Biological nitrogen removal and metabolic characteristics in a full-scale two-staged anoxic-oxic (A/O) system to treat optoelectronic wastewater

Nitrogen metabolism network in the biotreatment combination of coking wastewater: Take the OHO process as a case

As steel production increases, large volumes of highly toxic and nitrogen-rich coking wastewater (CWW) are produced, prompting the development of a novel oxic-hydrolytic-oxic (OHO) biological treatment combination designed for highly efficient removal of nitrogen-contained contaminants. However, previous studies have not comprehensively explored the CWW biotreatment from the perspective of nitrogen metabolism functional genes and pathways. Based on the investigation of taking the full-scale OHO biotreatment combination as a case, it was found that the O1 and O2 bioreactors remove nitrogen through the ammonia assimilation accounting for 33.87% of the total nitrogen (TN) removal rate, while the H bioreactor removes nitrogen through the simultaneous nitrification-denitrification accounting for 61.11% of the TN removal rate. The major ammonia assimilation taxa include Thauera, Immundisolibacter and Thiobacillus; the major nitrifying taxa include Nitrospira and Nitrosomonas; and the major denitrifying taxa include Thiobacillus, Lautropia and Mesorhizobium. Additionally, the H bioreactor exhibits the potential to be optimized for simultaneous nitrification-denitrification coupled with anaerobic ammonium oxidation (Anammox). These understandings will guide the optimization of engineering design and operational practices, contributing to more effective and sustainable wastewater treatment strategies.

Strengthening nitrogen removal of rural wastewater treatment in humus biochemical system under low dissolved oxygen conditions: Sludge and microbial characteristics

To achieve efficient and cost-effective treatment for the rural wastewater, a novel humus biochemical system (HBS) process derived from humus bio-functional material was proposed to treat rural wastewater under low dissolved oxygen (DO) conditions, and the operational performance, sludge characteristics, and microbial community in HBS were systematically investigated in this study. The results indicated that the HBS reactor could be operated stably under low DO levels of 0.2-0.8 mg/L, and maintained high removal efficiencies of 96.4%, 96.0%, and 88.2% for chemical oxygen demand, ammonia nitrogen, and total nitrogen, with corresponding effluent concentrations of 11.0, 1.7, and 5.1 mg/L, respectively. The sludge produced from HBS was characterized by relatively large particle size, complex structural morphology, and abundant humic substances, which favorably improved the system stability. Illumina sequencing demonstrated that HBS reactor possessed high microbial abundance and diversity and was enriched with plenty of nitrifying and denitrifying bacteria, which synergistically intensified the whole biological nitrogen removal process in this system. The study presented the feasibility and adaptability of HBS for energy-efficient rural wastewater treatment.

Advanced degradation of refractory organic compounds in electroplating wastewater by an in-situ electro-catalytic biological coupling reactor: Removal performance, microbial community and possible mechanism

A high-efficiency treatment system for advanced degradation of refractory organic compounds such as saccharin sodium (SS) and polyethylene glycol 6000 (PEG 6000) in electroplating wastewater was proposed, which coupled ion exchange, electrocatalysis, and microbial interactions through ion exchange particle electrode (IEPE) in a reactor, named in-situ electro-catalytic biological coupling reactor (i-SECBCR). A small-scale experimental test system was established and a feasibility investigation was conducted under the condition of 1.248 L/h continuous flow. The results revealed that (1) the i-SECBCR showed higher average removal rates of SS, PEG 6000, COD and NH4+-N, i.e. 88.48 %, 41.26 %, 66.81 % and 51.61 %,which meant an increase by 5.04 %, 12.05 %, 0.46 %, and 34.50 %, respectively, compared with BAF; (2) the optimal current intensity (CI) of i-SECBCR for simultaneous removal of SS, PEG 6000, COD and NH4+-N was 0.40 mA cm-2; (3) Rhodobacter, Defluviimonas, unclassified_f__Microscillaceae, Pseudoxanthomonas, Novosphingobium, and unclassified_f__Xanthobacteraccae accounted for the main bacterial community in i-SECBCR; (4) the possible degradation mechanism was attributed mainly to the synergistic effect of ion exchange, electrocatalytic oxidation and biology. Therefore, the i-SECBCR was suitable to simultaneously advanced remove SS, PEG 6000, COD and NH4+-N in electroplating wastewater.

