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From this study, the cabbage and cauliflower, a well-known agro-waste were used as biosorbents for removing toxic lead(II) and cadmium(II) from water. A batch of experiments for both biosorbents indicated that the lead(II) and cadmium(II) sorption depended on pH (5.0–6.5), doses of biosorbents (3–8 g/L) and contact time (15–45 min). The adsorption processes were fast, and equilibrium time was reached at 45 and 15 min for lead(II) and 45 and 30 min for cadmium(II) adsorption onto cabbage and cauliflower biosorbents, respectively. Both biosorbents showed higher preferences for lead(II) than cadmium(II) towards adsorption from a binary solution. Langmuir model was the best-predicted model, but three-parameter models (Redlich-Peterson, Koble Corrigan, Khan and SIPS) were shown good fitness with equilibrium data, and the adsorption coefficients indicate favourable adsorption. The maximum monolayer capacities for lead(II) were 60.57 and 47.63 mg/g onto cabbage and cauliflower biosorbents, respectively, ...

In this study, the removal of different fractions of organic matter in seawater was investigated using titanium tetrachloride (TiCl4) flocculation and compared with ferric chloride (FeCl3) flocculation. The organic matter fractions were characterised using liquid chromatography-organic carbon detector (LC-OCD). Results showed the hydrophobic compounds removal was dominant by both flocculants. However, the removal of hydrophilic organic compounds, such as humics and low-molecular weight neutral compounds of seawater, was superior by TiCl4 flocculation compared to FeCl3 flocculation and this removal increased considerably with the increase of TiCl4 doses. The flocculated sludge after TiCl4 flocculation was incinerated to produce titanium dioxide (TiO2) nanoparticle. TiO2 from seawater sludge characterised by X-ray diffraction (XRD) and scanning electron microscope/energy-dispersive X-ray spectroscopy (SEM/EDS) showed predominant anatase phase with Si as a main dopant. © 2013 Copyright Balaban Desalination Publications.

In this study, two different submerged membrane hybrid systems (SMHSs) namely (i) submerged membrane coagulation hybrid system (SMCHS) and (ii) submerged membrane coagulation-adsorption hybrid system (SMCAHS) were investigated as pretreatment options for seawater reverse osmosis. Organic matters in seawater before and after pretreatment were characterized in terms of XAD fractionation, molecular weight distribution (MWD) and fluorescence. A detailed study on the seawater organic matter (SWOM) structure was made through 1H-nuclear magnetic resonance (1H NMR), pyrolysis-gas chromatography-mass spectrometry (Py-GC/MS) and liquid chromatography-mass spectrometry-ion trap-time of fright (LC/MS-IT-TOF). The seawater investigated in this study is mainly composed of hydrophilic matter (57±3.2%). SMHSs removed a significant amount of organic matter. The EEM fluorescence showed a removal of humic-like materials by SMHSs. In addition, humic-like materials relative to protein-like compounds were reduced significantly but the aromaticity of humic-like materials increased. After pretreatment by SMHSs, humics and biopolymers of over 900Da. were found to be reduced and their structure associated with element composition was also changed. The transformation of the SWOM structure after SMHSs pretreatment may have been due to hydrolyzation or oxidization of the organic compounds such as humics and biopolymers resulting in poly-conjugation to aromatic compounds. SMHSs were effective in improving the RO performance leading to higher RO permeate flux and lower permeate flux decline. The pretreatment reduced the amount of foulants on the RO membrane. © 2012 Elsevier B.V.

Ammonium pollution in groundwater and surface water is of major concern in many parts of the world due to the danger it poses to the environment and people's health. This study focuses on the development of a low cost adsorbent, specifically a modified biochar prepared from corncob. Evaluated here is the efficiency of this new material for removing ammonium from synthetic water (ammonium concentration from 10 to 100mg/L). The characteristics of the modified biochar were determined by Brunauer-Emmett-Teller (BET) test, Fourier transform infrared spectroscopy (FTIR) and Scanning electron microscopy (SEM). It was found that ammonium adsorption on modified biochar strongly depended on pH. Adsorption kinetics of NH4+-N using modified biochar followed the pseudo-second order kinetic model. Both Langmuir and Sips adsorption isotherm models could simulate well the adsorption behavior of ammonium on modificated biochar. The highest adsorption capacity of 22.6mg NH4+-N/g modified biochar was obtained when the biochar was modified by soaking it in HNO3 6M and NaOH 0.3M for 8h and 24h, respectively. The high adsorption capacity of the modified biochar suggested that it is a promising adsorbent for NH4+-N remediation from water.

