Search

Urban areas face increasing pressures on water resources, necessitating innovative approaches to climate adaptation and water quality management. Nature-based Solutions (NbS) offer a sustainable pathway, yet their integration with existing infrastructure in urban settings remains occasional. This study presents a novel hybrid system—Sequential Sedimentation Biofiltration System (SSBS)—designed for stormwater treatment within confined urban spaces. The system was adjusted to the existing stormwater infrastructure by integrating a sedimentation tank (SED), three Permeable Reactive Barriers (PRBs), and a biofiltration zone (BIO). The SSBS was evaluated for its efficiency in removing nutrients and sediments, focusing on the performance of PRBs. Our findings showed limited sediment removal in SED and PRBs due to spatial constraints and a high Hydraulic Loading Rate (HLR = 1.31 m/d), achieving an average of 13.6% Total Suspended Solids (TSS) removal. However, PRBs demonstrated effective removal of ammonium (43.4%) and phosphate (59.3%), potentially due to sorption and biofilm activity, with dominant microbial communities including Proteobacteria, Bacteroidetes, and nutrient-transforming taxa such as Nitrospirae. Interestingly, PRBs increased nitrite levels (57.1%) but did not significantly impact nitrate, chloride, or TSS. The BIO zone further enhanced nutrient retention (56% PO 4 –P) and served as a sink for TSS (52%). This study underscores the potential for integrating traditional urban infrastructure with NbS in a sequential stormwater treatment system, demonstrating its effectiveness in space-constrained urban environments. [Display omitted] • A hybrid SSBS was implemented for stormwater treatment within an urban area. • The system effectively removed TSS, N, and P despite space constraints. • Permeable Reactive Barriers maintained their efficiency after 110 days of operation. • Biofilms with potential nutrient-cycling bacteria developed on sorption materials. [ABSTRACT FROM AUTHOR]

Conventional filtration practices typically operate with a pre-chlorination step for the disinfection of harmful pathogens. Without pre-chlorination, biofilters will develop, which are capable of reducing the formation of disinfection by-products (DBPs) and can decrease bacterial regrowth in the distribution system. However, concerns, particularly in North America, still exist with the implementation of biofiltration and there is a lack of side-by-side comparisons with pre-chlorinated filters in literature. A pilot scale study comparing conventional and biological dual media anthracite/sand filters was conducted to assess their performance under warm (15–25 °C) and cold (0–5 °C) water conditions. The filters were operated under various backwash conditions, including the addition of air scour and extended terminal subfluidization wash (ETSW). The biofilter effluent exhibited significantly lower (p < 0.05) DBP formations under both temperature conditions, with trihalomethanes (TTHM) and haloacetic acids (HAA9) concentrations 33–35% and 36–46% lower than the conventional filters, respectively. There was no significant difference when it came to particle passage or turbidity during ripening for both filter types, however the conventional filter proved to be more vulnerable to changes in terms of particles between backwashes. The biofilter exhibited greater average headloss development by 8.8 cm and 4.5 cm under warm and cold water conditions, respectively. Biofilter headloss was found to be minimized by 18% when applying air scour and ETSW during backwash compared to water only, under warm temperature conditions. • The biofilter effluent had significantly lower DBPs than the conventional filter. • DOC removals in the biofilter remained consistent under cold temperatures. • The conventional filter showed higher variability in particle release. • Air scour + ETSW improved headloss development in both filters. • The conventional filter outperformed the biofilter in terms of headloss control. [ABSTRACT FROM AUTHOR]

Ozone (O 3) treatment is an effective strategy in maintaining high efficiency and control of biomass accumulation in gas phase biofiltration. However, little is known about the long-term impact of O 3 on the microbial communities. In the present study, two biofilters treating gaseous ethyl acetate were operated continuously for 230 days with inlet loads up to 180 g m−3∙h−1. A biofilter operated under continuous O 3 addition (90 ppb v) yielded consistently higher removal efficiency (RE) and elimination capacity (EC) compared to the control system. After 120 days of operation, a lower biomass content accompanied by a pH of 1.5 was observed in the ozonated biofilter, which was 2 units lower compared to the control reactor. Both reactors developed a distinct microbial community composition over the course of 230 days. The bacterial community was dominated in both biofilters by Beijerinckia and Gluconacetobacter , while Rhinocladiella similis , Trichosporon veenhuissi and Exophilia oligosperma were abundant in the fungal community. These findings suggest that ozonation of the biofiltration systems not only reduced clogging, but also contributed to the selection of biomass suitable for degradation of ethyl acetate. • Continuous higher removal efficiency in the ozonated biofiltration system. • Biofiltration with ozone treatment resulted in more acidic operating conditions. • Distinct bacterial and fungal profile observed between ozonated and control system. • Ozonation contributed to biomass selection for ethyl acetate degradation. [ABSTRACT FROM AUTHOR]

The fraction of pollutant converted to CO 2 versus biomass in biofiltration influences the process efficacy and the lifetime of the bed due to pressure drop increases. This work determined the relative quantitative importance and potential interactions between three critical environmental parameters: toluene concentration (Tol), matric potential (ψ) and temperature (T) on % CO 2 , elimination capacity (EC) and the production rate of non-CO 2 products. These parameters are the most variable in typical biofilter operation. The data was fit to a non-linear model of the form y = a (T o l) b T c ψ d . A rigorous carbon balance (100.5 ± 7.0%) tracked the fate of degraded toluene as CO 2 and non-CO 2 carbon endpoints. The % CO 2 mineralization varied from (34–91%) with environmental parameters: temperature (20–40 °C), matric potential, (−10 to −100 cm H2O) and residual toluene, (20–180 ppm). The highest conversion to CO 2 was at the wettest conditions (−10 cm H2O) and lowest residual toluene concentration (18 ppm). Matric potential had twice the impact of toluene concentration on % CO 2 , while temperature had less impact. The elimination capacity varied from 11 to 50 g C ⋅m−3h−1 and was highest at 40 °C, the wettest conditions with limited impact by toluene concentrations. Temperature increased the EC and non-CO 2 production rates strongly while matric potential and toluene concentration had less influence (4x - 10x less). This study illustrated the quantitative significance and simultaneous interaction between critical environmental parameters on carbon endpoints and biofilter performance. This kind of multivariable parameter study provides valuable insights which can address performance and clogging issues in biofilters. Image 1 • Robust carbon balance closure accounting for CO 2 and non-CO 2 carbon endpoints(EPS). • Impact of environmental parameters on %CO 2 , EC and non-CO 2 fraction. • Matric potential had a greater impact (2x) on %CO 2 than toluene concentration. • Temperature strongly influenced EC and non-CO 2 production rates. • Multivariable investigations are key to decipher impact on vital response variables. [ABSTRACT FROM AUTHOR]

Methane is one of the most important greenhouse gases emitted from natural and human activities. It is scarcely soluble in water; thus, it has a low bioavailability for microorganisms able to degrade it. In this work, the capacity of the fungus Fusarium solani to improve the solubility of methane in water and to biodegrade methane was assayed. Experiments were performed in microcosms with vermiculite as solid support and mineral media, at temperatures between 20 and 35 °C and water activities between 0.9 and 0.95, using pure cultures of F. solani and a methanotrophic consortium (Methylomicrobium album and Methylocystis sp) as a control. Methane was the only carbon and energy source. Results indicate that using thermally inactivated biomass of F. solani, decreases the partition coefficient of methane in water up to two orders of magnitude. Moreover, F. solani can degrade methane, in fact at 35 °C and the highest water activity, the methane degradation rate attained by F. solani was 300 mg m−3 h−1, identical to the biodegradation rate achieved by the consortium of methanotrophic bacteria. Image 1 • Fusarium solani thermally inactivated biomass promotes methane solubilization. • F. solani was able to degrade methane in closed systems. • Fungal methane degradation rate was comparable with methanotrophic bacteria. • Bacterial-like particulate (or soluble) methane monooxygenases were not found. • Initial methane attack could be catalyzed by a cytochrome P450 in F. solani. [ABSTRACT FROM AUTHOR]

