Zeolite Column Research Articles

Post-treatment of high-rate activated sludge effluent via zeolite adsorption and recovery of ammonium-nitrogen as alternative fertilising products

This study investigates the potential to connect nutrient flows between wastewater treatment and agriculture through a two-stage nitrogen (N) recovery system composed of high-rate activated sludge treatment in contact stabilisation mode (HRAS/CS) and column adsorption with zeolite. The HRAS/CS process removes organic matter and suspended solids in wastewater, leaving N behind in the effluent. The N was successfully recovered with the zeolite column under different scenarios, generating N and K-rich by-products. The regeneration effluent from the zeolite column with KCl contained 60–845 mg NH4+-N/L and 1.6–14.3 g K/L, having potential for use as fertigation water. The N-saturated zeolite contained 1.5–8.4 mg N/g and 14.3–19.3 mg K/g of the product fresh weight and low contaminant content, making it potentially eligible as various fertilising products. Adsorption can thus concentrate N from HRAS/CS effluent and produce by-products with potential agricultural value while meeting chemical oxygen demand and total nitrogen discharge standards.

Biofiltration matrix optimization for efficient nitrogen removal from domestic onsite wastewater

Bench-scale columns were packed with marble chip, zeolite and gravel to treat septic tank effluent at elevated hydraulic loadings (0.48–0.64 m3 m−2 d−1) to challenge their hydraulic performance and ammonium (NH4+-N) removal performance. The results showed that higher NH4+-N removal efficiency was achieved in zeolite (75.8–94.1 %) and marble chip (54.9–83.9 %) columns than in sand (32.9–76.6 %) column without clogging during the experimental period (4 months). Biochar amendment (30 % v/v) resulted in a 23–29 % decrease of effluent NH4+-N in marble chip columns, while no impact was observed in the zeolite columns. Nitrification rather than adsorption contributed to the major NH4+-N removal (82–95 %) in zeolite, biochar amended zeolite and biochar amended marble chip columns. In addition, higher abundance of nitrifying microorganisms observed in the top layer of zeolite column (1.2 × 107 - 3.1 × 107amoA copies g−1, 3–10 times higher than marble chip) suggested NH4+-N was concentrated on zeolite surface by adsorption which then facilitated nitrification and promoted nitrifying biomass growth. Collectively, this study suggested that zeolite and biochar amended marble chip could serve as the filter materials for efficient NH4+-N removal from onsite wastewater at elevated wastewater loadings without clogging concerns.

Field study of an arsenic removal plant for drinking water using activated carbon and iron in a rural community in the province of Pisco, Peru.

The presence of arsenic in Peru is a serious public health problem due to the geographical extension of populations that consume water with arsenic concentrations above the value recommended by the World Health Organization (WHO). An arsenic removal plant has been studied in a community of 50 families located in the province of Pisco, Peru, a filter media of activated carbon impregnated with iron (AC-Fe) was applied, the adsorption capacity of the material was studied against As(V) and As(III) species, also, a possible decrease in the adsorption capacity of chloride and sulfate ions. Modifications were made to the plant layout based on filtration columns and workflows. The arsenic level was reduced to levels recommended by the WHO, the plant production was estimated at 9,000 volumes of water bed until reaching its breakpoint. An optimum working flow rate of 1.8 m3 h-1 was found, it was also found that the zeolite column used for suspended solids removal did not contribute to the reduction of arsenic concentration, and the presence of ions did not reduce the arsenic removal capacity.

Simulation on the Breakthrough Curve During CO2 Adsorption from Biogas in a Fixed Bed Column

Separation of CO2 gas from the biogas can be accomplished by adsorption process. An adsorbent has a maximum capacity, so the adsorbent will eventually be saturated at a certain time. Therefore, it is necessary to simulate the adsorption mass transfer to produce a breakthrough curve. The breakthrough curve from the simulation of adsorption mass transfer was validated with the experimental data. The research was conducted using variations in temperature and pressure. The mass transfer simulation was solved using the finite difference method. The adsorbent used in this research was 13X zeolite and the biogas was obtained from cow dung waste. Convergent curves can be obtained in numerical simulations as breakthrough curves. This research shows that adsorption should occur at low temperatures and high pressure. Column height and flow velocity also influence the breakthrough time. The comparison of the simulated breakthrough time with experimental data is not much different with R2 0.9969. The striking difference is in the adsorption zone with average relative error (ARE) values ranging from 9.57% to 20.49%. From the results of entropy, enthalpy, and Gibbs free energy calculations, the biogas adsorption research on the 13x zeolite column is an exothermic and spontaneous process