Dewatering of sludge from sewage treatment plants is proving to be a significant challenge due to the large amounts of residual sludges generated annually. In recent years, research and development have focused on improving the dewatering process in order to reduce subsequent costs of sludge management and transport. To achieve this goal, it is necessary to establish reliable indices that reflect the efficiency of sludge dewatering. However, the evaluation of sludge dewaterability is not an easy task due to the highly complex nature of sewage sludge and variations in solid–liquid separation methods. Most traditional dewatering indices fail to predict the maximum cake solids content achievable during full-scale dewatering. This paper reviews the difficulties in assessing sludge dewatering performance, and the main techniques used to evaluate dewatering performance are compared and discussed in detail. Finally, the paper suggests a new dewatering index, namely the modified centrifugal index, which is demonstrated to be an appropriate indicator for estimating the final cake solids content as well as simulating the prototype dewatering process.

© 2015 Elsevier B.V. All rights reserved. Elevated concentrations of nitrate in surface waters can cause eutrophication, while in drinking water they pose a threat to human health, especially causing blue baby syndrome in infants. An anion exchange resin - Dowex 21K XLT - was surface modified by incorporating Fe (Dowex-Fe) and tested to remove nitrate from aqueous solutions in batch and fluidised-bed adsorption experiments. Solution pH in the 4.0-7.5 range had no effect on nitrate adsorption. The adsorption data at pH 6.5 fitted well to the Langmuir model with maximum adsorption capacities of 27.6 mg N/g, and 75.3 mg N/g for Dowex and Dowex-Fe resins, respectively. Energy dispersion spectrometry and zeta potential measurements indicated that the increase in adsorption due to Fe impregnation was caused by additional surface positive charges induced on the resin by Fe. In both batch and fluidised-bed experiments, nitrate adsorption capacity declined markedly when sulphate was added, but phosphate and chloride additions had little effect. Batch kinetic data fitted well to the pseudo-first, pseudo-second and homogeneous surface diffusion models. Data from the fluidised-bed experiments satisfactorily fitted to the Thomas and plug-flow models. More than 95% of adsorbed nitrate was desorbed by 1 M KCl in all three adsorption/desorption cycles and the resins were successfully regenerated in each cycle with little reduction in adsorption capacity. No significant reduction in the Fe content of Dowex-Fe occurred during the regeneration.

© 2006 Australasian Fluid Mechanics Society. All rights reserved. Green or living walls are active bio-filters developed to enhance air quality. Often, these walls form the base from which plants are grown; and the plant-wall system helps to remove both gaseous and particulate air pollutants. A green wall can be found indoors as well as outdoors, and could be assembled from modules in an arrangement similar to tiling. Measurement of air flow through such a module has been conducted in this work. The module is essentially a rectangular plastic box (dimensions about 500 mm x 500 mm x 130 mm) that holds a permeable bag containing a plant-growing medium (replacement for soil). The front face of the module has multiple openings for plants to protrude out from the bag inside. Plant roots are imbedded in the medium. A fan positioned at a central opening on the module‟s back face drives air through the medium-plant-roots mix and then onward through the plants‟ canopy; and these would help to remove both gaseous and particulate pollutants from the air. Drip-irrigation water is dispensed from a tube running along the open top-face of the module. The module has also a small drainage hole on its bottom face. Pressure drop across the module, air-flow distribution through it as well as flow rate have been obtained, in terms of variable parameters which include moisture content, growing-medium-plant-roots mix and plant type. The measurements help to determine the pattern of flow resistances which in turn will be used in a future CFD (Computational Fluid Dynamics) analysis for improving the design of the module, such that more appropriate flow distribution and flow rate would be achieved. All this is in addition to the better understanding of air flow through complex moist porous media.

Three different submerged membrane hybrid systems (SMHSs) namely submerged membrane coagulation hybrid system (SMCHS), submerged membrane adsorption hybrid system (SMAHS), and submerged membrane coagulation–adsorption hybrid system (SMCAHS) were studied as pretreatment systems to seawater reverse osmosis (SWRO). The performances of these SMHSs were compared with that of submerged membrane system (without any coagulation or adsorption) in terms of trans-membrane pressure (TMP) development, critical flux, ultrafilter modified fouling index (UF-MFI), dissolved organic carbon (DOC) removal efficiency, and the removal of detailed organic fractions. The experimental results show that pretreatment by SMCAHS led to the best results in terms of organic removal and critical flux. With the low doses of ferric chloride (FeCl 3 ) and powder activated carbon (PAC) of 0.5 mg of Fe 3+ /L and 0.5 g of PAC/L, respectively, this hybrid system could remove 72% of DOC and reduce the UF-MFI nearly five times. The initial DOC and UF-MFI of seawater used in this study were 2.53 mg/L and 14,165 s/L 2 , respectively. The application of three different membrane fouling models namely pore blockage, pore constriction, and cake formation models showed that cake formation was the predominant fouling mechanisms causing fouling in SMHSs.

