Wastewater Nitrogen Removal Research Articles

Simultaneous removal of ammonia nitrogen and sulfide by coupled anammox and sulfur autotrophic denitrification process from industrial wastewater

This work presents an experimental study on the coupling between anammox and sulfur autotrophic denitrification for simultaneous removal of ammonia nitrogen and sulfide in industrial wastewater, leading to less environmental pollution. In a low-load continuous operation mode hybrid anaerobic baffled reactor (HABR) was started with 7 <pH<8.2 and temperature 30–35 °C. After 60 d of continuous operation successful enrichment of methanogenic granular sludge (MGS) size 7 and 5 mm was achieved. In the mature granular sludge phase (HRT 10 h), with influent chemical oxygen demand (COD) 1100 mg/L, the effluent COD 90 mg/L and removal efficiency was 90%. The MLSS, MLVSS, and f values were 9520, 6980, and 0.7. After 42 d of continuous operation with influent COD 600–700 mg/L, NO3−-N 250-300 mg/L, and COD/NO3−-N 2 to 2.8 (temperature 30–35 °C and pH 6.5–7.5) successful enrichment of denitrifying granular sludge (DGS) was achieved. In the research, the anammox start-up periods in MGS and DGS reactors are 86 and 118 d. An experimental comparative analysis to explore the influence of COD/TN 1:1,1:1.8,1:4.5, and 1:8.5 on the two reactors was performed. For COD/TN 1:1.8, the NH4+-N, NO2−-N, and TN removal efficiency were 54%, 73%, and 52%. The removal efficiency of the #2 reactors NH4+-N, NO2−-N, and TN were 50%, 60%, and 55%. S2−/NO3−-N of 2:5, 3.5:5, 5:5, 6.5:5 were investigated. Influent pH 7.5–8.0, temperature 30–35 °C and HRT 6.5 h, with average influent NH4+-N, NO3−-N, S2−, COD concentration 60, 25, 75, and 25 mg/L, the maximum removal efficiency of #1 reactor was 70%, 97%, 82%, and 100%. For 2# reactor 82%, 99%, 84%, and 100%. When MGS as carrier, the NH4+-N, NO3−-N, and S2− removal efficiency reached 67.67%, 98.59%, and 99.1%. With DGS as carrier, the NH4+-N, NO3−-N, and S2− removal efficiency reached 81.82%, 98.69%, and 84.18%. However, the coupling phase S0 production and productivity results showed that the DGS reactor was significantly better than the MGS reactor. Under the same hydraulic conditions the two reactors successfully coupled after 54 d of operation. Additionally, polymerase chain reaction denaturing gradient gel electrophoresis (PCR-DGGE) analysis, revealed that the microbial community change is related to the concentration of organic matter, nitrogen and sulfur in the water. Building on these findings, future study will focus on the optimization of the mix design to provide practical engineering guidance.

Study on enhanced nitrogen removal of caprolactam production wastewater

Caprolactam (CPL) is widely used in polymer material and engineering plastics synthesis. The CPL production wastewater is difficult to treat due to high chemical oxygen demand (COD) and ammonia nitrogen (NH3-N), complex components and poor biodegradebility. The common treatment method for this wastewater is biochemical treatment combined with physicochemical pretreatment. Though the NH3-N of effluent can decrease to 1 mg/L, total nitrogen (TN) usually is above 100 mg/L. Herein, the enhanced nitrogen removal way was studied. The results showed TN was mainly composed of nitrate nitrogen which the concentration was approximately 90 mg/L via traditional A/O process. A simulated A/O/A process with methanol addition was investigated and TN of the effluent was below 20 mg/L, indicating this process with carbon source is efficient for advanced nitrogen removal.

Effect of phosphorylated polyvinyl alcohol matrix size of cell entrapment on partial nitrification of ammonia in wastewater

ABSTRACT Partial nitrification is known as first and critical step for autotrophic nitrogen removal in high strength nitrogenous wastewater. Phosphorylated polyvinyl alcohol gel entrapment was used for suppressing oxygen to nitrite-oxidizing bacteria (NOB) in the gel matrix. The study investigated the effect of the size of gel matrix on partial nitrification. Results show that ammonia-oxidizing bacteria (AOB) proportion in the inoculum rather than the size of gel matrix governed ammonia oxidation. Nitrite oxidation depended on the size of gel matrix not the relative proportions of NOB and AOB in the inoculum. Larger size of gel matrix lead to less in situ oxygen penetration and available for NOB resulting in higher nitrite accumulation. This finding gains a better understanding of using suitable inoculum to control partial nitrification that is beneficial for the preparation of anaerobic ammonium oxidation-suited effluent.

