Search

Copyright of International Journal of Advances in Engineering & Pure Sciences is the property of Marmara University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

We investigated the removal of the reactive dye Remazol Red from segregated dye bath with an integrated physical-biological approach combining easy applicability and fast kinetics of the sorption process with intrinsic sustainability of biological treatments. The proposed process consists in a first step dye removal by sorption on a cheap commercial polymer (Hytrel 8206) followed by anaerobic polymer bioregeneration. Excellent dye removals were achieved (up to 100%) under acidic conditions with fast kinetics (in most cases, 4 h are sufficient to reach efficiencies ≥ 80%). Experimental sorption data were well correlated with the Freundlich isotherm and pseudo-first-order kinetic model. The sorption process was optimized with response surface methodology. Practically complete removal was achieved with pH of the solution, initial dye concentration and polymer-to-water ratio equal to 4, 50 mg/L and 8.03% v/v, respectively. High desorption performance under neutral conditions makes Hytrel suitable for bioregeneration in a two-phase partitioning bioreactor. Polymer bioregeration reached 82% efficiency with the added value of achieving effective biodegradation (> 50% in 4 days) of the dye desorbed from the polymer. The study demonstrated the two-step process feasibility, which is characterized by the advantage of employing a cheap commercial polymer and has the potential of achieving complete dye mineralization. [ABSTRACT FROM AUTHOR]

Bioregeneration of activated carbon (AC) is used to describe the renewal of the adsorptive capacity of AC by microorganisms for further adsorption. Recently, bioregeneration of AC has attracted more attention due to its potential to overcome some challenging of costly ex-situ regeneration methods. This study aims to investigate the bioregeneration of powdered activated carbon (PAC) loaded with paracetamol (PAR) and the effect of sludge retention time (SRT) on bioregeneration. A modified method was used to determine the bioregeneration, and also the adsorption and desorption kinetics of PAR onto PAC and the degradation of PAR in abiotic/biotic conditions were assessed to reveal the bioregeneration mechanism. The adsorption efficiency of PAR onto PAC at equilibrium conditions was as high as 99.8%. The isotherm and kinetic model studies showed that chemisorption was dominant in the adsorption of PAR onto PAC. The desorption efficiency of PAR from PAC was 26.3% in the abiotic conditions although PAR is a hydrophilic pharmaceutical active compound (PhAC). The bioregeneration efficiencies of PAC at the SRTs of 10, 30 and 60 days were determined as 17.3, 26.8 and 20.1%, respectively. The concentration gradient contributed 11.4% to the bioregeneration efficiency at all SRTs and the difference between the bioregeneration amount and the concentration gradient was attributed to the extracellular enzymatic activity. The bioregeneration efficiency at the SRT of 30 days was the highest among all SRTs and the more dominant mechanism in bioregeneration was found as the extracellular enzymatic activity at this SRT. The low desorption capacity limited the bioregeneration efficiency in all SRTs due to the low adsorption reversibility caused by chemisorption although the biodegradability of PAR was high at all SRTs tested in this study. [ABSTRACT FROM AUTHOR]

Ammonia nitrogen (NH4+-N) is widely found in aquifers with strong reducibility or poor adsorptivity as a dissolved inorganic nitrogen pollutant. The application of adsorbents with effective long-term in situ bioregeneration as permeable reactive barrier (PRB) media for nitrogen removal has raised concern. In this study, the advantage of natural diatomite as a PRB material was investigated by exploring its NH4+-N adsorption and desorption characteristics, and the ability of diatomite and zeolite to be loaded nitrifying bacteria was also compared. The results showed that the exchangeable ammonium from chemical-monolayer adsorption was the main form of NH4+-N and was adsorbed by diatomite. Moreover, the adsorption process was limited with a maximum adsorption capacity of 0.677 mg g−1. However, diatomite demonstrated an excellent loading of aerobic-heterotrophic microorganisms, even stronger than zeolite. Compared with zeolite reactors, a higher OD600 value of nitrifiers, a faster NH4+-N degradation rate and more abundant functional genes were observed during the bioregeneration process of diatomite. Both the solution and exchangeable ammonium forms were bioavailable, and the regeneration of diatomite was more than 80.0% after two days. Moreover, desorption-biodegradation was systematically analysed to determine the bioregeneration mechanism of diatomite. Diatomite with good regeneration ability can be used as a competitive alternative to address sudden nitrogen pollution. [ABSTRACT FROM AUTHOR]

Copyright of Polish Journal of Sports Medicine / Medycyna Sportowa is the property of Agencja Wydawnicza Medsportpress Sp. z o. o. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Highly variable flow has to be expected in decentralized greywater treatment and can lead to intermittent operation of the treatment system. However, few studies have addressed the influence of variable flow on the treatment performance of a biological activated carbon filter (BAC). In this study, we investigated the influence of intermittent flow using small-scale BAC columns, which treat greywater as a second treatment step following a membrane bioreactor (MBR). Three operating strategies to respond to variable flow were evaluated. The activated carbon was characterized before and after the experiments in terms of biological activity and sorption capacity. The performance of the BAC filters was assessed based on total organic carbon (TOC) removal, TOC fractions and growth potential. No significant differences were observed between constant flow compared to on-off operation with intermittent flow over the range of tested influent concentrations. Peaks with high TOC during 24 h periods were attenuated by sorption and biological degradation. Adsorbed TOC was released after switching back to normal concentrations for influent concentrations more than 5 times higher than usually observed, the BAC functioned as a temporary sink. In line with these results, the high influent TOC values led to increased biological activity in the filter but did not influence the sorption capacity. The experiments showed that intermittent flow does not negatively impact the performance of a BAC and that there is no need for additional equalization tanks to buffer the variable flow, for example in household-scale greywater treatment.