In this study, the performance of Purolite®A500PS in effluent organic matter (EfOM) removal was evaluated through adsorption equilibrium, kinetics and fluidized bed experiments. It was found that the maximum EfOM removal capacity of Purolite®A500PS calculated by the Langmuir isotherm was 50.9 mg DOC/g Purolite®A500PS. The results also showed that fluidized bed operational conditions strongly affected the EfOM removal efficiency. A fluidized bed packed with Purolite®A500PS can maintain a consistent EfOM removal efficiency of more than 80% with more than 800 bed volumes from 10 mg DOC/L of synthetic wastewater. A majority of hydrophilic compounds (76.4%) and a significant amount of hydrophobic compounds (55%) were removed by the Purolite®A500PS fluidized bed. The Purolite®A500PS fluidized bed was also found to remove a majority of biopolymer (98.5%), humic substances (86.5%), and low molecular weight neutrals (83.3%).

Deep bed filtration has traditionally been used as a pretreatment in seawater desalination. The performance of contact flocculation–filtration (CFF) as pretreatment of seawater reverse osmosis (SWRO) was evaluated in terms of pressure drop through the filter and removal of organics and turbidity. The average turbidity, total suspended solids, and dissolved organic carbon (DOC) of raw seawater were 0.92 NTU, 3.6, and 1.12 mg/L, respectively. The performances of CFF were experimentally evaluated with different flocculant doses (0.5–3.0 mg Fe3+/L) and rapid mixing times (1.7–14.4 s). Here rapid mixing was performed in a spiral flocculation unit which consisted of a PVC tube of length 0.5 m and internal diameters of 0.16 and 0.40 cm. The experimental results show that the filtration rate of 10.0 m/h led to an extensive increase in both head loss (pressure drop) and turbidity as compared to those at filtration rates of 5.0 and 7.5 m/h. The head loss also significantly decreased when the flocculant dos...

© 2015 Springer International Publishing Switzerland. Chemical methods have been used for the remediation of arsenic (As)-contaminated water; however, ecological consequences of these methods have not been properly addressed. The present study evaluated the effects of the Fe-oxide-coated sand (IOCS) remediation method on As toxicity to freshwater organisms (Lemna disperma, Chlorella sp. CE-35, and Ceriodaphnia cf. dubia). The As removal efficiency by IOCS decreased substantially with time. The IOCS remediation method was less effective at suppressing the toxicity of AsV than AsIII to L. disperma but was highly effective in reducing both the AsIII and AsV toxicity to C. cf. dubia. The growth of Chlorella sp. was significantly higher (p < 0.05) in remediated and pre-remediated water than in controls (non-As-contaminated filtered Colo River water) for AsIII, while the opposite was observed for AsV, indicating that AsV is more toxic than AsIII to this microalga. Although the IOCS can efficiently remove As from contaminated water, residual As and other constituents (e.g. Fe, nitrate) in the remediated water had a significant effect on freshwater organisms.

Submerged microfiltration system coupled with in-line flocculation as pretreatment for seawater reverse osmosis has the potential to remove organic compounds and mitigate fouling. The effect of flocculation on the performance of microfiltration (MF) was investigated using two flocculants, namely, modified poly ferric silicate (PFSi-δ) and ferric chloride (FeCl 3 ). The experimental results were analysed in terms of organic removal efficiency and critical flux. Both PFSi-δ and FeCl 3 were found to be suitable as pretreatment because of their capacity in removing organic compounds. The results show that PFSi-δ was better than FeCl 3 in terms of removing turbidity and dissolved organic carbon (DOC), particularly in removing hydrophilic compounds. The highest DOC removals of 68% and 57% were obtained when PFSi-δ at a dose of 1.2 mg Fe 3+ /L and FeCl 3 at 3 mg Fe 3+ /L were used, respectively. It was observed that PFSi-δ (1.2 mg Fe 3+ /L) and FeCl 3 (3 mg Fe 3+ /L) led to an increase of critical flux from 20 L/m 2 h to 35 L/m 2 h and 55 L/m 2 h, respectively.

