No description available.

Hydrous aluminum oxide colloids of 0.5 Am diameter were used to study the coagulation of submicron particles under water-treatment conditions. The research was aimed at understanding the effects of pH and ligands (organic and inorganic) on precipitation of the added coagulant and their influences on incorporation of the colloids into larger flocs. The reduction in the concentration of submicron particles as a result of alum coagulation was monitored by conventional jar-test experiments. Scanning electron microscopy was used for submicron particle counting. Up to three orders of magnitude reduction in submicron particle concentrations were observed in jar-test experiments. Higher pH (i.e., 7.5) and alum dose (i.e., 1.0 mg L⁻¹) favored homogeneous precipitation of aluminum hydroxide, whereas heterogeneous precipitation occurred at lower pH (i.e., 6.5) and alum dose (i.e., 0.5 mg L⁻¹). Homogeneous precipitation, involving formation of Al(OH)₃(s) from aqueous species, formed large masses of light-weight flocs that can effectively remove submicron particles by subsequent coagulation. Heterogeneous precipitation, which involves precipitation on the surfaces of the seed particles, resulted in destabilized particles that can efficiently coagulate with each other. The presence of ligands, inorganic (e.g., HCO₃⁻) and organic (e.g., functional groups of humic substances) inhibited the coagulation process, reducing particle removal up-to 250 fold. While these ligands inhibit coagulation by modifying particle surfaces, they may enhance the precipitation reactions of aluminum hydroxide. The presence SO₄²⁻ enhanced precipitation relative to NO₃⁻. Electrophoretic mobility values were used to derive equilibrium constants for aluminum speciation and precipitation reactions, both on the surface of particles and in solution. The adsorption of ligands lowered the pHiep, by almost 2 pH units in the presence of HCO₃⁻, and to a pH of less than 3 in the presence of organics. Aluminum species elevated the pHiep by 1 pH unit. Stoichiometric ratios of aluminum hydroxide precipitation were determined using a pH stat. This ratio (1.9 to 3.7) is a function of pH, and concentrations of particles and organics. These results were modeled as spherical precipitates (OH/A1 =3) with adsorbed aluminum species (OH/A1 = 1 to 4). The results of this research suggest that the aluminum precipitation pathway dictates the removal of submicron particles. Submicron particles provide most of the surfaces from particulate matter, thus suggesting the importance of surface precipitation for their removal. Samples from water treatment plants indicated 1.5 to 2.0 log removal of submicron particles. These plants were operating at higher pH values (above 7.5) relative to that of maximum removal experiments in laboratory. Plant operations can be optimized by careful control parameters affecting supersaturation ratio, thus improving removal of submicron particles.Such optimization should include efficient rapid mixing to achieve uniform upersaturation ratios, proper coagulant dose, and possibly better pH control.

No description available.

Submitted in fulfilment of the academic requirements for the Degree of M.Tech: Chemical Engineering, M. L. Sultan Technikon, 2001. / Historically inorganic coagulants were the coagulants of choice for OAF treatment of potable water. Water treatment practitioners using OAF technology preferred ferric chloride, an inorganic coagulant. Ferric chloride formed light, floatable floes at relatively low flocculation intensities and detention times. The inorganic coagulant was also more forgiving during incidents of overdosing and raw water and pH variability / M

