FG Biotechnologie der Wasseraufbereitung
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- FG Biotechnologie der Wasseraufbereitung (149)
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The UV treatment of 6:2 FTAB involves the mitigation of this persistent chemical by the impact of ultraviolet radiation, which is known for its resistance to environmental breakdown. UV treatment of PFOA and/or 6:2 FTAB, and the role of responsible species and their mechanism have been presented. Our investigation focused on the degradation of perfluorooctanoic acid (PFOA) and 6:2 fluorotelomer sulfonamide alkyl betaine (6:2 FTAB, Capstone B), using UV photolysis under various pH conditions. Initially, we used PFOA as a reference, finding a 90% decomposition after 360 min at the original (unadjusted) pH 5.6, with a decomposition rate constant of (1.08 ± 0.30) × 10−4 sec−1 and a half-life of 107 ± 2 min. At pH 4 and 7, degradation averaged 85% and 80%, respectively, while at pH 10, it reduced to 57%. For 6:2 FTAB at its natural pH 6.5, almost complete decomposition occurred. The primary UV transformation product was identified as 6:2 fluorotelomer sulfonic acid (6:2 FTSA), occasionally accompanied by shorter-chain perfluoroalkyl acids (PFAAs) including PFHpA, PFHxA, and PFPeA. Interestingly, the overall decomposition percentages were unaffected by pH for 6:2 FTAB, though pH influenced rate constants and half-lives. In PFOA degradation, direct photolysis and reaction with hydrated electrons were presumed mechanisms, excluding the involvement of hydroxyl radicals. The role of superoxide radicals remains uncertain. For 6:2 FTAB, both direct and indirect photolysis were observed, with potential involvement of hydroxyl, superoxide radicals, and/or other reactive oxygen species (ROS). Clarification is needed regarding the role of 𝑒−𝑎𝑞 in the degradation of 6:2 FTAB.
Aminophosphonates, like glyphosate (GS) or metal chelators such as ethylenediaminetetra(methylenephosphonic acid) (EDTMP), are released on a large scale worldwide. Here, we have characterized a bacterial strain capable of degrading synthetic aminophosphonates. The strain was isolated from LC/MS standard solution. Genome sequencing indicated that the strain belongs to the genus Ochrobactrum. Whole-genome classification using pyANI software to compute a pairwise ANI and other metrics between Brucella assemblies and Ochrobactrum contigs revealed that the bacterial strain is designated as Ochrobactrum sp. BTU1. Degradation batch tests with Ochrobactrum sp. BTU1 and the selected aminophosphonates GS, EDTMP, aminomethylphosphonic acid (AMPA), iminodi(methylene-phosphonic) (IDMP) and ethylaminobis(methylenephosphonic) acid (EABMP) showed that the strain can use all phosphonates as sole phosphorus source during phosphorus starvation. The highest growth rate was achieved with AMPA, while EDTMP and GS were least supportive for growth. Proteome analysis revealed that GS degradation is promoted by C-P lyase via the sarcosine pathway, i.e., initial cleavage at the C-P bond. We also identified C-P lyase to be responsible for degradation of EDTMP, EABMP, IDMP and AMPA. However, the identification of the metabolite ethylenediaminetri(methylenephosphonic acid) via LC/MS analysis in the test medium during EDTMP degradation indicates a different initial cleavage step as compared to GS. For EDTMP, it is evident that the initial cleavage occurs at the C-N bond. The detection of different key enzymes at regulated levels, form the bacterial proteoms during EDTMP exposure, further supports this finding.
The existence of large deposit of crude oil in the Nigerian Niger-Delta accords the region a strategic position in the country’s economy. However, activities associated with the oil and gas industry have resulted in extensive and in some instances indelible damages on the ecosystems. The destructive effect of hydrocarbon on bionetwork necessitated this study that aimed at evaluating the potential of adopting microbial and biosurfactant technology as tools for bioremediation. The research involved gas chromatography monitoring of hydrocarbon degradation in polluted soil, microbiological/molecular identification of hydrocarbon degraders and the evaluation of biosurfactant production by indigenous bacteria. The performance of four treatments involving; co-treatment with mixed bacterial consortium and close-to-nature surfactants (Bioversal QF and Bioversal UK), treatments with mixed bacteria culture, single bacteria culture and treatment with close-to-nature surfactants only were evaluated for the mineralization of hydrocarbons contained in 500g of 2% crude oil contaminated soil supplemented with Na2HPO4*2H2O, KH2PO4 and NH4Cl as nutrient sources over a period of 20 weeks. Six indigenous biosurfactant producing and/or hydrocarbon degrading bacteria strains were isolated namely: Pseudomonas aeruginosa, Bacillus sp, Achromobacter sp, Stenotrophonas sp, Lysinibacillus sp. and Delftia sp. Molecular characterization of sequenced polymerase chain reaction products of these cultured bacteria using Nucleotide Basic Local Alignment Search Tool confirmed close relationships ranging from 98.83% to 100% with those on the NCBI databank. Co-treatment with mixed bacteria culture and Bioversal UK/Bioversal QF yielded synergetic impact that enhanced 73.35% and 71.52% degradation of total petroleum hydrocarbon respectively. Treatments with close-to-nature surfactants and with mix bacterial culture recorded 53.61% and 54.58%. The use of single bacteria strains resulted in the mineralization of 46% - 62.26% total petroleum hydrocarbon while their use as a consortium yielded 54%. Liquid chromatography-Mass spectrometry assessment of extracellular polymeric substances produced by cultured bacteria strains indicated the presence of rhamnolipids (L-rhamnosyl-3-hydroxydecanoyl-3-hydroxydecanoic acid with a mass of 504.654 Da) and lipopeptides (2-(Hydroxymethyl) phenyl 6-O-palmitoyl-β-D-glucopyranoside with a mass of 524.687 Da). Extracellular polymeric substances produced yielded emulsion index ranging from 70.70% to 75% and 39% to 65% with crude oil and heptane respectively. EPS yields ranging from 1.34 g/ml to 1.5 g/ml were recorded.zeige weniger
In the Garu-Tempane area and Tamne River basin of north-eastern Ghana, granitic aquifers supply nearly 80% of annually abstracted groundwater. Rapid and diffuse recharge enters the fractured and weathered Tamnean Plutonic Suite aquifers mainly granitoid, which are the dominant rock types in the study area. However, a greater challenge to the water supply in the area is posed by global climatic changes and overexploitation due to population growth. The semi-arid nature of the area together with the factors mentioned earlier has caused water scarcity, particularly in the dry season and these have affected the livelihoods of the farmers who depend mostly on the groundwater for irrigation and domestic purposes. A promising way to balance water resources in the region is using engineering technology such as managed aquifer recharge (MAR). MAR augments water levels in water-scarce areas and represents a key tool in water supply management.
