Empty Bed Contact Time Research Articles

Iron-based sorption materials for the removal of antimony from water

The objective of this work was to verify the sorption properties of granular filter materials (GEH, Bayoxide E33, CFH12) during the process of removing antimony from water. Pilot tests showed that the use of iron-based sorption materials could possibly decrease the antimony content in water to the values limited for drinking water. At an average concentration of antimony in raw water of 58.3 μg/L and the empty bed contact time 6.0 for GEH, 6.4 for Bayoxide E33 and 6.3 for CFH12, the value of bed volume 1,700 for GEH, 715 for Bayoxide E33 and 790 for CFH12 achieved at breakthrough concentration 5 μg Sb/L was determined. Considering the values of bed volume GEH was the most suitable adsorbent for the removal of antimony from water.

Removal of micropollutants during tertiary wastewater treatment by biofiltration: Role of nitrifiers and removal mechanisms

The objective of this study was to determine the extent to which a suite of organic micropollutants (MPs) can be removed by biological filtration and the role of bioavailability and ammonia oxidizing microorganisms (AOMs) in the biodegradation process. During approximately one year, laboratory-scale columns with 8 min empty bed contact time (EBCT) and packed with anthracite as filter media were used for treating a tertiary effluent spiked with a broad range of MPs at a target concentration of 2 μg L−1. In parallel columns, aerobic biomass growth was inhibited by using either the biocide sodium azide (500 mg L−1 NaN3) or allylthiourea (5 mg L−1 ATU), specifically inhibiting nitrifying bacteria. Once the biomass had colonized the media, around 15% of the dissolved organic carbon (DOC) contained in the untreated tertiary effluent was removed by non-inhibited columns. The removal of several MPs increased over time indicating the relevance of biological activity for the removal of MPs, while the negative control, the NaN3 inhibited column, showed no significant removal. Out of 33 MPs, 19 were recalcitrant (<25%) to biodegradation under aerobic conditions with the others exhibiting a diverse range of removal efficiency up to 95%. Through inhibition by ATU it was shown that nitrifying bacteria were clearly having a role in the degradation of several MPs, whereas the removal of other MPs was not affected by the presence of the nitrification inhibitor. A relationship between the qualitative assessment of sorption of MPs on granular activated carbon (GAC) and their removal efficiency by biodegradation on anthracite was observed. This result suggested that the affinity of the MPs for GAC media could be a useful indicator of the bioavailability of compounds during biofiltration on anthracite.

Adsorption of phosphate using calcined Mg3–Fe layered double hydroxides in a fixed-bed column study

A granular calcined Mg3–Fe LDH adsorbent was prepared by using co-precipitation method under low super saturation condition. The characteristic of the adsorbent was analyzed by powder X-ray diffraction (XRD) and scanning electron microscope (SEM). The continuous phosphate adsorption experiments were conducted in a glass fix-bed column. The results showed an increase in bed height and initial phosphate concentration improves the phosphate adsorption capacity probably due to the longer bed height allowing a longer empty bed contact time (EBCT) between the adsorbent and the adsorbate, meanwhile the higher initial phosphate concentration provides a higher driving force for the mass transfer; however, an increase in flow rate inhibits the phosphate adsorption due to the higher flow rate reduced the interaction time of the adsorbent in solution. The bed depth service time (BDST) model was found to predict the breakthrough curve well at a 0.024L/h flow rate and 10mg/L initial phosphate concentration using linear regression analysis. The Clark model was found to give a best fit to experiment data under various bed height, flow rate and initial phosphate concentration, followed by the Thomas and Yoon–Nelson models using non-linear regression analysis. The reusability experiment was conducted using actual anaerobic sludge filtrate as adsorbate. The results indicated that the adsorbent still had good selectivity in an anions coexisting solution, high phosphate adsorption capacity, and acceptable desorption efficiency.