M.Sc. / Drinking water treatment plants in South Africa rely almost entirely on surface water sources, which are often compromised due to high return flows and indirect reuse. The typical treatment plants focus on the removal of physical and microbial contaminants which include turbidity, colour, chemical compounds and micro-organisms. A relatively new alarm to this list is natural organic matter (NOM) which has become a major concern in potable water treatment due to its recent regulation. Conventionally, the drive to remove NOM from potable water would be the desire to remove colour from public water supplies. However, more problems in drinking water treatment associated with NOM have been recently identified. These include taste and odour, its tendency to foul membranes, interference with the removal of other contaminants and its potential to contribute to corrosion and slime growth in distribution systems. Moreover, it causes high demands for coagulants and disinfectants. The NOM is also the main precursor for disinfection by-products (DBPs) formed when it interacts with disinfectants such as chlorine during water disinfection. In this study, different raw water samples, of different NOM composition were collected from selected sources across the country and assessed for the removal of dissolved organic carbon (DOC) and UV absorbance at a wavelength of 254 nm (UV 254) using enhanced coagulation (EC). The efficacy of EC, which can be employed as a practical technology in the removal of both turbidity and NOM, was evaluated in these raw water sources. Jar tests were conducted with ferric chloride as the coagulant, and specific pH values were chosen as target values guiding the different coagulant dosages for the jar tests. The pH of the low-alkalinity (<60 mg/ℓ CaCO3) raw waters were adjusted and raised by the addition of sodium carbonate. Algorithms for finding the optimum coagulant dosage for both turbidity and UV 254 removal were developed and consistently applied to all the results in independent v batch tests, in which residual amounts of UV 254, DOC and turbidity were measured. The raw water parameters and results obtained from these tests were used to develop feed-forward multiplicative models predicting the performance of EC using ferric chloride. The results showed that the raw waters chosen were, indeed, representative of the different water types present in South Africa, and that the general water characteristics were affected by seasonal variations. The EC procedure developed was able to reduce turbidity to levels low enough for removal by subsequent treatment steps in the water treatment train. The residual UV 254 values were in all cases lower than 6 m-1, which theoretically corresponds to about 3.5 mg/ℓ DOC. This was confirmed by the residual DOC values which were found to be lower than 4 mg/ℓ. Generally, the waters of South Africa were found to be amenable to coagulation. In almost all cases, the costs for EC were comparable to those for conventional coagulation, hence EC could be employed as a NOM removal strategy in the South African context.

The fate of iron complexed by various organic compounds was investigated as a function of both chemical oxidative and coagulation removal methods. Dissolved organic carbon (DOC) utilized in the studies was obtained from a variety of sources and included humic and fulvic acids, tannic acid and oxalic acid. Oxidants evaluated were potassium permanganate, free chlorine, and chlorine dioxide. Both laboratory-scale and field monitoring studies were performed. The relative molecular weight distribution (MWD) of the DOC present was analyzed to evaluate how changes in this parameter affected the efficiency of soluble iron removal by oxidation. In addition, the MWD of selected coagulated samples was evaluated to determine how this parameter affected the fate of complexed iron during the coagulation of dissolved organic matter with alum. A high degree of ferrous iron complexation occurred with the DOC dominated by higher molecular weight organics. This complexation rendered the iron stable against the addition of each of the oxidants evaluated. However, soluble Fe(II) complexed by low molecular weight organics was successfully removed by chemical oxidation. Potassium permanganate was found to be the most effective oxidant of the three oxidants utilized in the study. The results indicated that soluble Fe(II) complexed by high molecular weight DOC can be efficiently removed by alum coagulation. The pH and alum dose utilized to produce effective DOC removal was also found to promote efficient complexed Fe(II) removal. / Master of Science

