Wyniki wyszukiwania - BazTech

1

PAC adsorption efficiencies in the filter and in the homogeneous flocculator. A full-scale comparative study

Bielski Andrzej

Environment Protection Engineering

|

2022

|

Vol. 48, nr 1

83--97

EN

The paper investigates the efficiency of adsorption of organic pollutants present in natural water on powdered activated carbon (PAC). A PAC adsorption capacity is related to the mass exchange driving force between water and sorbent. During the study, it was confirmed that the mass transfer driving force in the homogeneous flocculator with simultaneous PAC adsorption was lower than in the filter column. The filter showed a better utilization of PAC adsorption capacity than the volume system, for the optimal PAC dose. The authors proposed a new method where adsorption was carried out in the filter column with PAC applied to its upper layer. The powdered sorbent was applied to the bed at the end of a backwashing cycle. Two models of PAC adsorption in transient states for the homogeneous flocculator and the column mass exchanger were presented. The simulation calculations confirmed that there was still a possibility to double the PAC adsorption capacity concerning commonly used adsorption with coagulation in the homogeneous flocculator.

2

An improved cardiac arrhythmia classification using an RR interval-based approach

Rahul Jagdeep, Sora Marpe, Sharma Lakhan Dev, Bohat Vijay Kumar

Biocybernetics and Biomedical Engineering

|

2021

|

Vol. 41, no. 2

656--666

EN

Accurate and early detection of cardiac arrhythmia present in an electrocardiogram (ECG) can prevent many premature deaths. Cardiac arrhythmia arises due to the improper conduction of electrical impulses throughout the heart. In this paper, we propose an improved RR interval-based cardiac arrhythmia classification approach. The Discrete Wavelet Transform (DWT) and median filters were used to remove high-frequency noise and baseline wander from the raw ECG. Next, the processed ECG was segmented after the determination of the QRS region. We extracted the primary feature RR interval and other statistical features from the beats to classify the Normal, Premature Ventricular Contraction (PVC), and Premature Atrial Contraction (PAC). The K-Nearest Neighbour (k-NN), Support Vector Machine (SVM), Decision Tree (DT), Naı¨ve Bayes (NB), and Random Forest (RF) classifier were utilised for classification. Overall performance of SVM with Gaussian kernel achieved Se % = 99.28, Sp % = 99.63, +P % = 99.28, and Acc % = 99.51, which is better than the other classifiers used in this method. The obtained results of the proposed method are significantly better and more accurate.

3

Filter beds supplemented with powdered activated carbon

Bielski A., Zymon W.

Environment Protection Engineering

|

2017

|

Vol. 43, nr 2

173--191

EN

Various factors influencing adsorption on powdered activated carbon (PAC) used for the removal of organic compounds from water and wastewater have been investigated. Incomplete utilization of adsorption capacity of PAC observed in current technological applications is caused by too short con-tact times of aqueous solutions with carbon particles and the system configuration (adsorption in volume systems with simultaneous coagulation). A new method has been proposed involving application of PAC into the upper layer of a two-layer filter or a middle layer of a three-layer filter during bed fluidization. The extended contact time between aqueous solutions and PAC increases the amount of adsorbate adsorbed on the surface of activated carbon. A comparative studies conducted on adsorption in both volume and column systems confirmed better utilization of adsorption capacity for PAC applied on a filter bed. Two models of PAC adsorption in transient conditions were developed for volume and column systems. Computer simulations confirmed that the adsorption capacity of PAC may be in-creased by several times in column systems with respect to the commonly used adsorption with coagulation in volume systems.

4

Fouling membran półprzepuszczalnych podczas oczyszczania wody metodą ultra- i mikrofiltracji - przegląd piśmiennictwa

Bodzek M., Płatkowska A.

