Archive for April, 2012

Kinetics and metabolism of chlorine by-products

Kinetics and metabolism of chlorine by-products

The source document for this Digest states:

Trihalomethanes

The THMs are absorbed, metabolized and eliminated rapidly by mammals after oral or inhalation exposure. Following absorption, the highest tissue concentrations are attained in the fat, liver and kidneys. Half-lives generally range from 0.5 to 3 h, and the primary route of elimination is via metabolism to carbon dioxide. Metabolic activation to reactive intermediates is required for THM toxicity, and the three brominated species are all metabolized more rapidly and to a greater extent than chloroform. The predominant route of metabolism for all the THMs is oxidation via cytochrome P450 (CYP) 2E1, leading to the formation of dihalocarbonyls (i.e., phosgene and brominated congeners), which can be hydrolysed to carbon dioxide or bind to tissue macromolecules. Secondary metabolic pathways are reductive dehalogenation via CYP2B1/2/2E1 (leading to free radical generation) and glutathione (GSH) conjugation via glutathione- S-transferase (GST) T1-1, which generates mutagenic intermediates. The brominated THMs are much more likely than chloroform to proceed through the secondary pathways, and GST-mediated conjugation of chloroform to GSH can occur only at extremely high chloroform concentrations or doses

Haloacetic acids

The kinetics and metabolism of the dihaloacetic and trihaloacetic acids differ significantly. To the extent they are metabolized, the principal reactions of the trihaloacetic acids occur in the microsomal fraction, whereas more than 90% of the dihaloacetic acid metabolism, principally by glutathione transferases, is observed in the cytosol. TCA has a biological half-life in humans of 50 h. The half-lives of the other trihaloacetic acids decrease significantly with bromine substitution, and measurable amounts of the dihaloacetic acids can be detected as products with brominated trihaloacetic acids. The half-lives of the dihaloacetic acids are very short at low doses but can be drastically increased as dose rates are increased.

Haloaldehydes and haloketones

Limited kinetic data are available for chloral hydrate. The two major metabolites of chloral hydrate are trichloroethanol and TCA. Trichloroethanol undergoes rapid glucuronidation, enterohepatic circulation, hydrolysis and oxidation to TCA. Dechlorination of trichloroethanol or chloral hydrate would lead to the formation of DCA. DCA may then be further transformed to monochloroacetate (MCA), glyoxalate, glycolate and oxalate, probably through a reactive intermediate. No information was found on the other haloaldehydes and haloketones.

Haloacetonotriles

The metabolism and kinetics of HANs have not been studied. Qualitative data indicate that the products of metabolism include cyanide, formaldehyde, formyl cyanide and formyl halides.

Halogenated hydroxyfuranone derivatives

3-Chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone (MX) is the member of the hydroxyfuranone class that has been most extensively studied. From animal studies, it appears that the 14C label of MX is rapidly absorbed from the gastrointestinal tract and reaches systemic circulation. MX itself has not been measured in blood. The MX label is largely excreted in urine and faeces, urine being the major route of excretion. Very little of the initial radiolabel is retained in the body after 5 days.

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Metabolism of Chloroform in the Human Liver and Identification of the Competent P450s

  1. Simonetta Gemma,
  2. Luciano Vittozzi and
  3. Emanuela Testai

+ Author Affiliations


  1. Biochemical Toxicology Unit, Comparative Toxicology and Ecotoxicology Laboratory, Istituto Superiore di Sanità, Rome, Italy
  1. Dr. Emanuela Testai, Istituto Superiore di Sanità, Comparative Toxicology and Ecotoxicology Laboratory-Biochemical Toxicology Unit, Viale Regina Elena 299, I-00161 Rome, Italy. E-mail: testai@iss.it

Metabolism of Chloroform

The oxidative and reductive cytochrome P450 (P450)-mediated chloroform bioactivation has been investigated in human liver microsomes (HLM), and the role of human P450s have been defined by integrating results from several experimental approaches: cDNA-expressed P450s, selective chemical inhibitors and specific antibodies, correlation studies in a panel of phenotyped HLM. HLM bioactivated CHCl3 both oxidatively and reductively. Oxidative reaction was characterized by two components, suggesting multiple P450 involvement. The high affinity process was catalyzed by CYP2E1, as clearly indicated by kinetic studies, correlation with chlorzoxazone 6-hydroxylation (r = 0.837; p < 0.001), and inhibition by monoclonal antihuman CYP2E1 and 4-methylpyrazole. The low affinity phase of oxidative metabolism was essentially catalyzed by CYP2A6. This conclusion was supported by the correlation with coumarin 7-hydroxylase (r = 0.777; p < 0.01), inhibition by coumarin and by the specific antibody, in addition to results with heterologously expressed P450s. Chloroform oxidation was poorly dependent on pO2, whereas the reductive metabolism was highly inhibited by O2. The production of dichloromethyl radical was significant only at CHCl3concentration ≥1 mM, increasing linearly with substrate concentration. CYP2E1 was the primary enzyme involved in the reductive reaction, as univocally indicated by all the different approaches. The reductive pathway seems to be scarcely relevant in the human liver, since it is active only at high substrate concentrations, and in strictly anaerobic conditions. The role of human CYP2E1 in CHCl3 metabolism at low levels, typical of actual human exposure, provides insight into the molecular basis for eventual difference in susceptibility to chloroform-induced effects due to either genetic, pathophysiological, or environmental factors.

Chloroform is a ubiquitous atmospheric and water contaminant. Beside its extensive use as a solvent in industrial processes, it is formed as a by-product during the chlorination of water intended for human use and paper bleaching. Due to its volatility, chloroform can be easily released from waste or chlorinated waters into the atmosphere or in the ambient air. Therefore, a large part of the human population may be chronically exposed to chloroform from different sources, although drinking water has been considered the main one. Recently, routes of exposure other than oral consumption of chlorinated water have been evaluated as relevant. Indeed, some indoor activities, such as showering or bathing as well as cooking and housekeeping, may significantly contribute to total chloroform body burden through dermal and inhalation exposure (Wallace, 1997; Backer et al., 2000). The main concern for public health arose with the carcinogenic potential of chloroform in experimental animals (NCI, 1976; Jorgenson et al., 1985), which is strain-, species- and gender-specific (IPCS, 1994).

No studies of chronic toxicity or cancer incidence in humans exposed exclusively to chloroform are available. Nevertheless, there are a number of epidemiological studies on populations exposed to chlorinated drinking water, some of which evidenced a weak association between water consumption and cancer of the bladder and lower gastrointestinal tract (Hogan et al., 1979; Gottlieb et al., 1981; Cantor et al., 1998;Hidelsheim et al., 1998). Moreover, some adverse reproductive outcomes have been recently reported in humans exposed to chloroform via drinking water (Gallagher et al., 1998; Waller et al., 1998). However, the poor assessment of exposure and the concomitant presence of many water contaminants, including other trihalomethanes and disinfection by-products, makes it difficult to establish a causal link between chloroform itself and adverse effects in humans.

The required step for CHCl3-induced toxicity is the cytochrome P450 (P4501)-mediated bioactivation to reactive metabolites (IPCS, 1994; Constan et al., 1999) (Fig. 1). Extensive in vitro and in vivo studies on rodents have demonstrated that chloroform may be metabolized oxidatively to trichloromethanol, which spontaneously decomposes to the electrophilic phosgene (Mansuy et al., 1977; Pohl et al., 1977). COCl2 is highly reactive and binds covalently to cell components containing nucleophilic groups, including proteins, phospholipid (PL) polar heads, and reduced glutathione (Pohl et al., 1981; Testai et al., 1990; De Biasi et al., 1992; Gemma et al., 1996; Vittozzi et al., 2000). Alternatively, phosgene may be hydrolyzed by reacting with water, yielding carbon dioxide and hydrochloric acid (Fig. 1). In anoxic or hypoxic conditions, chloroform may be reduced to dichloromethyl radical (Tomasi et al., 1985; Testai et al., 1995), which is able to bind to PL-fatty acyl chains (De Biasi et al., 1992;Gemma et al., 1996; Vittozzi et al., 2000) or to abstract a hydrogen atom from the biological environment, leading to dichloromethane (Testai et al., 1995) (Fig. 1). The relative ratio between the two pathways depends on the oxygen partial pressure, on chloroform concentration and is specie-, organ- and gender-specific (Ade et al., 1994; Gemma et al., 1996; Vittozzi et al., 2000).

