Granular Activated Carbon Bed Research Articles

Machine Learning Models to Predict Early Breakthrough of Recalcitrant Organic Micropollutants in Granular Activated Carbon Adsorbers.

Granular activated carbon (GAC) adsorption is frequently used to remove recalcitrant organic micropollutants (MPs) from water. The overarching aim of this research was to develop machine learning (ML) models to predict GAC performance from adsorbent, adsorbate, and background water matrix properties. For model calibration, MP breakthrough curves were compiled and analyzed to determine the bed volumes of water that can be treated until MP breakthrough reaches ten percent of the influent MP concentration (BV10). Over 400 data points were split into training, validation, and testing sets. Seventeen variables describing MP, background water matrix, and GAC properties were explored in ML models to predict log10-transformed BV10 values. Using the ML models on the testing set, predicted BV10 values exhibited mean absolute errors of ∼0.12 log units and were highly correlated with experimentally determined values (R2 ≥ 0.88). The top three drivers influencing BV10 predictions were the air-hexadecane partition coefficient and hydrogen bond acidity (Abraham parameters L and A) of the MPs and the dissolved organic carbon concentration of the GAC influent water. The model can be used to rapidly estimate the GAC bed life, select effective GAC products for a given treatment scenario, and explore the suitability of GAC treatment for remediating emerging MPs.

Comparing the performance of fluidized and fixed granular activated carbon beds as cathodes for microbial electrosynthesis of carboxylates from CO2

Microbial electrosynthesis (MES) can use renewable electricity to power microbial conversion of carbon dioxide (CO2) into carboxylates. To ensure high productivities in MES, good mass transfer must be ensured, which could be accomplished with fluidization of granular activated carbon (GAC). In this study, fluidized and fixed GAC bed cathodes were compared. Acetate production rate and current density were 42 % and 47 % lower, respectively, in fluidized than fixed bed reactors. Although similar microbial consortium dominated by Eubacterium and Proteiniphilum was observed, lowest biomass quantity was measured with fixed GAC bed indicating higher specific acetate production rates compared to fluidized GAC bed. Furthermore, charge efficiency was the highest and charge recovery in carboxylates the lowest in fixed GAC beds indicating enhanced hydrogen evolution and need for enhancing CO2 feeding to enable higher production rates of acetate. Overall, fixed GAC beds have higher efficiency for acetate production in MES than fluidized GAC beds.

Heat input optimization for the ignition of self-sustained smoldering remediation of contaminated soils using concentrated solar power

In this paper, we explore the industrial-scale feasibility of using concentrated solar power (CSP) as the heat source in the smoldering remediation of petroleum-contaminated soil. Approximately 5 L soil samples were loaded in a narrow-channel reaction chamber and heated from the bottom with CSP to identify the required heat input to achieve ignition. Both petroleum and granular activated carbon (GAC) were used as combustible media. GAC was selected as a cleaner-burning alternative to petroleum and could emulate petroleum-contaminated soil at a mixture of 40 g GAC per kg pool sand on a 1.5 cm bed of GAC. This mixture of GAC showed robust ignition with a minimum power input of 240 W, which was slightly higher than the power input required to ignite industrially generated petroleum-contaminated soil. Preheat temperatures in excess of 300°C were achieved in most experiments, allowing for robust ignition of the smoldering remediation process. CSP was collected using parabolic reflectors 600 mm in diameter and was delivered to the reaction chamber with fiber optic bundles. Each solar concentrator delivered between 50 and 80 W to the reaction chamber, and four concentrators were required to reliably achieve the required power input.

Prevalence of Escherichia coli in electrogenic biofilm on activated carbon in microbial fuel cell.

