Control of disinfection and halogenated disinfection byproducts by the electrochemical process

2007 ◽  
Vol 55 (12) ◽  
pp. 213-219 ◽  
Author(s):  
Y.J. Jung ◽  
B.S. Oh ◽  
J.W. Kang ◽  
M.A. Page ◽  
M.J. Phillips ◽  
...  
Keyword(s):  
Kinetic Studies ◽  
Disinfection Byproducts ◽  
Electrochemical Process ◽  
Free Chlorine ◽  
Haloacetic Acids ◽  
Oh Radicals ◽  
Inactivation Kinetic ◽  
E Coli ◽  
Electrochemical Processes

The aim of this study was to investigate some aspects of the performance of electrochemical process as an alternative disinfection strategy, while minimising DBPs, for water purification. The study of electrochemical processes has shown free chlorine to be produced, but smaller amounts of stronger oxidants, such as ozone, hydrogen peroxide and OH radicals (•OH), were also generated. The formation of mixed oxidants increased with increasing electric conductivity, but was limited at conductivities greater than 0.6 mS/cm. Using several microorganisms, such as E. coli and MS2 bacteriophage, inactivation kinetic studies were performed. With the exception of free chlorine, the role of mixed oxidants, especially OH radicals, was investigated for enhancement of the inactivation rate. Additionally, the formation and reduction of DBPs was studied by monitoring the concentration of haloacetic acids (HAAs) during the process.

scholarly journals Polyaspartamide Functionalized Catechol-Based Hydrogels Embedded with Silver Nanoparticles for Antimicrobial Properties

Polymers ◽  
2018 ◽  
Vol 10 (11) ◽  
pp. 1188 ◽  
Author(s):  
Milène Tan ◽  
Youngjin Choi ◽  
Jaeyun Kim ◽  
Ji-Heung Kim ◽  
Katharina Fromm
Keyword(s):  
Antimicrobial Properties ◽  
Kinetic Studies ◽  
Bactericidal Effect ◽  
Release Kinetic ◽  
E Coli ◽  
Dispersed Particles ◽  
Time Period ◽  
Long Time ◽  
20 Nm

In this study, polyaspartamide-based hydrogels were synthesized by boron-catechol coordination followed by incorporation of AgNPs into the materials. Free catechol moieties were exploited to produce AgNPs. TEM analyses displayed AgNPs of less than 20 nm in diameter and with minimum aggregation, attesting the role of hydrogels to act as an efficient template for the production of dispersed particles. XRD analyses confirmed the mean particle size using the Scherrer equation. Release kinetic studies were performed in DMEM medium, showing a slow release over a long time-period. Finally, the MIC and MBC were determined, demonstrating a bacteriostatic and bactericidal effect against Gram-positive S. aureus and Gram-negative E. coli.

scholarly journals Metals releases and disinfection byproduct formation in domestic wells following shock chlorination

2010 ◽  
Vol 3 (1) ◽  
pp. 177-198
Author(s):  
M. Walker ◽  
J. Newman
Keyword(s):  
Trace Metals ◽  
Contact Time ◽  
Disinfection Byproducts ◽  
Oxidation Potential ◽  
Free Chlorine ◽  
Haloacetic Acids ◽  
Background Concentrations ◽  
Disinfection Byproduct ◽  
Byproduct Formation ◽  
By Products

Abstract. Shock chlorination is used for rapid disinfection to control pathogens and nuisance bacteria in domestic wells. A typical shock chlorination procedure involves adding sodium hypochlorite in liquid bleach solutions to achieve concentrations of free chlorine of up to 200 ppm in the standing water of a well. The change in pH and oxidation potential may bring trace metals from aquifer materials into solution and chlorine may react with dissolved organic carbon to form disinfection byproducts. We carried out experiments with four wells to observe and determine the persistence of increased concentrations of metals and disinfection byproducts. Water samples from shock chlorinated wells were analyzed for Pb, Cu, As, radionuclides and disinfection byproducts (haloacetic acids and trihalomethanes), immediately prior to treatment, after sufficient contact time with chlorine had elapsed, and at intervals determined by the number of casing volumes purged, for up to four times the well casing volume. Elevated concentrations of lead and copper dissipated in proportion to free chlorine (measured semi-quantitatively) during the purging process. Trihalomethanes and haloacetic acids were formed in wells during disinfection. In one of two wells tested, disinfection byproducts dissipated in proportion to free chlorine during purging. However, one well retained disinfection byproducts and free chlorine after four well volumes had been purged. Although metals returned to background concentrations in this well, disinfection byproducts remained elevated, though below the MCL, likely because purging volume was insufficient. Simple chlorine test strips may be a useful method for indicating when purging is adequate to remove metals and disinfection by-products mobilized and formed by shock chlorination.

