Investigative approach to improve hot water system hydraulics through temperature monitoring to reduce building environmental quality hazard associated to Legionella

Several countries have promulgated control measures and design guidelines to limit the proliferation of Legionella within hot water distribution systems (HWDS). However, there is little information on how to assess and improve existing HWDS unable to maintain water temperatures >= 55 degrees C throughout the system. A 50-year old hot water system of a 10 story hospital was investigated in terms of temperature distribution and Legionella pneumophila prevalence. Concentrations of L. pneumophila were correlated with the maximum temperature reached at the tap, with a significant decrease observed at T >= 55 degrees C. Continuous temperature and flow monitoring was performed on the overall HWDS, characterizing the principal and secondary horizontal return loops for all 9 wings, and detailed investigations of the secondary vertical return loops was completed in Wing 3. Results indicated the system inability to systematically maintain desired operating temperatures of 55 degrees C. The deficient hydraulic distribution was the root cause of the poor temperature maintenance throughout the secondary loops, but defective devices were also identified as playing an important role in sectorial temperature failure. A simple stepwise investigative approach was developed to identify hydraulic deficiencies. The implementation of flow restrictions on identified recirculation loops and increased pumping efficiency was conducted within a short period of 2 months, with no major system upgrade. These corrective measures resulted in a balanced system with increased flow velocities (>0.2 m/s). As a result, the proportion of taps achieving 55 degrees C within 2 min increased from 11% to 74% and L. pneumophila prevalence decreased from 93.1% to 46.1% after 4 weeks. (C) 2016 The Authors. Published by Elsevier Ltd

Fluorescence probes: towards automatic coagulant dosing

There is a current lack of accurate tools to determine the concentration of cyanobacteria in situ.  Besides, cyanobacterial blooms have to be carefully monitored in reservoirs as they are more frequent because of climate change and can lead to potential released of toxins, along with other components. This project investigates the possible use of fluorescent probes to measure the concentration of different types of organic matter released by the algae. Three different species of toxic cyanobacteria were chosen to carry out this research as they are representative of the local harmful blooms found across Australia. Furthermore, the efficiency of two different chemicals (powdered activated carbon, also known as PAC, and alum) used in drinking water treatment plants were investigated, in order to determine a method for automatic dosage adjustment in water treatment plant. The organic matter was characterized by LC-OCD and fluorescence spectroscopy and statistical analysis such as principal component analysis was performed on the generated data. General characterization of the different species was firstly performed and globally, similar comportments were observed among the three cyanobacteria species. There is indeed a general increase in the release of organic material throughout the cell’s growth phase. Results from the jar tests showed that PAC mainly targeted humic-like substances and building blocks, which are middle size particles. The average removal rate obtained was 40µg/L per mg/L of PAC added into the water. Therefore, there is indication that the decreased efficiency for the removal of the taste and odor compounds observed in certain plants can be partially attributed to direct competition of organic matter adsorption onto PAC instead of a blockage of the PAC pores by larger particles. On the other hand, alum was able to remove large particles, particularly biopolymers and also humic-substances. However, a great increase of the low molecular weight molecules at very high doses of alum was seen, which suggest that a too high dose of alum is toxic for the algae cells. Based on the bench scale testing the recommended dose of 50 mg/L seems to be optimum for the studied water treatment plant. Specific ultraviolet absorbance and dissolved organic carbon measurements were also investigated and good correlations were found between the concentration of humic-like substances and absorbance, confirming that they are good measure to assess the content of organic matter in the water. However, as the slope coefficient of the linear trend varied between the species, it was not possible to obtain a common conversion factor for all the species. Finally, one fluorophore was found in common to all the samples and is characterized by the excitation-emission wavelength: 240/440 nm. Correlations with the chromatography’s results were investigated and this component seems to match the biopolymers and humic-like substances concentrations. Furthermore, its intensity decreases continuously with the addition of PAC whereas a drop was observed at the lower doses of alum. In regards on these findings, a method for automatic chemicals dosing from the fluorescence measures was proposed.Detta examensarbete handlar om hur dricksvattenkvalitet kan kontrolleras och övervakas i vattenreningsverk. Nu existerar  inte någon exakt metod för att bestämma koncentrationen av cyanobakterier i vatten då det finns många olika arter. Men det är viktigt att övervaka algers tillväxt in i vattenreningsverk för de kan släppa ut skadliga ämnen till dricksvattnet. De tre arter som studerats i detta projekt är giftiga. Det organiska materialet i råvattnet kan också blockera membranporer eller leda till n biprodukter, som är cancerframkallande. Till sist konkurrerar några organiska substansen med smak- och luktföreningar för adsorptionsställena hos det pulverformiga aktiverade kolet. Därför är smaken och luktföreningarna inte väl borttagna, vilket leder till kundernas klagomål. Cyanobakterier måste övervakas noggrant.                            För att bestämma biologisk och kemisk egenskap hos vatten används flera tekniker för närvarande. I examensarbetet har undersökningar med vätskekromatografi och fluorescensteknik företagits. Kromatografi användes för att klassificera den organiska substansen i mindre grupper: biopolymerer, humus substanser, byggstenar och neutralmolekyler med låg molekylvikt (LMVN). Statistisk analys med R, inklusive huvudkomponentanalys företogs på insamlade data. Fluorescensdata registrerades också och visas i en excitationsutsläppsmatris.                            Experimenten reproducerade en behandlingsprocess och undersökte effektiviteten hos två kemikalier: pulveriserat aktivt kol (PAK) och alun. Resultaten visade att humusämnen   och dess byggstenar var väl borttagna av PAK medan även biopolymerer och humusämnen var väl bortagna av alun. Emellertid var en för hög dos av alun skadlig eftersom det ledde till en ökad frisättning av LMVN. I synnerhert kunde PAK ta bort 40µg/L av både humusämnen och dess byggstenar per mg/L av PAK tillagd. Det föreslår att de är de viktigaste konkurrenterna och att endast direkt konkurrens för adsorptionsställena sker. Om det fanns blockeringsfenomen, skulle det också finnas en minskning för biopolymererna. Den optimala doseringen av alun som bestämdes för det undersökta vattenreningsverket var 50 mg/L. Det kunde ta bort 60-70% av biopolymerer och 40-50% av humusämnen.                            Specifik ultraviolett absorbans och fluorescens registrerades. Båda visade riktigt bra korrelationer med humusämnen, vilket gör de till bra verktyg för att bedöma vattenkvaliteten. Men det kräver fortfarande att arten av cyanobakterie urskiljs eftersom koefficientens lutningar var olika. De kan därför vara ett verktyg för att mäta koncentrationen av organisk material, men arten måste vara känd. Fluorescencedata visade en topp vid 440 nm. En parallellfaktoranalys utfördes på data och endast en komponent hittades gemensam i alla prover. Därför studerades den maximala fluorescensintensiteten hos denna komponent. Å ena sidan kunde vi observera en kontinuerlig minskning av intensiteten när PAK tillsattes. Det är därför möjligt att veta hur man justerar den kemiska doseringen från fluorescensintensiteterna. I slutet av examensarbetet föreslås en metod för automatisk kemisk dosering. Fluorescensprober kan ännu inte exakt indikera cellkoncentrationen. Men med flera sonder som riktar sig till olika våglängder kan de redan vara till stor hjälp för styrning vid vattenverk