For a better understanding of the distribution of depth-dependent electrochemically active bacteria at in the anode zone, a customized system in a microbial fuel cell (MFC) packed with granular activated carbon (GAC) was developed and subsequently optimized via electrochemical tests. The constructed MFC system was sequentially operated using two types of matrice solutions: artificially controlled compositions (i.e., artificial wastewater, AW) and solutions obtained directly from actual sewage-treating municipal plants (i.e., municipal wastewater, MW). Notably, significant difference(s) of system efficiencies between AW or MW matrices were observed via performance tests, in that the electricity production capacity under MW matrices is < 25% that of the AW matrices. Interestingly, species of Escherichia coli (E. coli) sampled from the GAC bed (P1: deeper region in GAC bed, P2: shallow region of GAC near electrolytes) exhibited an average relative abundance of 75 to 90% in AW and a relative abundance of approximately 10% in MW, while a lower relative abundance of E. coli was found in both the AW and MW anolyte samples (L). Moreover, similar bacterial communities were identified in samples P1 and P2 for both the AW and MW solutions, indicating a comparable distribution of bacterial communities over the anode area. These results provide new insights into E. coli contribution in power production for the GAC-packed MFC systems (i.e., despite the low contents of Geobacter (> 8%) and Shewanella (> 1%)) for future applications in sustainable energy research. KEY POINTS: • A microbial community analysis for depth-dependence in biofilm was developed. • The system was operated with two matrices; electrochemical performance was assessed. • E. coli spp. was distinctly found in anode zone layers composed of activated carbon.

Column-based removal of high concentration microplastics in synthetic wastewater using granular activated carbon

ABSTRACTMicroplastic (MP) is an emerging contaminant of concern due to its abundance in the environment. Wastewater treatment plant (WWTP) can be considered as one of the main sources of microplastics in freshwater due to its inefficiency in the complete removal of small MPs. In this study, a column-based MP removal which could serve as a tertiary treatment in WWTPs is evaluated using granular activated carbon (GAC) as adsorbent/filter media, eliminating clogging problems commonly caused by powder form activated carbon (PAC). The GAC is characterized via N2 adsorption–desorption isotherm, field emission scanning electron microscopy, and contact angle measurement to determine the influence of its properties on MP removal efficiency. MPs (40–48 μm) removal up to 95.5% was observed with 0.2 g/L MP, which is the lowest concentration tested in this work, but still higher than commonly used MP concentration in other studies. The performance is reduced with further increase in MP concentration (up to 1.0 g/L), but increasing the GAC bed length from 7.5 to 17.5 cm could lead to better removal efficiencies. MP particles are immobilized by the GAC predominantly by filtration process by being entangled with small GAC particles/chips or stuck between the GAC particles. MPs are insignificantly removed by adsorption process through entrapment in GAC porous structure or attachment onto the GAC surface.

Removal of the waterborne parasite Cryptosporidium parvum from drinking water using granular activated carbon

Cryptosporidium is a genus of apicomplexan parasites that infect the gastrointestinal tract of a wide range of vertebrate hosts, including humans. These enteropathogens are commonly detected in surface waters and Cryptosporidium is responsible of numerous waterborne outbreaks in industrialised countries. Filters of granular activated carbon (GAC) are mainly used to eliminate emerging micropollutants or control unpleasant odour and taste in drinking water. Recently, GAC has been also employed for removal of microorganisms from different types of water. This work evaluates the capability of GAC in the elimination of the infective forms of Cryptosporidium parvum (oocysts) from drinking water. For this, well water was spiked with oocysts of C. parvum and passed through a chromatographic column filled with fresh GAC at different bed heights (5–50 cm) and a filtration rate of 100 mL/min, approximately. By immunofluorescence microscopy, the number of oocysts in the water samples was determined. The logarithmic reduction (LR) was calculated by comparing the number of oocysts quantified in the filtered samples and the corresponding influent samples. High efficiencies of GAC in removing C. parvum oocysts from water were obtained. Thus, with a bed height of 35 cm, removal efficiencies > 2 LR were achieved. The highest LR (3.47 ± 0.31) was observed when a GAC bed height of 50 cm was used. Taking into account the results obtained, C. parvum oocysts were eliminated remarkably and, therefore, GAC adsorption filters may be considered additional barriers against this waterborne enteropathogen in drinking water at the household level in developing countries.

