GAC Filtration Research Articles

Mastering granular activated carbon filtration to remove organic micropollutants, antibiotic resistance and metals for municipal wastewater reuse

GAC filtration of municipal wastewater was optimized and intensified, making its implementation and operation directly after secondary clarification possible and relevant. GAC was first selected based on laboratory tests. Performances on organic micropollutants were linked to the repartition of BET surface between micropores and meso/macropores. At pilot scale, in order to limit the impact of head loss, downflow declogging sequences (DCS) were implemented and upflow filtration tested. 6 to 12 DCS per day led to a 4.7–5.5-fold increase of particles retention capacity between backwashes (cycle duration of 20–120 h), and upflow operations improved head loss evolution profile with only a slight GAC (<15 %) expansion. DCS allows backwash frequency reduction, enabling significant water savings. Both adaptations maintained high organic micropollutants removals compared to a review of 16 GAC studies at pilot or full-scale, results being in the upper range. A specific dose of 2.0–2.5 g GAC/gC was necessary to obtain an average removal of pharmaceuticals and benzotriazole of 80 % at 20 min contact time, which is comparable to PAC and low granulometry GAC. Higher doses are needed for PFAS but >80 % removals are achievable. Particles, TKN, particulate phosphorus and organic matter are well removed by GAC filtration in both configurations. Biological activity is observed through nitrogen transformation in the GAC bed. Heavy metals are greatly removed in GAC filtration, in particular Cd, Cu, Ni and Pb, probably through biosorption onto the biofilm, developed within the GAC bed. For wastewater reuse applications, GAC filtration has an added value through physicochemical quality improvement and fecal contamination indicators removal of 1 log, facilitating the implementation and optimizing the design of a post-disinfection. Antibiotic resistant bacteria and antibiotic resistance genes are also partially retained in GAC filtration. Finally, biological wastewater treatments combined to GAC filtration is a good solution to effectively treat organic micropollutants together with heavy metals and preparing post-disinfection for reuse.

Assessment of full-scale 4th treatment step for micro pollutant removal in Sweden: Sand and GAC filter combo

This study focuses on the 4th treatment step in Degeberga WWTP treatment plant, the first full scale GAC filter in Sweden installed in April 2020 for removal of micropollutants. The two GAC filters, containing two different carbon types, has operated flawlessly for three years (30,000 bed volumes) without requiring backwashing. The results indicate that the sand filter provides effective protection to the carbon filters, preventing solids from reaching the carbon and reducing the growth of organic matter. Additionally substantial biodegradation was observed for several substances.During the first year of operation, the two filters (at 8500 and 5700 bed volumes respectively) achieved >98 % removal of 24 substances. By the end of the second year (at 19,000 and 12,600 bed volumes respectively), fluconazole and sulfamethoxazole broke through completely, and the number of compounds below 80 % removal increased. The average removal of micro pollutants decreased over time. Compounds with positive charges generally exhibited higher adsorption capacities, while negatively charged compounds had lower removals. On average the investigated 24 compounds was removed by 89 % in the 4th treatment step over three years. The study suggests that biodegradation may contribute to the removal of some micropollutants in GAC filters, similar to observations made in the sand filter.Both Swiss and suggested EU regulations aim for at least an 80 % removal in micropollutant concentration. The study evaluated the performance of the filters based on this guideline and the presented technique is after a total of eight years of investigation and evaluation a proven performer.Overall, the 4th treatment combination of sand and GAC filters in WWTPs has shown promising results in removing organic micropollutants, addressing the need for efficient treatment strategies targeting these emerging pollutants. Degeberga WWTP serves as an example of successful implementation of advanced treatment for improving water quality and protecting human and aquatic health.

