Influence du stockage des boues de STEP sur les émissions de NH3 et de COV durant leur séchage

Le séchage constitue une étape importante en aval de la déshydratation mécanique en vue de la valorisation agricole ou énergétique des boues de station d’épuration. La teneur en eau peut être réduite à moins de 5%, diminuant ainsi la masse et le volume des boues et, par conséquent, le coût pour le stockage, la manutention et le transport. L'élimination de l'eau augmente considérablement le pouvoir calorifique inférieur, transformant les boues en un combustible convenable. En outre, les boues séchées peuvent être stabilisées et exemptes d'agents pathogènes en fonction de la température et de la durée de traitement. Les technologies convectives sont largement utilisées pour le séchage des boues. Le principal avantage est la simplicité de la technologie et l’inconvénient majeur résulte de la grande quantité d'air à épurer et désodoriser. Le but des travaux menés par l'Université de Liège et VEOLIA Environnement est d'effectuer une caractérisation en laboratoire des émissions gazeuses en fonction des conditions de séchage. Pour ce faire, il est primordial de garantir une qualité constante de l'échantillon initial tout au long des mesures. En effet, même si elles sont conservées à basse température, les boues peuvent être le siège de dégradations biologiques et les propriétés de séchage peuvent être modifiées. Ainsi, la première partie de ce travail est consacrée à l’étude de l'influence de la durée de stockage des boues à 4°C sur les émissions gazeuses produites au cours de leur séchage convectif. Deux types de boues, l’une ayant subi une digestion et l’autre pas, sont étudiés. L’échantillonnage est effectué après la déshydratation mécanique dans deux stations de traitement des eaux usées situées à proximité de l'Université de Liège. Les échantillons sont stockés dans le laboratoire à 4°C dans un récipient hermétique. Pour effectuer les essais, 300 g de boue sont déposés dans le sécheur sous la forme d’un lit d'extrudés de 6 mm de diamètre. La masse de boue, la concentration en ammoniac et la concentration en composés organiques volatils sont mesurées en ligne respectivement par une balance, un analyseur infrarouge et un détecteur à ionisation de flamme. Des thermocouples permettent le suivi de la température en amont, au sein et en aval du lit de boue. Des essais de séchage sont effectués au jour 0 (= jour du prélèvement), et après 1, 2, 4, 10, 17 et 20 jours sous les conditions suivantes : température de l'air = 140°C; vitesse superficielle de l'air = 1 m/s; humidité absolue = 0,005 kgeau/kgair sec. La seconde partie du travail a été réalisée sur un échantillon de boue non digérée conservé à 12°C pour simuler des conditions réelles de stockage. Les essais de séchage ont été menés le jour de prélèvement et après 4, 10 et 20 jours, avec des conditions opératoires similaires. L’étude réalisée avec un stockage à 4°C montre que les émissions gazeuses sont maximales le jour du prélèvement, diminuent fortement durant les deux premiers jours de stockage pour atteindre un niveau constant durant deux semaines avant d’augmenter. Lors du stockage à 12°C, les émissions d’ammoniac et de COV sont multipliées respectivement par un facteur 40 et 4 entre le jour 0 et le jour 20. Ces résultats mettent en évidence l’impact des conditions et de la durée de stockage sur les émissions lors du séchage des boues et montrent l’importance de sécher les boues le plus rapidement possible pour limiter les nuisances

USING OF AN EXPERIMENTAL DESIGN TO CHARACTERIZE THE CONVECTIVE DRYING BEHAVIOR OF DIFFERENT SLUDGES

Drying appears as a major step prior to valorization of sludge from wastewater treatment plant. This study uses an experimental design on different sludges to highlight the drying behavior according to drying conditions, storage and extrusion. This research is performed with industrial view, but on a single cylinder sample, and focuses on five responds: maximum drying flux, time to reach 95% of dry matter, final volume, critical moisture and slowing-down coefficient

Émissions gazeuses liées au séchage convectif de boues de station d’épuration

peer reviewe

INFLUENCE OF SLUDGE TREATEMENT ON ITS CONVECTIVE DRYING BEHAVIOR

Drying appears as a major step prior to valorization of sludge from wastewater treatment plant. This study uses an experimental design on different sludges to highlight the drying behavior according to drying conditions, storage and extrusion. This research is performed with industrial view, but on a single cylinder sample, and focuses on five responds: maximum drying flux, time to reach 95% of dry matter, final volume, critical moisture and slowing-down coefficient

Impact of storage duration on the emissions of ammonia and VOC during the convective drying of urban residual sludges

peer reviewe

Flow Diverters for Intracranial Aneurysms: The DIVERSION National Prospective Cohort Study