Pilot-scale removal of persistent and mobile organic substances in granular activated carbon filters and experimental predictability at lab-scale

Present knowledge about the fate of persistent and mobile (PM) substances in drinking water treatment is limited. Hence, this study assesses the potential of fixed-bed granular activated carbon (GAC) filters to fill the treatment gap for PM substances and the elimination predictability from lab-scale experiments. Two parallel pilot filters (GAC bed height 2 m, diameter 15 cm) with different GAC were operated for 1.5 years (ca. 47,000 BV throughput) alongside rapid small-scale column tests (RSSCT) designed based on the proportional diffusivity (PD) and the constant diffusivity (CD) approaches. Background dissolved organic matter (DOM) and a set of 17 target substances were investigated, among them 2-acrylamido-2-methylpropane sulfonate (AAMPS), adamantan-1-amine (ATA), melamine (MEL) and trifluoromethanesulfonic acid (TFMSA). Nine substances were predominantly present in the drinking water used as pilot filter influent (frequencies of detection above 80 %, median concentrations 0.003–1.868 μg/L) and their breakthrough behaviors could be observed: TFMSA was not retained at all, four substances including AAMPS and ATA reached complete breakthrough below 20,000 BV, three compounds were partially retained until the end of operation and oxypurinol was retained completely. The comparable PM candidate and DOM removal performances of both GAC aligns with their very similar surface characteristics and elemental compositions. The agreement of results between RSSCT with the pilot-scale filters were substance specific and no superior RSSCT design could be identified. However, CD-RSSCT provide a conservative removal prediction for most studied compounds. MEL adsorption was significantly underestimated by both RSSCT designs. Using the criterion of a carbon usage rate (with respect to 50 % breakthrough) below 25 mgGAC/Lwater for an economic retention by fixed-bed GAC filters, five (out of nine) substances met the requirement.

녹조오염 호소수의 수질특성과 흡착여과공정에 미치는 영향

The objectives of this study were to characterize an algae polluted-lake water using conventional variables of Trophic State Index Korea (TSIko) and to evaluate the performances of granular activated carbon (GAC) adsorption and the filtration of membrane filter (MF) using stirred dead end filtration cell on pollutants removal (COD, T-N, T-P, chlorophyll-a (chl-a), secchi disc (SD), and dissolved organic matter(DOC)) in the algae-polluted-lake water. As a result, regression analyses of log transformed seasonal Chl-a against T-P and T-N showed that variation of the Chl-a was explained by the variation of T-P(r= 0.3887) but not by T-N(r=0.2721). Consequently, The data obtained from this study suggest that one of the ways controlling the eutrophication would be a reduction of phosphorus from the watershed. Applied filtration rates during this experiment were <4.0 m/h for GAC bed and 0.5 m³/m².d for MF. Both GAC bed and GAC/MF system achieved more than 40% efficiency in removing geosmin and 2-methylisoborneol(2-MIB). The combined membrane process with GAC adsorption process was found to produce the highest quality finished water and could be proposed as one of the best available processes for removing geosmin. The increase of influent algae and DOC increased transmembrane pressure (TMP) of MF process. Membrane resistance of MF process coupled with GAC bed was lower than that MF process.