Long-term removal of perfluoroalkyl substances via activated carbon process for general advanced treatment purposes

Granular or powdered activated carbon (GAC/PAC) processes are installed in full-scale drinking water treatment plants (DWTPs) to reduce disinfection byproduct precursors, odor, ammonia, and pesticides. This study investigated the ability of GAC/PAC processes in 23 DWTPs to remove per- and polyfluoroalkyl substances (PFASs). In the GAC process, filter breakthrough of perfluoroalkyl carboxylic acids (PFCAs) occurred faster as the PFCA chain length is decreased. During periods of high water temperatures (20−29 °C), the effluent concentration of two short-chain PFCAs (C4 and C5) surpassed that of the influent after the throughput reached 5,000−7,500 bed volumes (equivalent to 2−3 months) due to desorption. However, such desorption was not observed during periods of low water temperatures (5−19 °C). Meanwhile, long-chain PFCAs were consistently removed, as the GAC was replaced before breakthrough became noticeable. PFAS removal deteriorated at a remarkably fast rate after a partial breakthrough of several tens of percent. Biological activated carbon was proved ineffective in removing PFASs due to its diminished adsorption capacity after long-term use. The PAC process, however, exhibited a slight decrease in PFCA residual (10%) at higher water temperatures (15−30 °C). The PAC dose required for a certain residual ratio was lower with an increase in the hydrophobicity of PFAS; C8-PFCA only required 20 mg/L of PAC for 50% removal, while C4-PFCA required a significantly higher dose of 100−700 mg/L. Consequently, the activated carbon process, which removes organic contaminants in surface water, was inadequate in removing PFASs, particularly those with short chains. Thus, it is recommended that GAC filters be replaced more frequently (within two months) for short-chain PFAS removal. Further, the adsorption performance of PAC must be enhanced.

Treatment of laundry wastewater by different processes: Optimization and life cycle assessment

Wastewater from industrial laundries is often difficult to treat because it usually presents high turbidity and chemical oxygen demand (COD). We studied several processes for the treatment of laundry wastewater which was provided by a hotel in the south of Gran Canaria, Spain. More specifically, we studied coagulation with iron (III) sulphate, Fenton, photo-Fenton and a biological treatment (using a biofilter, and a granular activated carbon, GAC, filtration). The coagulation and Fenton processes produced large amounts of sludge and could not meet the required standards for water reuse in Spain. The use of photo-Fenton and the BF resulted in complete turbidity removal and high COD removal. However, we found that the effluent from the BF did not meet the COD removal criteria for water reuse, and thus a GAC filtration post-treatment was employed to reduce COD to acceptable levels. The photo-Fenton process alone did meet the criteria for water reuse. The estimated cost to treat 1 m3 of wastewater was 6.72 € for photo-Fenton and 0.71 € for BF + GAC. The cost and life cycle assessment analyses that were also performed revealed that the acquisition of the necessary reagents is the main contribution to the overall economic and environmental costs for both options, and that the BF + GAC option is notably cheaper. Additionally, this option also causes much lower environmental impacts than photo-Fenton.

Iron removal from groundwater using granular activated carbon filters by oxidation coupled with the adsorption process

Abstract Granular activated carbon (GAC) is commonly used as an adsorbent for the removal of organic micropollutants. However, little is known about the inorganic pollutant removal using GAC. In this study, GAC was examined for the removal of iron from synthetic groundwater (SGW) using oxidation coupled with an adsorption mechanism. Batch experiments including kinetic and isotherm studies were carried out to find out the adsorption capacity of GAC. A column test was conducted at different phases to identify the influence of the initial concentration of iron, hydraulic retention time (HRT), and air supply to the system. It was observed that the experimental results for the kinetic experiment best fit the pseudo-first-order kinetics model with 88% maximum removal efficiency achieved in 240 min. A reduction in adsorption capacity was observed with the concomitant increase in the weight of GAC, whereas the maximum adsorption capacity of GAC was found to be 0.17mg Fe/g GAC. Column experiments confirmed that the effluent iron concentration reduced from 0.05 to 0.03mg/L when the iron concentration in the influent increased from 1 to 3mg/L. The reduction in HRT from 7 to 3.5h did not significantly affect the iron removal efficiency. The air supply to the system with the flow rate of 3.5L/min did not show any improvement in the iron removal efficiency due to the increased airflow rate. In all cases, the iron level in the effluent satisfied the drinking water quality standard recommended by the World Health Organization (WHO) which affirms that GAC filters are more suitable for iron removal from groundwater.