Abstract This work investigates the enhancement in the removal efficiency of isopropyl alcohol (IPA) vapor by a hollow trickling-bed microbial fuel cell (TB-MFC) that can be achieved by certain modifications. The effects of shock load and shutdown on the performance of TB-MFC were evaluated. When organic loading (OL) of IPA was approximately 22.1–88.5 g m−3 h−1, the removal efficiency of 85.1–93.8% of the TB-MFC was achieved. With an empty bed residence time (EBRT) of 60 s and an inlet IPA concentration of 4.42 g m−3, the TB-MFC achieved its maximum EC of 150 g m−3 h−1, which was 1.7–4 times higher than reported for conventional biofiltration technology. A maximum closed-circuit voltage (CCV) of 173 mV and maximum power density (PD max) of 53.2 mW m−3 were obtained under optimal conditions (IPA concentration = 0.73 g m−3; EBRT = 60 s). Short-term shutdown (seven days) did not cause significant changes in EC, CCV, and PD max of the TB-MFC. This investigation establishes the feasibility of using a trickling-bed MFC to substantially increase the removal of IPA and handle shock-load and shut-down events. To increase EC and power output, this laboratory-scale TB-MFC could easily be scaled up by stacking anodes, and has great potential for future application in the field in various industries. Graphical abstract Image 107532 Highlights • A trickling-bed microbial fuel cell (MFC) was to treat isopropanol (IPA). • Coke grain, a packing material, was stacked as anodes in the trickling-bed MFC. • Electricity was continuously produced with high IPA removal. • The trickling-bed MFC performed well during its transient operation. • A 7-day shutdown had no effect on the performance of the trickling-bed MFC. [ABSTRACT FROM AUTHOR]

Manipulating the methanotroph (MOB) composition and microbial diversity is a promising strategy to optimize the methane (CH 4) biofiltration efficiency of an engineered landfill cover soil (LCS) system. Inoculating soil with exogenous MOB-rich bacteria and amending soil with biochar show strong manipulating potential, but how the two stimuli interactively shape the microbial community structure and diversity has not been clarified. Therefore, three types of soils with active CH 4 activities, including paddy soil, river wetland soil, and LCS were selected for enriching MOB-dominated communities (abbreviated as B_PS, B_RWS, and B_LCS, respectively). They were then inoculated to LCS which was amended with two distinct biochar. Besides the aerobic CH 4 oxidation efficiencies, the evolution of the three microbial communities during the MOB enrichment processes and their colonization in two-biochar amended LCS were obtained. During the MOB enriching, a lag phase in CH 4 consumption was observed merely for B_LCS. Type II MOB Methylocystis was the primary MOB for both B_PS and B_LCS; while type I MOB dominated for B_RWS and the major species were altered by gas concentrations. Compared to biochar, a more critical role was demonstrated for the bacteria inoculation in determining the community diversity and function of LCS. Instead, biochar modified the community structures by mainly stimulating the dominant MOB but could induce stochastic processes in community assembly, possibly related to its inorganic nutrients. Particularly, combined with biochar advantages, the paddy soil-derived bacteria consortiums with diverse MOB species demonstrated the potent adaption to LCS niches, not only retaining the high CH 4 -oxidizing capacities but also shaping a community structure with more diverse soil function. The results provided new insights into the optimization of an engineered CH 4 -mitigation soil system by manipulating the soil microbiomes with the cooperation of exogenous bacteria and biochar. [Display omitted] • Exogenous MOB-rich bacteria dominate the microbial community assembly of LCS. • B_PS endows LCS with active CH 4 oxidation and more diverse soil function. • Biochar modifies microbial community structure by stimulating the dominant MOB. • Biochar could induce stochastic assembly of bacteria when B_PS was inoculated. [ABSTRACT FROM AUTHOR]

Abstract The variations of disinfection byproduct (DBP) precursors and DBPs-associated toxic potencies were evaluated by ozonation, followed by a up-flow biological activated carbon (O 3 /UBAC) filter treating two reconstituted water samples, featuring either high bromide (105.3 μg/L) or dissolved organic nitrogen (0.73 mg N/L) concentration, respectively. Ozonation contributed to ∼20% decrease in dissolved organic carbon (DOC) concentration at a dosage of 0.7 mg of O 3 /mg of DOC, but no further reduction in DOC level was observed with an increased dose of 1.0 mg of O 3 /mg of DOC. When chlorine or preformed monochloramine was used as a disinfectant, UBAC process led to ∼40% reduction in the sum of detected DBP formation potential (FP) due to the removal of precursors at a feasible empty bed contact time of 15 min. The integrated effect of ozonation and UBAC biofiltration decreased the sum of DBP FP by ∼50% including halonitromethanes (THNMs), N-nitrosamines (NAs), and bromate, which increased in the effluent of ozonation. Chloramination produced less DBPs by weight as well as DBPs-associated additive toxic potencies than chlorination. The reduction in additive toxic potencies was generally lower than the removal efficiency of DBP FP after chlor(am)ination of treated waters by O 3 /UBAC, indicating that the removal of DBPs-associated additive toxic potencies should be focused to better understand on the residual risk to public health in controlling DBP precursors. Graphical abstract Image 1 Highlights • O 3 /UBAC lowered the sum of DBP FP by 49.8 %–57.5% at 0.7 mg of O 3 /mg of DOC and 15 min EBCT. • Toxic potencies' reduction was lower than that of DBP FP. • DBPs and even their toxicity were less formed in chloramination than chlorination. • Ozonation increased toxic potencies partly due to the formation of brominated DBPs. [ABSTRACT FROM AUTHOR]

Abstract The objective of this pilot-scale study was to investigate the effectiveness of incorporating ozone (O 3) and advanced oxidation (hydrogen peroxide/ozone: H 2 O 2 /O 3) in combination with biofiltration for taste and odour control, organic carbon removal, and disinfection byproduct (DBP) precursor reduction. Implementation of O 3 and H 2 O 2 /O 3 with and without biofiltration was investigated at pilot-scale in terms of geosmin, 2-methylisoborneol (MIB), and DBP precursor removal efficiency. Two media types (granular activated carbon and anthracite) were compared in conjunction with investigating the impact of pre-oxidation with O 3 (2 mg/L) and varying H 2 O 2 /O 3 mass ratios (0.1, 0.2, 0.35, and 0.5 mg/mg). When O 3 preceded biologically active carbon (BAC) or biologically active anthracite, geosmin removals of 80% and 81%, respectively, were observed at 10 °C; this increased to 89% and 90%, respectively, at 16 °C. Optimal MIB removal (67%) was achieved with 0.1 H 2 O 2 /O 3 (mg/mg) in combination with BAC at 16 °C. In general, geosmin proved to be more amenable to biodegradation than MIB. BAC without pre-oxidation removed 87% geosmin and 85% MIB, at 22 °C. MIB removals decreased to 60% and 46%, respectively at 16 °C and 10 °C. The application of 0.2 H 2 O 2 /O 3 (mg/mg) prior to BAC provided treatment which effectively removed geosmin and MIB. However, in terms of DBP precursor reduction, there was no beneficial impact of H 2 O 2 addition on trihalomethane or haloacetic acid formation potentials. Highlights • BAC alone may serve as a suitable treatment technology for T&O control at warmer temperatures. • Biologically activated anthracite outperformed non-biological anthracite in removing both geosmin & MIB. • O 3 efficiency and BAC biodegradation rates significantly decreased in cold water conditions. • H 2 O 2 /O 3 advanced oxidation improved MIB removal in cold water conditions. • Biopolymers were observed to preferentially react with $OH rather than O 3. [ABSTRACT FROM AUTHOR]

