GAC Column Research Articles

Comprehensive Solutions to Prevent Larvae Breakout in Water Filtration Systems

The presence of invertebrates in drinking water distribution systems, particularly Chironomidae larvae, has raised concerns among the general public. This study aimed to comprehensively address the issue of larvae breakout in water filtration systems and provide potential solutions to prevent their escape into the water supply. The research investigated various factors contributing to larvae breakout, including the type of filtration column, sand depth, pretreatment methods, and the effective size and uniformity coefficient of sand media. Experimental results revealed that the GAC column, primarily utilized for adsorption, was ineffective in retaining Chironomidae larvae, leading to their escape within a short period. Similarly, the sand filter column, with a design that is currently widely used with sand specifications of an effective size of 0.7 mm and a uniformity coefficient of 1.7, failed to act as a barrier for larvae. Increasing the height of the sand media and applying a pretreatment method, which was expected to prevent larvae from entering the treated water, yielded unsatisfactory results. Our research results show that reducing the uniformity coefficient to 1.5 while maintaining an effective size of 0.7 mm proved to be important in preventing the release of larvae into treated water. The Sand/GAC and Sand/Anthracite systems, by maintaining adjusted media sand specifications, also succeeded in retaining larvae in the filtration system. Additionally, this study emphasized the importance of following the recommended backwash procedure, consisting of specific steps involving air flow, a combination of air and water flow, and final water flow. This sequence effectively removed contaminants, turbidity, and Chironomidae larvae from the filtration media, ensuring improved water quality and system performance. The findings of this study provide valuable insights and recommendations for water treatment plants to address the issue of larvae breakout and enhance water quality.

An analysis of performance of combined aerobic biofilter – granular adsorption – nano adsorption process in seaweed industrial wastewater treatment

Wastewater of Seaweed industry contains macronutrients, alkalis, moderately biodegradable organics, and has a large volume, which it is treated using a biological process (activated sludge) followed by an adsorption process. The results of this treatment are quite effective in reducing the concentration of pollutants to reach the quality standard. However, the reuse of seaweed industrial wastewater into drinking water or process water is still not effective when using a combination of these processes. On the other hand, biological treatment such as aerobic fixed film biofilter (AF2B) and nano adsorption has high effectiveness in reducing biodegradable organic matter (BOD, COD), bacteria, and other metals. Therefore, the reuse of seaweed industrial wastewater into drinking water can be done by combining the two types of processes. The aim of the research was to study the ability of the AF2B – Granular adsorption – nano adsorption process in reducing pollutants in seaweed industrial wastewater. The experiment is conducted by flowing wastewater continuously into a series of process an AF2B reactor, GAC, and CNTs column. By making changes to the factors that affect the performance of each process, and then measuring the pollutant concentration at the input and output of each process, so the performance of each process can be known. Data is analysed to obtain optimum condition in each process that used for design process in wastewater treatment plant. The results showed that of the AF2B/GAC process was able to reduce contaminants such as TSS, BOD, COD, NH3‑N and Chlorine by 98 %, 99 %, 97.3 %, 97.8 %, and 100 % respectively. Furthermore, in the CNTs process, all pollutants not detected until they meet drinking water quality standards

Performance of a granular activated carbon biologically active filter (GAC-BAF) for removing microcystin-LR (MC-LR) from eutrophic water

Abstract Microcystin-LR (MC-LR) removals linked with empty bed contact time (EBCT), temperature and backwash strategies are important for biologically active filter (BAF) application but remain not entirely clear. In addition, there is still a lack of understanding about the bio-regeneration of MC-LR adsorption capacity in a BAF. This study examined MC-LR removals by a granular activated carbon-biologically active filter (GAC-BAF) as a function of EBCT, temperature, and backwash strategies. Results demonstrated that the optimum EBCT (1.2 h for this study) likely depended upon an optimum superficial velocity as well as the GAC column height. A superficial velocity not greater than 0.5 m/h was deemed appropriate according to this research. The MC-LR removals achieved at the optimum EBCT reached 54.8%–72.0%. A higher temperature resulted in a greater MC-LR removal; adsorption might contribute to effective MC-LR removal by the GAC-BAF at a lower temperature. A strategy (Air + air-water + water) was suggested as an optimal backwash strategy for GAC-BAFs in terms of MC-LR removal. A comparison of the effectiveness of the experimental GAC-BAF in continuous and discontinuous operations on MC-LR removals was conducted, from which indirect evidence for bio-regeneration of MC-LR adsorption capacity of the GAC was obtained.