• A polymer-clay-bacteria composite for formaldehyde (FA) bioremediation is presented. • The composite lowers FA levels and neutralizes pH to make biodegradation possible. • Immobilized bacteria removed 15 times more FA than free cells over several cycles. • FA binding sites were regenerated by the bacteria without an active clean-up stage. A multi-functional, self-regenerating material was designed to adsorb and biodegrade formaldehyde from water in a simple, one-step process. The material is based on montmorillonite clay, polyethyleneimine and formaldehyde-degrading Pseudomonas putida , and has three unique functions which facilitate bioremediation: a. selectively adsorbs formaldehyde to reduce cytotoxicity, b. buffers the solution to allow efficient biodegradation, and c. self-cleans through slow release of formaldehyde and subsequent degradation by the attached bacteria, allowing regeneration and long-term use of the material. A polyethyleneimine-clay composite was optimized to carry positive surface charges and a high concentration of functional amine groups, which facilitated formaldehyde adsorption and bacterial adhesion. Formaldehyde binding was specific, yet reversible and pH dependent; binding fitted the Langmuir model and had a q max of 62 mg·g−1 composite. A formaldehyde-degrading Pseudomonas putida strain was then immobilized on the positively charged composite through electrostatic interactions. The efficiency of the resulting bio-composite was demonstrated for multiple successive treatment cycles, with degradation rates as high as 1600 mg·L−1·FA·h−1. This self-regenerating one-step process is a promising solution to the challenging drawbacks of formaldehyde remediation and could also help design other adsorption-degradation platforms for wastewaters that demand complicated treatment strategies. [ABSTRACT FROM AUTHOR]

• Different strength wastewater was treated in a zeolite amended GAO biofilm system. • COD uptake rate and PHA synthesis rate increased with influent organic content. • Zeolite bioregenerated via simultaneous nitrification and PHA based denitrification. • Total treatment time did not increase proportionally to the wastewater strength. • Rapid proliferation of Candidatus competibacter and Nitrospira were observed. Conventional aerobic treatment of high-strength wastewater is not economical due to excessively high energy requirement for compressed air supply. The use of passive aeration avoids the use of compressed air and enables energy efficient oxygen supply directly from the air. This study evaluates a passively aerated simultaneous nitrification and denitrification performing biofilm to treat concentrated wastewater. The biofilm reactor was operated > 5-months under alternating anaerobic/aerobic conditions. For 4-times concentrated wastewater, > 80% COD (2307 mg L−1 h−1) and > 60% N (60 mg L−1 h−1) was removed at a hydraulic retention time (HRT) of 7 h. A double application in the same reactor enabled > 95% COD and 85% N-removal, at an overall HRT of 14 h which is substantially shorter than what traditional activated sludge-based systems would require for the treatment of such concentrated feeds. Microbial community analysis showed Candidatus competibacter (27%) and nitrifying bacteria (Nitrosomonas, and Nitrospira) as key microbes involved in COD and N-removal, respectively. [ABSTRACT FROM AUTHOR]

Iron and non-ferrous metals has been shown to accumulate in the liquid phase during the two-step biohydrometallurgical treatment of copper–zinc concentrate. The removal of iron as a precipitate from a solution obtained after ferric leaching of the concentrate and its subsequent bioregeneration has been studied. Iron was almost completely (98.3%) removed from the liquid phase as jarosite, and the pH value increased up to 2.4 with the addition of lime. About 95% of non-ferrous metals remained in the solution as sulfates. Comparative analysis of the obtained precipitates (including waste from the two-step process) showed that the loss of non-ferrous metals for them was lower than that in waste from the mining of copper–zinc ores and copper smelters. [ABSTRACT FROM AUTHOR]

