Simultaneous Nitrification-denitrification Research Articles

Nitrification–Autotrophic Denitrification Using Elemental Sulfur as an Electron Donor in a Sequencing Batch Reactor (SBR): Performance and Kinetic Analysis

Simultaneous nitrification and autotrophic denitrification (SNAD) has received attention as an efficient biological nitrogen removal alternative. However, SNAD using elemental sulfur (S0) has scarcely been studied. Thus, the main objective of this research was to study the behavior of a simultaneous nitrification–autotrophic denitrification operation in a sequential batch reactor (SNAD-SBR) at a lab scale using S0 as an electron donor, including its kinetics. Two-scale reactors were operated at lab scales in cycles for 155 days with an increasing nitrogen loading rate (NLR: 0.0296 to 0.0511 kg N-NH4+/m3/d) at 31 °C. As a result, simultaneous nitrification–autotrophic denitrification using S0 as an electron donor was performed successfully, with nitrification efficiency of 98.63% and denitrification efficiency of 44.9%, with autotrophic denitrification as the limiting phase. The kinetic model adjusted for ammonium-oxidizing bacteria (AOB) was the Monod-type kinetic model (µmax = 0.791 d−1), while, for nitrite-oxidizing bacteria (NOB), the Haldane-type model was employed (µmax = 0.822 d−1). For denitrifying microorganisms, the kinetic model was adjusted by a half order (k1/2v = 0.2054 mg1/2/L1/2/h). Thus, we concluded that SNAD could be feasible using S0 as an electron donor, with kinetic behavior similar to that of other processes.

Influence of aeration modes and DO on simultaneous nitrification and denitrification in treatment of hypersaline high-strength nitrogen wastewater using sequencing batch biofilm reactor (SBBR)

Sequencing batch biofilm reactor (SBBR) has the potential to treat hypersaline high-strength nitrogen wastewater by simultaneous nitrification-denitrification (SND). Dissolved oxygen (DO) and aeration modes are major factors affecting pollutant removal. Low DO (0.35–3.5 mg/L) and alternative anoxic/aerobic (A/O) mode are commonly used for municipal wastewater treatment, however, the appropriate DO concentration and operation mode are still unknown under hypersaline environment because of the restricted oxygen transfer in denser extracellular polymeric substances (EPS) barrier and the decreased carbon source consumption during the anoxic phase. Herein, two SBBRs (R1, fully aerobic mode; R2, A/O mode) were used for the treatment of hypersaline high-strength nitrogen wastewater (200 mg/L NH4+-N, COD/N of 3 and 3% salinity). The results showed that the relatively low DO (2 mg/L) could not realize effective nitrification, while high DO (4.5 mg/L) evidently increased nitrification efficiency by enhancing oxygen transfer in denser biofilm that was stimulated by high salinity. A stable SND was reached 16 days faster with a ∼10% increase of TN removal under A/O mode. Mechanism analysis found that denser biofilm with coccus and bacillus were present in A/O mode instead of filamentous microorganisms, with the secretion of more EPS. Corynebacterium and Halomonas were the dominant genera in both SBBRs, and HN-AD process might assist partial nitrification-denitrification (PND) for highly efficient TN removal in biofilm systems. By using the appropriate operation mode and parameters, the average NH4+-N and TN removal efficiency could respectively reach 100% and 70.8% under the NLR of 0.2 kg N·m−3·d−1 (COD/N of 3), which was the highest among the published works using SND-based SBBRs in treatment of saline high-strength ammonia nitrogen (low COD/N) wastewater. This study provided new insights in biofilm under hypersaline stress and provided a solution for the treatment of hypersaline high-strength nitrogen (low COD/N) water.

