Microbial community structure and dynamics in a mixotrophic nitrogen removal process using recycled spent caustic under different loading conditions

Hacking biofilm developed in a structured-bed reactor (SBRRIA) with integrated processes of nitrogen and organic matter removal

Biomass samples from a structured-bed reactor subjected to recirculation and intermittent aeration (SBRRIA) were analyzed to investigate the bacterial community shift along with the changes in the C/N ratio. The C/N ratios tested were 7.6 ± 1.0 (LNC) and 2.9 ± 0.4 (HNC). The massive sequencing analyses revealed that the microbial community adjusted itself to different organic and nitrogenous applied loads, with no harm to reactor performance regarding COD and Total-N removal. Under LNC, conventional nitrification and heterotrophic denitrification steered the process, as indicated by the detection of microorganisms affiliated with Nitrosomonadaceae, Nitrospiraceae, and Rhodocyclaceae families. However, under HNC, the C/N ratio strongly affected the microbial community, resulting in the prevalence of members of Saprospiraceae, Chitinophagaceae, Xanthomonadaceae, Comamonadaceae, Bacillaceae, and Planctomycetaceae. These families include bacteria capable of using organic matter derived from cell lysis, ammonia-oxidizers under low DO, heterotrophic nitrifiers-aerobic denitrifiers, and non-isolated strains of Anammox. The DO profile confirmed that the stratification in aerobic, anoxic, and anaerobic zones enabled the establishment of different nitrogen degradation pathways, including the Anammox.

Effect of influent feeding pattern on municipal tailwater treatment during a sulfur-based denitrification constructed wetland

This work studied three parallel pilot-scale constructed wetlands based on sulfur-based autotrophic denitrification (SAD-CWs) with horizontal, vertical-horizontal and integrated vertical inflow for nitrogen removal of municipal tailwater. SAD system played the predominant role for nitrate removal and the integrated vertical inflow pattern was the most efficient pattern with 96.1% NO₃^--N and 44.3% total phosphorus (TP) removal efficiency, respectively, at the condition of 3.5 h hydraulic retention time (HRT) and 18.5-23.5 °C. Although no great and serious change for microbial community structure was observed among these systems, the diversity in term of abundance of microbes and certain function species was observed. Proteobacteria, Ignavibacterae and Chloroflexi were the dominant phyla and accounted for over 59.1%, 7.5%, and 6.0% in SAD-CWs, respectively. Moreover, the richness and diversity of denitrifies in SAD-CWs with integrated vertical inflow were both higher than that in the other two reactors, especially sulfur autotrophic denitrifying bacteria.

Thiosulfate-driven autotrophic and mixotrophic denitrification processes for secondary effluent treatment: Reducing sulfate production and nitrous oxide emission

Three ecological floating beds (EFBs) with different additional electron donors including sodium thiosulfate, mixed electron donors of sodium thiosulfate and sodium acetate and without additional electron donors were established to compare the differences of nitrogen removal efficiency, nitrous oxide emission, microbial community and functional gene between autotrophic and mixotrophic denitrification. Results showed denitrification efficiency was nearly 100% in both autotrophic and mixotrophic process when electron donors were sufficient while that ranged from 4 to 43% without additional electron donors. Sodium acetate addition could effectively decrease sulfate concentration in effluent and nitrogen oxide flux. In addition, high-throughput sequencing analysis revealed autotrophic denitrifying bacteria were dominant in autotrophic denitrification while autotrophic, facultative and heterotrophic denitrifying bacteria coexisted in mixotrophic denitrification, and there was no dominant genus. For EFB with mixed external autotrophic and heterotrophic electron donors, it can not only achieve better denitrification efficiency, but also reduce the emission of nitrous oxide.

