Showing papers by "Sherub Phuntsho published in 2013"
TL;DR: Nanofiltration (NF) is one of the widely used membrane processes for water and wastewater treatment in addition to other applications such as desalination as mentioned in this paper, which has replaced reverse osmosis (RO) membranes in many applications due to lower energy consumption and higher flux rates.
Abstract: . The application of membrane technology in water and wastewater treatment is increasing due to stringent water quality standards. Nanofiltration (NF) is one of the widely used membrane processes for water and wastewater treatment in addition to other applications such as desalination. NF has replaced reverse osmosis (RO) membranes in many applications due to lower energy consumption and higher flux rates. This paper briefly reviews the application of NF for water and wastewater treatment including fundamentals, mechanisms, fouling challenges and their controls.
172 citations
TL;DR: In this paper, the influence of membrane properties, draw solution (DS) properties, feed solution (FS) properties and operating conditions on the performance of forward osmosis (FO) desalination was evaluated.
150 citations
TL;DR: In this paper, nanofiltration has been assessed as an integrated process to FDFO desalination, either as a pre-treatment or post-treatment, to reduce the nutrient concentrations in the final product water and thereby allow direct use of the product water for fertigation without further dilution.
129 citations
TL;DR: PTC is an effective and promising coagulant for water purification and was able to recycle and produce functional TiO2 photocatalyst and the water pH after PTC coagulation was significantly improved toward neutral pH.
Abstract: Polymeric metal coagulants are increasingly being used to improve coagulation efficiency, yet the research on the development of titanium and particularly polytitanium salts remains limited. This study is the first attempt in the synthesis, characterization, and application of polytitanium salts as coagulants. Polytitanium tetrachloride (PTC) solutions with different basicity values B (OH/Ti molar ratio) were prepared using a slow alkaline titration method. Jar tests were conducted to assess coagulation performance using both synthetic and real raw water samples, and the floc characteristics were monitored online using a laser diffraction particle size analyzer. Electrospray ionization time-of-flight mass spectrometry (ESI-TOF-MS) was utilized to identify various Ti species, with the results providing strong evidence of the presence of various hydrolyzed Ti species in the titanium aqueous phase. Compared to titanium tetrachloride (TiCl4), higher or comparable turbidity and organic matter removal efficiency could be achieved by PTC with improved floc characteristics in terms of size, growth rate, and structure. Besides, the water pH after PTC coagulation was significantly improved toward neutral pH. This study indicates that PTC is an effective and promising coagulant for water purification. Besides, the PTC flocculated sludge was able to recycle and produce functional TiO2 photocatalyst.
83 citations
TL;DR: In this study, humic acid and Suwannee River natural organic matter were tested and compared as surface modifiers for Fe2O3 nanoparticles (NPs) and showed that both HA and SRNOM were rapidly and readily adsorbed on the surface of Fe2 O3 NPs, providing electrosteric stabilisation over a wide range of pH.
66 citations
TL;DR: This is the first attempt to use cationic polyacrylamide (PAM) as coagulant aid with titanium tetrachloride (TiCl4) to improve the coagulation performance and floc properties and showed that organic removal was enhanced by PAM addition at low TiCl4 doses.
54 citations
TL;DR: A multi-method approach was used to thoroughly characterise the behaviour of iron oxide nanoparticles (Fe2O3NPs) under environmentally relevant conditions, and coating the nanoparticles with dissolved organic matter (DOM) was investigated as an alternative "green" solution to overcoming the aggregation issue.
50 citations
TL;DR: In this paper, the authors investigated the performance of a post-treatment of the fertilizer-drawn forward osmosis with nanofiltration (NF) process and found that it can effectively reject the low nutrient (N) concentration more than 90%.
Abstract: The integration of the fertilizer-drawn forward osmosis with nanofiltration (NF) has been investigated to evaluate the performance of NF process as a post-treatment. The primary objective of this study is to optimize the operating conditions such as feed flow rate and feed concentration, while producing fresh water including low nutrient (N) concentration can be directly used for irrigation. Investigation of operating parameters at the pilot-scale level focused on specific water flux and ammonium sulphate rejection. Results from this study showed that NF process applied as the post-treatment can effectively reject the N concentration more than 90%. Although other factors such as the applied pressure and the cross-flow rates played a certain role in the performance of the pilot-scale NF process, the influence of the feed concentration was more significant on the specific water flux and N rejection.
31 citations
TL;DR: In this paper, two newly developed polyamide-based thin-film composite (TFC) FO membranes were tested and compared with the commercially available cellulose triacetate (CTA) FO membrane.
Abstract: Forward osmosis (FO) is an emerging low-energy technology. Much effort was given on developing a new membrane material and engineering membrane structure to improve the performance of FO membranes. The performances of two newly developed polyamide-based thin-film composite (TFC) FO membranes were tested and compared with the commercially available cellulose triacetate (CTA) FO membrane. The intrinsic properties of the two TFC FO membranes determined in RO experiments indicate superior performance of the membranes. When tested in FO experiments, TFC membranes delivered consistent results, confirming their outstanding permeability and selectivity properties. The study shows that future studies on membrane fouling will be necessary to have a better understanding of membrane performance and to further optimize membrane properties.
30 citations
TL;DR: In this paper, the effects of coagulant dose, solution pH and hydraulic conditions, including shear force and break-up period, on floc properties were investigated, and the results showed that the floc size followed the order of TiCl 4 Â> FeCl 3 Â > Al 2 (SO 4 ) 3 within the dose range investigated.
21 citations
TL;DR: In this article, a two-stage titanium tetrachloride (TiCl 4 ) dosing strategy was applied for investigating the coagulation effect on simulated water containing humic acid (HA) and fulvic acid (FA) and these represent the dissolved organic matter (DOM).
TL;DR: In this article, a comparative assessment of these two fertilizers as draw solution (DS) for forward osmosis (FO) desalination was conducted and the results indicated that both MAP and DAP can be used as a DS for FO desalification and for direct fertigation although concentration polarization significantly affected the water flux.
Abstract: Forward osmosis (FO) can be suitably used to desalinate water for irrigation using fertilizer as draw agent due to the desalinated water containing diluted draw solution. Mono-ammonium hydrogen phosphate (MAP) and di-ammonium hydrogen phosphate (DAP) are the important group of the most concentrated soluble fertilizer materials containing both N and P, essential fertilizer elements needed by the plants. The comparative assessment of these two fertilizers as draw solution (DS) for FO desalination was conducted. The results indicate that both MAP and DAP can be used as a DS for FO desalination and for direct fertigation although concentration polarization significantly affected the water flux. MAP performed slightly better in terms of pure water flux. However, the performance ratio of DAP was comparable to MAP when saline feed water was used. Furthermore, DAP was seen as a better DS candidate for desalination and fertigation due to significantly lower reverse solute flux.