Conversion behavior of heterotrophic nitrification - aerobic denitrification bacterium Paracoccus denitrificans HY-1 in nitrogen and phosphorus removal

The heterotrophic nitrification-aerobic denitrification (HN-AD) bacteria harbored remarkable removal capacity in eliminating single nitrogen pollutant, but their comprehensive performance in dealing with mixed nitrogen sources remained unknown. In this study, the denitrification capacity of HN-AD bacteria Paracoccus denitrificans HY-1 was explored through whole-genome sequencing and nitrogen metabolic pathway analysis, and the complex nitrogen sources with gradient concentration were used to validate its nitrogen removal efficiency under both aerobic and anaerobic conditions. The results demonstrated that strain HY-1 harbored an efficient degradation capacity on three nitrogen sources, and the removal rates of NH4+-N, NO2−-N and NO3−-N were 10.67 mg·L−1·h−1, 27.81 mg·L−1·h−1, and 22.05 mg·L−1·h−1, respectively. The denitrification rate of 15.33 mg·L−1·h−1 was obtained under anaerobic condition with mixed nitrogen sources. Also, the simultaneous nitrification denitrification phosphorus removal (SNDPR) trial revealed that strain HY-1 could eliminate PO43−-P with a rate of 0.38 mg·L−1·h−1 under coexistence condition of the three nitrogen sources. Combined with the nitrogen balance analysis, the results indicated that strain HY-1 possesses a great potential for application in complex nitrogen and phosphorus contaminated environments.

Effects of carbon to nitrogen ratio on nitrogen removal in a single-stage microaerobic system: A model-based evaluation

Single-stage microaerobic systems have been proven to be effective for concurrent removal of ammonium and organic carbon from sewage. While mechanistic models derived from activated sludge models (ASMs) have simulated nutrients removal under microaerobic conditions, classic ASMs exhibit limitations in capturing the intricate effects of carbon to nitrogen (C/N) ratio on nitrogen removal performance. To address this issue, a mechanistic model modified from the classic ASMs was proposed to capture the combined inhibitory effects of carbon and ammonium on microaerobic systems. This modified model was established based on experimental data from a single-stage microaerobic reactor encompassing simultaneous nitrification-denitrification and anammox processes. The inhibition coefficient of C/N ratio was integrated into the process rate equations, and its effectiveness was validated through model performance evaluation. Compared to the classic models, the modified one achieved superior predictions for nitrite and nitrate nitrogen concentrations. Simulations revealed that under optimized conditions with a C/N of 4.57 and a dissolved oxygen (DO) of 0.41 mg/L, the system could achieve up to 95.5% of total nitrogen (TN) removal efficiency. Based on the simulation of substrate uptake/production rate, increasing the nitrogen loading rate (NLR) rather than organic loading rate (OLR) was crucial for efficient nitrogen removal. The proposed modified model served as a valuable tool for designing and optimizing similar biological wastewater treatment systems.

Experimental investigation of simultaneous nitrification-denitrification and phosphorus removal in pilot-scale sequencing batch moving bed biofilm reactors (SB-MBBRs)

Sequencing batch moving bed biofilm reactors have been widely used in commercial wastewater treatment facilities for organic carbon and nitrogen removal. However, these reactors can remove low phosphorus (P) levels. Therefore, this study investigated the potential of SB-MBBRs for maximizing simultaneous nitrification-denitrification and P removal (SNDPR) potential from P-rich municipal wastewater impacted by industrial discharges. A series of experiments were carried out to investigate the effect of external volatile fatty acid (VFA) dosing, airflow rate, and temperature on SNDPR using pilot-scale SBMBBRs. Stable and robust SNDPR was achieved with an optimum acetic acid supply of 150 mg SCOD/L, at 20 oC and 2.5 L air/min. A low airflow rate (AFR) and high-temperature conditions affected P release and uptake kinetics. Efficient PHA storage, dissolved oxygen (DO) transfer (outer layer), DO diffusion limitation (inner layer) of biofilm, and conversion of NH4-N to NO2-N/NO3-N enhanced SNDPR in the two pilot SB-MBBRs.

