The objective of this work was to develop a continuous immobilized cell reactor system for the high rate production of ammonium lactate using deproteinized whey as a substrate. Further that this system should use techniques other than membranes to retain cells. The fermentation was carried out using a mixed culture of homofermentative thermophilic lactic acid bacteria selected by an enrichment technique. Immobilization was achieved by retaining the culture as a slime-film supported on a needle-punched polyester fabric, placed as a pleated tube in a column reactor. Flocculation was used to obtain further improvements in biomass retention. Two reactors of volume 0.2 litres were used for most of the experiments. The height to diameter ratios of these reactors were 2.2 and 7.3. The latter was designed to encourage flocculation and the diameter at the top was slightly larger, than at the bottom. The pH was continuously controlled by the addition of ammonium lactate. The influences of temperature, pH, residence time and yeast extract (added to the feed) were studied. When both methods of hold up were combined acid productivities up to 18 kg/m<SUP>3</SUP>/hr at a conversion rate of 0.95 could be obtained. The system was operated for up to 850 hours without a deterioration in performance.

The use of antifoam solution to control any foaming tendency is a very important aspect of fermentation processes. However, an antifoam solution will affect the mass transfer characteristics of a fermentation broth as well as suppressing foam so that both mass transfer and foam behaviour have been studied in the present work. The behaviour of a transient foam, which is produced by the antifoam itself, was investigated by means of a small two-dimensional bubble column. This bubble column consisted of two glass plates separated by a 10 mm thick frame of PTFE. Bubbles were produced from sintered-glass spargers of two pore sizes. Measurements of the average bubble diameters in the foam for different concentrations of solution were carried out from still photographs of the foam using an image analyzer. Two types of antifoams were investigated, polypropylene glycol (PPG) and a silicone oil emulsion. The two PPG concentrations used were 0.05 and 0.15 g/l both with and without adjustment of the pH and the addition of an electrolyte, NaCl. The silicon emulsion concentration was 0.015 g/l. Bovine serum albumen BSA as a foaming agent at a concentration of 0.20 g/l was investigated by itself, and with each of the antifoams. In each experiment, the height of foam layer was recorded as a function of the superficial gas velocity. A constant flow tank has been designed to allow the foam to overflow and to enable measurements of the mass transfer characteristics of the froth (or broth) layer only. These characteristics are: volumetric mass transfer coefficient <I>K<SUB>L</SUB>A</I>, Sauter mean bubble diameter <I><SUB>b</SUB></I>, gas hold-up <I><SUB>g</SUB></I>, interfacial area <I>A</I>, and mass transfer coefficient <I>K<SUB>L</SUB></I>. The value of <I>K<SUB>L</SUB>A</I> was calculated from a mass balance of steady-state dissolved oxygen. The gas hold-up was estimated from the differences in heights of gassed and ungassed solution. A photographic technique was applied to measure the bubble diameter. Thus, the interfacial area <I>A</I> was simply calculated using the formula (<I>A </I>= <I>6</I> <SUB>g</SUB> /<I> </I><SUB>b</SUB>). Finally, the value of <I>K<SUB>L</SUB></I> value was determined.

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The research was mainly concerned with performance analysis in seawater reverse osmosis desalination at the Addur SWRO Desalination Plant, Kingdom of Bahrain; there were four main objectives associated with the research. The first objective was conducting a process performance analysis of the conventional pre-treatment system at the Addur Plant so as to determine its filtration efficiency (Chapter 4). The analysis involved assessment of principal filtration parameters like temperature, silt density index (SDI) and turbidity for one seasonal year (with reference to total organic carbon (TOC), ultra violet absorbance (UVA), humic acids substances (HAS) and total suspended solids (TSS) that reflect the fouling potential of organic matter in the seawater feed). Through the evaluation of these parameters' time varying profile trends, specific key aspects were acknowledged. It was established that the incoming seawater quality is characterised as complex and most difficult seawater feed utilised for seawater RO desalination and confirmed that the , pre-treatment was unable to meeting its design performance parameters (i.e. reduce the raw seawater SDI to 2.7 and remove organic matter). Seeping of various undesirable matter through the pre-treatment was verified through EDX analysis suggesting filtration channelling. A system shortfall in the pre-treatment process was conclusive. It was a~so recognised from the profile trends that SDI and turbidity were influenced by seawater . temperature, as micro-organisms flourish within high temperature regions. The second objective was carrying out comprehensive performance analyses on three leading RO membrane modules in seawater desalination tested at similar seasonal conditions and seawater feed composition (Chapter 5) through which the most suitable module that withstood the harsh operation conditions was selected to replace the existing membrane modules at the Addur Plant (where the design aspects and operating guidelines for the three modules were also reviewed in Chapter 3). The results demonstrated that Toyobo CTA HF was best suitable and FilmTec spiral wound PA composite proven second suitable while the performance operation and endurance of DuPont HFF PA was not acceptable. both did not exactly correlate to one another owing to the unavailability of the salt concentration in the vicinity of the membrane wall during the actual RO process. In the second model variations in water and salt transport within a seawater RO module during RO were established in terms of flow, pressure and seawater feed concentration traversing through the module. Fundamental parameters to seawater RO processes were determined such as pure water permeability constant (A), mole fraction of concentrated boundary solution (XA2), solute transport parameter ((DAwKO)sw), mass transfer coefficient for seawater on the high pressure side of the membrane (ks»1, concentration polarisation modulus (M) and thickness of concentrated boundary solution (I). All these quantities are unique and not before determined for real seawater RO systems. The third modelling analysis was concerned with developing a mathematical model defining spatial variations in key parameters ofthe seawater feed entering and traversing through the RO module; this was performed in terms of seawater feed temperature,. volumetric permeate flow rate (and related velocity) and the volumetric flow rate, pressure and concentration of solutions on the high pressure side of the membrane during RO separation. The results achieved through this research have been of primary significance to the development of the pre-treatment and seawater RO process operations and systems at the Addur SWRO Desalination Plant while the consequences of the solutio.ns recommended henceforth had reshaped the configuration of the plant, enhanced production and ensured availability and reliability.

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