Changes in biofilm composition and microbial water quality in drinking water distribution systems by temperature increase induced through thermal energy recovery

Ahmad, Jawairia Imtiaz; Dignum, Marco; Liu, Gang; Medema, Gertjan; Hoek, Jan Peter van der

doi:10.1016/j.envres.2020.110648

Cited by 20 publications

(24 citation statements)

References 43 publications

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“…On the other hand, the T max is limited by the effects on the microbiological quality of drinking water and the standard for the drinking water temperature at the customer's tap (25 • C). The former has been already described, and temperatures up to 30 • C have shown no negative impact [12,24]. However, this is specifically the case for non-chlorinated DWDSs with microbiologically stable water and the absence of temperature-sensitive opportunistic pathogens, such as Legionella spp.…”

Section: Potential Energy and Cooling Down Of Drinking Water After Cold Recoverymentioning

confidence: 80%

“…Our previous pilot scale studies revealed that, with a drinking water temperature of 25 • C and 30 • C after cold recovery, no negative effects were observed in the water phase in terms of water quality parameters (like microbial activity: total biomass and cell counts) and proliferation of opportunistic pathogens (Legionella spp.) [24]. However, the elevated drinking water temperatures, due to cold recovery, did enhance the initial biofilm growth (in terms of biomass) in the first 2-3 months of operation, compared to the biofilm growth in a reference system, in which no cold recovery was applied.…”

Section: Introductionmentioning

confidence: 84%

“…Later (after 3-4 months), when the biofilm reached its steady growth phase, comparable biomass was observed in the systems with cold recovery and the reference system. Within the initial three months of applying cold recovery at the pilot plant scale, drinking water quality parameters (biomass activity and cell concentration) increased after cold recovery compared to the reference system but stayed within the standards of the Dutch drinking water regulation [24].…”

Section: Introductionmentioning

confidence: 90%

“…For this study, the operational parameters, such as inlet feed water temperature, flow rate, outgoing water temperature after cold recovery, soil temperature and pipe material, of a full-scale cold recovery (TED) plant of Sanquin-Waternet in Amsterdam were used [15]. Based on the results of the previous pilot scale studies [12,24], where no negative effects of cold recovery were observed on the microbial drinking water quality with exit temperatures (after leaving the heat exchanger) up to 30 • C, four values of T max were chosen for this study, 15, 20, 25 and 30 • C, respectively (defined as a threshold for cold recovery). The value of 15 • C is the one currently allowed in the full-scale operational system.…”

Section: Methodsmentioning

confidence: 99%

See 3 more Smart Citations

Maximizing Thermal Energy Recovery from Drinking Water for Cooling Purpose

Ahmad

Giorgi²,

Zlatanović

et al. 2021

Energies

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Drinking water distribution networks (DWDNs) have a huge potential for cold thermal energy recovery (TED). TED can provide cooling for buildings and spaces with high cooling requirements as an alternative for traditional cooling, reduce usage of electricity or fossil fuel, and thus TED helps reduce greenhouse gas (GHG) emissions. There is no research on the environmental assessment of TED systems, and no standards are available for the maximum temperature limit (Tmax) after recovery of cold. During cold recovery, the water temperature increases, and water at the customer’s tap may be warmer as a result. Previous research showed that increasing Tmax up to 30 °C is safe in terms of microbiological risks. The present research was carried out to determine what raising Tmax would entail in terms of energy savings, GHG emission reduction and water temperature dynamics during transport. For this purpose, a full-scale TED system in Amsterdam was used as a benchmark, where Tmax is currently set at 15 °C. Tmax was theoretically set at 20, 25 and 30 °C to calculate energy savings and CO2 emission reduction and for water temperature modeling during transport after cold recovery. Results showed that by raising Tmax from the current 15 °C to 20, 25 and 30 °C, the retrievable cooling energy and GHG emission reduction could be increased by 250, 425 and 600%, respectively. The drinking water temperature model predicted that within a distance of 4 km after TED, water temperature resembles that of the surrounding subsurface soil. Hence, a higher Tmax will substantially increase the TED potential of DWDN while keeping the same comfort level at the customer’s tap.

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Section: Potential Energy and Cooling Down Of Drinking Water After Cold Recoverymentioning

confidence: 80%

Section: Introductionmentioning

confidence: 84%

Section: Introductionmentioning

confidence: 90%

Section: Methodsmentioning

confidence: 99%

See 2 more Smart Citations

Maximizing Thermal Energy Recovery from Drinking Water for Cooling Purpose

Ahmad

Giorgi²,

Zlatanović

et al. 2021

Energies

Self Cite

View full text Add to dashboard Cite

show abstract

“…Bacterial communities composing the biofilm and producing extracellular polymeric substances (EPS) necessary for the biofilm integrity are subjected to this temperature change and may adapt. There is, however, limited literature available on its effect on biofilm composition since most research studies were performed under isothermal conditions [13][14][15]. Among the few studies considering the impact of thermal gradient, Yang et al have shown that co-current or counter-current configurations of heat exchangers cause different fouling behaviors [16].…”

Section: Introductionmentioning

confidence: 99%

Assessment of the Impact of Temperature on Biofilm Composition with a Laboratory Heat Exchanger Module

et al. 2021

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Temperature change over the length of heat exchangers might be an important factor affecting biofouling. This research aimed at assessing the impact of temperature on biofilm accumulation and composition with respect to bacterial community and extracellular polymeric substances. Two identical laboratory-scale plate heat exchanger modules were developed and tested. Tap water supplemented with nutrients was fed to the two modules to enhance biofilm formation. One “reference” module was kept at 20.0 ± 1.4 °C and one “heated” module was operated with a counter-flow hot water stream resulting in a bulk water gradient from 20 to 27 °C. Biofilms were grown during 40 days, sampled, and characterized using 16S rRNA gene amplicon sequencing, EPS extraction, FTIR, protein and polysaccharide quantifications. The experiments were performed in consecutive triplicate. Monitoring of heat transfer resistance in the heated module displayed a replicable biofilm growth profile. The module was shown suitable to study the impact of temperature on biofouling formation. Biofilm analyses revealed: (i) comparable amounts of biofilms and EPS yield in the reference and heated modules, (ii) a significantly different protein to polysaccharide ratio in the EPS of the reference (5.4 ± 1.0%) and heated modules (7.8 ± 2.1%), caused by a relatively lower extracellular sugar production at elevated temperatures, and (iii) a strong shift in bacterial community composition with increasing temperature. The outcomes of the study, therefore, suggest that heat induces a change in biofilm bacterial community members and EPS composition, which should be taken into consideration when investigating heat exchanger biofouling and cleaning strategies. Research potential and optimization of the heat exchanger modules are discussed.

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