Fermentation liquid as a carbon source for wastewater nitrogen removal reduced nitrogenous disinfection byproduct formation potentials of the effluent

Sludge alkaline fermentation liquid (SAFL) is an alternative to sodium acetate (NaAc) in enhancing wastewater nitrogen removal. Upon SAFL addition, dissolved organic nitrogen (DON) can be externally introduced or biologically synthesized during nitrogen removal, which is an important precursor to toxic nitrogenous disinfection by-products (N-DBPs). This study aims to evaluate the effects of different carbon source addition on effluent DON concentration, composition, and N-DBP formation potentials. A lab-scale A2O system treating real municipal wastewater was operated with NaAc or SAFL as external carbon sources. DON molecules and potential N-DBP precursors were identified by Orbitrap mass spectrometry. Subsequently, major microorganisms contributing to DON biosynthesis were suggested based on metagenomics. It was found that effluent DON was higher with SAFL as the carbon source than NaAc (1.51 ± 0.24 v.s. 0.56 ± 0.08 mg N/L, p < 0.05). Nevertheless, dichloroacetonitrile and nitrosamine formation potentials (7.14 ± 1.02 and 1.57 ± 0.07 μg/mg DON-N, respectively) of the effluent with SAFL addition were 42.79 ± 2.42% and 54.89 ± 1.70% lower than those of NaAc. Protein- and lignin-like compounds were the most abundant DON molecules in the effluent, where alanine, glycine and tyrosine were important precursors to N-DBPs. Azonexus and Flavobacterium spp. were positively correlated with these precursors, and possessed key genes involved in precursor synthesis. SAFL is a promising carbon source, not only for achieving efficient inorganic nitrogen and DON removals, but also for reducing N-DBP formation potentials of chlorinated effluent.

Hotspots and trends of biological water treatment based on bibliometric review and patents analysis

In order to reveal the hotspots and trends of biological water treatment from the perspectives of scientific and technological innovation, both of the bibliometric review and patents analysis were performed in this study. The Web of Science Core Collection database and Derwent Innovation Index database recorded 30023 SCI papers and 50326 patents, respectively were analyzed via information visualization technology. The results showed that China ranked the first in both papers and patents, while the United States and Japan had advantages in papers and patents, respectively. It was concluded through literature metrology analysis that microbial population characteristics, biodegradation mechanism, toxicity analysis, nitrogen and phosphorus removal and biological treatment of micro-polluted wastewater were the research hotspots of SCI papers. Activated sludge process and anaerobic-aerobic combined process were the two mainstream technologies on the basis of patent technology classification analysis. Technology evolution path of biological water treatment was also elucidated in three stages based on the citation network analysis. Furthermore, the future directions including research on the law of interaction and regulation of biological phases and pollutants and the technology innovations towards the targeted biotransformation or selective biodegradation of pollutants and resource reuse of wastewater were prospected.

Recent Advances in Autotrophic Biological Nitrogen Removal for Low Carbon Wastewater: A Review

Due to carbon source dependence, conventional biological nitrogen removal (BNR) processes based on heterotrophic denitrification are suffering from great bottlenecks. The autotrophic BNR process represented by sulfur-driven autotrophic denitrification (SDAD) and anaerobic ammonium oxidation (anammox) provides a viable alternative for addressing low carbon wastewater. Whether for low carbon municipal wastewater or industrial wastewater with high nitrogen, the SDAD and anammox process can be suitably positioned accordingly. Herein, the recent advances and challenges to autotrophic BNR process guided by SDAD and anammox are systematically reviewed. Specifically, the present applications and crucial operation factors were discussed in detail. Besides, the microscopic interpretation of the process was deepened in the viewpoint of functional microbial species and their physiological characteristics. Furthermore, the current limitations and some future research priorities over the applications were identified and discussed from multiple perspectives. The obtained knowledge would provide insights into the application and optimization of the autotrophic BNR process, which will contribute to the establishment of a new generation of efficient and energy-saving wastewater nitrogen removal systems.