scholarly journals Metals releases and disinfection byproduct formation in domestic wells following shock chlorination

2011 ◽  
Vol 4 (1) ◽  
pp. 1-8 ◽  
Author(s):  
M. Walker ◽  
J. Newman
Keyword(s):  
Trace Metals ◽  
Treatment Time ◽  
Disinfection Byproducts ◽  
Oxidation Potential ◽  
Free Chlorine ◽  
Haloacetic Acids ◽  
Background Concentrations ◽  
Disinfection Byproduct ◽  
Byproduct Formation ◽  
By Products

Abstract. Shock chlorination is used for rapid disinfection to control pathogens and nuisance bacteria in domestic wells. A typical shock chlorination procedure involves adding sodium hypochlorite in liquid bleach solutions to achieve concentrations of free chlorine of up to 200 mg L−1 in the standing water of a well. The change in pH and oxidation potential may bring trace metals from aquifer materials into solution and chlorine may react with dissolved organic carbon to form disinfection byproducts. We carried out experiments with four wells to observe and determine the persistence of increased concentrations of metals and disinfection byproducts. Water samples from shock chlorinated wells were analyzed for Pb, Cu, As, radionuclides and disinfection byproducts (haloacetic acids and trihalomethanes), immediately prior to treatment, after sufficient treatment time with chlorine had elapsed, and at intervals determined by the number of casing volumes purged, for up to four times the well casing volume. Elevated concentrations of lead and copper dissipated in proportion to free chlorine (measured semi-quantitatively) during the purging process. Trihalomethanes and haloacetic acids were formed in wells during disinfection. In one of two wells tested, disinfection byproducts dissipated in proportion to free chlorine during purging. However, one well retained disinfection byproducts and free chlorine after 4 WV had been purged. Although metals returned to background concentrations in this well, disinfection byproducts remained elevated, though below the MCL. This may have been due to well construction characteristics and interactions with aquifer materials. Simple chlorine test strips may be a useful method for indicating when purging is adequate to remove metals and disinfection by-products mobilized and formed by shock chlorination.

Correlations between surrogate nitrogenous organic precursors and C-, N-DBP formation

2011 ◽  
Vol 64 (12) ◽  
pp. 2395-2403 ◽  
Author(s):  
H. H. Chang ◽  
G. S. Wang
Keyword(s):  
Organic Compounds ◽  
Chlorine Dioxide ◽  
Benzalkonium Chloride ◽  
Product Formation ◽  
Disinfection Byproducts ◽  
Free Chlorine ◽  
Haloacetic Acids ◽  
Source Water ◽  
Organic Precursors ◽  
Different Characteristics

Nitrosamines have been emerging as disinfection byproducts in drinking water using source water impacted with domestic wastewaters. Nitrogenous organic compounds are suggested as precursors of nitrosamines, but many of them have not been identified. This study investigated the correlations between nine selected nitrogenous organic compounds with different characteristics and corresponding disinfection by-product formation potentials (nitrosamines, trihalomethanes (THMs), and haloacetic acids (HAAs)) from their reactions with free chlorine, chlorine dioxide and monochloramine. Besides dimethylamine, the well-known precursor of nitrosamines, 3-(N,N-dimethyloctylammonio)propanesulfonate (3-N,N-DAPSIS) inner salt and benzyldimethyltetradecylamine (benzalkonium chloride, BKC) were suggested as important nitrosamine precursors. 3-N,N-DAPSIS could form about 1,000 ng/L of N-nitrosodimethylamine (NDMA) and more than 1,000 μg/L of THMs. More than 150,000 ng/L of NDMA were observed when BKC was treated with monochloramine, and high levels of THMs (up to 2,700 μg/L) were also yielded. As expected, free chlorine produced higher levels of THMs and HAAs, and chlorine dioxide generated minor levels of traditional DBPs. Nitrosamines were mainly formed when the precursors were treated with monochloramine.