Fluorescence probes: towards automatic coagulant dosing

There is a current lack of accurate tools to determine the concentration of cyanobacteria in situ.  Besides, cyanobacterial blooms have to be carefully monitored in reservoirs as they are more frequent because of climate change and can lead to potential released of toxins, along with other components. This project investigates the possible use of fluorescent probes to measure the concentration of different types of organic matter released by the algae. Three different species of toxic cyanobacteria were chosen to carry out this research as they are representative of the local harmful blooms found across Australia. Furthermore, the efficiency of two different chemicals (powdered activated carbon, also known as PAC, and alum) used in drinking water treatment plants were investigated, in order to determine a method for automatic dosage adjustment in water treatment plant. The organic matter was characterized by LC-OCD and fluorescence spectroscopy and statistical analysis such as principal component analysis was performed on the generated data. General characterization of the different species was firstly performed and globally, similar comportments were observed among the three cyanobacteria species. There is indeed a general increase in the release of organic material throughout the cell’s growth phase. Results from the jar tests showed that PAC mainly targeted humic-like substances and building blocks, which are middle size particles. The average removal rate obtained was 40µg/L per mg/L of PAC added into the water. Therefore, there is indication that the decreased efficiency for the removal of the taste and odor compounds observed in certain plants can be partially attributed to direct competition of organic matter adsorption onto PAC instead of a blockage of the PAC pores by larger particles. On the other hand, alum was able to remove large particles, particularly biopolymers and also humic-substances. However, a great increase of the low molecular weight molecules at very high doses of alum was seen, which suggest that a too high dose of alum is toxic for the algae cells. Based on the bench scale testing the recommended dose of 50 mg/L seems to be optimum for the studied water treatment plant. Specific ultraviolet absorbance and dissolved organic carbon measurements were also investigated and good correlations were found between the concentration of humic-like substances and absorbance, confirming that they are good measure to assess the content of organic matter in the water. However, as the slope coefficient of the linear trend varied between the species, it was not possible to obtain a common conversion factor for all the species. Finally, one fluorophore was found in common to all the samples and is characterized by the excitation-emission wavelength: 240/440 nm. Correlations with the chromatography’s results were investigated and this component seems to match the biopolymers and humic-like substances concentrations. Furthermore, its intensity decreases continuously with the addition of PAC whereas a drop was observed at the lower doses of alum. In regards on these findings, a method for automatic chemicals dosing from the fluorescence measures was proposed.Detta examensarbete handlar om hur dricksvattenkvalitet kan kontrolleras och övervakas i vattenreningsverk. Nu existerar  inte någon exakt metod för att bestämma koncentrationen av cyanobakterier i vatten då det finns många olika arter. Men det är viktigt att övervaka algers tillväxt in i vattenreningsverk för de kan släppa ut skadliga ämnen till dricksvattnet. De tre arter som studerats i detta projekt är giftiga. Det organiska materialet i råvattnet kan också blockera membranporer eller leda till n biprodukter, som är cancerframkallande. Till sist konkurrerar några organiska substansen med smak- och luktföreningar för adsorptionsställena hos det pulverformiga aktiverade kolet. Därför är smaken och luktföreningarna inte väl borttagna, vilket leder till kundernas klagomål. Cyanobakterier måste övervakas noggrant.                            