Suitability of combined sewers for the installation of heat exchangers

Stránský, David; Kabelkova, I.; Bareš, Vojtěch; Stastna, G.; Suchorab, Zbigniew

doi:10.1515/eces-2016-0006

Cited by 5 publications

(4 citation statements)

References 25 publications

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“…In a combined sewer system, the sediment could be washed out during the rain events; in contrast, in dry weather seasons the sediment layer is build-up as the top layer is formed. In real sewer environments, the top layer is formed from organic material and bacterial biofilm and its amount decreases with increasing shear stress [40]. Due to the proportion of fine sediments and biofilm on the surface and their hydraulic conductivity [41], we can assume that no significant subsurface (hyporheic) flow will be formed in the sediments, so the subsurface flow does not form a significant proportion of dead zones.…”

Section: Discussionmentioning

confidence: 99%

Impact of Sediment Layer on Longitudinal Dispersion in Sewer Systems

Sokáč

Velísková

2021

Water

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Experiments focused on pollution transport and dispersion phenomena in conditions of low flow (low water depth and velocities) in sewers with bed sediment and deposits are presented. Such conditions occur very often in sewer pipes during dry weather flows. Experiments were performed in laboratory conditions. To simulate real hydraulic conditions in sewer pipes, sand of fraction 0.6–1.2 mm was placed on the bottom of the pipe. In total, we performed 23 experiments with 4 different thicknesses of sand sediment layers. The first scenario is without sediment, the second is with sediment filling 3.4% of the pipe diameter (sediment layer thickness = 8.5 mm), the third scenario represents sediment filling 10% of the pipe diameter (sediment layer thickness = 25 mm) and sediment fills 14% of the pipe diameter (sediment layer thickness = 35 mm) in the last scenario. For each thickness of the sediment layer, a set of tracer experiments with different flow rates was performed. The discharge ranges were from (0.14–2.5)·10−3 m3·s−1, corresponding to the range of Reynolds number 500–18,000. Results show that in the hydraulic conditions of a circular sewer pipe with the occurrence of sediment and deposits, the value of the longitudinal dispersion coefficient Dx decreases almost linearly with decrease of the flow rate (also with Reynolds number) to a certain limit (inflexion point), which is individual for each particular sediment thickness. Below this limit the value of the dispersion coefficient starts to rise again, together with increasing asymmetricity of the concentration distribution in time, caused by transient (dead) storage zones.

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Section: Discussionmentioning

confidence: 99%

Impact of Sediment Layer on Longitudinal Dispersion in Sewer Systems

Sokáč

Velísková

2021

Water

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“…42, №3 на прикладі міста Градец Кралове, Чехія (90 тис. мешканців) наведено в [8]. Класифікаційна схема, що включає такі критерії, як теоретично доступна теплота, діаметр каналізації, кількість паралельних модулів теплообмінника в перерізі каналізації, гідравлічні умови та потенційне забруднення за рахунок росту біоплівки.…”

Section: рис 1 існуючі системи утилізації стічної води [1] а -системи які можуть бути встановлені на очисних спорудах; б -системи які можunclassified

Technologies, Systems, and Equipment for Wastewater Heat Utilization (Review)

Басок

Novitska

Гончарук

2020

ttpe

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The paper analyzes research, technologies, and equipment related to wastewater heat utilization systems. The main factors influencing the development of the industry and the implementation of such systems are given. Such factors include: social, political, economic, technological, legal and environmental. The classification of technologies and equipment for wastewater heat utilization according to the place of heat extraction is given. Namely, low potential wastewater heat can be collected at the treatment plants, in sewer collectors leading to treatment plants and directly in houses. The paper describes the available research in the scientific literature on these three categories The global scientific community is working to create efficient wastewater heat recovery systems. The environmental situation requires greater use of wastewater recovery systems. An important issue is to increase awareness and education of the population, as this approach will increase the degree of implementation of wastewater heat utilization systems in residential buildings.

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“…This phenomenon must be taken into account in the modelling the dispersion and flows in sewer systems (Manina et al, 2020). However, also in combined sewer systems can fine sediment particles form so-called cohesive sediment, which is hardly removable by the self-cleaning ability of the sewer pipes (insufficient shear stress induced by the stormwater flows) (Stransky et al, 2016). Such sediments can be removed only by using mechanical cleaning procedures and technology, applied by the sewer system operator.…”

Section: Introductionmentioning

confidence: 99%

Dispersion process in conditions of real sewer systems – in situ experiments

Sokáč¹,

Velísková²

2022

ahs

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A general assumption of most current models used to simulate flow in sewer systems (pipes) is that the sewers are considered as prismatic channels. However, in real conditions there are many factors, which affect the real flow. One of them is the occurrence of the sediments and deposits in sewer pipes, which significantly changes the flow conditions, as well as the dispersion process in sewer systems by creation of "dead zones". Paper describes the effects of these zones on hydrodynamic dispersion process, which are particularly noticeable in hydraulic conditions of low flow rates in sewer system (sanitary, flow rates during dry period without rain …). In the study, there were applied two types of tracers and both used substances give identical results. Experimental results show that even though sewer pipes are considered as prismatic hydraulic channels, in the real conditions some irregularities resulted with dead zones creation are presented. Their influence on the mass concentration time-course shape is depending on the sediment layer thickness. Gaussian approximation of the one-dimensional advection dispersion equation for instantaneous pollution entry is not suitable for the sewer pipes with sediments occurrence. In case of sediments presence, the GEV and Gumbel's approximation function looks to be more accurate.

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Suitability of combined sewers for the installation of heat exchangers

Cited by 5 publications

References 25 publications

Impact of Sediment Layer on Longitudinal Dispersion in Sewer Systems

Impact of Sediment Layer on Longitudinal Dispersion in Sewer Systems

Technologies, Systems, and Equipment for Wastewater Heat Utilization (Review)

Dispersion process in conditions of real sewer systems – in situ experiments

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