revealed the occurrence of 30 pharmaceuticals (antibiotics, analgesics, antidepressants, alkylating agents, antiinflammatories, etc.). Concentrations between 17 ng/L up to 3.3 microg/L were subsequently measured by the validated target quantification.

Selective accurate-mass-based analysis of 11 oxy-PAHs on atmospheric particulate matter by pressurized liquid extraction followed by high-performance liquid chromatography and magnetic sector mass spectrometry.

An innovative analytical method based on high-performance liquid chromatography and atmospheric pressure chemical ionization magnetic sector mass spectrometry was developed and optimized to determine trace concentrations of 11 compounds belonging to the group of the seldom-analyzed oxy-PAHs (phenanthrene-9,10-dione, chrysene-5,6-dione, benzo[a]pyrene-4,5-dione, benzo[a]pyrene-1,6-dione, benzo[a]pyrene-3,6-dione, benzo[a]pyrene-6,12-dione, 4-oxa-benzo[def]chrysene-5-one, pyrene-1-carboxaldehyde, benzo[de]anthracene-7-one, benzo[a]anthracene-7,12-dione, and napthacene-5,12-dione) on airborne particulate matter (PM(10)). The mass spectrometer was operated in multiple ion detection mode, allowing for selective accurate mass detection (mass resolution of 12,000 full width at half maximum) of the oxy-PAHs characteristic ions. Optimization of both the vaporizer (450 °C) and capillary temperature (350 °C) resulted into instrumental detection limits in the range between 7 (benzo[a]pyrene-1,6-dione) and 926 pg (benzo[a]anthracene-7,12-dione). The advanced pressurized liquid extraction (PLE) and the more traditionally used ultrasonic extraction (USE) were compared using ethyl acetate as an extraction solvent. For both techniques, high recoveries from spiked quartz fiber filters (PLE, 82-110%; USE, 67-97%) were obtained. Recoveries obtained from real PM(10) samples were also high (76-107%), and no significant matrix effects (ME) on the ionization process (enhancement or suppression) were found (ME, 89-123%). Method limits of quantification (S/N = 10) were in the range between 2 and 336 pg/m(3). This method was used to analyze real PM samples collected at several urban and rural locations in the Antwerp area. For the first time, concentrations for Belgium are provided. Concentrations of individual oxy-PAHs are in the lower pictograms per cubic meter to 6 ng/m(3) range. High concentration differences between individual compounds are found as exemplified by the 75th percentile of the phenanthrene-9,10-dione and benzo[de]anthracene-7-one concentrations being a factor of 4 to 22 higher compared with the other target oxy-PAHs.

A membrane bioreactor for the removal of dimethyl sulphide and toluene from waste air.

In biotrickling filters, mass transfer of hydrophobic compounds is the limiting factor. Biofilters are static systems, and so control and regulation of operational parameters such as pH and nutrient supply can be a problem. In membrane bioreactors, these drawbacks can be avoided. The hydrophobic membrane separates the waste air from the aqueous phase, thus avoiding mass-transfer limitation, while pH and nutrient supply can be directly controlled. In this contribution, an overview will be given of results obtained during a four-year project. First, the physical chemical characteristics (solubility, permeability, diffusivity) and microbial adhesion of different membranes were tested. This led to the selection of a composite membrane consisting of a porous polyvinylidenefluoride (PVDF) support layer coated with a thin (1 or 2.5 microm) dense polydimethylsiloxane (PDMS) top layer. This membrane was mounted into a module provided with four parallel rectangular channels for gas flow (in contact with the porous layer) and nutrient solution (in contact with the dense layer) respectively. After inoculation, a biofilm developed on the dense layer. Experiments were performed with dimethyl sulphide and toluene as target VOCs. Operational characteristics such as elimination capacity as a function of the volumetric load and residence time, effect of nutrient supply, long-term performance) were determined. Mass transfer was studied by measuring concentration profiles along the channels of the module in different conditions.

Environmental engineering education at Ghent University, Flanders (Belgium).

