Comparative study of different ultrasound based hybrid oxidation approaches for treatment of real effluent from coke oven plant.

The present study investigates the treatment of real coke plant effluent utilising several ultrasound-based hybrid oxidation approaches including Ultrasound (US) alone, US + catalyst, US + H2O2, US + Fenton, US + Ozone, and US + Peroxone, with main objective as maximizing the reduction of chemical oxygen demand (COD). Ultrasonic horn at power of 130 W, frequency as 20 kHz and duty cycle as 70% was applied. Study with varying catalyst (TiO2) dose from 0.5 g/L - 2 g/L revealed 1 g/L as the optimum dose resulting in 65.15% reduction in COD. A 40 ml/L dose of H2O2 was shown to be optimal, giving an 81.96% reduction in COD, based on the study of varied doses of H2O2 from 20 ml/L to 60 ml/L. US + Fenton reagent combination at optimum Fe2+/H2O2 (w/v) ratio of 1:1 resulted in a COD reduction of 85.29% whereas reduction of COD as 81.75% was obtained at the optimum flow rate of ozone as 1 LPM for US + Ozone approach. US + Peroxone demonstrated the best efficiency (90.48%) for COD reduction. To find the toxicity effects, the treated (US + peroxone) and non-treated samples were tested for the growth of bacterial cultures. It was observed that the toxicity of the treated sample increased only marginally after treatment. High-resolution liquid chromatography mass spectrometry (HR-LCMS) analysis was also performed to establish intermediate compounds. Overall, the coupling of ultrasound with oxidation processes produced better results with US + Peroxone established as best treatment approach for coke plant effluent.

Endovascular Versus Surgical Treatment for All Comer Patients With Prosthetic Bypass Graft Occlusion: The Multicentre ENSUPRO Study.

OBJECTIVE: Bypass surgery plays a key role in complex lower limb lesions. However, there is a lack of evidence regarding the management of symptomatic prosthetic bypass graft (PBG) occlusion. This study aimed to report outcomes following open, hybrid, or endovascular management of patients presenting with symptomatic PBG occlusion. METHODS: A multicentre, retrospective cohort study was conducted, including patients presenting with PBG occlusion between January 2014 and December 2021 from 18 centres. It assessed the comparative value of treatment strategies, including (1) recanalisation of native vessels, (2) endovascular treatment of the failed PBG, (3) hybrid treatment, and (4) open surgery. The primary outcome measure was amputation free survival (AFS, time to major amputation and or death), whereas all cause mortality, major amputation, PBG re-occlusion, target lesion revascularisation (TLR), and Rutherford category (RC) improvement during follow up were considered as secondary endpoints. RESULTS: Of 260 patients with occluded PBGs, 108 (41.5%) were treated endovascularly (24 [22.2%] by recanalisation of native vessels and 84 [77.7%] by PBG re-opening), 57 (21.9%) underwent hybrid revascularisation, and 58 (22.3%) had surgery. In addition, 27 (10.4%) were treated conservatively and 10 (3.8%) received systemic thrombolysis. With a median follow up of 1.4 (0.6 - 3.0) years, AFS was 95.5%, 76.4%, 45.5%, and 37.1%, respectively in Groups 1 - 4 (p = .007). Older age and non-endovascular treatment (HR 1.05 and 1.70; p < .01 for both) were independent predictors of poor AFS. Endovascular treatment was associated with lower rates of major amputation (p = .04), PBG re-occlusion (p < .001), and TLR (p = .037), and higher RC improvements (p < .001), whereas all cause mortality was comparable between treatment groups (p = .21). CONCLUSION: Endovascular treatment is associated with higher rates of AFS and RC improvement and lower rates of PBG re-occlusion and TLR in patients with PBG occlusion.

Sequential hybrid ablation versus surgical CryoMaze alone for treatment of atrial fibrillation (SurHyb Trial): a protocol of the multicentre randomized controlled trial.

