The effects of four oxidants upon water treatment process parameters were investigated. The four oxidants under consideration were ozone, chlorine dioxide, potassium permanganate, and chlorine, Experimentation was directed towards the impact of these oxidants upon turbidity, TOC, and color removal, as well as reduced manganese oxidation. Studies were conducted with an experimental water with enhanced TOC levels. Experimentation was accomplished by a series of jar tests in which solution pH, coagulant dose, and oxidant dose were varied. Results show that, in general, oxidant application had either no impact or a negative impact upon TOC, turbidity, and color removal. Further deterioration of finished water quality was observed with increasing oxidant dose. Reduced manganese was oxidized by both potassium permanganate and chlorine dioxide. Ozone effectively oxidized reduced manganese in waters of low TOC, while chlorine was an ineffectual oxidant. Additionally, particle counts were conducted. Results show that the application of an oxidant increased the number of smaller particles present alter settling However, this immense of particles did not significantly alter settled turbidity levels. / Master of Science

Use of dye sensitized photooxidation is potentially a low cost means of degrading many of the hazardous compounds found in wastewaters. This study investigated the use of methylene blue as a sensitizer to degrade ortho-, meta-, and para-cresol, carbofuran and acrylonitrile. Significant reductions were found when aqueous solutions of the cresol isomers and carbofuran were illuminated and aerated in the presence of methylene blue. An average of 78% reduction of cresol was observed in seven hours. Carbofuran showed an average percent reduction of 56% in two hours. No loss was observed when the dye was absent. Acrylonitrile was found to be volatile and was stripped from solution by aeration. / M.S.

This problem was undertaken to determine the potentialities of chlorine dioxide as an algaecide and as an agent for the removal of tastes and odors from fresh water.

Yes / Fly ash is a toxic industrial waste, mainly consisting of silica and alumina particles, that has been found discharged into the environment. It is proposed that alginate, a naturally occurring biopolymer, can bind to these minerals and thus play a role in water purification. The binding forces involved in this process consist of weak interactions, such as van der Waals forces and electrostatic interactions. Although the attachment of alginate to mineral surfaces is mainly governed by its carboxylate groups, hydroxyl moieties could play a role in the interaction between the polymer and minerals. This work aims to use the SiO2 and Al2O3 particles as models for fly ash and to show the use of alginate biopolymers (fluorescently labelled with an aminonaphthaline sulfonate fluorophore (AmNS)) to coagulate them. The addition of simple electrolytes like NaCl and CaCl2 encourages the coiling of the polymer chain at high pH values which has an effect on its capability to bind to the inorganic particles. A combination of fluorescence and ICP-MS demonstrated that alginate has a considerable adsorption affinity for Al2O3, whereas it attracts SiO2 weakly. The adsorption process is pH dependent: strong adsorption was observed at low pH values. The dependence of adsorption on the mineral (Al2O3 and SiO2) concentration was also examined under different pH conditions: the adsorption amount was observed to increase by increasing the solid concentration. Adsorption isotherms obtained at low and high mineral concentrations were found to be Henry in type.

The use of ozone in a recirculating aquacultural production system on a commercial scale was investigated. ozonation was responsible for statistically significant differences in all test parameters, including: heterotrophic plate count, total coliforms, fecal coliforms, total solids, and total volatile solids. Results indicated ozone had a significantly positive effect in the recirculating aquacultural production system. Further study is recommended, however, to better understand the effects of ozone and to justify economically the use of ozone in commercial systems. / Master of Science

No description available.

This study investigated the effectiveness of vegetative filter strips (VFS) in removing phosphorus from surface runoff. Dissolved and particulate nutrients were treated separately due to differing transport and removal mechanisms. Nutrient transport in VFS appears to be a function of runoff rate, concentration and size distribution of suspended solids, and biological factors that influence hydrologic and chemical processes in filter strips. Three sets of experimental field plots were constructed to simulate VFS. Each set consisted of three plots containing sediment and nutrient source areas and 0.0, 4.6, or 9.1 m grass filter strips. Artificial rainfall was applied to the plots, and surface runoff, soil, and plant material samples were collected and physically and chemically analyzed. The VFS reduced surface runoff, suspended solids, and phosphorus losses. Most removal of sediment and phosphorus was accomplished in the first few meters of the VFS. The filter strips did not remove phosphorus as effectively as sediment, due to their ineffectiveness for filtering dissolved phosphorus and sediment-bound phosphorus associated with fine particles. The VFS often increased orthophosphorus losses in surface runoff. Laboratory batch experiments of phosph~rus desorption reaction suggested that plant residues, living plant canopy, and soil components of the strips could release dissolved phosphorus to surface runoff. A modified Elovich equation and a diffusion-control model were used to describe the phosphorus release from the plant and soil materials. A computer model, GRAPH, was developed to simulate phosphorus transport in VFS by incorporating phosphorus transport submodels into the VFS model in SEDIMOT II, a stormwater and sediment transport model. The model considers the effects of advection processes, infiltration, biological uptake, phosphorus desorption from the soil surface to runoff, the adsorption of dissolved phosphorus to suspended solids in runoff, and the effects of dynamic changes in the sediment size distribution on chemical transport. GRAPH was verified using the results of the physical plot simulations. The model's predictions and observed phosphorus transport compared favorably. Sensitivity analysis suggested that sediment and phosphorus removal was sensitive to the input parameters in the order: filter length and width, grass spacing, and filter slope and surface roughness. Increased filter width and length and aboveground biomass increased orthophosphorus loss from VFS. / Ph. D.

