•Novel approach for high-strength pharmaceutical wastewater by PD/A was confirmed.•PD/A biofilm was developed rapidly and had high tolerance to real wastewater.•Higher LB-EPS was produced with ...protein 3-turn helices structure was obtained.•Relatively stable TN removal efficiency of 81.2% was achieved with increasing load.•Thauera was highly enriched and dominated for partial NO3− reduction to NO2−.
Biological nitrogen removal from pharmaceutical wastewater has drawn increasing attention due to biotoxicity and inhibition. In this study, for the first time, a novel approach integrating partial-denitrification with anaerobic ammonia oxidation (PD/A) in a sequencing biofilm batch reactor (SBBR) was proposed and demonstrated to be efficient to treat the bismuth nitrate and bismuth potassium citrate manufacturing wastewater, containing ammonia (NH4+-N) and nitrate (NO3−-N) of 6300±50 mg L − 1 and 15,300±50 mg L − 1. The maximum anammox activity was found at the shock effect of influent total nitrogen (TN) of 100 mg L − 1 with NO3−-N/NH4+-N of 1.0. Long-term operation demonstrated that the PD/A biofilm was developed rapidly after 30 days using synthetic influent, with TN removal efficiency increasing from 40.9% to 80.8%. Significantly, the key bacteria for PD/A had high tolerance and adapted rapidly to pharmaceutical wastewater, achieving a relatively stable TN removal efficiency of 81.2% with influent NH4+-N and NO3−-N was 77.9 ± 2.6 and 104.1 ± 4.4 mg L − 1 at a relatively low COD/NO3−-N of 2.6. Anammox pathway contributed to TN removal reached 83.6%. Significant increase of loosely-bound extracellular polymeric substances was obtained with increasing protein of 3-turn helices structure as response to the inhibitory condition. High-throughput sequencing analysis revealed that the functional genus Thauera was highly enriched in both biofilms (9.5%→43.6%) and suspended biomass (15.5%→57.5%), which played a key role in high NO2−-N accumulation. While the anammox bacteria decreasing from 7.8% to 1.6% in biofilm, and from 1.8% decreased to 0.1% in the suspended sludge. Overall, this study provides a new method of high-strength pharmaceutical wastewater treatment with low energy consumption and operation cost, as well as a satisfactory efficiency.
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•Effluent TN as low as 4.0 mg N/L was achieved via PD-Anammox process.•Anammox was stable and accounted for 78.2% on nitrogen removal.•Low nitrous oxide (N2O) was produced in ...PD-Anammox process.•Oxygen consumption, COD demand and sludge production would be largely reduced.•PD-Anammox process can be easily retrofitted from existing plants.
High nitrate (NO3−-N) concentration in the effluent of wastewater treatment plants (WWTPs), cannot meet the increasing stringent discharge limits. Hence, the tertiary treatment is necessary to lower the total nitrogen concentration. In this study, an innovative partial denitrification (PD)-Anammox process was applied to remove the nitrate nitrogen (20–40 mg N/L) from secondary effluent. The nitrate wastewater were firstly fed to PD sequencing batch reactor (SBR, 10 L) to produce nitrite along with the low carbon/nitrogen ratio (C/N) municipal sewage (NH4+ of 57.8 mg N/L, COD of 175.8 mg/L), then the effluent from SBR was pumped to the anaerobic sludge blanket (UASB, 3.2 L) performing anammox for further nitrogen removal. The integrated process was operated for 224 days with the secondary effluent to municipal sewage volume ratio of 2.9–6. The results suggested that an excellent nitrate removal efficiency of 97.9% was achieved, and the mean removal efficiency of NH4+-N and COD from municipal sewage were 95.2% and 81.6%, respectively, leading to the total nitrogen and COD concentration in the final effluent as low as 4.0 mg N/L and 30.1 mg/L, respectively. Anammox was the main nitrogen removal pathway with a mean proportion of 78.2%, and Candidatus_Brocadia was identified as the dominating genus. Furthermore, it was found that a minor nitrous oxide (N2O) was produced in the integrated process. The PD-Anammox process was verified to be economically and environmentally feasible for retrofitting of existing plants.