Abstract Although granular activated carbon (GAC) has been broadly applied in ozone-biologically activated carbon filtration (O 3 /BAC) systems for potable reuse of municipal wastewater, the mechanisms of various pollutant removal remain largely unknown as the regenerated GAC develops microbial populations resulting in biofiltration but loses significant adsorption capacity as it becomes spent GAC. Therefore, pilot-scale parallel performance comparisons of spent and regenerated GAC, along with a range of pre-oxidant ozone doses, were used to shed light on the mechanisms responsible for the removal of various types of treatment byproduct precursors and trace organic compounds. It was confirmed from this pilot-study that ozone alone can effectively degrade chlorinated trihalomethane (THM) and haloacetic acid (HAA) precursors, chloramine-reactive N-nitrosodimethylamine (NDMA) precursors, and 29 PPCPs. In contrast, biodegradation by microbial population on spent or regenerated GAC can remove NDMA and 22 PPCPs, while the adsorption by regenerated GAC can remove chlorinated THM and HAA precursors, PFAS, flame retardants, and 27 PPCPs. The results of this pilot study are intended to provide those interested in potable reuse with an example of the simultaneous removal capabilities and mechanisms that can be anticipated for treating a complex mixture of organics present in real municipal wastewater effluent. Highlights • Roles of spent and regenerated GAC were for the first time compared. • Pathways for the removal of a wide spectrum of compounds were identified. • Biodegradation can remove NDMA and 22 PPCPs. • Adsorption can remove THM and HAA precursors, PFAS, flame retardants, and 27 PPCPs. • Ozone can remove THM, HAA, chloramine-reactive NDMA precursors, and 29 PPCPs. [ABSTRACT FROM AUTHOR]

Corbicula fluminea, an Asian clam, is one of the worst invasive species in Europe that can survive in very adverse environmental conditions. Despite its negative impacts, the species also has the capacity to bioaccumulate heavy metals, contaminants and can be exploited for wastewater treatment purposes. The capacity of the Asian clam to remove Escherichia coli, used as fecal contamination indicator, was analyzed. Conventional wastewater treatment plants are not suitable to remove bacteria, thus resulting in treated municipal wastewater with high bacterial loads. E. coli clearance rate was analyzed as function of the number of clams. The bivalves can remove bacteria until concentrations below the detection limit in about 6 h. The adsorption on the clam shells’ and bioaccumulation on the soft tissues were also analyzed. The depuration of clams along 48 h were analyzed revealing that no bacteria was detected in the water. Thus, these results suggest that Asian clam can bioprocess E. coli . On the other hand, results obtained by this methodology were compared with ozonation and photocatalytic oxidation using TiO 2 , Ag, Au, Pd-TiO 2 . In all treatments it was possible to achieve concentrations of E. coli below the detection limit. However, photocatalytic oxidation demands about 4700 folds more energy than ozonation, besides the costs associated with catalysts. Comparing complexity of ozonation with biofiltration, this study suggests that application of biofiltration using C. fluminea can be a suitable solution to minimize the presence of bacteria in wastewater, reducing environmental and economic impacts. [ABSTRACT FROM AUTHOR]

The purpose of this research was to investigate the impacts of ozone dose and empty bed contact time (EBCT) in ozone-biofiltration systems on disinfection byproduct (DBP) formation potential. The data were used to evaluate the possibility of using DBP formation potential as an alternative guideline for total organic carbon (TOC) removal in potable reuse applications. A pilot-scale ozone-biofiltration system was operated with O 3 /TOC ratios ranging from 0.1 to 2.25 and EBCTs ranging from 2 to 20 min. The biofiltration columns contained anthracite or biological activated carbon (BAC). Bench-scale chlorination was performed using the uniform formation conditions (UFC) approach, and quenched samples were analyzed for total trihalomethanes (TTHMs) and regulated haloacetic acids (HAA5s). The data demonstrated that ozone-biofiltration achieved TOC removals ranging from ∼10 to 30%, depending on operational conditions, but biofiltration without ozone generally achieved <10% TOC removal. UFC testing demonstrated that ozone alone was efficient in transforming bulk organic matter and reducing DBP formation potential by 10–30%. The synergistic combination of ozone and biofiltration achieved average overall reductions in TTHM and HAA5 formation potential of 26% and 51%, respectively. Finally, a maximum TOC concentration of 2.0 mg/L was identified as a recommended treatment target for reliable compliance with TTHM and HAA5 regulations for potable reuse systems in the United States. [ABSTRACT FROM AUTHOR]

Foul odors comprise generally a complex mixture of molecules, where reduced sulfur compounds play a key role due to their toxicity and low odor threshold. Previous reports on treating mixtures of sulfur compounds in single biofilters showed that hydrogen sulfide (H 2 S) interferes with the removal and degradation of other sulfur compounds. In this study, hydrogen sulfide (H 2 S) and dimethyl disulfide (DMDS) were fed to an alkaline biotrickling filter (ABTF) at pH 10, to evaluate the simultaneous removal of inorganic and organic sulfur compounds in a single, basic-pH system. The H 2 S-DMDS mixture was treated for more than 200 days, with a gas residence time of 40 s, attaining elimination capacities of 86 g DMDS m −3 h −1 and 17 g H2S m −3 h −1 and removal efficiencies close to 100%. Conversion of H 2 S and DMDS to sulfate was generally above 70%. Consumption of sulfide and formaldehyde was verified by respirometry, suggesting the coexistence of both methylotrophic and chemoautotrophic breakdown pathways by the immobilized alkaliphilic biomass. The molecular biology analysis showed that the long-term acclimation of the ABTF led to a great variety of bacteria, predominated by Thioalkalivibrio species, while fungal community was notoriously less diverse and dominated by Fusarium species. [ABSTRACT FROM AUTHOR]

Impacts of ozonation alone as well as an advanced oxidation process of ozone plus hydrogen peroxide (H 2 O 2 + O 3 ) on organic matter prior to and following biofiltration were studied at pilot-scale. Three biofilters were operated in parallel to assess the effects of varying pre-treatment types and dosages. Conventionally treated water (coagulation/flocculation/sedimentation) was fed to one control biofilter, while the remaining two received water with varying applied doses of O 3 or H 2 O 2 + O 3 . Changes in organic matter were characterized using parallel factors analysis (PARAFAC) and fluorescence peak shifts. Intensities of all PARAFAC components were reduced by pre-oxidation, however, individual humic-like components were observed to be impacted to varying degrees upon exposure to O 3 or H 2 O 2 + O 3 . While the control biofilter uniformly reduced fluorescence of all PARAFAC components, three of the humic-like components were produced by biofiltration only when pre-oxidation was applied. A fluorescence red shift, which occurred with the application of O 3 or H 2 O 2 + O 3 , was attributed to a relative increase in carbonyl-containing components based on previously reported results. A subsequent blue shift in fluorescence caused by biofiltration which received pre-oxidized water indicated that biological treatment readily utilized organics produced by pre-oxidation. The results provide an understanding as to the impacts of organic matter character and pre-oxidation on biofiltration efficiency for organic matter removal. [ABSTRACT FROM AUTHOR]