Simultaneous high-concentration pyridine removal and denitrification in an electricity assisted bio-photodegradation system

In this study, enhanced degradation of high-concentration pyridine and simultaneous denitrification were achieved in an Electricity assisted bio-photodegradation system (EBPS) with a photoanode zone, a biocathode zone and an aerobic zone. The recombination of photoelectron-hole pairs was significantly suppressed in EBPS, which could not only improve the pyridine oxidation in photoanode zone, but also accelerate the biodegradation process in biocathode zone. NH4+ produced from pyridine degradation could be effectively nitrified into NO2- and NO3- in aerobic zone, which was recirculated into biocathode zone to serve as electron acceptor for accelerating pyridine biodegradation. When influent pyridine concentration was as high as 1250 mg L-1, pyridine was completely degraded without adding any extra electron donors, and complete denitrification was achieved in biocathode zone. Microbial community analysis confirmed the enrichment of the pyridine biodegradation species (Rhodococcus, Hydrogenophaga, Truepera and Thermovirga), denitrification species (Thiobacillus, Thioalkalispira and Rhodococcus) and electroactive species (Thiobacillus, Thermovirga, Hydrogenophaga, Thioalkalispira and Rhodococcus). Furthermore, the mechanism of pyridine metabolism, denitrification and extracellular electron transfer processes in EBPS was investigated, utilizing Phylogenetic Investigation of Communities by Reconstruction of Unobserved States 2 (PICRUSt2). The results showed that the genes involved in pyridine degradation, denitrification and extracellular electron transfer were remarkably enriched in EBPS, indicating the crucial role of photoelectrical stimulation. This study provided a sustainable technical approach for simultaneous removal of pyridine and nitrogen in wastewater.

Fe-C Wrapped in Polyurethane Sponge Cubes Tied in Anoxic Zones to Enrich Multiple Denitrifying Bacteria Enhancing Wastewater Nitrogen Removal

Fe-C Wrapped in Polyurethane Sponge Cubes Tied in Anoxic Zones to Enrich Multiple Denitrifying Bacteria Enhancing Wastewater Nitrogen Removal

Ammonia assimilation: A double-edged sword influencing denitrification of Rhodobacter azotoformans and for nitrogen removal of aquaculture wastewater

NO3−-N and NH4+-N are two prevalent nitrogenous pollutants in aquaculture wastewater posing a significant health risk to aquatic animals. R. azotoformans ATCC17025 can rapidly denitrify to remove NO3−-N, assimilating NH4+-N. The study investigated the influence of ammonia assimilation on bacterial denitrification. Results revealed that low concentration of NH4+-N (≤0.3 mM) accelerated denitrification, whereas high concentration inhibited it. RT-qPCR indicated that the inhibition of NO reduction under high concentration of NH4+-N was the primary cause of denitrification depression, whereas low concentration of NH4+-N enhanced the synthesis of practically all enzymes involved in denitrification. Finally, nitrogen-rich aquaculture effluent was effectively treated in lab-scale using a semi-continuous operation that provided an appropriate NH4+-N concentration for denitrification. This semi-continuous operation treated wastewater 2 times faster than the batch operation and the content of nitrogen decreased to effluent standard. The study can provide guidance for nitrogen removal of aquaculture wastewater with bioaugmentation.

Biodegradation of tetramethylammonium chloride wastewater and inorganic nitrogen removal by a mixed culture

The disposal of wastewater containing tetramethylammonium chloride (TMAC) generated from the semiconductor and photoelectric industries is a challenging problem due to the limited information is available regarding its treatability. This study aims to investigate the feasibility of using biological processes to treat TMAC. An activated sludge collected from a lake near the Southern Taiwan Science Park was used. Various operational parameters, including operating temperature, pH conditions and TMAC dosages were evaluated for the optimal condition. Results showed that the activated sludge could successfully degrade TMAC, and subsequently achieve simultaneous nitrification and denitrification (SND) of the nitrogen-containing intermediates under mild conditions (pH at a range of 3–7 and temperature at a range of 20–40 °C). Besides, more than 60% of the nitrogen-containing intermediates were converted into gaseous nitrogen (N2). TMAC biodegradation was found to follow first-order kinetics. The observed rate constant of TMAC biodegradation increased from 0.64 ╳ 10−4 to 9.57 ╳ 10−4 1/min as the concentration of TMAC decreased. In addition, TMAC demethylation was identified as the rate-limiting step of the entire reaction. Major functional organisms of the activated sludge were identified as Mycobacterium, Ochrobactrum and Arthrobacter species which are aerobic and acidophilic strains. This study can be an important reference for future researches attempting to treatment TMAC wastewater by biological processes.