In this study, Purolite®A500PS was used to remove effluent organic matter in a fluidised bed and submerged membrane hybrid system (SMHS). It was found that the fluidised bed purolite column can effectively remove 73% of dissolved organic compound (DOC) from synthetic biologically treated sewage effluent (BTSE). DOC removal can be reduced further, by up to 95% when the fluidised bed purolite column was combined with a treatment by granular activated carbon column. Purolite®A500PS was also used as an adsorbent in the SMHS. The results showed that critical flux of the SMHS depend on the purolite size. Critical fluxes of SMHS were 30 and 35 L/m2.h where 0.1 g/L of purolite of sizes below 150 µm and 150–300 µm were used respectively. The removal efficiency of natural organic matter from synthetic BTSE by SMHS was a function of purolite dose. The removal efficiency increased from less than 60% to more than 70% when the purolite dose increased from 0.05g/L to 0.1g/L.

Flocculation alone and flocculation coupled with oxidation process were used for removing organic matter from biologically treated sewage effluent. The performances of different flocculants such as ferric sulphate, ferric nitrate, ferric chloride, and aluminium sulphate were experimentally evaluated. Among the flocculants tested, ferric chloride was selected because of its highest dissolved organic carbon (DOC) removal efficiency (67%) and the large size of the floc (mean size d(0.5) = 53.04 µm). The optimum dosage of FeCl3 was determined as 16 mg (Fe3+)/L. Different fractionation of organic matter before and after the flocculation process was analyzed. It was observed that FeCl3 could remove 90% of hydrophobic compounds and 61% of hydrophilic compounds. Oxidation process by Fenton reagent coupled with flocculation was also trialed. It is observed that DOC removal efficiency of Fenton reagent coupled with flocculation could reach 86%. The combination of flocculation and Fenton reagent increased the hydrop...

In this study, a commonly used ferric chloride was utilised as coagulant for removing organic compounds from seawater. More than 57% of dissolved organic carbon (DOC) was removed at optimum dosage of 3 mg Fe+3/L. The coagulation by FeCl3 at optimum dosage could remove a majority (95%) of hydrophobic compounds. The results from Liquid Chromatography - Organic Carbon Detector showed that only

Results of preliminary studies of last remnants of Glyptostrobus pensilis native populations in Vietnam are presented in the paper in form of standard taxonomical treatment with comments on ecology, population structure and natural conditions of its habitats. Perspectives of conservation of this unique Tertiary relict are specially assessed and discussed.

© 2015 Elsevier B.V. All rights reserved. Abstract Wastewater reclamation plants using reverse osmosis as the final polishing treatment produce reverse osmosis concentrate (ROC), which consists of high salinity, nutrients and (recalcitrant) organics. The ROC collected from the water reclamation plant in Sydney was treated with a micro filtration (MF)-GAC hybrid system that removed natural and synthetic organics prior to its discharge into the environment. The MF-GAC hybrid system's performance was studied in terms of trans-membrane pressure (TMP) development, and organics removal. These features were measured using liquid chromatography-organic carbon detection (LC-OCD), Fluorescence Excitation-Emission matrix (F-EEM), and Liquid chromatography with tandem mass spectroscopy (LC-MS). Adding GAC into the membrane reactor reduced the TMP by reducing membrane fouling both through mechanical scouring and pre-adsorption of organics. F-EEM confirms the removal of humics-like and fulvic-like compounds by GAC from ROC. Pharmaceuticals and personal care products (PPCPs) were also removed by the MF-GAC hybrid system.

© 2014 Elsevier B.V. Micro-filtered, biologically treated sewage effluent (BTSE) generally has high sodium adsorption ratio (SAR) and sodium (Na) and chloride (Cl) concentrations. Therefore it cannot be directly used for irrigating sensitive crops. A study was conducted on a micro-filtered BTSE from a Sydney water treatment plant to determine whether the BTSE can be treated using nanofiltration (NF) and reverse osmosis (RO) to bring these risk parameters within safety limits. The study showed that using NF and RO alone could not produce the required ratio of SAR. Furthermore, NF alone did not remove the necessary levels of Na and Cl ions while RO did. However, blending equal proportions of NF permeate and RO permeate obtained from a two stages hybrid treatment system consisting of NF followed by RO resulted in a product quality suitable for irrigation in terms of the above mentioned risk factors. Utilizing NF prior to RO reduced the RO membrane fouling as well. Both NF and RO removed most of the pharmaceutical and personal care products from the feed water and this may subsequently protect soil and ground water from potential hazards.

