Forward Osmosis as a Pre-Treatment Step for Seawater Dilution and Wastewater Reclamation

This chapter presents the exploration of the combined process of wastewater reclamation and seawater dilution using forward osmosis (FO). Wastewater and seawater are the two most abundant water sources that are free of the hydrological cycle and could serve as an alternative potable water source. Forward osmosis was chosen as the an ideal pre-treatment step to dilute seawater prior to desalination at relatively lower energy demand and low fouling propensity. Membrane fouling behavior was studied and investigated using different feed compositions bearing fractions of effluent organic matter (EfOM). The negative surface charge of all organic foulants was reduced by the adsorption of calcium ions. Filtration of feed streams containing single, simple organic foulants revealed that alginate (polysaccharides) and bovine serum albumin (BSA) resulted in significant loss in process performance as a result of permeate flux reduction. The complex mixture of alginate, BSA and humic acid caused severe loss in membrane performance due to dominant favorable synergistic interactions between foulants and between foulants and membrane surface. The forward osmosis process presents a viable alternative for a simple and effective seawater dilution step using wastewater as the feed solution. Process performance can be improved by selecting a foulant resistant membrane with matching flux

Photocatalytic Membranes for Efficient Water Treatment

Membrane processes which combine the physical separation through filtration and pollutant degradation or antibacterial properties achieved by photocatalysis in a single unit are gaining popularity as wastewater treatment alternatives. There has been considerable progress in the development of photocatalytic membranes through incorporation of metal-oxide photocatalysts to enhance the performance of the membranes. An optimum amount of the photocatalyst should be incorporated into the membrane in order to realise reasonable photocatalytic activity with minimal consequences on water flux. Besides TiO2 loading, membrane performance is also affected by light intensity and irradiation time. This chapter highlights some of the recent progresses in photocatalytic membrane fabrication, reactor configuration and membrane application in disinfection and pollutant removal from wastewater

Forward osmosis membrane performance during simulated wastewater reclamation : fouling mechanisms and fouling layer properties

A thin-film composite (TFC) FO membrane was used to study the fouling characteristics of effluent organic matter (EfOM) fractions in treated wastewater effluent represented by alginate, bovine serum albumin, humic acid and octanoic acid. These model foulants were chosen to represent carbohydrates, proteins, humic substances and fatty acids. Inter foulant interactions and their influence on membrane flux loss was established by running series of fouling tests with feed solutions containing mixtures of model foulants. The obtained results demonstrated that under our experimental conditions humic acid (HA) and octanoic acid (OA) had no significant role on permeate flux loss during wastewater treatment over short periods. However, alginate and bovine serum albumin (BSA) and their mixtures caused significant total flux loss, through alginate-calcium complexation that led to the formation of a resistant gel layer on the membrane surface. Protein fouling was mainly attributed to multiple layer adsorption onto the polyamide membrane surface. Mixing alginate with BSA saw a further decline in permeate flux, worse than that caused individually by either of the foulants, and gives an indication of the synergistic effect between the two foulants. There were favourable inter-foulant interactions between the carbohydrates and the proteins that promoted the formation of hybrid aggregates that were deposited on the membrane surface and enhanced flux loss. The additional presence of humic acid to the mixture of BSA and alginate further aggravated membrane fouling. Polysaccharides and proteins were found to be the most dominant foulants during wastewater reclamation. The extent of interactions between the organic foulants had an effect on the fouling layer structure and its role in permeate flux loss

Monitoring natural organic matter and disinfection by-products at different stages in two South African water treatment plants

Natural organic matter (NOM) is a complex organic material present in natural surface water. NOM can cause problems during water treatment . most notably the formation of toxic disinfection by-products. This study was undertaken in order to assess the effectiveness of some of the water treatment techniques employed by selected water supply companies in South Africa in dealing with NOM. Total organic carbon (TOC) and ultra violet (UV) absorbance at wavelength of 254 nm were measured andused to calculate specific ultra violet absorbance (SUVA), which was used to determine the changes in NOM concentration throughout the water treatment train. Other parameters measured include pH, turbidity, chemical oxygen demand (COD) and conductivity. Water samples were collected from two water treatment plants in South Africa, namely Sedibeng (Balkfontein) and Midvaal. The overall TOC reduction after the water treatment processes was 33% and 30% at Midvaal and Sedibeng, respectively. SUVA values were generally low (<2 ..mg-1.m-1) indicating the presence of aliphatic compounds and less earomaticityf in NOM of the water samples. Water insoluble ƒÀ-cyclodextrin (ƒÀ-CD) polyurethanes were then applied to the water to compare TOC reduction in addition to enormalf water treatment processes, and were found to provide up to 19% additional TOC decrease, and UV absorbance reduction was up to 78%. Results obtained using gas chromatography-mass spectrometry (GC-MS) analysis after chlorination, revealed that the water had the potential to form halomethane compounds with chloroform being the most dominant. Again, water-insoluble ƒÀ-CD polyurethanes were applied to the water as a treatment to remove trihalomethanes (THMs) and were found to efficiently remove up to 95% of THMs formed during the disinfection step. The treatment processes studied have limited ability in dealing with NOM and are not individually effective in NOM removal. Results obtained indicate that the application of ƒÀ-CD polyurethanes in addition to the water treatment processes may enhance NOM removal in water and significantly reduce the THMs formed

Recent Developments in Environmental Photocatalytic Degradation of Organic Pollutants: The Case of Titanium Dioxide Nanoparticles—A Review

The presence of both organic and inorganic pollutants in water due to industrial, agricultural, and domestic activities has led to the global need for the development of new, improved, and advanced but effective technologies to effectively address the challenges of water quality. It is therefore necessary to develop a technology which would completely remove contaminants from contaminated waters. TiO2 (titania) nanocatalysts have a proven potential to treat “difficult-to-remove” contaminants and thus are expected to play an important role in the remediation of environmental and pollution challenges. Titania nanoparticles are intended to be both supplementary and complementary to the present water-treatment technologies through the destruction or transformation of hazardous chemical wastes to innocuous end-products, that is, CO2 and H2O. This paper therefore explores and summarizes recent efforts in the area of titania nanoparticle synthesis, modifications, and application of titania nanoparticles for water treatment purposes

Platinum Group Metal Based Nanocatalysts for Environmental Decontamination

Research and development in chemical engineering is currently focused on design of highly active and selective catalytic systems for process intensification. In recent years, there has been growing interest in the use of catalysts based on nanosized metal particles to improve catalytic processes. Among the many metal catalysts, platinum group metals (PGMs) have received greater attention because of their physical and catalytic properties. They have found applications in a wide range of chemical conversion and environmental decontamination reactions due to their chemical stability and enhanced catalytic reactivity in the nano range. This chapter reviews some of the major innovative applications of PGM nanocatalysts for catalytic environmental decontamination

Electrochemical studies and sensing of iodate, periodate and sulphite ions at carbon nanotubes/ Prussian blue films modified platinum electrode

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