Sustainable mainstream deammonification by ion exchange and bioregeneration via partial nitritation/anammox

The partial nitritation and anammox (PN/A) process has gained popularity for the treatment of nitrogen removal in wastewater due to significant energy savings and its potentially much lower CO2 footprint. However, the treatment of mainstream municipal wastewater by PN/A has been limited mainly due to its unsuitable composition. In this research, we apply ion exchange using a zeolite column to selectively remove and concentrate ammonium from mainstream municipal wastewater. After an absorption phase, the ion exchange column is regenerated using a brine solution. The ammonium rich brine is “bioregenerated” in a PN/A reactor where ammonium is converted to nitrogen gas allowing the brine to be reused in another cycle of ion exchange regeneration. To successfully remove ammonium from the spent brine, anammox and ammonia oxidizing bacteria (AOB) were first cultivated in separate reactors under hypersaline conditions (4.0 %) and later combined in a single PN/A reactor. After continuous operation with sea water, the PN/A reactor treated recirculating brine from the ion exchange column for 48 cycles of ammonium absorption and bioregeneration with minimal blowdown. The various cations of the regenerant solution were stable except for calcium that reached very high values upwards of 3000 mg/L as Ca2+ and finally caused PN/A reactor failure due to mineral precipitation. The buildup of high concentrations of calcium in the regenerant was addressed in two ways: 1) 20 % regenerant replacement per cycle, and 2) precipitation of CaCO3 via the addition of sodium carbonate. Both methods were applied to 30 absorption and bioregeneration cycles each and shown to be effective in keeping calcium concentrations from accumulating in the regenerant allowing for stable PN/A reactor operation.

Graphical method to obtain multicomponent adsorption equilibria from intermediate breakthrough curve plateaus

Adsorption mixture equilibrium data remains challenging to obtain. An established technique is the adsorption breakthrough experiment where the final adsorbed capacities are determined. A graphical method to obtain adsorbed amounts from the intermediate plateaus in the breakthrough curves is proposed in this work. The method is proposed for isothermal, diluted breakthrough tests. Via an integrated capacity curve, the intermediate regions can be extrapolated to extract additional equilibrium points beyond the final state without the need for a multicomponent model. If the column is preloaded, the extra equilibrium points can correspond to multicomponent mixtures as multiple species can have non-zero intermediate concentration plateaus. The method is demonstrated on various simulated examples and then applied on breakthrough data from non-preloaded and preloaded columns of all-silica beta zeolite for diluted methanol/ethanol and diluted ethanol/isobutanol mixtures.

Impact of Long-Term Exposure to High Chlorine and to Low pH Solutions during Chlorine Regeneration of Ammonia-Loaded Zeolite

An earlier study has shown that chlorine solutions were capable of effectively regenerating an ammonium-loaded zeolite column; however, the chlorine concentrations were high (1000 mg Cl2/L), and for two hours of the regeneration cycle, the pH was approximately 3. This led to concerns regarding the long-term durability of the zeolite. The objective of this study is to investigate the durability of a zeolite by conducting long-term batch exposure tests using (a) high concentration chlorine solutions and (b) low pH solutions. Particle size analysis, SEM images, N2 gas adsorption tests, FTIR characterization and batch loading tests showed that 35-day exposure to 1000 mg Cl2/L solutions did not significantly impact the zeolite studied. This chlorine exposure is equivalent to 840,000 ppm-h, which is three orders of magnitude higher than the values recommended by the supplier. The 90-day-long low pH exposure tests showed that pH = 4 solutions only slightly impacted the zeolite’s characteristics and ammonium uptake; however, the pH = 3 exposure led to discernable changes, and the pH = 2 exposure led to an even greater impact. At pH = 2, there was a breakdown of some external part of the zeolite particles, leading to a 7.1-fold increase in the fines and a 56% reduction in the ammonium uptake. The decrease in the ammonium uptake was proportional to the percent of fines.