Abstract Polymetallic concentrates obtained during ore beneficiation pose a significant problem for the mining and metallurgy industry due to an increase in load on subsequent comminution steps and a high loss of metals in slag during smelting. Storage of such slag can lead to pollution of groundwater due to weathering. Biohydrometallurgy is an option for the processing of sulfidic raw materials that has a low impact on the environment. Processing of sulfidic concentrates of copper-zinc ore via bioleaching techniques was studied in this paper. Three mixed microbial cultures of acidophilic microorganisms were enriched from industrial mining sites: two autotrophic mesophilic cultures containing Acidithiobacillus ferroxidans and Leptospirillum spp. (grown at 30 and 35 °C), and a mixotrophic moderate thermophilic culture containing Sulfobacillus thermotolerans , Leptospirillum ferriphilum , as well as the archaea Ferroplasma acidiphilum and Acidiplasma spp. (grown at 40 °C). The autotrophic microbial culture growing at 30 °C was used to generate an iron-containing biosolution for ferric leaching of a copper-zinc concentrate. Zinc and iron extracted into solution faster than copper during high-temperature (80 °C) ferric leaching of the concentrate due to galvanic interactions between minerals, redox conditions of the medium, and differences between mineral oxidation mechanisms. Weight loss of the leach residue was 34.0%, with relative copper content increased by 1.0%, zinc content decreased by 6.18%, and iron content decreased by 15.1%. Biooxidation of ferrous iron in the pregnant leach solution by three microbial cultures was also studied. The most effective culture was moderate thermophilic. The results of studies on the bioregeneration of leaching solutions are relevant to the development of a two-step biohydrometallurgical technology for processing of copper-zinc concentrate with a closed cycle of technological flows. The ferrous iron biooxidation rate by the moderate thermophilic culture reached 20 g L−1 day−1. The leach residue obtained can be considered a high-grade copper concentrate able to be processed via smelting. This bioleaching process would make it possible to reduce pollution of groundwater by some toxic metals stored in slags. An environmentally friendly technology flow sheet for copper-zinc sulfidic ore processing using two-step bioleaching treatment was proposed. Graphical abstract Image Highlights • А new leaching biotechnology for processing of copper-zinc concentrate was proposed. • The proposed technology decreases the losses of non-ferrous metals in slags. • The two-step technology has a closed cycle of technological flows. • The technology will decrease ecological risks of pyrometallurgical enterprises. • Two-step technology is a part of eco-friendly copper-zinc ore processing. [ABSTRACT FROM AUTHOR]

Bioregeneration is a process of restoring the adsorptive capacity of the spent adsorbents through microbial action. In this study, the effects of acclimated biomass concentration, biomass acclimation concentration, dosage of granular activated carbon (GAC) and type of GAC on the bioregeneration efficiency (BE) of GAC loaded with phenol and p-nitrophenol (PNP), respectively, were investigated. The quantification was conducted by monitoring the time courses of adsorbed substrate amount during bioregeneration under the sequential adsorption and biodegradation approach. The mean BEs of phenol- and PNP-loaded GAC were found to be 78 ± 2 and 77 ± 1%, respectively. The results revealed that increasing acclimated biomass concentration and adsorbent dosage did not have an observable effect on the BEs of phenol- and PNP-loaded GAC. Additionally, the BEs were found to be almost the same for the bioregeneration of phenol-loaded GAC using biomass acclimated to 350 and 600 mg/L of phenol, respectively. The BEs of phenol-loaded GAC 830 (thermal-activated) and GAC 1240+ (thermal- and acid-activated) did not show any observable difference, but the BE of PNP-loaded GAC 1240+ was found to be greater than that of PNP-loaded GAC 830 indicating that the improvement of BE of spent GAC through further chemical activation was dependent on the type of adsorbate. [ABSTRACT FROM AUTHOR]

A comparative study of the oxidation of ferrous iron ions by various cultures of acidophilic chemolithotrophic microorganisms in solutions obtained after ferric leaching of copper-zinc concentrate at 80°C has been carried out. It was shown that the use of a moderately thermophilic culture for bioregeneration of leaching solutions was preferable. At the same time, the oxidation rate of Fe2+ ions reached 0.88 g/(L h), or 21.1 g/(L day). We propose that the activity of the moderately thermophilic culture was due to the presence of the mixotrophic bacteria Sulfobacillus spp., which used organic products of the microbial lysis for their growth. These products were formed during high-temperature ferric leaching of the copper-zinc concentrate with the biosolution. [ABSTRACT FROM AUTHOR]

The article shows that purification of water of 2-nitrophenol the term of the effective operation of biological activated carbon is increased by 1-1.5 month in fulfilling periodic offline aeration of the sorbent (4-7 days) with addition of nutrients. In this case 60-80% of restored pores volume was freed of products of vital activities of microorganisms. [ABSTRACT FROM AUTHOR]

Among various adsorbents studied, sulfur-impregnated activated carbon is one of the most promising adsorbents for mercury removal from flue gas. However, a large amount of spent activated carbons containing high content of mercury are generated after adsorption. To make the adsorption a more viable option, the regeneration and reuse of the spent activated carbon should be considered. The purpose of this study is to develop a novel technique for bioregeneration of sulfur-impregnated activated carbons after adsorption of mercury from flue gases by sulfur-oxidizing bacteria. The optimal operating parameters for this bioregeneration process were studied using central composite design (CCD) and response surface methodology (RSM). Results showed that the sulfur oxidation rate was increased with increasing activated carbon dosage. Furthermore, the increase of inoculum size only caused a slight increase of sulfur oxidation rate in the bioregeneration. The maximum mercury removal efficiency of more than 50% was obtained at 10% (w/v) activated carbon dosage and 20% (v/v) inoculum size. After the bioregeneration process, Brunauer–Emmett–Teller (BET) surface area and micropore volume of spent activated carbon increased due to the bio-oxidation of mercury bearing sulfur on the surface of activated carbons. [ABSTRACT FROM AUTHOR]

