Trickling filter technology for biotreatment of nitrogenous compounds emitted in exhaust gases from fishmeal plants

Ag/AgBr-oxygen enriched g-C3N4 for efficient photocatalytic degradation of trimethylamine

In this study, Ag/AgBr-O-gCN samples with ternary Z-type heterojunctions were prepared by in situ photoreduction using water as the reducing agent for generating Ag/AgBr active species and oxygen doping. The experimental results indicated that Ag/AgBr-O-gCN degraded trimethylamine by nearly 100% in half an hour and maintained 90% of its original activity after five cycles. The kinetic constant of Ag/AgBr-O-gCN was excellent at 0.0928 min-1, 3.8 times that of gCN, 2.3 times that of Ag/AgBr-gCN, and 1.9 times that of O-gCN. Unlike Ag/AgBr-gCN photoreduced by methanol, gCN was used as an electron donor in the aqueous solution during the photoreduction process, and oxidation sites between the gCN skeleton and Ag/AgBr were formed for constructing the heterojunction system. The Z-type heterojunction system was established by introducing a suitable size of Ag nanoparticles as the recombination center to keep indirect contact between gCN and AgBr. This effectively reduced the electron-hole recombination rate and caused activity enhancement. This study offers a novel idea for the construction of a ternary heterojunction.

Manganese doped two-dimensional zinc ferrite thin films as chemiresistive trimethylamine gas sensors

Trimethylamine (TMA) is highly toxic and can have lethal effects on living organisms. Detecting the presence of TMA in air is very important because, if the TMA level exceeds the OSHA (Occupational Safety and Health Administration) limit, it may harm the environment and endanger human life. Doping is an appropriate flexible way to change the electrical structures of metal oxide semiconductors (MOSs) and improve their ability to detect toxic gases. In this work, Mn-doped zinc ferrite thin film nanorods with agglomerated morphology were fabricated by a spray pyrolysis technique. For the first time, a comprehensive investigation was done on the gas sensing capabilities of Mn-doped ZnFe2O4 thin films. The findings showed that ZFM1 had the best gas sensing characteristics, with high sensitivity (S = 6.24), good selectivity, and quick recovery, towards 10 ppm TMA at ambient temperature. The alternate Mn-ZF sites are responsible for the rapid recovery because they can significantly increase the concentration of oxygen vacancies in the ZF crystal. 0.1 Mn doped ZnFe2O4 (ZFM1) thin film exhibits greatly enhanced gas sensing properties towards TMA, because of its high surface-to-volume ratio and rough surface with a small nanorod structure. The sensor's response to 10 ppm TMA was measured 13 weeks later for stability testing. The stability test results show that the coated ZFM1 film works well as a TMA gas sensor. This work shows that ZF thin films are effective in detecting TMA in the atmosphere.

A novel integrated industrial-scale biological reactor for odor control in a sewage sludge composting facility: Performance, pollutant transformation, and bioaerosol emission mechanism

In order to remove multiple pollutants in the sewage sludge (SS) composting facility, a novel integrated industrial-scale biological reactor based on biological trickling filtration and fungal biological filtration (BTF-FBF) was developed. This study examined bioaerosol emission, odour removal, pollutant transformation mechanism, and project investment. At an inlet flow rate of 7200 m³/h, the average removal efficiencies of hydrogen sulfide (H₂S), ammonia (NH₃), and volatile organic compounds (VOCs) during the steady stage were 97.2 %, 98.9 %, and 92.2 %. The BTF-FBF separates microbial phases (bacteria and fungi) of different modules. BTF removed most hydrophilic compounds, while FBF removed hydrophobic ones. Moreover, the reactor could effectively remove pathogens or opportunistic pathogens bioaerosols, such as Escherichia coli (61.9%), Salmonella sp. (85%), and Aspergillus fumigatus (82.1%). The pollutant transformation mechanism of BTF-FBF was proposed. BTF-FBF annualized costs were 324,783 CNY/year at 15 years. In conclusion, BTF-FBF provides new insights into composting facility bioaerosol, odour, and pathogen emission control.

