Characterization of performance of full-scale tertiary membranes under stressed operating conditions

2020 ◽  
Vol 81 (3) ◽  
pp. 571-584
Author(s):  
Sara Abu-Obaid ◽  
Pierre Bérubé ◽  
Wayne J. Parker

Abstract This study sought to identify factors responsible for enhanced fouling of ultrafiltration membranes used in tertiary wastewater treatment under challenging conditions of high flow and low temperature. A detailed analysis of full-scale membrane operating data was conducted, and this was supported by data gathered through a field sampling campaign. Higher average fouling rates and average recoveries were observed during periods of highest flows and lowest temperatures. The results demonstrated that the negative impact of seasonal changes on short-term fouling are readily reversible, while hydraulically irreversible fouling, which is responsible for intermediate and long-term fouling rates, is not effectively recovered by maintenance cleans (MCs) but is recovered by recovery cleans (RCs). An examination of membrane feedwater quality revealed that high fouling rates correlated to an increase in dissolved organic carbon (DOC) concentrations, with the biopolymer fraction of the DOC being most important. Increased capillary suction time (CST) values, which indicate reduced sludge dewaterability, were also observed during high fouling events. It was concluded that seasonal variations result in the increased release of extracellular polymeric substances (EPS) by microorganisms, which leads to higher membrane fouling and worsened dewaterability of the activated sludge.

2011 ◽  
Vol 63 (9) ◽  
pp. 1906-1912 ◽  
Author(s):  
Simos Malamis ◽  
Andreas Andreadakis ◽  
Daniel Mamais ◽  
Constantinos Noutsopoulos

The aim of this work was to evaluate the long-term performance of a Membrane Bioreactor (MBR) that operated continuously for 2.5 years and to assess membrane fouling and biomass activity under various operating conditions. Furthermore, a method for the characterisation of influent wastewater was developed based on its separation into various fractions. The MBR system operated at the solids retention times (SRT) of 10, 15, 20 and 33 days. The increase of SRT resulted in a decrease of the fouling rate associated with the reduction of extracellular polymeric substances. Moreover, the SRT increase resulted in a significant reduction of the Oxygen Uptake Rate (OUR) due to the lower availability of substrate and in a notable decrease of the maximum OUR since high SRT allowed the development of slower growing microorganisms. Biomass consisted of small flocs due to extensive deflocculation caused by intense aeration. Finally, the method developed for wastewater characterisation is straightforward and less time consuming than the usual method that is employed.


2019 ◽  
Vol 80 (6) ◽  
pp. 1011-1021 ◽  
Author(s):  
T. Miyoshi ◽  
T. P. Nguyen ◽  
T. Tsumuraya ◽  
K. Kimura ◽  
Y. Watanabe

Abstract We investigated the operating conditions of a baffled membrane bioreactor (B-MBR) under which long-term stable operation can be achieved through the continuous operation of a pilot-scale B-MBR. Under appropriate operating conditions, the B-MBR was capable of achieving excellent treated water quality in terms of biochemical oxygen demand and concentration of total nitrogen. Excellent removal of total phosphorus was also achieved. In addition, the degree of membrane fouling was acceptable, indicating that stable continuous operation of a B-MBR is possible under the operating conditions adopted in the present study. Estimation of the specific energy consumption in hypothetical full-scale B-MBRs operated under the conditions recommended by the findings was also performed in this study. The results suggest that energy consumption in full-scale B-MBRs would be in the range of 0.20–0.22 kWh/m3. These results strongly suggest that energy consumption in MBR operation can be significantly reduced by applying the concept of a B-MBR.


Author(s):  
Alejandro Ruiz-García ◽  
Noemi Melián-Martel ◽  
Ignacio Nuez

RO membrane fouling is one of the main challenges that membrane manufactures, the scientific community and industry professionals have to deal with. The consequences of this inevitable phenomenon have a negative effect on the performance of the desalination system. Predicting fouling in RO systems is key to evaluating the long-term operating conditions and costs. Much research has been done on fouling indices, methods, techniques and prediction models to estimate the influence of fouling on the performance of RO systems. This paper offers a critical review evaluating the state of industry knowledge in the development of fouling indices and models in membrane systems for desalination in terms of use and applicability. Despite major efforts in this field, there are gaps in terms of effective methods and models for the estimation of fouling in full-scale RO desalination plants. In existing models applied to full-scale RO desalination plants, neither the spacer geometry of membranes nor the efficiency and frequency of chemical cleanings - which play an important role in the performance of this process - are considered.