This study explores the potential of removing phosphorus from aqueous solutions and sewage by Zr(IV)-loaded okara (ZLO) in the fixed-bed column. Soybean residue (okara) was impregnated with 0.25 M Zr(IV) solution to prepare active binding sites for phosphate. The effect of several factors, including flow rate, bed height, initial phosphorus concentration, pH and adsorbent particle size on the performance of ZLO was examined. The maximum dynamic adsorption capacity of ZLO for phosphorus was estimated to be 16.43 mg/g. Breakthrough curve modeling indicated that Adams–Bohart model and Thomas model fitted the experimental data better than Yoon–Nelson model. After treatment with ZLO packed bed column, the effluent could meet the discharge standard for phosphorus in Australia. Successful desorption and regeneration were achieved with 0.2 NaOH and 0.1 HCl, respectively. The results prove that ZLO can be used as a promising phosphorus adsorbent in the dynamic adsorption system.

Trace elements (TEs) in road-deposited sediments (RDS) can be transported by stormwater to neighbouring water bodies to cause aquatic pollution. A study was conducted in Kogarah Bay, Sydney, Australia, to assess the possible sources and potential mobility of TEs in RDS and the contribution to the TE load to the adjacent waterbed sediments in canals and the bay. Of the 11 TEs analysed, pseudo-total concentrations of zinc (Zn), copper (Cu), vanadium (V), chromium (Cr), and antimony (Sb) were greatly enriched in RDS over baseline soils (top 10 cm depth) collected in bushlands. All TE concentrations in waterbed sediments (top 10 cm depth) were similar to those in baseline soils but lower than in RDS. Correlation and principal component analyses revealed that Zn, Cu, Cr and Sb were related to each other in RDS, and probably originated from tyres and brake linings. Vanadium occurred in another component, likely to have originated mainly from road asphalt. Pseudo-total and mobile-fraction (0.1 m acetic acid, pH 2.85 extraction) TE concentrations in RDS were: iron > manganese, Zn > Cu, lead > Cr, nickel, V, Sb, cadmium. The potential ecological TE risk was low to medium in RDS but low in baseline soils and waterbed sediments.

Arsenic (As) contamination in drinking water is a serious problem in a number of countries in the world, especially in small communities and developing countries. Arsenic is related to many health diseases. Several technologies such as coagulation, adsorption, ion exchange and membrane processes, etc., are used in removing arsenic from water. In this study, a new material, namely iron-coated sponge (IOCSp), was developed and used to remove As, and it was found that IOCSp has a high capacity for removing both As(V) and As(III). Each gram of IOCSp adsorbed about 160 µg of As upon a 9-h contact of IOCSp with As solution. A dynamic filter column conducted showed that even a small quantity of IOCSp (8 g) could reduce As from 156 µg/L to a concentration of less than 50 µg/L while treating 75 L of groundwater contaminated with arsenic. Both the filtration rate and the size of the sponge had an effect on effluent quality, and the amount of water treated to the acceptable quality.

Arsenic (As) is a highly toxic metalloid found in ground and surface water. Arsenic contamination in drinking water leads to harmful effects on human health. To eliminate arsenic from drinking water, several technologies such as coagulation, adsorption, ion exchange, filtration, membrane processes, etc., have been used. In this study, three technologies were evaluated for arsenic removal. Results from batch kinetic experiments showed that iron coated sand (IOCS-2) can remove more than 90% of As from synthetic water. Experiments were conducted with three different pH values (6, 7, and 8) and an initial As concentration of 260 μg/L. A new material, developed in this study, namely iron coated sponge (IOCSp), was found to have a high capacity in removing both As (V) and As (III). Each gram of IOCSp adsorbed about 160 μg of As within a 9-hour contact period of IOCSp with As solution. Low pressure nanofiltration removed more than 94% of As from an influent containing 440 μg/L As. The applied pressure was varied from 85 to 500 kPa. © 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Cationization of agricultural by-products using metal salts is widely used to activate their phosphorous capture ability. This study developed three kinds of new metal loaded soybean milk by-product 'okara' for phosphorus biosorption. A comparative study among these biosorbents was carried out with respect to their performances in terms of affinity, stability and reusability. Zirconium loaded okara (ZLO) was found to have the highest affinity towards PO(4)(3-) anions (47.88 mg/g), followed by iron/zirconium loaded okara--IZLO (40.96 mg/g) and iron loaded okara--ILO (16.39 mg/g). ZLO was successfully desorbed with 0.2M NaOH and activated with 0.1 HCl prior to the next cycle. After five consecutive cycles, the efficiency of both adsorption and desorption of ZLO remained about 85% whilst no Zr(IV) leakage was observed. Conversely, IZLO and ILO suffered from vital short comings such as high metal release and/or sharp reduction in PO4(3-) sequestering capability after multi operation cycles.