Effects of Moisture on NH3 Capture Using Activated Carbon and Acidic Porous Polymer Modified by Impregnation with H3PO4: Sorbent Material Characterized by Synchrotron XRPD and FT-IR

The performances of reactive adsorbents, H₃PO₄/C (activated carbon) and H₃PO₄/A (Amberlyst 35), in removing NH₃ from a waste-gas stream were investigated using a breakthrough column. Accelerated aging tests investigated the effects of the water content on the performance of the adsorbents. Results of breakthrough tests show that the adsorption capacity greatly decreased with the drying time of H₃PO₄/C preparation. Synchrotron XRPD indicated increased amorphous phosphorus species formation with drying time. Nitrogen adsorption-desorption isotherms results further suggested that the evaporation of water accommodated in macropores decreases adsorption capacity besides the formation of the amorphous species. Introducing water moisture to the NH₃ stream increases the adsorption capacity concomitant with the conversion of some NH₄H₂PO₄ to (NH₄)₂HPO₄. Due to the larger pore of cylindrical type and more hydrophilic for acidic porous polymer support, as opposed to slit-type for the activated carbon, the adsorption capacity of H₃PO₄/A is about 3.4 times that of H₃PO₄/C. XRPD results suggested that NH₃ reacts with aqueous H₃PO₄ to form NH₄H₂PO_4, and no significant macropore-water evaporation was observed when acidic porous polymer support was used, as evidenced by N₂ isotherms characterizing used H₃PO₄/A.

A review of biotechnologies for the abatement of ammonia emissions

Ammonia emissions are found in a wide range of facilities such as wastewater treatment plants, composting plants, pig houses, as well as the fertilizer, food and metallurgy industries. Effective management of these emissions is important for minimizing the detrimental effects they can have on health and the environment. Physical-chemical (thermal oxidation, absorption, catalytic oxidation, etc.) treatments are the most common techniques for the abatement of ammonia emissions. However, the requirement for more eco-friendly techniques has increased interest in biological alternatives. Accordingly, several bio-based process configurations (biofilters, biotrickling filters and bioscrubbers) have been reported for ammonia abatement in a wide spectrum of conditions. Due to ammonia is a highly soluble compound, bioscrubber seems to be the best option for ammonia abatement. However, this technology is still not widely studied. The proper managements of the ammonia bio-oxidation sub-products is a key parameter for the correct operation of the process. The aim of this review is to critically examine the biotechnologies currently used for the treatment of ammonia gas emissions highlighting the pros and cons of each technology. The key parameters for each configuration used in both full-scale and lab-scale bioreactors are analyzed and summarized according to previous publications.

Biological fixed-film systems

The technical papers published in 2019 regarding wastewater treatment and microbial films were classified into two categories: biofilm and biofilm reactors. The biofilm category includes biofilm formation, biofilm consortia, bacterial signals, biofouling, extracellular polymeric substances, and biofilm membrane bioreactors. The biofilm reactors category provides recent information on rotating biological contactors, fluidized-bed biofilm reactors, integrated fixed-film activated sludge, moving-bed biofilm reactors, packed-bed biofilm reactors, sequencing biofilm batch reactors, and trickling filters.

