Forward Osmosis (FO) is an emerging technology which has potential to operate with minimum energy input. High performance of FO systems depend on the availability of a suitable Draw Solution. Different types of Draw Solutions have been proposed, however; choosing a suitable one is still a developing area within the FO field. There is an urgent need to explore new materials in order to develop an efficient FO system. The current study aims at investigating the performance of three Draw Solutions namely, L-Alanine, DADMAC and PolyDADMAC as osmotic agents for FO. These organic cationic solutions can be used as extraction agents of water from poorer quality organic solutes such as fumaric acid solution produced in a continuous flow microbial fermentation process. The performance of the three Draw Solutions was evaluated by measuring the water flux and reverse solute diffusion at different concentrations. The viability of reconcentration of the diluted Draw Solutions was also investigated using Nanofiltration system. The performance and the efficiency of the Draw Solutions were studied via two separated bench scale systems of FO and Nanofiltration. Both Cellulose Triacetate (CTA) and Thin Film Composite (TFC) aquaporin protein FO membranes were employed under different orientations in FO set up operated for 24 hours or longer. In this study, NF90 membrane was used for reconcentration the Draw Solutions. A series of experiments were conducted to obtain the best water flux and reverse solute diffusion under various influencing operating conditions. The experiments were designed to achieve three objectives, i.e. (i) optimum operating conditions for FO system, (ii) optimum operating conditions for the reconcentration system, and (iii) implementation of the optimum operating conditions of the FO system for water recovery from a fumaric acid solution produced by a simulated industrial fermentation process. In the initial stage, L-Alanine Draw Solution demonstrated that it was the most viable agent for FO. It was established that L-Alanine Solution at 0.085 g/mL concentration achieved the highest initial water flux and the lowest reverse solute diffusion through both CTA and TFC aquaporin protein FO membranes. In the second stage, a Nanofiltration system was proven to be effective in the reconcentration of the diluted L-Alanine Draw Solution. The average rejection of L-Alanine ions achieved by NF90 membrane was 96.00%. Drawing on the previous results, the third stage was used to investigate the viability of the FO system in water recovery from fumaric acid solution produced by continuous microbial fermentation process using L-Alanine as a Draw Solution. The reduction of water content of the fumaric acid solution made it to concentrate by 26.00% and 19.80% in 32_ and 17_, respectively. Consequently, FO technology is an effective way to concentrate a fumaric acid solution produced by continuous microbial fermentation process. Based on the results, it is recommended that LAlanine should be proposed in the FO process according to its reliability and effectiveness as a viable draw agent. TFC aquaporin protein membrane is also recommended to be used in recover the water from fumaric acid solution produced by fermentation processes. Further studies should be done to investigate the viability of FO in water recovery from advanced application such as downstream bioprocessing. / Dissertation (MEng)--University of Pretoria, 2017. / Chemical Engineering / MEng / Unrestricted

Up to 30% by mass of plant cell walls are comprised of hemicelluloses. The remainder is comprised of cellulose, lignin and extractives. Potential economic uses of hemicellulose include hydrogels, fibre additives in pulp mill paper-making and as a substrate for fermentation processes. Development of a fermentation process with sugars from hemicellulose has become of increasing interest due to their potential as a feedstock for fermentation-based liquid fuels and other bio-based chemicals. These can be incorporated into existing processes, in particular alkaline chemical pulping mills, where up to 50% of the hemicelluloses are today degraded and eventually combusted. The main objective of this project is to examine the solubility and aggregation properties of xylans (the predominant hemicellulose), as this will hopefully lead to better solubility-based separations for their recovery. This was done at Michigan State University by alkaline extraction at 85°C on milled birch wood, and at 130 and 170°C (both time-dependent) on birch chips, with 50 g/L sodium hydroxide. This was then followed by precipitation/aggregation experiments with ethanol, polyDADMAC (a polycationic flocculant) and by acidification. Characterisation was done by performing dynamic light scattering (DLS) and size exclusion chromatography (SEC) analysis on resolubilised recovered material from the different extraction conditions. From these, size distributions, molecular weights and degrees of polymerization (DP) could be estimated. The DP values for the extracted polymers were higher than the expected values for hardwood xylans, owing to the incoherent SEC chromatograms. This may be due to aggregate formation with other polymers or re-solubilisation issues of the hemicellulose precipitates. The estimated size range for model xylan was between 100 to 300 nm and the ethanol precipitates seemed to also lie around this region, as detected by DLS. One of the major factors contributing to the difficulty of analysing the results was the issue of re-solubilisation of the hemicellulose precipitates and flocculates. / <p>Validerat; 20120827 (anonymous); 2017-02-08 Nedladdad 414 gånger t.o.m. september 2016. Downloaded 414 times up until september 2016 (marisr)</p>