Figure 1

View larger version:

Figure 1

The two pathways of chloroform bioactivation.

In rodents, it has been evidenced that at low concentration chloroform is oxidized by CYP2E1 (Testai et al., 1996; Constan et al., 1999). At higher CHCl3 concentration, in the presence of oxygen, phosgene formation is catalyzed by CYP2B1/2, while in anoxic conditions dichloromethyl radical production seemed to be mediated by constitutive P450s (Testai et al., 1996). These direct observations supported a number of studies, showing the potentiation effect of a variety of CYP2E1 and 2B1/2 inducers on chloroform-induced toxicity (Sato et al., 1980; Stevens and Anders, 1981; Branchflower et al., 1983).

Only rare data on chloroform metabolism in human tissues have been published (Fry et al., 1972; Testai et al., 1991). No direct information on the human P450(s) involved in the reaction is available at present, although CYP2E1 is suspected as the major catalyst of chloroform metabolism. The knowledge of the P450(s) responsible for CHCl3 bioactivation can provide useful information to identify the population group characterized by higher susceptibility to chloroform toxicity. Moreover, it would be possible to evaluate the environmental influence on susceptibility to chloroform-induced effects, through the study of metabolic interaction due to the combined exposure with other xenobiotics, affecting the rate of chloroform metabolism. Therefore, we have undertaken this study to characterize oxidative and reductive chloroform metabolism in human liver microsomes (HLM). In addition, we have identified the human P450(s) responsible for COCl2 andCHCl2 formation, by using different experimental approaches, including cDNA-expressed enzymes, correlation studies in a panel of phenotyped HLM, and inhibition by either chemical-selective inhibitors or anti-human P450 antibodies (Abs).