A pilot study employing two parallel trains of two-stage biofiltration, i.e., a sand/anthracite (SA) biofilter followed by a biologically-active granular activated carbon (GAC) contactor, was conducted to test the efficiency, feasibility and stability of biofiltration for removing natural organic matter (NOM) after coagulation in a drinking water treatment plant. Results showed the biofiltration process could effectively remove turbidity (<0.1 NTU in all effluents) and NOM (>24% of dissolved organic carbon (DOC), >57% of UV 254 , and >44% of SUVA 254 ), where the SA biofilters showed a strong capacity for turbidity removal, while the GAC contactors played the dominant role in NOM removal. The vertical profile of water quality in the GAC contactors indicated the middle-upper portion was the critical zone for the removal of NOM, where relatively higher adsorption and enhanced biological removal were afforded. Fluorescence excitation-emission matrix (EEM) analysis of NOM showed that the GAC contactors effectively decreased the content of humic-like component, while protein-like component was refractory for the biofiltration process. Nutrients (NH 4 -N and PO 4 -P) supplementation applied upstream of one of the two-stage biofiltration trains (called engineered biofiltration) stimulated the growth of microorganisms, and showed a modest effect on promoting the biological removal of small non-aromatic compositions in NOM. Redundancy analysis (RDA) indicated influent UV 254 was the most explanatory water quality parameter for GAC contactors’ treatment performance, and a high load of UV 254 would result in significantly reduced removals of UV 254 and SUVA 254 . [ABSTRACT FROM AUTHOR]

Previous lab-scale studies demonstrated that stimulating the indigenous soil microbial community of groundwater recharge systems by manipulating the availability of biodegradable organic carbon (BDOC) and establishing sequential redox conditions in the subsurface resulted in enhanced removal of compounds with redox-dependent removal behavior such as trace organic chemicals. The aim of this study is to advance this concept from laboratory to full-scale application by introducing sequential managed aquifer recharge technology (SMART). To validate the concept of SMART, a full-scale managed aquifer recharge (MAR) facility in Colorado was studied for three years that featured the proposed sequential configuration: A short riverbank filtration passage followed by subsequent re-aeration and artificial recharge and recovery. Our findings demonstrate that sequential subsurface treatment zones characterized by carbon-rich (>3 mg/L BDOC) to carbon-depleted (≤1 mg/L BDOC) and predominant oxic redox conditions can be established at full-scale MAR facilities adopting the SMART concept. The sequential configuration resulted in substantially improved trace organic chemical removal (i.e. higher biodegradation rate coefficients) for moderately biodegradable compounds compared to conventional MAR systems with extended travel times in an anoxic aquifer. Furthermore, sorption batch experiments with clay materials dispersed in the subsurface implied that sorptive processes might also play a role in the attenuation and retardation of chlorinated flame retardants during MAR. Hence, understanding key factors controlling trace organic chemical removal performance during SMART allows for systems to be engineered for optimal efficiency, resulting in improved removal of constituents at shorter subsurface travel times and a potentially reduced physical footprint of MAR installations. [ABSTRACT FROM AUTHOR]

The application of fluorescence spectroscopy to monitor natural organic matter (NOM) reduction as a function of biofiltration performance was investigated. This study was conducted at pilot-scale where a conventional media filter was compared to six biofilters employing varying enhancement strategies. Overall reductions of NOM were identified by measuring dissolved organic carbon (DOC), and UV absorbance at 254 nm, as well as characterization of organic sub-fractions by liquid chromatography–organic carbon detection (LC-OCD) and parallel factors analysis (PARAFAC) of fluorescence excitation-emission matrices (FEEM). The biofilter using granular activated carbon media, with exhausted absorptive capacity, was found to provide the highest removal of all identified PARAFAC components. A microbial or processed humic-like component was found to be most amenable to biodegradation by biofilters and removal by conventional treatment. One refractory humic-like component, detectable only by FEEM-PARAFAC, was not well removed by biofiltration or conventional treatment. All biofilters removed protein-like material to a high degree relative to conventional treatment. The formation potential of two halogenated furanones, 3-chloro-4(dichloromethyl)-2(5H)-furanone (MX) and mucochloric acid (MCA), as well as overall treated water genotoxicity are also reported. Using the organic characterization results possible halogenated furanone and genotoxicity precursors are identified. Comparison of FEEM-PARAFAC and LC-OCD results revealed polysaccharides as potential MX/MCA precursors. [ABSTRACT FROM AUTHOR]

The biodegradability of three anion surfactants by biofilm microorganisms and the toxicity of the most readily biodegradable surfactant to biofilm microorganisms were examined using batch experiments, and the optimal concentration of SDS for enhanced removal of hexane was investigated using two biotrickling filters (BTFs) for comparison. Results showed that SDS could be biodegraded by microorganisms, and its toxicity to microorganisms within the experimental range was negligible. The best concentration of SDS in biofiltration of n-hexane was 0.1 CMC and the elimination capacity (EC) of 50.4 g m −3 h −1 was achieved at a fixed loading rate (LR) of 72 g m −3 h −1 . When an inlet concentration of n-hexane increased from 600 to 850 mg m −3 , the removal efficiency (RE) decreased from 67% to 41% by BTF2 (with SDS) and from 52% to 42% by BTF1 (without SDS). SDS could enhance hexane removal from 43% (BTF1) to 60% (BTF2) at gas empty-bed residence time (EBRT) of 7.5 s and an inlet concentration of 200 mg m −3 . [ABSTRACT FROM AUTHOR]

Nitrogen oxides (NO x), including nitrogen monoxide (NO) and nitrogen dioxide (NO 2), are among the most important global atmospheric pollutants because they have a negative impact on human respiratory health, animals, and the environment through the greenhouse effect and ozone layer destruction. NO x compounds are predominantly generated by anthropogenic activities, which involve combustion processes such as energy production, transportation, and industrial activities. The most widely used alternatives for NO x abatement on an industrial scale are selective catalytic and non-catalytic reductions; however, these alternatives have high costs when treating large air flows with low pollutant concentrations, and most of these methods generate residues that require further treatment. Therefore, biotechnologies that are normally used for wastewater treatment (based on nitrification, denitrification, anammox, microalgae, and combinations of these) are being investigated for flue gas treatment. Most of such investigations have focused on chemical absorption and biological reduction (CABR) systems using different equipment configurations, such as biofilters, rotating reactors, or membrane reactors. This review summarizes the current state of these biotechnologies available for NO x treatment, discusses and compares the use of different microorganisms, and analyzes the experimental performance of bioreactors used for NO x emission control, both at the laboratory scale and in industrial settings, to provide an overview of proven technical solutions and biotechnologies for NO x treatment. Additionally, a comparative assessment of the advantages and disadvantages is performed, and special challenges for biological technologies for NO abatement are presented. [Display omitted] • The slightly solubility of NO is a limitation for the implementation of biological treatments. • A mass transfer vector is necessary to improve NO solubility so that biological systems can be implemented at an industrial level. • CABR systems with F e (I I) E D T A 2 − are the most widely used biological treatments for the biological treatment of NO. • The maximum removal capacity reported is 103.22 g NO·m-3· h-1 with F e (I I) E D T A 2 − in a biotrickling filter. [ABSTRACT FROM AUTHOR]

