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A study of the performance of biochar as adsorbing agent in o‐DGT devices / En studie av egenskaperna hos biokol som adsorberande agent i o‐DGT anordningarEliasson, Anna January 2017 (has links)
A new complex aspect in the matter of water quality is the occurrence of emerging organic pollutants and contaminants in waste water. The currently low extent to which treatment of waste water is performed in Brazil, and in the world as a whole, there is a considerable need for development of cheap and accurate in-situ sampling methods for far-reaching studies of surface water quality. The lack of such methods today makes the maintenance and establishing of sanitary safety difficult. This diploma work gives a brief introduction to the basic principles of the passive sampling method known as Diffusive Gradient in Thin-films (DGT). A method that could be useful for such monitoring of quality in water bodies world wide. The aim of this study is to develop a method, for the detection of organic emerging pollutants and contaminants – i.e. compounds, which usually are present at very low concentrations when found in the environment as a result of human activity. More specifically, this work investigates the potential and usefulness of the application of DGT devices in detection of organic compounds that can affect human health and ecosystems, even at low concentrations, however, their effects still are in need of further investigations. This study focuses on both purely technical as well as practical points of views. The efficiency of organic DGT (o-DGT) with biochar as the adsorbing agent is examined targeting the detection of organic pollutants and contaminants in surface water. In this sense, the specific aim of the work is to evaluate the performance of biochar as adsorbing agent. This work showed that the performance of biochar as the adsorbing agent in binding layers in o-DGT sample devices can be considered as satisfactory since all compounds of interest in this study was successfully detected, quantified an identified. Further investigations in the future are needed to determine the effects of varying pH, temperature and ion concentration in the deployment media, as well as the properties of the binding layer in relation to concentration of biochar and the thickness of the layer. These in order to optimize the method for in-situ water sampling, aiming conventional use of biochar as the adsorbing agent in the future.
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Assessment of exposure and response to atmospherically-derived contaminants in U.S. Arctic freshwater fishAllen-Gil, Susan M. 12 April 1995 (has links)
The Arctic has long been considered to be a pristine environment, far
from population centers and pollution sources. The detection of synthetic
organochlorine compounds in various elements of the Arctic food web has confirmed
the global dispersion of pollutants, particularly of persistent compounds such as
organochlorines and heavy metals. Levels of heavy metals, although elevated, appear
to be naturally so throughout much of the Arctic. Arctic pollution is both a
humanitarian and ecological concern. Many arctic coastal communities depend heavily
on marine mammal fat for sustenance, and are therefore potentially exposed to high
levels of organochlorines and some metals. From an ecological perspective, the
structure of arctic food webs, the importance of lipid mobilization for winter survival,
and the adaptive physiologies of arctic organisms may result in an enhanced response to
contaminant exposure. This thesis assesses the exposure and effect of organochlorine
and heavy metal exposure in inland freshwater ecosystems of Arctic Alaska, and
evaluates the physiological response of arctic grayling to experimental polychlorinated
biphenyl (PCB) exposure. / Graduation date: 1995
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Exposure to birch pollen and development of atopic disease in childhood /Kihlström, Anne, January 2004 (has links)
Diss. (sammanfattning) Stockholm : Karol. inst., 2004. / Härtill 4 uppsatser.