Thesis (MScFoodSc)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: Large volumes of high strength wastewater are generated annually by distilleries. Treatment of this wastewater is essential to increase its reuse potential. Anaerobic digestion (AD) has been widely applied as high strength wastewater treatment. Additionally, grain distillery wastewater (GDWW) is high in fats, oils and grease (FOG) which can cause problems during AD. Pre-treatment is therefore often required to make the AD process more efficient. The overall objective of this study was to investigate the operational efficiency of upflow anaerobic sludge blanket (UASB) reactors while treating GDWW as substrate. The first aim was to investigate the pre-treatment of the GDWW specifically for the removal of FOG by evaluating the effect of pH adaption, coagulant concentration and ozone (O3) dosages on the FOG reduction efficiency. Secondly, the effect of two different pre-treatments (only coagulant and coagulant and ozone) on the subsequent UASB treatment step was investigated. The pH of raw GDWW (pH 3.4) was adapted to three different pH values (5.0, 6.0, and 7.0) and the coagulant, aluminium chlorohydrate (ACH) (140 mg.L-1), was added. To make the process more economically viable, the lowering the coagulant concentration (to 100 mgACH.L-1) was also investigated. Optimal reductions for chemical oxygen demand (COD) (33.2% ± 4.93), total suspended solids (TSS) (91.9% ± 1.73) and FOG (84.1% ± 1.98) were, however, achieved at a higher coagulant concentration of 140 mgACH.L-1, and at a wastewater pH of 7.0. The effect of additional ozone treatment was also investigated. Maximum reductions for the ozone treatment were obtained at 100 mgO3.L-1 for COD (3.6% ± 4.08), and at 900 mgO3.L-1 for TSS (27.7% ± 5.58) and FOG (23.9% ± 1.83). The ozone treatment was most efficient for FOG reduction (in terms of mg FOG reduced per mg ozone) at 100 mgO3.L-1. An ozone dosage of 300 mgO3.L-1, was decided on based on economic feasibility, findings in literature on toxicity of ozone and the potential degradation of recalcitrant compounds at this dosage. The final pre-treatment thus included pH adaption to 7.0, coagulant dosage of 140 mgACH.L-1, and an ozone dosage of 300 mgO3.L-1. The second part of this study involved the operation of two 2 L laboratory scale UASB reactors for 277 days. The substrate of the first reactor contained GDWW that had only undergone coagulant pre-treatment (Rcontrol), while the substrate of the second UASB reactor consisted of GDWW that had undergone coagulant and ozone pre-treatment (Rozone). Both reactors treated the pre-treated GDWW successfully at ca. 9 kgCOD.m-3d-1. COD reductions of 96% for Rcontrol and 93% for Rozone, were achieved. FOG reductions (%) showed variations throughout the study and maximum reductions of 88% and 92% were achieved for Rcontrol and Rozone, respectively. The Rozone produced more biogas, but the methane content was similar for both reactors. The additional ozone pre-treatment did not show any added benefits to the reactor performance results. UASB granule washout in Rcontrol did, however, suggest possible toxicity of unsaturated fatty acids present in the non-ozonated substrate. The feasibility of FOG removal was shown as both reactors successfully treated pre-treated GDWW. Ozonation, after a coagulant dosage, which resulted in further reduction in the FOG content of the GDWW, is thus not essential to ensure the success of an anaerobic digestion step. Ozonation of the pre-treated GDWW could, however, be beneficial to gas production and the efficiency of a