Search results for "RETENTION"
showing 10 items of 347 documents
Improved growth performance in rainbow trout Oncorhynchus mykiss reared at high densities is linked to increased energy retention
2015
Abstract Behaviour has been suggested as an underlying factor influencing how rearing density affects growth performance in Salmonid fishes. At low densities there is an elevated intensity of aggressive interactions and the formation of dominance hierarchies. As density increases, it is commonly assumed that aggression decreases, as the cost and effort required to establish and maintain dominance hierarchies increase. The increased energy expenditure associated with aggressive interactions has been identified as one mechanism causing a reduced efficiency in feed utilisation and therefore decreased growth performance. Manipulating aggressive behaviour through density may have advantages from…
An implant-supported overdenture design with a horizontal path of insertion
2013
The rehabilitation of the atrophic maxilla by means of implant-supported prostheses cannot always be achieved with fixed prostheses because of anatomic, esthetic, or economic issues, so for some patients the treatment of choice is a removable prosthesis. This article analyzes a new design for implant-supported overdentures with horizontal or faciolingual insertion. Its retention system is based on frictional forces or stepped interlocking horizontal surfaces and is appropriate for patients with skeletal Class II or III relationships with severe maxillary atrophies. The design facilitates implant-prosthetic hygiene and improved esthetics in patients with nonparallel implants by hiding abutme…
Engaging learners through virtual worlds
2010
Abstract The aim of this paper is to explore how virtual worlds could support the engagement for learning. This paper reviews the results of studies that utilized virtual worlds to engage learners. The results are examined in two levels, namely learning gains and design principles. It has been found out that deeper learner engagement results in higher learning gains. In some studies better content retention is also noted. Many studies also suggest design principles for using virtual worlds for facilitating engaged learning. This paper builds a framework for the design and use of virtual worlds in education for better learner engagement.
Residence time distribution of solid particles in a continuous, high-aspect-ratio multiple-impeller stirred vessel
2004
Abstract In this paper experimental information on the retention time distribution (RTD) of solid particles in a high-aspect-ratio vessel, stirred by three equally spaced Rushton turbines, is presented. The relevant data were obtained by a special technique named twin system approach (TSA) that greatly simplifies the handling of particle-laden streams and is therefore particularly suited for investigating particle RTD in flow systems. The technique fundamentals are first summarized, together with the data analysis procedure. This lastly requires a numerical deconvolution operation that is easily performed with the help of Z -transforms. Two different approaches for excluding the spurious co…
Mass loading, distribution, and removal of antibiotics and antiretroviral drugs in selected wastewater treatment plants in Kenya.
2020
The discharge of active pharmaceutical ingredients (APIs) into the aquatic environment from wastewater effluents is a concern in many countries. Although many studies have been conducted to evaluate the APIs removal efficiencies and emissions to the environment in wastewater treatment plants (WWTPs), most of these studies considered the aqueous and sludge phases, disregarding the suspended particulate matter (SPM) phase. To try to understand the role of the SPM, the occurrence of five most common antibiotics and three antiretroviral drugs (ARVDs) commonly used in Kenya were investigated in this study. APIs partitioning and mass loading in influents and effluents of three different WWTPs: tr…
Influence of volatile solids and pH for the production of volatile fatty acids: batch fermentation tests using sewage sludge
2021
The aim of this work was to study the effect of volatile suspended solid (VSS) and pH on volatile fatty acids (VFA) production from waste activated sludge (WAS) fermentation by means of batch tests. The final goal was to gain insights to enhance VFA stream quality, with the novelty of using WAS with high sludge retention time. Results revealed that the optimum conditions to maximize VFAs and minimize nutrients and non-VFA sCOD are a VSS concentration of 5.9 g/L and initial pH adjustment to pH 10. The WAS bacterial community structures were analysed according to Next Generation Sequencing (NGS) of 16S rDNA amplicons. The results revealed changes of bacterial phyla abundance in comparison wit…
Nitrous oxide from integrated fixed-film activated sludge membrane bioreactor: Assessing the influence of operational variables
2017
The influence of the main operational variables on N2O emissions from an Integrated Fixed Film Activated Sludge University of Cape Town membrane Bioreactor pilot plant was studied. Nine operational cycles (total duration: 340 days) were investigated by varying the value of the mixed liquor sludge retention time (SRT) (Cycles 1â3), the feeding ratio between carbon and nitrogen (C/N) (Cycles 4â6) and simultaneously the hydraulic retention time (HRT) and the SRT (Cycles 7â9). Results show a huge variability of the N2O concentration in liquid and off-gas samples (ranged from 10â1μg N2O-N Lâ1to 103μg N2O-N Lâ1). The maximum N2O concentration (1228 μg N2O-N Lâ1) in the off-gas sa…
Greenhouse gas emissions from membrane bioreactors: analysis of a two-year survey on different MBR configurations
2018
Abstract This study aimed at evaluating the nitrous oxide (N2O) emissions from membrane bioreactors (MBRs) for wastewater treatment. The study investigated the N2O emissions considering multiple influential factors over a two-year period: (i) different MBR based process configurations; (ii) wastewater composition (municipal or industrial); (iii) operational conditions (i.e. sludge retention time, carbon-to-nitrogen ratio, C/N, hydraulic retention time); (iv) membrane modules. Among the overall analysed configurations, the highest N2O emission occurred from the aerated reactors. The treatment of industrial wastewater, contaminated with salt and hydrocarbons, provided the highest N2O emission…
Treatment of a submerged anaerobic membrane bioreactor (SAnMBR) effluent by an activated sludge system: the role of sulphide and thiosulphate in the …
2014
This work studies the use of a well-known and spread activated sludge system (UCT configuration) to treat the effluent of a submerged anaerobic membrane bioreactor (SAnMBR) treating domestic waste-water. Ammonia, phosphate, dissolved methane and sulphide concentrations in the SAnMBR effluent were around 55 mg NH4-N L-1, 7 mg PO4-P L-1, 30 mg non-methane biodegradable COD L-1, and 105 mg S2- L-1 respectively. The results showed a nitrification inhibition caused by the presence of sulphur compounds at any of the solids retention time (SRT) studied (15,20 and 25 days). This inhibition could be overcome increasing the hydraulic retention time (HRT) from 13 to 26 h. Among the sulphur compounds, …
Maximising resource recovery from wastewater grown microalgae and primary sludge in an anaerobic membrane co-digestion pilot plant coupled to a compo…
2021
[EN] A pilot-scale microalgae (Chlorella spp.) and primary sludge anaerobic co-digestion (ACoD) plant was run for one year in an anaerobic membrane bioreactor (AnMBR) at 35 °C, 70 d solids retention time and 30 d hydraulic retention time, showing high stability in terms of pH and VFA concentration. The plant achieved a high degree of microalgae and primary sludge substrate degradation, resulting in a methane yield of 370 mLCH4·gVSinf¿1. Nutrient-rich effluent streams (685 mgN·L¿1 and 145 mgP·L¿1 in digestate and 395 mgNH4-N·L¿1 and 37 mgPO4-P·L¿1 in permeate) were obtained, allowing posterior nutrient recovery. Ammonium was recovered from the permeate as ammonia sulphate through a hydrophob…