Changes in the Soil Microbiome in Eggplant Monoculture Revealed by High-Throughput Illumina MiSeq Sequencing as Influenced by Raw Garlic Stalk Amendment

The incorporation of plant residues into soil can be considered a keystone sustainability factor in improving soil structure function. However, the effects of plant residue addition on the soil microbial communities involved in biochemical cycles and abiotic stress phenomena are poorly understood. In this study, experiments were conducted to evaluate the role of raw garlic stalk (RGS) amendment in avoiding monoculture-related production constraints by studying the changes in soil chemical properties and microbial community structures. RGS was applied in four different doses, namely the control (RGS0), 1% (RGS1), 3% (RGS2), and 5% (RGS3) per 100 g of soil. The RGS amendment significantly increased soil electrical conductivity (EC), N, P, K, and enzyme activity. The soil pH significantly decreased with RGS application. High-throughput Illumina MiSeq sequencing revealed significant alterations in bacterial community structures in response to RGS application. Among the 23 major taxa detected, Anaerolineaceae, Acidobacteria, and Cyanobacteria exhibited an increased abundance level. RGS2 increased some bacteria reported to be beneficial including Acidobacteria, Bacillus, and Planctomyces (by 42%, 64%, and 1% respectively). Furthermore, internal transcribed spacer (ITS) fungal regions revealed significant diversity among the different treatments, with taxa such as Chaetomium (56.2%), Acremonium (4.3%), Fusarium (4%), Aspergillus (3.4%), Sordariomycetes (3%), and Plectosphaerellaceae (2%) showing much abundance. Interestingly, Coprinellus (14%) was observed only in RGS-amended soil. RGS treatments effectively altered soil fungal community structures and reduced certain known pathogenic fungal genera, i.e., Fusarium and Acremonium. The results of the present study suggest that RGS amendment potentially affects the microbial community structures that probably affect the physiological and morphological attributes of eggplant under a plastic greenhouse vegetable cultivation system (PGVC) in monoculture.

Nitrate removal from drinking water with a focus on biological methods: a review

This article summarizes several developed and industrial technologies for nitrate removal from drinking water, including physicochemical and biological techniques, with a focus on autotrophic nitrate removal. Approaches are primarily classified into separation-based and elimination-based methods according to the fate of the nitrate in water treatment. Biological denitrification as a cost-effective and promising method of biological nitrate elimination is reviewed in terms of its removal process, applicability, efficiency, and associated disadvantages. The various pathways during biological nitrate removal, including assimilatory and dissimilatory nitrate reduction, are also explained. A comparative study was carried out to provide a better understanding of the advantages and disadvantages of autotrophic and heterotrophic denitrification. Sulfur-based and hydrogen-based denitrifications, which are the most common autotrophic processes of nitrate removal, are reviewed with the aim of presenting the salient features of hydrogenotrophic denitrification along with some drawbacks of the technology and research areas in which it could be used but currently is not. The application of algae-based water treatment is also introduced as a nature-inspired approach that may broaden future horizons of nitrate removal technology.

Coupling autotrophic denitrification with partial nitritation-anammox (PNA) for efficient total inorganic nitrogen removal

The performance of and the microbial ecology in an integrated lab scale set up comprising of a PN/A bioreactor and an elemental sulfur-supported packed bed autotrophic denitrification (ESSAD) are reported. The PN/A reactor exhibited an average removal rate of 0.56±0.103kgNm^-3d^-1, whereas the ESSAD reactor removed an average of 0.0018kg NO₃^--Nm^-3d^-1. The combined average removal rate was 0.6kgNm^-3d^-1, yielding an overall total inorganic nitrogen efficiency of 97%. Based on 16S rRNA gene clone libraries from the ESSAD reactor, the extracted Operational Taxonomic Units (OTUs) formed a clade with Thiobacillus denitrificans sp. indicating a common ancestral relationship. High throughput amplicon sequencing targeting V3 region of 16S rRNA gene for the biofilm in the ESSAD also revealed an abundance of the Thiobacillus genus. Additionally, 16s rRNA amplicon sequencing of the genomic DNA from the PN/A reactor reflected a dominance of the Planctomycetes phylum.