2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Laura Altweck ◽  
Stefanie Hahm ◽  
Holger Muehlan ◽  
Tobias Gfesser ◽  
Christine Ulke ◽  
...  

Abstract Background While a strong negative impact of unemployment on health has been established, the present research examined the lesser studied interplay of gender, social context and job loss on health trajectories. Methods Data from the German Socio-Economic Panel was used, which provided a representative sample of 6838 participants. Using latent growth modelling the effects of gender, social context (East vs. West Germans), unemployment (none, short-term or long-term), and their interactions were examined on health (single item measures of self-rated health and life satisfaction respectively). Results Social context in general significantly predicted the trajectories of self-rated health and life satisfaction. Most notably, data analysis revealed that West German women reported significantly lower baseline values of self-rated health following unemployment and did not recover to the levels of their East German counterparts. Only long-term, not short-term unemployment was related to lower baseline values of self-rated health, whereas, in relation to baseline values of life satisfaction, both types of unemployment had a similar negative effect. Conclusions In an economic crisis, individuals who already carry a higher burden, and not only those most directly affected economically, may show the greatest health effects.


Author(s):  
سعدالله ألنعيمي

The study aims to analyzing the reciprocal relationship between the nominal exchange rate of the Turkish lira versus the U.S. dollar and the stock prices of the companies listed on the Istanbul Stock Exchange (ISE) expressed in the general market index for the period from 2005 to 2020 with 192 monthly observations, based on the traditional theory and the theory of portfolio balance model in theoretical interpretation for that relationship, aiming to identify the effect of the exchange rate on stock prices, as well as to analyze the causal relationship between those variables and to identify which of them is the cause or which is the result, using the Autoregressive Distributed Lag (ARDL) model. The research found that the exchange rate has a positive effect on stock prices in the long term, despite the emergence of the negative impact in the short term, but the long-term relationship has corrected the course of the short-term relationship with a time period not exceeding one month, in addition to proving that this relationship takes one direction. From the exchange rate towards stock prices, that is, the exchange rate is the reason and stock prices are the result, therefore the results of this research helps investors to predict future trends of stock prices depending on the exchange rate changes, and it also enables the companies, especially those with foreign transactions, to manage price risks the exchange rate in order to avoid its negative impact on its share price, as it represents an obstacle to achieving its main goal of maximizing the share price


2016 ◽  
Vol 2016 ◽  
pp. 1-11 ◽  
Author(s):  
Octavian Pastravanu ◽  
Mihaela-Hanako Matcovschi

The main purpose of this work is to show that the Perron-Frobenius eigenstructure of a positive linear system is involved not only in the characterization of long-term behavior (for which well-known results are available) but also in the characterization of short-term or transient behavior. We address the analysis of the short-term behavior by the help of the “(M,β)-stability” concept introduced in literature for general classes of dynamics. Our paper exploits this concept relative to Hölder vectorp-norms,1≤p≤∞, adequately weighted by scaling operators, focusing on positive linear systems. Given an asymptotically stable positive linear system, for each1≤p≤∞, we prove the existence of a scaling operator (built from the right and left Perron-Frobenius eigenvectors, with concrete expressions depending onp) that ensures the best possible values for the parametersMandβ, corresponding to an “ideal” short-term (transient) behavior. We provide results that cover both discrete- and continuous-time dynamics. Our analysis also captures the differences between the cases where the system dynamics is defined by matrices irreducible and reducible, respectively. The theoretical developments are applied to the practical study of the short-term behavior for two positive linear systems already discussed in literature by other authors.


