Thesis (M.S.)--Wisconsin. / Includes bibliographical references (leaves 86-90).

No description available.

Plasma cleaning is the most effective dry process to remove surface contaminates from a SAW (Surface Acoustical Wave) device. Consistent gas pressures, flows, and good electrical connections between the chamber shelves are necessary for the process to function predictably. In addition, operation of the monitoring system must be transparent to the plasma cleaning unit. This thesis describes a simple solution to the complex problem of monitoring a plasma cleaning system. The monitoring system uses the LabVIEW® G programming language and hardware, both products of National Instruments, Inc.®, to monitor critical parameters necessary to achieve a consistent process when cleaning these devices.

No description available.

Purging compounds allow for rapid colour and material changes in plastics converting machines. They have both a cleaning and a purging action. The cleaning action refers to the removal of contaminants, e.g. carbon deposits, from the die, barrel and extruder-screw surfaces. This mechanism relies on conventional detergency in combination with high wall shear stresses. The purging action refers to the observed narrowing in the residence time distribution and is less well understood. The action of a purge compound may encompass both the cleaning and purging mechanisms in order to achieve the desired effect. In industry the effectiveness of a purge is determined by a visual observation of the extrudate. Therefore, a scientific method was required to quantitatively determine the efficiency of each purging mechanism under a set of fixed experimental conditions. In this study, a method was developed using a laboratory film-blower, which made use of a phthalocyanine blue pigment to impart colour to the film produced. The method was used to test the efficiency of various commercial purge compounds in switching the colour of film from blue to clear. The analysis was achieved by measuring the residual pigment concentration in the blue polymer film using a UV -Visible spectrophotometer. Commercial purge compounds function by means of various mechanisms such as filler abrasion, solvent dissolution, the dislodging of deposits with the aid of surfactants, etc. This study also considered the use of slip additives as an additional purging mechanism. In proposing that slip additives can contribute to a purging action, several slip additives where tested in polyethylene (PE), polypropylene (PP) and acrylonitrile butadiene styrene (ABS). The slip additives polypropylene wax and polyamide showed a significant increase in the MFI of PE whereas the additives polar wax and polyamide exhibited a slight increase in MFI of PP. Three additives, namely, polyamide, polypropylene wax and polar wax had showed noticeable improvement on the MFI of ABS. The slip additives that showed a significant improvement in polyethylene were tested together with six different commercial purge compounds. These compounds were tested for their colour change efficiency using polyethylene and switching from blue to clear in a laboratory film blower. It was found that the slip mechanism contributes very little to the purging action. Polymeric materials tend to adhere to hot metal surfaces. When the material continues to adhere to the metal after cooling down, cleaning of the processing equipment becomes very difficult. A purge manufactured by the CSIR, Pretoria, exhibited this problem. This study also covers an investigation into overcoming the adhesion problem of this purging compound. / Dissertation (MSc (Chemistry))--University of Pretoria, 2006. / Chemistry / unrestricted

One of most major concerns from both cost-effective and technical point of view in membrane process industry is membrane cleaning. The aim of the project was to investigate the variations in membrane surface properties and separation efficiency of reverse osmosis membrane. Compativtive analysis have to be performed on four RO membrane before and after exposing the virgin membrane into chemical cleaning to identify and analysis the impact of the chemical cleaning on the performance of RO membrane. Commerical chemical cleaning used in this project were caustic and acidic cleaning agent. The project’s aim is the investigation of simulation software’s precision for the four membranes performance projection at different conditions of the feed water. The assessment of the membranes performance was done in the Innovation Cluster at pilot plant that was industrial in size. The main commercial elements used were the thin-film composite membranes with a spiral-wound of 8-inch polyamide. Ultrafiltration (UF) and seawater RO membrane pretreatment process was done for the red sea sourced feed water. A pressure vessel dimensioned at 8-inch was operated in conjunction with an individual element at 8 -20 m3/hr feed flow rate, with an 8 to 12 % recovery and an average 35,000-42,000 mg/L of total dissolved solids (TDS) composition for the feed water. To achieve the project’s aim in assessing the membranes, three phase experimental stages were completed. The membranes performance was assessed in terms of their water flux, salt rejection, boron rejection, bicarbonate rejection and permeate quality. In addition, the membrane surfaces were characterized after exposing the fresh membranes with a chemical cleaning reagent. The experimental results showed an increase in both permeate flow and salt passage for all studied elements. The changes in the membranes performance were systematically explained based on the changes in the charge density and chemical structure of the membranes surface. The experimental results showed that both the physical and chemical surface properties of the membranes do not significantly alter under standard industrial conditions. These results shed some light on the effects of chemical cleaning in a pilot-scale RO plant and improve our understanding to provide a potential research direction for cleaning methods of membranes.