For this reason, a comprehensive hydrogeological characterization involving the hydrochemistry of the groundwater, groundwater recharge process and residence time using multi-environmental tracers, and a numerical groundwater flow model was developed.
Based on the hydrochemistry results, the water quality index showed that the groundwater is very suitable for drinking. However, about 10.5 % out of the 38 groundwater samples had elevated nitrate concentrations exceeding the permissible WHO drinking water limit. These are mainly agricultural areas, which might have influenced the elevated nitrate concentrations.
Groundwater age dating using sulphur hexafluoride (SF6) and chlorofluorocarbons (CFCs) was used to date shallow groundwater in Ghana for the first time. The results proved that the mean residence time of groundwater was around 30 years, an indication of young groundwater and rapid groundwater renewability. The findings also showed different groundwater ages implying diffused flow systems occurring in the fractured granitic aquifer.
Investigation of the groundwater recharge using stable isotopes of deuterium and oxygen-18 revealed that the main source of groundwater recharge is of meteoric origin. There were little or no contributions from the stream and ponds as they were subjected to evaporative fractionation during the dry season. The White Volta River samples and samples from two big rivers were depleted in heavy isotopes, which suggested a hydraulic connection between them and the groundwater.
The numerical groundwater flow model was used to assess the feasibility of MAR and determine the maximum recharge and abstraction rates. The results showed that the aquifer had enough storage to accommodate enough volumes of floodwater without causing groundwater mounding. This shows that MAR is feasible in augmenting the water levels in the area when irrigation and domestic withdrawals are regulated.
Determination of biodegradation of synthetic phosphonates such as aminotris(methylenephosphonic acid) (ATMP), ethylenediamine tetra(methylenephosphonic acid) (EDTMP), or diethylenetriamine penta(methylenephosphonic acid) (DTPMP) is a great challenge. Commonly, ready biodegradability of organic substances is
assessed by OECD 301 standard tests. However, due to the chemical imbalance of carbon to phosphorus synthetic phosphonates do not promote microbial growth and, thus, limiting its biodegradation. Therefore, standard OECD test methods are not always reliable to predict the real biodegradability of phosphonates. In the presented study, we report the development of a standardized batch system suitable to synthetic phosphonates such as ATMP, EDTMP, DTPMP and others. The novel standard batch test is applicable with pure
strains, activated sludge from different wastewater treatment plants (i.e., municipal and industrial), and with tap water as inoculum. We optimized the required calcium and magnesium exposure levels as well as the amount of the start inoculum biomass. We demonstrated that our test also allows to determine several parameters including
ortho-phosphate (o-PO43 ), total phosphorus (TP), ammonium (NH4+) and total organic carbon (TOC). In addition, also LC/MS analyses of cell-free medium is applicable for determining the mother compounds and metabolites. We applied our optimized standardized batch with selected phosphonates and evidenced that the chemical structure has a major influence of the microbial growth rates. Thus, our novel batch test overcomes drawbacks of the OECD 301 test series for determination of easy biodegradability for stoichiometric imbalanced organic
compounds such as phosphonates.
The membrane bioreactor (MBR) is an efficient technology for the treatment of municipal and industrial wastewater for the last two decades. It is a single stage process with smaller footprints and a higher removal efficiency of organic compounds compared with the conventional activated sludge process. However, the major drawback of the MBR is membrane biofouling which decreases the life span of the membrane and automatically increases the operational cost. This review is exploring different anti-biofouling techniques of the state-of-the-art, i.e., quorum quenching (QQ) and model-based approaches. The former is a relatively recent strategy used to mitigate biofouling. It disrupts the cell-to-cell communication of bacteria responsible for biofouling in the sludge. For example, the two strains of bacteria Rhodococcus sp. BH4 and Pseudomonas putida are very effective in the disruption of quorum sensing (QS). Thus, they are recognized as useful QQ bacteria. Furthermore, the model-based anti-fouling strategies are also very promising in preventing biofouling at very early stages of initialization. Nevertheless, biofouling is an extremely complex phenomenon and the influence of various parameters whether physical or biological on its development is not completely understood. Advancing digital technologies, combined with novel Big Data analytics and optimization techniques offer great opportunities for creating intelligent systems that can effectively address the challenges of MBR biofouling.
Sunlight Degradation of the Aminophosphonate Diethylenetriamine Penta-(Methylenephosphonic Acid)
(2022)
Aminophosphonate diethylenetriamine penta(methylenephosphonic acid) (DTPMP) is a scale inhibitor commonly used in several industries. DTPMP is suspected to cause anthropogenic pollution through discharge into the aquatic environment. DTPMP is assumed to be degraded by
sunlight radiation. We recently predicted a preliminary degradation pathway of DTPMP applyingUV treatment. Currently, we have not yet evidenced that DTPMP shows the same degradation pattern with natural sunlight. One major reason leads to the fact that the light spectrum emitted by UV lamps does not completely represent the natural sunlight spectrum, and the emitted UVB and UVA irradiation flux is much higher than for solar light. For that reason, the degradation pattern and kinetics might be different between artificial UV treatment and natural sunlight treatment. Here, we investigated whether DTPMP is degradable under natural sunlight radiation, and whether
the degradation mechanisms determined through UV treatment are transferable to sunlight. We investigated five different treatment conditions, i.e., DTPMP degradation in direct or diffuse sunlight,
in diffuse sunlight with addition of Ca2+ or Mg2+, and in diffuse sunlight with local TW. Our experiment was carried out from March 2021 to October 2021. We performed LC/MS analyses and measured the release of o-PO4 3 . DTPMP was degraded with all five treatment conditions. The fastest DTPMP degradation occurred in direct and diffuse sunlight without addition of bivalent cations. The addition of Ca2+ and Mg2+ resulted in inhibited degradation. Similar effects occurred for sunlight treatment with local TW. We evidenced different degradation mechanisms for DTPMP depending on the presence of alkaline earth metals as we previously proposed for UV-treated DTPMP. However,
both degradation mechanisms of DTPMP belong to the same degradation pathway determined with UV treatment. Therefore, we conclude that DTPMP undergoes a similar degradation pathway in sunlight as compared to UV light.
