Enhanced removal of NH3 during composting by a biotrickling filter inoculated with nitrifying bacteria

Surface acidic sites strengthened core-shell HC@MnO2 for enhanced gaseous ammonia adsorption

As a common gaseous pollutant in atmospheric environment, ammonia (NH3) not only contributes to the formation of haze, but also disturb the nitrogen balance in ecosystem through atmospheric nitrogen deposition. Therefore, the control of NH3 emission has important environmental significance. Adsorption is the most commonly used technology for NH3 purification in practice, and efficient adsorbents are the key to adsorption method. Herein, a core-shell structured HC@MnO2 adsorbent was constructed by in-situ growth of layered δ-MnO2 on hydrochar (HC) surface, and its surface acidic sites were further strengthened. The enhancement of surface acidic sites significantly improved the adsorption performance of HC@MnO2 for NH3, reaching 34.49 mg NH3/g, which was superior to commercial carbon-based materials (whose adsorption capacity was 8.47 times that of Coal-based activated carbon, 14.25 times that of Coconut shell activated carbon, and 12.77 times that of Bamboo charcoal). Moreover, the operating parameters and adsorption kinetics were detailly investigated. The adsorption of HC@MnO2 on NH3 was in accordance with pseudo-second-order adsorption kinetics model. Large surface area of core-shell structure and abundant surface acidic sites of δ-MnO2 are the decisive reasons for the excellent adsorption performance of HC@MnO2. Importantly, the enhancement of surface stronger Brønsted acidic sites is the key to improve NH3 adsorption performance of HC@MnO2. Finally, the thermal regeneration and recycling performance of HC@MnO2-H were also investigated. This study provides a suggestive for further research on low-cost composite materials with excellent NH3 adsorption performance.

Effect of co-culturing bacteria and microalgae and influence of inoculum ratio during the biological treatment of tannery wastewater

This present investigation is carried out to study the effect of algal and bacterial inoculum concentrations on the removal of organic pollutants and nutrients from the tannery effluent by the combined symbiotic treatment process. The bacterial and microalgal consortia was developed in laboratory setup and mixed together to perform this study. The Influence of algae and bacteria inoculum concentrations on the removal of pollutants such as Chemical Oxygen Demand (COD) and Total Kjeldahl Nitrogen (TKN) were studied using statistical optimization through Response surface methodology. For the design of experimental set up and optimization, full factorial Central composite design was used. The profiles of pH, Dissolved Oxygen (DO) and nitrate were also monitored and studied. The inoculum concentrations of microalgae and bacteria showed significant effect on Co-culturing on COD, TKN and nitrate removals as major response. The linear effect of bacterial inoculum has positive dominant influence on COD and TKN removal efficiencies. Nitrate utilization by microalgae increases with the increase in microalgal inoculum concentration. The maximum removal efficiencies of COD and TKN with 89.9% and 80.9% were obtained at optimum bacterial and algal inoculum concentrations of 6.7 g/L and 8.0 g/L respectively. These outcomes of this study are immensely favorable for maximizing the COD and nitrogen (nutrients) removal capabilities of microalgae-bacterial consortia in tannery effluent.

Improving NH3 and H2S removal efficiency with pilot-scale biotrickling filter by co-immobilizing Kosakonia oryzae FB2-3 and Acinetobacter baumannii L5-4