Effect of Nitrate Presence on Selenium Bioremediation in Chemically Modified Zeolite Columns

Selenium is an essential micro-nutrient for living organisms, but elevated concentrations of it in water can adversely affect health. Nitrate is often found in selenium-contaminated water and negatively correlates with selenium removal. In this study, we investigate the effect of nitrate co-existence on selenium bioremediation in chemically modified zeolite columns. Dynamic sorption-reduction experiments were conducted using natural and iron-coated zeolite columns to remove selenite and selenate oxyanions separately, with and without nitrate anions. Anaerobic sludge was included as microbial inoculum, while lactate was the sole electron donor. The initial selenium concentration (SeIV or SeVI) was 790 µg/L, the nitrate concentration was 620 mg/L, the pH was 7.5, and the flow rate was 3 mL/min. Before introducing nitrate ions, selenium reduction in all four columns reached approximately 99%. However, after introducing nitrate ions, selenate and selenite reduction efficiencies were reduced to approximately 93% and 60%, respectively. Biofilm microbial community composition, assessed by 16S rRNA sequencing, was distinct between the communities with and without nitrate anions. Specifically, in the absence of nitrate, biofilm communities are mainly composed of selenium-reducing bacteria (Veillonella, Bacteroides and Escherichia). In contrast, the presence of nitrate led to mostly denitrifying bacteria (Anaeromusa-Anaeroarcus, Lentimicrobium, Azospirillum and Endomicrobium). Further, comparison of diversity indices (Shannon index, Faith PD and Pielou’s) shows alteration in all indices in the presence of nitrate.

Microbial Enhancement of Selenium Removal in Chemically Modified Zeolite Columns

Selenium (Se) is an essential micro-nutrient for living organisms, but elevated concentrations in water can adversely affect health. In this research, we investigate the removal of selenium oxyanions (selenate and selenite) in aqueous systems by integration of adsorption on modified zeolites and microbial reduction. Dynamic sorption-reduction experiments were conducted using two sets of zeolite columns for the removal of selenite and selenate oxyanions, respectively. In each case, one column was fully packed with natural, unmodified zeolites, while the other column was composed of 80% natural and 20% iron-coated zeolites, by mass. The initial selenium concentration, selenite (SeIV) or selenate (SeVI), was 790 μg/L, the pH was 7.5, and the flow rate was 3 mL/min. Initially, as expected, the higher selenate removal (34%) was observed with coated zeolite, twice as high compared to the results with unmodified zeolite. Maximum selenite removal was 89% in the column with modified zeolite. Within approximately 14 days, as the biofilm developed inside the columns, selenium reduction in all four columns reached approximately 99%. Biofilm microbial community composition, assessed by 16S rRNA sequencing, is consistent with the presence of mainly selenium-reducing bacteria (Veillonella, Bacteroides, and Escherichia). Selenium oxyanions were reduced to elemental selenium, visible within the bioreactors as red-color aggregates.

Treatment of Agricultural Waste Using a Combination of Anaerobic, Aerobic, and Adsorption Processes

The generation of waste in agricultural and livestock industries, followed by inadequate treatment and uncontrolled disposal to natural recipients, results in significant environmental pollution. Thus, the efficient and integrated management of high-organic-load waste produced in such activities is a key factor for sustainability and the protection of aqueous matrices. In this work, we investigate an integrated management approach for the treatment of agricultural, high-organic-load waste via a combination of processes, with an ultimate goal to improve the characteristics of the final waste and enhance the valorization of the nutrients contained in it. Towards this direction, a waste mixture comprising pig waste, cheese dairy, and food residues was sequentially treated in a laboratory scale by anaerobic digestion, followed by activated sludge (aerobic–anoxic treatment), and last by adsorption using natural zeolite. The efficiency of two different adsorption routes was examined (magnetically agitated zeolite or packed zeolite column), while the effect of the granule sizes of zeolite (0–1 mm or 1.5–3 mm) was also evaluated with regards to the remediation of the final effluent. Excellent adsorption capacities were observed in all cases, with the larger-sized zeolite exhibiting a superior performance, while the granule size of zeolite significantly affected the lifetime of the packed columns, as the smaller-sized zeolite columns reached their saturation point faster than the larger-sized zeolite analogue. The average ammonium nitrogen removal in the column experiment was ~92%, while total phosphorus was ~68%, respectively. Overall, an almost complete remediation of the final effluent was observed when compared with the physicochemical parameters of the initial waste, with a ~96% chemical oxygen demand, ~79% total nitrogen, ~96% total phosphorus, and ~82% phenols concentration decrease, signifying the high performance of the sequential treatment strategy proposed herein.