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Contamination des logements français en composés organiques semi-volatils en phase particulaire / Nationwide estimates of semi-volatile organic compounds in settled dust and suspended particles in French homesSawka, Corinne 10 December 2015 (has links)
Les composés organiques semi-volatils (COSV) font l’objet d’une attention croissante depuis une dizaine d’années. Utilisés dans de nombreux produits et matériaux du quotidien, ils sont émis dans les bâtiments par dispersion lors de l’usage, par évaporation ou abrasion. Du fait de leurs caractéristiques physico-chimiques, ces composés se répartissent à la fois dans l’air, en phases gazeuse et particulaire, et dans les poussières déposées au sol, sur le mobilier et les objets. Compte tenu du temps passé par la population dans les bâtiments, en particulier par les populations sensibles comme les enfants, les femmes enceintes et les personnes âgées, l’exposition à ces substances mérite d’être documentée, tenant compte des voies d’exposition en jeu : inhalation, ingestion et contact cutané. La thèse a porté sur les COSV présents en phase particulaire dans les logements. L’objectif de la thèse visait à exploiter les mesures de 66 COSV dans les particules en suspension de diamètre inférieur à 10 µm (PM10) et de 48 COSV dans les poussières au sol de taille inférieure à 100 µm considérées comme étant celles adhérant à la peau. Ces mesures ont été réalisées dans le cadre de deux campagnes nationales : la campagne « Logements » de l’Observatoire de la qualité de l’air intérieur conduite en 2003-2005 et l’enquête Plomb-Habitat dont les prélèvements ont eu lieu en 2008-2009. Une hiérarchisation des molécules jugées prioritaires au regard de leur impact sanitaire potentiel avait permis au préalable d’établir la liste des COSV à mesurer. L’exploitation de ces données de contamination a notamment porté sur l’identification d’éventuelles spécificités françaises au regard des molécules en présence et/ou des concentrations mesurées. Elle a permis de mettre en lumière un ensemble de facteurs déterminants de l’exposition (influence de la taille des particules, du type de poussières collectées, de leur bioaccessibilité), qui ne sont pas toujours considérés et qui limitent par ailleurs la comparabilité des résultats. Les concentrations mesurées ont aussi permis d’évaluer rétrospectivement la hiérarchisation sanitaire et d’en confirmer la pertinence. Les concentrations des COSV quantifiés à la fois dans l’air et au sol ont été mises en perspective afin d’examiner dans quelle mesure les particules en suspension et les poussières déposées sont similaires en termes de concentrations et de mélanges de COSV en présence. Enfin, l‘estimation des doses d’exposition aux COSV à partir d’équations simples, de variables humaines d’exposition et des données de contamination a permis une première évaluation des contributions respectives de l’inhalation et de l’ingestion aux expositions domestiques des enfants et adultes à ces composés en phase particulaire. / Semi-volatile organic compounds (SVOCs) refer to a broad spectrum of molecules from different chemical families that have numerous properties. They can be used as pesticides, plasticizers, flame retardants, surfactants, lubricants, etc. Consequently, they are introduced in numerous applications in buildings or used daily by the entire population. Once emitted through evaporation or abrasion in the indoor environment or introduced from the outdoors, their chemical or biological degradation is limited, and they persist indoors. This persistence also explains why some SVOCs that were banned a few years ago are still detected in the air and dust inside buildings. In indoor environments, SVOCs are divided between the gas phase, airborne particles, and dust settled on floors and surfaces. SVOCs are of concern due to their established or suspected health effects and their widespread exposure through different environmental media and pathways. The objective of the thesis was to study the concentrations of 66 SVOCs on airborne particles (PM10) and 48 SVOCs in settled dust in two samples of dwellings randomly selected across France. PM10 were sampled during the nationwide housing survey carried out by the French Observatory of indoor air quality in 2003-2005. The dust samples were collected from vacuum cleaner bags during a nationwide survey carried out in French dwellings where at least one child aged 6 months to 6 years lived (2008-2009). The SVOCs to be analyzed had prior been selected using a ranking method based on their toxicity and indoor concentrations. The data analysis focused in particular on the identification of French specificities in terms of detected molecules and measured concentrations. It highlighted some determinants of exposure, e.g., influence of particle size, type of dust collected, dust bioaccessibility, which are not always considered and limit the comparability of results. The measured concentrations were also used to assess the health ranking implemented prior to this work and to confirm its relevance. The concentrations measured both in the air and in settled dust were compared to study the similarities in terms of concentrations and SVOC mixtures. Finally, the exposure doses to SVOCs were calculated for both a child and an adult to assess the respective contributions of inhalation and ingestion to these compounds in particulate phase in dwellings.
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Abiotic Reduction Transformations of Recalcitrant Chlorinated Methanes, Chlorinated Ethanes, and 2,4-Dinitroanisole By Reduced Iron Oxides at Bench-ScaleBurdsall, Adam C. 07 June 2018 (has links)
No description available.