Microbial immobilization of soluble zinc (ZnSO₄ ) as ZnS was investigated to reduce the possible hazardous effects of soluble Zn in aquatic systems. Static three-phase microcosms were designed to simulate certain characteristics of natural systems in the laboratory. Microcosms (40, 15, 15 cm in length, width and height, respectively) contained water and sediments collected from a stream which had received metal-rich fly ash effluent from a coal burning power plant. To enhance sulfide production by sulfate reducing bacteria, an organic carbon source (1% cellulose g^-1 dry sediment) and 200 ppm sulfate were added into the microcosms. The rates of microbial respiration were determined by the analyses of carbon dioxide, oxygen, methane and hydrogen sulfide in the head space and water using gas chromatography. Selective chemical leaching techniques were applied to determine the fate of the added Zn as ZnSO₄ in the sediments using atomic absorption spectroscopy. Cellulose amendment resulted in elevated RQ values (M CO₂/M O₂ ) and strongly reduced sediments. Greater volatile sulfide production was observed in these cellulose amended microcosms. The absolute amount of Zn as ZnS in reduced microcosms was significantly greater (p<0.01) than that of non-cellulose amended controls. The amount of Zn as ZnS accented for over 90% when a sufficient amount of sulfate was present. When sulfate limitation was observed, however, the amount of Zn as ZnS accounted for approximately 50% of the total Zn in the sediments. The rest of the added Zn which could not bind with sulfide was mostly recovered as a loosely-bound exchangeable Zn. These results suggest that the addition of a suitable organic carbon source into the fly ash effluent receiving stream would remove soluble Zn from water and consequent precipitation of insoluble ZnS in the sediments. / M.S.

Thesis submitted in fulfillment of the academic requirement for the degree of (M.Tech.: Chemical Engineering), Durban University of Technology, South Africa, Durban, 2015. / Woven Fibre Microfiltration (WFMF) membranes have several advantages over its competitors with respect to durability, making it a favourable alternative for the developing world and operation during rough conditions. Wide application of membrane technology has been limited by membrane fouling. The durability of the WFMF membrane allows more options for flux enhancement and cleaning methods that can be used with the membranes even if they are vigorous. Therefore, the purpose of this work was to develop and evaluate flux enhancement and cleaning strategies for WFMF membranes. Feed samples with high contents of organics and turbidity were required for the study. Based on this, two rivers which are Umkomaasi and Duzi River were identified to satisfy these criteria. A synthetic feed with similar fouling characteristics as the two river water was prepared and used for this study. The synthetic feed solution was made up of 2 g/ℓ of river clay in tap water and 0.5% domestic sewerage was added into the solution accounting for 2% of the total volume. A membrane filtration unit was used for this study. The unit consisted of a pack of five membrane modules which were fully immersed into a 100 litres filtration tank. The system was operated under gravity and the level in the filtration tank was kept constant by a level float. The study focused on evaluating the performance of the woven fibre membrane filtration unit with respect to its fouling propensity to different feed samples. It also evaluated and developed flux enhancement and cleaning strategies and flux restoration after fouling. The results were compared to a base case for flux enhancement and pure water fluxes for cleaning. The WFMF membrane was found to be prone to both internal and external fouling when used in the treatment of raw water (synthetic feed). Internal fouling was found to occur quickly in the first few minutes of filtration and it was the major contributor for the loss of flux from the WFMF membrane. The fouling mechanism responsible for internal fouling was found to be largely pore blocking and pore narrowing due to particle adsorption on/in the membrane pores. The structure (pore size, material and surface layout) of the WFMF membrane was found to be the main cause that made it prone to internal fouling. The IV major fouling of the WFMF membrane was due to internal fouling, a high aeration rate of 30 ℓ/min had minimal effect on the fouling reduction. An aeration rate of 30 ℓ/min improved the average flux by only 36%, where a combination of intermittent backwashing with brushing and intermittent backwashing with aeration (aeration during backwashing only) improved average flux by 187% and 135% respectively. Pre-coating the WFMF membrane with lime reduced the effects of pore plugging and particle adsorption on the membrane and improved the average flux by 66%. The cleaning strategies that were most successful in pure water flux (PWF) recovery were high pressure cleaning and a combination of soaking and brushing the membrane in a 0.1% NaOCl (desired) solution. PWF recovery by these two methods was 97% and 95% respectively. Based on these findings, it was concluded that the WFMF membrane is susceptible to pore plugging by colloidal material and adsorption/attachment by microbiological contaminants which took effect in the first hour of filtration. This led to a 50% loss in flux. Also, a single flux enhancement strategy proved insufficient to maintain a high flux successfully. Therefore, combined flux enhancement strategies yielded the best results.