BACKGROUND: Atrial fibrillation is common in patients with structural heart disease who are undergoing cardiac surgery. Surgical CryoMaze has been shown to be an effective treatment in several trials, but success rates have varied considerably, between 47-95%. The sequential hybrid approach, combining surgical CryoMaze followed by radiofrequency catheter ablation, can achieve high freedom from atrial arrhythmias. However, in patients with concomitant surgical atrial fibrillation treatment, data comparing the hybrid approach to CryoMaze alone are lacking. METHODS: The SurHyb study was designed as a prospective, open-label, multicentre randomized trial. Patients with non-paroxysmal atrial fibrillation who were scheduled for coronary artery bypass grafting or valve repair/replacement were randomized to either surgical CryoMaze alone or surgical CryoMaze followed by radiofrequency catheter ablation 3 months post-surgery. The primary outcome measure was arrhythmia-free survival without class I or III antiarrhythmic drugs, which has been evaluated using implantable cardiac monitors. CONCLUSIONS: This is the first randomized study that compares concomitant surgical CryoMaze alone with the staged hybrid surgical CryoMaze followed by catheter ablation, in patients with non-paroxysmal atrial fibrillation using rigorous rhythm monitoring. The results may contribute to the optimization of the treatment in patients undergoing concomitant CryoMaze for atrial fibrillation.

Leachate treatment using sequential microwave and algal photo-bioreactor: Effect of pretreatment on reactor performance and biomass productivity.

The present study aims to design a lab-scale hybrid reactor, primarily focused on the removal of organics, nutrients, heavy metal and other toxic compounds, thereby, minimizing risk associated with the disposal of landfill leachate. The potential of a designed hybrid treatment system (i.e., sequential microwave (MW) with algal bioreactor) with and without pretreatment, i.e., coagulation-flocculation (CF), was evaluated based on several parameters. The CF pretreatment under optimized conditions has resulted in 90% turbidity and 76% COD removals from leachate; furthermore, the MW treatment achieved 91% ammonia removal from raw leachate. As a result, substantial algal growth was observed in the preliminary algal batch experiment conducted with MW and MW-CF treated samples. Subsequently, leachate treatment was carried out using sequencing batch reactor (SBR) systems, i.e., MW-algal SBR and CF-MW-algal SBR. Algal biomass growth and increment in DO level were observed in algal-SBR experiments. Under the optimized reactor conditions, TN and TP removal rates in the algal-SBR were found to be 1.67-20 mg/L/d and 0.6-9.6 mg/L/d, respectively. The majority of heavy metals present in the leachate were removed due to algal-uptake (mainly Zn2+) and bio-sorption (total-Fe, Cu2+ and Pb2+). Meanwhile, some amount of energy can be recovered from algal biomass as inferred from the cost benefit analysis. Overall, the hybrid treatment combining MW and algal-SBR has shown immense potential for sustainable leachate treatment.

[Aortic arch debranching in hybrid thoracic aortic replacement]. / Pereklyucheniya vetvei dugi pri gibridnykh vmeshatel'stvakh na grudnoi aorte.

OBJECTIVE: To analyze the outcomes of aortic arch debranching in hybrid thoracic aortic replacement. MATERIAL AND METHODS: There were 107 patients who underwent hybrid thoracic aortic repair with debranching of supra-aortic vessels between 2015 and 2021. Patients underwent total and partial debranching (subtotal debranching and subclavian-carotid anastomosis/bypass). Debranching was performed in patients with type 3 dissection, type B aneurysms, post-traumatic aortic isthmus and arch aneurysms, thoracoabdominal aneurysms type A and DeBakey type 1 dissections. RESULTS: One patient (0.9%) died from thoracic aorta rupture after retrograde dissection. There was a moderate decrease of blood flow velocity through the left vertebral artery after subtotal debranching without severe hemodynamic disorders. Despite mild surgical trauma, subtotal and especially total debranching are characterized by higher risk of thrombosis of branches with potential fatal outcomes. In young patients requiring subtotal aortic arch debranching, open reconstruction or repair with fenestrated stents is preferred. We recommend a Bavaria type II hybrid procedure for patients with high surgical risk. In our opinion, more physiological hybrid interventions with anatomical arrangement of supra-aortic vessels such as Elephant Trunk and Frozen Elephant Trunk procedures are preferred.