Biological and physico-chemical mechanisms accelerating the acclimation of Mn-removing biofilters

This study investigated treatment strategies which accelerated the acclimation of new Mn-removing biofilters to help utilities respond to changing Mn regulations, such as the recent introduction of a health-based maximum acceptable concentration and a reduction in the aesthetic objective for Mn in drinking water by Health Canada. Bench-scale filters of either GAC or anthracite media were fed with applied water containing Mn (17–61 μg/L) from a full-scale plant over 294 days. Treatment strategies included the addition of H2O2 (1 mg/L) and/or an increase in pH from 6.8 to 7.5 through the addition of NaOH. The potential physico-chemical and biological mechanisms responsible for accelerated biofilter acclimation under the various redox conditions were investigated through thermodynamic modelling, to predict homogeneous Mn oxide formation, and 16S rRNA gene amplicon sequencing, to characterize the microbial community within the filters. GAC filters treated with NaOH, and both H2O2 and NaOH, were the first to acclimate (< 20 μg/L Mn in filter effluent) after 59 and 63 days respectively, while the ambient GAC filter took almost 3 times as long to acclimate (168 days), and the anthracite filters which received the same chemically adjusted water took almost 4 times as long (226 and 251 days, respectively). The accelerated acclimation in the treated GAC filters was likely due to physico-chemical oxidation via three potential mechanisms: (1) homogeneous oxidation of dissolved Mn(II) to Mn(III)/Mn(IV) oxides and the subsequent removal of oxides from solution through adherence to the GAC surface, (2) adsorption of dissolved Mn(II) to GAC and subsequent homogeneous or biological oxidation, or (3) formation of colloidal Mn(III)/Mn(IV) oxides and subsequent adsorption of dissolved Mn(II) to the Mn colloids. In the untreated GAC filter and all anthracite filters, which did not benefit from improved redox conditions or an active surface, physico-chemical mechanisms alone were insufficient for consistent Mn removal to less than 20 μg/L. Acclimation in these filters was delayed until a microbiome enriched with bacteria capable of biological nitrification and Mn oxidation evolved within the filters. The acclimated microbiome was consistent between GAC and anthracite filters and was significantly different from the non-acclimated microbiome (p < 0.001) initially formed during the early operation of the filters. Interestingly, treatment with NaOH, and NaOH and H2O2, which accelerated physico-chemical oxidation in GAC filters, was observed to delay the development of biological oxidation in anthracite filters, and thus deferred acclimation. Although some filters took longer to acclimate than others, once acclimation was reached all filters had a similar microbiome and were able to consistently remove Mn to below 20 µg/L.

Adapting the low-cost pre-disinfection column PREDICO for simultaneous softening and disinfection of pore water

In previous works, a low-cost predisinfection column that combined coagulation-flocculation and GAC filtration was proposed for combination with electrodisinfection in the successful treatment of highly faecal polluted surface water. In this work, this column is adapted for the treatment of pore water by transforming the coagulation chamber into a chemical reactor with lime and replacing the GAC of the filter with ion exchange resins. This adapted system can soften water, remove nitrate and condition water for very efficient electrochemical disinfection, where 4 logs and 3 logs in the removal of E. coli and P. aeruginosa, respectively, were reached using commercial electrochemical cells, i.e., CabECO ® or MIKROZON®. The availability and low cost of the technology are strong points for usage in poor areas of developing countries.

Physio-Chemical And Statistical Analysis Of Ground Water Quality In Northern Part Of Karur District-Review