scholarly journals The roles of bromide and precursor structures on DBP formation and species distribution

2006 ◽  
Vol 6 (4) ◽  
pp. 27-33 ◽  
Author(s):  
G.S. Wang ◽  
P.L. Huang
Keyword(s):  
Organic Matter ◽  
Organic Acids ◽  
Natural Organic Matter ◽  
Species Distribution ◽  
Ph Effect ◽  
Free Chlorine ◽  
Haloacetic Acids ◽  
Formation Potential ◽  
Trihalomethane Formation Potential

This study investigates the role of bromide and the structure of precursors in DBPs formation. Resorcinol (1,3-dihydroxylbenzene) and 2,4-pentadiol were used to represent the aromatic and aliphatic precursors. Laboratory prepared hydrophilic organic acids was used to simulate the mixtures of the aqueous natural organic matter. The results showed that about 60% of the bromide was transformed into HOBr and OBr− by chlorine when the chlorine dosages was high (5–20 mg/L of free chlorine). However, only 20% of bromide was transformed into HOBr and OBr− at low chlorine dosage (1 mg/L). Trihalomethane formation potential (THMFP) measurements showed that higher THMs formation was obtained at higher pH for 2,4-pentadiol, mainly due to the presence of the bromo-THMs. For resorcinol, however, no bromo-THMs are formed at either pH 7 or 9. For THMFP from hydrophilic organic acids, no apparent pH effect was observed. It is concluded that the higher THM formation at higher pH was mainly due to the formation of bromo-THMs from the aliphatic precursors. Similar trends are obtained in THMFP measurements for haloacetic acids formation potential (HAAFP).

scholarly journals Membrane and Electrochemical Processes for Water Desalination: A Short Perspective and the Role of Nanotechnology

Membranes ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 280
Author(s):  
Moon Son ◽  
Kyung Hwa Cho ◽  
Kwanho Jeong ◽  
Jongkwan Park
Keyword(s):  
Energy Consumption ◽  
Operating Cost ◽  
Water Flux ◽  
High Water ◽  
High Energy ◽  
Electrochemical Process ◽  
Water Desalination ◽  
The Past ◽  
Electrochemical Processes

In the past few decades, membrane-based processes have become mainstream in water desalination because of their relatively high water flux, salt rejection, and reasonable operating cost over thermal-based desalination processes. The energy consumption of the membrane process has been continuously lowered (from >10 kWh m−3 to ~3 kWh m−3) over the past decades but remains higher than the theoretical minimum value (~0.8 kWh m−3) for seawater desalination. Thus, the high energy consumption of membrane processes has led to the development of alternative processes, such as the electrochemical, that use relatively less energy. Decades of research have revealed that the low energy consumption of the electrochemical process is closely coupled with a relatively low extent of desalination. Recent studies indicate that electrochemical process must overcome efficiency rather than energy consumption hurdles. This short perspective aims to provide platforms to compare the energy efficiency of the representative membrane and electrochemical processes based on the working principle of each process. Future water desalination methods and the potential role of nanotechnology as an efficient tool to overcome current limitations are also discussed.

scholarly journals Insights into Enzymic Catalysis from Studies on Dihydrofolate Reductases

Pteridines ◽  
1989 ◽  
Vol 1 (1) ◽  
pp. 37-43 ◽  
Author(s):  
Stephen J. Benkovic ◽  
Joseph A. Adams ◽  
Carol A. Fierke ◽  
Adel M. Naylor
Keyword(s):  
Catalytic Efficiency ◽  
Kinetic Studies ◽  
Structural Similarity ◽  
E Coli ◽  
Energy Profiles ◽  
Dihydrofolate Reductases ◽  
Cellular Dna ◽  
High Degree ◽  
Conserved Amino Acids