2020 ◽  
Vol 3 (1) ◽  
Author(s):  
Grace Amin

Bullying is deliberate aggressive action, using an imbalance of strength physically or mentally by hurting physical, verbal, or emotional / psychological forms repeatedly. In the last decade, cases of bullying in Indonesia continue to increase and if not handled properly will increasingly have a negative impact on the development of the children of the nation's next generation. Bullying does not only affect children who are bullied but can also affect children who bully, children who witness bullying. Some of the effects of bullying include anxiety, depression, and low self-esteem. The purpose of community engagement is to socialize the impact of bullying and how to increase self-esteem to adolescents. Through psychoeducation programs in adolescents such as schools and teenagers religious communities in the Cikarang - Bekasi region, young people gain an in-depth understanding of bullying, its effects and how to increase their confidence. Through this psychoeducation, teenagers understand the understanding, types and effects of bullying both short term and long term so they promise to resist bullying starting from themselves. Teenagers learn that humans are social beings who need each other. They learn about the meaning of diversity and bhineka tunggal ika and try to implement it in their next lives by respecting the differences in their environment. These teenagers learn to respect themselves more, see the positive things that God has given them. They try to always believe in themselves that they are perfect and valuable beings in God's eyes so that even though the environment around them may not appreciate, they can still see positive things in themselvesABSTRAK:Bullying adalah tindakan agresif yang disengaja, menggunakan ketidakseimbangan kekuatan secara fisik atau mental dengan cara menyakiti bentuk fisik, verbal, atau emosional/ psikologis secara berulang – ulang. Dalam satu decade terakhir, kasus bullying di Indonesia terus meningkat dan bila tidak ditangani dengan baik akan semakin berdampak negative bagi perkembangan anak – anak generasi penerus bangsa. Tindakan bullying tidak hanya berdampak pada anak yang di-bully tetapi juga dapat berdampak pada anak yang mem-bully, anak yang menyaksikan bullying. Beberapa dampak bullying diantaranya kecemasan, depresi, serta rendahnya harga diri (self-esteem). Tujuan dari pengabdian kepada masyarakat ini adalah untuk mensosialisasikan dampak bullying serta cara meningkatkan self-esteem kepada para remaja. Melalui program psikoedukasi di lingkungan remaja seperti sekolah maupun komunitas keagamaan remaja wilayah Cikarang – Bekasi, para remaja mendapatkan pemahaman mendalam mengenai bullying, dampaknya serta bagaimana cara meningkatkan kepercayaan diri mereka. Melalui psikoedukasi ini, para remaja memahami pengertian, jenis serta dampak bullying baik jangka pendek maupun jangka panjang sehingga mereka berjanji untuk bersikap menolak bullying mulai dari diri mereka sendiri. Para remaja belajar bahwa manusia adalah mahluk social yang saling membutuhkan. Mereka belajar tentang makna keberagaman dan Bhineka Tunggal Ika serta berusaha mengimplementasikannya dalam kehidupan mereka selanjutnya dengan cara menghargai perbedaan yang ada di lingkungannya. Remaja ini belajar untuk lebih menghargai diri mereka, melihat hal positif yang telah diberikan Tuhan kepada mereka. Mereka mencoba untuk selalu menanamkan dalam diri bahwa mereka adalah mahluk yang sempurna dan berharga di mata Tuhan sehingga walaupun lingkungan di sekitar mereka mungkin tidak menghargai, mereka tetap dapat melihat hal positif dalam diri mereka.


2020 ◽  
Author(s):  
Christian Rück ◽  
David Mataix-Cols ◽  
Kinda Malki ◽  
Mats Adler ◽  
Oskar Flygare ◽  
...  

ABSTRACTBackgroundVarious surveys have documented a negative impact of the COVID-19 pandemic on the population’s mental health. There is widespread concern about a surge of suicides, but evidence supporting a link between global pandemics and suicide is very limited. Using historical data from the three major influenza pandemics of the 20th century, and recently released data from the first half of 2020, we aimed to investigate whether an association exists between influenza deaths and suicide deaths.MethodsAnnual data on influenza death rates and suicide rates were extracted from the Statistical Yearbook of Sweden from 1910-1978, covering the three 20th century pandemics, and from Statistics Sweden for the period from January to June of each year during 2000-2020. COVID-19 death data were available for the first half of 2020. We implemented non-linear autoregressive distributed lag (NARDL) models to explore if there is a short-term and/or long-term effect of increases and decreases in influenza death rates on suicide rates during 1910-1978. Analyses were done separately for men and women. Descriptive analyses were used for the available 2020 data.FindingsBetween 1910-1978, there was no evidence of either short-term or long-term significant associations between influenza death rates and changes in suicides. The same pattern emerged in separate analyses for men and women. Suicide rates in January-June 2020 revealed a slight decrease compared to the corresponding rates in January-June 2019 (relative decrease by −1.2% among men and −12.8% among women).InterpretationWe found no evidence of short or long-term association between influenza death rates and suicide death rates across three 20th century pandemics or during the first six months of 2020 (when the first wave of COVID-19 occurred). Concerns about a substantial increase of suicides may be exaggerated. The media should be cautious when reporting news about suicides during the current pandemic.


Author(s):  
Roberto Llorente ◽  
Marta Beltran ◽  
Joaquin Perez ◽  
Noboru Uehara ◽  
Md. Khan ◽  
...  

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