Anaerobic ammonium oxidation (anammox) has been extensively investigated for cost-efficient nitrogen removal from wastewater. However, the major issues of nitrate (NO3−-N) residue and instability in ...the current combination of nitritation and anammox process necessitates being addressed efficiently. The recently proposed partial-denitrification (PD), terminating NO3−-N reduction to nitrite (NO2−-N), has been regarded as a promising alternative of NO2−-N supplying for anammox bacteria. Given the engineering practices, the steadily high NO2−-N production, alleviating organic inhibition, and reducing greenhouse gas of PD process offers a viable and efficient approach for anammox implementation. Moreover, it allows for the extending applications of anammox process due to the NO3−-N removal availability. Here we comprehensively review the important new outcomes and discuss the emerging applications of PD-based anammox including the process development, mechanism understanding, and future trends. Significant greater stability and enhanced nitrogen removal efficiency have been demonstrated in the novel integrations of PD and anammox process, indicating a broad perspective in dealing with the mainstream municipal sewage, ammonia-rich streams, and industrial NO3−-N contained wastewater. Furthermore, researches are still needed for the predictable and controllable strategies, along with the detailed microbiological information in future study. Overall, the achievement of PD process provides unique opportunity catalyzing the engineering applications of energy-efficient and environmental-friendly wastewater treatment via anammox technology.
•Partial-Denitrification provides a stable and efficient alternative for nitrite supply.•PD process offers extending application of anammox treating nitrate wastewater.•PD/A holds potential in improved efficiency for mainstreams and sidestreams treatment.•Emerging opportunities are given for wastewater treatment engineering by PD/A.•Predictable controlling strategies and penetrating microbial mechanism are needed.
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•Stable NRR and ORR of 5.95 kg N/m3/day and 0.77 kg DOC/m3/day were achieved.•EEM-PARAFAC model is an efficient way to identify the species and content of rDOM during ANAMMOX ...process.•A novel metabolism mechanism of rDOM in ANAMMOX reactor was established.•Anaerolineaceae is possible primary degraders for rDOM.
This study applied combined spectroscopy techniques to assess rDOM compositional characteristic and investigated its transformation mechanisms during the treatment of mature landfill leachate by ANAMMOX process. A novel rDOM metabolism mechanism was proposed in this study for the first time. A stable, high nitrogen removal rate of 5.95 kg N/m3/day and a rDOM conversion efficiency of 51% were achieved in ANAMMOX reactor (AR). In additionally, the initial rDOM removal was closely related to sludge adsorption, with the adsorption force mainly originating from electrostatic interaction and hydrophobicity. As the operating time increased, the removal mechanism of rDOM in the AR changed from adsorption to adsorption-biodegradation and finally stabilized. Furthermore, Anaerolineaceae, associated with the hydrophobic reaction, were the primary degraders for the rDOM and Candidatus Kuenenia dominated the nitrogen consumption. rDOM removal efficiency was suggested to be increased by a moderate enhancement of Anaerolineaceae content in the AR.
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•Partial-denitrification is a feasible way to supply nitrite for anammox.•Nitrite accumulation rate (NAR) increased with pH during denitrification.•The higher NAR at pH 9.0 was ...correlated with an enrichment of Thauera.•Thauera harbored more nitrate reductase than nitrite reductase.•A process for achieving partial denitrification/anammox in WWTP was proposed.
Partial-denitrification (nitrate to nitrite) can supply nitrite for anammox which can reduce organic matter consumption in wastewater treatment plants (WWTPs). In order to achieve stable partial-denitrification, the effect of pH on denitrification were investigated for 420 days in three reactors with influent pH of 5.0, 7.0 and 9.0. The results indicate that the nitrite accumulation rate (NAR) increased with pH, with average effluent NARs being 21%, 38% and 57% in the above reactors, respectively. The sludge cultivated at a high pH of 9.0 was resistant to pH shock, with a high NAR being maintained at 83% when it was exposed to a low pH of 5.0. Metagenomic analysis showed that the higher NAR at pH 9.0 was correlated with an enrichment of Thauera, which harbored more nitrate reductase (8098 hits) than nitrite reductase (2950 hits). Based on these findings, a novel process was proposed for achieving partial-denitrification/anammox in mainstream WWTPs.