In this study, two NH₄⁺-N and S^2- removal strains, namely, Kosakonia oryzae (FB2-3) and Acinetobacter baumannii (L5-4), were isolated from the packing materials in a long-running biotrickling filter (BTF). The removal capacities of combined FB2-3 and L5-4 (FB2-3 + L5-4) toward 100 mg L^-1 of NH₄⁺-N and 200 mg L^-1 of S^2- reached 97.31 ± 1.62% and 98.57 ± 1.12% under the optimal conditions (32.0 °C and initial pH = 7.0), which were higher than those of single strain. Then, FB2-3 and L5-4 liquid inoculums were prepared, and their concentrations respectively reached 1.56 × 10⁹ CFU mL^-1 and 1.05 × 10⁹ CFU mL^-1 by adding different resuspension solutions and protective agents after 12-week storage at 25 °C. Finally, pilot-scale BTF test showed that NH₃ and H₂S in the real exhaust gases from a pharmaceutical factory were effectively removed with removal rates > 87% and maximum elimination capacities were reached 136 g (NH₃) m^-3 h^-1 and 176 g (H₂S) m^-3 h^-1 at 18 °C-34 °C and pH 4.0-7.0 in the BTF loaded with bamboo charcoal packing materials co-immobilized with FB2-3 and L5-4. After co-immobilization of FB2-3 and L5-4, in the bamboo charcoal packing materials, the new microbial diversity composition contained the dominant genera of Acinetobacter, Mycobacterium, Kosakonia, and Sulfobacillus was formed, and the diversity of entire bacterial community was decreased, compared to the control. These results indicate that FB2-3 and L5-4 have potential to be developed into liquid ready-to-use inoculums for effectively removing NH₃ and H₂S from exhaust gases in BTF.

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.

The role of a newly isolated strain Corynebacterium pollutisoli SPH6 in waste activated sludge alkaline fermentation

Alkaline fermentation has been considered as one of the efficient methods for waste activated sludge (WAS) treatment, but usually limited by microbial fermentation activities under extreme pH condition. One newly isolated alkali-tolerant strain Corynebacterium pollutisoli SPH6 was used to assess its potential role and effect on WAS alkaline fermentation process. Results from response surface method showed that the optimal organic nitrogen degradation rate by SPH6 was obtained under temperature of 35 °C, initial pH of 10, shaking speed of 80 rpm, inoculation ratio of 6.5%. Batch-scale experiments demonstrated that, compared with the control group, the inoculation of SPH6 finally achieved higher productions with 13.4% of carbohydrates, 27.1% of protein and 25.4% of total volatile fatty acids (VFAs), and more predominant functional bacteria characterized by high-throughput sequencing, such as genera Acinetobacter in phylum Proteobacteria, Tissierella and Acetoanaerobium in phylum Firmicutes. The strain SPH6 might play a vital role in maintaining and facilitating the growth and diversity of functional bacteria in WAS alkaline fermentation process. It has implied promising practical application of the present strain in enhancing WAS reduction and utilization.

Long-term microbial community dynamics at two full-scale biotrickling filters treating pig house exhaust air

In this study, the microbial community structure of two full‐scale biotrickling filters treating exhaust air from a pig housing facility were evaluated using 16S metabarcoding. The effect of inoculation with activated sludge of a nearby domestic waste water treatment plant was investigated, which is a cheap procedure and easy to apply in practice. The study was performed at a three‐stage and a two‐stage full‐scale biotrickling filter; of which, only the latter was inoculated. Both biotrickling filters evolved towards a rather similar community over time, which differed from the one in the activated sludge used for inoculation. However, the bacterial population at both biotrickling filters showed small differences on the family level. A large population of heterotrophic bacteria, including denitrifying bacteria, was present in both biotrickling filters. In the non‐inoculated biotrickling filter, nitrite‐oxidizing bacteria (NOB) could not be detected, which corresponded with the incomplete nitrification leading to high nitrite accumulation observed in this system. Inoculation with the wide spectrum inoculum activated sludge had in this study a positive effect on the biotrickling filter performance (higher ammonia removal and lower nitrous oxide production). It could thus be beneficial to inoculate biotrickling filters in order to enrich NOB at the start‐up, making it easier to keep the free nitrous acid concentration low enough to not be inhibited by it.