Fluid transport in porous media based on differences in filter media morphology and biofilm growth in bioreactors

To elucidate the effect of pore structure on bioclogging and seepage flow in bioreactors, we used X-ray computed tomography (X-CT) to investigate the changes in seepage flow of porous media in zeolite, gravel and ceramsite bioreactors with biofilm growth by injecting a non-ionic contrast medium iohexol. Based on the X-CT images using a ball-and-stick model, the highest average pore radius (R‾) and the average pore throat radius (r‾) in the ceramsite column were found under the initial conditions, which facilitated its permeability. The pore and throat of the gravel column were small and homogeneous relatively. Biofilm growth decreased the pore and pore throat in the columns. The total throat area of zeolite, gravel and ceramsite columns declined by 74%, 73% and 79% respectively. The zeolite column had the highest average pore throat, which contributed to its maximum conductivity subsequently after biofilm growth. Further, the fractal dimensions of the pore structure increased with biofilm growth, especially in the zeolite and ceramsite columns. The heterogeneity of the porous media was reinforced by the biofilm growth in the zeolite and ceramsite columns due to their higher heterogeneity initially. We also observed that an increase in heterogeneity of porous medium amplified the preferential flow and flow heterogeneities, especially in the zeolite and ceramsite columns.

Chlorine vs. Sodium Chloride Regeneration of Zeolite Column for Ammonium Removal from an Explosives Impacted Mining Wastewater

There has only been limited research on ammonium removal by zeolites followed by chlorine regeneration; these studies used batch tests and, in many cases, only dealt with single solute solutions as opposed to multi-component ones. To better simulate full-scale applications, this study used a continuous-flow ion exchange (IE) column system to assess the feasibility of chlorine regeneration of a zeolite IE column used for the removal of ammonium from synthetic explosives impacted mining wastewater (EIMWW). Multi-cycle column loading-regeneration tests were used to evaluate and compare the performance of a NaOCl (1000 ppm as free Cl2) solution with that of a standard salt regeneration solution (5% NaCl). In addition, the impact of two loading cycle durations was evaluated. After three operational cycles with 6 h loading phases, the TAN (total ammonia nitrogen) uptake after NaOCl regeneration was almost the same as that obtained with salt regeneration (0.21 meq/g vs. 0.21 meq/g). The zeolite with NaOCl regeneration showed a higher preference for TAN than with NaCl regeneration (Ca:TAN:K = 2.8:2.3:1 vs. 2.5:1.9:1 for the 6 h loading phase); however, the NaOCl regeneration took longer to complete. It was also found that effluent pH, total chlorine level, and free chlorine level during the chlorine regeneration were positively related, seemingly confirming that the ammonium is oxidized to nitrogen gas and producing hydrogen ions. Regardless of the regeneration solution, if one uses a two-column system, with one column online and the other offline, the shorter loading cycles (6 h) yield a substantially higher daily TAN removal rate.

Separation of hydrocarbon mixture of neopentane and n-hexane using NaY zeolite: Large distinct diffusivity.

A recently proposed method based on Levitation and Blow torch effects, is employed here to see if it can separate a mixture of neopentane and n-hexane. The results show that the mixture can be separated with a hot zone temperature of just 40 K above the ambient temperature, 300 K. The two components are found to accumulate at the two extreme ends of the zeolite column. The computed separation factor is in the range of 1015 -1020 (as compared to 104 for existing separation methods). The energy expense for the separation is significantly smaller than for existing separation methods by several orders of magnitude. Transport (D11 ), self (Ds ), and distinct diffusivities (Dd ) of the mixture were computed. The contribution of distinct diffusivity to the transport diffusivity is 70% as compared to 10%-30% seen in other separation methods and is larger by 2.3 times as compared to the self-diffusivity.

High purity separation of n-pentane from neopentane using a nano-crystal of zeolite Y.