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Kontinuerliga sensormätningar av turbiditet som metod för att kvantifiera transport och avskiljning av föroreningar i dagvatten / Continuous sensor measurements of turbidity as a proxy for transport and removal of pollutants in stormwaterSvenda, Sara January 2024 (has links)
Dagvatten är det vatten som faller som nederbörd och sedan rinner över vägar och bebyggelse ned i brunnar eller direkt till recipienten. Dagvatten innehåller många olika föroreningar som kan vara direkt skadliga för vattenmiljön. I examensarbetet undersöks Gottsunda dagvattenpark som syftar till att rena dagvattnet innan det når recipienten Hågaån. Målet är att alla ytvattenförekomster i Sverige ska uppnå god ekologisk och kemisk ytvattenstatus, då Hågaån inte uppnår detta i dagsläget är det viktigt att kvantifiera hur väl den befintliga reningen av dagvatten fungerar. Syftet med examensarbetet är att undersöka om kontinuerlig turbiditets- och flödesmätning kan vara en fungerande metod för att kvantifiera transport och avskiljning av dagvattenföroreningarna suspenderat material, fosfor, kadmium, krom, nickel, koppar, bly och zink. Kontinuerliga sensormätningar kan i högre grad fånga in den snabba variationen i dagvatten än konventionella mätmetoder. Bland annat kan turbiditet mätas kontinuerligt med sensorer, en parameter som ofta visar hög korrelation med bland annat suspenderat material. Denna studie visade att signifikanta linjära samband finns mellan turbiditet med suspenderat material, fosfor och metaller för Gottsunda dagvattenparks in- och utlopp. En viss osäkerhet förekommer för sambanden i inloppet till följd av extremvärden med hög influens där ett behov finns av fler stickprover. Den beräknade avskiljningen i denna studie är något lägre än vad som förväntas, en möjlig förklaring är den stora fraktionen lerjordar i avrinningsområdet samt att dammen är förhållandevis nyetablerad. En ytterligare förklaring kan vara att det inte är exakt samma vattenpaket som undersökts i in- och utlopp, vilket antas gett upphov till en underskattning av avskiljningen. Vid viktning av mängderna utifrån en korrekt vattenbalans uppnås en högre avskiljning. Avskiljningsförmågan i Gottsunda dagvattenpark har i stort ökat med tiden men med sämre avskiljning under vintermånaderna. Kontinuerliga sensormätningar fungerar bra för att uppskatta medelkoncentrationer och belastningar av föroreningar och har potentialen att revolutionera dagvattenövervakningen. Dock behövs mer forskning där bland annat partikelsammansättningens påverkan behöver undersökas. / Stormwater is the precipitation that falls over cities and proceeds to flow on our streets, collecting pollutants on its way to the recipient. Stormwater contains a lot of different pollutants that can cause harm to our water bodies. In the study, Gottsunda stormwater pond is examined, whose purpose is to purify the stormwater before it reaches the recipient Hågaån. The goal is that all waters in Sweden should achieve good ecological and chemical surface water status. Since this isn’t achieved by Hågaån it is important to quantify if the current stormwater purification works as intended. The purpose of this study is to examine the potential to use high frequency sensors, measuring turbidity and discharge, to quantify transport and removal of the stormwater pollutants suspended solids, phosphorus, cadmium, chromium, nickel, copper, lead, and zinc. Measuring turbidity and discharge continuously using high frequency sensors can capture the fast variation in stormwater to a higher extent than conventional methods. Turbidity is a parameter which often shows high correlation with e.g. suspended solids. The study showed significant linear relationships between turbidity with suspended solids, phosphorus, and metals for incoming and outgoing water of Gottsunda stormwater pond. Uncertainty is present in the relationships for the incoming water due to extreme values with high influence, thus more grab samples are required. The calculated removal of pollutants is below the expected level, a possible explanation for this is the high fraction of clay soils in the catchment and the young age of the pond. Another explanation could be that the water volumes differ between in- and outlet. Considering the same volumes a higher removal is retrieved. The ability to remove pollutants has increased over time since the pond was established, with exception for the winter months. High frequency sensor measurements work well for estimating mean concentrations and loads of pollutants and has the potential of revolutionizing surveillance of stormwater. Although, more research is required where the effect of particle composition needs to be examined more closely.
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[en] METROLOGICAL EVALUATION OF OPTICAL EMITTERS AND DETECTORS APPLIED TO THE CHARACTERIZATION OF ATMOSPHERIC PARTICULATES POLLUTANTS / [pt] AVALIAÇÃO METROLÓGICA DE EMISSORES E DETECTORES ÓPTICOS APLICADOS À CARACTERIZAÇÃO DE POLUENTES PARTICULADOS ATMOSFÉRICOSMONICA ARI SANO 25 June 2003 (has links)
[pt] A poluição atmosférica é um problema mundial latente e é
prejudicial à saúde, à visibilidade e ao clima. Devido a
estes fatores, diversos estudos e pesquisas foram
desenvolvidos para caracterizar a sua composição química,
concentração, tamanho de partículas, etc. Com o objetivo de
construir instrumentos adequados para o controle da
qualidade do ar, mas estes instrumentos são sofisticados,
complicados e de alto custo.