Mitigating Greenhouse Gas and Ammonia Emissions from Beef Cattle Feedlot Production: A System Meta-Analysis

Beef cattle production systems are the largest contributors of greenhouse gas (GHG) and ammonia (NH₃) emissions in the livestock industry. Here, we present the first meta-analysis and integrated assessment of gaseous emissions and mitigation potentials for a typical beef cattle feedlot system, including methane (CH₄), nitrous oxide (N₂O), and NH₃ losses from enteric fermentation and manure management based on data from 104 studies. A total of 14 integrated emission factors (EF) and the mitigation efficiencies (ME) of 17 available options were provided. The estimated GHG and NH₃ emissions from the baseline feedlot system were 2786 ± 108 kg carbon dioxide equivalents (CO₂-eq) per animal unit (AU) per year and 49.1 ± 1.5 kg NH₃ AU^-1 year^-1, respectively. Enteric CH₄ fermentation and manure on the feedlot contributed 67.5% and 80.8% of the total system GHG and NH₃ emissions, respectively. The highest ME values were found for lipid additives for enteric CH₄ fermentation and urease inhibitor additives (UI) for NH₃ emissions from manure on the feedlot, being -14.9% ( p < 0.05) and -59.5% ( p < 0.001), respectively. The recommended mitigation combinations of a low-crude-protein (CP) diet and a UI additive for manure on the feedlot could reduce the GHG of the system by 4.9% and NH₃ by 50.9%. The results of this study have important implications for developing sustainable beef cattle feedlot systems from the viewpoint of GHG and NH₃ mitigation.

Biostimulation of nutrient additions on indigenous microbial community at the stage of nitrogen limitations during composting

Microorganisms can play a crucial role in the efficiency for composting, which are essential for converting the organic wastes into a well-stabilized, value added product. However, the activity of most of the key functional microorganisms were inhibited due to the limited special nutrient substances or other physiochemical factors during composting, which further affected the quality of compost. The study was conducted to investigate the effects of enriched ammonium (NH₄⁺-N) and organic nitrogen (Org-N) on indigenous microbial community and whether nitrogen (N) nutrient additions could modify the special species during composting. The results showed that the abundance and structure of bacterial community had distinctly diverse responses to different N nutritional treatments (no nutrient addition, NH₄⁺-N addition, and Org-N addition). The addition of N sources enhanced the abundance of corresponding uncultured indigenous species negatively related to the factor of NH₄⁺ and Org-N in redundancy analysis (RDA) during composting but the effect of NH₄⁺ was more significant than Org-N. Nonmetric multidimensional scaling ordination (NMDS) demonstrated that both the two N additions changed bacterial community but had different duration for affecting bacterial composition. Conclusively, an optimized method for regulating the key stains with special biological capacity is proposed by controlling the single limiting-nutrient factor sharply decreasing at one of composting stages and negatively related to the key species in RDA.

Comparison between absorption and biological activity on the efficiency of the biotrickling filtration of gaseous streams containing ammonia

Polluted air streams can be purified using biological treatments such as biotrickling filtration, which is one of the most widely accepted techniques successfully tuned to treat a wide variety of exhausted gaseous streams coming from a series of industrial sectors such as food processing, flavor manufacturers, rendering, and composting. Since the degradation of a pollutant occurs at standard pressure and temperature, biotrickling filtration, whether compared with other more energy-demanding chemical-physical processes of abatement (such as scrubbing, catalytic oxidation, regenerative adsorption, incineration, advanced oxidation processes, etc.), represents a very high energy-efficient technology. Moreover, as an additional advantage, biodegradation offers the possibility of a complete mineralization of the polluting agents. In this work, biotrickling filtration has been considered in order to explore its efficiency with respect to the abatement of ammonia (which is a highly water-soluble compound). Moreover, a complete mathematical model has been developed in order to describe the dynamics of both absorption and biological activities which are the two dominant phenomena occurring into these systems. The results obtained in this work have shown that the absorption phenomenon is very important in order to define the global removal efficiency of ammonia from the gaseous stream (particularly, 44% of the ammonia is abated by water absorption). Moreover, it has been demonstrated (through the comparison between experimental results and theoretical simulations) that the action of bacteria, which enhance the rate of ammonia transfer to the liquid phase, can be modeled through a simple Michaelis-Menten relationship.