Stable partial nitrification was achieved for nitrogen removal from municipal wastewater by gel immobilization: A pilot-scale study

As an energy and carbon saving process for nitrogen removal from wastewater, the partial nitrification and denitrification process (PN/D) has been extensively researched. However, achieving stable PN in municipal wastewater has always been challenging. In this study, a gel immobilized PN/D nitrogen removal process (GI-PN/D) was established. A 94d pilot-scale experiment was conducted using real municipal wastewater with an ammonia concentration of 43.5 ± 5.3 mg N/L at a temperature range of 11.3–28.7℃. The nitrogen removal performance and associated pathways, shifts in the microbial community as well as sludge yield were investigated. The results were as follows: the effluent TN and COD were 0.6 ± 0.4 mg/L and 31.1 ± 3.8 mg/L respectively, and the NAR exceeding 95 %. GI-PN/D achieved deep nitrogen removal of municipal wastewater through stable PN without taking any other measures. The primary pathways for nitrogen removal were identified as denitrification, simultaneous nitrification-denitrification, and aerobic denitrification. High-throughput sequencing analysis revealed that the immobilized fillers facilitated the autonomous enrichment of functional bacteria in each reactor, effectively promoting the dominance and stability of the microbial communities. In addition, GI-PN/D had the characteristic of low sludge yield, with an average sludge yield of 0.029 kg SS/kg COD. This study provides an effective technical for nitrogen removal from municipal wastewater through PN.

Nitrogen removal and carbon reduction of mature landfill leachate under extremely low dissolved oxygen conditions by simultaneous partial nitrification anammox and denitrification

In this study, a SNAD-SBBR process was implemented to achieve ammonia removal and carbon reduction of mature landfill leachate under extremely low dissolved oxygen conditions (0.051 mg/L) for a continuous operation of 266 days. The process demonstrated excellent removal performance, with ammonia nitrogen removal efficiency reaching 100 %, total nitrogen removal efficiency reaching 87.56 %, and an average removal rate of 0.180 kg/(m3·d). The recalcitrant organic compound removal efficiency reached 34.96 %. Nitrogen mass balance analysis revealed that the Anammox process contributed to approximately 98.1 % of the nitrogen removal. Candidatus Kuenenia achieved a relative abundance of 1.49 % in the inner layer of the carrier. In the SNAD-SBBR system, the extremely low DO environment created by the highly efficient partial nitrification stage enabled the coexistence of AnAOB, denitrifying bacteria, and Nitrosomonas, synergistically achieving ammonia removal and carbon reduction. Overall, the SNAD-SBBR process exhibits low-cost and high-efficiency characteristics, holding tremendous potential for landfill leachate treatment.

New insights into substrates shaped nutrients removal, species interactions and community assembly mechanisms in tidal flow constructed wetlands treating low carbon-to-nitrogen rural wastewater

A limited understanding of microbial interactions and community assembly mechanisms in constructed wetlands (CWs), particularly with different substrates, has hampered the establishment of ecological connections between micro-level interactions and macro-level wetland performance. In this study, CWs with distinct substrates (zeolite, CW_A; manganese ore, CW_B) were constructed to investigate the nutrient removal efficiency, microbial interactions, metabolic mechanisms, and ecological assembly for treating rural sewage with a low carbon-to-nitrogen ratio. CW_B showed higher removal of ammonia nitrogen and total nitrogen by about 1.75–6.75 % and 3.42–5.18 %, respectively, compared to CW_A. Candidatus_Competibacter (denitrifying glycogen-accumulating bacteria) was the dominant microbial genus in CW_A, whereas unclassified_f_Blastocatellaceae (involved in carbon and nitrogen transformation) dominated in CW_B. The null model revealed that stochastic processes (drift) dominated community assembly in both CWs; however, deterministic selection accounted for a higher proportion in CW_B. Compared to those in CW_A, the interactions between microbes in CW_B were more complex, with more key microbes involved in carbon, nitrogen, and phosphorus conversion; the synergistic cooperation of functional bacteria facilitated simultaneous nitrification-denitrification. Manganese ores favour biofilm formation, increase the activity of the electron transport system, and enhance ammonia oxidation and nitrate reduction. These results elucidated the ecological patterns exhibited by microbes under different substrate conditions thereby contributing to our understanding of how substrates shape distinct microcosms in CW systems. This study provides valuable insights for guiding the future construction and management of CWs.