Esta dissertação refere-se ao estudo de viabilidade para a
utilização de componentes optoeletrônicos simples, tais
como diodos emissores de luz (LED) e fotodetectores
ópticos, como sensores de medição da variação da
concentração de poluentes particulados atmosféricos em
relação ao tempo.
O principio de medição baseia-se nas propriedades ópticas
da luz: reflexão, refração e absorção que ocorre quando um
feixe de luz incide sobre as partículas de um poluente
qualquer, dando lugar à atenuação da intensidade do feixe
incidente, que é proporcional à concentração de poluente.
Selecionaram-se LED e fotodetectores, segundo as
informações dadas nas especificações fornecidas pelo
fabricante. Formaram-se quatro tipos diferentes de Pares
Emissores-Detectores, (Pares E-D), onde cada LED
trabalhava com um fotodetector específico.
As avaliações foram feitas em função dos Pares E-D nas
condições recomendadas pelo fabricante e, selecionaram-se
dois tipos diferentes de Pares E-D, que apresentaram
melhores características físicas, tempo de resposta (11 e
16µs), o nível do sinal gerado pelo fotodetector (entre
2,50V e 3,50V), e estabilidade em uma faixa de temperatura
de 20oC à 30oC.
Para testar o funcionamento dos Pares E-D como sensores de
medição da variação da concentração dos poluentes
particulados atmosféricos foi construída uma maquete
instrumentada com oito Pares (E-D), quatro de cada
tipo dos Pares E-D selecionados previamente. Teve-se
cuidado na disposição física dos Pares E-D para evitar
interferências de luz. Para diminuir o ruído do circuito, a
placa Protoboard foi substituída por uma placa impressa. A
razão sinal/ruído foi de 3,242V/0,020V, (162:1).
Foi desenvolvido um programa especifico no software
LabVIEW, com o propósito de registrar os sinais gerados
pelos fotodetectores a cada 10 µs e armazená-los em uma
base de dados para posterior análise.
A maquete instrumentada e o software de aquisição
representam um sistema de medição para a caracterização da
dispersão dos poluentes particulados atmosféricos.
Para verificar o desempenho da maquete instrumentada e do
software de aquisição, foram feitas simulações de
contaminação ambiental. Utilizando uma máquina geradora de
fumaça, jogou-se fumaça sobre a maquete, foram obtidos
resultados satisfatórios, já que trabalhando com os oito
Pares E-D ativos, conseguiu-se obter 12500 dados por
segundo para cada Par E-D.
Estas quantidades de dados registrados pelo programa feito
no software LabVIEW foram mais que suficientes para a
construção das curvas de caracterização preliminares. / [en] The atmospheric pollution is a latent world-wide problem,
and it is harmful to the health, visibility and climate.
For these factors, several studies and researches have been
developed to characterize the chemical composition
of the pollutants, concentration, size of particles, etc,
with the objective of constructing adjusted instruments for
the control of the air quality, but these instruments are
sophisticated, complicated and very expensive.
This dissertation is a study about the feasibility to use
simple optoelectronic components, such as light emitting
diodes (LED) and optical photo detectors, as sensors for
measuring the variation of the concentration of atmospheric
particulate pollutants in relation to time.
The measurement principle is based on the optic properties
of the light: reflection, refraction and absorption that
occur when a light beam arrives on particles of any
pollutant, taking place the attenuation of the intensity of
the incident beam, which is proportional to the pollutant
concentration.
LED and photo detectors were selected according to
information given in the specifications supplied for the
manufacturer. Four different types of Pairs
formed Emitters-Detectors, (Pairs E-D), where each LED
worked with a specific photo detector.
The evaluations were made in function of the Pairs E-D
according to the recommendation of the manufacturer and two
types different of Pairs E-D were selected, which presented
better physical characteristics, time of response (11
and 16µs), level of the signal generated by the photo
detector, (between 2,50V and 3,50V), and stability in a
range of temperatures between 20oC to 30oC.