Summary The role of DHFR in the maintenance of cellular DNA has sparked wide interest in the structure and dynamics of this enzyme. Kinetic studies of specific amino acid replacements on the enzyme isolated from E. coli has proved useful in the detailing of hydrophobic and ionic interactions both proximal and distal to the site of chemical transformation (e. g. Phe-31, Leu-54 and Arg-44). Despite the low sequence homology shared by the E. coli and L. easei enzymes, the free energy profiles are surprisingly comparable. This probably is the result of the high degree of structural similarity of the active site surfaces, but the deleterious effects of subtle replacements (e. g. Leu-54-Ile) at strictly conserved amino acids underscore the latters unique role in attaining the required catalytic efficiency for the enzyme.

Scanning tunneling microscopy of E. coli RNA polymerase deposited onto an Au substrate by an electrochemical process

1991 ◽  
Vol 49 ◽  
pp. 378-379
Author(s):  
Rebecca W. Keller ◽  
Carlos Bustamante ◽  
David Bear
Keyword(s):  
Scanning Tunneling Microscope ◽  
Biological Sample ◽  
Substrate Surface ◽  
Electrochemical Process ◽  
Atomic Resolution ◽  
Scanning Tunneling ◽  
Tunneling Microscopy ◽  
Tunneling Microscope ◽  
E Coli ◽  
Preparation Techniques

Under ideal conditions, the Scanning Tunneling Microscope (STM) can create atomic resolution images of different kinds of samples. The STM can also be operated in a variety of non-vacuum environments. Because of its potentially high resolution and flexibility of operation, it is now being applied to image biological systems. Several groups have communicated the imaging of double and single stranded DNA.However, reproducibility is still the main problem with most STM results on biological samples. One source of irreproducibility is unreliable sample preparation techniques. Traditional deposition methods used in electron microscopy, such as glow discharge and spreading techniques, do not appear to work with STM. It seems that these techniques do not fix the biological sample strongly enough to the substrate surface. There is now evidence that there are strong forces between the STM tip and the sample and, unless the sample is strongly bound to the surface, it can be swept aside by the tip.

The Local Sanarelli-Shwartzman Phenomenon in Rats Induced by Human Leukaemic Cells

1973 ◽  
Vol 29 (02) ◽  
pp. 353-362
Author(s):  
J Lisiewicz ◽  
A Pituch ◽  
J. A Litwin
Keyword(s):  
Chronic Lymphocytic Leukaemia ◽  
Intravenous Injection ◽  
Peripheral Blood ◽  
Lymphocytic Leukaemia ◽  
Acute Myeloblastic Leukaemia ◽  
Demarcation Line ◽  
E Coli ◽  
Leukaemic Cells ◽  
Shwartzman Phenomenon

SummaryThe local Sanarelli-Shwartzman phenomenon (SSP-L) in the skin of 30 rats was induced by an intr a cutaneous sensitizing injection of leukaemic leucocytes isolated from the peripheral blood of patients with chronic lymphocytic leukaemia (CLL), acute myeloblastic leukaemia (AL) and chronic granulocytic leukaemia (CGL) and challenged by an intravenous injection of 100(μ of E. coli endotoxin. SSP-L was observed in 7 rats after injection of CLL lymphocytes and in 6 and 2 rats after AL myeloblasts and the CGL granulocytes, respectively. The lesions in the skin after AL myeloblasts appeared in a shorter time and were of longer duration compared with those observed after CLL lymphocytes and CGL granulocytes. Histologically, the lesions consisted of areas of destruction in the superficial layers of the skin ; the demarcation line showed the presence of neutrophils, macrophages and erythrocytes. Haemorrhages and fibrin deposits near the demarcation line were larger after injection of CLL lymphocytes and AL myeloblasts than after CGL granulocytes. The possible role of leucocyte procoagulative substances in the differences observed have been discussed.

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