Investigation of enhanced biological dye removal of colored wastewater in a lab-scale biological activated carbon process

In this study, the influence of bacteria and activated carbon adjacent was investigated on treatment and decolorization of synthetic wastewater in a Biological Activated Carbon process. Pseudomonas putida was selected as a bacterial strain capable of degrading aromatic compounds and Acid Blue 92 was used as model azo dye. The optimum conditions for environmental factors affecting decolorization of azo dye was achieved from series of batch experiments. At 25 °C and pH7 the highest efficiency was obtained. At concentration of 20 mg L−1 in batch process, more than 90 % of Acid Blue 92 was reduced in color within just 3 h under optimum conditions. Dual-beam UV–Visible spectrometry and plate assay confirmed biodegradation of the dye by P.putida. The optimum values were then used for continues process. It was found that flow rate and thereby retention time has a critical role in biofilter efficiency. A lab-scale submerged downflow GAC column was sustained by bacterial strain to form the biofilter. About 70 % decolorization was obtained in continuous biological activated carbon process within 2 h with 60 mL h−1 flow rate while adsorption of dye reached the equilibrium and no further dye removal observed. Our results suggest the potential use of P. putida in azo dye decolorization. The combination of activated carbon adsorption and biodegradation by bacterial strains capable of degrading xenobiotic proved to be a promising technique for treatment of dye-contaminated wastewater.

Column filled with Fe-GAC and GAC to remove both As(V) and Fe(III)

First of all, Fe or/and Mn immobilized granular activated carbons (Fe-GAC, Mn-GAC, (Fe, Mn)-GAC) were synthesized and tested to remove arsenate (As(V)). The results in batch test indicated that Fe-GAC removed As(V) effectively, even though the surface area of Fe-GAC was reduced largely. Moreover, adsorption isotherm test indicated that the experimental data fit well with Langmuir model and the maximum adsorption capacity () of Fe-GAC for As(V) was , which was higher than GAC (). In column test, the simulated water, which consisted of As(V), Fe(III), Mn(II) and Ca(II) in tap water, was used. Fe-GAC column with 1 hr of pre-washing time treated As(V) effectively while GAC column removed Fe(III) better than Fe-GAC column. Moreover, the increasing pre-washing time from 1 to 9 hour in Fe-GAC column enhanced Fe(III) removal with little negative impact of As(V) removal. Mostly, the column filled with Fe-GAC and GAC (i.e. the mass ratio of Fe-GAC:GAC

Catalytic Ozonation with Activated Carbon for Treatment of Humic Substances in Water

Ozonation of the ubiquitous and poorly biodegradable humic acid in aquatic system was conducted in the presence of activated carbon with the aim of catalyst. The optimum operating parameters deduced from this study was GAC amount of 16.5 v/v% (GAC column volume per reactor volume) in the humic acid solution of initial pH 9. DOC removal rate in Ozone/GAC process was higher than the sum of Ozone alone and GAC adsorption process. Formaldehyde formation in Ozone/GAC process was less than in Ozone alone and GAC adsorption process. The part of molecular size distribution under 10 k Dalton were increased in the Ozone/GAC process.

오존(O3).입상활성탄(GAC) 공정을 이용한 맛.냄새 유발물질과 유기물질의 제거특성 평가

This study assessed the removal characteristics of taste and odor causing compounds (2-methylisoborneol and geosmin) and organic matters, using a pilot-scale ozone/granular activated carbon (/GAC) process treating surface water of Pal-dang reservoir in the Han river over a 3-month period. Experiments were conducted to verify the removal efficiency of /GAC process which has two different empty bed contact time (EBCT) (/GAC column 1 : 10 min and 2 : 15.1 min) with 10.86 min contact time of ozonation at 1.0 mg/L . Spiking test using geosmin and 2-MIB was also conducted systematically to mimic the conditions when the algae appears, specifically at the levels similar to the concentrations experienced (geosmin: 250 ng/L) in the winter of 2011. In single ozonation process, organic materials, disinfection by-products (DBPs) and their precursors were disassembled but not removed completely. Meanwhile, it was verified that organic matters, taste and odor causing compounds, and DBPs were well removed when sequentially passing through the GAC process. The pilot results also showed that GAC column with larger EBCT achieved higher removal efficiency. Specifically, in spiking tests, single process showed approximately 89% removal efficiency of geosmin and 2-MIB. /GAC combined process demonstrated excellent removal of geosmin and 2-MIB, which are higher than 95%.