This is the first attempt to explore the sustainability of aged refuse as ammonium-removal media. Batch experiments combined with the aged-refuse-based reactor were performed to examine how the adsorption and desorption processes are involved in the ammonia removal via aged refuse media in this research. The results showed that the adsorption of ammonium by aged refuse occurred instantly and the adsorbed ammonium was stable and less exchangeable. The adsorption data fit the Freundlich isotherms well and the n value of 0.1–0.5 indicated that the adsorption of ammonium occurred easily. The maximum adsorbed ammonium occupied less than 10% of the cation exchange capacity in aged-refuse-based reactors owing to the high solid/liquid ratios (50:1–120:1). The synergistic transformations of ammonium within the aged-refuse-based reactor indicated that the cation exchange sites only provide temporary storage of ammonium, and the subsequent nitrification process can be considered the predominant restoration pathway of ammonium adsorption capacity of the reactor. It seems reasonable to assume that there is no expiry for the aged-refuse-based reactor in terms of ammonium removal owing to its bioregeneration via nitrification. [ABSTRACT FROM AUTHOR]

The effects of dry biomass density in cryogel beads, shaking speed and initial concentration ratio of phenol to 4-chlorophenol (4-CP) on the bioregeneration efficiencies of binary phenol and 4-CP-loaded granular activated carbon (GAC) for phenol and 4-CP, respectively, were investigated under the simultaneous adsorption and biodegradation approach. The results revealed higher bioregeneration efficiencies of binary-loaded GAC for phenol and 4-CP at higher dry biomass density but moderate shaking speed. The optimum dry biomass density in cryogel beads and shaking speed for use in bioregeneration were found to be 0.01 g/mL and 250 rpm, respectively. With respect to the initial phenol to 4-CP concentration ratio, the bioregeneration efficiencies were lower under increasing phenol and 4-CP initial concentrations, respectively, with the effect being more conspicuous under increasing 4-CP concentration. Higher bioregeneration efficiencies were achieved with the use of immobilized rather than suspended biomasses. [ABSTRACT FROM AUTHOR]

The bioregeneration of activated carbon (AC) in biological activated carbon (BAC) systems is limited by sorption-desorption hysteresis and transport between the adsorbent and biomass. In this study, we investigated these limitations and whether a biofilm covering the AC surface is required. Consequently, BAC reactors were operated at different shear stress and AC surface smoothness, since this may affect biofilm formation. The experiments were carried out in BAC and blank reactors treating synthetic wastewater containing the pharmaceutical metoprolol. After start-up, all reactors removed metoprolol completely; however, after 840 h the removal dropped due to saturation of the AC. In the blank reactors, the removal dropped to 0% while in the BAC reactors removal recovered to >99%, due to increased biological activity. During the initial phase, the metoprolol was adsorbed, rather than biodegraded. At the end, the AC from the BAC reactors had higher pore volume and sorption capacity than from the blank reactors, showing that the AC had been bioregenerated. At high shear (G = 25 s −1 ), the rough AC granules (R a = 13 μm) were covered with a 50–400 μm thick biofilm and the total protein content of the biofilm was 2.6 mg/gAC, while at lower shear (G = 8.8 s −1 ) the rough AC granules were only partly covered. The biofilm formation at lower shear (G = 8.8 s −1 ) on smooth AC granules (R a = 1.6 μm) was negligible. However, due to the presence of suspended biomass the reactor performance or bioregeneration were not reduced. This showed that direct contact between the AC and biomass was not essential in mixed BAC systems. The microbial analyses of the suspended biomass and the biofilm on AC surface indicated that metoprolol was mainly biodegraded in suspension. [ABSTRACT FROM AUTHOR]

This paper has investigated bioregeneration of biologically activated carbon (BAC) from procaine. The study has shown low efficiency (up to 25%) of desorption of procaine by aqueous solutions even at heating up to 80°C. In the course of bioregeneration media of spent BAC was recovered a small degree of adsorption capacity of the sorbent and by two times enhanced the ATP-ase activity of the biofilm, which increased the efficiency of the operation of biosorbents 2.5 and 3.25 times after respective 4 and 10 days of bioregeneration. A positive effect of bioregeneration affects further biofiltration about 1000 c.v. of the model solution. [ABSTRACT FROM AUTHOR]

Contents A placenta is defined as structural approximation of maternal and foetal tissues to perform physiological exchange. Associated processes of differentiation and the establishment of its cells take place within the extracellular matrix ( ECM) that provides a rich environment of collagens, fibronectins, cytokines and other components. Placental ECM is promising for tissue regeneration purposes, because it has immune tolerance capacities that may cause only minimal rejections of transplants with immunological differences between donor and recipient. However, specific characteristics of ECM during evolution of the structurally very diverse mammalian placenta are not yet revealed. We here address the major aspects of placental types, that is non-invasive (epitheliochorial), medium (endotheliochorial)-to-high (haemochorial) invasive nature of the interhemal barrier between the foetal and maternal blood system as well as their main components of ECM with special reference to species that are commonly used as animal models for human placentation and in the potential applications for regenerative medicine. [ABSTRACT FROM AUTHOR]

