FG Biotechnologie der Wasseraufbereitung
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Institute
This study describes the seasonal course of denitrifying and nitrate-reducing bacteria in a dimictic mesotrophic lake (Lake Scharmützelsee, Brandenburg, Germany) within a three-year period from 2011 to 2013. The bacterial cell numbers were quantified by the fluorescence microscopy, most probable number (MPN) and PCR-dependent quantification of the chromosomal 16S rDNA and of the nirS and nirK gene copy number. The highest seasonal differences (up to three orders of magnitudes) have been measured usingMPNin the epilimnion. This variation was not reflected by PCR-dependent approaches or direct microscopical enumeration. At adverse conditions (low temperature and/or low nitrate concentrations), the differences between MPN and gene copy numbers increased by up to five orders of magnitudes and decreased to one magnitude at favourable environmental conditions. These results can be explained best by an increasing ratio of viable but not cultivable (VBNC) cells or dead cells at impairing conditions. In the hypolimnion, the courses of MPN and nir gene copy numbers were similar. This can be explained by a higher feeding pressure and therefore smaller amounts of dormant cells. In the pelagial in general, the total cell numbers enumerated by either microscopical or molecular approaches were similar. In the sediment, more than 99% of the DNA was obviously not related to viable bacteria but was rather DNA in dead cells or adsorbed to particle surfaces.
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.
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 NaH₂PO*₄2HO₂, KHP₂O₄ and NHC₄l 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.
Determination of specific metabolic activities of anammox bacteria and their sensitivity to oxygen
(2013)
The discovery of Anammox bacteria has bridged our knowledge gap in the nitrogen cycle. This is because it explained the direct conversion of nitrite and ammonium to nitrogen gas in many reducing natural environments. However, it has been found that the presence of oxygen is an important determinat factor for certain biochemical processes and distribution of organisms in the environment. In this work, two methodological approaches were used to investigate the specific metabolic activities of Anammox bacteria and their sensitivity to oxygen using a mixed biomass culture. Two laboratory-scale bioreactors were maintained and the biomass in the reactors served as the inoculum for the investigations. The molecular characterization of the biomass was done using the Fluorescence in situ hybridization (FISH) technique. The specific Anammox activity (SAA) and important inhibition kinetic parameter characterization were estimated while monitoring activities of the biomass using several batch experiments.
The results of the biochemical characterization revealed that several microbial activities such as denitrification, nitrification, dissimilatory nitrate reduction to ammonium and Anammox processes were competing in the bioreactors. These were observed in the analysis of effluent recirculation of the feed solutions in the bioreactors, however, the Anammox process was predominant. An optimum sonication time top of eight minutes was established used to determine the average optical density to dry mass (OD: DM) ratio of 0.87 in the biomass. The FISH characterization estimated 60.4 % ± 14.6% (mean ± standard deviation) Anammox bacteria concentration in the biomass of Bioreactor 1. The Anammox bacteria were made up C. Kuenenia Stuttgartiensis (̴ 78%) and the remaining C. Brocadia Fulgida.
The maximum SAA of 0.025 mgNH4-N (TSSAnammox-1. d-1) and 5.4 mgNH4–N (1011 CellAnammox-1. d-1) for ammonium, and 0.04 mg N2-N (TSSAnammox-1. d-1) and 9.4 mgN2–N (1011 CellAnammox-1. d-1) for nitrogen gas were found in the biomass. While a binding affinity constant Ki = 0.07 mgO2 /l, maximum half inhibition concentration IC50 ̴ 0.2 mg O2 /l and KM = 50 mg/l were estimated for the inhibition kinetics of oxygen in the biomass. The low Ki value found in this study indicates that oxygen is an efficient inhibitor for Anammox activities and concentrations between 0.4 - 0.64 mg O2 /l can lead to complete inhibition of Anammox activity. However, this process is reversible. Finally, the implication of this inhibition kinetic results might be important in tracing the distribution of Anammox processes in natural environments where fixed nitrogen is present.
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.
Surface water has been used by mankind as the main source of water for domestic agriculture and industrial use in numerous countries around the world. However, water quality can be affected by mining activities which influences the natural environment, human health and aquatic ecosystem. The major pollutants in acid mine drainage are high amount of dissolved sulphate and heavy/toxic metals. Constructed wetlands are promising in situ water treatment methods which helps in the remediation process by stimulating microbial growth within the rhizospheric zone of the plants. The sulphate in constructed wetlands are removed by dissimilatory sulphate reduction in strict anaerobic conditions which helps in the removal of metals as metal sulphides.
The objective of this research is to investigate sulphate and metal removal pathways in constructed wetlands treating acid mine drainage. Therefore, several approaches were applied: (a) various types of model wetlands were used to investigate different removal processes (b) intensification of treatment processes with stimulation of the dissimilatory sulfate reduction in an autotrophic way by the use of hydrogen gas.