한강수계 내 Melamine 농도검출과 GAC처리에서의 파과모델링

한강수계 내 Melamine 농도검출과 GAC처리에서의 파과모델링

Removal of trace organic contaminants by a membrane bioreactor–granular activated carbon (MBR–GAC) system

The removal of trace organics by a membrane bioreactor–granular activated carbon (MBR–GAC) integrated system were investigated. The results confirmed that MBR treatment can be effective for the removal of hydrophobic (logD>3.2) and readily biodegradable trace organics. The data also highlighted the limitation of MBR in removing hydrophilic and persistent compounds (e.g. carbamazepine, diclofenac, and fenoprop) and that GAC could complement MBR very well as a post-treatment process. The MBR–GAC system showed high removal of all selected trace organics including those that are hydrophilic and persistent to biological degradation at up to 406 bed volumes (BV). However, over an extended period, breakthrough of diclofenac was observed after 7320BV. This suggests that strict monitoring should be applied over the lifetime of the GAC column to detect the breakthrough of hydrophilic and persistent compounds which have low removal by MBR treatment.

Removal of organic matters and bacteria by nano-MgO/GAC system

Membrane fouling is a critical problem for efficient commercialization of nanofiltration plants. A nano-MgO/GAC (Granular Activated Carbon) process was investigated the feasibility of using as pre-treatment for nanofiltration. Based on the results obtained, nano-MgO could decrease 51% of Permanganate Index (CODMn), 60% of the ultraviolet absorbance at 254nm (UVA254), and more than 99% of colony counts within 6h. The pH increased to about 10.30 within only 0.5h and then kept stable in the system containing nano-MgO. In addition, adding GAC led to less organic matters (remaining 4.74mg·L−1 versus 6.80mg·L−1) and bacteria (13CFU·mL−1 versus 15CFU·mL−1) relative to using nano-MgO only. Furthermore, almost all nano-MgO could be adsorbed by the GAC column. The pH value of the effluents from the nano-MgO and GAC was 10.18 and 10.20, respectively, while that of the effluent after KH2PO4 adjustment could keep about 7.10.

Bench-scale assessment of pretreatment to reduce fouling of salt-rejecting membranes

A batch, dead-end filtration method is used to compare the effect of various pretreatment operations on membrane performance. The dead-end method is compared with results obtained in cross-flow filtration as well as with conventional SDI measurements. Dead-end experiments were designed to approximate permeate flux over a range of recovery (up to 85%) while cross-flow experiments were operated at a constant recovery of 75%. Fouled membranes were imaged by SEM and, in some cases, EDAX to obtain information on foulant structure and composition. Among the advanced pretreatment processes evaluated, GAC pretreatment, combined with ozone, reduced fouling of both of the membranes tested to the greatest extent. UV irradiation and pre-filtration through a 5 μm membrane did not measurably reduce fouling. The effect of GAC age on fouling was also investigated. GAC columns that had been in service for longer periods of time provided the same benefit in reducing fouling as did GAC columns that had been recently regenerated. This suggests that the primary benefit of GAC pretreatment may be related to biological activity on the GAC filters rather than adsorption of organic matter. Measurements of SDI, TOC values and flux decline suggested a relationship between feed SDI and TOC. However, flux decline was not predicted by SDI values.