Ochrobactrum tritici SCII24T bacteria is an environmental strain with high capacity to resist to arsenic (As) toxicity, which makes it able to grow in the presence of As(III). The inactivation of the two functional arsenite efflux pumps, ArsB and ACR3_1, resulted in the mutant O. tritici As5 exhibiting a high accumulation of arsenite. This work describes a method for the immobilization of the mutant cells O. tritici As5, on a commercial polymeric net after sputtered modified by the deposition of poly(tetrafluoroethylene) (PTFE) thin films, and demonstrates the capacity of immobilized cells to accumulate arsenic from solutions. Six different set of deposition parameters for PTFE thin films were developed and tested in vitro regarding their ability to immobilize the bacterial cells. The surface that exhibited a mild zeta potential value, hydrophobic characteristics, the lowest surface free energy but with a high polar component and the appropriate ratio of chemical reactive groups allowed cells to proliferate and to grow as a biofilm. These immobilized cells maintained their ability to accumulate the surrounding arsenite, making it a great arsenic biofilter to be used in bioremediation processes. [ABSTRACT FROM AUTHOR]

Despite several fungal strains have been retrieved from methane-containing environments, the actual capacity and role of fungi on methane abatement is still unclear. The batch biodegradation tests here performed demonstrated the capacity of Graphium sp. to co-metabolically biodegrade methane and methanol. Moreover, the performance and microbiology of a fungal-bacterial compost biofilter treating methane at concentrations of ∼2% was evaluated at empty bed residence times of 40 and 20 min under different irrigation rates. The daily addition of 200 mL of mineral medium resulted in elimination capacities of 36.6 ± 0.7 g m −3 h −1 and removal efficiencies of ≈90% at the lowest residence time. The indigenous fungal community of the compost was predominant in the final microbial population and outcompeted the inoculated Graphium sp. during biofilter operation. [ABSTRACT FROM AUTHOR]

The goal of this study was to investigate the potential of biofiltration to reduce the formation potential of disinfection byproducts (DBPs). Particularly, the work investigates the effect of the duration of the filter cycle on the formation potential of total trihalomethanes (TTHM) and five species of haloacetic acids (HAA5), dissolved oxygen (DO), organic carbon, nitrogen and total phosphorous concentrations along with biofilm coverage of the filter media and biomass viability of the attached cells. The study was conducted on a full-scale biologically active filter, with anthracite and sand media, at the Britannia water treatment plant (WTP), located in Ottawa, Ontario, Canada. The formation potential of both TTHMs and HAA5s decreased due to biofiltration. However the lowest formation potentials for both groups of DBPs and or their precursors were observed immediately following a backwash event. Hence, the highest percent removal of DBPs was observed during the early stages of the biofiltration cycle, which suggests that a higher frequency of backwashing will reduce the formation of DBPs. Variable pressure scanning electron microscopy (VPSEM) analysis shows that biofilm coverage of anthracite and sand media increases as the filtration cycle progressed, while biomass viability analysis demonstrates that the percentage of cells attached to the anthracite and sand media also increases as the filtration cycle progresses. These results suggest that the development and growth of biofilm on the filters increases the DPB formation potential. [ABSTRACT FROM AUTHOR]

Dimethylamine (DMA) is one of the important precursors of drinking water disinfection by-product N -nitrosodimethylamine (NDMA). Reduction of DMA to minimize the formation of carcinogenic NDMA in drinking water is of practical importance. Biodegradation plays a major role in elimination of DMA pollution in the environment, yet information on DMA removal by drinking water biofilter is still lacking. In this study, microcosms with different treatments were constructed to investigate the potential of DMA removal by a mixed culture enriched from a drinking water biofilter and the effects of carbon and nitrogen sources. DMA could be quickly mineralized by the enrichment culture. Amendment of a carbon source, instead of a nitrogen source, had a profound impact on DMA removal. A shift in bacterial community structure was observed with DMA biodegradation, affected by carbon and nitrogen sources. Proteobacteria was the predominant phylum group in DMA-degrading microcosms. Microorganisms from a variety of bacterial genera might be responsible for the rapid DMA mineralization. [ABSTRACT FROM AUTHOR]

Highlights: [•] Leca was studied with respect to sorption and chemisorption of H2S, MT and DMS. [•] DMS is not degraded but H2S and MT are removed with variable efficiency. [•] O2 is not necessary for chemisorption of H2S and MT. [•] Moisture content has an influence on removal of H2S and MT. [•] Dimethyl disulphide and dimethyl trisulphide are observed as gaseous by-products. [Copyright &y& Elsevier]

Highlights: [•] We studied the influence of different doses oxidants on changes in fulvic acids (FA). [•] Biological activity occurred by mineralization of small and biotransformation of big molecules. [•] Chlorine substituted into the FAs structure. [•] Chlorine dioxide oxidized FA stronger than chlorine and they became more biodegradable. [•] Ozonation is the most preferable process for pre-treatment of FAs before biofiltration. [Copyright &y& Elsevier]

Highlights: [•] Biofiltration of seawater amended with and biodegradable DOC is studied. [•] additions have not noticeable impact on NOM removal by biofiltration. [•] Biodegradable DOC additions are completely consumed by the biofilter. [Copyright &y& Elsevier]

Abstract: This paper presents a study on the chemical safety of the secondary effluent for reuse purposes and the requirement of advanced treatment. Water quality analysis was conducted regarding conventional chemical items, hazardous metals, trace organics and endocrine disrupting chemicals (EDCs). Generally speaking, the turbidity, COD, BOD, TN and TP of the secondary effluent can meet the Chinese standards for urban miscellaneous water reuse but higher colour is a problem. Further removal of BOD and TP may still be required if the water is reused for landscape and environmental purposes especially relating to recreation. In addition, Hazardous metals, trace organics and endocrine disrupting chemicals (EDCs) are not the main problems for water reuse. At the same time, several tertiary treatment processes were evaluated. The coagulation–filtration process is effective process for further improvement of the conventional water quality items and removal of hazardous metals but less effective in dealing with dissolved organic matter. The ultrafiltration (UF) can achieve almost complete removal of turbid matter while its ability to remove dissolved substances is limited. The ozone–biofiltration is the most effective for colour and organic removal but it can hardly remove the residual hazardous metals. Therefore, the selection of suitable process for different water quality is important for water use. [Copyright &y& Elsevier]

Abstract: Antibiotics and antibacterials are present in water bodies worldwide but little is known about their effects on the biological processes often used to treat water. In this research, the effect of antibiotics on bacterial activity and community structure was investigated by growing biofilms in the presence and absence of a mixture of three compounds (sulfamethoxazole, erythromycin, and ciprofloxacin) in a continuous-flow rotating annular bioreactor fed acetate as a carbon and energy source. Steady-state, surface area-normalized substrate utilization rates for all antibiotic treatments (all at 0.33μgL−1, all at 3.33μgL−1, and 1 at 3.33μgL−1 with the other 2 at 0.33μgL−1) were similar to the control experiments. Higher attached biomass levels in the experiments with ciprofloxacin at 3.33μgL−1 resulted in lower steady-state biomass-normalized substrate utilization rates in comparison to other runs. Microbial community analyses via automated ribosomal intergenic spacer analysis revealed significant shifts in community structure for the experiments dosed with the highest concentrations of ciprofloxacin, suggesting that the antibiotic selected for more resistant bacterial strains. The results of this research also suggest that mixtures of antibiotics at the sub-μgL−1 concentrations typically observed in surface waters are unlikely to affect biological process performance, at least in terms of the degradation of easily assimilable compounds. Conversely, changes to community structure and biofilm quantity might be expected with ciprofloxacin at μgL−1 concentrations. [Copyright &y& Elsevier]