Microbial synergy achieving simultaneous nitrification-denitrification (SND) in salt-tolerant aerobic granular sludge

The adaptation of microbial community is vital for the potential use of aerobic granular sludge (AGS) as a technology for high-salinity wastewater. Although AGS has dense microbial aggregates and excellent settling ability, it requires a long adaptation period and may become unstable when exposed to salt stress. This study investigated the adaptation process of microbial community in salt-tolerant AGS (S-AGS) reactors to identify core microbes and their synergistic action during the AGS adaptation period. Compared to the control groups (R1, municipal sludge; R2, industrial sludge), the S-AGS (R3, mixed sludge) was quickly formed within 30 days and maintained with good structural stability (integrity coefficient > 0.95, particle size > 1200 μm) and high removal efficiency to COD (>90 %) and TN (>78 %). The core community of S-AGS in R3 was dominated by Thauera spp. and Pseudofulvimonas spp., while Rhodobacter spp. and Flavobacterium spp. were significantly inhibited during high salt stress. Co-occurrence network analysis revealed that Thauera spp. and Pseudofulvimonas spp. were the essential modules for S-AGS. The RT-qPCR results indicated that a higher level of nitrogen metabolism-related genes (nxrB, napA) ensured the functional potential of simultaneous nitrification-denitrification (SND). Furthermore, the results of microbial community analysis indicated that microbial synergy via enhancing ion transport and tryptophan secretion played a vital role in resisting the salt stress of AGS. This study provided a deeper insight into the stable development of S-AGS through microbial synergy, thereby providing practical implications for the saline wastewater treatment.

Research progress of anaerobic ammonium oxidation (Anammox) process based on integrated fixed-film activated sludge (IFAS).

The integrated fixed-film activated sludge (IFAS) process is considered one of the cutting-edge solutions to the traditional wastewater treatment challenges, allowing suspended sludge and attached biofilm to grow in the same system. In addition, the coupling of IFAS with anaerobic ammonium oxidation (Anammox) can further improve the efficiency of biological denitrification. This paper summarises the research progress of IFAS coupled with the anammox process, including partial nitrification anammox, simultaneous partial nitrification anammox and denitrification, and partial denitrification anammox technologies, and describes the factors that limit the development of related processes. The effects of dissolved oxygen, influent carbon source, sludge retention time, temperature, microbial community, and nitrite-oxidising bacteria inhibition methods on the anammox of IFAS are presented. At the same time, this paper gives an outlook on future research focus and engineering practice direction of the process.

Simulation assisted process simplification and energy recovery from a cryptic biological nutrient removal plant

In this study, simulation-based analysis is conducted for nitrogen removal mechanism in a biological nutrient removal plant designed in an encrypted manner. In the first phase, the simulation study elucidates how nitrogen removal occurs in a complex design using a series of 4 carousel bioreactors with additional nitrate recycle. It is demonstrated that pre-anoxic volume fed with limited internal recirculation only would not be sufficient to meet the discharge Total Nitrogen (TN) limit of 10 mg N/L. However, the addition of simultaneous nitrification-denitrification (SND) processes in aerobic reactors enables compliance with TN discharge limits. In the second phase, the configuration is simplified by means of process simulation, where the complex design is streamlined by eliminating internal recycle while achieving nitrogen removal through the SND process. Plant data confirmed that the simplified configuration can achieve nitrogen removal providing the same discharge quality. The simulations resulted that TN concentration achieved at the plant effluent is comparable, while effluent total phosphorus concentration is decreased by approximately 50 % due to increased activity of Phosphorus Accumulating Organisms (PAOs) under reduced sludge retention time (SRT). In the third phase, the application of the SND process in the field using a simplified and new activated sludge configuration yields similar results to the simulation. According to plant records, 28 % energy savings and an equivalent chemical cost reduction of €945,000 per year were achieved with the new process configuration.