The adsorption of acid blue 74 (AB74), basic green 1 (BG1) and reactive blue 4 (RB4) on carbons from pine sawdust (Ps) using single carbonization (C-Ps) and modification of Ps with a calcium chloride 1 M (C-Ps-Ca) was studied. Also the effects of the type of adsorbate (acid, basic and reactive dye) on the bioregeneration of exhausted carbons using Pseudomona putida were investigated. Characterization of the samples was performed using Nitrogen adsorption isotherms at 77 K, elemental analysis, FT-IR spectroscopy and SEM-EDX analysis. For this study, the maximum adsorption capacity obtained for the two types of carbons were for C-Ps: 12.8, 4.6 and 51.68 mg g −1 , and for C-Ps-Ca: 38.3, 48.6 and 155.1 mg g −1 , for AB74, RB4 and BG1 dyes respectively. The bioregeneration process showed that is possible to renovate 25% of original adsorption capacity of the carbon C-Ps-Ca, equivalent to the adsorption capacity of C-Ps carbon. Among the dye-loaded adsorbents, the bioregeneration efficiency of C-Ps-Ca using the bacteria Pseudomona putida showed a better capacity for the degradation of BG1 compared with AB74 and RB4. Modelling of the adsorption results using a non-linear regression approach and performing the global minimization showed that both Langmuir and Sips models showed an adequate description of the acid, basic and reactive dyes adsorption. [ABSTRACT FROM AUTHOR]

The extent of bioregeneration of granular activated carbon (GAC) loaded with binary mixture of phenol and 4-chlorophenol (4-CP) was investigated. Batch studies were conducted at (i) different initial phenol and 4-CP loading concentrations and (ii) various GAC dosages to examine the effects of different ratios of phenol to 4-CP adsorbed (to) on bioregeneration efficiency. The bioregeneration efficiency was higher when thetoratio was higher due to lower adsorption irreversibility of phenol. Increasing the GAC dosage under saturation condition at the same initial conditions only marginally improved the bioregeneration efficiency. The characteristics of the adsorption process (i.e. the irreversibility of adsorption) of each adsorbate are an important factor influencing the extent of bioregeneration in binary component-loaded GAC. [ABSTRACT FROM PUBLISHER]

The effects of initial cresol loading concentration, granular activated carbon (GAC) dosage, dry biomass density biomass immobilization matrix and chemical structure of cresol isomers on the bioregeneration efficiency of GAC loaded with o -, m - and p -cresol using polyurethane (PU) and polyvinyl alcohol (PVA) immobilized biomasses, respectively, were investigated. The results revealed higher bioregeneration efficiencies of cresol-loaded GAC when GAC was saturated with cresol. The dominating factor determining the bioregeneration efficiency was the distribution of cresol molecules within the micro-, meso- and macropores of GAC. Bioregeneration efficiency of cresol-loaded GAC could be enhanced by increasing the dry biomass density from 0.32 to 1.3 g/100 mL in PU-immobilized biomass beads. PU-immobilized biomass was found to yield higher bioregeneration efficiency than PVA-immobilized biomass. Among the cresol isomer-loaded GACs, bioregeneration efficiency of o -cresol-loaded GAC was the lowest due to more irreversibility of adsorbed o -cresol than m - and p -cresol. [ABSTRACT FROM AUTHOR]

Studies on the development of alternative adsorbent using rice husk have been extensively reported. However, relatively little has been reported on the comparative adsorptive removal of phenolic compounds using rice husk activated with different methods as well as their bioregeneration potential and reusability. This study aimed to investigate the adsorption capacities of rice husk activated with nitric acid (ARH), ethylenediamine (MRH), and potassium hydroxide (KRH), respectively, for 4-chlorophenol (4-CP) and 2,4-chlorophenol (2,4-DCP) in comparison to powdered activated carbon (PAC) and the bioregeneration efficiencies and reusability of chlorophenol-loaded activated rice husks. For both cases using 4-CP and 2,4-DCP as adsorbates, the adsorption capacities were found in the order of KRH > PAC > ARH > MRH. Despite the much lower abiotic desorption efficiencies, the bioregeneration efficiencies were found comparable for all the adsorbents (>80% for the first cycle except for 2,4-DCP-loaded KRH). The total capacity losses for all the bioregenerated adsorbents were observed to increase with increasing number of cycles of use. In terms of the efficacy, KRH showed the highest accumulated amount of 4-CP and 2,4-DCP removed followed by PAC, ARH, and MRH. Amongst the adsorbents, KRH was found to be the most efficient adsorbent to remove 4-CP and 2,4-DCP, respectively, based on the accumulated amount of adsorbate after successive bioregeneration. [ABSTRACT FROM AUTHOR]

Anaerobic digestion (AD) is widely used for the treatment of livestock waste because the biogas produced can be utilized as energy source. Further treatment of AD effluents is often required for total nitrogen (TN) removal, which is typically carried out using biological nitrogen removal processes. However, the high free ammonia (FA) concentrations present in AD effluents can inhibit nitrification processes. This research tested a sequencing batch reactor (SBR) amended with particulate chabazite (chabazite-SBR) for removal of TN from anaerobically digested swine waste centrate. In the chabazite-SBR, zeolitic material with a high ion exchange (IX) capacity for NH4+ is used to ease nitrification inhibition. Once nitrification is complete, an external organic electron donor is supplied during an anoxic stage to promote denitrification. An overall TN removal efficiency of 84% was achieved in a laboratory-scale chabazite-SBR, with specific nitrification and denitrification rates of 0.43 and 1.49 mg-N/(g-VSS ·h), respectively. Simultaneous nitrification-denitrification was observed in the biofilm surrounding the chabazite particles, resulting in improved TN removal and alkalinity control. TN and chemical oxygen demand (COD) removal were dependent on external organic carbon dose, with a COD/N ratio of 3.2 g-COD/g-N resulting in both high TN (97%) and COD (51%) removal efficiencies. Over the 40 cycles of operation, the IX stage was able to reduce FA concentrations to below the inhibitory level for nitrification. No loss in IX efficiency was observed, and no fresh zeolite was added to the reactor. The chabazite-SBR is a promising technology for treatment of high NH4+ strength wastewaters. [ABSTRACT FROM AUTHOR]