To test the functioning of the Pairs E-D as sensors for
measuring of the variation of the concentration of the
atmospheric particulate pollutants. It was
built an instrumented reduced model with eight Pairs E-D
was built, four of each type of the Pairs E-D selected
previously. It was taken care of the physical disposition
of the Pairs E-D to prevent light interferences. To reduce
the noise of the circuit, the Protoboard was substituted by
a circuit board printed. The relation signal/noise was
3,242V/0,020V, (162:1).
A specific program was developed in the software LabVIEW.
The goal was to register the signals generated by photo
detectors at each 10µs, and to store the data for posterior
analysis.
The instrumented reduced model and the software to the data
acquisition represent a system for measurement and the
characterization of the dispersion of the atmospheric
particulate pollutants.
To verify the performance of the instrumented reduced model
and the software for acquisition, simulations of ambient
contamination were made. A FOG machine was used to generate
smoke on the reduced model, The results were satisfactory.
Working with the eight active E-D Pairs, it was possible to
get 12500 data per second for each Pair E-D. This amount of
registered data by the acquisition program in LabVIEW was
enough for the construction of the preliminary curves of
characterization for the E-D Pairs.
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Evaluation et traitement des polluants émis par un moteur thermique fonctionnant avec des biocarburants / Evaluation and treatment of polluants emitted by an engine fed with biofuelsCosseron, Anne-Flore 29 October 2012 (has links)
Les biocarburants présentent une alternative prometteuse à l’utilisation de carburants fossiles. Cependant, l’augmentation de la quantité de biocarburants introduite dans les carburants nécessite de connaître leur impact sur les émissions de polluants. Le travail réalisé lors de cette thèse peut être décrit en deux parties : La première traite de l’évaluation des émissions de polluants réglementés et non réglementés émis par la combustion de biocarburants dans un moteur diesel. Différents biocarburants ont été testés : des esters méthyliques d’huile de soja et de colza, des esters éthyliques d’huile usagée et un carburant de référence exempt de tout biocarburant. Les résultats montrent que la nature des biocarburants ainsi que leur teneur ont un impact sur les polluants émis. Par exemple, une diminution de la taille des particules émises a été observée avec l’utilisation des esters méthyliques d’huile de soja. Le deuxième objectif de cette thèse concerne le piégeage des polluants Diesel, notamment des composés organiques volatils par des zéolithes. Plusieurs zéolithes ont été synthétisées puis caractérisées. Des tests d’adsorption par thermogravimétrie ont ensuite été réalisés au laboratoire avec différentes molécules sondes représentatives des polluants émis par les moteurs Diesel (le n-hexane, le p-xylène et l’acétone). Certaines zéolithes comme les zéolithes faujasite présentent des capacités d’adsorption intéressantes. Toutefois, la plupart des résultats montrent une diminution de la capacité d’adsorption avec l’augmentation de la température. Ces zéolithes ont ensuite été placées en sortie d’échappement d’un moteur diesel afin d’étudier leur capacité d’adsorption. / Nowadays, biofuels are a promising alternative to the use of fossil fuels. However, increasing the amount of biofuels introduced in fuels requires to know their impact on emissions pollutants.The work done in this thesis can be described in two parts: The first one deals with the evaluation of emissions of regulated pollutants (NOx, CO, CO2, O2, THC) and unregulated pollutants (volatile organic compounds, carbonyl compounds and fine particles (between 30 nm and 10 microns)) emitted by the combustion of biofuels in a diesel engine. Different biofuels have been tested: methyl esters of soybean oil and rapeseed oil, ethyl esters of used oil and a reference fuel free of biofuel. The results show that the nature of biofuels and their content have an impact on the pollutants emitted. For example, a decrease in the size of the particles emitted was observed with the use of methyl esters of soybean oil. The second objective of this thesis was to trap pollutants, like volatile organic compounds (VOCs) with zeolites. Several hydrophilic and hydrophobic zeolites have been synthesized and characterized. Adsorption tests were then carried by thermogravimetry with different probe molecules representative of pollutants from diesel engines (n-hexane, p-xylene and acetone). Some zeolites such as faujasite zeolites have interesting adsorption capacities. However, most of the results show a decrease in the adsorption capacity with the increase of the temperature. Then, these zeolites have been placed in the exhaust outlet of a diesel engine in order to study their adsorption capacity.