Abstract: A 13.4L biofilter treating an off-gas stream supplemented with methanol under two different situations was studied in terms of MeOH removal efficiency, microbial ecology and odor removal. During Period 1 (P1) the reactor was packed with wood bark chips with no pH control, treating an off-gas resulting from the aerobic chamber of a membrane biological reactor treating sewage and located outdoor, whereas during Period 2 (P2) a compressed air stream fed with MeOH was treated using PVC rings and maintaining pH at neutral values. Both systems operated at 96g MeOHm−3 h−1 achieving removal efficiencies of around 90% during P1 and 99.9% during P2. The relative activity of biomass developed in both systems was assessed using respirometric analysis with samples obtained from both biofilms. Higher biomass activity was obtained during P2 (0.25–0.35kg MeOHkg−1 VSSd−1) whereas 1.1kg MeOHkg−1 VSSd−1 was obtained in the case of P1. The application of molecular and microscopic techniques showed that the eukaryotes were predominant during P1, being the yeast Candida boidinii the most abundant microorganism. A specific Fluorescence in situ hybridization probe was designed for C. boidinii and tested successfully. As a result of the neutral pH, a clear predominance of prokaryotes was detected during P2. Interestingly, some anaerobic bacteria were detected such as Desulfovibrio, Desulfobacteraceae species and also some archaea such as Methanosarcina. [Copyright &y& Elsevier]

Abstract: One of the main challenges that face successful biofiltration is the erratic loading pattern and long starvation periods. However, such patterns are common in practical applications. In order to provide long-term stable operation of a biofilter under these conditions, a cyclic adsorption/desorption beds system with flow switching was installed prior to a biofilter. Different square waves of a mixture containing n-hexane and benzene at a 2:1 ratio were applied to the cyclic adsorption/desorption beds and then fed to a biofilter. The performance of this integrated system was compared to a biofilter unit receiving the same feed of both VOCs. The cyclic adsorption/desorption beds unit successfully achieved its goal of stabilizing erratic loading even with very sharp peaks at the influent concentration equalizing influent concentrations ranging from 10–470ppmv for n-hexane to 30–1410ppmv for benzene. The study included different peak concentrations with durations ranging from 6 to 20min. The cyclic beds buffered the fluctuating influent load and the followed biofilter had all the time a continuous stable flow. Another advantage achieved by the cyclic adsorption/desorption beds was the uninterrupted feed to the biofilter even during the starvation where there was no influent in the feed. The results of the integrated system with regard to removal efficiency and kinetics are comparable to published results with continuous feed studies at the same loading rates. The removal efficiency for benzene had a minimum of 85% while for n-hexane ranged from 50% to 77% according to the loading rate. The control unit showed very erratic performance highlighting the benefit of the utilization of the cyclic adsorption/desorption beds. The biofilter was more adaptable to concentration changes in benzene than n-hexane. [ABSTRACT FROM AUTHOR]

Abstract: The bacterial composition of a lab-scale biotrickling filter (BTF) treating high loads of H2S was investigated by the rRNA approach. Two 16S rRNA gene clone libraries were established 42 and 189 d after reactor startup, while fluorescent in-situ hybridization (FISH) with DNA probes was performed throughout 260d of reactor operation. Diversity, community structure and metamorphosis were studied from reactor startup to fully-established pseudo-steady state operation at near neutral pH and at an inlet H2S concentration of 2000 ppmv (load of 55.6g H2S m−3 h−1). In addition, FISH was used for assessing the spatial distribution of sulfur-oxidizing bacteria (SOB) along the length of the reactor under pseudo-steady state operation. A major shift in the diversity of the community was observed with the operating time, from a well-diverse community at startup to pseudo-steady state operation with a majority of retrieved sequences affiliated to SOB of the sulfur cycle including Thiothrix spp., Thiobacillus spp., and Sulfurimonas denitrificans. Although aerobic species were predominant along the BTF, a vertical stratification was encountered, in which facultative anaerobes had a major relative abundance in the inlet part of the BTF, where the sulfide to oxygen ratio was higher. The observed changes were related to the trophic properties of the community, the DO concentration, the accumulation of elemental sulfur and the operation at neutral pH. [Copyright &y& Elsevier]

Abstract: Biofiltration of gas-phase styrene was studied using a newly isolated fungus Sporothrix variecibatus, in a perlite biofilter, at inlet concentrations and gas-flow rates ranging from 0.13 to 14gm−3 and 0.075 to 0.34m3 h−1, respectively, corresponding to empty bed residence times (EBRT) ranging between 91 and 20s. Styrene loading rates were varied between 50 and 845gm−3 h−1and a maximum elimination capacity of 336gm−3 h−1 was attained with nearly 65% styrene removal. On the other hand, the critical inlet loads to achieve more than 90% removal were 301, 240 and 92gm−3 h−1 for EBRT of 91, 40, and 20s, respectively. In order to test the stability and shock bearing capacity of the fungal biofilter, short-term tests were conducted by suddenly increasing the gas-phase styrene concentration, while maintaining the gas-flow rate constant. The response, a restoration in the removal performance to previous high values, after subjecting the biofilter to shock loads proves the resilient nature of the attached Sporothrix sp. and its suitability for biofiltration under non-steady state conditions. [Copyright &y& Elsevier]

Abstract: The fates of various nitrogen species were investigated in a layered biological infiltration system under an intermittently wetting regime. The layered system consisted of a mulch layer, coarse soil layer (CSL), and fine soil layer (FSL). The effects of soil texture were assessed focusing on the infiltration rate and the removal of inorganic nitrogen species. The infiltration rate drastically decreased when the uniformity coefficient was larger than four. The ammonium in the synthetic runoff was shown to be removed via adsorption during the stormwater dosing and nitrification during subsequent dry days. Stable ammonium adsorption was observed when the silt and clay content of CSL was greater than 3%. This study revealed that the nitrate leaching was caused by nitrification during dry days. Various patterns of nitrate flushing were observed depending on the soil configuration. The washout of nitrate was more severe as the silt/clay content of the CSL was greater. However, proper layering of soil proved to enhance the nitrate removal. Consequently, a strictly sandy CSL over FSL with a silt and clay content of 10% was the best configuration for the removal of ammonium and nitrate. [Copyright &y& Elsevier]

Trickle bed air biofilters (TBABs) are suitable for treatment of relatively high volumes of volatile organic compounds due to their controlled environment. A laboratory-scale TBAB was used for the treatment of an air stream contaminated with benzene under different loading rates (LRs) ranging from 7.2 to 76.8gm−3 h−1. The TBAB was operated at pH 7 and 25°C. Consistent long-term performance of the benzene TBAB depends on various factors one of which is the excess amount of biomass accumulated within the bed. Three experimental strategies for biomass control were employed in the study: weekly backwashing for 1h, starvation (no benzene feed for a period of 2d/week) and stagnation (no benzene, air and nutrient flow for a period of 2d/week). The experimental plan was designed to investigate the long-term performance of the TBAB with emphasis on the empty bed resident time (EBRT), different benzene LRs, removal efficiency with TBAB depth, volatile suspended solids and carbon mass balance closure. For benzene loading up to 34.1gm−3 h−1, removal efficiency consistently over 98% was achieved. At the maximum LR 76.8gm−3 h−1 the removal efficiency was still above 80% by utilizing stagnation strategy for 2d and gas flow switching once per week as means of biomass control. Backwashing once per week provided less efficient performance as compared to stagnation while starvation showed the worst performance. EBRT at 120s provided the best performance while EBRT at 90s showed slightly lower performance. [Copyright &y& Elsevier]

