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This thesis contains the results and discussion of an exploratory investigation into the application of Crossflow Microfiltration (CFMF) for solid/liquid separation in biological wastewater treatment systems. The principal objective of the study was to assess the influence of CFMF on the performance of identified biological wastewater treatment systems. It was not the objective to optimise filtration performance. A literature review indicated that the crossflow mode of filtration has been widely accepted as a unit operation in the fermentation industry. The filtration mode is now being applied not only for solid/liquid separation but also for separations on a molecular and ionic level. Very few applications of crossflow filtration in the context of biological wastewater treatment solid/liquid separation are reported in the literature. The reasons for this limited experience would appear to be the scale involved and the perceived high costs; separations in the fermentation industry are usually conducted at relatively small scale (laboratory or pilot-scale) and involve high-value products, justifying high capital and operating costs. Also, the high level of separation performance attained is perhaps not necessary for many wastewater treatment applications. No doubt these reservations are largely valid. However, these arguments cannot be applied equally to all filtration methods and wastewater treatment schemes. For example, the costs of microfiltration are substantially less than ultrafiltration or reverse osmosis, and in certain cases effluents with extremely low suspended solids contents may be required. In the light of these observations an investigation of CFMF for solid/liquid separation in biological wastewater treatment systems appears justified. Two biological treatment systems were selected for study: the Upflow Anaerobic Sludge Bed (UASB) reactor and the Activated Sludge system. The envisaged benefits accruing from the application of CFMF were different in each case.

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The possible effect of oxidation [processing with or without sulfur dioxide (±S0₂)] and of pre-ultrafiltration treatment of juices with enzymes and fining agents on flux, and on juice color, composition and stability was investigated. White Riesling juice was ultrafiltered with a Romicon system operated with a nominal molecular weight cut-off (MWCO) of 10,000 daltons. In addition, UF White Riesling juices processed ±S0₂, were stored for 2 months (1985 vintage) and 12 months (1984 vintage) at 2°C and 20°C, and evaluated by a trained panel using descriptive analysis. Pre-UF treatment with enzymes and fining increased flux. Sediment formation and instability to heat testing of UF permeates processed -S0₂ was prevented with pre-fining. Up to 99% of protein, 90% of pectin, 84% of color and low variable phenolics were retained by the membrane of 10,000 dalton MWCO. During UF there is a significant increase in the soluble protein and water soluble pectin passing through the membrane with increasing volume concentration ratio (VCR, process time). It is concluded that it is not only the amount but the nature/state of compounds such as proteins, phenolics, pectins, and their interaction that results in instability. UF juices processed with minimum oxidation and stored for 12 months had lower intensity aroma (apple/apple cider, sweet, and honey/caramel) and overall intensity flavor by mouth descriptors than those processed with oxidation. Moreover, juices processed with minimum oxidation and stored for two months (1985 vintage) had significantly lower intensity of apple/apple cider, sweet, honey/caramel aroma descriptors when compared to those processed with oxidation. There was no effect of temperature of storage on any of the aroma and flavor-by-mouth descriptors for the 1985 juice after two months of storage. Only one aroma descriptor (vegetative) was significantly increased for the 1984 White Riesling juice after 12 months at 2°C. This indicates the possibility that UF juices may be stored at higher temperature (20°C) for less cost with minimal changes in aroma and flavor. White Riesling (WR) and Gewurztraminer (GEW) wines were ultrafiltered with Romicon and Millipore pilot-scale systems, respectively. The effect of ultrafiltration (UF), membrane MWCO from 10,000-50,000 daltons, and of VCR on composition and wine stability was investigated. The effect of 1) pilot-scale UF processing and Bentonite fining on WR and GEW wines, and 2) commercial-scale UF processing on GEW wine was sensorially evaluated by a trained panel using descriptive analysis. UF processing significantly reduced color (A [subscript 420nm]), total phenol, protein and heat/cold test (HOT) haze of both WR and GEW wines. Stability to HOT haze formation was obtainable with MWCO of 10,000 daltons, but trace instability can remain. With increasing VCR (process time) there was a significant decrease in membrane retention of color (A [subscript 420nm]), protein, and HCT haze formation in the WR wine and the color (A [subscript 420nm]) of the GEW wine. UF processing of the WR wine significantly decreased the perception of overall aroma intensity, fruity, fresh fruity citrus, floral, sweet and honey/caramel character but it also increased the intensity of the vegetative aroma descriptor when compared to the control unfiltered WR wine. In addition, significant differences were detected for these descriptors between the bentonite-fined WR wine and the ultrafiltered WR wine except for fresh fruity citrus and honey/caramel which were less intense in the ultrafiltered WR ultrafiltered WR wine. UF processing of GEW wine significantly decreased the intensity of fruity, fresh fruity aroma descriptors; and increased the chemical aroma descriptor compared to the control unfiltered GEW wine. However, no significant differences were detected for these descriptors between the bentonite fined GEW wine and the ultrafiltered GEW wine except for fresh fruity which was less intense in the ultrafiltered GEW wine. Commercial processing of GEW wine by UF did not have any significant effect on the aroma and flavor by mouth descriptors evaluated as compared to standard processing procedures. / Graduation date: 1988

