Réduction et contrôle du foisonnement filamenteux des boues activées par application d'un régime turbulent

Le foisonnement filamenteux des boues activées est un problème important dans les stations d'épuration du type Boues Activées, car il peut entraîner des pertes de biomasse avec l'eau épurée. Les techniques de lutte utilisées actuellement sont, soit des techniques dites « biologiques » (sélecteurs), soit des techniques chimiques (floculants, biocides). L'objectif de notre travail a été la mise au point d'un procédé original basé sur la création d'une zone de turbulence pour casser les réseaux filamenteux. La réduction et le contrôle du bulking sont obtenus par passage (de durée limitée T1) de la biomasse dans un système venturi, équipée d'une prise d'air. L'efficacité du procédé dépend principalement de la turbulence due à l'auto-aspiration d'air au niveau du rétrécissement du venturi. Cette turbulence contribue d'une part au mécanisme de « cisaillement » des filaments, et d'autre part à la qualité de l'effluent sortant. Une gestion adaptée (aération séquentielle en procédé à faible charge) permet d'obtenir, outre une amélioration de la décantation, une amélioration de l'élimination de l'azote. De plus, le contrôle de la biomasse optimise l'élimination de la pollution carbonée.The loss of biomass in a waste water plant as a result of sludge bulking is an important problem. Biological (ex.: selector configuration) or chemical (ex. : floculating reagents, biocides...) methods habe been used in order to control bulking. A new process based on the generation of turbulence to break the filaments is described. To reduce and control sludge bulking, the biomass is pumped through a venturi equipped with an air inlet. Figure 1 represents the pilot scheme. Two processes can be used : the emulsor with air is introduced on recycling of sludge or is placed in an independent loop. Here, it is the latter that has been used.We tried to reduce bulking by mechanical treatment. The hydrodynamic efficiency of the process depends mostly on the degree of turbulence generated by the waters speed and by the suction of air in the constricted part of the venturi.During the first trials on the plant, we defined the maximum turbulence allowed in order not to break the floc. We could not use a big aeration to prevent defloculation.The main factors to reduce bulking are :- the sequences of usage of the emulsor venturi (the periodicity of the treatment is T),- the speed of the water in the nozzle of the venturi (we can refer to the Reynolds Number Re = Ud/ʋ; but this number can’t really represent the turbulence created),- the duration of the emulsor's application. The emulsor venturi is used during a period T1 with a periodicity T (T>T1), with T1 : n X (VR/qv) where VR/qv is the contact time in the venturi and n is the frequence of recycling.During the period T, it is possible to use continuous aeration or to work with sequential aeration.a) continuous aeration|_________________________| TTime between two applications of the venturi|_______________| T1Venturi durationThe process is the same as the aeration of activated sludge. COD is reduced but only with low load, significant nitrification occurs. Figure 5 shows the efficiency of the continuous aeration process especially versus the sludge index parameter.b) sequential aerationAs we try to remove nitrogen, the sequential aeration is more useful than continuous aeration. A cycle is divided in two periods (T2, T3 with T = T2 + T3), and of course, the duration of the venturi use equal to T1.|_________________________| TTime between two applications of the venturi|_____________| T1Venturi duration|_________________| T2Aeration duration          |_____| T3Anoxic periodFigures 6 and 7 show the efficiency of the emulsor if we consider lB (sludge index) as the main parameter for the sequential operation (T2, T3) and it's also possible to obtain a good removal of nitrogen pollution.Our operations parameters were for these experiments :T = 8 or 12 hoursT1 between 20 min. and 1 hourT2 between 4 and 5 hoursThis process is now patiented and the first industrial applications are now defined

Reply to Worth et al

TO THE EDITOR—We thank Worth and colleagues for reflecting on some important points related to our recent study where we reported a 63% reduction in hospital-onset (HO) Staphylococcus aureus bacteremia (SAB) in Australia

La naturaleza llama. Urbanitas en busca de la recuperación del primer espacio público

La naturaleza es el primer espacio público del ser humano. Su relación psicoafectiva con ella, la biofilia, se asocia a su respeto, a la satisfacción con la propia vida y la adopción de actitudes sustentables. Esto tiene especial sentido en las urbes contemporáneas, caracterizadas por un alto grado de desconexión natural, a su vez asociadas a un alto grado de insustentabilidad. Mediante la revisión de literatura y materiales relacionados con el tema, la realización de entrevistas, encuestas y experimentos de campo, se estudió cómo influye la biofilia en la adopción de comportamientos ecológicos en Guadalajara, Jalisco. Por medio de entrevistas, se obtuvo información de urbanitas que optaron por estilos de vida más cercanos a lo natural. Se realizaron encuestas en sitios en los que los urbanitas buscan reconectarse con la naturaleza, con el fin de detectar inferencias causales entre actitudes sustentables y sus relaciones biofílicas. Durante el proceso, se realizaron experimentos de campo dentro del marco de la observación participante en entornos naturales de Guadalajara. Así, se detectó un movimiento social en ciernes, influido por experiencias en la naturaleza (pasadas y presentes), que adopta comportamientos sustentables (acciones) por razones emotivas (amor por la naturaleza) más que por morales o racionales. Se presentan algunas de las características más importantes de este movimiento social que busca aumentar su vínculo con la naturaleza; esto se discute en términos de los beneficios que el concepto biofilia tiene para la sustentabilidad de los entornos urbanos.Consejo Nacional de Ciencia y Tecnologí