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Development and application of a new passive sampling device : the lipid-free tube (LFT) samplerQuarles, Lucas W. 29 September 2009 (has links)
Contaminants can exist in a wide range of states in aqueous environments, especially in surface waters. They can be freely dissolved or associated with dissolved or particulate organic matter depending on their chemical and physical characteristics. The freely dissolved fraction represents the most bioavailable fraction to an organism. These freely dissolved contaminants can cross biomembranes, potentially exerting toxic effects. Passive sampling devices (PSDs) have been developed to aid in sampling many of these contaminants by having the ability to distinguish between the freely dissolved and bound fraction of a contaminant. A new PSD, the Lipid-Free Tube (LFT) sampler was developed in response to some of the shortcomings of other current PSD that sample hydrophobic organic contaminants (HOCs). The device and laboratory methods were original modeled after a widely utilized PSD, the semipermeable membrane device (SPMD), and then improved upon. The effectiveness, efficiency, and sensitivity of not only the PSD itself, but also the laboratory methods were investigated. One requirement during LFT development was to ensure LFTs could be coupled with biological analyses without deleterious results. In an embryonic zebrafish developmental toxicity assay, embryos exposed to un-fortified LFT extracts did not show significant adverse biological response as compared to controls. Also, LFT technology lends itself to easy application in monitoring
pesticides at remote sampling sites. LFTs were utilized during a series of training exchanges between Oregon State University and the Centre de Recherches en Ecotoxicologie pour le Sahel (CERES)/LOCUSTOX laboratory in Dakar, Senegal that sought to build "in country" analytical capacity. Application of LFTs as biological surrogates for predicting potential human health risk endpoints, such as those in a public health assessment was also investigated. LFT mass and accumulated contaminant masses were used directly, representing the amount of contaminants an organism would be exposed to through partitioning assuming steady state without metabolism. These exposure concentrations allow for calculating potential health risks in a human health risk model. LFT prove to be a robust tool not only for assessing bioavailable water concentrations of HOCs, but also potentially providing many insights into the toxicological significance of aquatic contaminants and mixtures. / Graduation date: 2010
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Biodegradation of cyanide and subsequent nitrification-aerobic denitrification in cyanide containing watewaterMekuto, Lukhanyo January 2014 (has links)
Thesis submitted in fulfilment of the requirements for the degree
Master of Technology: Chemical Engineering
in the Faculty of
Engineering
at the
Cape Peninsula University of Technology
2014 / Environmental legislation focusing on wastewater disposal in industries that utilise cyanide
and/or cyanide-related compounds has become increasingly stringent worldwide, with many
companies that utilise cyanide products required to abide by the Cyanide International Code
associated with the approval of process certifications and management of industries which
utilise cyanide. This code enforces the treatment or recycling of cyanide-contaminated
wastewater. Industries such as those involved in mineral processing, photo finishing, metal
plating, coal processing, synthetic fibre production, and extraction of precious metals, that is,
gold and silver, contribute significantly to cyanide contamination in the environment through
wastewater. As fresh water reserves throughout the world are low, cyanide contamination in
water reserves threatens not only the economy, but also endangers the lives of living
organisms that feed from these sources, including humans. In the mining industry, dilute
cyanide solutions are utilised for the recovery of base (e.g. Cu, Zn, Ni, etc.) and precious
metals (e.g. Au, Ag, etc.). However, for technical reasons, the water utilised for these
processes cannot be recycled upstream of the mineral bioleaching circuit as the
microorganisms employed in mineral bioleaching are sensitive to cyanide and its complexes,
and thus the presence of such compounds would inhibit microbial activity, resulting in poor
mineral oxidation. The inability to recycle the water has negative implications for water
conservation and re-use, especially in arid regions. A number of treatment methods have
been developed to remediate cyanide containing wastewaters. However, these chemical and
physical methods are capital intensive and produce excess sludge which requires additional
treatment. Furthermore, the by-products that are produced through these methods are
hazardous. Therefore, there is a need for the development of alternative methods that are
robust and economically viable for the bioremediation of cyanide-contaminated wastewater.
Biological treatment of free cyanide in industrial wastewaters has been proved a viable and
robust method for treatment of wastewaters containing cyanide. Several bacterial species,
including Bacillus sp., can degrade cyanide to less toxic products, as these microorganisms
are able to use the cyanide as a nitrogen source, producing ammonia and carbon dioxide.
These bacterial species secrete enzymes that catalyse the degradation of cyanide into
several end-products. The end-products of biodegradation can then be utilised by the
microorganisms as nutrient sources.