Evaluation of Recycled Crushed Glass Sand Media for High-Rate Sand Filtration

Evaluation of Recycled
Crushed Glass Sand Media
for High-Rate Sand Filtration
NIST MEP
Environmental Program
EVALUATION OF RECYCLED CRUSHED GLASS
SAND MEDIA FOR HIGH-RATE SAND FILTRATION
FINAL REPORT
PREPARED FOR:
CWC
A division of the Pacific NorthWest Economic Region (PNWER)
2200 Alaskan Way, Suite 460
Seattle, WA 98121
October 1998
PROJECT CONSULTANT:
Aquatic Commercial Industries
This recycled paper is recyclable
Copyright © 1998 CWC. All rights reserved. Federal copyright laws prohibit reproduction, in whole or in part, in any
printed, mechanical, electronic, film or other distribution and storage media, without the written consent of the CWC.
To write or call for permission: CWC, 2200 Alaskan Way, Suite 460, Seattle, Washington 98104, (206) 443-7746.
Disclaimer
CWC disclaims all warranties to this report, including mechanics, data contained within and all other aspects, whether expressed or
implied, without limitation on warranties of merchantability, fitness for a particular purpose, functionality, data integrity, or accuracy of
results. This report was designed for a wide range of commercial, industrial and institutional facilities and a range of complexity and
levels of data input. Carefully review the results of this report prior to using them as the basis for decisions or investments.
Report No. GL-98-1
ACKNOWLEDGMENTS
CWC is a nonprofit organization providing recycling market development services to both businesses and
governments, including tools and technologies to help manufacturers use recycled materials. CWC is an
affiliate of the national Manufacturing Extension Partnership (MEP) – a program of the US Commerce
Department’s National Institute of Standards and Technology. The MEP is a growing nationwide
network of extension services to help smaller US manufacturers improve their performance and become
more competitive. CWC also acknowledges support from the US Environmental Protection Agency and
other organizations.
Special thanks to the following individuals, companies and agencies, whose help and support made this
evaluation possible.
Bally Total Fitness for providing their facility in Federal Way. To Mike Chapman, Steve Smith, and other
staff for their help in data collection and mechanical work.
Wayne Smith, at WMS Aquatics for his continued interest and support during this evaluation.
City of Bellingham, Washington for loaning the Hach Turbidometer for the duration of the project.
Fred Miller and the staff at TriVitro for their dedication, technical and problem solving assistance, and for
providing the glass sand media.
TABLE OF CONTENTS
EXECUTIVE SUMMARY………………………………………………………………………………………………..i
1.0 BACKGROUND…………………………………………………………………………………………………….1
2.0 PLAN AND SETUP………………………………………………………………………………………………..3
3.0 FILTER EQUIPMENT…………………………………………………………………………………………..4
4.0 ADDITIONAL EQUIPMENT…………………………………………………………………………………5
5.0 ESTABLISHING THE CONTROL DATA ………………………………………………………………6
6.0 MEDIA CHANGE………………………………………………………………………………………………….8
7.0 FLOW METER PROBLEMS…………………………………………………………………………………8
8.0 GLASS SAND DATA……………………………………………………………………………………………..9
9.0 CONCLUSIONS…………………………………………………………………………………………………..12
10.0 RECOMMENDATIONS FOR FURTHER STUDY……………………………………………….13
11.0 REFERENCES…………………………………………………………………………………………………….15
APPENDIX A: FIGURES
Figure 1: Comparison of Average Recirculation Flow Rates
Figure 2: Comparison of Average Influent Pressures
Figure 3: Comparison of Average Effluent Filter Pressures
Figure 4: Comparison of Average Differential Filter Pressures
Figure 5: Comparison of Average Turbidity Units
Figure 6. Comparison of Backwash Time
APPENDIX B
1. Specification Sheet
© CWC 1998 i
EXECUTIVE SUMMARY
A field test was performed to examine the potential for using finely processed recycled glass sand as a
filtration medium in high-rate sand filtration. Previous CWC studies and lab tests at Pennsylvania State
and San Jose State Universities have demonstrated that, when properly processed, recycled glass is an
effective filtration medium as a substitute for natural sand in many applications. This field test at an
athletic club swimming pool was designed to determine whether glass sand was able to attain or exceed
the clarity achieved with conventional sand and to establish how the cleaning characteristics of glass
sand media compared with sand in terms of frequency and water use. This project was also intended to
provide the filtration industry with information for economic evaluations to be made regarding the market
potential for recycled glass sand as a filtration medium.
The test was run from July 1997 to March 1998 at the Bally Total Fitness Center in Federal Way,
Washington. Three filters were used, with a filter surface area of 21.18 square feet. The maximum
design flow for the filter system, at 15 gallons per minute per square foot of filter area, was 327 gallons
per minute. Each filter contained 275 pounds of 1/8″ x 1/4″ pea gravel and 650 pounds of #20 silica
sand. Control data on turbidity, operating pressures and backwash efficiency was developed by
observing and testing the filters’ operation through four complete filter runs with conventional silica sand
media (US Sieve Standard #20 x 30).
The conventional media was removed and replaced with VitroClean™ crushed glass sand media
manufactured by TriVitro Corporation in Seattle, Washington. Again, data was collected during
repeated filter runs with the recycled glass media. This data was then compared to the control data for
silica sand.
© CWC 1998 ii
The field evaluation revealed the following trends that illustrate the performance of recycled glass sand
media compared to conventional sand media:
1. Improved water clarity shown by a 25% reduction in National Turbidity Unit (NTU) readings.
2. Increased backwash efficiency shown by a 23% reduction in water used for backwashing.
3. Approximately 20% less glass sand (by weight) required for filtration.
An anomaly in filter pressure differentials was found during the data analysis phase. While it is
unfortunate that the data on influent pressure and flow was inconsistent, other critical and positive
information regarding improved water clarity and increased backwash efficiency remains unaffected.
The data supports findings that indicate possible performance advantages in using recycled glass in highrate
sand filtration. Glass appears to be able to catch more turbid particles, thereby cleaning water
more effectively and efficiently. This may allow pool filters to be operated for fewer hours to achieve
desired water clarity, thereby saving energy and equipment life. More efficient backwashing uses less
pool water that has already been chemically treated, heated and filtered and requires less operational
and staff time.
Of particular interest is the fact that these results were achieved by using 20% less filter media by
weight. In economic terms, filter media is measured and purchased by weight; costs for filter media are
incurred in both the acquisition and disposal of media. Simply by the fact that glass is 20% less dense
than silica sand, real savings in pool operating costs can be achieved, especially when improved water
clarity and increased backwash efficiency are added considerations.
© CWC 1998 1
1.0 BACKGROUND
This study compares the performance of a recycled glass filtration medium with conventional sand in
high-rate recirculating sand filters. Previous studies sponsored by the CWC have tested glass as a
filtration medium in slow sand filtration for municipal water treatment, septic treatment sand filtration,
and monitoring well filtration. Those studies demonstrated that, when properly processed, recycled
glass is an effective filtration medium as a substitute for natural sand in many applications. This study
extends the knowledge base of effective filtration uses of recycled glass.
The water treatment and swimming pool industries have used slow-rate sand filtration for over a
century. In slow-rate filtration, water flows by gravity through a filter bed. Because the only driving
force is gravity, slow-rate filters require large amounts of filtration media and large facilities. In addition,
flocculants (broad-based polymer filtration aids) are often needed to cause particles to agglomerate for
physical removal in the filter. In order to reduce the size of filtration facilities while maintaining filtration
efficiency, gravity sand filters evolved into pressurized “rapid-sand” filters, with flow rates designed for
three to five gallons per minute per square foot (gpm/sq ft). These filters use more tightly graded
filtration media.
In the 1950’s, pressurized sand filters with filtration rates of up to 20 gpm/sq ft were introduced. These