Rotating drum biofilters (RDBs) mounted with reticulated polyurethane sponge media has showed high removal efficiencies over a long period of time when used for volatile organic compound (VOC) removal. Due to the accumulation of biomass within the sponge medium, the porosity of a filter bed usually changes dynamically, which makes it difficult to predict and to control. In this paper, the porosity of a multi-layer RDB bed was investigated by a diffusion–reaction model in which biofilm growth and decay were taken into account at the pore scale of the sponge medium. Temporal and spatial changes of porosity were studied under various organic loadings and gas empty bed contact times (EBCTs). The porosity of the biofilter bed was assumed to be a function of biofilm thickness, and all the pores were assumed to be uniform. Toluene was selected as the model VOC. The model was solved using numerical methods through the MATLAB software. Results show that the porosity decreased with increased time of operation, increased toluene loading, or decreased gas EBCT value. The porosity in the outermost medium layer was less than that in the inner medium layers. Toluene removal efficiencies and porosities calculated from this model correlated with the experimental data well. Porosity variation was proposed to be an indicator for prediction of biofilter performance in biofilters as a consequence. [Copyright &y& Elsevier]

Exhausted carbon coming from the H2S adsorption process is a big environmental problem in Wastewater Treatment Plants. In this study, reusing exhausted carbon as a carrier of sulfide-oxidizing bacteria in lab-scale biofilters was evaluated. The exhausted carbons from different heights of the adsorption bed have different exhaustion extents, i.e. characteristics in terms of sulfur content, pH and porosity. Therefore, four biofilters were packed separately with exhausted carbon from top, middle, bottom of H2S adsorption bed, and a mixture of the three, to investigate the suitability for further H2S biofiltration. The results showed a quick startup in these biofilters (∼80h). The numbers of sulfide-oxidizing bacteria immobilized on activated carbon were approximately 4.8, 9.2 and 14×108 CFUg−1 top, middle and bottom carbon after the 240-h operation, respectively. In addition, the biofilters demonstrated a rapid recovery to the original removal efficiency (RE) within 2h after the H2S spike loadings. After a 110-h shutdown, the RE was rapidly recovered for all the biofilters within 5h, with a shorter time (1h) observed for the bottom carbon biofilter. The H2S removal mechanism of these biofilters was studied through a full analysis of sulfur products in both liquid (recycling medium) and activated carbon, and variable characterization of activated carbon before and after biofiltration. This study shows that the exhausted carbon-based biofilter is a feasible and economical alternative to conventional odor biofiltration. [Copyright &y& Elsevier]

A biofilter using granular activated carbon with immobilized Paracoccus sp. CP2 was applied to the elimination of 10–250ppm of trimethylamine (TMA), dimethylamine (DMA), and methylamine (MA). The results indicated that the system effectively treated MA (>93%), DMA (>90%), and TMA (>85%) under high loading conditions, and the maximum degradation rates were 1.4, 1.2, and 0.9g-Nkg−1 GAC d−1. Among the three different amines treated, TMA was the most difficult to degrade and resulted in ammonia accumulation. Further study on TMA removal showed that the optimal pH was near neutral (6.0–8.0). The supply of high glucose (>0.1%) inhibited TMA removal, maybe due to substrate competition. However, complete TMA degradation was achieved under the co-immobilization of Paracoccus sp. CP2 and Arthrobacter sp. CP1 (∼96%). Metabolite analysis results demonstrated that the metabolite concentrations decreased by a relatively small 27% while the metabolite apparently increased by heterotrophic nitrification of Arthrobacter sp. CP1 in the co-immobilization biofilter. [Copyright &y& Elsevier]

Abstract: The Cheng-Ching Lake Water Treatment Plant (CCLWTP) is the main supplier of domestic water for the Greater Kaohsiung area, the second largest metropolis in Taiwan. Biological activated carbon (BAC) filtration is one of the major treatment processes in CCLWTP. The objectives of this study were to evaluate the effectiveness of BAC filtration on water treatment in the studied advanced water treatment plant and its capability on pollutants [e.g., AOC (assimilable organic carbon), bromide, bromate, iron] removal. In this study, water samples from each treatment process of CCLWTP were collected and analyzed periodically to assess the variations in concentrations of AOC and other water quality indicators after each treatment unit. Moreover, the efficiency of biofiltration process using granular activated carbon (GAC) and anthracite as the fillers was also evaluated through a column experiment. Results show that the removal efficiencies for AOC, bromide, bromate, and iron are 86% 100%, 17%, and 30% after the BAC filter bed, respectively. This indicates that BAC filtration plays an important role in pollutant removal. Results also show that AOC concentrations in raw water and effluent of the CCLWTP are approximately 143 and 16μg acetate-Cl−1, respectively. This reveals that the treatment processes applied in CCLWTP is able to remove AOC effectively. Results of column study show that the AOC removal efficiencies in the GAC and anthracite columns are 60% and 17%, respectively. Microbial colonization on GAC and anthracite were detected via the observation of scanning electron microscopic images. The observed microorganisms included bacteria (rods, cocci, and filamentous bacteria), fungi, and protozoa. Results from this study provide us insight into the mechanisms of AOC removal by advanced water treatment processes. These findings would be helpful in designing a modified water treatment system for AOC removal and water quality improvement. [Copyright &y& Elsevier]

In biological gas treatment, like biofiltration of volatile organic compounds or odorous substances, the microbial nutritional needs could be a key factor of the process. The aim of this work is to propose a new packing material able to provide the lacking nutrients. In the first part of this study, two kinds of material composed of calcium carbonate, an organic binder and two different nitrogen sources, ammonium phosphate and urea phosphate (UP), were compared. The new supports present bulk densities between 0.88 and 1.15gcm−3, moisture retention capacities close to 50% and 70%, and water cohesion capacities greater than six months for the material with 20% binder. In the second part, oxygen consumption measurements in liquid experiments show that these packing materials could enhance bacterial growth compared to pine bark or pozzolan and have no inhibitory effect. The biodegradation of different substrates (sodium sulfide and ammonia) and the support colonization by the biomass were evaluated. Finally, UP 20 was chosen and tested in a hydrogen sulfide or ammoniac biofiltration process. This showed that, for H2S concentrations greater than 100mgm−3, UP 20 has a real advantage over pine bark or pozzolan. [Copyright &y& Elsevier]

Biofiltration of waste gases is cost-effective and environment-friendly compared to the conventional techniques for treating large flow rates of gas streams with low concentrations of pollutants. Pulp and paper industry off-gases usually contain reduced sulfur compounds, such as hydrogen sulfide and a wide range of volatile organic compounds (VOCs), e.g., methanol. It is desirable to eliminate both of these groups of compounds. Since the co-treatment of inorganic sulfur compounds and VOCs in biotrickling filters is a relatively unexplored area, the simultaneous biotreatment of H2S and methanol as the model VOC was investigated. The results showed that, after adaptation, the elimination capacity of methanol could reach around 236gm−3 h−1 with the simultaneous complete removal (100%) of 12ppm H2S when the empty bed residence time is 24s. The pH of the system was around 2. Methanol removal was hardly affected by the presence of hydrogen sulfide, despite the low pH. Conversely, the presence of the VOC in the waste gas reduced the efficiency of H2S biodegradation. The maximal methanol removal decreased somewhat when increasing the gas flow rate. This is the first report on the degradation of methanol at such low pH in a biotrickling filter and on the co-treatment of H2S and VOCs under such conditions. [Copyright &y& Elsevier]