Polyurethane Foams for Domestic Sewage Treatment

The aim of the study was to assess the possibility of using polyurethane foams (PUF) as a filling of a foam-sand filter to directly treat domestic sewage with increased content of ammonium nitrogen and low organic carbon to nitrogen ratio (C/N). The study compared performance of two types of flexible foams: new, cylinder-shaped material (Novel Foams, NF) and waste, scrap foams (Waste Foams, WF). The foams serving as a filling of two segments of a foam-sand filter were assessed for their hydrophobic and physical properties and were tested for their cell structure, i.e., cell diameter, cell size distribution, porosity, and specific surface area. The study accounted also for selected application-related properties, such as hydrophobicity, water absorption, apparent density, dimensional stability, amount of adsorbed biomass, and the possibility of regeneration. Cell morphology was compared in reference foams, foams after 14 months of the filter operation, and regenerated foams. The experimental outcomes indicated WF as an innovative type of biomass carrier for treating domestic sewage with low C/N ratio. SEM images showed that immobilization of microorganisms in NF and WF matrices involved the formation of multi-cellular structures attached to the inner surface of the polyurethane and attachment of single bacterial cells to the foam surface. The amount of adsorbed biomass confirmed that the foam-sand filter made up of two upper layers of waste foams (with diameters and pore content of 0.50-1.53 mm and 53.0-63.5% respectively) provided highly favorable conditions for the development of active microorganisms.

Comparative evaluation on the utilization of applied electrical potential in a conductive granule packed biotrickling filter for continuous abatement of xylene: Performance, limitation, and microbial community

This study investigates the use of electrically conductive granules as packing material in biotrickling filter (BTF) systems as to provide insights on the specific microbial abundance and functions during the treatment of xylene-containing waste gas. In addition, the effect of applied potential on attached biofilm on conductive granules during xylene degradation was briefly investigated. During stable operation period, the conductive granules packed BTF achieved reactor performance of no less than 80% with a maximum EC of 137.7 g/m³ h. Under applied potential of 1V, the BTF system showed deterioration of xylene removal by ranging from 21 to 76%, which also affected the distribution and relative abundance of the major microorganisms such as Xanthobacter, Acidovorax, Rhodococcus, Hydrogenophaga, Arthrobacter, Brevundimonas, Pseudoxanthomonas, Devosia, Shinella, Sphingobium, Dokdonella, Pseudomonas and Bosea. The acclimation of applied potential led to the enrichment of autotrophic bacteria and strains, which are correlated to improved nitrogen cycling. In general, applying electrical potential is feasible to shape the microbiological structure of biofilms to selectively adjust their biochemical functions.

Polyurethane film prepared from ball-milled algal polyol particle and activated carbon filler for NH3-N removal

This research offers a novel approach of free chemical preparation to obtain algae-based biopolyol through a ball milling method. The algae-based polyurethane (AlgPU) film was obtained from a casting solution made of ball-milled algal polyol particle and methylene diphenyl diisocyanate (MDI). The characteristics of the material had been investigated using Fourier Transform Infrared, Scanning Electron Microscopy – Electron Dispersive Spectroscopy, Differential Scanning Calorimetry, and Tensile Strength Analysis. The surface area was determined by Brunauer–Emmett–Teller (BET) isotherm, meanwhile the total pore volume was by Barrett-Joyner-Halenda (BJH) isotherm, based on the adsorption-desorption of N₂. The addition of activated carbon contributed in the increase of functional group and surface area, which were important for the NH₃–N removal. As a result, the adsorption capacity increased greatly after the addition of activated carbon (from 187.84 to 393.43 μg/g). The results also suggested AlgPU as a good matrix for immobilizing activated carbon filler. The adsorption shows a better fit with Langmuir isotherm model, with R² = 0.97487 and root-mean-square error (RMSE) = 33.91952, compared to Freundlich isotherm model (R² = 0.96477 and RMSE = 44.05388). This means the NH₃–N adsorption followed the assumption of homogenous and monolayer adsorption, in which the maximum adsorption was found to be 797.95 μg/g. This research suggests the potential of newly developed material for NH₃–N removal.