“high-rate” sand filters did not use flocculants. The lack of flocculants, along with the higher flow rates,
made the need for high quality filtration media even more critical. These filters require very tightly
graded media, typically U.S. Standard Sieve #20 x #30 (ASTM E11 – .850mm x .600mm) silica sand,
with high uniformity of size, no clays or non-silica soils, and sub-angular grain shape.
The Northwest United States (especially Oregon and Washington) does not have natural sources of
high quality sand media for high-rate filters. This has resulted in higher costs for media because the
material must be shipped from other parts of the country.
© CWC 1998 2
TriVitro Corporation of Seattle, Washington, processes glass for a variety of uses, including tile
manufacturing, paint additives, and media for abrasive blasting. TriVitro manufactures VitroClean™,
a filter medium that has been processed specifically to meet swimming pool filter specifications. As a
result of TriVitro’s process, VitroClean™ glass sand particles have the sub-angular grain shape
required by the filter industry.
The glass used in this project was post-industrial plate glass scrap from window and door
manufacturers. The glass is processed through a series of crushers, dryers, and screens to remove
contaminants and to produce a range of uniformly sized filtration media. Post-industrial glass was
chosen for this test because it is completely free of the potential organic (sugars, labels, etc.) and
inorganic (aluminum rings, steel caps, etc.) contamination that can be present in post-consumer
container glass. The potential for these types of contamination would introduce another variable in the
analysis, and it was beyond the scope of this project to test methods for cleaning post-consumer glass.
Other studies of crushed glass filtration media for slow sand or rapid sand filters have included
“Crushed, Recycled Glass as a Water Filter Media”, by Richard Huebner, Ph.D, Penn State
University, 1994, and “Recycled Glass: Development of Market Potential”, by R. Guna Selvaduray,
San Jose State University, 1994. These studies have indicated that crushed glass media filters function
as well as conventional sand filters and may remove small turbid particles more efficiently than
conventional sand media.
The two specific issues of special interest in this study were:
1. to determine whether glass sand was able to attain or exceed the clarity achieved with conventional
sand; and
© CWC 1998 3
2. to determine how glass sand compared with conventional sand in cleaning frequency and water use.
2.0 PLAN AND SET UP
This study examined and compared the performance of recycled glass sand media with a conventional
sand medium in high-rate sand filters during actual operating conditions. Data was first collected on the
operating characteristics of conventional sand media, then that data was compared with recycled
crushed glass sand media. The original parameters planned for evaluation of the two media included:
· Visual inspection of the pool water
· Recirculation flow rate
· Backwash flow rate
· Turbidometer readings
· Influent and effluent filter pressures
The visual inspection (by photo) was eliminated early in the evaluation because the range of changes
seen in turbidity were not observable through visual or photographic inspection. In addition, unforeseen
field conditions affected the recirculation flow rate and influent pressure readings and resulted in limiting
the conclusions that can be drawn from this project.
The Pacific West Health Club (Federal Way, WA) was chosen as the test site. Upgrades required at
the facility to facilitate this study included upsizing of a backwash pit by adding an auxiliary backwash
tank with a gravity drain to an approved sewer connection, and installation of new digital flow meters,
sight glasses, pressure gauges, and a turbidometer.
3.0 FILTER EQUIPMENT
Filters used for this evaluation were “Triton” TR series filters manufactured by PacFab, Inc. These
filters are common in the swimming pool industry, with an estimated 5,000 to 7,000 filter vessels located
© CWC 1998 4
on the West Coast of the United States. Each filter contained 7.06 square feet of cross-sectional filter
area. Three filters were on one manifold, for a total of 21.18 square feet of filter surface area. The
maximum design flow for this installation, at 15 gallons per minute (gpm) per square foot of filter area,
was 327 gpm. These filters are manufactured for flow rates between 5 and 20 gpm per square foot.
Each filter contained 275 pounds of 1/8″ x 1/4″ pea gravel and 650 pounds of #20 silica sand. The
sand depth from surface to bottom drain lateral was 13.5 inches. The bottom drain laterals were
grooved to prevent sand particles larger than #30 silica from leaving the filter. Each filter was fitted
with manual air relief valves.
The backwash sight glass was not sufficient for this study, so an additional in-line sight glass was
installed on the backwash discharge line between the filters and the backwash holding tank. This sight
glass was fitted with two parallel lines, allowing a technician to evaluate the clarity of the backwash
water to determine when the filter had been sufficiently backwashed.
The size of the existing backwash holding tank was unable to hold a complete backwash discharge
from even one filter. An additional backwash holding tank with a capacity of 300 gallons was installed.
This allowed a complete backwash of three minutes per tank. The holding tank water gravity-flowed
into the sewer pit.
4.0 ADDITIONAL EQUIPMENT
The recirculation flow rate and the backwash flow rate were monitored by Signet Model 5100 digital
flow meters. One was placed on the effluent recirculation line downstream of the filter, prior to chemical
© CWC 1998 5
injection points, measuring recirculation flow. The other flow meter was placed in the backwash
discharge line. To assure accuracy, the devices were installed in locations providing laminar flow (10
pipe diameters prior to measuring device and 5 pipe diameters downstream of the device of clear pipe:
no fittings, elbows, etc.).
Pressure readings were taken with stainless steel pressure gauges manufactured by Ashcroft with oil
filled cases for vibration dampening. They were located on the filter cap and the effluent filter line; six
gauges were used, two on each filter. Since the filters were manifolded, the gauge readings were
averaged to achieve consistency. The gauges chosen were 0-60 psi. In retrospect, 0-30 psi gauges
would have suited the project better. Pressure gauge readings of influent and effluent pressures were
used for the calculation of pressure differential. Differential pressure measurements provide the best
evaluation of filter bed performance with respect to collection of suspended particles, reflected by
resistance created across the filter.
Water clarity was determined from turbidity units measured by a Hach Turbidometer, model 1720A.
Measurements were recorded in National Turbidity Units (NTU’s). According to standards established
by the National Sanitation Foundation, pool water that is rated “excellent” maintains a NTU reading of
.5 or less.
Data collection sheets and procedures were developed in-house. Two National Swimming Pool
Foundation Certified Pool Operators were employed as primary and secondary technicians. Training in
data collection and backwashing procedures was completed and data collection began on July 1, 1997.
The swimming pool was intended to be the primary test site. However, since a spa system was located
in the same room, both systems were fitted with the equipment described above and comparative
evaluations were conducted. A system of valves was installed so that the Hach Turbidometer could
measure either the pool or the spa. After switching the water source, a waiting period of ten minutes
© CWC 1998 6
was established to allow the Turbidometer to adjust to the new water. The spa water often provided
skewed turbidity readings because the spa air jets introduced air bubbles that were not entirely
dissipated or removed by filtration. The air bubbles appeared as turbid particles to the turbidometer.
5.0 ESTABLISHING THE CONTROL DATA
The original silica sand in the filters was tested by an independent test lab and rated “very good.” The
sieve size was primarily U.S. Standard #20 x 30, with a size coefficient (D60/D10) of 1.4. The size
coefficient is the ratio of the screen size through which 60% of the medium passes, divided by the screen
size through which 10% of the medium passes. The plan was to operate with the conventional sand for
no less than four complete filter runs (period between backwashes) to establish a “control database” to
