The degradtion of humic substance using continuous photocatalysis systems

Photocatalytic oxidation is an emerging technology in water and wastewater treatment. Photocatalysis often leads to complete degradation of organic pollutants without the need for chemicals. This study investigated the degradation of humic substances in water using photocatalysis systems coupled with physio-chemical processes such as adsorption and/or flocculation. Dissolved Organic Carbon (DOC) removal of PAC-TiO2 was improved by a factor of two to three times compared with TiO2 alone. Solid Phase Micro Extraction (SPME)/Gas Chromatograph (GC) flame ionisation detector (FID) was used to investigate intermediates of photocatalytic oxidation in a batch reactor with TiO2 alone and with powder activated carbon (PAC) with TiO2. GC peaks showed that PAC-TiO2 adsorbed some by-products which were photo-resistant and prevented the reverse reaction that occurred when TiO2 was used alone. The two other types of photocatalytic reactors used were the continuous photocatalytic reactor and recirculated photocatalytic reactor. The results show that the recirculated reactor had the highest efficiency in removing organic matter in a short photo-oxidation (detention) time of less than 10min. The use of PAC-TiO2 in recirculated continuous reactor resulted in 80% removal of organic matter even when it was operated for a short detention time and allowed the use of a smaller dose of TiO2

Submerged membrane system with biofilter as a treatment to rainwater

Rainwater has been used as drinking water in Thailand for centuries especially in the rural parts and is accepted as an important water resource. From past to present, the quality of rainwater has changed with the landuse of the landscape, and its water quality is influenced by a diverse range of conditions such as the management of pollutant sources, the catchment condition, wind and meteorological conditions, and the location of rainwater collection points. In this study, the quality of rainwater collected off roofs at several locations was examined. Granular activated carbon (GAC) filtration was used as a pretreatment to microfiltration (MF) to remove the dissolved organic matter (DOC). After an initial adsorption period, the biofilm that formed on the GAC (biofilter) was found to remove DOC by up to 40%, 35%, and 15% for bed filter depths of 15, 10, and 5 cm, respectively. Biofilters also removed nitrate and phosphate by more than 80% and 35%. The hollow fiber membrane microfiltration with pore size of 0.1 μm was used to treat the effluent from biofiltration to remove the microorganisms/pathogens in the rainwater. Although there was no significant additional removal of DOC by MF, the biofilter removed all microorganisms. The use of biofilters as pretreatment to MF/UF could remove a higher amount of DOC, remove microorganisms, increase the membrane treatment efficiency, and reduce membrane fouling. © Springer Science + Business Media B.V. 2009

Granular activated carbon (GAC) adsorptionphotocatalysis hybrid system in the removal of herbicide from water

The performance of the granular activated carbon (GAC) fixed bed adsorption, the continuous photocatalysis systems and a combination of the two were studied to evaluate their capabilities in removing the herbicide of metsulfuron-methyl (MM) from waste water. Columns packed with GAC at different bed depths were operated at different filtration rates over a period of several weeks. Removal of MM via adsorption using GAC fixed beds of 5, 10 and 15 cm depths (operated at meter per hour) achieved a removal of 35, 55 and 65% of MM respectively. In the continuous photocatalysis system, heterogeneous photocatalysis with TiO2 was used to degrade MM. The system achieved removal rates between 40 and 60%. GAC photocatalysis hybrid system is a coupling of GAC fixed bed adsorption and the continuous photocatalysis system where the effluent from the former was fed to the later. TiO2 and small amount of powder activated carbon (PAC) were used as the catalyst in the photocatalysis system. The system had a high removal rate of over 90%. The retention time of the photocatalysis system was less than 10 min. This system allows a greater degree of flexibility in the manner the system can be operated

Photocatalytic degradation of organic pollutants from wastewater using aluminium doped titanium dioxide