Karur district is located in banks of amaravathi and kaveri rivers ,it is well known for its handloom textiles ,blanket exports,dyeing industries and netting industries.The ground water resources are well polluted due to the untreated effluent discharges of above mentioned industries.We have analysed the physio-chemical parameters of samples from 25 various locations in January and February month at northern part of karur district.(i.e.,pH,Turbidity,Electrical Conductivity,TDS,Hardness,etc.,) and interpulated the results with statistical approach,correlation and WQI.While interpolating the results with WQI we found that 12% of samples has a very poor status(75.7068) and 4% is unfit for drinking(157.124). 98% of samples is beyond 500mg/l while calculating TDS(highest range 5800mg/l at Noyyal.EC,pH are within the permissible limits.We can observe a drastical hike of results exceeding the permissible limit of Indian standards,WHO limits.We found a peak value of chlorides(2813mg/l)while testing Noyyal sample.Correlation gives positive value while correlating alkalinity with other parameters,this shows a direct proportionality of alkalinity with other parameters.For controlling these pollution and improving the ground water quality we must ensure of not mixing oils,cleaning chemicals,untreated effluents from industries into ground water.Air sparging and stripping,GAC filters,RO methods can be used for treating contaminated ground water.

Demonstrating the reduction of enteric viruses by drinking water treatment during snowmelt episodes in urban areas

This study investigates short-term fluctuations in virus concentrations in source water and their removal by full-scale drinking water treatment processes under different source water conditions. Transient peaks in raw water faecal contamination were identified using in situ online β-d-glucuronidase activity monitoring at two urban drinking water treatment plants. During these peaks, sequential grab samples were collected at the source and throughout the treatment train to evaluate concentrations of rotavirus, adenovirus, norovirus, enterovirus, JC virus, reovirus, astrovirus and sapovirus by reverse transcription and real-time quantitative PCR. Virus infectivity was assessed through viral culture by measurement of cytopathic effect and integrated cell culture qPCR. Virus concentrations increased by approximately 0.5-log during two snowmelt/rainfall episodes and approximately 1.0-log following a planned wastewater discharge upstream of the drinking water intake and during a β-d-glucuronidase activity peak in dry weather conditions. Increases in the removal of adenovirus and rotavirus by coagulation/flocculation processes were observed during peak virus concentrations in source water, suggesting that these processes do not operate under steady-state conditions but dynamic conditions in response to source water conditions. Rotavirus and enterovirus detected in raw and treated water samples were predominantly negative in viral culture. At one site, infectious adenoviruses were detected in raw water and water treated by a combination of ballasted clarification, ozonation, GAC filtration, and UV disinfection operated at a dose of 40 mJ cm−2. The proposed sampling strategy can inform the understanding of the dynamics associated with virus concentrations at drinking water treatment plants susceptible to de facto wastewater reuse.

Microbial Risks in Household GAC Filters Increased with Residence Time

The research studied microbial contamination in household GAC filters with residence time. Initial GAC effluents were collected and stored in different circumstances (glass cup, silver cup and new GAC), Bacterial growth in GAC effluents and stored samples were detected during the 3-day residence time simultaneously. Besides, microbiome diversities in the GAC unit were measured for one month. Three main conclusions were found: (1) the maximum microbial counts were higher in storage water than in GAC filters. (2) The growth rates were faster in filters than those in storage water in a shorter residence time and the microbial risks were apparent initially. (3) The pH level decreased with residence time and the oxidation properties increased due to the desorption of GAC. The research provided useful information for optimizing household purifiers usage.

Biological ion exchange as an alternative to biological activated carbon for drinking water treatment

Biological ion exchange (BIEX) has proved to remove natural organic matter (NOM) better than biological activated carbon (BAC). This raises the question if BIEX can be integrated into a full-scale drinking water treatment plant to remove NOM and ammonia. In this study, a pilot plant consisting of one BIEX filter, three GAC filters and one BAC filter was set up as second-stage filtration at the Sainte-Rose drinking water treatment plant (Laval, Canada). The pilot plant was operated for a period of nine months without regeneration of the ion exchange resins. The influent water showed low DOC (2.5 mg/L) and high sulfate concentrations (28.2 mg/L). Except of a short peak of DOC released at about 1 000 BV, the BIEX filter achieved a nearly constant removal of 29–36% over the whole study period. The DOC removals of GAC were similar to BIEX at < 8000 BV but then stabilized at 13–24% after 8 000 BV. Most DOC removal in the BIEX filter was achieved at the top 30 cm layer (81%) compared to 62–66% removal in the GAC/BAC filters in the same layer. After the rapid exhaustion of the primary ion exchange capacity (<1 000 BV), sulfate displaced the fraction of NOM with lower affinity than sulfate, corresponding to the initial DOC release in the BIEX filter. The fraction of NOM with higher affinity than sulfate can still replace sulfate, which explains the good long-term performance of the BIEX filter. BIEX released ammonia with an average of 15% in warm water condition, probably related to the small diameter of the column which limited backwash effectiveness.