© 2014 The Korean Society of Industrial and Engineering Chemistry. Applying pre-treatments to remove dissolved organic matter from reverse osmosis (RO) feed can help to reduce organic fouling of the RO membrane. In this study the performance of granular activated carbon (GAC), a popular adsorbent, and purolite A502PS, an anion exchange resin, in removing effluent organic matter (EfOM) from RO feed collected from a water reclamation plant located at Sydney Olympic Park, Australia were evaluated and compared through adsorption equilibrium, kinetics and fluidized bed experiments. The maximum adsorption capacity (Qmax) of GAC calculated from the Langmuir model with RO feed was 13.4mg/g GAC. The operational conditions of fluidized bed columns packed with GAC and purolite A502PS strongly affected the removal of EfOM. GAC fluidized bed with a bed height of 10cm and fluidization velocity of 5.7m/h removed more than 80% of dissolved organic carbon (DOC) during a 7h experiment. The average DOC removal was 60% when the bed height was reduced to 7cm. When comparing GAC with purolite A502PS, more of the later was required to remove the same amount of DOC. The poorer performance of purolite A502PS can be explained by the competition provided by other inorganic anions present in RO feed. A plug flow model can be used to predict the impact of the amount of adsorbent and of the flow rate on removal of organic matter from the fluidized bed column.

Sixteen polycyclic aromatic hydrocarbons (PAHs) considered as priority environmental pollutants were analysed in surface natural soils (NS), road-deposited sediments (RDS), and water sediments (WS) at Kogarah in Sydney, Australia. Comparisons were made of their concentration distributions, likely sources and potential toxicities. The concentrations (mg/kg) in NS, RDS, and WS ranged from 0.40 to 7.49 (mean 2.80), 1.65 to 4.00 (mean 2.91), and 0.49 to 5.19 (mean 1.76), respectively. PAHs were dominated by relatively high molecular weight compounds with more than three fused benzene rings, indicating that high temperature combustion processes were their predominant sources. The proportions of high molecular weight PAHs with five or six fused benzene rings were higher in NS than in RDS, whereas the low molecular weight PAHs were higher in RDS. Concentrations of all PAHs compounds were observed to be the lowest in WS. The concentrations of most of the high molecular weight PAHs significantly correlated with each other in RDS and WS. All PAHs (except naphthalene) were significantly correlated in NS suggesting a common PAH source. Ratios for individual diagnostic PAHs demonstrated that the primary source of PAHs in WS and NS was of pyrogenic origin (combustion of petroleum (vehicle exhaust), grass, and wood) while in RDS it was petrogenic (i.e. unburned or leaked fuel and oil, road asphalt, and tyre particles) as well as pyrogenic. The potential toxicities of PAHs calculated using a toxicity equivalent quotient (TEQ) were all low but higher for NS compared to WS and RDS. Refereed/Peer-reviewed

This critical review discusses the potential use of agricultural waste based biosorbents (AWBs) for sequestering heavy metals in terms of their adsorption capacities, binding mechanisms, operating factors and pretreatment methods. The literature survey indicates that AWBs have shown equal or even greater adsorption capacities compared to conventional adsorbents. Thanks to modern molecular biotechnologies, the roles of functional groups in biosorption process are better understood. Of process factors, pH appears to be the most influential. In most cases, chemical pretreatments bring about an obvious improvement in metal uptake capacity. However, there are still several gaps, which require further investigation, such as (i) searching for novel, multi-function AWBs, (ii) developing cost-effective modification methods and (iii) assessing AWBs under multi-metal and real wastewater systems. Once these challenges are settled, the replacement of traditional adsorbents by AWBs in decontaminating heavy metals from wastewater can be expected in the future.

Banana peel, a fruit waste were used to produce bioadsorbent through environment friendly process. It were cut, washed, dried, grounded into powder and used for copper removal. Copper adsorption onto banana peel was depended upon the controlling parameters such as particle size, doses, pH, contact time, agitation speed and temperature. Slightly acidic water (pH = 6) was found to be suitable for copper removal. Equilibrium data were well fitted (R2 = 0.998) with the Langmuir and Freundlich isotherms. The monolayer adsorption capacity was 27.78 mg/g. The calculated RL and 'n' values has proved the favorability of copper adsorption onto banana peel. Copper adsorption was followed the second order kinetic properly rather than other models. The equilibrium adsorption capacity was 1.439, 8.849, 18.182, 31.250 and 71.429 mg/g when initial copper concentrations were 10, 50, 100, 200, and 400 mg/l respectively. Solvent 0.1N Sulphuric acid showed higher desorption of copper (94%) and adsorption-desorption process can be continued till seven cycles efficiently. © 2012, International Journal of GEOMATE.