Lumen air pressure regulated multifunctional microbiotas in membrane-aerated biofilm reactors for simultaneous nitrogen removal and antibiotic elimination from aquaculture wastewater

In this study, two membrane-aerated biofilm reactors (MABRs) were constructed: one solely utilizing biofilm and another hybrid MABR (HMABR) incorporating both suspended-sludge and biofilm to treat low C/N aquaculture wastewater under varying lumen air pressure (LAP). Both HMABR and MABR demonstrated superior nitrogen removal than conventional aeration reactors. Reducing LAP from 10 kPa to 2 kPa could enhance denitrification processes without severely compromising nitrification, resulting in an increase in total inorganic nitrogen (TIN) removal from 50.2±3.1 % to 71.6±1.0 %. The HMABR exhibited better denitrification efficacy than MABR, underscoring its potential for advanced nitrogen removal applications. A decline in LAP led to decreased extracellular polymeric substance (EPS) production, which could potentially augment reactor performance by minimizing mass transfer resistance while maintaining microbial matrix stability and function. Gene-centric metagenomics analysis revealed decreasing LAP impacted nitrogen metabolic potentials and electron flow pathways. The enrichment of napAB at higher LAP and the presence of complete ammonia oxidation (Comammox) Nitrospira at lower LAP indicated aerobic denitrification and Comammox processes in nitrogen removal. Multifunctional microbial communities developed under LAP regulation, diversifying the mechanisms for simultaneous nitrification-denitrification. Increased denitrifying gene pool (narGHI, nirK, norB) and enzymatic activity at a low LAP can amplify denitrification by promoting denitrifying genes and electron flow towards denitrifying enzymes. Sulfamethoxazole (SMX) was simultaneously removed with efficiency up to 80.2 ± 3.7 %, mainly via biodegradation, while antibiotic resistome and mobilome were propagated. Collectively, these findings could improve our understanding of nitrogen and antibiotic removal mechanisms under LAP regulation, offering valuable insights for the effective design and operation of MABR systems in aquaculture wastewater treatment.

Simultaneous aerobic nitrogen and phosphate removal by Pseudomonas aeruginosa SNDPR-01: Comprehensive insights on metabolic potential and mechanisms

Versatile metabolic bacteria with simultaneous nitrification–denitrification and phosphate removal (SNDPR) capabilities are promising to reduce the wastewater treatment process from a multi-unit system to a single unit system. Due to the limited study, the metabolic potential and mechanisms of nitrogen (N) and phosphate (P) removal for any SNDPR bacteria remain unknown. In this study, genomic analysis revealed various genes were present in an SNDPR isolate, Pseudomonas aeruginosa SNDPR-01, establishing diverse N- and P-metabolism potential, such as aerobic and anoxic denitrification; dissimilatory nitrate reduction to ammonia; polyphosphate (polyP) metabolism; and utilization of organic P. Phylogenetic analysis predicted that key functional genes related N and P metabolism may co-evolve with chromosomal genes, except for the norB gene, which may originate from horizontal gene transfer. Transcriptomic analysis revealed a partial nitrification and denitrification pathway (NH4+ → NO2– → NO → N2O → N2) to aerobically remove N without the involvement of conventional amoA, hao and napA genes. Unknown genes were confirmed to mediate the oxidation of ammonium to nitrite. Excellent P removal ability was aided by the synthesis of adenosine triphosphate (ATP) and polyP. The formed polyP was utilized under aerobic conditions without accumulation, which is different from traditional polyP accumulation organisms in wastewater treatment plants (WWTPs). This study will deepen the roles of SNDPR bacteria in aerobic ecological niches and enhance their application in WWTPs.

An advanced control system for nitrogen removal and energy consumption optimization in full-scale wastewater treatment plants

The development and implementation of advanced control systems enable the successful and efficient conversion of wastewater treatment plants into water resource recovery facilities. This work presents an advanced control system based on low-cost sensors (pH, ORP and DO) which enhances biological nitrogen removal and improves energy efficiency. It consists of three independent fuzzy-logic-based control loops (for nitrification, simultaneous nitrification-denitrification, and denitrification, respectively) combined with a set of knowledge-based rules. The control system was implemented in three facilities and test-run for over two years. During this time, proper process performances were achieved both in terms of water quality and of operating cost savings. Energy consumption, calculated as kWh per kg COD equivalent removed (including nitrogen removal), was reduced between 14 % and 33 %.