Gel-encapsulated microorganisms used as a strategy to rapidly recover biofilters after starvation interruption

Biosystems used for volatile organic compound (VOC) control have slow re-acclimation after extended starvation. In this study, a gel-encapsuled microorganism biofilter (GEBF) for the treatment of VOCs was used for rapid recovery after starvation interruption. Another conventional perlite biofilter (BF) was used as a control. Results showed that GEBF and BF needed 3 and 6 days for fully recovery after short-term (6 days) starvation. For long-term (20 days) starvation, GEBF fully recovered the removal performance after 9 days, whereas BF recovered only 70% within the same period. Flow cytometry analysis indicated that GEBF presented better viability state of microbial population than that in BF under starvation. The average metabolic activity of microorganisms in GEBF remained a relatively high during and after starvation (0.0049 h^-1). However, the average metabolic activity of microorganisms in BF decreased from 0.0042 h^-1 before starvation to 0.0033 h^-1 under starvation. Changes in the microbial community structure in GEBF and BF were investigated and compared by high-throughput sequencing and principal component analysis. Notably, the microbial community structure in the two biofilters showed different behavior. All these results demonstrated that the gel encapsulation of microorganisms is a promising strategy to resist starvation in biofiltration technologies.

Trimethylamine abatement in algal-bacterial photobioreactors

Trimethylamine (TMA) is an odorous volatile organic compound emitted by industries. Algal-based biotechnologies have been proven as a feasible alternative for wastewater treatment, although their application to abate polluted air emissions is still scarce. This work comparatively assessed the removal of TMA in a conventional bacterial bubble column bioreactor (BC) and a novel algal-bacterial bubble column photobioreactor (PBC). The PBC exhibited a superior TMA abatement performance compared to the conventional BC. In this sense, the BC reached a removal efficiency (RE) and an elimination capacity (EC) of 78% and 12.1 g TMA m^-3 h^-1, respectively, while the PBC achieved a RE of 97% and a EC of 16.0 g TMA m^-3·h^-1 at an empty bed residence time (EBRT) of 2 min and a TMA concentration ~500 mg m^-3. The outstanding performance of the PBC allowed to reduce the operating EBRT to 1.5 and 1 min while maintaining high REs of 98 and 94% and ECs of 21.2 and 28.1 g m^-3·h^-1, respectively. Moreover, the PBC improved the quality of the gas and liquid effluents discharged, showing a net CO₂ consumption and decreasing by ~ 30% the total nitrogen concentration in the liquid effluent via biomass assimilation. A high specialization of the bacterial community was observed in the PBC, Mumia and Aquamicrobium sp. being the most abundant genus within the main phyla identified. GraphicalAbstract.

Treatment of Gaseous Ammonia Emissions Using Date Palm Pits Based Granular Activated Carbon

The present work investigated the application of granular activated carbon (GAC) derived from date palm pits (DPP) agricultural waste for treating gaseous ammonia. Respective findings indicate increased breakthrough time (run time at which 5% of influent ammonia is exiting with the effluent gas) with a decrease in influent ammonia and increase in GAC bed depth. At a gas flow rate of 1.1 L/min and GAC column length of 8 cm, the following breakthrough trend was noted: 1295 min (2.5 ppmv) > 712 min (5 ppmv) > 532 min (7.5 ppmv). A qualitatively similar trend was also noted for the exhaustion time results (run time at which 95% of influent ammonia is exiting with the effluent gas). The Fourier Transform Infrared Spectroscopy (FTIR) findings for the produced GAC indicated some salient functional groups at the produced GAC surface including O–H, C–H, C–O, and S=O groups. Ammonia adsorption was suggested to result from its interaction with the respective surface functional groups via different mechanisms. Comparison with a commercial GAC showed the date palm pits based GAC to be having slightly higher breakthrough and exhaustion capacity.

Fungal elimination of toluene vapor in one- and two-liquid phase biotrickling filters: Effects of inlet concentration, operating temperature, and peroxidase enzyme activity