Biofouling on reverse osmosis (RO) membranes is the most serious problem which affects desalination process efficiency and increases operation cost. The biofouling cannot be effectively removed by the conventional pre-treatment traditionally used in desalination plants. Hybrid membrane systems coupling the adsorption and/or coagulation with low-pressure membranes can be a sustainable pre-treatment in reducing membrane fouling and at the same time improving the feed water quality to the seawater reverse osmosis. The addition of powder activated carbon (PAC) of 1.5 g/L into submerged membrane system could help to remove significant amount of both hydrophobic compounds (81.4%) and hydrophilic compounds (73.3%). When this submerged membrane adsorption hybrid system (SMAHS) was combined with FeCl(3) coagulation of 0.5 mg of Fe(3+)/L, dissolved organic carbon removal efficiency was excellent even with lower dose of PAC (0.5 g/L). Detailed microbial studies conducted with the SMAHS and the submerged membrane coagulation-adsorption hybrid system (SMCAHS) showed that these hybrid systems can significantly remove the total bacteria which contain also live cells. As a result, microbial adenosine triphosphate (ATP) as well as total ATP concentrations in treated seawater and foulants was considerably decreased. The bacteria number in feed water prior to RO reduced from 5.10E(+06) cells/mL to 3.10E(+03) cells/mL and 9.30E(+03) cells/mL after SMAHS and SMCAHS were applied as pre-treatment, respectively. These led to a significant reduction of assimilable organic carbon (AOC) by 10.1 μg/L acetate-C when SMCAHS was used as a pre-treatment after 45-h RO operation. In this study, AOC method was modified to measure the growth of bacteria in seawater by using the Pseudomonas P.60 strain.

Palm oil fruit shells were evaluated as a new bioadsorbent to eliminate toxic copper from water and wastewater. Without any chemical treatment, palm oil fruit shells were washed, dried and grounded into powder (75 μm) for use in the experiments. Characterization showed mesopore based bioadsorbent was prepared from palm oil fruit shells. The results indicate that the highest Cu removal efficiency was found in an aqueous solution with pH of 6.5. The equilibrium sorption capacity of copper was significantly high (between 28 and 60 mg/g) at room temperature. Nonlinear regression analyses for isotherm models revealed that three-parameter isotherms had a better fit to the experimental data (R(2)0.994) than that of two-parameter isotherms. The copper sorption system was heterogeneous as the values of exponents were lying between 0 and 1. The highly correlated pseudo-second-order kinetics model (R(2)0.998) ascertained the applicability of copper removal by palm oil fruit shells.

Magnetic Ion Exchange Resin (MIEX®) is effective in removing the majority of organic carbon from biologically treated wastewater. It removed 77% of dissolved organic carbon (DOC) from synthetic wastewater when operated in batch mode using a MIEX® concentration of 10. mL/L. A pseudo second-order reaction rate model namely the Ho model was used for the kinetic study and it was found that it provided a realistic description of the adsorption kinetics of DOC. A fluidised bed MIEX® contactor effectively removed organic matter from synthetic biologically treated sewage effluent with more than 60% DOC removal even after 172 bed volumes. The regenerated MIEX® resin did not display any significant reduction in its ability to remove organic matter. © 2011 Elsevier B.V.

Millions of people worldwide are at risk from the presence of arsenic in groundwater. In this study, adsorption equilibrium and long term experiments were carried out to evaluate the performance of iron oxide coated sponge (IOCSp) in arsenic removal. It was found that maximum adsorption capacity of IOCSp for As(III) and As(V) calculated by Sips isotherm was 4.2 and 4.6 mg/g of IOCSp, respectively. A filter packed with small amount of 25 g IOCSp maintained a consistent arsenic removal efficiency of 95% from synthetic solution containing arsenic concentration of as high as 1000 microg/L. This produced a throughput volume of 153 and 178 L of water containing As(III) and As(V), respectively before any need for regeneration or disposal of IOCSp. IOCSp could be regenerated by washing it with NaOH solution. The dynamic (column) adsorption kinetics were successfully predicted by the Thomas and Nikolaidis modified models.