Inżynieria i Ochrona Środowiska

|

2009

|

T. 12, nr 1

5-24

PL

Procesom membranowym uzdatniania wody i oczyszczania ścieków towarzyszy nieodłącznie zjawisko zmniejszania wydajności i żywotności membran zwane foulingiem. Pierwszym krokiem do ograniczenia foulingu jest poznanie natury tego zjawiska. Pozwalają na to dostępne techniki analityczne, takie jak: SEM, AFM, FTIR, HPSEC, analiza OWO, ASA, pomiar kąta zwilżenia oraz potencjału elektrokinetycznego membran czy też frakcjonowanie na żywicach XAD8/4. Stopień foulingu powodowanego przez NOM uzależniony jest m.in. od siły jonowej oraz pH. Zależy on w dużej mierze od właściwości filtrowanej wody, w tym hydrofilowości/hydrofobowości jej składników. Duża część badaczy obarcza frakcję hydrofobową odpowiedzialnością za fouling. Dla procesów niskociśnieniowych zaobserwowano wpływ rozmiaru cząstek filtrowanej frakcji (im mniejsze, tym większy obserwowany spadek strumienia oraz opór filtracji) na zjawisko foulingu. Zidentyfikowano 4 kategorie NOM, które uważane są za silne foulanty, a mianowicie białka, aminocukry, polisacharydy i związki poli(hydroksy-aromatyczne). Znaczenia ma również rodzaj membrany. W zdecydowanej większości prac zaobserwowano większą tendencję do foulingu w przypadku membran hydrofobowych niż hydrofilowych, co tłumaczono adsorpcją ujemnie naładowanych grup funkcyjnych NOM na dodatnio naładowanych powierzchniach membrany. Obecnie stosowane są różne procesy wstępnego przygotowania nadawy, mające na celu zwiększenie jakości wody i/lub wydajności membran. Koagulacja oraz adsorpcja na węglu aktywnym są polecane przy minimalizacji foulingu związanego z dużymi stężeniami poli(hydroksy-aromatów), proces utlenienia natomiast jest zalecany do zmniejszania foulingu powodowanego polisacharydami.

EN

During membrane water and wastewater processes reduction of capacity and membranes lifetime can be observed. Those phenomena are caused by membrane fouling. To limit the influence of fouling on the efficiency of membrane processes detailed recognition of its nature is required. This can be done using available analytical technologies like: electron microscopy (SEM, AFM), infrared spectroscopy (FTIR), high performance size exclusion chromatography (HPSEC), TOC analysis, atomic absorption spectroscopy (AAS), measurement of contact angle and zeta potential or fractionation on XAD8/4 resins. The influence of fouling caused by NOM mainly depends on ionic strength and pH, but also on properties of filtrated water, including hydophobicity/hydrophilicity of its components. Resent scientific reports suggest that the hydrophobic water fraction has a significant impact on fouling. Size of molecules of filtrated fraction is responsible for fouling occurring fouling during low-pressure membrane processes (the smallest size of molecules the highest flux decline). 4 categories of NOM, which are considered to be strong foulants, were identified. They include: proteins, aminosugars, polysaccharides and poly(hydroxy-aromatics). The membrane composing material also has a meaning. Hydrophobic membranes seem to have greater ability to fouling than hydrophilic ones. It can be explained by the fact, that the positively charged membrane surface tends to adsorb negatively charged functional groups of NOM. Nowadays different water pretreatment processes are applied. Their aim is to improve water quality and/or membrane capacity. Fouling caused by poly(hydroxyl-amines) can be minimized by coagulation or adsorption on activated carbon, while oxidation reduces the fouling induced by polysacharides.

5

Sorption of phenol onto activated carbon

Tomaszewska M., Mozia S., Kaleńczuk R. J.

Polish Journal of Chemical Technology

|

2001

|

Vol. 3, nr 2

28-30

EN

Investigations of the adsorptivity of selected activated carbons towards aqueous solutions of phenol have been undertaken. The times necessary to achieve adsorption equilibrium and the course of adsorption isotherms were determined. The isotherms may be described by Freundlich and Langmuir equations. On the basis of adsorption isotherms the best carbon for removal of phenol was selected. Carbon structure characterisation including BET surface area, pore size distribution and pore volumes and its influence on applied adsorbate were also investigated. All carbons were microporous and consist mostly of micropores with a pore size range of 0.9 - 1.2 nm. BET surface areas of applied carbons range from 680 - 1323 m exp.2/g.