which the crushed glass sand media would be compared.
There was difficulty with the backwash flow meter because debris continued to foul the transducer
paddle wheel. An in-line oversized strainer basket was installed to capture large debris and the problem
was partially solved. Data collection was resumed the following week, however, small particles
continued to clog the flow meter too often to provide reliable flow data. As a data back-up, backwash
duration (in time) was noted. While this was not as accurate as flow, it did provide a backwash
standard that could be measured and evaluated against the glass sand media.
The pool water clarity was excellent with the original conventional sand. Due to inadequate lighting for
quality photos and the subtle differences expected, the visual evaluations and recordings originally
planned were not conducted.
Collected data was consistent each day, with expected increases and decreases in pressures, flow and
turbidity readings corresponding to filter performance as the filters filled with turbid particles. The
control data phase was completed in eight weeks (see Appendix A for Figures 1 through 6).
© CWC 1998 7
The data was an average of the pressure and flow characteristics recorded each week. However,
sometimes because of staff scheduling, data was not collected and some days were interpolated from
adjacent data. According to Washington State Health and Safety Regulations, after the
recirculation flow drops 10% (approximately 25 to 30 gallons per minute), backwashes must be
scheduled to clean the filters and to re-establish the desired flow. During the analysis of the baseline
sand and glass sand media, the time between filter backwashes was seven days in all but two cases
during the 17 weeks of data collection. Seven days was a convenient schedule for backwashing, so
scheduling and data charting were established on a seven-day cycle. Figures one through five,
therefore, reflect pressure and turbidity averages for each successive day following a backwash.
The backwash flow rate measurements were somewhat skewed by flow meter problems. The average
duration (in minutes) of backwash (total of six backwashes recorded) of the conventional sand was
three minutes, twenty-one seconds. Although this was somewhat subjective, the backwash sight glass
was fitted with two black parallel lines that were to be viewed through the backwash water. When the
edges of the lines were clear, the backwash was deemed complete.
6.0 MEDIA CHANGE
The conventional media was removed and replaced with the TriVitro crushed glass sand media. The
sand replacement took approximately one day. The 1/8″ x 1/4″ rounded pea gravel bed below the
medium was left in place. The underdrain laterals were surrounded and covered with gravel to a height
of approximately one-inch above the laterals. This gravel allowed the filter to better distribute the
backwash flow to the sand bed and is required by the National Sanitation Foundation (NSF) for the
filter’s approval at filter rates of 15 gpm (and higher) per square foot of filter area.
© CWC 1998 8
The filter manufacturer’s specifications required 6.5 cubic feet of medium for each filter (a total of 19.5
cubic feet for the system). This would have required 1,950 pounds of silica sand. However, glass is
less dense than silica sand, so only 1,560 pounds were needed, demonstrating a 20% savings in
filtration media by weight. This savings would be reflected in both raw material and shipping costs. This
difference is derived from two factors . First, the specific gravity of glass is 2.53, compared with
approximately 2.75 for sand, a 10% difference. In addition, the newly fractured glass particles appear
to not pack as tightly as the sand grains. Therefore, the interstitial spaces between the glass particles
are, on average, larger and have less rounded edges than sand grains. This confirmed previous research
at Pennsylvania State University.
7.0 FLOW METER PROBLEMS
Upon installation of the glass medium, the Signet flow meter equipment failed on a regular basis.
Evaluation of the recirculation flow meter transducer revealed that glass particles (estimated to be 40
micron and smaller) were passing through the filter underdrain laterals, causing the rotor to jam. After
evaluation of the glass filtration medium, it was determined that there were too many “fines” left in the
first batch of VitroClean™ sand after processing. The problem began to lessen
as repeated backwash procedures eventually removed the smaller sand particles. However, at this
point there was a question of whether the glass filtration medium as delivered in the first batch would
meet most pool owners’ satisfaction.
During the same period, TriVitro had improved its glass processing to the extent that TriVitro’s
engineers were confident that their process improvements had almost totally eliminated the fines
carryover. Therefore, it was recommended that the original glass sand be replaced and additional data
collected using this improved media product. The CWC agreed to a project extension and an
additional six weeks of testing was undertaken.
© CWC 1998 9
The final TriVitro product tested was VitroClean™ 25N, with a coefficient of uniformity of 1.40 and
effective size of .50mm. Effective size is defined as the size opening that will just pass 10% (by weight)
of a representative sample of the filter material. A specification sheet is included in Appendix B.
8.0 GLASS SAND PERFORMANCE
With the exception of the backwash duration data, the glass sand media data was collected from the
second sand media load. In fact, after four weeks of operation and backwashing and most of the “fines”
removed, the media characteristics of the “cleaned” glass sand (the first medium after
being subjected to multiple backwashes) and the new “improved” glass sand were virtually identical.
The glass sand media data is illustrated in Figures 1 through 6.
Recirculation Flow
After switching to the glass sand media, the most immediate and surprising change was the measurable
increase in recirculation flow (Figure 1). This was surprising in light of the increased influent pressure
readings (Figure 2). In general, for a centrifugal pump, it is expected that the
only way to achieve increased flow is in conjunction with decreased pressure drop. In this case, effluent
pressure was constant, as shown in Figure 3. Since influent pressures increased, the differential
pressure across the filter must have increased, as shown in Figure 4. Explaining the strange and
conflicting data in this field test is difficult.
The CWC’s project manager and the technical consultant for this project, Aquatic Commercial
Industries, share responsibility for this problem. In the first month a differential pressure increase should
have been seen along with an increased flow rate; people with experience with pump curves should
have realized there was a problem and investigated. Unfortunately, the issue was not noticed until the
curves were generated.
© CWC 1998 10
Another possible source of inaccuracy in the project was the fact that 60 psi gauges were used to take
readings as low as 3 psi. Good instrument practice requires that mechanical gauges be read within the
middle 50% of the range, in this case 15 to 45 psi. It is possible that cumulative gauge misreadings
contributed to this problem.
It is also possible that a reduction in the pump suction head (possibly stemming from a change in the
pump strainer basket and/or its maintenance) lowered the total system head, therefore allowing higher
flow as well as higher influent pressures.
Water Clarity
NTU readings actually dropped 25% with installation of the glass medium (Figure 5). This significant
drop in NTU readings indicates that glass sand media may trap finer turbid particles than conventional
sand, resulting in clearer water.
Backwash
The average duration of backwash (in minutes) was 2:34 based upon ten backwashes, compared to
3:21 for silica sand based on six backwashes. Therefore, there was a reduction of as much as 23% of
water used for backwashing glass sand media compared to conventional sand.
The glass media seemed to fluidize quicker and require less water for a complete backwash. This is
probably a result of a combination of causes. First, glass sand has lower density. The lighter material
simply floats more easily with backwash flow. In addition, glass particles have a more angular shape
and relatively flatter fractured sides. This may mean that glass particles pack less densely than sand and
therefore require less backwash water to “unpack” during filter cleaning.
© CWC 1998 11
The noteworthy improvements in the backwash results in this field test were consistent with trends