Treatment of Dye Waste Water using Moving Bed Biofilm Reactor and Granular Activated Carbon with Neem Leaf Powder

In recent days, the waste productions from industries are increased and direct discharge of wastes causes various pollution to the environment. Wastewater treatment in textile and dye industry mainly involves treatment of highly colored wastewater containing variety of dyes in different concentrations. The dyeing industries using different types of pigments and dyes of various concentration during their several production steps. These industries discharge a wastewater which contains organic substance, high colour with high COD and low concentration of BOD. This dye waste water are directly discharge in to the streams and thus contaminate the groundwater. To treat the wastewater, which is discharge from the dyeing industries a simple physio-chemical treatment is not sufficient for the removal of pollutants. So that a biological treatment followed with a physio-chemical treatment have been required. In this study, the experiment was carried out to reduce the organic substance, high colour, COD, BOD, and Heavy metals from dye wastewater using the laboratory scale Moving Bed Biofilm Reactor followed with Granular activated Carbon bed (GAC with NLP-MBBR) with Neem leaf powder. A various thick granular activated carbon bed was used for adsorption technique and for biological treatment of wastewater. The GAC with 8cm thick is layered followed by Ennore sand with 3 grades with 4cm thick equally. Then the MBBR was operated continuously with various retention times. The polypropylene type bio balls were used for microorganism attachment in MBBR. The outlet water from the MBBR are treated using membrane process. Membrane process using moving membranes reduces the pH, organic contents, heavy metals, COD, BOD, turbidity etc., The final effluent water is suitable for Irrigation.

Fluidisation characteristics of granular activated carbon in drinking water treatment applications

Granular activated carbon (GAC) filtration is an important unit operation in drinking water treatment. GAC filtration is widely used for its filtration and adsorption capabilities as a barrier for undesired organic macro- and micro-pollutants. GAC filtration consists of two successive phases: adsorption and filtration, capturing the impurities from the water in conjunction with a backwash procedure in which the suspended particles are flushed out of the system. Available literature predominantly focusses on adsorption. A less frequently discussed but nevertheless equally crucial aspect of this operation is the backwash procedure of GAC beds. To prevent accumulation of suspended particles and to avoid additional operation costs, optimal backwashing is required. Another factor is sustainability: water utilities are showing increasing interest in exploring new sustainable GAC media. As these have different bed expansion tendencies due to different GAC characteristics with varying geometries, operational developments are needed for prediction models to estimate the expansion degree during backwashing. The prediction of the bed expansion of GAC is complex as the particles are non-spherical, porous and polydisperse. Through a combination of advanced particle laboratory and fluidisation experiments, we demonstrate a new approach which leads to an improved expansion prediction model for the backwashing of GAC filters.

Experimental estimation of axial–vertical flow permeability through a packed bed of granular activated carbon

Flow through packed beds of granular materials, and for instance, granular activated carbon (GAC), is of great importance and has various applications in desalination, refinery, filtration, separation, and so forth. Hence, transport analysis and flow characterization of such problems have to be supported by experimental data. In the present study, flow transport through a packed bed of GAC, as an adsorbent material, is analyzed experimentally. The focus of the work is on the axial–vertical flow of air and argon through five different GAC grain samples to characterize the flow behavior in terms of GAC grain size. In addition, some other affecting parameters, including the fluid inlet pressure and the flow rate, are studied and their effects on the permeability of the porous bed as well as fluid pressure drop are presented. To study the effects of the gravity on friction factor and pressure drop, all tests are performed in two situations—fluid flow with the same and the opposite direction as the gravitational acceleration. It is found that gravity can increase the pressure drop about 10 to 400 Pa (about 10 to 25% higher) which is significant. Also, the pressure drops through the packed bed of GAC are found and the results are reported in terms of non-dimensional parameters of friction factor versus Reynolds number, to propose proper correlations for various fluids flowing in different directions through the applied GAC grains. Correlations, which are reported in this article, can be used in designing systems in which pressure drop is of great importance, and activated carbon in the vertical situation is utilized.