Elimination of nitrogen pollution from wastewater containing high-strength nitrate (NO3−-N) is a significant issue to prevent deterioration of water quality and eutrophication of receiving water ...body. Traditional denitrification process faces several challenges including the huge organic carbon demand, intermediate products accumulation, and long acclimatization period. In this study, an efficient solution was given by a novel two-stage Partial Denitrification (PD)-Anammox process. High NO3−-N (1000 mg N/L) wastewater and municipal sewage (COD: 182.5 mg/L, ammonia (NH4+-N): 58.3 mg/L) were simultaneously introduced to the PD reactor for NO3−-N converting to NO2−-N. The NH4+-N and NO2−-N in effluent of PD were removed in subsequent anammox reactor. Results showed that a satisfactory nitrogen removal was achieved by optimizing the volume ratios of influent NO3−-N and municipal sewage, as well as the external organic matter dosage. The NO3−-N removal efficiency reached up to 95.8% without accommodation period, along with the NH4+-N removal achieving 92.8%. Anammox contributed to 78.9% of TN removal despite the high COD (76.5–98.6 mg/L) in PD effluent was introduced, indicating the significant stability of the integrated process. The microbial analysis suggested that the Candidatus Brocadia, identified as anammox bacteria, cooperated stable with denitrifying bacteria in 215-day operation. The PD-Anammox process offers an economically and technically attractive approach in the high NO3−-N wastewater treatment since it has great advantages of much low carbon demand, minimal sludge production, enabling simultaneous treatment of municipal sewage, and avoiding the common issues in traditional denitrification process.
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•Simultaneous treatment of high-strength nitrate and municipal sewage was demonstrated.•Nitrate removal efficiency reached up to 95.8% at influent nitrate of 1000 mg/L.•Municipal sewage was treated with nitrogen removal efficiency of 92.8%.•Anammox and denitrifying bacteria cooperated for advanced nitrogen removal.•Partial-denitrification combining with anammox is an economic and efficient option.
Mainstream anammox still faces the challenges of non-ideal NO2−/NH4+ ratios and excess nitrate resulted from the instability of partial nitrification (PN) in municipal wastewater. To address these ...problems, in this study, we developed a novel two-sludge process that combined PN with synchronous anammox and endogenous partial denitrification (SAEPD); the process was tested with pre-treated domestic sewage at ambient temperatures for 205 d. High nitrogen removal efficiency of 91.2% was achieved with an influent C/N ratio of 1.7 at 15.4 °C; the success was attributed to the fact that EPD replenished the deficient nitrite by reducing nitrate and the excess nitrite was further reduced to nitrogen gas. With a non-ideal NO2−/NH4+ ratio of 0.89, the contribution of the SAEPD-sequencing batch reactor (SBR) during the anoxic stage reached 98.2% and the proportional contributions of the anammox and denitrification pathways were 77.2% and 22.8%, respectively. Although the low nitrite accumulation (66.1%) caused 10.8 mg N/L of nitrate to be transported into the SAEPD-SBR and the anammox reaction also converted 20% of nitrite to nitrate, only 1.1 mg N/L of nitrate remained in the effluent. High-throughput sequencing analysis revealed that although NH2OH was added, some genera of nitrite-oxidizing bacteria (0.73%) remained in the PN-SBR and potentially resulted in the oxidation of nitrite to nitrate. In the SAEPD-SBR, anammox and endogenous denitrifying bacteria co-existed and synergistically achieved the removal of ammonium, nitrite, and nitrate. Overall, the PN-SAEPD process has great potential for achieving cost-effective and energy-efficient municipal wastewater treatment.
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•EPD enhanced the robustness of mainstream anammox to cope with different NO2−/NH4+ ratios.•High TIN removal efficiency (91.2%) was achieved with a C/N ratio of 1.7 at 15.4 °C.•PN-SAEPD process has a unique advantage over the traditional PN/A process for treating nitrate.•Anammox and endogenous denitrifying bacteria synergistically achieved nitrogen removal.•PN-SAEPD process is an energy-efficient municipal wastewater treatment process.