The application of hydrogen gas (as external electron donor) combined with common physico-chemical and biological parameters helped us to intensify the sulphate reduction process and removal of metals in constructed wetlands.
In the model wetland systems, the removal efficiencies varied with the types of constructed wetlands. The removal efficiencies of sulphate and metals were high in planted constructed wetlands as compared to unplanted constructed wetland. The combination of gravel bed and plants (Phragmites australis) resulted in the highest removal rate in horizontal subsurface flow constructed wetland. The metals mostly precipitated to the bottom of the constructed wetland as metal sulphides.
Though under carbon limited and anoxic conditions, a high mean removal efficiency of sulphate and heavy metals was observed in the experiments with HSSF CW so it is important to take into consideration the importance of electron donor. With hydrogen gas as electron donor the performance efficiency was increased by almost 12% for sulphate removal and almost 6% increase in aluminium removal efficiency.
In conclusion, this research exhibit that the combination of physico-chemical measurements along with hydrogen gas as an electron donor is an efficient tool for investigation of sulphate and metal removal processes in constructed wetlands. Such information is not only beneficial for understanding the processes taking place in these wastewater treatment facilities but also necessary for future technological improvement of constructed wetlands.
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.
Aim of this study
The aim of this research is to develop batch scale and continuous reactor systems to evaluate technical and practical feasibility of sequential hydrogen and methane from food waste by two step dark fermentation process.
Methodology
The effects of limiting factors, like pH, temperature, as well as inoculum sources and pretreatment methods on H₂ yields were studies in batch assays. In addition, the feasibility of sequencing producing H₂+CH₄ via two stage dark fermentation process was evaluated in lab-scale tests based on batch assay results. Three kinds of Acid producing reactor, like CSTR, semi-percolator, and ASBR had been tested for bioH₂ production and well inoculated ASBR methane was used for further degradation of volatile organic acids produced in these acid producing reactor which acts as by-products of bioH₂. Different limiting factors on fermentation process have been investigated in each reactor type for optimum energy recovery. Monodigestion of food waste for methane production was also studied and used as reference value for energy recovery from food waste.
Main results and technical application from this study
Hydrogen production results from food waste were shown to be possible with aerated inoculum in batch assays in thermophilic range, with highest H₂ yields of 19.72L/(kg oTS) from food waste. The inoculated HPB (Hydrogen producing bacterial) sludge taken from ASBR acid producing reactor was proved the optimum H₂ yields with the value of 61.41 L/(kg oTS) in this batch test. Inoculum to substrates ratio at 3 was found the best situ for H₂ yields in batch test. Even H₂ productivity at hyperthermophilic range has been confirmed with faster and higher performance, thermophilic fermentation process was taken in continuously lab-scale investigation due to too high process requirements in hyperthermophilic process.
Two-stage sequencing producing H₂+CH₄ was shown the potential in H₂ yields in the first acid producing phase. Methane yields from monodigestion in ASBR methane reactor with OLR of 3.88 kg oTS/(m3.d) and average CH₄ yields at 312.71L/kg oTS were achieved and act as reference value for total energy recovery.
In CSTR+ASBRMe system, the max. hydrogen yields of 69.15 L/(kg oTS) and CH₄ yields at 291.77. L/(kg oTS) were achieved; In semi-Percolator+ASBRMe system, the max. hydrogen yields of 77.34 L/kg oTS and average CH₄ yields at 293.87 L/(kg oTS) were achieved; In ASBR+ASBRMe system, the max. hydrogen yields of 196.85L/(kg oTS) and average CH₄ yields at 293.87 L/(kg oTS) were achieved. The max. H₂ concentration in hydrolysis gas was got in ASBR acid producing reactor at 54%.
The experimental results indicated that food wastes can be considered as suitable substrates for BioH₂ and CH₄ sequencing production. Moreover, the less production cost for H₂ due to higher OLR and shorting HRT.