Comparison of acoustic and hydrodynamic cavitation based hybrid AOPs for COD reduction of commercial effluent from CETP.

The present work investigates the treatment of commercial effluent obtained from Common Effluent Treatment Plants (CETP) using acoustic cavitation (AC) and hydrodynamic cavitation (HC) based hybrid AOPs. Comparison of different hybrid AOPs viz. H2O2, Fe2+/H2O2, Fe2+/H2O2/Air, Fe2+/H2O2/S2O82- and Fe2+/H2O2/S2O82-/Air in combination with both AC and HC has been performed in terms of extent of chemical oxygen demand (COD) reduction and kinetic rate constants. The best results of COD reduction as 95.2% and 97.28% were obtained for AC/Fe2+/H2O2/Air and HC/Fe2+/H2O2/Air systems respectively at Fe2+/H2O2 ratio of 0.1 and pH of 2 within 60 min of treatment under conditions of ultrasonic power dissipation as 150 W, inlet pressure for HC as 4 bar (as applicable depending on process) and temperature of 30 ± 2 °C. Slightly lower efficacy was established for the combination approach involving AC or HC coupled with Fe2+-activated S2O82- and H2O2 yielding COD reduction of 82.9% and 86.93% for the AC/Fe2+/H2O2/S2O82-/Air and HC/Fe2+/H2O2/S2O82-/Air systems respectively at Fe2+/H2O2/S2O82- ratio of 1:40:17.5. Cost estimation on the basis of cavitational yield performed on the AC and HC based treatment systems revealed economical nature of HC based treatment. Kinetic studies were also performed by fitting the experimental data with pseudo first order kinetic model (PFOKM), generalized kinetic model (GKM) and Behnajady-Modirshahla-Ghanbery kinetic model (BMGKM). It was demonstrated that GKM provided best fitting for all the experiments whereas BMGKM was most suitable for Fenton based reactions. It was clearly established that complex CETP effluent can be effectively treated using the combined approaches based on HC with potential for larger scale operation.

A modified surgical ablation line for atrial fibrillation. The Bachmann line.

Surgical treatment of atrial fibrillation generally consists in the isolation of the pulmonary veins ("box-lesion"). Bachmann's bundle is a cardiac structure that may play an important role in the genesis of the atrial fibrillation. Surgical isolation of such bundle has not been reported before. We aim to describe how to perform minimally invasive epicardial pulmonary vein isolation along with the isolation of the Bachmann's bundle. Adding the surgical ablation line of Bachmann's bundle is a feasible, fast, and easy procedure that may be contribute to the reduction of atrial fibrillation relapses.

[Hybrid technologies in treatment of a patient with vascular graft infection]. / Gibridnye tekhnologii v lechenii bol'nogo s infektsiei sosudistogo proteza.

Presented in the article are advantages of various methods of treatment of periprosthetic infection which continues to be one of the most challenging problems in modern vascular surgery. We describe herein a clinical case report regarding a patient with late infection of a bifurcated aortofemoral bypass graft. The infectious complication manifested itself by a periprosthetic infiltrate in the area of the distal anastomosis. The stent-graft's limb was resected within the limits of the unaltered tissue. The infectious process then manifested itself as sequestration of the main branch. Staged complete anatomical reconstruction performed later on using a hybrid technique made it possible to achieve an optimal result and resolution of the infection. This case report demonstrated undeniable advantages of using hybrid techniques.