Presently, the wastewater treatment practices can be significantly improved through the introduction of new microbial treatment technologies. To meet increasingly stringent discharge standards, new ...applications and control strategies for the sustainable removal of ammonium from wastewater have to be implemented. Partial nitrification to nitrite was reported to be technically feasible and economically favorable, especially when wastewater with high ammonium concentrations or low C/N ratios is treated. For successful implementation of the technology, the critical point is how to maintain partial nitrification of ammonium to nitrite. Partial nitrification can be obtained by selectively inhibiting nitrite oxidizing bacteria through appropriate regulation of the system's DO concentration, microbial SRT, pH, temperature, substrate concentration and load, operational and aeration pattern, and inhibitor. The review addressed the microbiology, its consequences for their application, the current status regarding application, and the future developments.
Sludge aggregation and biofilm formation are the most effective approaches to solve the washout of anammox microorganisms. In this study, the structure and composition of EPS (extracellular polymeric ...substances) were investigated to elucidate the factors for the anammox aggregation property. Anammox sludge taken from 18 lab-scale and pilot-scale reactors treating different types of wastewater was analyzed using EEM-PARAFAC (excitation-emission matrix and parallel factor analysis), FTIR (Fourier transform infrared spectroscopy) and real-time PCR combined with multivariate statistical analysis. The results showed that slime and TB-EPS (tightly bound EPS) were closely related with water quality and sludge morphology, and could be used as the indicators for anammox microbial survival ability and microbial aggregate morphology. Furthermore, slime secreted from anammox bacterial cells may be exhibited higher viscosity to the sludge surface and easily formed the gel network to aggregate. Large amounts of hydrophobic groups of protein in TB-EPS promoted the microbial aggregation. The mechanisms of anammox aggregation explored in this study enhanced the understanding of anammox stability in wastewater treatment processes.
In this study, a novel DEAMOX (DEnitrifying AMmonium OXidation) process coupling anammox with partial-denitrification generated nitrite (NO2−-N) from nitrate (NO3−-N) was developed for simultaneously ...treating ammonia (NH4+-N) and NO3−-N containing wastewaters. The performance was evaluated in sequencing batch reactors (SBRs) with different carbon sources for partial-denitrification: acetate (R1) and ethanol (R2). Long-term operation (180 days) suggested that desirable nitrogen removal was achieved in both reactors. The performance maintained stably in R1 despite the seasonal decrease of temperature (29.2 °C–12.7 °C), and high nitrogen removal efficiency (NRE) of 93.6% on average was obtained with influent NO3−-N to NH4+-N ratio (NO3−-N/NH4+-N) of 1.0. The anammox process contributed above 95% to total nitrogen (TN) removal in R1 with the nitrate-to-nitrite transformation ratio (NTR) of 95.8% in partial-denitrification. A little lower NRE was observed in R2 with temperature dropped from 90.0% at 22.7 °C to 85.2% at 16.6 °C due to the reduced NTR (87.0%–67.0%).
High-throughput sequencing analysis revealed that Thauera genera were dominant in both SBRs (accounted for 61.53% in R1 and 45.17% in R2) and possibly played a key role for partial-denitrification with high NO2−-N accumulation. The Denitratisoma capable of complete denitrification (NO3−-N→N2) was found in R2 that might lead to lower NTR. Furthermore, different anammox species was detected with Candidatus Brocadia and Candidatus Kuenenia in R1, and only Candidatus Kuenenia in R2.
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•Two novel DEAMOX were established for simultaneously treating NH4+-N and NO3−-N.•Stable nitrogen removal efficiency of 93.6% was achieved in acetate-driven DEAMOX.•Nitrogen removal efficiency declined from 90.0% to 85.2% in ethanol-driven DEAMOX.•Genera Thauera (61.53% and 45.17%) would play key role in partial-denitrification.•Brocadia and Kuenenia were identified in acetate-SBR, only Kuenenia in ethanol-SBR.
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