A method for the separation of a mixture of n-pentane and neopentane using a nano-crystallite of zeolite Y is reported. This method judiciously combines two well-known, counter-intuitive phenomena, the levitation and the blowtorch effects. The result is that the two components are separated by being driven to the opposite ends of the zeolite column. The calculations are based on the non-equilibrium Monte Carlo method with moves from a region at one temperature to a region at another temperature. The necessary acceptance probability for such moves has been derived here on the basis of stationary solution of an inhomogeneous Fokker-Planck equation. Simulations have been carried out with a realistic and experimentally relevant Gaussian hot zone and also a square hot zone, both of which lead to very good separation. Simulations without the hot zones do not show any separation. The results are reported at a loading of 1molecule per cage. The temperature of the hot zone is just ∼30K higher than the ambient temperature. The separation factors of the order of 1017 are achieved using single crystals of zeolite, which are less than 1 μm long. The conditions for including the hot zone may be experimentally realizable in the future considering the rapid advances in nanoscale thermometry. The separation process is likely to be energetically more efficient by several orders of magnitude as compared to the existing methods of separation, making the method very green.

Minimizing greenhouse gas emissions from leachate treatment by using zeolite column

In this study, by using a fluidized bed reactor, anaerobic treatment of young landfill leachate was performed to observe carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) emissions. Greenhouse gas (GHG) emissions from an anaerobic fluidized bed reactor (AFBR) were calculated through a developed model based on IPCC approach. During 270 days of operation, it was reported that CH4 was the major emitted greenhouse gas with the highest values. Also, N2O and CO2 have been emitted from an AFBR. To minimize the GHG emissions, a zeolite column reactor was used for the reduction of the GHG emissions during 60 days of operation. Static chamber method was applied to measure the emissions from the zeolite column reactor. It was observed that GHG emissions from leachate treatment was minimized by applying an adsorption process with zeolite. CO2 emission was 0 at the end of 46 days. N2O emission was zero at 27th day. The emission of methane was also reduced up to 32%. The emission of CH4 emission was minimized at nearly 4.75 kg CO2e/d. Thus, it can be said that zeolite could adsorb CO2, CH4 and N2O gases and minimize GHG emissions.

Ammonia-Ca-K competitive ion-exchange on zeolites in mining wastewater treatment: batch regeneration and column performance

This manuscript addresses the treatment explosives-impacted mining wastewaters (EIMWW) using ion-exchange to remove elevated levels of ammonia. Repeated batch loading-regeneration cycles were conducted for two commercially available zeolite media used in the treatment of ammonia-ladenEIMWW to establish the effects of competing ions and regeneration solution composition. The Northern Ontario EIMWW tested contained 3.87 meq/L total ammonia (TA) as well as 2.85 meq/L Kþ and 3.9 meq/L Ca2þ.The media studied were a natural clinoptilolite and a modified clinoptilolite (SIR-600). Five regenerant solutions with different NaCl and KCl concentrations were evaluated. The presence of potassium in the regenerant was found to hinder the TA exchange capacity of both zeolites. The SIR-600 and the natural clinoptilolite used in conjunction with the 10% NaCl solution featured the best TA exchange capacities, 0.46 ± 0.02 meq TA/g and 0.36 ± 0.05 meq TA/g, respectively. The batch tests showed that both media had a slight preference for Kþ over TA. The continuous flow column tests performed using SIR-600 media greatly accentuated the selectivity of Kþ over TA. In reaching the same 0.55 meq TA/L breakthrough level, the same modified zeolite column was able to treat five time more volume of a synthetic TA solution than EIMWW.

Separating Hydrocarbon Mixtures by Driving the Components in Opposite Directions: High Degree of Separation Factor and Energy Efficiency.

A radically different approach for separation of molecular mixtures is proposed. A judicious combination of levitation effect observed in zeolites with a counter intuitive Landauer blow torch effect provides driving forces for the two components of the mixture to move in opposite directions. Using nonequilibrium MonteCarlo simulations, we illustrate the efficacy of the method for separating real mixtures of both linear n-pentane and its branched isomer, neopentane, and linear n-hexane and its branched isomer, 2,2-dimethylbutane. The method yields several orders of magnitude improvement in separation factor and relative energy efficiency by using submicron zeolite column. The extremely high purity of the resulting single components makes the method best suited for green chemistry.

