Abstract The chemical characteristics of spent wash, an effluent from the distillation of ethanol from molasses, can vary, depending on the initial feed stock and the operations of the factory. Spent wash from Australia contained large quantities of dissolved organic carbon (DOC), K, N and Cl with moderate to low concentrations of Ca, Mg, Na, and S, and small amounts of trace elements (Fe, Al, Mn, Cu, Zn). Spent wash from Thailand was obtained from whisky distillation and generally had similar chemical attributes to the spent wash from ethanol production, although the Zn concentration was much higher (399-974 mg Zn L-1). Large differences in EC and pH were found between Australian (pH: 4.08-4.49; EC: 40.4-42.2 dS m-1) and Thai spent wash (pH: 7.86-9.20; EC: 11.3-82.4 dS m-1). However, the high concentration of K in spent wash from both manufacturing processes indicates the unique chemical characteristic of wastewater produced from molasses-based distillation. While chemical characterisations of spent wash have shown its potential value as a fertilizer, its utility needs to be more practical than by direct application. This is due to its dilute nature, associated with the presence of organic carbon (OC) and nutrients in soluble form, thus making direct application susceptible to leaching losses of nutrients, especially in soils of low cation exchange capacity (CEC). It was hypothesized that capturing OC and nutrients on a high activity exchanger would overcome this problem. Since the charge on organic components in spent wash is important to the capturing process, pH manipulation is one of the major factors affecting the efficiency of this capture. The study of the influence of pH on development of charge on organic components in spent wash was undertaken using potentiometric titration. The potentiometric titration, and derived pH buffer curve, showed that the organic components in spent wash comprised a wide range of ionizable organic functional groups behaving like a mix of weak acids. While the inflection point (s) could not be obtained from the potentriometric titration, the absorbance of spent wash in the UV waveband (250 to 400 nm) confirmed the presence of phenolic groups in spent wash. The charge on organic components in spent wash was strongly pH dependent, and highest in the pH range of 4.0-5.0. The manipulation of pH and salt concentration (EC) was shown to have an effect on flocculation/dispersion and it is inferred that this was due to changes in the molecular arrangement of organic components in spent wash. A coiled configuration is suggested at acidic pH, whereas a linear flexible configuration and macromolecular structure tending to occur at neutral and alkaline pH respectively. Ca-saturated bentonite, originally sourced from Mantuan Downs, Central Queensland, was used in an investigation of the capture of OC and nutrients from Sarina spent wash at different pH values (4.5, 6.0, 8.0). This study demonstrated that manipulation of pH and electrolyte concentration had a small effect on adsorption of OC by the clay, probably the result of effects on the charge characteristics of both clay mineral surfaces and organic molecules and also on molecular sizes of the dissolved organic matter (DOM). The highest absorption of OC was only 28% for dewatered spent wash, suggesting Ca-saturated bentonite may not be a strong sorbent for DOM from a wastewater of high EC and which contains high concentration of DOC of the composition found in spent wash. The study of the adsorption of K by bentonite in a pure inorganic system (without DOM) indicated sufficiently high concentrations of K can compete with divalent Ca2+ for exchange sites on the clay surface. The adsorption of K in an organic system (the DOM component in spent wash) showed that DOM had a positive influence on adsorption of inorganic ions (e.g. K+). Characterisation of the spent wash/ clay mixture demonstrated its potential to be used as a soil ameliorant on the basis of the large quantity of OC and nutrients it contained (especially N and K). Wet and dry organic clays were produced and assessed as ameliorants in a glasshouse trial using forage oat (Avena sativa var. Coolobah) as test species. This pot study indicated a positive influence of application of either wet or dry organic clay on crop biomass at the high application rate (equivalent to 40 tonnes ha-1). The high proportional K recovery from this high application rate application suggests that organic clays can be used as K fertilizer. The crop nutrient uptake data also indicated its use as a source of S and Mn.