tertiary biological process. / AFRIKAANSE OPSOMMING: Groot volumes hoë-sterkte afloopwater word jaarliks deur distilleerderye opgelewer. Die behandeling van hierdie afloopwater is noodsaaklik om die hergebruiksmoontlikheid daarvan te verhoog. Die toepassing van anaërobiese vertering (AV) is wydverspreid in hoë-sterkte afloopwaterbehandeling. Graandistillerings-afloopwater (GDAW) is boonop hoog in vette, olies en ghries (VOG), wat probleme kan veroorsaak tydens AV. Voorbehandeling word dus dikwels verlang om die AV meer doeltreffend te maak. Die oorhoofse doelstelling van hierdie studie was om die doeltreffendheid van opvloei-anaërobieseslykkombers- (OAS-) reaktore wat GDAW as substraat behandel, te ondersoek. Die eerste mikpunt was om die voorbehandeling van die GDAW, te ondersoek vir die verwydering van VOG. Dit is uitgevoer deur die uitwerking van pH aanpassing, koagulantkonsentrasie en osoon(O3)dosis op VOG vermindering te evalueer. Tweedens is die uitwerking van twee verskillende voorbehandelings (slegs koagulant asook koagulant en osoonbehandeling) op die opvolgende OAS-behandelingsstap ondersoek. Die pH van rou GDAW (pH 3.4) is aangepas tot drie verskillende pH waardes (5.0, 6.0 en 7.0) en die koagulant, aluminium-chlorohidraat (ACH), is bygevoeg (140 mg.L-1). Om die proses meer ekonomies uitvoerbaar te maak is ‘n verlaagde koagulantkonsentrasie (verlaag tot 100 mgACH.L-1) ook ondersoek. Die optimale afnames vir chemiese suurstofvereiste (CSV) (33.2% ± 4.93), totale oplosbare vastestowwe (TOV) (91.9% ± 1.73) en VOG (84.1% ± 1.98) is egter bereik teen ‘n hoër koagulant konsentrasie van 140 mgACH.L-1, en teen ‘n afloopwater-pH van 7.0. Die uitwerking van ‘n bykomende osoonbehandeling is ook ondersoek. Die hoogste afnames tydens die osoonbehandeling is bereik teen 100 mgO3.L-1 vir CSV (3.6% ± 4.08), en teen 900 mgO3.L-1 vir TOV (27.7% ± 5.58) en VOG (23.9% ± 1.83). Die osoonbehandeling was mees doeltreffend vir VOG (in terme van mg VOG verwyder per mg osoon) teen 100 mgO3.L-1. Daar is besluit op ‘n van 300 mgO3.L-1, as gevolg van die ekonomiese uitvoerbaarheid, bevindinge in literatuur vir die toksisiteit van osoon, en die moontlike afbraak van moeilik-afbreekbare komponente teen hierdie dosis. Die finale voorbehandeling het dus bestaan uit ‘n aanpassing van die afloopwater-pH na 7.0, ‘n koagulantdosis van 140 mgACH.L-1, en ‘n osoondosis van 300 mgO3.L-1. Tydens die tweede gedeelte van hierdie studie is twee 2 L laboratoriumskaal OAS reaktore bedryf vir 277 dae. Die substraat van die eerste reaktor het GDAW bevat wat slegs ‘n koagulant-voorbehandeling ondergaan het (Rkontrole), terwyl die substraat van die tweede OAS-reaktor GDAW bevat het wat koagulant- en osoon-voorbehandeling ondergaan het (Rosoon). Beide reaktore het die voorbehandelde-GDAW suksesvol behandel teen ‘n organieseladingstempo van ca. 9 kgCSV.m-3d-1. Afnames in CSV van 96% vir Rkontrole en 93% vir Rosoon, is bereik. Tydens die studie is deurlopende wisseling in VOG verwydering (%) waargeneem, en die hoogste verwyderings wat bereik is, is onderskeidelik 88% en 92% vir Rkontrole en Rosoon. Die Rosoon het meer biogas geproduseer, maar die metaanpersentasie was soortgelyk vir beide reaktore. Die osoon-voorbehandeling het nie enige toegevoegde voordele getoon in die reaktorprestasie resultate nie. Die uitwas van die OAS-granules vir die Rkontrole het egter moontlike toksisiteit van onversadigdevetsure aangedui, wat moontlik teenwoordig kon wees in die nie-geösoneerde substraat. Die uitvoerbaarheid van VOG verwydering is getoon aangesien beide reaktore voorbehandelde GDAW suksesvol behandel het. Osonering, wat verdere afname in die VOG inhoud van GDAW teweeggebring het (na ‘n koagulant dosis), is dus nie noodsaaklik vir die suksesvolle verloop van ‘n anaërobiese-verteringsstap nie. Osonering van die voorbehandelde GDAW kan egter voordelig wees vir gasvorming, en kan ook verder die doeltreffendheid van ‘n tersiêre biologiese behandeling verhoog.

No description available.