Today, nanotechnologies (NTs) are well established in both private households and commercial markets. NTs are fully accepted in several sectors, such as medicine and pharmacy, and in industries, such as chemistry, electricity, food production, military, and other commercial branches, due to their unique properties. With regard to the growing demands for environmental resources caused by the still-growing global population, the application of NTs is an extremely important new branch in the environmental sector, delivering several advantages. Our review provides a comprehensive overview of the current developments in environmental remediation, wastewater treatment, drinking water treatment, and agriculture. More specifically, in the section on environmental remediation, we review the application of NTs towards enhanced reductive dechlorination, removal of heavy metals and remediation of oil spills. In the section on wastewater treatment, we highlight developments in the adsorption of heavy metals and persistent substances, advanced photocatalytic
degradation of common wastewater pollutants, and improvements in membrane filtration processes.
In the section on drinking water treatment, we discuss applications for the enhanced disinfection of pathogens, removal of heavy metals, point-of-use treatments, and the removal of organic matter. In the final section, on agriculture, we provide an overview of precision farming and the current state of the art concerning nanofertilisers, nanopesticides, nanoherbicides, and nano(bio)sensors.
Intrinsisch antimikrobielle Polyurethane : Synthesekonzepte - neue Strukturen - Charakterisierung
(2020)
Roundup® is the brand name for herbicide solutions containing glyphosate, which specifically inhibits the 5-enolpyruvyl-shikimate-3-phosphate (EPSP) synthase of the shikimate pathway. The inhibition of the EPSP synthase causes plant death because EPSP is required for biosynthesis of aromatic amino acids. Glyphosate also inhibits the growth of archaea, bacteria, Apicomplexa, algae and fungi possessing an EPSP synthase. Here, we have characterized two glyphosate-resistant bacteria from a Roundup solution. Taxonomic classification revealed that the isolates 1CH1 and 2CH1 are Burkholderia anthina and Burkholderia cenocepacia strains respectively. Both isolates cannot utilize glyphosate as a source of phosphorus and synthesize glyphosate-sensitive EPSP synthase variants. Burkholderia. anthina 1CH1 and B. cenocepacia 2CH1 tolerate high levels of glyphosate because the herbicide is not taken up by the bacteria. Previously, it has been observed that the exposure of soil bacteria to herbicides like glyphosate promotes the development of antibiotic resistances. Antibiotic sensitivity testing revealed that the only the B. cenocepacia 2CH1 isolate showed increased resistance to a variety of antibiotics. Thus, the adaptation of B. anthina 1CH1 and B. cenocepacia 2CH1 to glyphosate did not generally increase the antibiotic resistance of both bacteria. However, our study confirms the genomic adaptability of bacteria belonging to the genus Burkholderia.
The reuse of treated wastewater for irrigation is of increasing importance. The Ecosave farming project developed a new photocatalytic electrodialysis process for desalination and hygienization. However, membrane scaling significantly reduces filtration efficiency. This study investigated biofilm development on anion and cation exchange membranes at a wide pH range in pre-treated wastewater. Epifluorescence microscopic quantification of the biofilm by cell counts and surface coverage together with 16S rDNA gene copy numbers showed stronger biofilm development on the anion exchange membrane (AEM) compared with the cation exchange membrane (CEM) with up to 105 cells mm−2 and 20% surface coverage after three weeks. As the AEM biofilm developed best in neutral and a slightly alkaline pH, the CEM was colonized preferably at alkaline conditions. Extreme pH conditions strongly inhibited biofilm growth, which might help to minimize the maintenance effort by creating those conditions during the operation of the dialysis cell itself.
Glyphosate is a nonselective herbicide that kills weeds and other plants competing with crops. Glyphosate specifically inhibits the 5-enolpyruvyl-shikimate-3-phosphate (EPSP) synthase, thereby depleting the cell of EPSP serving as a precursor for biosynthesis of aromatic amino acids. Glyphosate is considered to be toxicologically safe for animals and humans. Therefore, it became the most-important herbicide in agriculture. However, its intensive application in agriculture is a serious environmental issue because it may negatively affect the biodiversity. A few years after the discovery of the mode of action of glyphosate, it has been observed that bacteria evolve glyphosate resistance by acquiring mutations in the EPSP synthase gene, rendering the encoded enzyme less sensitive to the herbicide. The identification of glyphosate-resistant EPSP synthase variants paved the way for engineering crops tolerating increased amounts of the herbicide. This review intends to summarize the molecular mechanisms underlying glyphosate resistance in bacteria. Bacteria can evolve glyphosate resistance by (i) reducing glyphosate sensitivity or elevating production of the EPSP synthase, by (ii) degrading or (iii) detoxifying glyphosate and by (iv) decreasing the uptake or increasing the export of the herbicide. The variety of glyphosate resistance mechanisms illustrates the adaptability of bacteria to anthropogenic substances due to genomic alterations.
The cultivation based characterization of microbial communities and the quantification of certain functional bacterial groups is still an essential part of microbiology and microbial ecology. For plate count methods meanwhile low strength media are recommended, since they cover a broader range of different species and result in higher counts compared to established high strength media. For liquid media, as they are used for most probable number (MPN) quantifications, comparisons between high and low strength media are rare. In this study we compare the performance of different high and low strength media for the MPN quantification of nitrate reducing and denitrifying bacteria in two different fresh water environments. We also calculated the cell specific turnover rates of several denitrifying cultures previously enriched in high and low strength media from three different fresh water environments and a waste water treatment plant. For fresh water samples, our results indicate that high strength media detect higher MPN of denitrifying bacteria and in equal MPN of nitrate reducing bacteria compared to low strength media, which is in contrary to plate count techniques. For sediment samples, high and low strength media performed equal. The cell specific turnover rate was independent from the enrichment media and the media of the performance test. The cause of the lower denitrifyer MPN in low strength media remains, however, unclear. The results are important for further MPN quantifications of bacteria in nutrient poor environments and for calculations of nitrogen turnover rates by kinetical models using the number of metabolic active cells as one parameter.
