18 research outputs found
An overview on the reactors to study drinking water biofilms
The development of biofilms in drinking water distribution systems (DWDS) can cause pipe degradation, changes in the water organoleptic properties but the main problem is related to the public health. Biofilms are the main responsible for the microbial presence in drinking water (DW) and can be reservoirs for pathogens. Therefore, the understanding of the mechanisms underlying biofilm formation and behavior is of utmost importance in order to create effective control strategies. As the study of biofilms in real DWDS is difficult, several devices have been developed. These devices allow biofilm formation under controlled conditions of physical (flow velocity, shear stress, temperature, type of pipe material, etc), chemical (type and amount of nutrients, type of disinfectant and residuals, organic and inorganic particles, ions, etc) and biological (composition of microbial community e type of microorganism and characteristics) parameters, ensuring that the operational conditions are similar as possible to the DWDS conditions in order to achieve results that can be applied to the real scenarios. The devices used in DW biofilm studies can be divided essentially in two groups, those usually applied in situ and the bench top laboratorial reactors. The selection of a device should be obviously in accordance with the aim of the study and its advantages and limitations should be evaluated to obtain reproducible
results that can be transposed into the reality of the DWDS. The aim of this review is to provide an overview on the main reactors used in DW biofilm studies, describing their characteristics and applications, taking into account their main advantages and limitations.This work was supported by the Operational Programme for Competitiveness Factors COMPETE and by Portuguese Foundation for Science and Technology through Project Phyto disinfectants - PTDC/DTPSAP/1078/2012 (COMPETE: FCOMP-01-0124-FEDER-028765), the Post-Doc grant awarded to Lucia Simoes (SFRH/BPD/81982/2011). Also, this work was undertaken as part of the European Research Project SUS-CLEAN (Contract n_FP7-KBBE-2011-5, project number: 287514) and the COST Action FA1202. The authors are solely responsible for this work. It does not represent the opinion of the Community, and the Community is not responsible for any use that might be made of data appearing herein
The Role of Ethical Funds in Influencing Sustainable Business Practice
Den snabbt vÀxande etiska fondmarknaden Àr dels en respons pÄ ökad efterfrÄgan frÄn investerare, och dels en reaktion pÄ ett ökat intresse och förstÄelse för miljö och etiska frÄgor frÄn företagens sida. Denna studie diskuterar detta fÀlt frÄn företagens perspektiv. Ett flertal studier har lagt fram teorier om att socialt ansvarsfullt investerande [SRI] och etiska fonder specifikt, har potential att förÀndra företagens beteende. Denna uppsats placerar etiska fonder bland generella drivkrafter som har en effekt pÄ dagens företag, och analyserar etiska fonder utifrÄn deras roll som en drivkraft nÀr det gÀller pÄverkan av företag som dessa investerar i. FrÄn KPA Pensions etiska fondinnehav, deltog 19 företag i studien. Genom enkÀt och intervjuer har denna studie funnit att de etiska fonderna inte kan sÀgas vara en drivkraft nÀr det gÀller att pÄverka företagen gÀllande miljö och CSR frÄgor. Kunder, investerare och företagens egna, inre engagemang verkar vara de frÀmsta aktörerna och drivkrafterna för att uppmuntra till arbete med dessa frÄgor. Enligt företagen sjÀlva, dock, finns det fortfarande positiva effekter som de etiska fonderna ger upphov till i form av positiv respons frÄn kunder, ökad goodwill och ökade markandsandelar. En del av företagen menar att de inte har haft lika mycket kontakt med KPA Pension som de kanske hade velat, men kÀnner att dialogen och samarbetet mellan dem och KPA Pension har varit och Àr vÀrdefullt. Dessutom visar företagen tecken pÄ förstÄelse att ett arbete med miljö och CSR- frÄgor Àr ett kontinuerligt sÄdant, och dÀrför borde relationen mellan företagen och KPA Pension förbÀttras
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Characterisation of the behaviour of particles in biofilters for pre-treatment of drinking water
Biofiltration of surface water was examined using granular activated carbon (GAC) and expanded clay (EC). Particle removal was 60-90%, measured by flow cytometry, which enabled discrimination between total- and autofluorescent particles (microalgae) in size ranges of 0.4-1 and 1-15 mu m, and measured by on-line particle counting. Total particles were removed at a higher degree than autofluorescent particles. The biofilters were also challenged with 1 mu m fluorescent microspheres with hydrophobic and hydrophilic surface characteristics and bacteriophages (Salmonella typhimurium 2813). Added microspheres were removed at 97-99% (hydrophobic) and 85-89% (hydrophilic) after 5 hydraulic residence times (HRT) and microspheres retained in the biofilter media were slowly detaching into the filtrate for a long time after the addition. Removal of bacteriophages (5 HRT) was considerably lower at 40-59%, and no long-lasting detachment was observed. A comparison of experimental data with theoretical predictions for removal of particles in clean granular media filters revealed a similar or higher removal of particles around 1 mu m in size than predicted, while bacteriophages were removed at a similar or lesser extent than predicted. The results highlight the selectivity and dynamic behaviour of the particle removal processes and have implications for operation and microbial risk assessment of a treatment train with biofilters as pre-treatment. (c) 2005 Elsevier Ltd. All rights reserved