Energieeffizientes Nährstoffsplitting von flüssigen Wirtschaftsdüngern mittels Membranfiltration
(2017)
Die definierte Selektivität der Membranfiltration kann dazu genutzt werden, einzelne spezifische Gülle-Separationsprobleme in übergeordneten Aufbereitungsklassen zusammenzufassen. Mit dem Ansatz einer gesteuerten Nährstofftrennung bzw. Teilzusammenführung von modifizierten Strömen, und der Zuordnung von spezifischen Aufgaben an die Mischprodukte, werden die Nachteile des Ausgangsrohstoffs reduziert und der Wertstoff Gülle rückstandsfrei nutzbar gemacht. Mit einem Anlagenmodell, bestehend aus einer Hydrotankpresse als Vorfiltration und einer Ultrafiltration als Kernkomponenten, ist es über empirisch ermittelte Betriebsparameter möglich, einen energetisch optimierten und kontinuierlichen Produktionsbetrieb durchzuführen. Als Produkte der dezentralen Aufbereitungsanlage werden ein emissionsreduzierender Flüssigdünger, eine als Brennstoff und als Gärsubstrat geeignete Feststoffphase, sowie das Retentat als aktivierendes Material zur Biogasertragssteigerung gewonnen. Das untersuchte Anlagenmodell ist auf den innerbetrieblichen Einsatz in Milchviehhaltungsbetrieben abgestimmt. Mit der Erarbeitung von stabilen und energetisch günstigen Anlagenbetriebspunkten wird das Anlagenverhalten hydraulisch steuerbar. Durch die Zuordnung von Anlagenzuständen zu differenziertem Spülverhalten, wird die direkte Einflussnahme der Temperatur auf den Permeat-Flux erkennbar. Der Einsatz eines Tauchkühlers, mit voreingestellten Grenztemperaturen, stabilisiert signifikant das Anlagenverhalten im Vergleich zu konventionellen Anlagenkonfigurationen. Die Anwendung einer Hydropresse gestattet höhere TDS-Belastungen im UF-Kreislauf, bietet aber kein Potenzial zur Steigerung der Nährstoffdurchsätze. Dies gilt auch für den Einsatz einer 300 kDa-Variante, im Vergleich zur priorisierten 150 kDa-UF-Membran. Mit der Hydropresse kann eine höhere Feststoffabscheidung wie mit Verstopfungs- bzw. Siebfiltrationen erreicht werden, die TDS-Belastungen sind im Retentat auf 5.000 - 7.000 ppm limitiert, oder müssen durch Verdünnung auf diese Werte eingegrenzt werden. Mit der zusätzlichen Anwendung einer Gasspülung in der Anströmung der UF-Module, können TDS-Belastungen über 10.000 ppm erstmals dauerhaft bewältigt werden. Über die so erweiterte Verfahrenstechnik sind Standzeiten von mehreren Wochen, ohne betrieblich bedingte Unterbrechungen, möglich. Die durch Fluoreszenzmikroskopie nachweisbare Anreicherung von Methanbildnern im Retentat, bestätigt eine mögliche Anwendung des Retentats als Biogassubstratergänzung. Der Biogasertrag wird durch Zusatz von Retentat zu den bisher verfügbaren Substraten generell erhöht. Eine Mischung aus Retentat und dem Feststoff aus der Hydropresse unterstützen die biochemische Stabilisierung in Fermentern. In Kombination mit Anteilen an Feststoff ist das Permeat bei der Bewertung von pflanzenbaulichen Erträgen, als konkurrenzfähig zu Rohgülle und Mineralstoffdünger einzustufen. Das auf landwirtschaftliche Flächen ausgebrachte Permeat ist geruchslos.
Wastewater treatment systems abound as a result of technological improvements in treatment processes. Therefore in the selection of a wastewater treatment system for a particular wastewater treatment situation there are many alternatives to choose from. Despite this development municipal wastewater treatment in communities in developing countries are not always sustainable due to the application of inappropriate treatment systems. The question is how can an appropriate treatment system be identified for a certain location? The answer to this question is of importance to developing countries where wastewater treatment is usually not sustainable.
In this study a framework for assessing wastewater treatment systems was developed. First, a comprehensive set of indicators representing parameters of treatment systems and properties of the study area that impacts on wastewater treatment were identified. Secondly, assessment of these indicators were carried out through expert and community survey to identify a final set of indicators whose composition consist of efficiency, reliability and simplicity of treatment systems and resource constraint, resource recovery and environmental concerns of the study area. Thirdly, four wastewater treatment systems, namely: Waste Stabilization Ponds, Trickling Filter, reed bed and free water surface Constructed Wetlands considered to be feasible for the study area were evaluated by the application of the identified indicators. Finally, a decision matrix produced was processed by multi-attribute decision making methods using two indicator weights to identify the most appropriate treatment system among the four alternatives.
Results of the study show that in a scenario where equal indicator weights are assumed, reed bed is identified as the most appropriate with stabilization ponds being ranked as the least appropriate. In a more practical scenario where the weights of the indicators are allocated to reflect conditions of the study area, free water surface is ranked as the most appropriate. This outcome is at variance with stabilization pond technologies currently installed at communities in the study area. The performance of constructed wetlands is at the midpoint as far as most of the high to medium weighted assessment indicators are concern. It therefore represents a compromising solution between waste stabilization pond and trickling filter. The study also shows a change in variants of constructed wetland with a change in indicator weights. An indication that the decision situation determines the appropriateness of a treatment system and not the treatment system itself.
The selection framework employed in this study can be said to be reliable and capable of identifying a treatment system that can be appropriate for a particular location. This is because the choice of a constructed wetland for the study area fits the definition of appropriate treatment system defined by the final indicators identified in this study.