Consistent responses of the microbial community structure to organic farming along the middle and lower reaches of the Yangtze River

Soil microorganisms play a crucial role in the biogeochemical cycling of nutrient elements and maintaining soil health. We aimed to investigate the response of bacteria communities to organic farming over different crops (rice, tea and vegetable) along the middle and lower reaches of the Yangtze River of China. Compared with conventional farming, organic farming significantly increased soil nutrients, soil enzyme activities, and bacterial richness and diversity. A Venn diagram and principal component analysis revealed that the soils with 3 different crops under organic farming have more number and percent of shared OTUs (operational taxonomic units), and shared a highly similar microbial community structure. Under organic farming, several predominant guilds and major bacterial lineages (Rhizobiales, Thiotrichaceae, Micromonosporaceae, Desulfurellaceae and Myxococcales) contributing to nutrient (C, N, S and P) cycling were enriched, whereas the relative abundances of acid and alkali resistant microorganisms (Acidobacteriaceae and Sporolactobacillaceae) were increased under conventional farming practices. Our results indicated that, for all three crops, organic farming have a more stable microflora and the uniformity of the bacterial community structure. Organic agriculture significantly increased the abundance of some nutrition-related bacteria, while reducing some of the abundance of acid and alkali resistant bacteria.

The feasibility of an up-flow partially aerated biological filter (U-PABF) for nitrogen and COD removal from domestic wastewater

An up-flow partially aerated biological filter (U-PABF) was developed to study the removal of nitrogen and chemical oxygen demand (COD) from synthetic domestic wastewater. The removal of NH4(+)-N was primarily attributed to adsorption in the zeolite U-PABF and to bioprocesses in the ceramic U-PABF. When the hydraulic retention time (HRT) was 5.2h, the ceramic U-PABF achieved a good performance and the NH4(+)-N, total nitrogen (TN), and COD removal efficiency reached 99.08±8.79%, 72.83±0.68%, and 89.38±1.04%, respectively. The analysis of NH4(+)-N, NO3(-)-N, NO2(-)-N, and TN at different depths revealed the simultaneous existence of nitrification-denitrification, and anaerobic ammonium oxidation (anammox) in ceramic U-PABF. Illumina pyrosequencing confirmed the existence of Planctomycetes, which are responsible for anammox. The results indicated that the nitrification-denitrification and anammox all contributed to the high removal of NH4(+)-N, TN, and COD in the U-PABF.

Bioaugmentation with isolated strains for the removal of toxic and refractory organics from coking wastewater in a membrane bioreactor

The bioaugmentation strains for phenol, pyridine, quinoline, carbazole, and naphthalene degradation were employed to treat coking wastewater in a membrane bioreactor (MBR). The results showed that the bioaugmented MBR was much better in pollutant removal than that of the control MBR with conventional activated sludge. Compared to the control MBR, the bioaugmented MBR displayed an additional 3.2 mg/L of phenol, pyridine, quinoline, naphthalene and carbazole in total by the addition of the degrading strains. Also, about 10 % of the chemical oxygen demand in the effluent was further removed by the bioaugmentation. The pyrosequencing analysis of the sludge in the MBRs revealed that the microbial community shifted in response to the addition of the degrading strains. The diversity of the microbial community increased during the bioaugmentation, and some bacterial taxa favorable to the removal of toxic and refractory pollutants appeared in the bioaugmented MBR. The results indicated that the use of high-efficiency bacteria was a feasible method for industrial coking wastewater treatment.

Sulfate reduction and mixotrophic sulfide-utilization denitrification integrated biofilm process for sulfate-laden wastewater treatment and sulfur recovery

A novel and integrated biofilm process--the sulfate reduction (SR) and mixotrophic (MR) sulfide-utilization denitrification process (SMSD)--was recently proposed for sulfate treatment and sulfur recovery. The process consisted of two bioreactors: a 5.1 L anaerobic upflow reactor for SR, and a 3.5 L anaerobic upflow reactor for MR desulfurization-denitrification. The experiment was conducted for 370 days to evaluate the performance of SMSD at various sulfate concentrations and hydraulic retention times. The process successfully achieved sulfate, organics and nitrogen compound removal efficiencies of 94.1, 97.7 and 99.1%, respectively. Sulfate was predominantly converted to element sulfur, while nitrate and nitrite were finally converted to nitrogen gas. In SR, with the help of high pH and sponge cubes with various bacteria, 97.5% of sulfide conversion efficiency and 540 mgS/L of sulfide were obtained. In MR, sulfide was removed up to 100% and was partially oxidized to sulfur. The extent of heterotrophic denitrification, which ranged from 35.8 to 59.8%, depended on the categories of electron acceptors.