[Hybrid approach to surgical treatment for a saccular thoracic aortic aneurysm]. / Gibridnyi podkhod pri khirurgicheskom lechenii meshotchatoi anevrizmy grudnoi aorty.

Presented herein is a clinical case report regarding hybrid surgical treatment for a saccular aneurysm of the aortic arch in a female patient. While undergoing a routine medical check-up she had been found to have fluorographic evidence strongly suggesting dilatation of the aortic thoracic portion. Based on the findings of further examination we determined the indications for surgical treatment of the thoracic portion of the aorta. The woman was subjected to reconstruction of the arch and the descending portion of the thoracic aorta according to the frozen elephant trunk technique.

Hybrid treatment of a giant thoracic aneurysm in a 38 year-old woman.

A 38-year-old woman, with no comorbidities, presented to an outside institution with a 10-cm aortic arch and descending thoracic aortic aneurysm. After an aborted attempt at hybrid repair, she underwent successful, staged repair with zone 1 thoracic endovascular aortic repair and open aneurysmal sac revision. The patient made an uneventful recovery with computed tomographic evidence of complete aneurysmal exclusion. This case demonstrates many of the techniques and issues in the evolving field of aortic arch repair.

Cervical Debranching in the Endovascular Era: A Single Centre Experience.

OBJECTIVE/BACKGROUND: Debranching of the supra-aortic arteries is a common practice either as part of a hybrid treatment of aortic arch pathology or owing to arterial occlusive disease. Results of the debranching techniques have not been reported frequently. METHODS: This was a retrospective single centre study of all consecutive patients with cervical debranching procedures as part of hybrid aortic arch repair. RESULTS: Between 2010 and 2017, 201 patients underwent 211 cervical debranching procedures in a tertiary centre. Mean ± SD patient age was 67.7 ± 10.7 years (70.6% males; n = 142/201) and mean ± SD body mass index (BMI) was 26.3 ± 5. In 78.7% of the cases carotid-subclavian bypass was performed alone (n = 166/211) followed by transposition of the subclavian artery to the ipsilateral carotid (n = 17/211; 8.1%) and in 28 cases (13.3%) a combination of procedures was performed. Twenty-four cases (11.4%) were complicated with local bleeding and 21 cases required re-intervention (10.4%). Nineteen patients (9.5%) developed local peripheral neurological damage post-operatively. Eight patients (3.8%) developed a chylous fistula and five (2.4%) presented with a local wound infection. One patient (0.5%) developed a bypass graft infection. The thirty day mortality was 7.6% (n = 16/211): one death occurred after isolated debranching without thoracic endovascular aneurysm repair (TEVAR; 0.5%). Whether the hybrid procedures were undertaken in a single stage (simultaneous TEVAR and cervical debranching) or two stage fashion appeared to have a significant impact on 30 day mortality (single stage n = 9/60 [15%] vs. debranching alone or two stage hybrid procedures n = 7/144 [4.9%]; p = .018). The major stroke incidence was 4.3% (n = 9/211); no strokes occurred after isolated debranching. Stroke was correlated with longer operating times (odds ratio [OR] 1.006; 95% confidence interval [CI] 1.000-1.011; p = .045) and higher BMI (OR 1.195; 95% CI 1.009-1.415; p = .039). Mean ± SD follow up was 15 ± 17 months (range 0-89 months). Primary cumulative graft patency during follow up was 98.1% (n = 207/211) and secondary patency was 100%. CONCLUSION: The results of cervical debranching procedures showed not only excellent patency rates, but also a significant rate of local complications. Carotid-subclavian bypass appeared to be safer with significantly fewer post-operative complications. Staged hybrid procedures also seemed to be safer.

Extra-anatomical splanchnic revascularization for hybrid treatment of thoracoabdominal aortic aneurysms.