Aminophosphonates such as aminotris(methylenephosphonic acid) (ATMP) are common constituents of antiscalants. In nanofiltration (NF) and reverse osmosis (RO) processes, ATMP prevents inorganic scaling leading to more stable membrane performance. So far, little attention has been paid to the possible permeation of aminophosphonates through NF and RO membranes. We have investigated the permeability of these membrane types for ATMP and its potential metabolites iminodi(methylenephosphonic acid) (IDMP) and amino(methylenephosphonic acid) (AMPA) with two different NF membranes (TS40 and TS80) and one RO membrane (ACM2) and three different water compositions (ultra-pure water, synthetic tap water and local tap water). We found traces of
phosphonates in all investigated permeates. The highest phosphonate rejection occurred with local tap water for all three membranes investigated. Filtration experiments with a technical antiscalant
formulation containing ATMP indicated similar trends of phosphonate permeability through all three membranes. We assume that the separation mechanisms of the membranes are the results of a very
complex relationship between physico-chemical properties such as Donnan exclusion, feed pH, feed ionic strength and feed concentration, as well as solute–solute interactions.
Minimising matrix effects through high sample purity is of major importance for LC/MS analysis. Here we provide supplementary data and protocols related to the article “Rapid sample clean-up procedure of aminophosphonates for LC/MS analysis”(revised article submitted to Talanta) [1] . It is demonstrated that the tested phosphonates iminodi(methylenephosphonic acid) (IDMP), hydroxyethelidene(diphosphonic acid) (HEDP), aminotris(methylenephosphonic acid) (ATMP), ethylenediaminetetra(methyloenephosphonic acid) (EDTMP) and diethylenetriaminepenta(methylenephosphonic acid) (DTPMP) dissolved in tap water are not detectable by LC/MS without sample clean-up. Only the smallest aminophosphonate amino(methylenephosphonic acid) (AMPA) was detectable but the recovery is decreased drastically. The optimised sample clean-up with cation exchange resin (CER) Dowex 50WX8 is described in detail and illustrated. The protocol is provided. The influence of the incubation time, addition of different ammonium acetate concentrations, different samples pHs and different water qualities is demonstrated and preferred clean- up conditions are recommended. Calibration results of all tested aminophosphonates are validated regarding limit of detection, limit of quantification, lower limit of quantification, absolute and relative process standard deviation. A final recommendation for the best clean-up condition for all six tested aminophosphonates is provided.
Aminophosphonates such as hexamethylenediaminetreta(methylene phosphonic acid) (HDTMP) are categorised as persistent substances. They are commonly used as scale inhibitors in cooling water systems and desalination processes. After utilisation, they are often discharged into aquatic environment without pre-treatment. Advanced oxidation processes (AOP) are promising pre-treatments for industrial wastewater treatments. We investigated the photodegradation of HDTMP with or without addition of
manganese (Mn2þ) and/or H2O2. Similar to results of our former photodegradation studies, we found that HDTMP also undergoes conversion with or without additives during the ultra violet (UV) irradiation. The reaction rate was most affected by the addition of H2O2, i.e. the HDTMP degradation was accelerated
by a factor 3.85 compared with UV treatment without additives. The addition of Mn2þ accelerated the degradation of HDTMP only by a factor 1.53 compared with the UV treatment without additives. The combined addition of Mn2þ and H2O2 accelerated the HDTMP degradation by a factor 2.81. Interestingly, the initial cleavage is not initiated as expected at the CeN bond but at the CeP bond of the methyl carbon and the phosphorus of the methylenephosphonic acid group of HDTMP. This initial
cleavage was independent whether the UV treatment was performed with or without additives. Therefore, we conclude that the degradation mechanism is similar independent of the four tested
treatment conditions. We identified amino(methylenephosphonic acid) AMPA, dimethylamino(methylenephosphonic acid) DAMP and iminodi(methylenephosphonic acid) IDMP as the major breakdown
products by performing LC/MS analyses. The major mineralisation products were ortho-phosphate, ammonium and carbon dioxide. The mass balances of unknown breakdown products
Photodegradation of aminophosphonates such as ethylenediaminetetra(methylenephosphonic acid) (EDTMP) is recently assumed being the major degradation pathway in aquatic environments. Several photolysis studies were reported about EDTMP and possible breakdown products occurring in natural ecosystems. Reliable prediction of environmental photolysis of parent compounds and possible release of breakdown products requires different
set-up conditions and varying the parameters influencing the photodegradation. We studied the influence of three different system configurations during UV degradation of EDTMP. These three configurations differed either in geometry and/or treated sample volumes. System 1 was equipped with a direct cooling jacket at the UV lamp. System 2 had the geometry of system 1 but there was no usage of a direct cooling jacket. System 3 was a gas-tight system with a larger sample volume. Using the chemical actinometer potassium ferrioxalate, we determined the highest photon flux for system 3 followed by system 2 and 1. In addition, we performed scavenger experiments with methanol and ascorbic acid in order to prove the dominating radical species. In system 1, the addition of methanol showed almost no effect while the ascorbic acid resulted in a reduction of 57.1% orthophosphate released. Therefore we conclude that in system 1 the radical-drive degradation of EDTMP is mainly
based on superoxide radicals. In system 2 and 3 both radical species, i.e., hydroxyl radicals and superoxide radicals, contribute to the photodegradation of EDTMP. We determined different half-lives for EDTMP for the three different systems configurations. For system 1, the estimated half-life achieved was 14.09 ± 0.15 min. For
system 2 and 3, the half-lives were almost similar and averaged 4.75 ± 0.05 min and 5.02 ± 0.20 min, respectively. Contrary to our assumption to also find the highest degradation rate for system 3, we found the highest degradation rate for system configuration 2 as a result of the differences in the construction and geometry
of the three systems. Our findings lead us to recommend the three system configuration for different research purposes. Thus, we recommend system 1 for detailed studies on the degradation pathway of the parent compound and their breakdown products. System 2 is recommended as a suitable configuration for kinetic studies of the parent compound. And finally, we recommend the system configuration 3 for complete mass balances. The gas-tight system allows determining all soluble and gaseous compounds.
Aminophosphonate sind synthetisch hergestellte Komplexbildner, die kovalente C-P Bindungen aufweisen. Durch zusätzlich eingefügte Aminogruppen (NH2) komplexieren Amino-phosphonate besonders gut Metallionen, weshalb sie in einem sehr breiten Anwendungsspektum zum Einsatz kommen. So werden Phosphonate vielseitig als Haushalts- und Industriereiniger, aber auch als Komponenten von Kosmetika und in der Medizin verwendet. Des weiteren werden sie zur Kühlwasserkonditionierung, Stabilisierung von Peroxiden oder Bleichbädern und als Korrosionsinhibiter eingesetzt. Entsprechend der vielseitigen Anwendungsgebiete lag bereits in den früher 90igern des vergangenen Jahrhunderts die Gesamtproduktion an Phosphonaten in Europa bei über 11.000 Tonnen pro Jahr (Jaworska et al., 2002). Weltweit zeigen die Nutzung und der damit verbundene Bedarf an Phosphonaten einen immer weiter steigenden Trend. Dem entgegen steht der noch immer wenig untersuchte Verbleib und das chemische Verhalten von Phosphonaten in der Umwelt.