identified in the San Jose State University study (Selvaduray) where measurements of the sand bed
expansion were greater with the glass sand media than with conventional sand.
Consumption
In all cases, the amount of media required by weight was substantially less (approximately 20%) for the
recycled glass sand than for silica sand. In pool operations this difference would be noted twice – first
in the purchase of filter media and second in the disposal of spent media. Both are purchased by weight
rather than by volume.
Summary
The field evaluation revealed the following trends:
1. a 25% reduction in National Turbidity Unit readings;
2. a 23%+ reduction in time for backwashing; and
3. approximately 20% less glass sand (by weight) is required for filtration.
It is worthy to note that items 1, 2, and 3 were mirrored in the spa test data.
Applicability to other filter systems
Industries and governments use high rate filtration systems in a variety of settings. Findings from this and
preceding studies show strong potential for glass to be used in commercial and municipal filtration. It is
likely that the benefits concluded from this swimming pool field evaluation would be seen in other types
of filtration applications, such as stormwater, agricultural and industrial filtration.
9.0 CONCLUSIONS
This project was intended to be a full-scale “field test” of recycled glass for high-rate sand filtration.
The work done at San Jose State University and Pennsylvania State University showed that, in
laboratory scale, recycled glass had equal or better efficiency than conventional sand. Consistent with
© CWC 1998 12
this prior research, recycled glass sand media performed as well or better than conventional filter sand in
swimming pool filtration.
The main advantages of recycled glass sand over conventional sand are:
1. Improved Water Quality. Finer particles were removed in the filter more efficiently, reflected by
the 25% decrease in NTU’s. The findings showed repeatedly that recycled glass sand cleaned
water more effectively. Clearer water is always desired. Being able to catch smaller turbid particles
makes high-rate filtration sand even more efficient and therefore attractive over other types of
filtration media. This advantage may allow recirculation systems to be operated fewer hours in
those locations that allow pool systems to be turned off during non-use periods. This saves
electrical energy and extends equipment longevity.
2. More Efficient Backwashing. Less backwash water was required to clean the filter medium. As
these test results are duplicated in repeated future usage, the ability to backwash with over 20% less
water is a major advantage that can prove valuable both in construction and in operation. The cost
of sewer lines and holding tanks can be reduced. Most importantly, water has been saved. Beyond
the value of the water resource, pool water has an added economic value when it has been
chlorinated, pH adjusted, alkalinity adjusted, hardness adjusted, heated and filtered. The savings
through more efficient backwashing are measured both in the cost of the water consumed and then
disposed (some facilities that are charged per 100 cubic feet of water that is treated by sewage
plants). Costs for chemicals and for heating water are also reduced.
3. Less Media. Glass sand media is less dense and therefore lighter than conventional sand filter
media. Less media by weight is required. Shipping, handling and disposal costs would be saved
proportionately to the ratio of density of glass vs. silica sand media., approximately 20%.
© CWC 1998 13
The benefits described in 1 and 2 above (i.e., savings in pool operating costs, energy, water usage, etc.)
are achieved with 20% less material by weight.
It cannot be emphasized strongly enough that these results reflect a test of a specific glass
filtration medium produced by a specific processor. Although they confirm the efficacy of
properly processed glass as a recirculating water filtration medium, they do not support the
use of glass for this application from any other processor, unless that processor is able to
produce media that meets industry specifications for consistency in particle shape, size
distribution, cleanliness and uniformity.
10. 0 RECOMMENDATIONS FOR FURTHER STUDY
The following recommendations are provided to those who may wish to undertake further testing in
swimming pool operations:
1. The use of ultra-sonic flow measurement devices with totalizers will allow for a more precise
measurement of filter media backwash flow and water usage. The paddle wheel units, though very
accurate, have small tolerances for particulate matter in the water and can become clogged.
2. The ability to record data seven days per week every week is important in order to monitor trends.
3. Controlling pool operating conditions at the field test facility is important. Filtration equipment
repairs or modifications and staffing changes can interfere with data collection and skew results.
4. Care must be taken to isolate and monitor changes in operating pressures due to the use of recycled
glass media. Using gauges that more accurately reflect the actual pressure conditions (see Section
4), careful evaluation of suction and discharge head condition on the recirculation pump during the
baseline evaluation and new media evaluation is important. This can be accomplished with vacuum
and pressure gauges on the suction and discharge lines of the pump.
© CWC 1998 14
5. Test designs should track filter ripening and run times. Reports from the Pennsylvania State and San
Jose State University studies showed faster ripening and longer run times. It would be valuable to
determine if these trends are readily observed in field test conditions.
© CWC 1998 15
11.0 REFERENCES
Certified Pool Operator Handbook, National Swimming Pool Foundation, Lester
Kowalski, Editor. 1990.
Aquatic Facility Operator Handbook, National Recreation and Park Association,
Kent Williams, 1994.
Washington State Health and Safety Code, for Swimming Pools.
Crushed, Recycled Glass as a Water Filter Media, Pennsylvania State University, 1994,
Richard Heubner PhD, Project Director.
Recycled Glass: Development of Market Potential, San Jose State University, 1994,
Dr. Guna Selvaduray
Crushed Glass as a Filter Media for Onsite Treatment of Wastewater, CWC. 1995
Examination of Pulverized Waste Recycled Glass as Filter Media in Slow Sand Filtration,
NYSERDA, October 1997.
APPENDIX A: FIGURES 1 THROUGH 6
Figure 1: Comparison of Average Recirculation Flow Rates
Figure 2: Comparison of Average Influent Pressures
Figure 3: Comparison of Average Effluent Filter Pressures
Figure 4: Comparison of Average Differential Filter Pressures
Figure 5: Comparison of Average Turbidity Units
Figure 6: Comparison of Backwash Time
APPENDIX B
1. Specification Sheet
Figure 1
Comparison of Average Recirculation Flow Rates (gallons per minute)
187.5 182.5 176.7 173 168.5 162 155.5
277 272.5 268.2 265 262.5 257.5 252
0
50
100
150
200
250
300
Day 1 Day 2 Day 3 Day 4 Day 5 Day 6 Day 7
Con Sand
Glass
Figure 2
Comparison of Average Influent Pressures (pounds per square inch)
9.25
8.7
9.8
8 8.15 8.45
11 10.45
11.25 11.75 12.15
12.6
13.3
14.05
0
2
4
6
8
10
12
14
16
Day 1 Day 2 Day 3 Day 4 Day 5 Day 6 Day 7
Con Sand
Glass
Figure 3
Comparison of Average Effluent Filter Pressures (pounds per square inch)
4.1
4.55
3.6
5.75
5.3
5.07
3.05
5.8 5.4
5
4.75
4.25
3.75
3.2
0
1
2
3
4
5
6
Day 1 Day 2 Day 3 Day 4 Day 5 Day 6 Day 7
Con Sand
Glass
Figure 4
Comparison of Average Differential Filter Pressures (pounds per square inch)
2.65
4.05
5
2.2
3.34
6
7.05
10.4
9.35
8.35
7.4
6.75
5.85
5.2
0
2
4
6
8
10
12
Day 1 Day 2 Day 3 Day 4 Day 5 Day 6 Day 7
Con Sand
Glass
Figure 5
Comparison of Average Turbidity in National Turbidity Units (NTUs)
0.75
0.5
0.4
0.31
0.28 0.27
0.55
0.45
0.4 0.4 0.4 0.4
0.55
0.27
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
Day 1 Day 2 Day 3 Day 4 Day 5 Day 6 Day 7
Con Sand
Glass
Figure 6
Comparison of Average Backwash Time in Minutes
0:00
0:28
0:57
1:26
1:55
2:24
2:52
3:21
3:50
Week 1 2 3 4 5 6 7 8 9 10
Con Sand
Glass
Note: Conventional sand recorded for 6 weeks, Glass sand for 10 weeks.
VITRO
Water Filtration Sand
An Amorphous Soda-Lime Silicon Dioxide Product
Typical Specifications
VitroClean 25N
U.S. Sieve No. % Retained on Sieve
14 0.0
16 0.2
20 4.0
25 31.5
30 46.2
40 16.5
50 0.4
pan 1.2
Effective Size 0.50mm
Coeff.Uniformity 1.40
Specific Gravity 2.53
Est. Sphericity 0.30
Est. Roundness Angular-Subangular
Other filtration sand sizes are available
Product specifications are approzimate & subject to change.
TRIVITROcorporation
351 Elliott Avenue West
Seattle, WA 98119-4010
Sales: 360-733-2122
Plant: 206-301-0181
Fax: 206-301-0183