Tobermolite를 이용한 폐수내 인산염제거

This study is carried out to get the basic design parameters for phospate removal facilites from wastewater by Tobermolite. The phosphate removal by the apatite formation on the surface was affected by several important factors, temperature, ions present in wastewater stream, contact time, recirculation rate, and etc. In case of the temperature, with the increase of temperature, the apatite formation was accelerated. When temperature increased from to , removal efficiency of phosphate increased from 83 % to 93 %. An increase of calcium and fluoride ion content increase the apatite formation, however, bicarbonate and magnesium ion inhibited the crystallization of apatite. As expected, when the recirculation rate was increased from 1 Q to 3 Q, at EBCT (Empty Bed Contact Time) 60min enhanced removal efficiency was observed. The more the recirculation rate increased, the more the removal efficiency increased. According to the results of column experiment using an actual wastewater with low and high phosphate concentration (5 mg/L and 50 mg/L-P), the removal efficiency was 77 % at EBCT of 45 min, and 80 % at 60 min. It was suggested that optimum EBCT was 45 min.

Assessment of manganese removal from over 100 groundwater treatment plants

The aim of this study was to make an inventory of water quality and operational parameters which could affect manganese removal through aeration and rapid sand filtration and to establish correlations between these parameters and manganese removal efficiency. The focus of the overview was on manganese removal efficiency in the first aeration-filtration stage of conventional groundwater treatment plants (GWTPs). Data from selected full-scale GWTPs have been collected, and univariate and multivariate statistical analyses were conducted. Multivariate statistics indicated that multiple parameters including NH 4 + removal efficiency, iron loading per filter run (FR) and pH of filtrate play a significant role in manganese removal, while other parameters (oxygen concentration in filtrate, filtration rate and empty bed contact time (EBCT)) were found to be of secondary importance. Univariate statistical assessment of the data suggests that very effective manganese removal can be achieved when all of the following conditions are met: NH 4 + removal efficiency >85%, pH of filtrate >7.1, iron loading per FR 2 , oxygen concentration in filtrate >1 mg O 2 /L, filtration rate 11.5 min.

Advanced treatment of recalcitrant textile wastewater and goal-oriented process design

This study was intended to evaluate the performance of a biological and a chemical treatment process of recalcitrant textile wastewater. The biological process consisted of Activated Sludge (AS) reactor followed by column reactor packed with cellimmobilized pellets. The chemical process consisted of coagulation/precipitation and ozone oxidation. Experiments were conducted by pilot-scale reactors fed with textile wastewater. The removal efficiency of BOD by AS process was 85%, but only 45% of the COD was removed, indicating the AS process was not satisfactory in removing recalcitrant organic matter. However, the packed-bed column reactor effectively removed the recalcitrant organic matter, showing stable performance at an empty bed contact time of 8. hours. Both PAC and ferric chloride appeared to be excellent coagulants for removal of the remained hardly-biodegradable COD. Although the previous biological processes and coagulation/precipitation had already removed 74% of the color in the influent, most of the remaining color was removed by ozone oxidation at a contact time of 20 minute. A combination of AS, PEG-pellet column, and coagulation/precipitation produced a good effluent quality which met the discharge standards of most Asian countries. Additionally, if the ozone oxidation was added, the effluent quality could meet more stringent standards of advanced countries.

Silica nanopowders/alginate composite for adsorption of lead (II) ions in aqueous solutions

The aim of the present work was to study the Pb(II) ions adsorption by entrapped silica nanopowders within calcium alginate to determine the isotherm, kinetic and thermodynamic of the adsorption process. According to the results, an optimal initial pH of 5.0 was found for the Pb(II) adsorption. The adsorbed Pb(II) ions reached to 36.51mg/g as the contact time increased to 180min at an initial Pb(II) concentration of 50mg/L. However, a contact time of 90min was selected as equilibrium time because of no significant increase in Pb(II) adsorption after this time. The results of isotherm and kinetic studies showed the Langmuir isotherm and pseudo-second order kinetic model were the best fitted models (R2>0.999). The maximum adsorption capacity for Pb(II) adsorption onto entrapped silica nanopowders was estimated to be 83.33mg/g. According to the Dubinin–Radushkevich (D–R) isotherm model, Pb(II) adsorption onto the composite follows a chemical mechanism (E=10kJ/mol). Negative ΔG° and ΔH° values indicated spontaneous and exothermic nature of the Pb(II) adsorption onto entrapped silica nanopowders, respectively. In addition, the results of continuous flow mode study exhibited that increasing empty-bed contact time (EBCT) from 5 to 20min resulted in increasing the specific throughput (St) from 8.42 to 11.22mL/g, respectively.