N-Nitrosodimethylamine (commonly known as NDMA) is a probable human carcinogen that has been recognized as an emerging drinking water contaminant in recent years. Previous studies have shown that certain N-containing organic compounds may form NDMA in reaction with chlorine or monochloramine and the NDMA yield is affected by the structure of the organic-N compounds, water conditions and treatment parameters. Many amine-based water treatment polymers contain organic-N functional groups and thus have been suspected as potential NDMA precursors in water treatment systems. The purpose of this research was to systematically assess the potential NDMA formation from different structural types of water treatment polymers in reactions with various oxidants and probe the possible factors that influence the NDMA formation. Robust analytical methods for detection of NDMA and the well-known NDMA precursor dimethylamine (DMA) in the reaction samples were established. The cationic polyacrylamide (cationic PAMS), aminomethylated polyacrylamide (Mannich), poly-diallyldimethylammonium chloride (polyDADMAC) and polyamine polymers were evaluated in reactions with nitrite, free chlorine, monochloramine or chlorine dioxide in aqueous solutions at circumneutral pH and room temperature conditions. This study employed high dosages of polymer and oxidant and long reaction time in order to assess the maximum potential to form NDMA. A range of operational parameters that may affect the above reactions were also evaluated.

abstract: N-nitrosodimethylamine (NDMA) is a probable human carcinogen and drinking water disinfection by-product. NDMA forms as the product of reactions between chloramines and precursor compounds in water. This dissertation aims to provide insight into the removal of NDMA precursors, their nature, and a method to aid in their identification. Watershed-derived precursors accounted for more of and greater variability to NDMA formation upon chloramination than polymer-derived precursors in environmental samples. Coagulation polymers are quaternary amines, which have low NDMA yield but high use rates. Watershed-derived precursors were removed up to 90% by sorption to activated carbon, but activated carbon exhibited much less (<10%) sorption of polymer-derived precursors. Combined with literature NDMA molar yields of model anthropogenic compounds, where anthropogenic chemicals in some cases have NDMA yields >90% and biological compounds always have yields <2%, trace, organic, amine containing, anthropogenic chemicals were implicated as the most likely source of NDMA precursors in the watershed. Although activated carbon removes these precursors well, identification of individual compounds may result in more cost effective mitigation strategies. Therefore, I developed a method to isolate NDMA precursors from other organic matter into methanol to facilitate their identification. Optimization of the method resulted in a median recovery of NDMA precursors of 82% from 10 surface waters and one wastewater. The method produces 1,000X concentrated NDMA precursors and, in collaboration with the University of Colorado Center for Environmental Mass Spectrometry, time of flight mass spectrometry (TOF-MS) was performed on multiple treated wastewater and raw drinking water isolates. During TOF-MS, tertiary amines can cleave to form a neutral loss and an R group ion that is dependent on the original structure and I wrote a software program to “trawl” exported TOF-MS spectra for the diagnostic neutral loss resulting from fragmentation of tertiary amines. Methadone was identified as one new NDMA precursor that occurs at concentrations that form physiologically relevant levels of NDMA in surface water and wastewater. The approach used here to identify NDMA precursors is adaptable to other unknown disinfection by-product precursors given that a functional group is known that can 1)control sorption and 2)produce a predictable diagnostic fragment. / Dissertation/Thesis / Doctoral Dissertation Civil and Environmental Engineering 2015