Two independent parallel trickling bed air biofilters (TBABs) (“A” and “B”) with two different typical VOC mixtures were investigated. Toluene, styrene, methyl ethyl ketone (MEK), and methyl isobutyl ketone (MIBK) were the target VOCs in the mixtures. Biofilter “A” was fed equal molar ratio of the VOCs and biofilter “B” was fed a mixture based on EPA 2003 emission report. Backwashing and substrate starvation operation were conducted as biomass control. Biofilter “A” and “B” maintained 99% overall removal efficiency for influent concentration up to 500 and 300ppmv under backwashing operating condition, respectively. The starvation study indicated that it can be an effective biomass control for influent concentrations up to 250ppmv for biofilter “A” and 300ppmv for “B”. Re-acclimation of biofilter performance was delayed with increase of influent concentration for both biofilters. Starvation operation helped the biofilter to recover at low concentrations and delayed re-acclimation at high concentrations. Furthermore, re-acclamation for biofilter “B” was delayed due to its high toluene content as compared to biofilter “A”. The pseudo first-order removal rate constant decreased with increase of volumetric loading rate for both biofilters. MEK and MIBK were completely removed in the upper 3/8 media depth. While biofilter depth utilization for the removal of styrene and toluene increased with increase of influent concentrations for both biofilters. However, toluene removal utilized more biofilter depth for biofilter “B” as compared to biofilter “A”. [Copyright &y& Elsevier]

The performance of a lab scale biofilter packed with biomedia, encapsulated by sodium alginate and polyvinyl alcohol was used for treating ammonia (NH3) gas at different loading rates. The metabolic end products during NH3 oxidation were , and . It is noteworthy to mention that the immobilized cell biofilter required no separate acclimatization period and showed high removal efficiencies during the start of continuous experiments. The removal efficiency was nearly 100% when ammonia loading was 4.5gm−3 h−1 and the maximum elimination capacity achieved in this study was 5.5gNH3 m−3 h−1 at a loading rate of 7.5gm−3 h−1. Shock loading studies were carried out to ascertain the response of the immobilized cells to fluctuations in inlet concentration and flow rate. The inlet loading rates were varied between 0.05 and 6gNH3 m−3 h−1 during this phase of operation. The biofilter responded effectively to these shock loading conditions and recovered rapidly within 4–8h. Pressure drop values were consistently less and insignificant. The results from this study indicated that this immobilized cell biofilter could be considered as a potential option to treat NH3 under steady and transient state operation. [Copyright &y& Elsevier]

Packing materials play a key role in the performance of bioreactors for waste gas treatment and particularly in biofilter applications. In this work, the performance of four differently packed biofilters operated in parallel for the treatment of relatively high inlet concentration of toluene was studied. The reactors were compared for determining the suitability of coconut fiber, digested sludge compost from a waste water treatment plant, peat and pine leaves as packing materials for biofiltration of toluene. A deep characterisation of materials was carried out. Biological activity and packing capabilities related to toluene removal were determined throughout 240 days of operation under different conditions of nutrients addition and watering regime. Also, biofilters recovering after a short shutdown was investigated. Nutrient addition resulted in improved removal efficiencies (RE) and elimination capacities (EC) of biofilters reaching maximum ECs between 75 and 95gm−3 h−1 of toluene. In the first 80 days, the pH decreased progressively within the reactors, causing a population change from bacteria to fungi, which were the predominant decontaminant microorganisms thereafter. All reactors were found to recover the RE rapidly after a 5 days shutdown and, in a maximum of 7 days, all reactors had been completely recuperated. These results point out that fungal biofilters are a suitable choice to treat high loads of toluene. In general, coconut fiber and compost biofilters exhibited a better performance in terms of elimination capacity and long-term stability. [Copyright &y& Elsevier]

Abstract: The effects of temporal and spatial changes in biological activity and biomass amount on biofilter performance were investigated in a lab-scale trickle-bed air biofilter at a toluene loading of 46.9gm−3 h−1 under two different experimental strategies, namely, periodic backwashing at a rate of 1h once a week and 2d starvation. Analysis of the overall reaction for toluene metabolism revealed that cell synthesis was relatively favored over toluene oxidation in the inlet section of the biofilter, but over time its oxidation became favored throughout the biofilter bed. Periodic in situ backwashing with media fluidization effectively made even spatial distribution of biomass along the bed media, by which consistent high removal performance in the biofilter has been attained. After 2d starvation, the ratio of the biofilm EPS to the total biomass increased along the media bed depth, while the total biomass in the media bed subsequently decreased. The presence of sufficient biomass and microbial activity favorably influenced biofilter reacclimation after restart-up following starvation. [Copyright &y& Elsevier]

Abstract: In order to evaluate the combined effect of adsorption and biodegradation of H2S on activated carbon surface in biotrickling filtration, four laboratory-scale biofiltration columns were operated simultaneously for 120h to investigate the mechanisms involved in treating synthetic H2S streams using biological activated carbon (BAC). The first three columns (A, B, C) contained a mixture of activated carbon and glass beads, with the carbons (BAC or virgin activated carbon (VAC)) and conditions (with or without liquid medium recirculation) differentiated. The last column (D) used 100% glass beads with liquid medium recirculation. Air streams containing 45ppmv H2S were passed through the columns at 4s of gas retention time (GRT) and liquid flow rate was set at 0.71mlmin−1. Column D got its breakthrough in 3min of operation, indicating a negligible contribution of glass beads to the adsorption of H2S. The removal efficiency (RE) of Columns B and C using VAC dropped quickly to 30% within the first 8h, and afterwards continued to drop further but slowly. Column A using BAC stayed at 25% of RE throughout the operation time. A thorough investigation of the H2S oxidation products, i.e., various S species in both aqueous (recirculation media) and solid phases (BAC and VAC), was conducted using ICP-OES, IC, XRF, and CHNS elemental analyzer. BAC demonstrated a better performance than columns with adsorption only. Water film was found to enhance H2S removal. The percentage of sulphate in the total sulphur of the BAC system improved to twice of that of VAC system, indicating sulphate is the main product of H2S biofiltration. The observed pH drop in BAC system double confirmed that the presence of biodegradation in the biofilm over carbon surface did profound effect on the oxidation of H2S, compare to the systems with adsorption only. [Copyright &y& Elsevier]

Abstract: With ketone pollution forming an ever-growing problem, it is important to identify a ketone-degrading microorganism and establish its effect. Here, a methyl ethyl ketone (MEK)-degrading bacterium, Pseudomonas sp. KT-3, was isolated and its MEK degradation characteristics were examined in liquid cultures and a polyurethane-packed biofilter. In liquid cultures, strain KT-3 could degrade other ketone solvents, including diethyl ketone (DK), methyl propyl ketone (MPK), methyl isopropyl ketone (MIPK), methyl isobutyl ketone (MIBK), methyl butyl ketone (MBK) and methyl isoamyl ketone (MIAK). The maximum specific growth rate (μ max) of the isolate was 0.136h−1 in MEK medium supplemented with MEK as a sole carbon source, and kinetically, the maximum removal rate (V m) and saturation constant (K m) for MEK were 12.28mMg−1 DCWh−1 (DCW: dry cell weight) and 1.64mM, respectively. MEK biodegradation by KT-3 was suppressed by the addition of MIBK or acetone, but not by toluene. In the tested biofilter, KT-3 exhibited a>90% removal efficiency for MEK inlet concentrations of around 500ppmv at a space velocity (SV) of 150h−1. The elimination capacity of MEK was more influenced by SV than by the inlet concentration. Kinetic analysis showed that the maximum MEK removal rate (V m) was 690gm−3 h−1 and the saturation constant (K m) was 490ppmv. Collectively, these results indicate the polyurethane sequencing batch biofilter with Pseudomonas sp. KT-3 will provide an excellent performance in the removal of gaseous MEK. [Copyright &y& Elsevier]