Soil and grass filtration of a domestic sewage effluent for trace element removal was investigated by applying oxidation-pond-treated waste water to twelve 2.44-meter-long, 30.5-cm-diameter, lysimeter columns and to a half-acre plot planted to common bermudagrass. Bermudagrass was also planted on the soil columns to aid in the removal of accumulated metals, thus prolonging the filtering capacity of the soil system. Four irrigation patterns, continuous flooding, alternate day flooding, one day wet-three days dry cycles and two days wet-five days dry cycles, were employed during the eleven week lysimeter test. Water samples were extracted from the soil columns at eight sampling depths to determine the soil depth at which the various trace metals were removed from the filtrate by the processes of adsorption, absorption and biological assimilation. Atomic absorption spectrophotometric techniques were used to determine the concentrations of iron, manganese, hexavalent chromium, nickel, copper, zinc, lead, cadmium, cobalt and strontium in the applied effluent, filtrate, soil and grass clippings. Filtrate samples for trace metal analysis were also extracted at shallow depths and from two groundwater zones at 9.1 and 15.2 meters depth under the grass plot. In the lysimeter study, iron, manganese, nickel, copper, zinc, lead and cadmium were removed from the filtrate at, or near, the soil surface. Some copper, zinc and cobalt were found in the deeper filtrate samples during periods of high infiltration rates and in the presence of anaerobic conditions. Smaller amounts of manganese, nickel and lead were also found at the deeper sampling points. Strontium was not removed from the water percolating through the calcareous soil employed in this study. Chromium and cobalt were not present in measurable quantities in the applied effluent. Iron and manganese were removed from the soil system in the grass clippings in the greatest amounts. Traces of copper, zinc and cadmium were also detected in the grass clippings. Larger quantities of iron, manganese and copper were detected in the filtrate at the grass plot than at comparable depths of the lysimeter columns, probably due to effluent applications at the grass plot over a period of two years. Lower quantities of nickel and lead in the filtrate at the grass plot were attributed to leaching by effluent during grass filtration tests, prior to the trace metal experiments. The concentrations of trace metals in the filtrate at the bottom of the lysimeter columns and in the groundwater zones at the grass plot were irsignificant by United States Public Health Service drinking water standards (1962) and would meet most other water supply requirements. The total nitrogen and nitrate contents were successfully reduced when a combination of aerobic and anaerobic environments were present in the soil system. Total nitrogen and nitrate levels were not reduced by grass filtration through 304.8 meters of dense grass. Fewer total coliform organisms were detected in the aerobic lysimeter columns than in the continuously flooded columns. The majority of coliform organisms detected in the filtrate at the 61 cm depth were believed to be of non-fecal origin. The chemical oxygen demand of the applied effluent was reduced to as low as 105 mg/L by grass filtration. A substantial portion of the remaining COD was attributed to high algal concentrations. The most effective treatment employed in this study was the one day wet-three days dry irrigation cycles. This treatment provided the necessary aerobic environment for trace metal removal from the effluent, nitrification of reduced nitrogen compounds and coliform organism elimination. The flooding period provided the anaerobic conditions required for denitrification losses of nitrate.

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