There is a global need to develop low-cost technologies to remove arsenic from water for individual household water supply. In this study, a purified and enriched waste material (treated magnetite waste, TMW) from the Trai Cau's iron ore mine in the Thai Nguyen Province in Vietnam was examined for its capacity to remove arsenic. The treatment system was packed with TMW that consisted of 75% of ferrous-ferric oxide (Fe(3)O(4)) and had a large surface area of 89.7 m(2)/g. The experiments were conducted at a filtration rate of 0.05 m/h to treat groundwater with an arsenic concentration of 380 microg/L and iron, manganese and phosphate concentrations of 2.07 mg/L, 0.093 mg/L and 1.6 mg/L respectively. The batch experimental results show that this new material was able to absorb up to 0.74 mg arsenic/g. The results also indicated that the treatment system removed more than 90% arsenic giving an effluent with an arsenic concentration of less than 30 microg/L while achieving a removal efficiency of about 80% for Mn(2 + ) and PO(4) (3-). This could be a promising and cost-effective new material for capturing arsenic as well as other metals from groundwater.

One of the problems in drinking water that raises concern over the world is that millions of people still have to use arsenic-contaminated water. There is a worldwide need to develop appropriate technologies to remove arsenic from water for household and community water supply systems. In this study, a new material namely iron oxide coated sponge (IOCSp) was developed and used to remove arsenic (As) from contaminated groundwater in Vietnam. The results indicated that IOCSp has a high capacity in removing both As (V) and As (III). The adsorption capacity of IOCSp was up to 4.6 mg As/g IOCSp, showing better than many other materials. It was observed from a pilot study that a small quantity of IOCSp (180 g) could reduce As concentration of 480 μg/L in 1.5 m3 of contaminated natural water to below 40 μg/L. In addition, an exhausted IOCSp, containing a large amount of arsenic (up to 0.42 wt %) could safely be disposed through the solidification/stabilization with cement. Addition of fly ash also reduced the amount of arsenic in the leachate.

Arsenic is a toxic semi-metallic element that can be fatal to human health. Arsenic pollution in water is found in many parts of the world, especially in developing countries such as Bangladesh, India, Nepal, and Vietnam. Photo-oxidation experiments with titanium dioxide (TiO2) as photo-catalyst showed that photo-oxidation of As(III) to As(V) is possible within minutes. Further, TiO2 can also adsorb both As(III) and As(V) on its surface. Photo-catalysis reaction with TiO2 reduced about 98% of arsenite from water containing 500 μg/L of arsenite. By adding nano-scale zero valent iron (nZVI) of 0.05 g/L in the photo-reactor, arsenic removal can be significantly enhanced. Further the TiO2 requirement is five times less in this photo-catalysis nZVI hybrid system. The photo-catalytic degradation processes was modeled using the first-order, second-order and Langmuir-Hinshelwood kinetics equations and removal rates were simulated. © 2007 Elsevier B.V. All rights reserved.

Arsenic (As) contamination in water has raised a grave concern in many regions of the world. Arsenic can lead to a number of health problems even at very low concentration. This paper presents the laboratory-scale experimental results on the specific treatment technology: iron coated sponge (IOCSp) adsorption in As removal. The results indicated that IOCSp could remove 47.3% to 65% of As (III) and As (V) after a 1 hour contact with IOCSp (initial As concentration = 260 μg/l; 0.15g sponge/100ml solution). A nine hour-adsorption led to a very high As removal efficiency (more than 92.4% removal for both As (III) and As (V)). Each gram of IOCSp adsorbed about 160μg of As (III) and As (V) upon a 9 hour - contact of IOCSp with the As solution. After adsorption, IOCSp can be easily regenerated by NaOH.

Arsenic (As) contamination in groundwater raises grave concerns in many parts of the world. Arsenic can cause severe health problems even at very low concentration. In the first part of this review, the available technologies to treat As-rich water are discussed. It was found that even conventional technologies, which can be readily adopted in rural areas of the developing countries, can reduce As concentrations to the required level. The efficiency of the treatment technologies is better for removing As(V) than it is for As(III). The second part of this paper presents laboratory-scale experimental results with respect to specific treatment technologies, such as high-rate flocculation and a new membrane-adsorption system, for As removal. The results indicate that up to 78% of the As was removed when using a packed polystyrene-bead filter with in-line FeCl 3 addition at a high loading rate (30 m 3/m 2h). When powder-activated carbon (PAC) was used as an adsorbent for in-line addition to the membrane hybrid system, 87% removal of As was achieved when the mixing time was 2.7 min, the velocity gradient was 87.8 s -1, the average permeate flux was 760 L/m 2h and the membrane pore size was 0.2 m.