Treatment of thoracoabdominal aortic aneurysms with endovascular or conventional surgical techniques is burdened by high risk in older patients. Furthermore, the standard hybrid approach might be not feasible in case of severe atherosclerotic disease of the peripheral vessels. This report describes an alternative hybrid procedure which consists of an innovative mini-invasive thoracic approach combined with laparotomy to perform antegrade revascularization of the visceral arteries from the ascending aorta, followed by endovascular treatment.

Hybrid treatment of multilevel revascularization in patients with peripheral arterial disease - a multi-centre study in Korea.

BACKGROUND: Endovascular treatment is an alternative first-line management for peripheral artery disease (PAD). Hybrid treatment (HT) is defined as a combined treatment for patients with PAD using endovascular and open surgery, simultaneously performed in an operating room. The results of HT are reportedly good for multilevel revascularization (MR) in patients with chronic limb ischaemia, and even in older high-risk patients. The goal of this study was to examine the clinical and haemodynamic outcomes of HT in patients who need MR. PATIENTS AND METHODS: Nine university hospitals in Korea participated in this multicentre study. A total of 134 patients with multilevel PAD underwent HT and MR. Patients were enrolled from July 2014 to June 2015 and were followed for 18 months. RESULTS: The mean age of the patients was 68.8 ± 9.93 years and 88.1 % were men. Patients with Rutherford category 2 to 3 and 4 to 6 comprised 59.0 % and 42.0 % of the group, respectively. The technical success rate was 100 %. The primary patency rates at 12 and 18 months were 77.6 % and 63.9 %, respectively. The primary-assisted patency rates at 12 and 18 months were both 90.0 %. The pre-operative mean ankle brachial index (0.43 ± 0.23) increased to 0.87 ± 0.23 at six months post-operatively (t-test, p < 0.05). The amputation free survival rate was 97.1 %. CONCLUSIONS: Although outcomes of multilevel PAD are reportedly poor when endovascular treatment alone is used, we have shown that HT is a feasible alternative modality for patients with multilevel PAD, with satisfactory amputation-free survival and freedom from re-intervention rates.

Photosynthetic pretreatment increases membrane-based rejection of boron and arsenic.

The metalloids boron and arsenic are ubiquitous and difficult to remove during water treatment. As chemical pretreatment using strong base and oxidants can increase their rejection during membrane-based nanofiltration (NF), we examined a nature-based pretreatment approach using benthic photosynthetic processes inherent in a unique type of constructed wetland to assess whether analogous gains can be achieved without the need for exogenous chemical dosing. During peak photosynthesis, the pH of the overlying clear water column above a photosynthetic microbial mat (biomat) that naturally colonizes shallow, open water constructed wetlands climbs from circumneutral to approximately 10. This biological increase in pH was reproduced in a laboratory bioreactor and resulted in analogous increases in NF rejection of boron and arsenic that is comparable to chemical dosing. Rejection across the studied pH range was captured using a monoprotic speciation model. In addition to this mechanism, the biomat accelerated the oxidation of introduced arsenite through a combination of abiotic and biotic reactions. This resulted in increases in introduced arsenite rejection that eclipsed those achieved solely by pH. Capital, operation, and maintenance costs were used to benchmark the integration of this constructed wetland against chemical dosing for water pretreatment, manifesting long-term (sub-decadal) economic benefits for the wetland-based strategy in addition to social and environmental benefits. These results suggest that the integration of nature-based pretreatment approaches can increase the sustainability of membrane-based and potentially other engineered treatment approaches for challenging water contaminants.

Intraoperative electrochemotherapy of the posterior resection surface after pancreaticoduodenectomy: Preliminary results of a hybrid approach treatment of pancreatic cancer.