Effect of multi-stage inoculation on the bacterial and fungal community structure during organic municipal solid wastes composting

In this study, PCR-DGGE method was applied to investigate the impact of multi-stage inoculation treatment on the community composition of bacterial and fungal during municipal solid wastes (MSW) composting process. The results showed that the high temperature period was extended by the multi-stage inoculation treatment, 1day longer than initial-stage inoculation treatment, and 5days longer than non-inoculation treatment. The temperature of the secondary fermentation increased to 51°C with multi-stage inoculation treatment. The multi-stage inoculation method improved the community diversity of bacteria and fungi that the diversity indexes reached the maximum on the 17days and 20days respectively, avoided the competition between inoculations and indigenous microbes, and enhanced the growth of dominant microorganisms. The DNA sequence indicated that various kinds of uncultured microorganisms with determined ratios were detected, which were dominant microbes during the whole fermentation process. These findings call for further researches of compost microbial cultivation technology.

The operating performance of a biotrickling filter with Lysinibacillus fusiformis for the removal of high-loading gaseous chlorobenzene

Removal of gaseous chlorobenzene (CB) by a biotrickling filter (BTF) filled with modified ceramics and multi-surface hollow balls during gas-liquid mass transfer at the steady state was by microbial degradation rather than dissolution in the spray liquid or emission into the atmosphere. The BTF was flexible and resistant to the acid environment of the spray liquid, with the caveat that the spray liquid should be replaced once every 6-7 days. The BTF, loaded with Lysinibacillus fusiformis, performed well for purification of high-loading CB gas. The maximum CB gas inlet loading rate, 103 g m(-3) h(-1), CB elimination capacity, 97 g m(-3) h(-1), and CB removal efficiency, 97.7 %, were reached at a spray liquid flow rate of 27.6 ml min(-1), an initial CB concentration of up to 1,300 mg m(-3), and an empty bed retention time of more than 45 s.

Transient-state studies and neural modeling of the removal of a gas-phase pollutant mixture in a biotrickling filter

The removal efficiency (RE) of gas-phase hydrogen sulfide (H), methanol (M) and α-pinene (P) in a biotrickling filter (BTF) was modeled using artificial neural networks (ANNs). The inlet concentrations of H, M, P, unit flow and operation time were used as the model inputs, while the outputs were the RE of H, M and P, respectively. After testing and validating the results, an optimal network topology of 5-8-3 was obtained. The model predictions were analyzed using Casual index (CI) values. M removal in the BTF was influenced positively by the inlet concentration of M in mixture (CI=3.79), while the removal of P and H were influenced more by the time of BTF operation (CI=25.36, 15.62). The BTF was subjected to different types of short-term shock-loads: 5-h shock-load of HMP mixture simultaneously, and 2.5-h shock-load of either H, M, or P, individually. It was observed that, short-term shock-loads of individual pollutants (M or H) did not significantly affect their own removal, but the removal of P was affected by 50%. The results from this study also show the sensitiveness of the well-acclimated BTF to handle sudden load variations and also revival capability of the BTF when pre-shock conditions were restored.

Ammonia removal from a waste air stream using a biotrickling filter packed with polyurethane foam through the SND process

This paper presents the results of a bench-scale biotrickling filter (BTF) on the removal of ammonia gas from a waste stream using a simultaneous nitrification/denitrification (SND) process. It was found that the developed BTF could completely remove 100 ppm ammonia from a waste stream, with an empty bed retention time of 60 s and 98.4% nitrogen removal through the SND process under the tested conditions. It was elucidated that both autotrophic and heterotrophic bacteria were involved in the nitrogen removal trough the SND process in the BTF. Additionally, the elimination capacity of total nitrogen by the BTF increased from 3.5 to 18.4 g N/m(3) h with an inlet load of 20.6 g N/m(3) h (73.6%). The findings of this study suggest that the BTF can be operated to attain complete ammonia removal through the SND process, thereby making the treatment of ammonia-laden gas streams both short and cost-effective.