Submitted in fulfillment of the requirements of the degree of Master of Engineering: Chemical Engineering, Durban University of Technology, Durban, South Africa, 2016. / River water is a life supporting watercourse to most communities in rural areas. It is used for both human and animal consumption, and is well becoming a collection channel for defecation and urination due to shortage or lack of access to running water and sanitation facilities. This has resulted to the contamination of water sources, which poses a great risk to human health. This has motivated researchers to study simple but yet robust systems to produce safe drinking water. Photocatalysis is one of such emerging disinfection technologies. Titanium dioxide (TiO2) which is one of the basic materials used for paint manufacturing has emerged as an excellent photocatalyst material for water purification. TiO2 was selected in this study because it is locally available with a potential to open a new market in water purification for the manufacturers. The setback in previous studies is the recovery of nano-scaled TiO2 (nTiO2) after purification when used as a suspension in treated water. Thus this study evaluates the performance of four grades of micro-scaled TiO2 (mTiO2) on the degradation of organic matters, Escherichia coli (E. coli) and total coliform in river water and to investigate the percentage recovery of the mTiO2 using a locally manufactured Polyester Woven Fabric Microfiltration (PWFMF) membrane. The PWFMF though uncharacterized has been used in a number of studies for treating domestic and industrial waste waters. The best-performing grade was used to optimize the degradation efficiency of E. coli in river water using the Design of Experiments (DOE) methodology. Grade 2 of the mTiO2, which is hydrated titanium dioxide with additions (ahTiO2) of particle size range of 0.2 – 53 µm at a concentration of 2.5 g/l displayed an advantageous photocatalytic activity. The results show that 80 % of the organics were removed in 3 hours and increased to 93% after 6 hours. Two particle size ranges of 0.2 – 53 µm and 54 – 75 µm at a concentration of 5 g/l degraded organic matters to 90 % and 77 % in 3 hours respectively. The particle size range of 0.2 – 53 µm at a concentration of 5 g/l was then filtered using a PWFMF and turbidities went below 1 NTU after 20 minutes from feed turbidity of 470 NTU for all three trials. The average percentage recovery in 2 hours was 98.91 %. The four grades of mTiO2 were analyzed for E. coli and total coliform for 4 hours at concentrations of 2, 5 and 7 g/l. Grade 2 achieved the E. coli specification of 0 count/ 100 mL at 5 g/l in 2 hours and at 7 g/l in 0.5 hours. Grade 4 E. coli specification was achieved with 7g/l in 4 hours. Grades 2 and 4 performed better since they both achieved the E. coli and total coliform specifications. Grade 2 was the best performing grade and was considered for statistical studies. Grade 2 was then used on a comparative study between the Central Composite Design (CCD) and Box-Behnken Design (BBD), which are two of the major Response Surface Methodologies (RSM). The CCD compared to BBD provides high quality predictions over the entire design space. The CCD obtained optimum results for concentration of mTiO2 (X1), temperature (X2), initial pH (X3) and aeration (X4) which were 6.94 g/l, 28.75 OC, pH = 6.04, and 13.35 L/min for the maximum degradation efficiency of 99.85 % which showed comparable optimum results to the BBD that were 6.45 g/l, 28.28 OC, pH = 6.02 and 12.21 L/min for the maximum degradation efficiency of 99.80%. These theoretical model results were validated by practical experiments that produced the maximum degradation efficiency for CCD and BBD of 99.67 and 99.26 % respectively. Grade 2 of the mTiO2 can be used as a photocatalyst for river water purification due to its strong ability for the removal of E. coli. The additions used in grades 2 and 4 during production improved the photocatalytic activity. The PWFMF membrane showed a great performance of above 98 % particle recovery of mTiO2 from treated water, although there was an indication that the smallest particles were passing through the membrane. The RSM results gave approximately the same optimum results that were well within the limits, which were experimentally validated and showed that the models were sustainable. It is recommended that the effect of additions be studied on the structures or the charge stability of the two grades. / M