Removal of amoxicillin from contaminated water using NH4Cl-activated carbon: Continuous flow fixed-bed adsorption and catalytic ozonation regeneration

This study investigates the elimination of amoxicillin from water by adsorption onto NH4Cl-activated carbon (NAC) and standard activated carbon (SAC) in the fixed-bed columns with ozone-regeneration of the saturated carbon. Breakthrough curves for amoxicillin (AMX) adsorption were determined at various empty bed contact times (EBCTs) ranging from 2 to 10min. Results determined breakthrough times of 5.5–103h for the NAC bed and 10–98h for SAC bed. The breakthrough point adsorption capacity of NAC was much greater than that of SAC at each of the tested EBCTs. Based on the experimental data, the breakthrough point adsorption capacity of NAC increased from 73.3 to 274.1mg/g and that of SAC increased from around 31.6 to 65.2mg/g with an increased EBCT from 2 to 10min. The saturated NAC bed was completely regenerated in situ through a catalytic ozone-regeneration process with an ozone dose of 1.4mg-O3/min for 3h and the regenerated NAC demonstrated adsorption behavior similar to that of fresh NAC. The NAC-bed improved the quality of the contaminated real water from background contaminants and completely removed AMX. Therefore, the NAC fixed-bed adsorption and subsequent ozonation presents a promising and efficient process for the removal of AMX as an emerging contaminant from polluted water.

Fate of 17β-estradiol and 17α-ethinylestradiol in batch and column studies simulating managed aquifer recharge

Laboratory-scale batch and soil columns experiments were conducted to investigate the attenuation of estrogens (17β-estradiol and 17α-ethinylestradiol) during managed aquifer recharge. The role of microbial activity in the removal of selected estrogens was evaluated by comparing the results from biotic and abiotic batch experiments. Moreover, batch experiments were carried out using the sand media prepared over different acclimation periods to investigate the impact of acclimation periods on the removal of selected estrogens. Batch studies showed that adsorption was the dominant removal mechanism in the removal of 17β-estradiol and 17α-ethinylestradiol. 17β-estradiol and 17α-ethinylestradiol were attenuated by 99% and 96%, respectively, in batch experiments under oxic conditions. Redox conditions did not show any significant effect on the attenuation of 17β-estradiol. However, the net estrogenicity of 17β-estradiol remaining was lower under oxic conditions (130 ng estradiol-equivalents/L) than anoxic conditions (970 ng estradiol-equivalents/L). Column studies operated at 17 h of empty bed contact time also demonstrated that removal mechanism of 17α-ethinylestradiol was more dependent on adsorption than biodegradation.

Exceptional arsenic (III,V) removal performance of highly porous, nanostructured ZrO2 spheres for fixed bed reactors and the full-scale system modeling

Highly porous, nanostructured zirconium oxide spheres were fabricated from ZrO2 nanoparticles with the assistance of agar powder to form spheres with size at millimeter level followed with a heat treatment at 450 °C to remove agar network, which provided a simple, low-cost, and safe process for the synthesis of ZrO2 spheres. These ZrO2 spheres had a dual-pore structure, in which interconnected macropores were beneficial for liquid transport and the mesopores could largely increase their surface area (about 98 m2/g) for effective contact with arsenic species in water. These ZrO2 spheres demonstrated an even better arsenic removal performance on both As(III) and As(V) than ZrO2 nanoparticles, and could be readily applied to commonly used fixed-bed adsorption reactors in the industry. A short bed adsorbent test was conducted to validate the calculated external mass transport coefficient and the pore diffusion coefficient. The performance of full-scale fixed bed systems with these ZrO2 spheres as the adsorber was estimated by the validated pore surface diffusion modeling. With the empty bed contact time (EBCT) at 10 min and the initial arsenic concentration at 30 ppb, the number of bed volumes that could be treated by these dry ZrO2 spheres reached ∼255,000 BVs and ∼271,000 BVs for As(III) and As(V), respectively, until the maximum contaminant level of 10 ppb was reached. These ZrO2 spheres are non-toxic, highly stable, and resistant to acid and alkali, have a high arsenic adsorption capacity, and could be easily adapted for various arsenic removal apparatus. Thus, these ZrO2 spheres may have a promising potential for their application in water treatment practice.