© 2018 Elsevier Ltd The objective of this research was to study the performance of batch and continuous recirculating reactor to photo-degrade dye and synthetic wastewater. Here, Aluminium (Al) was used as the doped metal. The commercially available TiO2 P-25 and Al (NO3)3 was used as a Ti-precursor and doping agent, respectively, via the impregnation method. Various parameters such as the concentration of the doping agent, and calcination temperature were studied. The TiO2 nanocrystal doped with Al was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and thermogravimetric analyzer (TGA). The photocatalytic performance of Al-doped nanoparticle was quantified by the degradation of methylene blue (MB) solution under a visible light irradiation condition. Its performance was compared against undoped-nano-TiO2. The results showed that Al(NO3)3 solution with a concentration of 0.25% and volume of 100 cm/ml, and calcined at 300 ๐C for 4 h, was the optimum condition of Al-doped nano-TiO2. Furthermore, the highest pseudo-first-order kinetic rate was 0.096 where the doped Al(NO3)3 of 0.75 w/v was used in the batch reactor. The Al-doped nano-TiO2 that was obtained has the potential for use as a photocatalyst for degradation organics pollutant from wastewater under the visible light irradiation. The highest removal of organic pollutants from synthetic wastewater was 75% using TiO2 P-25 alone at 2 g/L dosage. In addition, the removal of organic pollutant by TiO2/doped with Al was 80% at a dosage of 0.5 g/L and was 85% at a dosage of 1 g/L

A continuous photocatalysis system in the degradation of herbicide

The performance of both batch and continuous photo-catalytic reactors was studied to evaluate their capabilities in removing the sulfonyl urea herbicide of metsulfuron methyl (MM). It was found in a batch reactor that the addition of a small amount of powder activated carbon (PAC) significantly increased the rate of degradation of MM. The continuous photo-catalytic system resulted in 57% of MM removal. When a small dose of activated carbon was added in the photo-catalytic system, MM removal increased to 78-86% MM removal for retention times between of 5.25-21 min (corresponding to withdrawal rates of 10-40 mLmin-1). In this study, the pseudo first order rate constants of a continuous photo-catalytic system revealed that shorter retention times were associated with lower rate constants. Solid phase micro extraction/gas chromatography (SPME/GC) results showed that high concentrations of MM were broken down to small volatile organic compounds (VOCs) by photo-catalytic oxidation. PAC adsorbed the photo-products and increased the degradation of MM. © 2008 Springer

Water quality of membrane filtered rainwater

Although most Australians receive their domestic supply from reticulated mains or town water, there are vast areas with very low population densities and few reticulated supplies. In many of these areas rainwater collected in tanks is the primary source of drinking water. Heavy metals are a concern as their concentration in rainwater tanks was found to exceed recommended levels suitable for human consumption. This paper reports on experimental investigations where rainwater collected from a typical domestic roof in Sydney, Australia was treated in two stages of filtration including granular activated carbon (GAC) as a pre-treatment adsorption filter media and a metallic membrane from Steri-flow Filtration Systems Pty. Ltd. The quality of the treated rainwater was compared against the drinking water standards to determine its suitability as a supplement for potable water supply. The pollutants analysed were heavy metals, total coliform and faecal coliforms, total organic carbon, total suspended solids and turbidity. The results indicate that before treatment, the rainwater already complied with many of the parameters specified in drinking water standards. The metallic membrane performed well in removing suspended particles and heavy metals from the rainwater. The performance of the metallic membrane is greatly improved by the use of pre-treatment such as GAC which was used in this experiment. © 2011 Desalination Publications. All rights reserved

Submerged Membrane System with Biofilter as a Treatment to Rainwater

Abstract Rainwater has been used as drinking water in Thailand for centuries especially in the rural parts and is accepted as an important water resource. From past to present, the quality of rainwater has changed with the landuse of the landscape, and its water quality is influenced by a diverse range of conditions such as the management of pollutant sources, the catchment condition, wind and meteorological conditions, and the location of rainwater collection points. In this study, the quality of rainwater collected off roofs at several locations was examined. Granular activated carbon (GAC) filtration was used as a pretreatment to microfiltration (MF) to remove the dissolved organic matter (DOC). After an initial adsorption period, the biofilm that formed on the GAC (biofilter) was found to remove DOC by up to 40%, 35%, and 15% for bed filter depths of 15, 10, and 5 cm, respectively. Biofilters also removed nitrate and phosphate by more than 80% and 35%. The hollow fiber membrane microfiltration with pore size of 0.1 μm was used to treat the effluent from biofiltration to remove the microorganisms/pathogens in the rainwater. Although there was no significant additional removal of DOC by MF, the biofilter removed all microorganisms. The use of biofilters as pretreatment to MF/UF could remove a higher amount of DOC, remove microorganisms, increase the membrane treatment efficiency, and reduce membrane fouling