Die gegenwärtig technisch eingesetzten Phosphonate ähneln in ihrer Struktur den bekannteren Aminocarboxylaten wie dem EDTA und NTA. Chemisch synthetisierte Phosphonate sind nur schwer biologisch abbaubar, weshalb zu einer kontinuierlichen Anreicherung in der aquatischen Umwelt kommen kann (Jaworska et al., 2002). Dies liegt unter anderem auch daran, dass Phosphonate als Phosphatersatz in großen Mengen in Waschmitteln enthalten sind und über das Abwasser in die Kläranlagen gelangen, wo sie nicht weiter biologisch abgebaut werden. Sie werden hauptsächlich durch Absorption an die Oberfläche vom Belebtschlamm aus den Abwasser entfernt. Nowack (2004) beschrieb die Toxizität von Phosphonaten in Kläranlagen als gering, verwies aber gleichzeitig darauf, dass aufgrund ihrer hohen Stabilität Phosphonate hemmend auf Proteasen und Syntheasen (Enzyme) von Mikroorganismen wirken.
Der photochemische und biologische Abbau von dem Phosphonat EDTMP wurde eingehend untersucht, um dessen Umweltverhalten besser abschätzen zu können. Ziel der Untersuchungen war es den Abbauprozess zu entschlüsseln als Grundlage für die langfristige Entwicklung umweltverträglicher Aminophosphonatstrukturen. Der photochemische Abbau von EDTMP und die Bildung von Metaboliten konnte mittels LC-MS und 31P-NMR bereits aufgeklärt werden. So zeigt sich das EDTMP bereits nach wenigen Minuten im UV-Licht zerfällt und nicht mehr nachgewiesen werden kann. Als Hauptprodukt konnte das Phosphonat IDMP identifiziert werden. Als weitere Abbauprodukte konnten die Phosphonate EABMP und AMPA identifiziert werden. In allen Versuchen konnte nach 300 min UV-Behandlung mindestens 75% des Endprodukts CO2 nachgewiesen werden. Weitere drei maßgebliche Abbauprodukte wurden mit Hilfe der LC-MS gefunden. Deren chemische Struktur konnte bisher jedoch noch nicht eindeutig beschrieben werden. Im Anschluss an die UV-Experimente wurde ein Versuch mit Sonnenlicht simuliert. Insgesamt verlief der EDTMP-Abbau im Sonnenlicht wesentlich langsamer. Auch hier konnten wieder dieselben Abbauprodukte IDMP, EABMP und AMPA identifiziert werden. Zusätzlich traten auch die drei noch nicht eindeutig identifizierten Metaboliten von EDTMP auf. Aus den gewonnen Daten kann somit geschlussfolgert werden, dass EDTMP unter Einwirkung von UV-Licht abbaubar ist. Die Annahme, dass EDTMP und dessen Abbauprodukte langfristig zur Schädigung des aquatischen Ökosystems führt, kann somit nicht bestätigt werden.
In weiteren Untersuchungen wurde der biologische Abbau von EDTMP und seiner photochemischen Abbauprodukten eingehend studiert. Für die Abbauversuche wurden die beiden Stämme Pseudomonas aeruginosa und Ochrobactrum sp. aus Boden isoliert. Es konnte gezeigt werden, dass sie 1mM EDTMP innerhalb von 35 Tagen zu mindestens 94% abbauen. Zusätzlich zum biologischen Abbau von EDTMP wurden auch die Verdopplungszeitung der beiden Stämme für EDTMP, IDMP, EABMP und AMAP ermittelt. Es zeigte sich, dass der Stamm P. aeruginosa für alle vier Phosphonate ein besseres wachstum zeigte als Ochrobactrum sp. Der Stamm P. aeruginosa erreichte für die Verstoffwechselung von EDTMP eine Verdopplungszeit von 10,1 Tagen, für IDMP 7,4 Tage, für EABMP 7,4 Tage und für AMPA 13,7 Tage. Der Stamm Ochrobactrum sp. erreichte für das Substrat EDTMP eine Verdopplungszeit von 11,8 Tagen, für IDMP 18,9 Tage, für EABMP 7,7 Tage und für AMPA 22,0 Tage. Offensichtlich war für beide Stämme der Abbau von AMPA der limitierende, aber nicht hemmende Schritt im biologischen Abbau. Somit kann geschlussfolgert werden, dass die Abbauprodukte der Photolyse auch biologisch abgebaut werden können. In weiteren Untersuchungen soll der biologische Abbau auf enzymatischer Ebene entschlüsselt werden. Die Identifizierung der Schüsselenzyme spielt hierbei eine wesentliche Rolle, um neuartige Phosphonatstrukturen herzuleiten, die auf der einen Seite ihre Funktionalität und Eigenschaften behalten, aber auf der anderen Seite eine erheblich verbesserte Bioverfügbarkeit aufweisen, so dass eine dauerhafte Akkumulation in der Umwelt und Folgebeeinträchtigungen minimiert ggf. ausgeschlossen werden können.
Aminophosphonates are commonly utilised for complexing bivalent ions such as calcium and magnesium. With regard to environmental samples, the analysis of these highly polar compounds is still challenging due to matrix effects and lacking analytical standard methods. We have recently developed a LC/MS method for common aminophosphonates without derivatisation. This LC/MS method delivers precise and accurate measurement for standard samples with very low concentration of cations disturbing the analysis. However, due to matrix effects this LC/MS method requires a sample clean-up being also applicable to natural water or wastewater samples.
We developed and optimised a sample clean-up procedure applying strong cation exchange resin Dowex 50WX8. This clean-up allows a single LC/MS analysis of hydroxyethelidene(diphosphonic acid) (HEDP), aminotris(methylenephosphonic acid) (ATMP), ethylenediaminetetra(methyloenephosphonic acid) (EDTMP), diethylenetriaminepenta(methylenephosphonic acid) (DTPMP) and its major intermediates amino(methylphosphonic acid) (AMPA) and iminodi(methylenephosphonic acid) (IDMP). We compared different test conditions with six aminophosphonates in either ultra pure water or tap water. The latter was used to simulate cation concentrations typical for natural waters.