Rapid adsorption of arsenic from aqueous solution by ferrihydrite-coated sand and granular ferric hydroxide

The efficiency of As removal by Fe oxyhydroxide-based adsorbents was studied. Water containing micro-molar concentrations of As was cleaned using columns containing ferrihydrite-coated grains of sand or the commercial material granular ferric hydroxide, GFH®. Adsorption of considerable amounts of arsenate and arsenite were achieved on a sub-minute time scale with both adsorbents. Furthermore, efficient adsorption on GFH® can be achieved in seconds of empty bed contact time. Arsenate adsorption was affected by moderate changes in pH, while such an effect was negligible for arsenite. At slightly acidic pH substantially higher amounts of arsenate could be adsorbed. The Fe content of the coated sand was varied and it was found that more As was adsorbed on grains with a higher Fe content, however, the relationship was far from proportional. This is supported by scanning electron microscopy and energy dispersive spectroscopy, which showed that in addition to the occurrence of Fe in compounds coating the flakes, it also occurred adsorbed to the surface. The Fe oxyhydroxide coating was confirmed to be ferrihydrite using EXAFS spectroscopy. Batch experiments with ferrihydrite support the view that almost all can be adsorbed with a sufficient surplus of Fe oxide/hydroxide mineral suspension.

Pretreatment of 2,4-dinitroanisole (DNAN) producing wastewater using a combined zero-valent iron (ZVI) reduction and Fenton oxidation process

A combined zero-valent iron (ZVI) reduction and Fenton oxidation process was tested for the pretreatment of 2,4-dinitroanisole (DNAN) producing wastewater. Operating conditions were optimized and overall performance of the combined process was evaluated. For ZVI process, almost complete reduction of nitroaromatic compounds was observed at empty bed contact time (EBCT) of 8h. For Fenton process, the optimal pH, H2O2 to Fe(II) molar ratio, H2O2 dosage and hydraulic retention time (HRT) were found to be 3.0, 15, 0.216mol/L and 5h, respectively. After pretreatment by the combined ZVI-Fenton process under the optimal conditions, aromatic organic compound removal was as high as 77.2%, while the majority of COD remained to be further treated by sequent biological process. The combined anaerobic-aerobic process consisted of an anaerobic baffled reactor (ABR) and a moving-bed biofilm reactor (MBBR) was operated for 3 months, fed with ZVI-Fenton effluent. The results revealed that the coupled ZVI-Fenton-ABR-MBBR system was significantly efficient in terms of correcting the effluent's main parameters of relevance, mainly aromatic compounds concentration, COD concentration, color and acute toxicity. These results indicate that the combined ZVI-Fenton process offers bright prospects for the pretreatment of wastewater containing nitroaromatic compounds.

Removal of reactive yellow dye by adsorption onto activated carbon using simulated wastewater

Reactive yellow dye was investigated as an adsorbate to be removed onto activated carbon during batch and continuous processes. A Fourier transform infrared (FTIR) analysis was carried out before and after onto the activated carbon adsorption. Thermodynamic parameters: Gibbs free energy, enthalpy change, and entropy change were found at different temperatures. Isotherm experiments were carried out at different conditions: adsorbent dosage (0.1–0.5 g), temperature (20–50°C), pH (2.5–9), and initial concentration (50–150 mg/l). Langmuir, Freundlich, and (Brunauer, Emmet, and Teller) BET isotherm model were used to fit the results. Kinetics mechanism of mass transfer pseudo-first-order, pseudo-second-order, and intraparticale diffusion models were studied. Fixed bed column experiments were carried out at different bed heights (0.05–0.15 m), initial concentration (10–50 mg/l), and flow rate (4–12) 10−6 m3/min to find empty bed contact time at break though point. Bed depth service time model was used as a shortcut model to predicate the breakthrough curves comparing with experimental data.