Bacterial inoculation of granulaR activated carbon filters for the removal of atrazine from surface water

Pilot scale GAC columns (1 m×140 mm i.d.) were fed ozonated river water containing atrazine at concentrations of 0.5, 10 or 20 μg l −1. Columns were inoculated with an atrazine degrading bacterium Rhodococcus rhodochrous strain SL1. At the start of the experiment, gradual introduction of SL1 into the GAC column over a period of 30 min improved retention of inoculant, compared to rapid (<10 s) injection. Influent and effluent atrazine and atrazine adsorbed to GAC were measured and populations of SL1 and indigenous bacteria associated with the GAC were monitored for 467 d. Inoculation extended “bed life” (i.e. defined as the time before “breakthrough” of atrazine in the effluent consistently exceeded the EU maximum admissible concentration of 100 ng l −1) by a minimum of 41 calendar days or 39 operational days (an increase of 14.5% or 20.5% over non-inoculated columns). A definition which considers the first time breakthrough occurs as significant, gives equivalent figures of 40.2% or 81.7%. The effect of inoculation on reducing effluent atrazine concentration was greatest in the first 232 d of the experiment but was recorded until day 351, by which time an indigenous atrazine degrading population had become established in the non-inoculated columns. SL1 competed well against indigenous bacteria, however periodic reinoculation was required to maintain numbers above the threshold level (>1×10 5 g −1 GAC). Significantly, the pilot plant was subject to a series of disruptions and shutdowns throughout the experiment, but the resilience of the bioregeneration method was demonstrated.

Treatment of taste and odor causing substances in drinking water

To collect fundamental data for the improvement of drinking water quality, focusing on the removal of 2-MIB, Geosmin, IPMP, IBMP and TCA, a total of 20m3/d pilot plant was operated with process schemes of GAC with post-O3(PP-I), and without ozonation(PP-II). Five taste and odor causing substances could be removed to non-detectable concentration with PP-I, but GAC alone was not so effective as PP-I. The larger the EBCT and Iodine Number of GAC column employed, the higher the removal efficiencies expected. The minimum EBCT and Iodine Number were respectively 15 min and 1,000 mg/g of GAC column. Geosmin removal efficiencies ranged 30 to 40% at 15.6 ng/l during conventional process scheme, but 70 to 80% removal was achieved by the PP-I and 60 to 70% by PP-II was achieved. IPMP removal efficiencies were 60 to 80% with GAC only. IBMP and TCA were seldom detected in raw water samples, but TCA was the most difficult to remove of five taste and odor causing substances.

Treatment of taste and odor causing substances in drinking water

To collect fundamental data for the improvement of drinking water quality, focusing on the removal of 2-MIB, Geosmin, IPMP, IBMP and TCA, a total of 20m3/d pilot plant was operated with process schemes of GAC with post-O3(PP-I), and without ozonation(PP-II). Five taste and odor causing substances could be removed to non-detectable concentration with PP-I, but GAC alone was not so effective as PP-I. The larger the EBCT and Iodine Number of GAC column employed, the higher the removal efficiencies expected. The minimum EBCT and Iodine Number were respectively 15 min and 1,000 mg/g of GAC column. Geosmin removal efficiencies ranged 30 to 40% at 15.6 ng/l during conventional process scheme, but 70 to 80% removal was achieved by the PP-I and 60 to 70% by PP-II was achieved. IPMP removal efficiencies were 60 to 80% with GAC only. IBMP and TCA were seldom detected in raw water samples, but TCA was the most difficult to remove of five taste and odor causing substances.

Effect of Ozonation on the biodegradability of atrazine in GAC columns.

The biodegradation of atrazine as influenced by preozonation was studied in biological GAC columns. Metabolism of isopropyl-14C atrazine produced more 14CO2 than ring-UL-14C atrazine, indicating dealkylation was more rapid than ring cleavage. Preozonation increased mineralization of ring-UL-14C atrazine and, consequently, enhanced the performance of GAC columns. Sixty-two percent of the influent atrazine was converted to 14CO2 in columns that received ozonated atrazine and ozonated surface water, while 50% of the influent atrazine was converted to 14CO2 in columns that received untreated atrazine and ozonated surface water, and only 38% of the influent atrazine was converted to 14CO2 in columns with untreated influent.

