Hydraulic retention time
About: Hydraulic retention time is a(n) research topic. Over the lifetime, 6406 publication(s) have been published within this topic receiving 151005 citation(s).
Papers published on a yearly basis
TL;DR: In this paper, over 160 publications related to fermentative hydrogen production from wastewater and solid wastes by mixed cultures are compiled and analyzed, including pre-treatment conditions for screening hydrogen-producing bacteria from anaerobic sludge or soil, and the process and performance parameters for (2) single substrates in synthetic wastewaters, (3) actual wastewater, and (4) solid wastes.
Abstract: Over 160 publications related to fermentative hydrogen production from wastewater and solid wastes by mixed cultures are compiled and analyzed. Of the 98 reported cases, 57 used single substrates (mainly carbohydrates), 8 used actual wastewater, and 33 used solid wastes for hydrogen conversion. The key information is compiled in four tables: (1) pretreatment conditions for screening hydrogen-producing bacteria from anaerobic sludge or soil, and the process and performance parameters for (2) single substrates in synthetic wastewaters, (3) actual wastewaters, and (4) solid wastes. Process parameters discussed include pH, temperature, hydraulic retention time, seed sludge, nutrients, inhibitors, reactor design, and the means used for lowering hydrogen partial pressure. Performance parameters discussed include hydrogen yield, maximum volumetric production rate, maximum specific production rate, and conversion efficiency. The outlook for this new technology is discussed at the end.
TL;DR: Results from batch experiments suggested that Ag-NP transformation to Ag(2)S occured in the nonaerated tank within less than 2 h, which must be considered in future risk assessments.
Abstract: We investigated the behavior of metallic silver nanoparticles (Ag-NP) in a pilot wastewater treatment plant (WWTP) fed with municipal wastewater. The treatment plant consisted of a nonaerated and an aerated tank and a secondary clarifier. The average hydraulic retention time including the secondary clarifier was 1 day and the sludge age was 14 days. Ag-NP were spiked into the nonaerated tank and samples were collected from the aerated tank and from the effluent. Ag concentrations determined by inductively coupled plasma-mass spectrometry (ICP-MS) were in good agreement with predictions based on mass balance considerations. Transmission electron microscopy (TEM) analyses confirmed that nanoscale Ag particles were sorbed to wastewater biosolids, both in the sludge and in the effluent. Freely dispersed nanoscale Ag particles were only observed in the effluent during the initial pulse spike. X-ray absorption spectroscopy (XAS) measurements indicated that most Ag in the sludge and in the effluent was present a...
01 May 2000-Bioresource Technology
TL;DR: In this paper, the effect of N2 sparging on hydrogen yield was investigated in non-sterile conditions using a hydrogen-producing mixed culture previously enriched from soya bean meal.
Abstract: The effect on hydrogen yield of N2 sparging was investigated in non-sterile conditions using a hydrogen-producing mixed culture previously enriched from soya bean meal. A continuous stirred-tank reactor (CSTR) at 35°C and pH 6.0 was operated on a mineral salts-glucose (10 g l−1) medium at a hydraulic retention time (HRT) of 8.5 h, and organic loading rate of 27.02 g glucose litre reactor−1 day−1. Results are reported from an 8 week period of continuous operation, and the enrichment culture gave stable results over an extended period. A hydrogen yield of 0.85 moles H2/mole glucose consumed was obtained after 5 HRT, the gas produced being 53.4% H2. With N2 sparging at a flow rate approximately 15 times the hydrogen production rate, the hydrogen yield was 1.43 moles H2/mole glucose consumed. The specific hydrogen production rate increased from 1.446 ml hydrogen min−1g−1 biomass to 3.131 ml hydrogen min−1 g−1 biomass under sparging conditions. It is suggested that hydrogen partial pressure in the liquid phase was an important factor affecting hydrogen yield. Energy could be recovered as hydrogen from processes generating volatile fatty acids for fine chemicals and liquid bio-fuels or from acidification reactors preceding normal anaerobic biological treatment of sugary wastewaters.
01 Feb 2007-Ecological Engineering
TL;DR: In this article, the effect of temperature, hydraulic residence time (HRT), vegetation type and porous media material and grain size on the performance of horizontal subsurface flow (HSF) constructed wetlands treating wastewater, five pilot-scale units of dimensions 3.m in length and 0.75m in width were operated continuously from January 2004 until January 2006 in parallel experiments.
Abstract: In order to investigate the effect of temperature, hydraulic residence time (HRT), vegetation type and porous media material and grain size on the performance of horizontal subsurface flow (HSF) constructed wetlands treating wastewater, five pilot-scale units of dimensions 3 m in length and 0.75 m in width were operated continuously from January 2004 until January 2006 in parallel experiments. Three units contained medium gravel obtained from a quarry. The other two contained one fine gravel and one cobbles, both obtained from a river bed. The three units with medium gravel were planted one with common reeds and one with cattails, and one was kept unplanted. The other two units were planted with common reeds. Planting and porous media combinations were appropriate for comparison of the effect of vegetation and media type on the function of the system. Synthetic wastewater was introduced in the units. During the operation period, four HRTs (i.e., 6, 8, 14 and 20 days) were used, while wastewater temperatures varied from about 2.0 to 26.0 °C. The removal performance of the constructed wetland units was very good, since it reached on an average 89, 65 and 60% for BOD, TKN and ortho -phosphate (P-PO 4 3− ), respectively. All pollutant removal efficiencies showed dependence on temperature. It seems that the 8-day HRT was adequate for acceptable removal of organic matter, TKN and P-PO 4 3− for temperatures above 15 °C. Furthermore, based on statistical testing, cattails, finer media and media obtained from a river showed higher removal efficiencies of TKN and P-PO 4 3− .
TL;DR: It seems that the substrate present in the raw influent competitively inhibits the degradation of E1 and E2, and these compounds are therefore removed mainly in activated sludge compartments with low substrate loading.
Abstract: The removal of estrogens (estrone E1, estradiol E2, and ethinylestradiol EE2) was studied in various municipal wastewater treatment processes equipped for nutrient removal. A biological degradation model is formulated, and kinetic parameters are evaluated with batch experiments under various redox conditions. The resulting model calculations are then compared with sampling campaigns performed on different types of full-scale plant: conventional activated-sludge treatment, a membrane bioreactor, and a fixed-bed reactor. The results show a >90% removal of all estrogens in the activated sludge processes. (Due to the analytical quantification limit and low influent concentrations, however, this removal efficiency represents only an observable minimum.) The removal efficiencies of 77% and ≥90% for E1 and E2, respectively, in the fixed-bed reactor represent a good performance in view of the short hydraulic retention time of 35 min. The first-order removal-rate constant in batch experiments observed for E2 vari...
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