Enhancing nitrogen removal from wastewater in a low C/N ratio using an air-lift bio-electrochemical reactor (ALBER)

This study focuses on the development of an air-lift bio-electrochemical reactor (ALBER) with a continuous feeding regime. The objective is to enhance nitrogen removal from synthetic wastewater with a low carbon-to-nitrogen (C/N) ratio. The chemical oxygen demand (COD) and total nitrogen (TN) of the influent wastewater were 500 and 200 mg/L, respectively. The effect of four independent variables, i.e., temperature, hydraulic retention time (HRT), N−NH4+/TN ratio and current density in the range of 16–32 °C, 6–12 h, 25–75%, and 2–10 A/m2, respectively, at three levels on the bio–electrochemical reactor performance were investigated during the bio–electrochemical reactor operation. The Face Center Cube (FCC) of response surface methodology (RSM) was used for design of experiments and model of obtained data. The ALBER achieved the maximum TN removal of 73% (146 mg/l) using external voltage and zeolite/plastic medium at temperature of 16 °C, HRT of 6 h, current density of 2 A/m2 and N−NH4+/TN ratio of 75%. The results indicated that shortening the HRT from 12 to 6 h, reducing the temperature from 32 °C to 24 °C, increasing the current density from 2 to 6 A/m2 and the reduction of nitrate concentration caused an increase in the TN removal. The results indicated that the performance of air-lift bio-electrochemical for nitrogen removal could be attributed to autotrophic denitrification (AD) and simultaneous nitrification/denitrification (SND). The research findings suggest that the ALBER should be further studied for potential use in treating industrial wastewater at low temperatures.

Nitrogen removal from pharmaceutical wastewater using simultaneous nitrification–denitrification coupled with sulfur denitrification in full-scale system

Fermentation pharmaceutical wastewater (FPW) containing excessive ammonium and low chemical oxygen demand (COD)/nitrogen ratio (C/N ratio) brings serious environmental risks. The stepwise nitrogen removal was achieved in a full-scale anaerobic/aerobic/anoxic treatment system with well-constructed consortia, that enables simultaneous partial nitrification–denitrification coupled with sulfur autotrophic denitrification (SPND-SAD) (∼99 % (NH4+-N) and ∼98 % (TN) removals) at the rate of 0.8–1.2 kg-N/m3/d. Inoculating simultaneous nitrification–denitrification (SND) consortia in O1 tank decreased the consumed ΔCOD and ΔCOD/ΔTN of A1 + O1 tank, resulting in the occurrence of short-cut SND at low C/N ratio. In SAD process (A2 tank), bio-generated polysulfides reacted with HS− to rearrange into shorter polysulfides, enhancing sulfur bioavailability and promoting synergistic SAD removal. PICRUSt2 functional prediction indicated that bioaugmentation increased genes related to Nitrogen/Sulfur/Carbohydrate/Xenobiotics metabolism. Key functional gene analysis highlighted the enrichment of nirS and soxB critical for SPND-SAD system. This work provides new insights into the application of bioaugmentation for FPW treatment.

Simultaneous nitrification/denitrification in a single-chamber stainless steel bioelectrochemical reactor