Chlorine and Chloramine Removal with Activated Carbon

from Carbonresources.com

Municipalities routinely began
using chlorine to treat drinking
water starting in 1908 with
Jersey City, NJ. Its use has helped to virtually eliminate diseases
like typhoid fever, cholera and dysentery in the US and other
developed countries. Globally the World Health Organization
(WHO) estimates that 3.4 million people in underdeveloped
countries die every year from water-related diseases.
Use of chlorine in water can produce an undesirable taste;
therefore, many consumers prefer to remove it. Disinfection
byproducts (DBPs) may also unintentionally form when chlorine
and other disinfectants react with natural organic matter that is
in the water. To reduce DBP formation, many municipalities are
switching to monochloramine.
Monochloramine treatment was first used in Ottawa,
Ontario, Canada in 1916 and in Denver, CO in 1917. Use of
monochloramine took a downturn during World War II due to
ammonia shortages. Currently the US EPA estimates more than
30 percent of larger US municipalities use monochloramine.
It’s a common misperception that activated carbon removes
chlorine and monochloramine from water by adsorption.
Understanding how activated carbon
removes chlorine and monochloramine
from water is critical to the design and
operation of such systems.
Chlorine formation and
reactions
Use of chlorine is the most common
method to disinfect public water
supplies. Chlorine is a powerful germicide,
killing many disease-causing
microorganisms in drinking water, reducing
them to almost non-detectable
levels. Chlorine also eliminates bacteria,
molds and algae that may grow in
water supply systems.
US EPA’s maximum residual disinfection levels (MRDLs) are
four mg/L for chlorine; however, chlorine may cause problems
that activated carbon can help resolve. The addition of chlorine
to disinfect water is accomplished by one of three forms: chlorine
gas (Cl2), sodium hypochlorite solution (NaOCl) or dry calcium
hypochlorite, Ca (OCl)2.
The addition of any of these to water will produce
hypochlorous acid (HOCl). This disassociates into hypochlorite
ions (OCl-) to some degree. (The reaction is summarized
below).
Cl2 + H2O → HOCl + H+ + Cl–
HOCl – → H+ + OCl+
The ratio of hypochlorous acid and hypochlorite ion in water
is dependent upon pH level and, to a much lesser degree, water
temperature. The ratio of hypochlorous acid and hypochlorite ion
at various water pH and temperature is shown in Table 1.
It is important to understand the ratio of hypochlorous
acid and hypochlorite ion in water. First,
it has been estimated that hypochlorous
acid is almost 100 times more effective
for disinfection than hypochlorite ion. Secondly, activated
carbons more readily remove hypochlorous acid compared to
the hypochlorite ion.
Chlorine concentrations greater than 0.3 ppm in water can be
tasted. Activated carbon is very effective in removing free chlorine
from water. The removal mechanism employed by activated
carbon for dechlorination is not the adsorption phenomena that
occur for organic compound removal.
Dechlorination involves a chemical reaction of the activated
carbon’s surface being oxidized by chlorine. There are reactions
when hypochlorous acid and hypochlorite ion react with activated
carbon (shown below).
Carbon + HOCl → C*O + H+ + Cl–
Carbon + OCl– → C*O + Cl–
C*O represents the oxidized site of activated carbon after
reacting with chlorine; the chlorine has been reduced to chloride
ion (Cl-). These reactions occur very quickly.
Factors impacting
dechlorination
When designing an activated
carbon dechlorination system, several
process factors must be considered. If
the system is being designed for organic
removal and dechlorination, design
criteria for organic removal will override
design criteria for dechlorination.
Since organic adsorption onto activated
carbon is a slower process than
dechlorination, a system that has been
properly designed for organic removal
will work well for dechlorination.
When the design is strictly for dechlorination, consideration
must be given to any dissolved organics that may be present
in the water. These organics can reduce the capacity of carbon
for dechlorination by occupying the available sites used for
dechlorination.
Particle size of activated carbon is the most important factor
impacting effective dechlorination. The smaller the activated
carbon particles, the faster the dechlorination rate. A disadvantage
of smaller particles is greater pressure drop within the media bed
and, therefore, must be given careful consideration in the overall
system design.
A 20×50 mesh size granular activated carbon (GAC) will be
more effective than a 12×30 or 8×30 mesh GAC. Carbon block
filters are made with fine mesh powder activated carbon with
particle sizes predominantly between 50 and 325 mesh.
Carbon block filters, therefore, are very effective for
dechlorination because of their very small activated carbon
particle size. If a GAC dechlorination system was designed for
20×50 mesh GAC and it was replaced with 12×40 mesh GAC, it
Chlorine and Chloramine Removal
with Activated Carbon
By Robert Potwora
Table 1. Percentages of HOCl and OCl –
% HOCl % OCl – % HOCl % OCl –
pH 32°F 32°F 68°F 68°F
4 100.0 0.0 100.0 0.0
5 100.0 0.0 97.7 2.3
6 98.2 1.8 96.8 3.2
7 83.3 16.7 75.2 24.8
8 32.2 67.8 23.2 76.8
9 4.5 95.5 2.9 97.1
10 0.5 99.5 0.3 99.7
11 0.05 99.95 0.03 99.97
JUNE 2009 Water Conditioning & Purification
would need about 25 to 50 percent more 12×40 mesh GAC. If that
system was designed for 12×40 mesh GAC and it was replaced
with 8×30 mesh GAC, about 100 percent more 8×30 mesh GAC
would be needed.
Since dechlorination is a chemical reaction, the higher the
water temperature, the faster the dechlorination rate. Winter
water temperatures in northern climates can cause dechlorination
rates to be reduced by as much as half as compared to summer
water temperatures.
Although it is generally not feasible to adjust the pH of
the water, it does have an impact upon the dechlorination rate.
As discussed earlier, the pH level will affect the ratio of the
hypochlorous acid and the hypochlorite ion.
Since the removal rate for hypochlorite ion is slower than
that for hypochlorous acid, water at an extremely high pH will
require additional activated carbon for effective dechlorination.
Going from a neutral pH of 7 to a pH of 9 or 10 will require 30 to
60 percent more GAC for effective dechlorination.
The expected service life of 12×40 and 8×30 mesh GAC at a
water temperature of 70°F (21°C) and pH 7 is given in Figure 1.
Flowrates through the GAC bed were 4 GPM/ft3 GAC, 2 GPM/
ft3 GAC and 1 GPM/ft3 GAC. This corresponds to an empty bed
contact time (EBCT) of 1.9, 3.7 and 7.5 minutes respectively.
EBCT calculation equation is:
Volume of activated carbon (ft3)
Flow rate of the water (ft3/minute)
The chart assumes no organic or bacteria interference and
breakthrough at 0.1 ppm Cl2.
A typical activated carbon cartridge breakthrough curve
10
1
0.1
Influent chlorine, mg/L
Million gallons/cubic foot GAC
0.1 1 10 100
8×30 4 GPM/ft3 8×30 2 GPM/ft3 12×40 4 GPM/ft3
12×40 2 GPM/ft3 8×30 1 GPM/ft3 12×40 1 GPM/ft3
Figure 1. Dechlorination with GAC
2.5
2.0
1.5
1.0
0.5
0.0
Free chlorine, mg/L
Accumulated volume, gal.
0 500 1000 1500 2000 2500
Influent, Cl2 mg/L Effluent, Cl2 mg/L
Figure 2. Dechlorination
Water Conditioning & Purification JUNE 2009
tested for dechlorination per NSF/ANSI 42
protocol is shown in Figure 2. The carbon
cartridge contained 20×50 mesh coconut
shell GAC. The flow rate was 0.5 GPM
with an EBCT time of 0.14 minutes.
Chloramine formation and
reactions
Using free chlorine to disinfect, however,
can cause problems. Free chlorine can
react with naturally occurring organics in
the water, like humic and fulvic acids, to
form total trihalomethanes (TTHMs) and
haloacetic acids (HAAs).
Trihalomethanes in water are generally
composed of chloroform and, to a
lesser extent, bromodichloromethane, dibromochloromethane
and bromoform. To minimize TTHM
and HAA formation, many municipalities have
switched to alternate disinfection methods, the most
common being monochloramine.
Chloramines are formed by adding ammonia to chlorinated
water. The reactions are:
HOCl + NH3 → NH2Cl + H2O (monochloramine)
HOCl + NH2Cl → NHCl2 + H2O (dichloramine)
HOCl + NHCl2 → NCl3 + H2O (trichloramine)
The chloramine formed is dependent upon water pH. At
pH less than 4.4 trichloramine is formed. Between pH 4.4 – 6.0,
dichloramine is formed. At pH above 7, monochloramine is the
most prevalent.
Since most municipalities have a pH greater than 7, monochloramine
is the only chlormaine to be concerned about. Monochloramine
may impact taste and odor, but to a lesser extent
than chlorine. It is toxic to tropical fish and may cause anemia in
patients being treated with kidney dialysis.
Removal by activated carbon, therefore, is becoming more
common. How monochloramine is removed by activated carbon
is summarized in these reactions.
GAC + NH2Cl + H2O → NH3 + H+ + Cl- + CO*
CO* + 2NH2Cl → N2 + H2O + 2H+ + 2Cl + C
CO* represents a surface oxide on the GAC
The preferred reaction is the second one because nitrogen
and chloride are the end products. With a new bed of traditional
GAC, the first reaction occurs to some degree with ammonia
being formed. Over time with traditional GAC, the second reaction
will occur.
GAC systems designed for free-chlorine removal may need to
be retrofitted for monochloramine removal. The reaction rate for
monochloramine removal is considerably slower than removing
free chlorine using traditional GAC.
At least two to four times more EBCT will be required for
monochloramine removal with traditional GAC. Regulatory
authorities and some standards may require 10 minutes EBCT
when removing monochloramine from water for kidney dialysis.
100
90
80
70
60
50
40
30
20
10
0
Percent reduction
Carbon contact elapsed time (minutes)
0 1 2 3 4 5 6 7 8 9 10
Competitive surface-enhanced
Spartan coconut surface-enhanced
Standard coconut AC
Figure 3.
Removal of monochloramine
Information on treating water for hemodialysis may be found in
ANSI/AAMI Standard RD 62:2006, “Water Treatment Equipment
for Hemodialysis Applications.”
Surface enhanced activated carbons
To compensate for poor performance of traditional GAC
for monochloramine removal, manufacturers have developed
surfaced-enhanced activated carbons. These activated carbons
have surface reaction sites enhanced during the manufacturing
process. They are superior for monochloramine removal compared
to traditional GAC. For surface-enhanced GAC, an EBCT of three
minutes will be sufficient to remove monochloramine from water.
A coconut shell-based, surface-enhanced GAC can be compared to
a bituminous coal-based, surface-enhanced
activated carbon (Table 2).
In addition to excellent monochloramine
removal with surface-enhanced coconut
shell-based GAC, its higher iodine
number means it has superior volatile
organic chemical (VOC) capacity. It also
has lower ash content and higher hardness,
resulting in less dust.
A quick bench-scale test is used to
evaluate how well different types of activated
carbons perform for monochloramine
removal. In a beaker containing 400 mL
water and four-ppm monochloramine,
0.2 grams of pulverized activated carbon
is added.
With constant stirring, reduction in
monochloramine is monitored over time. Different types of
surface-enhanced activated carbons can be compared with a
traditional activated carbon (Figure 3). The surface-enhanced,
coconut shell-based activated carbon proved superior.
Based upon field studies for surface enhanced GAC, a
minimum EBCT of three minutes is recommended. For traditional
GAC, a minimum EBCT of 10 minutes is recommended. Using the
recommended EBCT for each type of GAC, the volume of GAC
required for various flow rates may be compared (Table 3). Surfaceenhanced
GAC costs more, but based upon the lower volume
requirements, it is cost effective compared to traditional GAC.
About the author
 Robert Potwora is Technical Director for Carbon Resources, LLC. He
has 30 years experience in the activated carbon industry and is currently
Vice Chairman of the ASTM D28 Committee on Activated Carbon.
Potwora may be reached by phone at (760) 630-5724 or by email at
robert@carbonresources.com.
About the company
 Carbon Resources, based in Oceanside, CA, is a quality supplier of
activated carbon products and services that is backed by technical support
and individualized customer service. The Carbon Resources management
team has over 85 years of experience in the activated carbon industry and
offers an unmatched line of the most diverse activated carbon products
on the market. The Sabre-series®, Spartan-series® (the surface-enhanced
coconut shell-based activated carbon used in Table 2), Guardian Adsorberseries
® and newly introduced Sentry-series® activated carbon products
are widely recognized in the industry. For more information, please visit