The effect of time and velocity variation in sequencing batches reactor on TSS and nitrogen removal in tofu waste

The tofu industry is one of the home industries which in the processing process, produces liquid waste. Tofu liquid waste is known to contain very high organic matter such as Nitrogen and TSS so that if it is directly discharged into water bodies, if discharged directly into the environment will cause water. The purpose of this study was to determine and analyse the effect of variations in times and velocity of sequence batch reactor on the optimization of Nitrogen and TSS removal in tofu industrial wastewater by anaerobic bacteria originating from natural sediments. This study uses a Sequencing Batch Reactor, and the waste used is artificial by the characteristics in the preliminary test. In this study, time and speed variations were used in the mixing process. The artificial waste has a TSS value of 2,910 mg/l and Nitrogen of 18.82 mg/l. The results show that using a sequence batch reactor can reduce the TSS value to 66 mg/l and reduce the nitrogen value to 1.214 mg/l.

Green Roofs for domestic wastewater treatment: Experimental and numerical analysis of nitrogen turnover

The use of Green Roofs (GRs) for domestic wastewater treatment and nitrogen (N) removal is an appealing opportunity to conjugate hydrological, energetic, and water quality benefits. However, the research in this direction has been limited to few experimental studies, while the role of numerical modeling for analysis and design has been overlooked. To advance understating of reactive transport processes in GRs and investigate the use of numerical models, this study presents a comprehensive experimental and numerical investigation of the N turnover in vegetated and non-vegetated GRs exposed to domestic wastewater injection. A Bayesian framework is used to calibrate a mechanistic numerical model against multiple observations from a controlled laboratory experiment. A Global Sensitivity Analysis complements the framework to further enlighten the role of multiple physical processes. Results indicate that GRs have high nitrification capacity, which increases after wastewater application. The total leached N is 94% of the total injected N in a non-vegetated GR, compared to 67% for a vegetated GR. Nitrate leaching is negatively correlated with the root solute uptake capacity of the vegetation, which may reach up to 32% of the total injected N. Maximization of this factor is desirable and can be achieved by selecting appropriate plant species and reducing water stress periods using a proper irrigation schedule.

Advances in Studies on Microbiota Involved in Nitrogen Removal Processes and Their Applications in Wastewater Treatment.

The discharge of excess nitrogenous pollutants in rivers or other water bodies often leads to serious ecological problems and results in the collapse of aquatic ecosystems. Nitrogenous pollutants are often derived from the inefficient treatment of industrial wastewater. The biological treatment of industrial wastewater for the removal of nitrogen pollution is a green and efficient strategy. In the initial stage of the nitrogen removal process, the nitrogenous pollutants are converted to ammonia. Traditionally, nitrification and denitrification processes have been used for nitrogen removal in industrial wastewater; while currently, more efficient processes, such as simultaneous nitrification-denitrification, partial nitrification-anammox, and partial denitrification-anammox processes, are used. The microorganisms participating in nitrogen pollutant removal processes are diverse, but information about them is limited. In this review, we summarize the microbiota participating in nitrogen removal processes, their pathways, and associated functional genes. We have also discussed the design of efficient industrial wastewater treatment processes for the removal of nitrogenous pollutants and the application of microbiome engineering technology and synthetic biology strategies in the modulation of the nitrogen removal process. This review thus provides insights that would help in improving the efficiency of nitrogen pollutant removal from industrial wastewater.