Inoculation of granular activated carbon with s-triazine-degrading bacteria for water treatment at pilot-scale

Bacterial strains (SL1: Rhodococcus rhodochrous; WT1: Acinetobacter junii) capable of biodegrading atrazine and simazine in surface water were inoculated into pilot-scale fixed beds of granular activated carbon (GAC, 1 m depth, 15 min empty bed contact time, EBCT). River water was screened, clarified, ozonated and spiked with atrazine and simazine (post-ozonation concentration 0.5–15 μg l −1 of each s-triazine) before entering GAC columns that were monitored for 302 d. Elution of inoculated isolates from GAC columns peaked 15 min (WT1) and 30 (SL1) min after inoculation, but had fallen to 3.8 ± 0.13 × 10 3ml −1 (WT1) and 3.6 ± 3.37 × 10 2ml −1 (SL1) by 120 min. During routine operation, elution of SL1 was frequently < 10 ml −1 and less than WT1, and from day 0 to day 119 SL1 was retained on GAC in greater numbers (minimum 8.8 ± 0.32 × 10 4g −1 dry wt GAC) than indigenous WT1 (1.1 ± 0.16 × 10 4g −1 dry wt GAC) or introduced WT1 (9.1 ± 0.00 × 10 3g −1 dry wt GAC). On days 49, 84, 119, 265 and 302 inoculated GAC (SL1 or WT1) had less adsorbed s-triazine per column than non-inoculated GAC. Inoculation of GAC with s-triazine-degrading isolate SL1 reduced transient breakthrough concentrations of atrazine and simazine compared to non-inoculated and WT1-inoculated column effuents on days 21, 84, 140 and 170. However, from day 189 onwards consistent breakthrough occurred in all effluents exceeding the EU maximum admissible concentration (MAC, 0.1 μg l −1).

生物活性炭処理による排水中のＢｏｒｄｅａｕｘ Ｓ染料の処理

Model dye wastewater prepared by adding Bordeaux S (BS) dye was treated by a fixed bed of biological activated carbon (BAC) in comparison to granular activated carbon (GAG) treatment of the wastewater. The total removal efficiency of color and COD in the BAC and GAC column, respectively, was studied. It became clear that the biodegradation rate of BS dye was low because of the low growth rate of Y-1 culture, which was isolated from surface of BAG particles. From the study of BS dye adsorption on Y-1 culture, it was found that the adsorption rate was very high, and adsorption capacity increased greatly when the equilibrium concentration became higher. The adsorption capacity of Y-1 culture which exists on SAC surface can be increased greatly, because the concentration of BS dye on the surface of carbon particles becomes higher due to adsorption. It can be considered therefore, that the adsorption of BS dye on Y-1 culture plays an important roles for removal of BS dye by BAC treatment.

Effects of preozonation on the adsorbability and the biodegradability of aquatic humic substances and on the performance of granular activated carbon filters

Previous work carried out with test organic substances and under sterile and non-sterile conditions of filtration allowed us to show that the microbial degradation of biodegradable compounds increased the GAC adsorption capacities for non-biodegradable solutes (De Laat et al., 1985). This research extends the work to higher molecular weight compounds (isolated aquatic humic and fulvic acids, PHA and PFA) and evaluates the effects of a preozonation treatment on the performances of GAC filters. In the first part of this study, the effect of ozonation on some physical and chemical properties (carboxyl content, adsorbability on GAC, u.v.-absorbance) and on the biodegradability of humic substances were investigated. In the second part, GAC column filtrations were operated under sterile and non-sterile conditions in order to show the influence of preozonation treatment on the performance of GAC columns and to determine the parts due to adsorption and to biodegradation in DOC removal.

Adsorption and Microbiological Mechanisms for Removal of Natural Organics in Granular Activated Carbon Columns

Abstract Performance data for GAC columns treating surface water are analyzed to determine the relative importance of physical adsorption and biological activity, with and without pre-ozonation. Kinetic and equilibrium adsorption parameters for the source water are used in the Homogeneous Surface Diffusion model to predict GAC performance over 83 weeks. The model underestimates removal of TOC for ozonated and unozonated streams by 46% and 28%, respectively, which is attributed to omission of biological removal in the model.

Bioregeneration of activated carbon saturated with phenol

Bioregeneration of granular activated carbon under conditions typical of water treatment plant operation has been demonstrated. An increase in adsorptive capacity, resulting from bacterial removal of material adsorbed on carbon, was shown to occur in bench-scale GAC columns pre-saturated with phenol. Laboratory investigations established the conditions under which bioregeneration took place.