Experiment research on physical clogging mechanism in the porous media and its impact on permeability

The physical clogging of porous medium is a significant problem that impacts the performance of infiltration systems. Although the physical clogging has been extensively studied, the mesoscopic mechanism and clogging dynamic in the porous medium are still unclear. This paper focuses on the migration characteristic and physical clogging mechanism of suspended solid (SS) particles in gravel and zeolite columns. The results indicate that the permeability of the filter medium significantly decreases at the initial stage of SS infiltration and reduces to a steady value as the accumulated SS load increases. The permeability of the porous medium decreases as the particle size of the filter medium decreases, while lower particle sphericity and coarser particle texture also result in a reduction in the permeability of the porous medium. X-ray computed tomography was used to obtain images during the infiltration of the SS particles through the substrates. Due to the formation of a clogging layer, the intrusion of subsequent SS inflow can be prevented, leading to the formation of a blanket depositional layer. The ratio between the particle size of the filter medium and the SS particles controls the migration of the SS particles within the porous medium. Additionally, in this experimental study, the threshold is affected by the particle shape and texture of the filter medium. Considering the reduction in the permeability of porous medium by the clogging layer, a simple double-layered analytical model that considers SS accumulation was proposed to estimate the variation in the permeability, which agrees well with the experimental measurements.

Integration of an anaerobic fluidized-bed membrane bioreactor (MBR) with zeolite adsorption and reverse osmosis (RO) for municipal wastewater reclamation: Comparison with an anoxic-aerobic MBR coupled with RO.

This study compared the performance of an anaerobic fluidized bed membrane bioreactor (AFMBR)-zeolite adsorption-reverse osmosis (RO) system and an anoxic-aerobic MBR-RO system for municipal wastewater reclamation. Both MBR-RO systems were operated in parallel with the same operating conditions. The results showed that the MBR systems achieved excellent organic removals (>95%) and the anoxic-aerobic MBR could also remove ∼57% of soluble total nitrogen. Compared to the aerobic MBR, the AFMBR displayed better membrane performance with less energy consumption, attributed to effective membrane scouring by liquid-fluidized GAC particles. Furthermore, a zeolite column was employed to remove ammonia in the AFMBR permeate, which ensured comparable organic and nitrogen levels in the feeds to RO units in the two processes. Although less organic substances and microbial cells were accumulated on the RO membrane fed with AFMBR-zeolite column effluent, its fouling rate (∼6.5±2.2bar/day) was significantly greater than that fed with anoxic-aerobic MBR permeate (∼1.1±1.5bar/day). This may be associated with more severe inorganic colloidal fouling on the RO membrane, illustrated by an electrical impedance spectroscopy fouling monitoring system.

A Hybrid Phase I-Phase II Toxicity Identification Evaluation (TIE) for the Simultaneous Characterization and Identification of Toxicants of Concern in Coastal and Estuarine Environments.

A sequential TIE procedure combining in a single framework Phase I manipulations and Phase II methods, including chemical analyses and complementary Phase I treatments, was proposed for characterization and identification of toxicants of concern in estuarine environments. Interstitial water was chosen as test matrix and embryo-larval development with the bivalve Crassostrea gigas as toxicity endpoint. TIE treatments included addition of Ulva rigida and elution through zeolite column for addressing effects due to ammonia, addition of EDTA and elution through a Cation-Exchange Solid-Phase Extraction column for characterize metals, and elution through two different type of polymers (XAD and DPA) with different affinity for polar and nonpolar organic pollutants. Chemical analyses concerned determination of ammonia and trace elements in the untreated sample and after manipulation intended to remove or modify bioavailability of ammonia and metals. The "hybrid" Phase I-Phase II TIE sequence proved to be a reliable and effective tool for the identification of main toxicant of concern in a highly toxic and contaminated interstitial water sample, also in presence of high concentration of potential confounding factors (ammonia). The addition of U. rigida was the more reliable treatment for the removal of ammonia, due to the concurrent release of particles and potentially toxic elements, such as Ba, Rb, and Tl by zeolite column, which may increase toxicity in the post-column sample. The combined use of polymers with different affinity for the various classes of organic pollutants was essential to identify the contribution of polar organic compounds to the observed toxicity.