Kinetics of autotrophic denitrification process and the impact of sulphur/limestone ratio on the process performance

Kinetics of sulphur-limestone autotrophic denitrification process in batch assays and the impact of sulphur/limestone ratio on the process performance in long-term operated packed-bed bioreactors were evaluated. The specific nitrate and nitrite reduction rates increased almost linearly with the increasing initial nitrate and nitrite concentrations, respectively. The process performance was evaluated in three parallel packed-bed bioreactors filled with different sulphur/limestone ratios (1:1, 2:1 and 3:1, v/v). Performances of the bioreactors were studied under varying nitrate loadings (0.05 - 0.80 gNO(-)(3) - NL⁻¹ d⁻¹) and hydraulic retention times (3-12 h). The maximum nitrate reduction rate of 0.66 g L⁻¹ d⁻¹ was observed at the loading rate of 0.80 g NO(-)(3) - N L⁻¹ d⁻¹ in the reactor with sulphur/limestone ratio of 3:1. Throughout the study, nitrite concentrations remained quite low (i.e. below 0.5 mg L⁻¹ NO(-)(2) -N. The reactor performance increased in the order of sulphur/limestone ratio of 3:1, 2:1 and 1:1. Denaturing gradient gel electrophoresis analysis of 16S rRNA genes showed quite stable communities in the reactors with the presence of Methylo virgulaligni, Sulfurimonas autotrophica, Sulfurovum lithotrophicum, Thiobacillus aquaesulis and Sulfurimonas autotrophica related species.

Enhancing total nitrogen removal from wastewater of a science and industrial park using entrapped biomass

This study employed entrapped biomass technology to augment the conventional activated sludge process with anoxic-oxic (AO)/anaerobic-anoxic-oxic (A20) functions for the removal of total nitrogen (TN) from wastewater of a science and industrial park in Taiwan. The entrapped biomass unit was fabricated in the format of carrier plates on which microbial cells were entrapped. Due to mass transport limitations, anoxic and anaerobic conditions were created within the bioplates that enabled denitrification to occur. The treatment basin incorporated an equivalent amount of 1300-2400mg MLSS/L of activated sludge on the bioplates at packing ratios of 10-30% (volume ratio ofbioplates to basin) operating with the addition of sodium carbonate for alkalinity and methanol for the electron donor. The results showed nearly 90% of ammonia nitrogen being converted to nitrate and 63% of TN removal, in comparison with typically 10% of TN removal in traditional activated sludge process of domestic wastewater plants.

Composition and dynamics of microbial community in a zeolite biofilter-membrane bioreactor treating coking wastewater

In this study, a lab-scale anaerobic/anoxic/zeolite biofilter-membrane bioreactor (A1/A2/ZB-MBR) was designed to treat coking wastewater. The 454 pyrosequencing was used to obtain the composition and dynamics of microbial community about the treatment system. The results showed that the system yielded stable effluent chemical oxidation demand (158.5 ± 21.8 mg/L) and ammonia (8.56 ± 7.30 mg/L), but fluctuant total nitrogen (31.4-165.1 mg/L) concentrations. In addition, 66,256 16S rRNA gene sequences were obtained from A2 and ZB-MBR, and the microbial diversity and richness for five samples were determined. Although community compositions in the five samples were quite different, bacteria assigned to phylum Proteobacteria and class Flavobacteria commonly existed and dominated the microbial populations. The pyrosequencing analysis revealed that the microbial community shifted in the ZB-MBR with the presence of zeolite. Some taxa began to appear in ZB-MBR and contributed to the system performance. Additionally, Nitrosomonas and Nitrobacter gradually became the dominant ammonia-oxidizing bacteria and nitrite-oxidizing bacteria during the operation, respectively, which are favorable for the stabilized ammonia removal. Our results proved that the ZB-MBR is an alternative technique for treating coking wastewater.