Since the 1980s, environmental engineering education has been a rapidly growing discipline in many universities. This paper discusses the history, the current status and the near future of environmental engineering education at Ghent University. This university, with about 50% of the Flemish university environmental engineering students, can be considered as representative for the situation in Flanders, Belgium. In contrast to many other universities, environmental engineering education at Ghent University does not have its historical roots in civil engineering, but has been developed from the curricula organized by the former Faculty of Agricultural Sciences. As part of a reorganisation of the education and research activities at this faculty, a curriculum leading to the degree of "bio-engineer in environmental technology" was established in 1991. This curriculum covers a 5-year study and is constructed around 8 main components. Exchange of students with other European universities, e.g. within the Socrates framework, has become a prominent aspect of student life and education. This paper also briefly describes the employment opportunities of graduated bio-engineers in environmental technology. Finally, the current implementation of the bachelor's-master's structure, leading to a "master of science in environmental technology" degree is summarized.

Degradation of isobutyraldehyde and its intermediates in a compost biofilter.

This study demonstrates that at low to medium isobutyraldehyde loading rates (191 gm(-3) d(-1)-933 gm(-3) d(-1)), 100% removal efficiencies can be obtained in a compost biofilter. However, increasing the loading rate to 1500-1900 gm(-3) d(-1) caused a drop in degradation efficiency, a pH decrease and production of isobutyl alcohol and isobutyric acid. Additional batch and continuous experiments were performed to study the effect of pH and compost moisture content on the biofiltration of isobutyraldehyde, isobutyl alcohol and isobutyric acid. It was shown that the degradation rate of the three compounds decreased in the order isobutyraldehyde > isobutyl alcohol >> isobutyric acid, with no significant degradation for isobutyric acid. The isobutyl alcohol degradation rate was negatively influenced by the presence of isobutyraldehyde, while isobutyraldehyde degradation was not affected by the presence of either of the two compounds. A pH of 5.2 apparently inhibited the isobutyl alcohol degradation and lowered the isobutyraldehyde degradation rate, although adaptation of the microorganisms to low pH seemed to occur in the biofilters. Moisture content had a smaller effect on the degradation rates, although continuous experiments showed that a very high water content (55% compared to 40%) negatively affected isobutyraldehyde elimination increasingly during the course of the experiment. As a conclusion, it appears that at high loads of isobutyraldehyde, isobutyric acid is accumulated in the biofilter, resulting in a drop of pH. Consequently, isobutyraldehyde removal efficiency decreases and both isobutyl alcohol and isobutyric acid are measured in the effluent. It is suggested that next to moisture control, a pH buffer is necessary to remove high loads of isobutyraldehyde and to avoid persistence of intermediates in the effluent.

Optimalisation of magnesium ammonium phosphate precipitation and its applicability to the removal of ammonium.

Among the physico-chemical abatement technologies, mainly acid scrubbers have been used to control NH3-emission. The disadvantage of this technique is that it yields waste water, highly concentrated in ammonia. In this report, the applicability of the magnesium ammonium phosphate (MAP) process to regenerate the liquid phase, produced by scrubbing NH3-loaded waste gases, was investigated. In the MAP process, ammonium is precipitated as magnesium ammonium phosphate, which can be used as a slow release fertilizer. The influence of a number of parameters, e.g. pH, kinetics, molar ratio NH(+)4/Mg2+/PO(3-)4 on the efficiency of the formation of MAP and on the ammonium removal efficiency was investigated. In this way, optimal conditions were determined for the precipitation reaction. Next to this, interference caused by other precipitation reactions was studied. At aqueous NH(+)4-concentrations of about 600 mg l(-1), ammonium removal efficiencies of 97% could be obtained at a molar ratio NH(+)4/Mg2+/PO(3-)4 of 1/1.5/1.5. To obtain this result, the pH was continuously adjusted to a value of 9 during the reaction. According to this study, it is obvious that the MAP-precipitation technology offers opportunities for ammonium removal from scrubbing liquids. The practical applicability of the MAP-process in waste gas treatment systems, however, should be the subject for further investigations.