To elute all aminophosphonate including AMPA, ammonium acetate addition was necessary. The addition of ammonium acetate was combinable with all tested aminophosphonates and provides high sample quality for LC/MS analysis. For acceptable recovery, the smallest aminophosphonate AMPA required the highest addition of ammonium acetate (1000 mg L-1) during the sample clean-up. Finally, the optimised clean-up procedure was successfully applied to identify and quantify phosphonates from an industrial wastewater sample. The sample clean-up procedure is simple, cheap, rapid and precise and can be further combined with solid phase extraction and more sensitive LC/MS methods.
Durch anthropogene Aktivität hat sich der Nährstoffeintrag in die Umwelt stark erhöht. Die Hauptquellen sind die Landwirtschaft, kommunales und industrielles Abwasser. Erhöhte Stickstofffrachten haben einen starken Einfluss auf den Stickstoffkreislauf. Das Überangebot an Stickstoff führt zu Eutrophierung in Gewässern und somit zu einem weniger diversen, instabileren Ökosystem. Die Stickstoffeliminierung aus Abwässern ist essentiell für den Schutz der Ökosysteme. Das etablierte System der Nitrifikation/Denitrifikation ist aufgrund des hohen Sauerstoffbedarfs sehr energie- und somit auch kostenintensiv. Der Anammox-Prozess (anaerobe Ammonium Oxidation) ist eine potentielle Alternative zur konventionellen Stickstoffelimination. Anammox-Bakterien nutzen Ammonium und Nitrit als Elektronenakzeptor. Durch Nutzung der partiellen Nitrifikation in Kombination mit Anammox (PN/A) kann bis zu 60 % der Belüftungsenergie eingespart werden. Trotz Erfolgen in der Teilstrombehandlung ist der Prozess noch nicht erfolgreich in der Hauptstrombehandlung eingesetzt worden. Die größten Herausforderungen sind die niedrigen Temperaturen, geringe Zulaufkonzentrationen und hohe Konzentrationen organischen Kohlenstoffs. Die vorliegende Arbeit konnte die Wirksamkeit von membranbelüfteten Biofilm Reaktoren unter Verwendung von synthetischem Abwasser bei niedrigen Temperaturen (18 - 8 °C) belegen. Die Innovation in diesem System ist die räumliche Trennung von nitrifizierenden Bakterien und Anammox Bakterien. Die regelmäßige mechanische Entfernung des Nitrifikanten-Biofilms ermöglichte einen langzeitstabilen Reaktorbetrieb. Diese Reaktorkonfiguration konnte auch erfolgreich für hochsaline Abwässer (5 -30 g NaCl*L-1) bei einer Reaktortemperatur von 30 °C und auch unter Zugabe von TOC (40-100 mg TOC*L-1) genutzt werden. Weiterhin wurden Untersuchungen zur Aktivität von salzadaptierter Anammox-Biomasse und nicht adaptierter Biomasse in einem Bereich von 0 bis 50 g NaCl*L-1 durchgeführt. Bei Konzentrationen unter 30 g NaCl*L-1 konnten keine signifikanten Unterschiede im Abbauverhalten festgestellt werden. Allerdings war adaptierte Biomasse bei höheren Salzkonzentrationen konkurrenzstärker. Außerdem wurden Langzeitlagerungsversuche durchgeführt. Die Lagerungsbedingungen variierten in der Lagerungstemperatur, im Redoxpuffer und der Nährstoffversorgung. Nach 106 Tagen bei 4 °C konnte die Anammox-Biomasse noch 91 % ihrer ursprünglichen Aktivität erhalten. Somit konnte eine einfache und kostengünstige Lagerungsmethode für Anammo-Bakterien entwickelt werden.
Calculation of hypolimnic denitrification in a dimictic freshwater lake during summer stratification
(2019)
Phosphonates comprise a very large group of organophosphonates including aminophosphonates. Their main chemical feature leads to complexation of earth alkaline metals and transition metals (under stoichiometric). Therefore they are very often applied as complexing agents of detergents, as compounds of industrial cleaning products, or as antiscalants in cooling water systems and desalination processes. The high consumption of phosphonates within the past two decades leads to an increased discharge into the aquatic environment, of which the environmental risk is still uncertain. To date, there are several analytical methods published to determine phosphonates from environmental samples. However, no standard method has been defined until now. Different treatment technologies to break down phosphonates have been studied extensively such as photochemical degradation, chemical degradation and other advanced oxidation processes. The results obtained from those studies gained our chemical understanding with respect to possible implementation of such pre-treatment approaches in wastewater treatment, cooling water treatment and desalination process. The biological degradation of phosphonates has been studied for more than forty years. It was demonstrated that microorganisms are capable to breakdown the C-P bond with at least three different degradation pathways.
Rapid urbanisation in Ghana has resulted in individuals expanding the cities for abodes without considerations of the negative externalities these may have on the environment. One of the major challenges with rapid urbanisation is the formation of urban slums associated with lack of basic sanitation facilities. This has led to recurrent outbreak of cholera and typhoid fever. The use of a single-stage solar-supported hyper-thermophilic anaerobic biogas digester for the treatment of black water has not been investigated, hence this study. The performance of three seeding sludge under three different hyper-thermophilic temperatures (60°C, 65°C and 70°C) were tested in batch tests. The three seeding sludge were sewage sludge, sludge from maize silage and cow manure. The results from the batch tests showed cow manure at 65°C as the preferred seeding sludge and optimal hyper-thermophilic temperature.
A 50 L single-stage laboratory-scale hyper-thermophilic continuous stirred tank reactor (HT-CSTR) was operated to treat only black water for 10 weeks using cow manure at 65°C as the seeding sludge and optimal hyper-thermophilic temperature. Afterwards, co-digestion of blended kitchen food waste and black water was also practised for 12 weeks. With a mean hydraulic retention time (HRT) of 23.3 days, a mean total COD removal of 86.3 % was achieved. The reactor had an average COD volumetric loading rate of 6.22 kgCOD/(m3.d) and remained uninhibited. It also had organic loading rate of 0.3 kgVS/(m3.d) and a degradation performance (R) of 5.43 kgCOD/(m3.d). Treatment of only black water produced biogas with less methane content of 34.9 % even though a stable pH of 6.9 was recorded both in the reactor and in the effluent. Co-digestion with kitchen food waste increased the percentage content of methane in the biogas by 77 % from 34.9 % to 61.8 %.