Improved two-reactor system with sulfonated membranes in wastewater treatment

The ion exchange membrane bioreactor with two-reactor system has gained attention because it has been known to be beneficial to the simultaneous removal of organic and nitrogen. However, this system has a disadvantage for accumulation of nitrate in nitrification due to low diffusivity of nitrate through a cation exchange membrane. To resolve this problem, this study proposed a unique membrane bioreactor system bounded sulfonate membrane to be applied for simultaneous removal of organic and nitrogen in wastewater. The unique membrane bioreactor system consists of two reactors called reactors A and B. The reactor A was maintained in anoxic condition while the reactor B was operated in aerobic condition during the operation period. In ammonium migration experiment, the ammonium migration rates were determined by measuring ammonium concentrations in reactor A. As a result of the measurement, the maximum mass fluxes at the initial ammonia levels of 500, 1000, 1500, and 2000 mg N/L resulted in 1.03, 2.06, 2.98, and 3.87 mg/m2• s, respectively. Those high fluxes indicated that the unique membrane bioreactor exhibited high ion diffusivity. The mass fluxes of ammonia nitrogen in this system were strongly correlated to the initial concentrations of ammonia. The nitrate produced in the reactor B by biological nitrification was effectively migrated to the reactor A, and then the migrated nitrate in the reactor A was converted to nitrogen gas by denitrifying bacteria. As a result, almost complete nitrogen removal efficiency was achieved as 99% in the batch system. Further interestingly, no severe nitrate accumulation problem was observed in reactor B in the unique membrane bioreactor, although such a problem commonly exists in the conventional cation exchange membrane bioreactor system. It is expected that this unique membrane system can be operated with low operation costs and high removal efficiencies of ammonia nitrogen.

Micro-nano aeration is a promising alternative for achieving high-rate partial nitrification

Biological nitrogen removal is the most prevalent wastewater nitrogen removal process but nitrification limits the rate of the whole process mainly due to the low efficiency of oxygen transfer. In this study, clean-water oxygenation tests, batch tests, long-term operational tests and metagenomic analyses were applied to assess the effects of micro-nano aeration on nitrification. The oxygen transfer coefficient (KLa), oxygen transfer rate (OTR) and oxygen transfer efficiency (OTE) were determined to be 0.56 min−1, 0.36 kg·m−3·h−1 and 71.43%, respectively during micro-nano-bubble aeration. Impressively, these values were 15 times greater than those of conventional aeration. The results of batch tests and long-term operation experiments found that the ammonia removal rate of micro-nano aeration was 3.2-fold that of conventional aeration. The energy cost for micro-nano aeration was calculated to be 3694.5 mg NH4+-N/kW·h, a 50% energy saving in comparison to conventional aeration. In addition, the nitrite accumulation ratio in the Micro-nano (MN) reactor was 1.5 that of the Conventional (CV) reactor. Metagenomic analysis showed that after long-term operation in micro-nano aeration, the abundances of genes encoding ammonia monooxygenase (amoA) and hydroxylamine oxidoreductase (hao) was more than 8-fold and 4-fold of those in conventional aeration, respectively. The abundance of the gene encoding nitrite oxidoreductase (nxrA) was similar in both reactors. Read taxonomy revealed that abundance of AOB-Nitrosomonas increased significantly when using micro-nano aeration, while abundance of NOB-Nitrospira abundance was similar in both reactors. The results of this study indicated that the micro-nano aeration process will increase the ammonia oxidation performance by enhancing oxygen transfer but was also shown to be beneficial for enhancing partial nitrification by specific enrichment of ammonia oxidizing bacteria. This latter result demonstrates the potential benefits of the micro-nano aeration process as an alternative approach to establishing high-rate partial nitrification.

Nitrogen and phosphorus removal in simulated wastewater by two aquatic plants.

Water pollution control is the focus of environmental pollution control. Ecological water treatment is widely used because of its low cost and landscape effect, and has no pollution. Aquatic plants have attracted wide attention because of their low cost and high level of resource utilization. In order to study the effects of emergent and submerged plants on the removal of different concentrations of wastewater, and the effect of pollutants on plant growth, two common aquatic plants found in Northeast China (Iris ensata Thunb. and Potamogeton malaianus Miq.) were selected. Under static conditions, the removal efficiency of nitrogen and phosphorus in wastewater with different concentrations by two kinds of plants was studied. The results showed that the removal rate of total nitrogen (TN) in medium- and high-pollutant concentration water samples and total phosphorus (TP) in medium- and low-pollutant concentration water with I. ensata reached more than 75%. The removal rate of TN in the medium-pollutant concentration water with P. malaianus reached 71.4%, while the removal efficiency of TN and TP in the low-pollutant concentration water was higher than 80%. In the Nanhu Park Lake samples, I. ensata had the highest removal rates of TN (80.38%) and TP (85.62%). This study shows that both I. ensata and P. malaianus can be used as aquatic plants to restore the water quality of urban lakes. This research provides an important basis for the phytoremediation and treatment of urban domestic wastewater and urban surface water bodies in Northern China.