Achieving tetracycline removal enhancement with granules in marine matrices: Performance, adaptation, and mechanism studies

Using the aerobic granular sludge (AGS) to improve tetracycline (TET) removal in the treatment of mariculture wastewater was investigated in the present study. The AGS rapidly adapted to and was sustained in seawater matrices with a robust granule strength (k = 0.0014) and a more stable sludge yield than the activated sludge (AS) (0.14 vs 0.11 g-VSS/g-COD_rem). The compact structure provided the AGS with an anoxic environment, which favored the growth of N (37.3 %) and P removal bacteria (30.4 %) and the expression of functional genes (nos, nor, and nar), resulting in more than 62 % TN and TP removals, respectively. Similar abundances of aromatic compound-degrading bacteria (∼34 %) in both reactors (AGS and AS) led to comparable TET biodegradation efficiencies (∼0.045 mg/g-VSS). The greater size and surface area of the AGS expanded the boundary layer diffusion region, leading to 16 % increases in the granule's TET adsorption capacity.

Metagenomic insights into microbial nitrogen metabolism in two-stage anoxic/oxic-moving bed biofilm reactor system with multiple chambers for municipal wastewater treatment

To explore the microbial nitrogen metabolism of a two-stage anoxic/oxic (A/O)-moving bed biofilm reactor (MBBR), biofilms of the system's chambers were analyzed using metagenomic sequencing. Significant differences in microbial populations were found among the pre-anoxic, oxic and post-anoxic MBBRs (P < 0.01). Nitrospira and Nitrosomonas had positive correlations with ammonia nitrogen (NH₄⁺-N) removal, and were also predominant in oxic MBBRs. These organisms were the hosts of functional genes for nitrification. The denitrifying genera were predominant in anoxic MBBRs, including Thiobacillus and Sulfurisoma in pre-anoxic MBBRs and Dechloromonas and Thauera in post-anoxic MBBRs. The four genera had positive correlations with total nitrate and nitrite nitrogen (NO_X^--N) removal and were the hosts of functional genes for denitrification. Specific functional biofilms with different microbial nitrogen metabolisms were formed in each chamber of this system. This work provides a microbial theoretical support for the two-stage A/O-MBBR system.

Performance and bacterial community analysis of a two-stage A/O-MBBR system with multiple chambers for biological nitrogen removal

A two-stage anoxic/oxic (A/O)-moving bed biofilm reactor (MBBR) system with multiple chambers was established for municipal wastewater treatment. At the total hydraulic retention time (HRT) of 11.2 h and nitrate recycling ratio of 1, the removal efficiencies reached 83.8%, 82.5%, and 77.8% for soluble chemical oxygen demand (SCOD), 98.0%, 97.5%, and 94.9% for ammonia nitrogen (NH₄⁺-N), and 91.8%, 92.0%, and 87.7% for total inorganic nitrogen (TIN) in summer, autumn and winter, respectively. Biofilms with functional bacterial populations were formed in the pre-anoxic reactors, the pre-oxic reactors, the post-anoxic reactors and the post-oxic reactors of the two-stage A/O-MBBR system. The highest nitrification potential was found in the last oxic reactor of the first A/O-MBBR subsystem with the highest relative abundances of the functional genes including [EC:1.14.99.39] and [EC:1.7.2.6]). The highest denitrification potential was found in the post-anoxic reactors with the highest relative abundances of the functional genes including [EC:1.7.2.1], [EC:1.7.2.5] and [EC:1.7.2.4]. This work constructed an efficient municipal biological nitrogen removal technology to achieve high effluent nitrogen standards in winter, and investigated its working mechanism to provide a basis for its design and optimization.

Applications of submerged and staged membrane systems for pollutant removal from effluents and mechanism studies - a review

Membrane based filtration is one of the promising technologies for rehabilitation of wastewater streams for reuse and recycle. Many advancements have emerged with the use of novel materials and innovative integrated technologies. The present investigation focuses on the treatment methods based on submerged and stages systems of membranes for water purification. Ceramic, polymeric and mixed matrix type of membranes fabricated for specific type of effluents, their modification methods for accelerating the rejection efficiency, permeability, durability, stability and antifouling properties are detailed in this review. Graphene oxide is the most considered membrane material for adsorption purposes as it exhibits larger surface area, abundant functional groups contain oxygen and has good supply of ligands which is responsible in metal adsorption as it enhances electrostatic interaction by bonding metal ions with graphene oxide nanosheets. Energy derivation in terms of biogas production was also reported in some integrated methods. In many cases, embedded nanomaterial matrices yielded maximum efficiencies in both the submerged and staged operations. However, submerged type of membranes are reported more than the staged type due to simpler configuration with relatively lesser equipment, operational and maintenance issues. In treatment of a low strength wastewater, aluminum oxide based membrane in fluidized bed assembly was reported to yield promising results with reduced power requirement.