Application of bacteriophages to selectively remove Pseudomonas aeruginosa in water and wastewater filtration systems

Water and wastewater filtration systems often house pathogenic bacteria, which must be removed to ensure clean, safe water. Here, we determine the persistence of the model bacterium Pseudomonas aeruginosa in two types of filtration systems, and use P. aeruginosa bacteriophages to determine their ability to selectively remove P. aeruginosa. These systems used beds of either anthracite or granular activated carbon (GAC), which were operated at an empty bed contact time (EBCT) of 45 min. The clean bed filtration systems were loaded with an instantaneous dose of P. aeruginosa at a total cell number of 2.3 (±0.1 [standard deviation]) × 107 cells. An immediate dose of P. aeruginosa phages (1 mL of phage stock at the concentration of 2.7 × 107 PFU (Plaque Forming Units)/mL) resulted in a reduction of 50% (±9%) and >99.9% in the effluent P. aeruginosa concentrations in the clean anthracite and GAC filters, respectively. To further evaluate the effects of P. aeruginosa phages, synthetic stormwater was run through anthracite and GAC biofilters where mixed-culture biofilms were present. Eighty five days after an instantaneous dose of P. aeruginosa (2.3 × 107 cells per filter) on day 1, 7.5 (±2.8) × 107 and 1.1 (±0.5) × 107 P. aeruginosa cells/g filter media were detected in the top layer (close to the influent port) of the anthracite and GAC biofilters, respectively, demonstrating the growth and persistence of pathogenic bacteria in the biofilters. A subsequent 1-h dose of phages, at the concentration of 5.1 × 106 PFU/mL and flow rate of 1.6 mL/min, removed the P. aeruginosa inside the GAC biofilters and the anthracite biofilters by 70% (±5%) and 56% (±1%), respectively, with no P. aeruginosa detected in the effluent, while not affecting ammonia oxidation or the ammonia-oxidizing bacterial community inside the biofilters. These results suggest that phage treatment can selectively remove pathogenic bacteria with minimal impact on beneficial organisms from attached growth systems for effluent quality improvement.

Granular iron oxide adsorbents to control natural organic matter and membrane fouling in ultrafiltration water treatment

Fine iron oxide particles (IOPs) are effective in removing natural organic matter (NOM) that causes membrane fouling in water treatment, but the separation of used IOPs is problematic. This study focused on the fabrication and use of granular iron oxide adsorbents, in combination with ultrafiltration (UF) membranes while investigating the NOM removal efficiency and fouling control. Sulfonated styrene-divinylbenzene copolymer beads were coated with two types of iron oxides (ferrihydrite and magnetite) and their performances were compared to that of fine IOPs. A significant amount of iron oxide coating (52–63 mg of Fe per g bead) was achieved by means of electrostatic binding and hydrolysis of iron ions. Iron oxide coated polymer (IOCP) beads were able to remove some amounts (∼20%) of dissolved organic carbon (DOC) comparable to that achieved by IOPs within a short period of time (<15 min). Regenerated IOCPs exhibited the same sorption capacity as the fresh ones. The integrated IOCP/UF system operation with a 15-min empty bed contact time and 10-h cyclic regeneration maintained the 20% DOC removal with no sign of significant membrane fouling. In contrast, a sharp transmembrane pressure buildup occurred in the UF system when no iron oxide pretreatment was applied, regardless of the types of membranes tested. Iron oxide adsorbed the NOM fraction with molecular weights of >1000 kDa which is believed to be responsible for severe UF fouling.

Recalcitrant organic matter removal from textile wastewater by an aerobic cell-immobilized pellet column

The treatment of textile wastewater is difficult because of its recalcitrant organic content. The biological removal of recalcitrant organics requires a long retention time for microbial growth. Activated sludge was immobilized in a polyethylene glycol pellet to allow for sufficient sludge retention time. The pellets were filled in an aerobic cell-immobilized pellet column (CIPC) reactor in order to investigate the removal of recalcitrant organics from textile wastewater. A textile wastewater effluent treated by a conventional activated sludge reactor was used as a target wastewater. The chemical oxygen demand (COD) removal efficiency of the aerobic CIPC reactor at various empty bed contact times was in the range of 42.2-60.5%. Half of the input COD was removed in the lower part (bottom 25% of the reactor volume) of the reactor when the organic loading rate was less than 1.5 kg COD/(m(3)•d). About 15-30% of the input COD was removed in the remaining part of the column reactor. The COD removed in this region was limitedly biodegradable. The biodegradation of recalcitrant organics could be carried out by the interactional functions of the various bacteria consortia by using a cell-immobilization process. The CIPC process could effectively treat textile wastewater using a short retention time because the microorganisms that degrade limitedly biodegradable organics were dominant in the reactor.