The effectiveness of the HT-CSTR to hygienise the effluent for agricultural purpose was assessed by spiking the reactor with 200 ml each of 2 x 109 CFU/ml Salmonella senftenbergensis and 8 x 108 CFU/ml Escherichia coli. The HT-CSTR was able to hygienise all bacteria of Salmonella senftenbergensis and E. coli. A simulation test confirmed that between 30 minutes and 1 hour, all the cells of Salmonella senftenbergensis and E. coli in the treatment system were killed at 65 °C. Eubacteria, Methanosarcina spp., Methanomicrobium spp. and Methanococcus spp. were identified in the seeding sludge at the hyper-thermophilic temperature of 65°C. The design, construction and performance of a pilot-scale reactor in Terterkessim slum in Elmina, Ghana was based on results from the laboratory-scale HT-CSTR. It achieved 97 % removal of influent total COD and could produce about 2.52 Nm³CH₄/(kgCOD.d) which could be burned for at least 8 hours. The effluent cannot be used for cultivation of leafy vegetables such as cabbage since it had some concentrations of pathogens like Salmonella spp. and E. coli but can be used for cotton crop.
An enrichment culture of Candidatus Brocadia fulgida was identified by three independent methods: analysis of autofluorescence using different microscope filter blocks and a fluorescence spectrometer, fluorescence in situ hybridization (FISH) with anammox-specific probes and partial sequencing of the 16S rDNA, hydrazine synthase hzsA and hydrazine oxidoreductase hzo. The filter block BV-2A (400–440, 470 LP, Nikon) was suitable for preliminary detection of Ca. B. fulgida. An excitation-emission matrix revealed three pairs of excitation-emission maxima: 288–330 nm, 288–478 nm and 417–478 nm. Several autofluorescent cell clusters could not be stained with DAPI or by FISH, suggesting empty but intact cells (ghost cells) or inhibited permeability. Successful staining of autofluorescent cells with the FISH probes Ban162 and Bfu613, even at higher formamide concentrations, suggested insufficient specificity of Ban162. Under certain conditions, Ca. B. fulgida lost its autofluorescence, which reduced the reliability of autofluorescence for identification and detection. Non-fluorescent Ca. Brocadia cells could not be stained with Ban162, but with Bfu613 at higher formamide concentrations, suggesting a dependency between both parameters. The phylogenetic analysis showed only good taxonomical clustering of the 16S rDNA and hzsA. In conclusion, careful consideration of autofluorescent characteristics is recommended when analysing and presenting FISH observations of Ca. B. fulgida to avoid misinterpretations and misidentifications.
Energieeffizientes Nährstoffsplitting von flüssigen Wirtschaftsdüngern mittels Membranfiltration
(2017)
The Anammox process is an efficient low energy alternative for the elimination of nitrogen from wastewater. The process is already in use for side stream applications. However, some industrial wastewaters, e.g. from textile industry are highly saline. This may be a limit for the application of the Anammox process. The aim of this study was to evaluate the effects of different NaCl concentrations on the efficiency of adapted and non-adapted Anammox biofilms. The tested NaCl concentrations ranged from 0 to 50 g NaCl*L⁻¹. Concentrations below 30 g NaCl*L⁻¹did not significantly result in different nitrogen removal rates between adapted and non-adapted bacteria. However, adapted bacteria were significantly more resilient to salt at higher concentrations (40 and 50g NaCl*L⁻¹). The IC50 for adapted and non-adapted Anammox bacteria were 19.99 and 20.30 g NaCl*L⁻¹, respectively. Whereas adapted biomass depletes the nitrogen in ratios of NO-₂/NH+₄ around 1.20 indicating a mainly Anammox-driven consumption of the nitrogen, the ratio increases to 2.21 at 40 g NaCl*L⁻¹ for non-adapted biomass. This indicates an increase of other processes like denitrification. At lower NaCL concentrations up to 10 g NaCl*L⁻¹, a stimulating effect of NaCl to the Anammox process has been observed.
DTPMP is predominantly utilized as scale inhibitor. We investigated the reaction rates and degradation mechanism of DTPMP with and without addition of Fe²⁺, Mg²⁺ and Ca²⁺ by performing LC/MS and ³¹P-NMR analyses. DTPMP undergoes conversion with and without addition of bivalent metal ions. The initial cleavage of DTPMP is initiated at the C-N bond leading to release of IDMP as its major breakdown product. The release of smaller quantities of EABMP and AMPA confirmed the nucleophilic attack on the DTPMP amines. Oxidation of Fe²⁺ to Fe³⁺ during the initial 30 min indicated an intramolecular electron transfer changing the electron density distribution at the nitrogen centre, which increased the radical attack during UV irradiation. Independent of the fact that Fe acted as catalyst and Mg²⁺ and Ca²⁺ acted as reactants, we found no significant differences in their degradation mechanisms. However, the reaction rates were strongly affected by the addition of the bivalent metal ions as Fe²⁺ accelerated most DTPMP degradation followed by Mg²⁺ and Ca²⁺. The UV treatment without metal ion addition was four times slower compared with Fe²⁺ addition. We conclude that in environments rich in ferrous iron and/or at reduced redox potential, photolysis of DTPMP will be catalysed by iron and will lead to accumulation of IDMP, EABMP and AMPA and several other none-quantifiable breakdown products.
Microbial dynamics and enzymatic activities of activated sludge processes are not completely understood yet. A better understanding about the biology is indispensable for further process
optimization. Since proteins play a key role as catalysts in sludge processes, a protocol for protein extraction and analysis by 2-D PAGE was established. It is based on phenol extraction of alkaline extracts and on a subsequent precipitation with ammonium sulphate. 2-D protein patterns obtained from different sludges collected from membrane bioreactors showed – besides common spots – significant differences. Selected proteins were identified with nano-
HPLC-ESI-MS/MS. All membrane biological reactor (MBR) sludge samples investigated in this study contained elastase 3A, which implies that this human serine protease is a significant constituent of municipal wastewater. Although the identification of proteins from
ammonia-oxidizing bacterium Nitrosomonas europaea was expected, the detection of a protein with homology to the marine bacterium Saprospira grandis in MBR1 was surprising.