BACKGROUND: Despite extensive research in recent decades, pancreatic cancer continues to be among the most lethal forms of cancer, with no substantial increase in survival rates. Local recurrences account for approximately 30 per cent of all disease recurrences. With the intent to improve survival, we designed a novel, hybrid treatment strategy consisting of surgical resection and additional intraoperative electrochemotherapy of the posterior resection surface. We present the study protocols and preliminary findings of a prospective pilot study investigating this treatment approach. METHODS: Consenting patients with resectable pancreatic head ductal adenocarcinoma who met the inclusion criteria were enrolled in the study. After surgical resection, electrochemotherapy with bleomycin was performed using plate electrodes to cover the area between anatomical landmarks. RESULTS: Electrochemotherapy of the posterior resection surface was feasible in all 7 patients. We observed pancreatic fistula grade B in only one patient; all other noted complications were Clavien-Dindo grade 2 or less. The hospital mortality was 0%. CONCLUSIONS: Our preliminary results suggest that a hybrid approach combining surgery with intraoperative electrochemotherapy is safe and feasible.

Equivalence Trial of the Non-Bismuth 10-Day Concomitant and 14-Day Hybrid Therapies for Helicobacter pylori Eradication in High Clarithromycin Resistance Areas.

Background and aim: We conducted an equivalence trial of quadruple non-bismuth "concomitant" and "hybrid" regimens for H. pylori eradication in a high clarithromycin resistance area. Methods: There were 321 treatment-naïve H. pylori-positive individuals in this multicenter clinical trial randomized to either the hybrid (esomeprazole 40 mg/bid, amoxicillin 1 g/bid for 7 days, then 7 days esomeprazole 40 mg/bid, amoxicillin 1 g/bid, clarithromycin 500 mg/bid, and metronidazole 500 mg/bid) or the concomitant regimen (all medications given concurrently bid for 10 days). Eradication was tested using histology and/or a 13C-urea breath test. Results: The concomitant regimen had 161 patients (90F/71M, mean 54.5 years, 26.7% smokers, 30.4% ulcer) and the hybrid regimen had 160 (80F/80M, mean 52.8 years, 35.6% smokers, 31.2% ulcer). The regimens were equivalent, by intention to treat 85% and 81.8%, (p = 0.5), and per protocol analysis 91.8% and 87.8%, (p = 0.3), respectively. The eradication rate by resistance, between concomitant and hybrid regimens, was in susceptible strains (97% and 97%, p = 0.6), clarithromycin single-resistant strains (86% and 90%, p = 0.9), metronidazole single-resistant strains (96% and 81%, p = 0.1), and dual-resistant strains (70% and 53%, p = 0.5). The side effects were comparable, except for diarrhea being more frequent in the concomitant regimen. Conclusions: A 14-day hybrid regimen is equivalent to a 10-day concomitant regimen currently used in high clarithromycin and metronidazole resistance areas. Both regimens are well tolerated and safe.

Sequential electro-coagulation and electro-Fenton processes for the treatment of textile wastewater.

Textile wastewater, laden with persistent dyes and non-biodegradable organics, poses a challenge for treatment in common effluent treatment plants (CETPs) using conventional methods. Pre-treatment of textile effluents is essential to ensure compatibility with CETPs. The present study employed three-dimensional (3D) aluminum and graphite electrodes for a sequential electro-coagulation and electro-Fenton (EC + EF) process. An experimental plan of 25 experiments was constructed using Taguchi method. The combination resulted in high removal efficiencies: 99.91% for color, 93.20% for chemical oxygen demand (COD), and 91.75% for total organic carbon (TOC) for the operating parameters; for EC, current density (J): 20 mA/cm2, time (t): 45 min, speed of rotation (N): 55 rpm; and for EF, current density (J): 25 mA/cm2, time (t): 50 min, iron concentration: 40 mg/L. Post-treatment, the wastewater exhibited an enhanced biodegradability index of 0.875, rendering it suitable for CETPs. There was an increase of 11% in the total energy consumption when energy spent during rotation and aeration at the time of EC and EF, respectively, were considered. This energy increases the cost and is not accounted for, in previous research. The energy consumption in kWh per g of COD removed at optimum condition for the hybrid treatment was 0.0314, which is lower than the energy consumption by other electrochemical processes employing plate electrodes. This indicates that 3D electrodes are more energy efficient than plate electrodes. PRACTITIONER POINTS: Hybrid electrochemical processes can be used as pre-treatment method for textile effluents. Three-dimensional electrodes improve removal rates with lower energy consumption. Significant color, COD, and TOC abatement were noted post-hybrid treatment of textile wastewater. Biodegradability of the textile effluent improves after the hybrid treatment.