För att bestämma biologisk och kemisk egenskap hos vatten används flera tekniker för närvarande. I examensarbetet har undersökningar med vätskekromatografi och fluorescensteknik företagits. Kromatografi användes för att klassificera den organiska substansen i mindre grupper: biopolymerer, humus substanser, byggstenar och neutralmolekyler med låg molekylvikt (LMVN). Statistisk analys med R, inklusive huvudkomponentanalys företogs på insamlade data. Fluorescensdata registrerades också och visas i en excitationsutsläppsmatris.                            Experimenten reproducerade en behandlingsprocess och undersökte effektiviteten hos två kemikalier: pulveriserat aktivt kol (PAK) och alun. Resultaten visade att humusämnen   och dess byggstenar var väl borttagna av PAK medan även biopolymerer och humusämnen var väl bortagna av alun. Emellertid var en för hög dos av alun skadlig eftersom det ledde till en ökad frisättning av LMVN. I synnerhert kunde PAK ta bort 40µg/L av både humusämnen och dess byggstenar per mg/L av PAK tillagd. Det föreslår att de är de viktigaste konkurrenterna och att endast direkt konkurrens för adsorptionsställena sker. Om det fanns blockeringsfenomen, skulle det också finnas en minskning för biopolymererna. Den optimala doseringen av alun som bestämdes för det undersökta vattenreningsverket var 50 mg/L. Det kunde ta bort 60-70% av biopolymerer och 40-50% av humusämnen.                            Specifik ultraviolett absorbans och fluorescens registrerades. Båda visade riktigt bra korrelationer med humusämnen, vilket gör de till bra verktyg för att bedöma vattenkvaliteten. Men det kräver fortfarande att arten av cyanobakterie urskiljs eftersom koefficientens lutningar var olika. De kan därför vara ett verktyg för att mäta koncentrationen av organisk material, men arten måste vara känd. Fluorescencedata visade en topp vid 440 nm. En parallellfaktoranalys utfördes på data och endast en komponent hittades gemensam i alla prover. Därför studerades den maximala fluorescensintensiteten hos denna komponent. Å ena sidan kunde vi observera en kontinuerlig minskning av intensiteten när PAK tillsattes. Det är därför möjligt att veta hur man justerar den kemiska doseringen från fluorescensintensiteterna. I slutet av examensarbetet föreslås en metod för automatisk kemisk dosering. Fluorescensprober kan ännu inte exakt indikera cellkoncentrationen. Men med flera sonder som riktar sig till olika våglängder kan de redan vara till stor hjälp för styrning vid vattenverk

Insights into the genetic makeup of French Polynesian peripheral populations of the small giant clam Tridacna maxima

The small giant clam, Tridacna maxima, is distributed from the Red Sea and East African coast to French Polynesia. Across this widespread Indo‐Pacific range, T. maxima shows strong population structure, in agreement with its limited dispersal abilities. Peripheral populations may have smaller effective population sizes, increasing their vulnerability under any environmental changes. Understanding evolutionary processes at play in such regions located at the edges of T. maxima distribution is a prerequisite in the context of transfers and restocking programmes. In this study, giant clams were sampled from 14 atolls and islands within four archipelagos in the peripheral region of French Polynesia, in 2001–2002 and/or in 2012–2013, then genotyped at the COI gene and at nine microsatellite loci. Mitochondrial lineages of T. maxima from French Polynesia diverged from those sampled in Micronesia, Melanesia, the Coral Triangle and the Red Sea by 6.6–7.3%. Within French Polynesia, significant genetic structure was found, indicating restricted gene flow, and it was stable through time. Most of the genetic variation at microsatellite loci was between archipelagos. The most differentiated archipelago was the most geographically isolated (the Austral Islands). The current patterns of genetic structuring of T. maxima in French Polynesia probably result from long‐term genetic isolation with limited dispersal ability. In addition, these results underlined that sufficiently large populations of T. maxima have persisted in the Central Pacific during the last sea‐level regression. Strategies to optimize transfers and restocking programmes should be designed to preserve the genetic diversity and structure observed here, to avoid the risks of altering the genetic structure, allele loss and/or introduction of maladapted alleles in the receiving populations