More efficient alkalisation with ground limestone in groundwater treatment

Research Article| May 01 2013 More efficient alkalisation with ground limestone in groundwater treatment J. Sallanko; J. Sallanko 1Department of Process Engineering, Water and Environmental Laboratory, P.O. BOX 4300, 90014 University of Oulu, Finland E-mail: jarmo.sallanko@oulu.fi Search for other works by this author on: This Site PubMed Google Scholar J. Hietala; J. Hietala 2Ahma Environment Ltd, Teollisuustie 6, P.O. BOX 96, 96101 Rovaniemi, Finland Search for other works by this author on: This Site PubMed Google Scholar R. Lindström; R. Lindström 3Oulu Waterworks, P.O. BOX 35, 90015 City of Oulu, Finland Search for other works by this author on: This Site PubMed Google Scholar A. Kytövaara; A. Kytövaara 4Kangasala Waterworks, P.O. BOX 50, 36201 Kangasla, Finland Search for other works by this author on: This Site PubMed Google Scholar T. Väisänen T. Väisänen 5Finnish Environmental Institute (SYKE), P.O. BOX 413, 90014 University of Oulu, Finland Search for other works by this author on: This Site PubMed Google Scholar Journal of Water Supply: Research and Technology-Aqua (2013) 62 (3): 183–188. https://doi.org/10.2166/aqua.2013.025 Article history Received: February 21 2012 Accepted: February 18 2013 Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Cite Icon Cite Permissions Search Site Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentAll JournalsThis Journal Search Advanced Search Citation J. Sallanko, J. Hietala, R. Lindström, A. Kytövaara, T. Väisänen; More efficient alkalisation with ground limestone in groundwater treatment. Journal of Water Supply: Research and Technology-Aqua 1 May 2013; 62 (3): 183–188. doi: https://doi.org/10.2166/aqua.2013.025 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex Most Finnish groundwater must be alkalised before use as municipal drinking water because it is corrosive. The corrosiveness is due to low pH and softness of water. Groundwater also often contains aggressive carbon dioxide (CO2), so there is more free CO2 than is required to keep calcium and hydrogen carbonate in solution. The most popular alkalisation method in the past was addition of sodium hydroxide, but use of limestone (calcium carbonate) for alkalisation is becoming increasingly popular, the main reasons being that the overdosing risk is avoided and that water hardness is increased by limestone. The most common method of alkalisation using limestone is through limestone filters, but these are quite large and the empty bed contact time needed often ranges from about 40 minutes to more than 2 h. The investment cost and size of plant required can be substantially reduced by using mechanically ground limestone instead of limestone filters. Incorporation of mechanical grinders into two commercial-scale water treatment plants in Finland greatly reduced the space and treatment time requirements, but some problems were observed by consumers because the harder water increased limescale formation. alkalisation, calcium carbonate, grinding, groundwater treatment, limestone, water treatment This content is only available as a PDF. © IWA Publishing 2013 You do not currently have access to this content.