In this study, performance of biotrickling filters (BTFs) inoculated with fungus Phanerochaete chrysosporium at 30 °C and 40 °C in the absence and presence of silicone oil (10% v/v) was investigated. Removal of toluene was carried out at empty bed residence time (EBRT) of 1 min and at inlet concentrations of 0.5-4.4 g m^-3 and 0.5-24.7 g m^-3 for one-liquid phase (OLP-BTF) and two-liquid phase BTF (TLP-BTF), respectively. In general, at 40 °C, removal efficiencies (REs) > 80% were obtained in OLP-BTF for the inlet toluene concentrations < 2.5 g m^-3, and REs > 70% were obtained for concentrations < 18 g m^-3 in TLP-BTF. Based on the balanced equation for biodegradation, fungal respiration produced more CO₂ in OLP-BTF (1.38 mol CO₂/mole toluene) in comparison to TLP-BTF (0.67 mol CO₂/mole toluene). In other words, the presence of oil enhanced microbial growth due to the increase of hydrophobic substrate bioavailability. The activity of extracellular ligninolytic manganese peroxidase (MnP) enzyme produced by the fungal culture was detected in the range of 27.6-71.6 U L^-1 (μmol min^-1 L^-1) at 40 °C in TLP-BTF, while no enzymatic activity was detected in OLP-BTF.

Insights into the storage stability of ammonia in polyester aluminum bags

A list of gaseous odorants such as ammonia (and hydrogen sulfide) are generally collected using rigid containers or flexible bags for quantitative analysis. The aim of this investigation was to assess the stability of polyester aluminum bags used for gaseous ammonia sampling and storage. To this end, ammonia standards were prepared at two concentration levels of low (7.8 ppm) and high concentrations (39 ppm) and stored in the polyester ammonia bags for durations of 0, 1, 2, 4, and 6 days. These samples were then analyzed at each interval by an impinger-based indophenol method utilizing a spectrophotometer. At each pre-set period, three different mass loadings of ammonia samples were collected from the storage bag to obtain response factors (RF) for comparison between different elapsed times set for the storage. Subsequently, the relative recovery values for each interval were computed by dividing the RF for each sampling day by that of the 0^th day. The relative recovery values for low and high concentration standards decreased with increasing storage time as 82.9% (day 1) to 36% (day 6) and 89.9% (day 1) to 59.7% (day 6), respectively. As such, the potentially superior recovery of ammonia from polyester aluminum bags was demonstrated (e.g., relative to other storage options introduced previously) to support its practical merit as storage media.

Kinetic evaluation for rapid degradation of dimethylamine enriched with Agromyces and Ochrobactrum sp

Dimethylamine (DMA) possesses an obnoxious odor which has resulted in public concern during the past several decades. A rare bacterial species proficient to degrade DMA, designated IR-26, was isolated from Indian Oil Corporation Limited (IOCL) and identified as Agromyces and Ochrobactrum sp., which has presented a rapid degradation when compared to other bacterial species which were capable to degrade DMA. The removal efficiency of 100% has been calculated in different concentration of DMA. The kinetic study reveals the maximum reduction rate of DMA was 0.11 per hour and the maximum growth rate of biomass was 0.013 per hour respectively. The saturation constant of DMA was around 1.96 mg/L which shows a high affinity of DMA. The importance of these analyses is offered and conversed in this paper.

Application of a compact trickle-bed bioreactor for the removal of odor and volatile organic compounds emitted from a wastewater treatment plant

A compact trickle-bed bioreactor (CTBB) was tested for the removal of volatile organic compounds (VOCs) and hydrogen sulphide (H₂S) present in the exhaust air of a wastewater treatment plant. At gas-flow rates varying between 2.0 and 30.0 m³/h and for specific pollutant loads up to 20 g/(m³·h), removal efficiencies for H₂S and VOC were >95%. The CTBB was designed for a maximum H₂S concentration of ∼200 ppm and removal efficiencies >97% were noticed. VOC concentrations were in the range of 25-240 ppm_v and the removal efficiency was in the range of 85-99%. Possible consequences of an excessive pollutant overload and the time required for regenerating the microbial activity and reviving stable process conditions in the CTBB were also investigated. An increase in the H₂S concentration from 400 to 600 ppm_v for a few hours caused bioreactor poisoning; however, when original H₂S concentrations were restored, stable CTBB operation was ascertained within 3 h.