In Biological Activated Carbon (BAC) systems, persistent organic pollutants can be removed through a combination of adsorption, desorption and biodegradation. These processes might be affected by the presence of other organics, especially by the more abundant easily-biodegradable organics, like acetate. In this research these relations are quantified for the removal of the persistent pharmaceutical metoprolol. Acetate did not affect the adsorption and desorption of metoprolol, but it did greatly enhance the metoprolol biodegradation. At least part of the BAC biomass growing on acetate was also able to metabolise metoprolol, although metoprolol was only converted after the acetate was depleted. The presence of easily-degradable organics like acetate in the feeding water is therefore beneficial for the removal of metoprolol in BAC systems. The isotherms obtained from metoprolol adsorption and desorption experiments showed that BAC systems are subject to hysteresis; for AC bioregeneration to take place the microbial biomass has to reduce the concentration at the AC-biomass interface 2.7 times compared to the concentration at which the carbon was being loaded. However, given the threshold concentration of the MET degrading microorganisms (<0.08 μg/L) versus the average influent concentration (1.3 μg/L), bioregeneration is feasible. [ABSTRACT FROM AUTHOR]

One of the main sources of air pollution is the combustion of fuels by various thermal and power plants, transport facilities, and metallurgical plants. Main components of industrial gases that pollute air are carbon oxides, nitrogen oxides, sulphur oxides and hydrogen sulphide. Sulphur has received a more attention than any other contaminant, because the sulphur released into the atmosphere in the form of sulphur dioxide or hydrogen sulphide is a precursor of the acid rain formation. To meet environmental emission regulations, sulphur and other contaminant species released during the gasification of coal must be removed from the fuel gas stream. The removal of contaminat at high temperatures is referred to as hot-gas cleanup in general and hot-gas desulphurization in particular when sulphur species are the primary contaminants to be remove. In recent years, zinc ferrite is the leading candidate for hot-gas desulphurization, capable of removing sulphur-containing species from coal gas at gasifier exit temperatures. It can also be of being regenerated for a continuous use. The conventional methods of the regeneration of sulphurized sorbents are based on oxidizing pyrolysis of sulphides or on the pressure leaching of sulphides in the water environment at high temperatures. The first results of the experiments using the biological-chemical leaching, as a new way of regeneration of sulphurized sorbent based on zinc ferrite, are presented in this paper. The results show that the biological-chemical leaching leads to the removal of sulphides layers (á-ZnS, â-ZnS) from the surface of the sorbent at room temperature. The biological-chemical leaching process results in the increase of the active surface area of the regenerated sorbent.

• Sulfate-reducing bacteria used for bioregeneration of commercial anion exchange resin. • Successful bioregeneration with both pure and mixed SRB cultures. • In batch mode, bioregeneration efficiency increased with contact time. • In column mode, almost complete bioregeneration of resin capacity. Ion exchange technology removes ionic compounds from waters effectively but treatment of the spent regenerant is expensive. The bioregeneration of sulfate-laden strong base anion exchange resin was successfully tested using both pure and mixed sulfate-reducing bacterial cultures. The resin was first used for removal of sulfate from neutral (pH 6.7 ± 0.5) synthetic sodium sulfate solutions, after which the spent resin was regenerated by incubating with a viable sulfate-reducing bacterial culture in batch and column modes. In the batch bioregeneration tests, the achieved bioregeneration was 36–95% of the original capacity of the fresh resin (112 mg SO 4 2−/g) and it increased with regeneration time (1–14 days). The capacity achieved in the column tests during 24 hours of bioregeneration was 107 mg SO 4 2−/g after the first regeneration cycle. During the bioregeneration, sulfate was mainly reduced by the sulfate-reducing bacteria (approx. 60%), but part of it was only detached from the resins (approx. 30%). The resin-attached sulfate was most likely replaced with ions present in the liquid sulfate-reducing bacterial culture (e.g., HCO 3 −, HS−, and Cl−). During the subsequent exhaustion cycles with the bioregenerated resin, the pH of the treated sodium sulfate solution increased from the original 6.7 ± 0.5 to around 9. The study showed that biological sulfate reduction could be used for sulfate removal in combination with ion exchange, and that the exhausted ion exchange resins could be regenerated using a liquid sulfate-reducing bacterial culture without producing any brine. [Display omitted] [ABSTRACT FROM AUTHOR]