English

There are number of issues in soft drink industries&rsquo; mode of GAC operation, however, this study focuses on three issues like control of regeneration breakthrough in line with Chlorine and THM breakthrough; its frequency of regeneration and finally the competitive adsorption of different THM on two different types of GAC and extrapolation of result to full scale plant. All the experiments were conducted using rapid small scale column test (RSSCT). And for de-chlorination experiment, deionized water spiked with 2 mg/L chlorine (HOCl) was used. On the other hand, for THM&rsquo;s removal experiment, deionized model water was used with two THM species (chloroform, bromoform or mixture of both components) at a total THM concentration of approximately 80 &micro;g/L. In the experiments, GAC breakthrough curves were established with RSSCT protocol. Therefore, in this study, GAC regeneration is reveled to be controlled by THMs removal. And, RSSCT suggests that in the treatment plant (THMs concentration in feed water of approximately 80 &micro;g/L) Calgon F200 GAC (empty bed contact time (EBCT) = 7.12 min) could treat up to 12000BV before breakthrough of 10 &micro;g/L and this would correspond to 2 months operation. In this study, both Calgon F200 and Norit GCN 1240 also demonstrated in RSSCT experiments that THMs can be effectively reduced below 10 &micro;g/L. However, RSSCT-chloroform adsorption showed slightly higher capacity of Norit GCN 1240 at lower concentration (&lt; 40 &micro;g/L) and slightly higher capacity of Calgon F200 at higher concentration (&gt; 50 &micro;g/L) for Co= 79.8 &plusmn; 4.30 &micro;g chloroform/L and EBCT of 0.31 min. &nbsp; Key words:&nbsp;Granular activated carbon (GAC), rapid small scale column test (RSSCT), bromoform, chloroform, de-chlorination and trihalomethanes (THMs).

Arsenite Removal from Simulated Groundwater by Biogenic Schwertmannite: A Column Trial

To assess the feasibility of biogenic schwertmannite to act as a sorbent for removing arsenite from groundwater, a series of biogenic schwertmannite-packed column adsorption experiments were conducted on simulated As(III)-containing groundwater. Empty bed contact time (EBCT), As(III) concentration in effluent, and the removal efficiency of As(III) through the column were investigated at pH 8.0 and temperature 25 ± 0.5 °C. The results showed that the breakthrough curves were mainly dependent on EBCT values when the influent As(III) concentration was 500 μg L−1 and the optimum EBCT was 4.0 min. When the effluent As(III) concentration reached 10 and 50 μg L−1, the breakthrough volumes for the schwertmannite adsorption column were 4 200 and 5 600 bed volume (BV), with As(III) adsorption capacity of 2.1 and 2.8 mg g−1, respectively. Biogenic schwertmannite could be regenerated by 1.0 mol L−1 NaOH solution, and more than 80% of As(III) adsorbed on the surface of schwertmannite could be released after 3 successive regenerations. The breakthrough volume for the regenerated schwertmannite-packed column still maintained 4 000–4 200 BV when the As(III) concentration in effluent was below 10 μg L−1. Compared with other sorbents for As(III) removal, the biogenic schwertmannite-packed column had a higher breakthrough volume and a much higher adsorption capacity, implying that biogenic schwertmannite was a highly efficient and potential sorbent to purify As(III)-contaminated groundwater.

Study of Seawater Biofiltration by Measuring Adenosine Triphosphate (ATP) and Turbidity

In the present study, we examined seawater biofiltration in terms of adenosine triphosphate (ATP) and turbidity. A pilot biofilter continuously fed with fresh seawater reduced both turbidity and biological activity measured by ATP. Experiments operated with an empty bed contact time (EBCT) of between 2 and 14 min resulted in cellular ATP removals of 32 to 60 % and turbidity removals of 38 to 75 %. Analysis of the water from backwashing the biofilter revealed that the first half of the biofilter concentrated around 80 % of the active biomass and colloidal material that produces turbidity. By reducing the EBCT, the biological activity measured as cellular ATP concentration moved from the first part of the biofilter to the end. Balances of cellular ATP and turbidity between consecutive backwashings indicated that the biological activity generated in the biofilter represented more than 90 % of the detached cellular ATP. In contrast, the effectively trapped ATP was less than 10 % of the overall cellular ATP detached during the backwashing process. Furthermore, the biological activity measured as cellular ATP generated in the biofilter seemed to be more dependent on the elapsed time than the volume filtered. In contrast, the turbidity trapped in the biofilter was proportional to the volume filtered, although a slightly higher amount of turbidity was found in the backwashing water; this was probably due to attrition of the bed medium. Finally, no correlations were found between turbidity and ATP, indicating that the two parameters focus on different matter. This suggests that turbidity should not be used as an alternative to cellular concentration.