Efficient treatment of digested piggery wastewater via an improved anoxic/aerobic process with Myriophyllum spicatum and bionic aquatic weed

The traditional anoxic/aerobic process (A/O) process is widely used for treating digested piggery wastewater, but the lack of carbon sources leads to poor efficiency. Therefore, the process needs optimization to achieve high-efficiency and low-cost operation mode. In this study, an improved A/O system with bionic aquatic weed and Myriophyllum sp. was established to decontaminate digested piggery wastewater. The average removal efficiencies of chemical oxygen demand (COD), NH₄⁺-N, and total nitrogen (TN) by the improved A/O system was satisfactory. The average removal efficiencies of COD, NH₄⁺-N, and TN were 62.1%, 87.5%, and 61.9%, respectively. High-throughput sequencing identified a number of dominant microorganisms. The relative abundance of Nitrosomonas (ammonia-oxidizing bacteria) and Nitrospira (nitrite-oxidizing bacteria) was 0.07%-3.52% and 0.32%-1.30%, respectively. Combining bionic aquatic weed and Myriophyllum sp. altered the microbial community structure and metabolic pathways. The results demonstrate a cost-effective method for treating digested piggery wastewater.

Bacterial diversity assessment of world's largest sewage-fed fish farms with special reference to water quality: a Ramsar site

Bacterial community structure is one of the essential components of aquaculture dynamics and plays an important role in maintaining wetland health. The present work is an effort to study the structure of bacterial communities in the world's largest sewage-fed fish farms, the East Kolkata Wetlands (EKWs), along with their predicted functional metabolic pathways and correlation with environmental variables. Sequencing data analysis revealed the abundance of genera such as Arcobacter (0-50%), Pseudomonas (0-15%), Sulfurospirillum (0-9%), Cloacibacterium (0-6%), hgcI clade (7-29%), C39 (0-9%), V6 (3-36%), Fluiivicola (1-6%) and Cyanobium (3-8%) in the EKWs. Further, water quality analysis of three treatment groups, i.e. Sewage, Sewage F-1 and Sewage F-2, revealed that dissolved oxygen (DO), biochemical oxygen demand (BOD) and chemical oxygen demand (COD) differed significantly and violated the standard prescribed norms (Central Pollution Control Board, CPCB, New Delhi) for fishery propagation and irrigation in India. Further, the correlation matrix analysis between the abundance of bacterial genera and environmental variables indicated that DO, BOD and COD were mainly responsible for bacterial community structure and their proliferation in the EKWs. Our results indicated that the abundance of genera such as Arcobacter, Pseudomonas, Sulfurospirillum and Cloacibacterium has an inverse relationship with BOD and COD. Our observations based on the bacterial community structure and deteriorated water quality indicate the ineffective functioning and poor management of this man-made constructed wetland.

Compact wastewater treatment process based on abiotic nitrogen management achieved high-rate and facile pollutants removal

Chemically enhanced primary treatment (CEPT), ammonium ion exchange and regeneration (AIR) and membrane bioreactor (MBR) were coupled as CAIRM to treat domestic wastewater compactly and efficiently. CAIRM achieved efficient removal of chemical oxygen demand, ammonia nitrogen, total nitrogen (TN) and total phosphorus with total hydraulic retention time of 4.6 h, and obtained 2.3 ± 0.9 mg/L TN in the effluent. CEPT removed phosphate and impurities and prevented AIR from pollution. AIR maintained excellent nitrogen removal with a slight decrease in the exchange capacity of ion exchangers. MBR polished the effluent from AIR, and the larger particle size and better dewaterability of sludge mitigated the membrane fouling. Many heterotrophic genera, such as Rhodobacter and Defluviimonas, were enriched in the oligotrophic MBR. This study demonstrates the viability and stability of CAIRM in efficient wastewater treatment, which will address critical challenges in insufficient nitrogen removal and high land occupancy of current processes.