This study focused on the isolation and identification of bacterial species in wastewater
containing elevated concentrations of cyanide, and the assessment of the cyanide
biodegradation ability of the isolates. Thirteen bacterial isolates were isolated from
electroplating wastewater by suppressing the growth of fungal organisms and these species
were identified as species belonging to the Bacillus genus using the 16S rDNA gene. A
mixed culture of the isolates was cultured in nutrient broth for 48 hours at 37°C, to which FCN
as KCN was added to evaluate the species‟ ability to tolerate and biodegrade cyanide in
batch bioreactors. Subsequently, cultures were supplemented solely with agro-waste
extracts, that is, Ananas comosus extract (1% v/v), Beta vulgaris extract (1% v/v), Ipomea
batatas extract (1% v/v), spent brewer‟s yeast (1% v/v) and whey (0.5% w/v), as the primary
carbon sources. Owing to the formation of high ammonium concentration from the cyanide
biodegradation process, the nitrification and aerobic denitrification ability of the isolates,
classified as cyanide-degrading bacteria (CDB) was evaluated in a batch and pneumatic
bioreactor in comparison with ammonia-oxidising bacteria (AOB). Furthermore, the effects of
F-CN on the nitrification and aerobic denitrification was evaluated assess the impact of F-CN
presence on nitrification. Additionally, optimisation of culture conditions with reference to
temperature, pH and substrate concentration was evaluated using response surface
methodology. Using the optimised data, a continuous biodegradation process was carried
out in a dual-stage packed- bed reactor combined with a pneumatic bioreactor for the
biodegradation of F-CN and subsequent nitrification and aerobic denitrification of the formed
ammonium and nitrates.
The isolated bacterial species were found to be gram positive and were able to produce
endospores that were centrally located; using the 16S rDNA gene, the species were found to
belong to the Bacillus genus. The species were able to degrade high cyanide concentration
in nutrient broth with degradation efficiencies of 87.6%, 65.4%, 57.0% and 43.6% from 100
mg F-CN/L, 200 mg F-CN/L, 300 mg F-CN/L, 400 mg F-CN/L and 500 mg F-CN/L
respectively over a period of 8 days. Additionally, the isolates were able to degrade cyanide
in an agro-waste supported medium, especially in a medium that was supplemented with
whey which achieved a degradation efficiency of 90% and 60% from 200 mg F-CN/L and 400
mg F-CN/L, respectively over a period of 5 days. The nitrification ability of the isolates was
evaluated and the removal of NH4
+/NO3
- by the CDB and AOB in both shake flasks and
pneumatic bioreactor was determined to be pH dependent. The maximum NH4
+/NO3
-
removal evaluated over a period of 8 days for CDB and 15 days for AOB, observed at pH 7.7
in shake flasks, was 75% and 88%, respectively, in the absence of F-CN. Similarly, the
removal of NH4
+/NO3
- in a pneumatic bioreactor was found to be 97.31% for CDB and 92%
for AOB, thus demonstrating the importance of aeration in the designed process. The
nitrification by CDB was not inhibited by cyanide loading up to a concentration of 8 mg FCN/
L, while the AOB were inhibited at cyanide loading concentration of 1 mg F-CN/L. The
CDB removed the NH4
+/NO3
- in PBSs operated in a fed-batch mode, obtaining efficiencies
>99% (NH4
+) and 76 to 98% (NO3
-) in repeated cycles (n = 3) under F-CN (≤8 mg F-CN/L).
The input variables, that is, pH, temperature and whey-waste concentration, were optimised
using a numerical optimisation technique where the optimum conditions were found to be: pH
9.88, temperature 33.60 °C and whey-waste concentration 14.27 g/L, under which 206.53
mg CN-/L in 96 h can be biodegraded by the microbial species from an initial cyanide
concentration of 500 mg F-CN/L. Furthermore, using the optimised data, cyanide
biodegradation in a continuous mode was evaluated in a dual-stage packed-bed bioreactor
connected in series to a pneumatic bioreactor system used for simultaneous nitrification
including aerobic denitrification. The whey-supported Bacillus sp. culture was not inhibited by
the free cyanide concentration of up to 500 mg F-CN/L, with an overall degradation efficiency
of ≥99% with subsequent nitrification and aerobic denitrification of the formed ammoniu and
nitrates over a period of 80 days.
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