The removal of nitrogen from wastewater with a low C/N ratio often requires additional carbon sources to address the shortage of electron donors, which increases the cost. We explored a simple and energy effecient means for treating wastewater with a high concentration of ammonia nitrogen under anoxic conditions without the addition of carbon sources. We constructed a stainless steel tube as an anaerobic single-chamber microbial electrolysis cell (MEC) for investigating autotrophic simultaneous nitrification/denitrification (SND). Two different structures (carbon brush vs. stainless-steel) were used to construct biocathodes and compared their performances under different voltages (1.8 V, 1.5 V, 1.2 V) applied by DC power. When voltage was applied at 1.5 V, the removal rates of TN and NH4+-N reached 19.68 ± 0.02 mg L−1 d−1 and 21.04 ± 0.17 mg L−1 d−1, respectively. Simultaneously, it achieved maximum TN and NH4+-N removal over 14 days (44.97 ± 0.28 %, 48.16 ± 0.32 %). These rates were 1.8 and 5 times of that obtained with the conventional carbon brush electrode and open-circuit control. Furthermore, microbial community and SEM analysis indicate that species of Thermomonas, Thibacillus and Thauera were the predominant autotrophic electroactive denitrifying bacteria in the reactors. Overall, we achieved a high rate of nitrogen removal, electron utilization and energy recovery in a single-chamber stainless steel MEC.

Biomass yield characteristics and removal kinetic model construction with mass transfer optimization of a moving bed and constructed wetland (MBCW) integrated bioreactor

The degradation of pollutants in a moving bed and constructed wetland (MBCW) integrated bioreactor depended on rich microbial diversity and complex community structure. Sludge yield characteristics showed this system had an advantage on sludge decrement. Removal of pollutants was mainly through a simultaneous nitrification denitrification and further denitrification (SND-DN) process, according to the analysis of removal mass balance and contribution. Based on the fluidization characteristics of mixed biocarriers, the overall first-order kinetic model of MBCW system was constructed. The comparison between theoretical and measured values proved the kinetic model of CODCr, NH3-N and TN removal was validated.

Evaluación de la tasa de utilización de sustratos orgánicos y nitrogenados por los microorganismos en un reactor discontinuo secuencial

In this article, the utilization rate of organic and nitrogenous substrates contained in tannery wastewater by a sequential batch reactor is evaluated. Two factorial experimental designs (FEDs) were implemented. FED1 (22) used granular biomass, the aeration sequence (oxic, anaerobic-oxic) and cycle duration (6 and 24 h). FED2 (4 x 3) included suspended biomass, reaction phases (anoxic I, oxic, anoxic II (CND: conventional nitrification-denitrification) and (SND: simultaneous nitrification-denitrification), filling time (fast, slow and in stages). The substrates examined were chemical oxygen demand (COD), ammonium (NH4+-N) and total nitrogen Kjeldahl (TKN). The utilization rates were COD (-100 and -200 mg l-1 h-1) (FED1) and (-48 and -75 mg l-1 h-1) (FED2), being 1.5 to 2 times higher in FED1 than FED2. In TKN (-5 mg l-1 h-1), and NH4+-N (-30 mg l-1 h-1), they were significant in the anoxic I and oxic phases.

Evaluating the Effect of Nonaerobic Hydraulic Retention Time on Nutrients Removal in Nonaerobic and Aerobic SBR

The nonaerobic stage is critical for the processes of denitrification and phosphorus release in biological wastewater treatment. A lab-scale sequencing batch reactor (SBR) operating as nonaerobic/aerobic was used to treat synthetic wastewater, and the nutrients removal performance was investigated under different nonaerobic hydraulic retention times (HRTs). The results showed when the nonaerobic HRT changed from 0 to 4 h with constant aerobic HRT of 8 h [dissolved oxygen (DO) 0.50–1.50 mg·L−1], the removal efficiencies of PO43−─P and NH4+─N were all above 90.00%, respectively. The nonaerobic HRT could influence carbon utilization between denitrification and phosphorus release, which showed a close relationship with the ratio of consumed chemical oxygen demand (COD)phosphorus release to CODdenitrification (0.94). Specifically, the consumed CODphosphorus release increased with the increase of nonaerobic HRT (0.90), whereas the relationship between consumed CODdenitrification and nonaerobic HRT was limited (−0.60). Furthermore, internal carbon source produced through phosphorus release could promote simultaneous nitrification denitrification. This control strategy could be conveniently applied in intermittent-flow sewage treatment plant through adjusting nonaerobic HRT.