Drinking water quality and its resources with three different technologies

Surface water and ground water are the basic resources of drinking water insuburban area. Three kinds of waters and were monitored to differentiate its suitability for drinking waters through different technologies used to treat. For three waters characterized results, biological indicators were moderate loads. While, chemical analyses were recorded different water quality indices (WQI). All of the collected samples showed significant improvements in total solids. The only sample that showed slight increases in total solids was the raw water from the surface compared to the other two groundwater resources. In case of system operating with only chlorination for groundwater, increased dosing loads resulted in a bad taste that required GAC filtration units after. In a GAC/RO system operating in water conditions (<500 TDS), reducing the treatment efficiency loading rate to 45% from 60-80% was important for achieving effluent quality more than 150mg/L during events of low TDS content. The performance of both sedimentation/filtration systems was highly dependent on the biological maturity of the system and surface water quality.

New phenolic halogenated disinfection byproducts in simulated chlorinated drinking water: Identification, decomposition, and control by ozone-activated carbon treatment

Recently, 13 new phenolic halogenated disinfection byproducts (DBPs) were discovered and confirmed in chlorinated drinking water using ultra performance liquid chromatography/electrospray ionization-triple quadrupole mass spectrometry (UPLC/ESI-tqMS), which have been attracting a growing concern due to their higher chronic cytotoxicity, developmental toxicity, and growth inhibition compared with commonly known aliphatic DBPs. In this study, another 12 new phenolic halogenated DBPs were detected and identified in simulated chlorinated drinking water samples, including two monohalo-4-hydroxybenzaldehydes, two monohalo-4-hydroxybenzoic acids, three monohalo-salicylic acids, and five mono/di/trihalo-phenols. Decomposition mechanisms of these new phenolic halogenated DBPs during chlorination were speculated and partially verified by identifying intermediate products. These new DBPs could undergo hydrolysis, halogenation, substitution, addition, decarboxylation, and rearrangement reactions to form a series of decomposition products, including dihaloacetic acids, 2-halomaleic acids, and a group of new heterocyclic DBPs (trihalo-hydroxy-cyclopentene-diones). A bench-scale ozone-granular activated carbon (GAC) treatment unit was designed and set up in the lab. It was found that ozonation and GAC filtration were effective in reducing dissolved organic carbon levels and aromaticity (DBP precursors) of simulated raw water samples, and thus were effective in decreasing the concentrations of these new phenolic DBPs by 82.5% and 88.6%, respectively. Furthermore, four different treatment scenarios (i.e., ozonation, GAC filtration, ozonation followed by GAC filtration, and GAC filtration followed by ozonation) were evaluated and compared. Results showed that ozonation followed by GAC filtration was most effective in precursor removal and could decrease the level of these new phenolic DBPs by up to 97.3%.

The application of GAC sandwich slow sand filtration to remove pharmaceutical and personal care products