Performance Evaluation of Immobilized Microorganism for Nitrogen Removal in Wastewater Using EQPS

Performance Evaluation of Immobilized Microorganism for Nitrogen Removal in Wastewater Using EQPS

Lab-scale autothermal thermophilic aerobic digestion can maintain and remove nitrogen by controlling shear stress and oxygen supply system

Autothermal thermophilic aerobic digestion (ATAD) is used to treat human excreta hygienically. We previously reported a unique full-scale ATAD, showing distinctive bacterial community transitions and producing high-nitrogen-content liquid fertilizer; nevertheless, the mechanism remains unclear. One hypothesis involves using a gas-inducing (GI) agitator. We designed a lab-scale GI system and compared it with a disk-turbine (DT) agitator system by mimicking the temperature shift of full-scale ATAD. The agitation system and its agitation speed greatly affected physicochemical properties and bacterial community structure. GI system at 1000rpm (GI1000; high total carbon removal efficiency, 88.3%), with few nitrifying and denitrifying bacteria, maintained a high ammoniacal nitrogen concentration and had more shared operational taxonomic units related to Acinetobacter sp., Arcobacter sp., and Longimicrobium sp. with the full-scale ATAD compared with the GI system at 490rpm and DT system at 1000rpm (DT1000). Furthermore, DT1000, with a high abundance of nitrifying and denitrifying bacteria such as Alcaligenes aquatilis and Pseudomonas caeni, removed 94.7% total nitrogen with 71.9% total carbon removal efficiency. These results suggested that shear stress and oxygen supply system would change the bacterial community structure, thus affected ATAD performances. Consequently, it is possible that ATAD can be applied for not only production of highly nitrogen-containing liquid fertilizer but also extremely nitrogen removal of wastewater.

Anammox bacteria enrichment in fixed biofilm successfully enhanced nitrogen removal of domestic wastewater in a sequencing biofilm batch reactor (SBBR)

The feasibility of enhancing anammox enrichment in sewage treatment through fixed biofilm was investigated in this study. Two reactors were used to treat real domestic sewage and operated in an identical mode: one is a sequencing biofilm batch reactor (SBBR) with blank carriers and the other is a sequencing batch reactor (SBR) without carriers. After anammox sludge inoculation and 160 days' operation, the abundance of the anammox bacteria increased to 2.58 × 109 gene copies/g dry sludge in the biofilm of SBBR, but decreased to 8.18 × 107 gene copies/g dry sludge in the activated sludge of SBR. The nitrogen removal efficiency (NRE) of SBBR and SBR was 79.3% and 57.9%, respectively. Further analysis suggests that the partial nitrification was stabilized in SBBR due to the addition of carriers and the dominating nitrogen removal pathway was the anammox reaction. In general, the fixed biofilm effectively maintained and enriched the anammox bacteria, which benefitted the start-up and steady operation of the sewage partial nitrification anammox (PNA) process.

Life cycle assessment of electrodialysis for sidestream nitrogen recovery in municipal wastewater treatment

Nitrogen is removed during municipal wastewater treatment to reduce eutrophication of waterways and preserve drinking water quality. Nitrification-denitrification and sidestream partial nitrification-anammox are state-of-the-art municipal N removal technologies, but they require energy for aeration and can release nitrous oxide as a fugitive greenhouse gas. An emerging sidestream electrodialysis technology is intended to both remove and recover N as ammonium-based fertilizer. This midpoint life cycle assessment compiles literature values to compare the state-of-the-art technologies of municipal wastewater nitrogen removal to the new electrodialysis nitrogen removal and recovery technology, accounting for the offset of Haber-Bosch-derived ammonia. Electrodialysis is projected to be environmentally favorable compared to the state-of-the-art, predicting electricity savings similar to anammox and, with the offset of industrial ammonia manufacture, net negative emissions in five of ten midpoint environmental impact categories, including global warming potential.