CAPES / A utilização de coagulantes naturais no tratamento de água vem sendo uma alternativa cada vez mais empregada a fim de evitar possíveis danos à saúde e ao meio ambiente causados por determinados coagulantes químicos. A Moringa oleifera é uma árvore de múltiplos usos, cujas sementes possuem uma eficiente atividade como coagulante natural. Entretanto, estudos apontam para uma possível toxicidade deste extrato. Baseando-se nisto, o objetivo do presente trabalho foi o de avaliar a toxicidade de três diferentes extratos de M. oleifera (extrato aquoso, extrato salino da semente integral e extrato salino da semente sem óleo) e da água tratada com os mesmos extratos, frente a duas espécies de microcrustáceos utilizadas como bioindicadoras de toxicidade (Daphnia magna e Artemia salina). Nos ensaios de toxicidade aguda dos extratos utilizando D. magna, verificou-se uma CE50 de 314,05 mg.L-1 para o extrato salino da semente integral e 346,76 mg.L-1 para o extrato salino da semente sem óleo. O extrato aquoso não apresentou toxicidade nem mesmo nas maiores concentrações (400 a 600 mg.L-1). Para o organismo A. salina, nenhum dos extratos mostrou-se tóxico. Nos ensaios realizados com a água tratada com os extratos de M. oleifera, foi encontrada toxicidade para D. magna nas frações sobrenadante (CE50=296,02 mg.L-1) e sedimentada (CE50=291,04 mg.L-1) da água tratada com o extrato salino da semente integral. Para a água tratada com o extrato salino da semente sem óleo, da mesma forma encontrou-se toxicidade nas frações sobrenadante (CE50=351,17 mg.L-1) e sedimentada (CE50=342,32 mg.L-1), o que indica que a toxicidade do extrato não é reduzida após a coagulação/floculação/sedimentação. No teste crônico realizado utilizando organismos de D. magna expostos durante 21 dias ao extrato salino da semente integral de M. oleifera, foram observadas alterações nos parâmetros avaliados (mortalidade, fecundidade e crescimento), sendo que quanto maior a concentração testada, maiores os efeitos tóxicos. Ao término dos 21 dias experimentais, havia ocorrido a mortalidade de 100% dos indivíduos expostos às maiores concentrações (10 e 15 mg.L-1). Além disso, houve grande variação na fecundidade entre os grupos. Com base nestes resultados, é possível afirmar que a utilização de elevadas concentrações do extrato de M. oleifera (acima de 300 mg.L-1) pode causar danos agudos ao organismo D. magna. Entretanto, na prática, as concentrações utilizadas deste coagulante são consideravelmente menores, variando principalmente entre 50 e 150 mg.L-1, de acordo com dados da literatura. Da mesma forma, a diluição que ocorreria no meio hídrico dificilmente proporcionaria que a concentração permanecesse elevada, mesmo que grande quantidade do extrato chegasse ao meio ambiente. Com base nisso, é possível afirmar que o uso do extrato da M. oleifera pode ser incentivado, mas desde que utilizado com cautela, evitando-se concentrações elevadas. / The use of natural coagulants for water treatment has been an alternative increasingly employed in order to avoid possible damage to health and the environment caused by certain chemical coagulants. Moringa oleifera is a multipurpose tree whose seeds have an efficient activity as natural coagulant. However, studies point to a possible toxicity of this extract. Based on this, the objective of this study was to evaluate the toxicity of three different extracts of M. oleifera (aqueous extract, saline extract of the whole seed and saline extract of the seed without oil) and water treated with the same extracts, against two species of microcrustaceans used as bioindicators of toxicity (Artemia salina and Daphnia magna). In acute toxicity tests of the extracts using D. magna, there was an EC50 of 314.05 mg.L-1 for the saline extract of the whole seed and 346.76 mg.L-1 for the saline extract of the seed without oil. The aqueous extract showed no toxicity even at the highest concentrations (400 to 600 mg.L-1). For the organism A. saline, none of the extracts proved toxic. In the tests performed with water treated with the extracts of M. oleifera, toxicity was found for D. magna in the supernatant fractions (EC50=296.02 mg.L-1) and sedimented (EC50=291.04 mg.L-1) of treated water with the saline extract of the whole seed. For the treated water with the saline extract of the seed without oil, was found toxicity in the supernatant fraction (EC50=351.17 mg.L-1) and the sedimented fraction (EC50=342.32 mg.L-1), which indicates that the toxicity of the extract is not reduced after coagulation/flocculation. In the chronic test performed using D. magna exposed during 21 days to the saline extract of the whole seed of M. oleifera, changes in the evaluated parameters (mortality, fertility and growth) were observed, and as higher the concentration tested, bigger was the toxicity. At the end of the 21 experimental days, there had been a 100% mortality of individuals exposed to higher concentrations (10 and 15 mg.L-1). Furthermore, there was wide variation in fertility between the groups. Based on these results, we can say that the use of high concentrations of the extract of M. oleifera (above 300 mg.L-1) can cause acute damage for D. magna. However in practice, the concentrations used of this coagulant are considerably smaller, ranging mainly between 50 and 150 mg.L-1, according to literature data. Likewise, the dilution that occur in the aquatic environment, hardly provide high concentration of the extract in the water bodies. Based on this, we can say that the use of the extract of M. oleifera can be encouraged, but if used with caution, avoiding high concentrations.