Submitted by Johnny Rodrigues (johnnyrodrigues@ufcg.edu.br) on 2018-09-30T14:07:04Z No. of bitstreams: 1 JOÃO BATISTA QUEIROZ DE CARVALHO - DISSERTAÇÃO PPGECA 1975..pdf: 23722015 bytes, checksum: 8472b04995abaef083f89dbe9bba109e (MD5) / Made available in DSpace on 2018-09-30T14:07:04Z (GMT). No. of bitstreams: 1 JOÃO BATISTA QUEIROZ DE CARVALHO - DISSERTAÇÃO PPGECA 1975..pdf: 23722015 bytes, checksum: 8472b04995abaef083f89dbe9bba109e (MD5) Previous issue date: 1975-03 / 0 propósito desta dissertação foi estudar "algumas propriedades físico-químicas e de engenharia de uma argila orgânica" que forma parte do subsolo da cidade do Recife. As "amostras indeformadas" foram retira das do subsolo pelo uso de tubos de parede fina sem costura conhecidos por tubos tipo "Shelby". Os resultados dos ensaios de laboratório foram obtidos com amostras retiradas ao longo da camada de argila orgânica com intervalos de 1,0 metro. Os ensaios, teor de umidade de campo, limites de Atterberg, análise granulométrica , área específica , pH, composição mineralógica, adensamento e triaxial não consolidado não drenado, permitiram não somente o estudo do solo em função da profundidade mas também sua caracterização. O estudo mostra que a homogeneidade e uniformidade da "argila orgânica" é provavelmente função da variação do teor de matéria orgânica. O solo é caracterizado como uma "argila orgânica" com baixo teor de matéria orgânica finalmente dividida, apresentando alta plasticidade, composta predominantemente do argilo-mineral caulinita, normalmente adensada e de baixa sensibilidade. Análise de regressão linear foi usada para explorar possíveis correlações entre os valores dos diferentes ensaios realizados. Isto mostra que, dentro das limitações do estudo, existem correlações entre os parâmetros medidos. Propõe-se que estas correlações sejam usadas preliminarmente para avaliar as propriedades de engenhar i d do solo estudado. / The purpose of this dissertation was to study some physico-chemical and engineering properties of an "organic clay" which forms part of the soil profile underlying the city of Recife. Undisturbed specimens were recovered from the subsoil by the use of seamless, thin walled steel tubes known as "Shelby type tubes". Results during the laboratory testing programme were obtained from specimens recovered at 1 m intervals along the depth of the organic clay strata. Field moisture content, Atterberg limits, grain size distribution, specific gravity, specific surface, pH, minera1ogica1 analysis, consolidation and unconsolidated undrained triaxiol tests allowed not only the study of the soil as a function of depth but its characterization as well. The study shows that the homogeneity and uniformity of the "organic clay" is probably a function of the variation of organic matter content.- The soil is characterized as a: "soft organic clay with traces of highly divided inactive organic matter, exhibiting high plasticity, composed predominantly of kaolinite cl y mineral, normally consolidated and of low sensitivity". Linear regression analysis was used to explore possible correlations between the values of the different tests carried out. It is shown that, within the limitations of the study, statistical relations do exist between the parameters measured. It is proposed that these correlations may be used for preliminary evaluation of the engineering properties of the soil studied.

Soft soil deposits of coastal regions and lowland areas pose many geotechnical problems but it is indispensable to utilize these grounds to meet the growing demand for infrastructure with ever increasing urbanization and industrial development. Soft soils are generally associated with high compressibility and low strength characteristics which augment the risk of huge settlements and foundation failure. It is essential to understand the complex behaviour of the ground consisting of soft clays as construction and maintenance of infrastructure in these areas is challenging. Marine sediments mostly possess open microstructure irrespective of the differences in their mineral composition and sedimentation environment. Also this particular microstructure in marine sediments is generally accompanied by the presence of a great amount of organic residues and fragments of marine organisms. Formation of pyrite is also possible because of the presence of decomposable organic matter, dissolved sulfate and reactive iron minerals. These soils due to their inherent mineralogy and microstructure have high void ratios and consequently high water holding capacity which explains the reason for their low shear strength and high compressibility characteristics. And often the formation environment is conducive for incorporation of organic content in the soft clay deposits which further aggravates the problem. A complete characterization of the soil can enhance the understanding of soil behavior and therefore can play a crucial role in suggesting suitable and sustainable ground improvement method. Soft clay deposits of Kuttanad area in Kerala, India extending to varying depths below the ground level, present a challenge as a foundation soil due to low bearing capacity and high settlement. Geologically Kuttanad is considered as a recent sedimentary formation. In the geological past, the entire area was a part of the Arabian Sea. Presently Kuttanad area covers an area of about 1,100 km2. Many intriguing reports of distresses to structures founded on this soil are available. An over view of specific characteristics of soft clays along with the comprehensive description of soft clays from various parts of the world is presented in the introductory Chapter. Deep soil mixing and mass stabilization methods are found to be relatively advantageous in reducing differential settlements and in achieving expeditious construction. A