Effect of sequencing batch reactor (SBR)/granular activated carbon (GAC) bed and membrane hybrid system for simultaneous water reuse and membrane fouling mitigation

The objectives of this study are to assess the potential of an activated and granular sludge (AS and GS) sequencing batch reactor (SBR)/granular activated carbon (GAC) coupled with a membrane for achieving reclamation and reuse of real mixed wastewater and to evaluate the feasibility of the configured systems for achieving membrane fouling mitigation. A better performance of membrane filtration (MF) having lower membrane fouling was observed at both higher agitation velocity and lower permeate flux. Despite a twice shorter hydraulic retention time (HRT) than that of the AS-SBR/MF configured system, the performances of the GS-SBR/MF system without and with a GAC bed as a pretreatment for the MF process achieved higher efficiencies than those of the AS-SBR system for organics and nutrient removal and higher flux in the MF. The addition of a GAC filter after SBR processes was more effective in mitigating membrane fouling due to effective foulant removal. These results indicate that the GS-SBR as an alternative process for the AS-SBR or the addition of a GAC bed after the SBR process is needed to obtain the reusable water with good quality and to improve the fouling rate and filtration time of the MF process.

Treatment of Gaseous Ammonia Emissions Using Date Palm Pits Based Granular Activated Carbon.

The present work investigated the application of granular activated carbon (GAC) derived from date palm pits (DPP) agricultural waste for treating gaseous ammonia. Respective findings indicate increased breakthrough time (run time at which 5% of influent ammonia is exiting with the effluent gas) with a decrease in influent ammonia and increase in GAC bed depth. At a gas flow rate of 1.1 L/min and GAC column length of 8 cm, the following breakthrough trend was noted: 1295 min (2.5 ppmv) > 712 min (5 ppmv) > 532 min (7.5 ppmv). A qualitatively similar trend was also noted for the exhaustion time results (run time at which 95% of influent ammonia is exiting with the effluent gas). The Fourier Transform Infrared Spectroscopy (FTIR) findings for the produced GAC indicated some salient functional groups at the produced GAC surface including O–H, C–H, C–O, and S=O groups. Ammonia adsorption was suggested to result from its interaction with the respective surface functional groups via different mechanisms. Comparison with a commercial GAC showed the date palm pits based GAC to be having slightly higher breakthrough and exhaustion capacity.

Minicolumn Test of Remaining GAC Performance for Taste and Odor Removal: Theoretical Analysis

AbstractIn drinking water treatment, it is difficult to predict the remaining service life of a partially spent granular activated carbon bed when contaminants are intermittent, such as taste and o...

IMPROVEMENT OF METHANE STORAGE CAPACITY IN ACTIVATED CARBON BED WITH BIDISPERSE PACKING

Abstract This study presents a numerical investigation of the dynamics of methane adsorption in granular activated carbon beds with bidisperse packing in order to reduce the void spaces between the adsorbent particles and to improve the storage capacity in adsorbed natural gas vessels. Two distinct particle sizes (d and D) were used for the packing of the bidisperse bed, and the following particle size ratios were investigated: δ = d/D = 1 (monodisperse bed), 1/5, 1/10, 1/15, and 1/20. Compared with the monodisperse bed condition, the results obtained showed that bidisperse packing increases bed density by about 30% and methane storage capacity by up to 20%. The results also showed that the charging time could be optimized by increasing the pressure drop applied to the bed and that the storage capacity can be increased by cooling the admitted gas in the vessel.

Combined microfiltration and adsorption process applied to public water supply treatment: water quality influence on pesticides removal

ABSTRACT Granular activated carbon (GAC) fixed bed adsorption technology was applied to remove carbamates carbaryl, methomyl and carbofuran from public water supply. In order to minimize the effect of clogging and to evaluate adsorbent saturation for carbamates, the microfiltration (MF) was previously used to adsorb and the backwash procedure of the GAC bed was carried out. The determination and quantification of the carbamates were performed by analytical technique in high performance liquid chromatography with post-column derivatization and fluorescence detector. The MF of the water previously adsorbed in the GAC fixed bed allowed the greater removal of 100% of the carbamates pesticides with an initial concentration of 25 μg L−1 during the first 48 h of operation. The saturation of the GAC fixed bed occurred in 240 h, due to the partial removal of the natural organic matter by the MF, consequently the competition for adsorptive sites of the GAC was smaller. The backwashing procedure contributed to the partial recovery of the performance of the hydraulic filtration and allowed to identify the saturation of the adsorption column, since the sealing phenomenon preceded the saturation. Finally, the use of public water supply was considered a relevant and positive aspect, since it allowed the identification of the performance of this technology in the removal of carbamates pesticides considering the presence of substances inherent to the public water supply.