The study aims to: (1) investigate the adsorption of powdered activated carbon (PAC) and granular activated carbon (GAC) for phenol, indole, and their mixtures, respectively, and (2) determine the bioregeneration efficiency and reusability of PAC loaded with phenol, indole, and their mixtures. The results showed that phenol was easier to be adsorbed than indole. The adsorption using PAC was obviously better than GAC. The considerably higher bioregeneration efficiency of the phenol-loaded PAC as compared to that of indole-loaded PAC was probably due to the recalcitrant nature of indole. PAC exhibited much higher adsorption capacity for indole, especially in the presence of low concentration of phenol. Besides, phenol improved the biodegradation of indole and therefore enhanced the reusability of indole-loaded PAC. Therefore, powdered activated carbon technology (PACT) was appropriate for the treatment of similar wastewater. Within the PACT system, PAC preferentially adsorbed the recalcitrant indole while the relatively easily degradable phenol was utilized by the biomass. Besides, phenol enhanced the degradation of indole and the reusability of PAC, which resulted in a stable and efficient performance. [ABSTRACT FROM PUBLISHER]

The increasing use of highly-selective resins for the removal of anions from contaminated drinking water has increased the demand for these resins and increased the waste generated during the treatment process. The proof of concept for the extension of the use of these resins by use of multi-cycle exhaustion/bioregeneration has been demonstrated previously. To fully develop a process for the commercialization of this technology it is important to determine the effect of the temperature and salt concentration on the nitrate desorption rates to model chemical and biological processes. Results show pseudo-second order kinetic analysis explains the experimental data very well. The initial desorption rates were significantly different in different salt concentrations and temperature; higher and lower value for 6% and 2% salt, higher and lower value at 35 °C and 12 °C. The mean value of the equilibrium concentration at 12 °C was significantly lower than 23 °C and 35 °C with no effect of salt concentration on the temperature means. The results of this research provide much needed data of the kinetics as well as the typical equilibrium as such is a significant contribution to the overall design of systems for the reuse of highly selective resin in multi-cycle ion exchange processes without any further disinfection or cleaning procedures. [ABSTRACT FROM AUTHOR]

Ion-exchange (IX) is the most feasible technology for perchlorate removal from drinking water. Reuse of resins present challenges, however. Selective resins are non-regenerable, and are incinerated after one time use, while non-selective resins, when regenerable, produce a waste stream that contains high concentration of perchlorate that must be disposed of. A process to bioregenerate spent resin containing perchlorate with perchlorate-reducing bacteria (PRB) has been recently developed. In this research, potential mechanisms for bioregeneration of resin-attached perchlorate (RAP) were investigated. Batch bioregeneration experiments were performed using gel-type and macroporous-type resins. Various initial chloride concentrations and various resin bead sizes were used. The results of the bioregeneration experiments suggested that chloride, i.e. the product of perchlorate biodegradation, is more likely the desorbing agent of RAP; and increasing the concentration of chloride enhances the bioregeneration process. Both film and pore diffusion were found to be relevant with respect to the rate of perchlorate mass-transfer to the bulk liquid. Bioregeneration was found to be more effective for macroporous than for gel-type resins, especially in the case of macroporous resins with relatively small bead size in the presence of higher chloride concentration. [ABSTRACT FROM AUTHOR]

Ozone has been shown to be effective in the transformation of several chemicals of emerging concern that escape the wastewater treatment process, but there is concern whether toxic transformation products are formed. Two parallel biofilter columns with granular activated carbon (GAC) and filter sand following a pilot-scale ozone unit to treat secondary treated municipal wastewater were studied. Results show reduced wastewater genotoxicity following ozonation and further reduction following biofiltration. The BAC biofilter outperformed the sand biofilter in terms of reduction in both organics and genotoxicity. Biofilter performance correlated with biological indicators (dissolved oxygen reduction and effluentE. colicounts) but not with ATP bioactivity measurements. Limited bacterial (E. coli) regrowth was observed in treated effluent from both biofilters. [ABSTRACT FROM PUBLISHER]

Removal of TCE by Biological Powdered Activated Carbon (BPAC), inoculated with Burkholderia vietnamiensis G4 and fed with toluene as the growth substrate, was investigated in fed-batch mode reactors, focusing on the regeneration of Powdered Activated Carbon (PAC). Cell-only and PAC-only reactors were operated in parallel for comparison. BPAC, once acclimated, removed toluene and TCE faster than cell-only or PAC-only reactors, leaving the lowest residuals in the liquid. This was amplified when the substrate dose was elevated. Toluene competitively adsorbed into the BPAC, resulting in TCE desorption, which accelerated bioregeneration of the TCE-sorbed BPAC. The regenerated BPAC exerted a similar adsorption capacity to PAC and a similar biodegradation capability to virgin BPAC under the experimental conditions. An acclimation of cells on TCE was necessary before its degradation, which indicated that TCE cometabolism may not be a fortuitous reaction. When a bioactive zone is constructed with BPAC, it is expected that TCE in the groundwater will be adsorbed to the BPAC; then, the adsorbed TCE will be desorbed and cometabolized upon pulse injections of toluene. A portion of left-over toluene will be stored in the BPAC and utilized for later TCE cometabolization. [ABSTRACT FROM AUTHOR]

Highlights: [•] Mono-amine modified silica (MAMS) was used for the removal of azo dye. [•] Bioregeneration duration increased in decreasing dye-loaded MAMS particle size. [•] Bioregeneration of AO7-loaded MAMS decreased in decreasing particle size. [•] Acclimation without co-substrate was preferred for bioregeneration of spent MAMS. [Copyright &y& Elsevier]