Interlobar pulmonary sequestration with celiac aberrant artery in an elderly patient treated with combined endovascular and video-assisted thoracoscopic approach.

Pulmonary sequestration is a rare congenital pulmonary anomaly where a portion of the lung parenchyma is supplied by an anomalous systemic artery, usually originating from the thoracic or abdominal aorta. Traditionally surgical resection and ligation of the aberrant feeding vessel are the gold standard treatments of this disease. Hybrid operations consisting in endovascular arterial embolization and surgical resection is a promising treatment option. We report a case of a 69-years-old man with symptomatic intralobular sequestration successfully treated by hybrid approach.

Economic and environmental benefits of natural treatment systems for sewage treatment: A life cycle perspective.

Sewage treatment involves a trade-off of land vs. energy and the location of installing Sewage Treatment Plants (STPs) strongly impacts the decisions regarding treatment technologies. In the wake of rapid urbanization, deteriorating freshwater quality and water scarcity, it is crucial to plan adequate and low-cost sewerage infrastructure that can improve the quality of life in rural and urban areas. The present work involves a novel life cycle analysis through six scenarios generated from a holistic perspective that can aid urban planners and urban local bodies in planning the sewage treatment facilities in their cities, towns or villages. Instead of planning sewerage infrastructure for a long-term period of thirty years, it is suggested to create and operate the STPs only for the upcoming decade. Further, owing to the drawbacks of mechanized and natural treatment systems, adopting a mix of these treatment approaches in planning infrastructure is suggested and the benefits of implementing the same are quantified and discussed. Implementing these strategies results in almost 30 % cost savings and 40 % reduction in greenhouse gas emissions, hence, investing in land for natural treatment systems is suggested instead of incurring heavy electricity bills for mechanized treatment systems. The land cost significantly affects the decision-making regarding treatment technology selection; hence, the variation in the life cycle cost of different sewage treatment approaches is assessed for varying land rates in India.

Robustness of the anammox process at low temperatures and low dissolved oxygen for low C/N municipal wastewater treatment.

Low water temperatures and ammonium concentrations pose challenges for anammox applications in the treatment of low C/N municipal wastewater. In this study, a 10 L-water bath sequencing batch reactor combing biofilm and suspended sludge was designed for low C/N municipal wastewater treatment. The nitrogen removal performance via partial nitrification anammox-(endogenous) denitrification anammox process was investigated with anaerobic-aerobic-anoxic mode at low temperatures and dissolved oxygen (DO). The results showed that with the decrease of temperature from 30 to 15℃, the influent and effluent nitrogen concentrations and nitrogen removal efficiencies were 73.7 ± 6.5 mg/L, 7.8 ± 2.8 mg/L, and 89.4 %, respectively, with aerobic hydraulic retention time of only 6 h and DO concentration of 0.2-0.5 mg/L. Among that, the stable anammox process compensated for the inhibitory effects of the low temperatures on the nitrification and denitrification processes. Notably, from 30 to 15℃, the anammox activity and relative abundance of the dominant Brocadia genus were increased from 39.7 to 45.5 mgN/gVSS/d and 7.3 to 12.0 %, respectively; the single gene expression level of the biofilm increased 9.0 times. The anammox bacteria showed a good adaptation to temperatures reduction. However, nitrogen removal by anammox was not improved by increasing DO (≥ 4 mg/L) at 8-4℃. Overall, the results of this study demonstrate the feasibility of the mainstream anammox process at low temperatures.