more detailed review of literature on Kuttanad soil problems and various ground improvement methods adopted are presented. The different ground improvement techniques attempted are soil reinforcement, stone columns, preloading etc. Soil mixing can be relatively advantageous over the other conventional ground improvement methods. Laboratory studies carried out earlier with different binders such as cement, lime and lime fly ash combinations did not exhibit appreciable improvement in soil strength. It is reasoned that the lack of understanding of the soil characteristics is responsible for the limited success of these attempts. Based on the review of literature the detailed scope of the work is presented at the end of Chapter 1. The method of collection of the soil from Kuttanad region, methods adopted for characterization of soil, characteristics of various binders used and testing procedures adopted for assessing the geotechnical behavior with and without binders are described in Chapter 2. In order to characterize the soil for understanding its behaviour under different conditions as well as to gauge its response to different stabilizers, a detailed physico¬chemical, mineralogical, morphological and fabric studies are carried out and presented in Chapter 3. An attempt has been made to explain the role of components of soils such as organic substances, pyrite and sesquioxides for variations in its properties with change in water content. The high water holding capacity of the soil reflected in its Liquid limit along with relatively low plasticity characteristics of the soil has been explained as due to the presence of minerals such as metahalloysite and gibbsite, the flocculated fabric, porous organic matter and water filled diatom frustules (amorphous silica). Based on the study conducted on the plasticity characteristics of Kuttanad soil under different conditions of drying and treatment, it was brought about that the organic content plays a dominant role in particle cementation and aggregation causing a substantial reduction in plasticity upon drying. Further, the presence of minerals such as pyrite and iron oxides also account for the plasticity changes. The significant changes in soil properties upon drying have also been successfully explained in Chapter 4. Attempts made to stabilize the soil using conventional chemical stabilizers are described in Chapter 5. The effect of binders on the strength improvement of soil has been explained based on the changes occurring in the composition, fabric and physico-chemical characteristics of soil upon addition of the binders. Lack of strength development in soil with lime has been attributed to the inherent composition of the soil hindering the formation of pozzolanic compounds and unfavourable modification of the fabric. On the other hand the soil responded well to cement stabilisation. The influence of various parameters such as Water/Cement (W/C) ratio, Initial water content, curing period and additive dosage on the strength development of cement treated soil has been examined. Cement improved the strength of the soil by binding the soil particles without depending on the interaction with the soil. It was observed that the role of initial water content is insignificant and the strength improved with reducing W/C ratio. The dependence of strength development with cement addition on the fabric at different W/C ratios has been assessed. Also the role of other additives such as Lime, Sand, Fly Ash, Ground granulated blast furnace slag, Silica fume and Sodium silicate to enhance the strength of cement treated soil has been analysed in Chapter 5. It was shown that only Sodium Silicate (NS) along with cement meets with good success. The studies on the undrained shear strength and compressibility characteristics of cemented soil carried out to understand the strength and deformation behaviour of the cemented soil are presented in Chapter 6. It is clear from the compressibility characteristics of the cemented soil that there is a well defined yield stress demarcating the least compressible pre-yield zone and more compressible post yield zone. Generally the yield stress increases with reducing water cement ratio. It is interesting to note that the post yield compressibility of the cemented soil is controlled more by the fabric of soil than by cementation effect. The study on the undrained shear behavior of cemented soil revealed that the cohesion intercept and angle of internal friction increases with addition of cement. However the impact of cementation is reflected more as increase in cohesion intercept with increasing cement content. The uniqueness of failure envelope observed for the cemented soil irrespective of whether the confining stress is above or below the yield stress has been explained in detail. A case study on the performance of embankment founded on Kuttand soil improved with Deep mixed cement columns (DMCC) has been evaluated through numerical simulations using FLAC 2D and this forms the subject matter of Chapter 7. For this work the soil properties of the Kuttanad soil determined by experimental investigations have been used. The simulation results showed that the introduction of DMCC columns improved the factor of safety against failure and reduced settlements. This study clearly endorses the analysis and the results of the test carried out on Kuttanad soil. The final chapter summarizes the details of the work carried out which brings out the importance of characterization of the soil in terms of soil components, physico-chemical environment as well as the micro structure of the soil in predicting the behaviour of the soil in changing environment and to understand the stabilization response of the soil with different binders which intern helps to select appropriate binder and or binder combinations.