Lab-scale GAC sandwich slow sand filters with different GAC layer depths were evaluated for the first time to remove selected pharmaceutical and personal care products (PPCPs) (namely DEET, paracetamol, caffeine and triclosan, 25 μg/L). Coarse sand (effective grain size of 0.6 mm) was used instead of conventional fine sand. In addition to single sand and GAC filters, GAC sandwich filters were assessed at three filtration rates (i.e. 5 cm/h, 10 cm/h and 20 cm/h) to compare removals. Sandwich filter with 20 cm GAC achieved the best average PPCP removal (98.2%) at 10 cm/h rate. No significant difference of average PPCP removal was found between 10 and 20 cm/h filtration rates for the three GAC sandwich filters (p > 0.05). Among the selected PPCPs, DEET, the recalcitrant compound, was most effectively removed by the GAC sandwich filters. Combining the GAC layers with the slow sand filters significantly enhanced the removal of the target PPCP compounds (p < 0.05), demonstrating that both adsorption and biodegradation contributed to the removals. Furthermore, pseudo-second-order equation (Type 1) could best represent the adsorption kinetics of the four target PPCP compounds onto GAC. In relation to other quality parameters, sandwich filter with 20 cm of GAC also showed good average removals of chemical oxygen demand (COD) of 65.8% and total organic carbon (TOC) of 90.3%, but occurrence of ammonium up to 0.76 mg/L concentration indicated inapplicability of filtration rate of 5 cm/h. No significant difference was found between 10 cm/h and 20 cm/h filtration rates for nitrogen and phosphate removals (p > 0.05). Results of this lab-scale investigation show that GAC sandwich slow sand filter is potentially an effective process for removing PPCPs from tertiary wastewater.

FLASH Technology: Full-Scale Hospital Waste Water Treatments Adopted in Aceh

A Hospital waste water contains a complex mixture of hazardous chemicals and harmful microbes, which can pose a threat to the environment and public health. Some efforts have been carried out in Nangroe Aceh Darussalam (Aceh), Indonesia with the objective of treating hospital waste water effluents on-site before its discharge. Flash technology uses physical and biological pre-treatment, followed by advanced oxidation process based on catalytic ozonation and followed by GAC and PAC filtration. Flash Full-Scale Hospital waste water Treatments in Aceh from different district have been adopted and investigated. Referring to the removal efficiency of macro-pollutants, the collected data demonstrate good removal efficiency of macro-pollutants using Flash technologies. In general, Flash technologies could be considered a solution to the problem of managing hospital waste water.

Drinking water quality and its resources with three different technologies

Surface water and ground water are the basic resources of drinking water insuburban area. Three kinds of waters and were monitored to differentiate its suitability for drinking waters through different technologies used to treat. For three waters characterized results, biological indicators were moderate loads. While, chemical analyses were recorded different water quality indices (WQI). All of the collected samples showed significant improvements in total solids. The only sample that showed slight increases in total solids was the raw water from the surface compared to the other two groundwater resources. In case of system operating with only chlorination for groundwater, increased dosing loads resulted in a bad taste that required GAC filtration units after. In a GAC/RO system operating in water conditions (<500 TDS), reducing the treatment efficiency loading rate to 45% from 60-80% was important for achieving effluent quality more than 150mg/L during events of low TDS content. The performance of both sedimentation/filtration systems was highly dependent on the biological maturity of the system and surface water quality.

Evaluation of a full-scale wastewater treatment plant upgraded with ozonation and biological post-treatments: Abatement of micropollutants, formation of transformation products and oxidation by-products