The data presented in this article provide supporting information to the related research article “Comparison of ten different DNA extraction procedures with respect to their suitability for environmental samples” (revised manuscript submitted to J. Microbiol. Methods). In that article, we compared the suitability of ten selected DNA extraction methods based on DNA quality, purity, quantity and applicability to universal PCR. Here we provide the data on the specific DNA gel sample load, all unreported gel images of crude DNA and PCR results, and the complete cost analysis for all tested extraction procedures and in addition two commercial DNA extraction kits for soil and water.
The FISH (fluorescence in situ hybridization) method is widely used to identify various types of cells. In comparison to cultivation-dependent methods, identification of microbes by FISH is easier
and generally takes several hours. This paper presents a review of improvements to the FISH method, its advantages and disadvantages, as well as examples of applications. Particular consideration was
given to the efficiency of microbes identification in samples taken from sewerage. The effectiveness of the method was confirmed by the results obtained in samples from the membrane bioreactor (MBR).
DNA extraction for molecular biological applications usually requires target optimized extraction procedures depending on the origin of the samples. For environmental samples, a range of different procedures has been developed. We compared the applicability and efficiency of ten selected DNA extraction methods published in recent literature using four different environmental samples namely: activated sludge from a domestic wastewater treatment plant, river sediment, anaerobic digestion sludge and nitrifying enrichment culture. We assessed the suitability of the extraction procedures based on both DNA yield and quality. DNA quantification was performed by both ultra violet (UV) spectrophotometry and fluorescence spectrophotometry after staining with PicoGreen. In our study, DNA yields based on UV measurement were overestimated in most cases while DNA yields from fluorescence measurements correlated well with the sample load on agarose gels of crude DNA. The quality of the DNA extracts was determined by gel electrophoresis of crude DNA and PCR products from 16S rDNA with the universal primer set 27f/1525r. It was observed that gel electrophoresis of crude DNA was not always suitable to evaluate DNA integrity and purity since interfering background substances (e.g. humic substances) were not visible. Therefore, we strongly recommend examining the DNA quality of both crude DNA and 16S rDNA PCR products by gel electrophoresis when a new extraction method is established.
Summarizing, we found four out of ten extraction procedures being applicable to all tested samples without noticeable restrictions. The procedure G (according to the standard method 432_10401 of the Lower Saxony State Office for Consumer Protection and Food Safety) had the broadest application range over procedure J
(published by Wilson, 2001). These were followed by procedures F (Singka et al., 2012) and A (Bourrain et al., 1999). All four extraction procedures delivered reliable and reproducible crude DNA and PCR products. From an economical point of view, all procedures tested during this study were cheaper compared to commercial DNA extraction kits.
This study aims at investigating the abiotic degradation pathway of
ethylenediaminetetra(methylenephosphonic acid) (EDTMP) simulated applying UV
irradiation. The degradation of EDTMP and formation of degradation products was
determined using LC-MS and ³¹P-NMR. In the laboratory scale experiments, EDTMP was
degraded within 30 min and the degradation products, iminodi(methylenephosphonic
acid) (IDMP), ethylaminobis(methylenephosphonic acid) (EABMP), and amino-
(methylenephosphonic acid) (AMPA), were simultaneously released. IDMP was the
main degradation product of EDTMP. Therefore, we conclude that the initial cleavage of
EDTMP is a heterolytically driven process, which starts the degradation process at the
intramolecular C-N bond. In contrast, the main product of a possible homolytic C-C
cleavage of methylaminobis(methylenephosphonic acid) could not be confirmed with
either LC-MS or ³¹P-NMR. Additionally, there was no evidence for a primary attack on
the C-P bond. All identified degradation products of EDTMP have been mineralized to
carbon dioxide (CO₂). Three additional degradation products (M1, M2, and M3) have
been found using the ³¹P-NMR analysis but have not yet been quantified using LC-MS.
We assume that the unidentified degradation product M1 is related to m/z 312, M2
to m/z 341, and M3 to m/z 409. Thus we concluded that EDTMP undergoes photochemical
conversion to IDMP, the main degradation product. EABMP and AMPA also accumulate,
but in smaller amounts. All intermediates are further mineralized to CO₂.
The anammox process is a potential alternative to the conventional nitrogen removal from wastewater. However, due to large generation times of anammox bacteria, the start-up of treatment reactors may be impeded. An efficient storage technique can handle this drawback and may be also suitable for seasonally operated treatment plants like in touristic areas. In the current study, several storage techniques were investigated with respect to its suitability for the
preservation of the specific anammox activity after long-term storage. Storing conditions differed in terms of temperature, redox buffer and nutrient supplementation. The specific activity of immobilized anammox bacteria (Candidatus Kuenenia stuttgartiensis) was determined three times during a long-term preservation of 78 days and 106 days, respectively. The highest activity was ensured at a storing temperature of 4 WC, providing nitrate as redox buffer and a nutrient
supplement every 23 days. Thus, 91.4% of the initial anammox activity could be preserved after a storage of 106 days. Superiority of the presented treatment condition was confirmed by a calculated nitrate-ammonium consumption rate close to the optimal ratio of 1.32. This technique
provided an economical and simple method suitable for long-term storage of immobilized anammox biomass.
The precision of cell number quantification in environmental samples depends on the complexity of the sample and on the applied technique. We compared fluorescence microscopy after filtration, quantification of gene copies and the cultivation based most probable number technique for their precision. We further analyzed the effect of increasing complexity of the sample material on the precision of the different methods by using pure cultures of Pseudomonas aeruginosa, fresh water samples and sediment slurries with and without ultrasonic treatment for analyses. Microscopy reached the highest precision, which was similar between pure cultures and water samples, but lower for sediment samples due to a higher percentage of cells in clusters and flocks. The PCR based quantification was most precise for pure cultures. Water and sediment samples were similar but less precise, which might be caused by the applied DNA extraction techniques. MPN measurements were equally precise for pure cultures and water samples. For sediment slurries the precision was slightly lower. The applied ultrasonic treatment of the slurries dispersed the cell clusters and flocks, increased the precision of microscopical and MPN measurements and also increased the number of potential colony forming units. However, the culturable cell number decreased by half. For MPN quantification of viable cells in samples with a high proportion of clustered cells we therefore recommend an optimization of ultrasonic treatment and a confirmation by microscopy and cultivation to reach highest possible dispersion of the cells with a minimum of inactivation. As a result of these observations we suggest a correction factor for MPN measurements to consider the effect of sonication on complex samples. The results are most likely applicable to other complex samples such as soil or biofilms.
Unerwünschte Bewohner : Wasserasseln und andere Makroorganismen in Trinkwasserversorgungsnetzen
(2013)