Um dos grandes desafios para a Ciência é buscar processos metodológicos que reflitam direta ou indiretamente no ambiente, diminuindo o impacto ao meio e ao mesmo tempo, proporcionando o desenvolvimento desses processos. A água é, atualmente, um desses desafios, principalmente quanto à disponibilidade e ao padrão de qualidade microbiológico e físico-químico para consumo. Por causa desta problemática, é que o trabalho teve como objetivo utilizar sementes de moringa para redução da turbidez, por apresentar um biocoagulante que apresenta vantagens, quando se compara com os coagulantes químicos. A água foi coletada no rio Capibaribe, no município de Recife, Pernambuco, Brasil. Os parâmetros físico-químicos como pH, condutividade elétrica e turbidez foram determinados antes (pH=8,11; CE=8,35 mS/cm; turbidez=16,62 NTU) e após o tratamento. As concentrações do pó da Moringa oleífera foram 0, 50, 100, 200, 250 e 300 mg/200mL de água, relacionados com tempo de contato correspondente a 0,1, 2, 4 e 6 horas, sendo estes ajustados pelo planejamento experimental DCCR. Após os ensaios, o resultado obtido na remoção de até 100 % da turbidez foi com a concentração de 200 mg, com o tempo de sedimentação de 2 horas, comprovando a eficiência do biocoagulante presente na semente da Moringa oleífera para a clarificação da água. Antes e após os tratamentos foram determinadas turbidez, pH e condutividade elétrica. Os resultados foram analisados pela tabela ANOVA e o gráfico de Pearson que representavam respectivamente um nível de significância de 5 % e correlação entre as variáveis. Verificou-se que o tempo de sedimentação e o pH apresentou correlação de 0,63; e de turbidez com pH foi de 0,49. Os resultados observados nas fotomicrografias eletrônicas de varredura indicam melhoria da biossorvência de partículas dissolvidas. / One of the greatest challenges for science is searching for methodological processes which reflect directly or indirectly in the environment, decreasing the environmental impact and at the same time, providing the development of these processes. Water is currently one of those challenges, especially with regard to the availability and the pattern of physical-chemical and microbiological quality for consumption. Because of this problem, is that the work aims using moringa seeds to reduce turbidity, by presenting a biological coagulant that has advantages, when compared with the chemical coagulants. The water was collected in the Capibaribe River, in the municipality of Recife, Pernambuco, Brazil. The physical and chemical parameters such as pH, electrical conductivity and turbidity were determined before (pH=8 .11; CE=8.35 mS/cm; turbidez= 16.62 NTU) and after treatment. The Moringa powder oleifera were 0, 50, 100, 200, 250 and 300 mg/200mL of water, related to contact time corresponding to 0.1, 2, 4, and 6:0, which are adjusted for planning experimental CCRD. After the tests, the result obtained in the removal of up to 100 of the turbidity was with the concentration of 200 mg, with the time of sedimentation 2:0, proving the efficiency of biological coagulant present in Moringa seed oleifera for clarifying the water. Before and after the treatments were determined turbidity, pH and electrical conductivity. The results were analyzed by ANOVA table and the chart of Pearson representing respectively a significance level of 5 and correlation between variables. It was found that the time of sedimentation and pH showed correlation of 0.63; turbidity and pH was 0.49. The results observed in the electronic scanning photomicrographs indicate improvement in the particle biological sorvente dissolved.