Anaerobic membrane bioreactors (AnMBR) have been established as an efficient method of wastewater treatment to obtain high-quality effluent with low energy consumption. However, membrane fouling leading to flux reduction and an increase in operational costs can negate potential benefits associated with AnMBR. Today’s conventional membrane cleaning process includes physical and chemical approaches, both of which have their own drawback. For this reason, the biological approach was proposed as an alternative to dangerous, energy-consuming, and environmentally unsafe treatment techniques. The combination of UV-C and bacteriophage offers an alternative chemical-free approach for biofouling control. This dissertation aims to test the different order of using UV-C and bacteriophage to clean anaerobic membrane. This dissertation also demonstrates a proof-of-concept to achieve semi-online cleaning using UV-C and bacteriophage, thus increasing the feasibility of described technology. As a result of this work, it was shown that preliminary UV exposure enhances bacteriophage propagation into thick biofilms, and that the bacteriophages are able to affect total cell number and extracellular polymeric substances (EPS) compared to the control. Compared to the control, the semi-online cleaning strategy also resulted in a membrane that took a longer time for the transmembrane pressure to increase in the next operation cycle after cleaning.

Increasing demand for fresh water in arid and semi-arid areas, similar to the Middle East, pushed for the use of seawater desalination techniques to augment freshwater. Seawater Reverse Osmosis (SWRO) is one of the techniques that have been commonly used due to its cost effectiveness. Recently, the use of Ultrafiltration (UF) was recommended as an effective pretreatment for SWRO membranes, as opposed to conventional methods (i.e. sand filtration). During UF operation, intermittent cleaning is required to remove particles and contaminants from the membrane's surface and pores. The different cleaning steps consume chemicals and portion of the product water, resulting in a decrease in the overall effectiveness of the process and hence an increase in the production cost. This research focused on increasing the plant's efficiency through optimizing the cleaning protocol without jeopardizing the effectiveness of the cleaning process. For that purpose, the design of experiment (DOE) focused on testing different combinations of these cleaning steps while all other parameters (such as filtration flux or backwash flux) remained constant. The only chemical used was NaOCI during the end of each experiment to restore the trans-membrane pressure (TMP) to its original state. Two trains of Dow™ Ultrafiltration SFP-2880 were run in parallel for this study. The first train (named UF1) was kept at the manufacturer's recommended cleaning steps and frequencies, while the second train (named UF2) was varied according to the DOE. The normalized final TMP was compared to the normalized initial TMP to measure the fouling rate of the membrane at the end of each experiment. The research was supported by laboratory analysis to investigate the cause of the error in the data by analyzing water samples collected at different locations. Visual inspection on the results from the control unit showed that the data cannot be reproduced with the current feed water quality. Statistical analysis using SAS JMP® was performed on the data obtained from UF2 determined that the error in the data was too significant, accounting for 42%. Laboratory inspection on water samples concluded that the water quality feeding to the UF membranes was worse than that of the raw water. This led to a conclusion that severe contamination occurred within the main feed tank where the water was retained before arriving to the UF modules. The type of contamination present in the feed tank is yet to be investigated. Though, frequent cleaning or flushing of the feed tank is recommended on regular basis.

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Call number: LD2668 .T4 1963 S94 / Master of Science