The Tolerance of Anoxic-Oxic (A/O) Process for the Changing of Refractory Organics in Electroplating Wastewater: Performance, Optimization and Microbial Characteristics

In order to investigate the tolerance of an anoxic-oxic (A/O) process for the changing of refractory organics in electroplating wastewater, optimize the technological parameters, and reveal the microbial characteristics, a pilot-scale A/O process was carried out and the microbial community composition was analyzed by high-throughput sequencing. The results indicated that a better tolerance was achieved for sodium dodecyl benzene sulfonate, and the removal efficiencies of organic matter, ammonia nitrogen (NH4+-N), and total nitrogen (TN) were 82.87%, 66.47%, and 53.28% with the optimum hydraulic retention time (HRT), internal circulation and dissolved oxygen (DO) was 12 h, 200% and 2–3 mg/L, respectively. Additionally, high-throughput sequencing results demonstrated that Proteobacteria and Bacteroidetes were the dominant bacteria phylum, and the diversity of the microbial community in the stable-state period was richer than that in the start-up period.

Bio-leaching of manganese from electrolytic manganese slag by Microbacterium trichothecenolyticum Y1: Mechanism and characteristics of microbial metabolites

The related microbial metabolomics on biological recovery of manganese (Mn) from Electrolytic Manganese Slag (EMS) has not been studied. This study aimed at open the door to the metabolic characteristics of microorganisms in leaching Mn from EMS by using waste molasses (WM) as carbon source. Results show Microbacterium trichothecenolyticum Y1 (Y1) could effectively leach Mn from EMS in combination with using waste molasses as carbon and energy sources. For the first time, Y1 was identified to be capable of generating and then metabolizing several organic acids or other organic matter (e.g., fumaric acid, succinic acid, malic acid, glyoxylic acid, 3-hydroxybutyric acid, glutaric acid, L(+)-tartaric acid, citric acid, tetrahydrofolic acid, and L-methionine). The production of organic acids by Y1 bacteria was promoted by EMS with the carbon source. This study demonstrated for the first time that metabolic characteristics and carbon source metabolic pathways of Y1 in bioleaching of Mn from EMS.

Improvement in nitrogen removal and changes in community structure in a sequencing batch reactor bioaugmented with P. stutzeri strain XL-2

The aim of this work was to study the bioaugmentation of P. stutzeri strain XL-2 in activated sludge to improve nitrogn removal from wastewater with the guide of growth kinetics. When 4250 mg/L COD and 80 mg/L NH₄⁺-N were applied, the TN removal efficiency in a bioaugmented sequencing batch reactor (SBR_XL) achieved 95%, while that in the control reactor (SBR_C) without strain XL-2 was only 84% (P < 0.05). The microbial community analysis demonstrated that strain XL-2 was successfully bioaugmented in SBR_XL, and increasing influent COD concentration promoted its abundance. Influent COD concentration played a dominant role in affecting community structure, while the bioaugmentation of strain XL-2 had much less impact on the community structure. Combined with principal coordinates analysis, redundancy analysis and FAPROTAX, the improvement of TN removal was mainly achieved by the bioaugmentation of strain XL-2, which played a major role in promoting aerobic denitrification.

Effects of plants competition on critical bacteria selection and pollutants dynamics in a long-term polyculture constructed wetland

The effects of mix planting on the functions of plants, microorganisms, and their interactions were studied in a CW planted with Phragmites australis and Typha orientalis over six years. Findings show notable competition among plant species, with excessive overgrowth of the dominant species (P. australis) over T. orientalis. The excessive outcompeting by P. australis resulted in significantly higher plant density and biomass of 20.1 times and 11.2 times, respectively than that of T. orientalis. Interspecific competition appeared to considerably intensify plants contributions to nitrogen and phosphorus removal, which increased from circa 9% in the first year up to 42% in the sixth year. High-throughput pyrosequencing and network analyses demonstrated that the dominant species stands harbor diverse bacterial communities that could enhance the wetland performance through carbon degradation, nutrient cycling, and supporting plant growth. These results provide useful insights into the interactive effects of plants and bacteria in polyculture constructed wetlands.