Water extractable organic matter (WEOM) as an indicator of granular activated carbon (GAC) bed life and water quality outcomes in drinking water treatment

Simple extraction and quantification of adsorbed organic carbon can effectively assess granular activated carbon bed file.

Experimental investigation of effects of grain size, inlet pressure and flow rate of air and argon on pressure drop through a packed bed of granular activated carbon

Considering the wide range of applications of the activated carbon in different applications, the behavior of fluid flow through a packed bed of irregular shaped activated carbon grains has significant importance. Hence, an experimental investigation is conducted on axial-horizontal flow of air and argon through 5 different packed beds of granular activated carbon (GAC) with different grain sizes. Investigations are done different flow line pressure and flow rates. Based on the previous studies, a simple correlation is proposed and results are presented in terms of dimensionless friction factor versus Reynolds number. Results are presented for different grain sizes and the correlation coefficients have been estimated with excellent curve fitting to the experimental data. Outcomes of this study could be used to design the systems in which the pressure drop through a packed bed of GAC is required.

Vertical distribution pattern of naidids in granular activated carbon filters and potential technology to control their penetration risk

Abstract Aquatic worms propagated in granular activated carbon (GAC) filter has become a troublesome problem for drinking water supply. This study investigated the vertical distribution patterns of naidids in GAC filter beds and assessed the effect of an additional sand bed, located below the GAC bed, in preventing naidids from being present in effluent. The results indicated that the vertical distribution data of naidids in the GAC filter bed were well fitted by a Gaussian distribution, and the location of peak population density was mainly affected by downward flow. Backwashing experiments revealed that additional pressure air scouring shifted the distribution pattern of naidids in the GAC filter bed, resulting in a significant enhancement in naidid removal efficiency. Additionally, the addition of a sand bed exhibited pronounced interception and inactivation effects on naidids, suggesting that it may be a very promising technology for preventing naidids propagated in GAC filters from being present in the effluent.

Treatment of mature landfill leachate using hybrid processes of hydrogen peroxide and adsorption in an activated carbon fixed bed column

ABSTRACTIn this study, the treatment of mature landfill leachate is evaluated by oxidation with hydrogen peroxide (H2O2) combined with adsorption in a granular activated carbon (GAC) fixed bed column to determinate the increase in the biodegradability index, the reduction of chemical oxygen demand (COD) as well as the increase in the useful life of the GAC bed. The sample leachate from Loma de Los Cocos Landfill (Cartagena de Indias, Colombia) has a very low biodegradability ratio ranging from 0.034 to 0.048 that makes it difficult to meet the required water quality level according to the regulations. The COD removal is initially monitored in the H2O2 oxidation treatment process. The operating conditions such as pH, H2O2 dosage, and the reaction time are optimized in this process based on the percentage of COD removal. A maximum COD removal of 29.9% is achieved at an initial H2O2 concentration of 5000 mg L−1 with a pH of 8 and the reaction time of 60 min. The hybrid treatment by H2O2-GAC achieved 97.3% COD removal and 116% increase in the biodegradability ratio (from 0.072 to 0.134) while this ratio was increased by 6.5% with H2O2 alone. Moreover, the useful life of the GAC bed is increased from 45 min in the column fed with raw leachate to 170 min in the column fed with pretreated leachate and 5000 mg L−1 of H2O2 at pH of 8 that subsequently increased the activated carbon adsorption capacity. An adsorption model for leachate treated with H2O2 is also developed.