Background and Purpose- Flow diverters are used for endovascular therapy of intracranial aneurysms. We did a nationwide prospective study to investigate the safety and effectiveness of flow diversion at 12 months. Methods- DIVERSION was a national prospective cohort study including all flow diverters placement between October 2012 and February 2014 in France. The primary end point was the event-free survival rate at 12 months, defined as the occurrence of morbidity (intracranial hemorrhage, ischemic stroke, noncerebral hemorrhage, or neurological deficit due to mass effect), retreatment, or death within 12 months post-treatment. A quality control was carried out on 100% of the collected data and of at least 10% of the included patients in each center, chosen at random. All reported serious events were adjudicated by an independent Data Safety and Monitoring Board. Satisfactory occlusion was defined as 3 or 4 on Kamran scale by an independent imaging core laboratory at 12 months. Results- We enrolled 398 patients harboring 477 intracranial aneurysms. At least 1 morbidity-mortality event was noted in 95 of 408 interventions representing an event-free survival rate of 75.7% (95% CI, 71.1-79.7). The rate of permanent-related serious events and mortality was 5.9% and 1.2% at 12 months, respectively. Multivariate analysis showed that high baseline blood pressure (hazard ratio, 2.54; 95% CI, 1.35-4.79; P=0.039), diabetes mellitus (hazard ratio, 3.70; 95% CI, 1.60-8.6; P=0.0022), and larger aneurysms (hazard ratio, 1.07; 95% CI, 1.04-1.11; P<0.0001) were associated with the occurrence of a neurological deficit. The satisfactory occlusion rate at 12 months was 79.9%, and the absence of high baseline blood pressure (odds ratio, 2.01; 95% CI, 1.12-3.71; P=0.0193) and postprocedural satisfactory occlusion (odds ratio, 2.75; 95% CI, 1.49-5.09; P=0.0012) were associated with a 12-month satisfactory occlusion. Conclusions- A satisfactory occlusion was achieved in almost 80% of cases after flow diverter treatment with a permanent-related serious event and mortality rates of 5.9% and 1.2% at 12 months, respectively

Effect of Operator's Experience on Proficiency in Mechanical Thrombectomy: A Multicenter Study

International audienceBackground and Purpose:We aimed to evaluate among trained interventional neuroradiologist, whether increasing individual experience was associated with an improvement in mechanical thrombectomy (MT) procedural performance metrics.Methods:Individual MT procedural data from 5 centers of the Endovascular Treatment in Ischemic Stroke registry and 2 additional high-volume stroke centers were pooled. Operator experience was defined for each operator as a continuous variable, cumulating the number of MT procedures performed since January 2015, as MT became standard of care or, if later than this date, since the operator started performing mechanical thrombectomies in autonomy. We tested the associations between operator’s experience and procedural metrics.Results:A total of 4516 procedures were included, performed by 36 operators at 7 distinct centers, with a median of 97.5 endovascular treatment procedures per operator (interquartile range, 57–170.2) over the study period. Higher operator’s experience, analyzed as a continuous variable, was associated with a significantly shorter procedural duration (β estimate, −3.98 [95% CI, −5.1 to −2.8]; P<0.001), along with local anesthesia and M1 occlusion location in multivariable models. Increasing experience was associated with better Thrombolysis in Cerebral Infarction scores (estimate, 1.02 [1–1.04]; P=0.013).Conclusions:In trained interventional neuroradiologists, increasing experience in MT is associated with significantly shorter procedural duration and better reperfusion rates, with a theoretical ceiling effect observed after around 100 procedures. These results may inform future training and practice guidelines to set minimal experience standards before autonomization, and to set-up operators’ recertification processes tailored to individual case volume and prior experience

Non-ischemic cerebral enhancing lesions after intracranial aneurysm endovascular repair: a retrospective French national registry

International audienceBackground Non-ischemic cerebral enhancing (NICE) lesions are exceptionally rare following aneurysm endovascular therapy (EVT). Objective To investigate the presenting features and longitudinal follow-up of patients with NICE lesions following aneurysm EVT. Methods Patients included in a retrospective national multicentre inception cohort were analysed. NICE lesions were defined, using MRI, as delayed onset punctate, nodular or annular foci enhancements with peri-lesion edema, distributed in the vascular territory of the aneurysm EVT, with no other confounding disease. Results From a pool of 58 815 aneurysm endovascular treatment procedures during the study sampling period (2006–2019), 21/37 centres identified 31 patients with 32 aneurysms of the anterior circulation who developed NICE lesions (mean age 45±10 years). Mean delay to diagnosis was 5±9 months, with onset occurring a month or less after the index EVT procedure in 10 out of 31 patients (32%). NICE lesions were symptomatic at time of onset in 23 of 31 patients (74%). After a mean follow-up of 25±26 months, 25 patients (81%) were asymptomatic or minimally symptomatic without disability (modified Rankin Scale (mRS) score 0–1) at last follow-up while 4 (13%) presented with mild disability (mRS score 2). Clinical follow-up data were unavailable for two patients. Follow-up MRI (available in 27 patients; mean time interval after onset of 22±22 months) demonstrated persistent enhancement in 71% of cases. Conclusions The clinical spectrum of NICE lesions following aneurysm EVT therapy spans a wide range of neurological symptoms. Clinical course is most commonly benign, although persistent long-term enhancement is frequent