Highlights: [•] Clinoptilolite sorption was studied with batch experiments and constructed wetlands. [•] Both sorption and nitrification were enhanced in wetlands with clinoptilolite. [•] Clinoptilolite can improve ammonia treatment performance in constructed wetlands. [ABSTRACT FROM AUTHOR]

Benzene, toluene, ethylbenzene, and xylenes (BTEX) are common groundwater pollutants. Biological activated carbon (BAC) treatment is attractive because BTEX species are well-adsorbed on activated carbon and also easily biodegraded in the adsorber. The inoculated activated carbon columns quickly became BAC systems; they removed most of the BTEX species present in the feed. Biodegradation was primarily responsible for the overall removal of the BAC systems, and the amounts of benzene, toluene, and o-xylene removed during the 2-week treatment period were all more than their respective isotherm capacities; 1,486, 1,463, 1,537, and 1,719 mg of benzene, toluene, ethylbenzene, and o-xylene were removed in the 2.5-g BAC systems versus the available adsorptive capacities of 174, 731, 1,515, and 895 mg, respectively. The stable BAC systems were resistant to the shock loadings of higher flow and concentration and consumed less than the expected amount of dissolved oxygen. Bioregeneration enabled the long-term treatment capability of the BAC systems for removing BTEX and other pollutants without periodic carbon replacement. The coal-based activated carbon (SC) was more desirable than the coconut-based activated carbon (YK) because of its lower cost and higher degree of bioregeneration. [ABSTRACT FROM AUTHOR]

Highlights: [•] Use of immobilized biomass-PAC for bioregeneration of phenol- and o-cresol loaded GAC. [•] Comparison of bioregeneration using immobilized and suspended biomasses. [•] Minimization of biomass colonization on immobilized biomass bioregenerated GAC. [•] Shortening of bioregeneration duration using immobilized biomass-PAC. [Copyright &y& Elsevier]

Highlights: [•] Bioregeneration of AO7-loaded MAMS in the absence of co-substrate. [•] Bioregeneration of AY9- and AR14-loaded MAMS in the presence of co-substrate. [•] Shortening of bioregeneration duration using higher acclimation concentration. [•] No effect on bioregeneration efficiency under different acclimation concentrations. [Copyright &y& Elsevier]

Highlights: [•] Bioregeneration of a phenol-preloaded hypercrosslinked polymeric resin was examined. [•] Concentration-gradient driving diffusion of the loaded phenol dominate the bioregeneration process. [•] The regenerated resin could be employed for multiple phenol adsorption. [ABSTRACT FROM AUTHOR]

Background Information on the effects of initial biomass concentration on bioregeneration rate and efficiency is lacking as many of the bioregeneration studies were conducted at constant initial biomass concentration. The objectives of this study are: (i) to develop kinetic models incorporating adsorption, desorption, biodegradation and the irreversibility of adsorption in describing the bioregeneration of granular activated carbon ( GAC) loaded with 4-chlorophenol (4- CP); and (ii) to investigate the effect of initial biomass concentration on the rate and efficiency of bioregeneration of 4- CP-loaded GAC in simultaneous adsorption and biodegradation processes. Results The bioregeneration model with Haldane biodegradation kinetics gave a better fit ( R2 > 0.956) than the model with first-order biodegradation kinetics ( R2 > 0.805) to the experimental data. Values of the rate constant of desorption generated from the models showed that there was no observed effect of varying biomass concentration on the bioregeneration rate. The efficiency study revealed no observed effect of varying biomass concentration on the bioregeneration efficiency provided there was no inhibition effect due to 4- CP. Conclusions Change in the initial biomass concentration had no observed effect on the bioregeneration rate and efficiency, if there was no inhibitory effect due to the substrate in the latter case. © 2012 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Utilization of agrowaste materials for the production of activated carbon, as an excellent adsorbent with large surface area, is well established industrially, for dephenolation of wastewater. In the present work, dried pods of Prosopis cineraria-a novel and low-cost agrowaste material-were used to prepare activated carbons by zinc chloride activation. Batch adsorption experiments were carried out to study the effects of various physicochemical parameters such as initial phenol concentration, adsorbent dose, initial solution pH, and temperature. Pseudo-first-order second-order and diffusion kinetic models were used to identify the possible mechanisms of such adsorption process. The Langmuir and Freundlich equations were used to analyze the adsorption equilibrium. Maximum removal efficiency of 86 % was obtained with 25 mg L of initial phenol concentration. The favorable pH for maximum phenol adsorption was 4.0. Freundlich equation represented the adsorption equilibrium data more ideally than the Langmuir. The maximum adsorption capacity obtained was 78.32 mg g at a temperature of 30 °C and 25 mg L initial phenol concentration. The adsorption was spontaneous and endothermic. The pseudo-second-order model, an indication of chemisorption mechanism, fitted the experimental data better than the pseudo-first-order Lagergren model. Regeneration of spent activated carbon was carried out using Pseudomonas putida MTCC 2252 as the phenol-degrading microorganism. Maximum regeneration up to 57.5 % was recorded, when loaded phenol concentration was 25 mg L. The data obtained in this study would be useful in designing and fabricating an efficient treatment plant for phenol-rich effluents. [ABSTRACT FROM AUTHOR]