Response of Invasive Longhorn Beetles (Coleoptera: Lamiinae) to Known Cerambycid Aggregation-Sex Pheromones in the Puna District of Hawaii Island

The Queensland longhorn borer (QLB; Acalolepta aesthetica [Olliff 1890]; Coleoptera: Cerambycidae: Lamiinae: Monochamini) and plumeria long- horn borer (PLB; Lagocheirus obsoletus [Thomson 1778] = Lagocheirus undatus [Voet 1778]; Coleoptera: Cerambycidae: Lamiinae: Acanthocini) are invasive longhorn beetle species that have become established on the island of Hawaii. Both QLB and PLB are polyphagous. Known hosts of QLB include cacao, citrus, kukui, and breadfruit in Hawaii, and QLB are known to attack live, healthy trees. Currently the beetle occurs in the Puna district of the island, but its range is expanding. PLB is a pest of plumeria and other ornamental plants throughout the state of Hawaii and elsewhere. As a first step towards developing a monitoring tool for these invasive beetles, we tested four known aggregation-sex pheromones of cerambycids in this subfamily—monochamol, fuscumol acetate, fuscumol, and geranylacetone—that have proven effective for attracting more than 30 lamiine species in different areas of the world. When tested in panel traps, these compounds individually and in a blend attracted 9 QLB total, which was not significantly different than the 5 QLB captured in solvent control traps. In contrast, traps baited with one of the tested compounds, fuscumol acetate, captured significantly more PLB than solvent blank control traps. We discuss future research directions for developing attractants using chemical ecology approaches to monitor QLB and PLB

Five-year antimicrobial resistance patterns of urinary escherichia coli at an Australian tertiary hospital: Time series analyses of prevalence data

This study describes the antimicrobial resistance temporal trends and seasonal variation of Escherichia coli (E. coli) urinary tract infections (UTIs) over five years, from 2009 to 2013, and compares prevalence of resistance in hospital- and community-acquired E. coli UTI. A cross sectional study of E. coli UTIs from patients attending a tertiary referral hospital in Canberra, Australia was undertaken. Time series analysis was performed to illustrate resistance trends. Only the first positive E. coli UTI per patient per year was included in the analysis. A total of 15,022 positive cultures from 8724 patients were identified. Results are based on 5333 first E. coli UTIs, from 4732 patients, of which 84.2% were community-acquired. Five-year hospital and community resistance rates were highest for ampicillin (41.9%) and trimethoprim (20.7%). Resistance was lowest for meropenem (0.0%), nitrofurantoin (2.7%), piperacillin-tazobactam (2.9%) and ciprofloxacin (6.5%). Resistance to amoxycillin-clavulanate, cefazolin, gentamicin and piperacillin-tazobactam were significantly higher in hospital- compared to community-acquired UTIs (9.3% versus 6.2%; 15.4% versus 9.7%; 5.2% versus 3.7% and 5.2% versus 2.5%, respectively). Trend analysis showed significant increases in resistance over five years for amoxycillin-clavulanate, trimethoprim, ciprofloxacin, nitrofurantoin, trimethoprim-sulphamethoxazole, cefazolin, ceftriaxone and gentamicin (P < 0.05, for all) with seasonal pattern observed for trimethoprim resistance (augmented Dickey-Fuller statistic = 4.136; P = 0.006). An association between ciprofloxacin resistance, cefazolin resistance and ceftriaxone resistance with older age was noted. Given the relatively high resistance rates for ampicillin and trimethoprim, these antimicrobials should be reconsidered for empirical treatment of UTIs in this patient population. Our findings have important implications for UTI treatment based on setting of acquisition

Five-Year Antimicrobial Resistance Patterns of Urinary Escherichia Coli at an Australian Tertiary Hospital: Time Series Analyses of Prevalence Data

This study describes the antimicrobial resistance temporal trends and seasonal variation of Escherichia coli (E. coli) urinary tract infections (UTIs) over five years, from 2009 to 2013, and compares prevalence of resistance in hospital- and community-acquired E. coli UTI. A cross sectional study of E. coli UTIs from patients attending a tertiary referral hospital in Canberra, Australia was undertaken. Time series analysis was performed to illustrate resistance trends. Only the first positive E. coli UTI per patient per year was included in the analysis. A total of 15,022 positive cultures from 8724 patients were identified. Results are based on 5333 first E. coli UTIs, from 4732 patients, of which 84.2% were community acquired. Five-year hospital and community resistance rates were highest for ampicillin (41.9%) and trimethoprim (20.7%). Resistance was lowest for meropenem (0.0%), nitrofurantoin (2.7%), piperacillin-tazobactam (2.9%) and ciprofloxacin (6.5%). Resistance to amoxycillin-clavulanate, cefazolin, gentamicin and piperacillin-tazobactam were significantly higher in hospital- compared to community-acquired UTIs (9.3% versus 6.2%; 15.4% versus 9.7%; 5.2% versus 3.7% and 5.2% versus 2.5%, respectively). Trend analysis showed significant increases in resistance over five years for amoxycillin-clavulanate, trimethoprim, ciprofloxacin, nitrofurantoin, trimethoprim-sulphamethoxazole, cefazolin, ceftriaxone and gentamicin (