To protect the ecosystem and drinking water resources in Switzerland and in the countries of the downstream catchments, a new Swiss water protection act entered into force in 2016 aiming to reduce the discharge of micropollutants from wastewater treatment plants (WWTPs). As a consequence, selected WWTPs must be upgraded by an advanced treatment for micropollutant abatement with suitable and economic options such as (powdered) activated carbon treatment or ozonation. WWTP Neugut (105′000 people equivalent) was the first WWTP in Switzerland to implement a long-term full-scale ozonation. Differing specific ozone doses in the range of 0.35–0.97 g O3/g DOC were applied to determine the adequate ozone dose to fulfill the requirements of the Swiss water protection act. Based on this assessment, a specific ozone dose of 0.55 g O3/g DOC is recommended at this plant to ensure an average abatement of the twelve selected indicator substances by ≥80% over the whole treatment. A monitoring of 550 substances confirmed that this dose was very efficient to abate a broad range of micropollutants by >79% on average. After ozonation, an additional biological post-treatment is required to eliminate possible negative ecotoxicological effects generated during ozonation caused by biodegradable ozonation transformation products (OTPs) and oxidation by-products (OBPs). Three biological treatments (sand filtration, moving bed, fixed bed) and granular activated carbon (GAC, fresh and pre-loaded) filtration were evaluated as post-treatments after ozonation. In parallel, a fresh GAC filter directly connected to the effluent of the secondary clarifier was assessed. Among the three purely biological post-treatments, the sand filtration performed best in terms of removal of dissolved organic carbon (DOC), assimilable organic carbon (AOC) and total suspended solids (TSS). The fresh activated carbon filtration ensured a significant additional micropollutants abatement after ozonation due to sorption. The relative abatement of the indicator substances ranged between 20 and 89% after 27′000 bed volumes (BV) and was still substantial at 50′000 BV. In an identical GAC filter running in parallel and being fed with the effluent of the secondary clarifier, the elimination was less efficient. Seven primary OTPs (chlorothiazide and six N-oxides) formed during ozonation could be quantified thanks to available reference standards. Their concentration decreased with increasing specific ozone doses with the concomitant formation of other OTPs. The seven OTPs were found to be stable compounds and were not abated in the biological post-treatments. They were sorbed in the fresh GAC filter, but less efficiently than the corresponding parent compounds. Two OBPs, bromate (BrO3−) and N-nitrosodimethylamine (NDMA), were formed during ozonation but did not exceeded 5 μg/L for bromate and 30 ng/L for NDMA at the recommended specific ozone dose of 0.55 g O3/g DOC. NDMA was well abated in all post-treatments (minimum 41% during fixed bed filtration, maximum 83% during fresh GAC filtration), while bromate was very stable as expected.

A Cost‐Effective Treatment Process for Producing High‐Quality Drinking Water

To reduce capital spending while maintaining water quality goals, american water investigated converting GAC filters from a time‐based regeneration/replacement mode to biofiltration.

Fluorescence spectroscopy and parallel factor analysis as a dissolved organic monitoring tool to assess treatment performance in drinking water trains.

Fluorescence excitation emission matrix (FEEM) spectroscopy was used to evaluate its applicability as a tool to track dissolved organic matter (DOM) in a drinking water treatment plant (DWTP) that incorporates a conventional line (consisting in ozonation and GAC filtration) and a membrane-based line (consisting in ultrafiltration, reverse osmosis and mineralization) working in parallel. Seven sampling points within the different process stages were characterized monthly during 2014. A global Parallel Factor Analysis (PARAFAC) was used to pull out underlying organic fractions from the fluorescence spectra. Accordingly a five components model was selected to describe the system and the pros and cons of the model were discussed by analysis of the residuals. Among the five fluorescent components, those associated to humic-like matter (C1, C3 and C4) showed a similar season variability in the river water feeding the DWTP (which resembled that of UV254 and TOC), whereas the two components associated to protein-like matter (C2 and C5) exhibited a different behavior. The maximum fluorescence intensity values (Fmax) were used to quantify DOM removals across the plant. Compared to the conventional line, water from the UF/RO membrane-based line showed between 6 and 14 times lower fluorescence intensity signal for the humic-like components and between 1 and 3 for the protein-like components as compared to the conventional line. The differences in DOM composition due to seasonal variations and along the treatment trains point out the suitability of using fluorescence measurements over other parameters such as UV254 as a monitoring tool to help optimize operation conditions of each treatment stage and improve produced water quality in a DWTP.

ECONOMIC ASPECTS OF APPLICATION OF PRETREATMENT SYSTEMS BEFORE GRANULAR ACTIVATED CARBON FILTRATION

Abstract Granular activated carbon (GAC) is used for removing an excessive amount of organic contaminants causing undesirable taste, odour or colour of water, and refractive micropollutants, such as heavy metals or toxic organic compounds. However, adsorption is one of the most expensive unit processes used in treatment and renewal of water. This is due to the high cost of granular active carbon and the necessity of its frequent exchange or regeneration. In the paper the authors present the results of the technological and economic analysis of preliminary water treatment systems before GAC filters. The analysis enabled to determine the profitability of these investments taking into account raw water quality and the life of carbon between regenerations. The simulation results showed that it is economically profitable to apply preliminary water treatment independently of analysed pretreatment systems.