Does monochloramine cause cancer?

from docstoc.com

23) Does monochloramine cause cancer?
EPA believes that water disinfected with monochloramine that meets regulatory
standards poses no known or anticipated adverse health effects, including cancer.
Most of the research on the cancer risk of monochloramine comes from animal
studies using mice and rats.1 SO DO THE STUDIES ON CHLORINE – THEY USED
THE SAME PROTOCAL. In fact, the Drinking Water Criteria Document for
Chloramine, published in 1994 which EPA authored and continues to cite for
justification for using chloramines was based upon studies of rats and mice.
EPA believes that available data support the use of monochloramine to protect
public health. Only in terms of reducing chlorine byproducts, where is the data on
the safety of chlormaine byproducts?
EPA’s regulatory standard for chloramines provides a wide margin of safety2 to offset
any uncertainties in risk assessments. These are speaking of standards for the
compound chloramines not the byproducts of NDMA, hydrazine, iodo acids or
DXAA.
Monochloramine use may reduce bladder cancer risk compared to chlorine use.
Several studies have shown lower rates of bladder cancer in communities served by
systems that use monochloramine as a secondary disinfectant compared to systems that
use chlorine.1
Compared to chlorine, water treated with monochloramine may contain higher
concentrations of unregulated disinfection byproducts but the cancer risk is unknown.3
EPA continues to support research3 on the safety of monochloramine use. EPA
sponsored studies have reported highly toxic byproducts associated with
monochloramine that have been found to be genotoxic, cytotoxic and
carcinogenic. EPA has classified two of these byproducts (NDMA and Hydrazine)
to be ‘probable human cancinogens”. EPA and WHO studies have determined
that monochloramine is the least effective alternative for bacteria and virus
deactivation.
Monochloramine use produces lower levels of regulated disinfection byproducts that
are linked to cancer.
Regulated disinfection byproducts are produced in lower amounts when
monochloramine is used.
Regulated disinfection byproducts serve as indicators4 of other types of byproducts
that may also be reduced as a result of using monochloramine.
Compared to chlorine, water treated with monochloramine may contain higher
concentrations of unregulated disinfection byproducts.3
Additional Supporting Information:
3. EPA is currently researching unregulated disinfectant byproducts that can form from monochloramine
use. Compared to chlorine, water treated with monochloramine may contain different unregulated
disinfection byproducts than chlorinated water. There are few studies on health effects of unregulated
disinfection byproducts. However, additional information on NDMA, an unregulated byproduct, can be
found at: http://www.epa.gov/tio/download/contaminantfocus/epa542f07006.pdf . Also see question 9 and
19. This page does not load.
02/24/2009 US EPA
25) Do chloramines cause breathing problems?
EPA believes that water disinfected with monochloramine that meets regulatory
standards has no known or anticipated adverse health effects, including breathing
problems.
Monochloramine does not enter the air easily and therefore would be difficult to
inhale. This statement completely ignores the fact that monochloramine speciates
into di and tri chloramines with the slightest change in pH and temperature.
PAWC chemist stated that all chloraminated water contains all three species of
chloramines. It is widely known that tri-chloramine is the culprit for respiratory
irritation. Tri chloramines is created when chloraminated water is heated and
vaporized as in heated pools or showers.
CDC’s investigation1 of reports of monochloramine-related breathing problems
associated with drinking water use was unable to draw any conclusions about
monochloramine use and health effects. See above
Breathing problems associated with trichloramine and indoor swimming pools have
been reported.2 In a study by Dr. Richard Bull to determine dermal affects of
chloramines on mice, Dr. Bull emerced mice in chloraminated water. One
hundred percent of his test mice died from inhalation of chloramines before he
could complete his testing. Special harnesses had to be made for the mice in
order to conduct the dermal study. Dr. Bull indicated that no such problem
occurred with chlorinated water.
Trichloramine3, a chemical related to monochloramine and often found in swimming
pools, has been linked to breathing problems.
Trichloramine forms in swimming pools when chlorine reacts with ammonia from
bodily fluids.
Breathing problems traceable to disinfected water are typically related to swimming
pool use.4
EPA continues to review research related to the use of disinfectants used in
swimming pools. The findings in this area are unanimous. Dr. David Reckhow
indicates that the respiratory issues associated with swimming pool chloramines
is analogous to chloraminated drinking water that is heated or where pH is similar
to that of swimming pool conditions. Where are the studies in progress???
People who believe their breathing problems are related to monochloramine should
consult with their doctors.
The causes of breathing problems are often difficult to determine.
People who have breathing problems should inform their doctors if they have spent
time in or around a swimming pool recently.
CDC’s investigation1 of reports of monochloramine-related breathing problems
associated with drinking water use was unable to draw any conclusions about
monochloramine and health effects. This is how they keep changing the subject of
the discussion. They acknowledge that tri-chloramine is caused by ammonia and
chlorine and a respiratory problem in swimming pools. Connecting the dots – trichloramine
is a respiratory irritant…tri-chloramine is created with temperature
and pH change in monochloramine…. Trichloramine is created in showers, spas,
dishwasher vapor, etc. ……Yet they say MONO chloramines does not pose
breathing related problems. this is not rocket science it is simple logic..it is not
the mono chloramines – it is the TRI chloramines…but the trichloramine is an
unintended and unavoidable result of monochloramine use in a treatment
system…and, by their own admission, has not been studied by EPA.
Additional Supporting Information:
1. CDC and EPA conducted a preliminary investigation of reports of monochloramine-related
respiratory problems associated with drinking water. The investigation consisted of a
questionnaire filled out by complainants. The information collected could be used to help design
future epidemiologic studies.
CDC’s trip report can be found at:
http://healthvermont.gov/enviro/water/documents/CDC_Chloramines_report_011608.pdf.
2. Reported breathing problems due to chloramines are primarily related to inhalation of
household chemicals (mixing ammonia and bleach cleaning products), indoor swimming pool
air, or industrial exposure. See question 1 for further information about different types of
chloramines.
3. Trichloramine formation does not usually occur under normal drinking water treatment
conditions. However, if the pH is lowered below 4.4 or the chlorine to ammonia-nitrogen ratio
becomes greater than 7.6:1, then trichloramine can form. Trichloramine formation can occur at a
pH between 7 and 8 if the chloramine to ammonia-nitrogen ratio is increased to 15:1. Source:
Optimizing Chloramine Treatment, 2nd Edition, AwwaRF, 2004. It may not occur in the
treatment process but it does occur in the water use. They will only talk about
the conditions of treatment and the water quality as it leaves the plant…..not the
end point use.
4. Improper pool maintenance can often lead to trichloramine formation: Some examples
include: http://www.cdc.gov/niosh/hhe/reports/pdfs/2007-0163-3062.pdf and
http://www.cdc.gov/mmwR/PDF/wk/mm5636.pdf

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  • Ease of maintenance: self-cleaning system doesn’t require acid washing as a normal maintenance task
  • Adaptability: convertible between mixed oxidant and hypochlorite chemistries with minimal changes
  • Expandability: modular cell packs allow for expansion of chlorine capacity without increasing equipment footprint

Applications:

  • Final disinfection for water and wastewater
  • Biofilm removal for better chlorine residual in distribution systems
  • Disinfection-by-product (TTHM and HAA5) reduction
  • Chemical savings by microflocculation

MaximOS

Air Solubility in Water

Air Solubility in Water

Amount of air that can be dissolved in water – decrease with temperature – increase with pressure

The amount of air that can be dissolved in water increase with the system pressure and decrease with the temperature.

Deaeration

When fresh water is heated up, air bubbles start to form. The water can obviously not hold the dissolved air with increasing temperature. At 100 oC (212 oF) water starts to boil – the bubbles are formed by evaporated water or steam. If the water is cooled down at then again reheated, bubbles will not appear until the water starts to boil. The water is deaerated.

Solubility Ratio

The solubility of air in water can be expressed as a solubility ratio:

Sa = ma / mw         (1)

where

Sa = solubility ratio

ma = mass of air (lbm, kg)

mw = mass of water (lbm, kg)

Henry’s Law

Solution of air in water follows Henry’s Law – “the amount of air dissolved in a fluid is proportional with the pressure of the system” – and can be expressed as:

c =  pg / kH        (2)

where

c = solubility of dissolved gas

kH = proportionality constant depending on the nature of the gas and the solvent

pg = partial pressure of the gas

The solubility of oxygen in water is higher than the solubility of nitrogen. Air dissolved in water contains approximately 35.6% oxygen compared to 21% in air.

Solubility of Air in Water

Temperature (oF) Gauge Pressure (psig)
0 20 40 60 80 100
40 0.0258 0.0613 0.0967 0.1321 0.1676 0.2030
50 0.0223 0.0529 0.0836 0.1143 0.1449 0.1756
60 0.0197 0.0469 0.0742 0.1014 0.1296 0.1559
70 0.0177 0.0423 0.0669 0.0916 0.1162 0.1408
80 0.0161 0.0387 0.0614 0.0840 0.1067 0.1293
90 0.0147 0.0358 0.0589 0.0750 0.0990 0.1201
100 0.0136 0.0334 0.0536 0.0730 0.0928 0.1126
110 0.0126 0.0314 0.0501 0.0699 0.0877 0.1065
120 0.0117 0.0296 0.0475 0.0654 0.0833 0.1012
130 0.0107 0.0280 0.0452 0.0624 0.0796 0.0968
140 0.0098 0.0265 0.0432 0.0598 0.0765 0.0931
150 0.0089 0.0251 0.0413 0.0574 0.0736 0.0898
160 0.0079 0.0237 0.0395 0.0553 0.0711 0.0869
170 0.0068 0.0223 0.0378 0.0534 0.0689 0.0844
180 0.0055 0.0208 0.0361 0.0514 0.0667 0.0820
190 0.0041 0.0192 0.0344 0.0496 0.0647 0.0799
200 0.0024 0.0175 0.0326 0.0477 0.0628 0.0779
210 0.0004 0.0155 0.0306 0.0457 0.0607 0.0758

Example – Calculating Air Dissolved in Water

Air dissolved in water can be calculated with Henry’s law.

Henry Law’s Constants at a system temperature of 25oC (77oF)

  • Oxygen – O2 : 756.7 atm/(mol/litre)
  • Nitrogen – N2 : 1600 atm/(mol/litre)

Molar Weights

  • Oxygen – O2 : 31.9988 g/mol
  • Nitrogen – N2 : 28.0134 g/mol

Partial fraction in Air

  • Oxygen – O2 : ~ 0.21
  • Nitrogen – N2 : ~ 0.79

Oxygen dissolved in the Water at atmospheric pressure can be calculated as:

co = (1 atm) 0.21 / (756.7 atm/(mol/litre)) (31.9988 g/mol)

= 0.0089 g/litre

~ 0.0089 g/kg

Nitrogen dissolved in the Water at atmospheric pressure can be calculated as:

cn = (1 atm) 0.79 / (1600 atm/(mol/litre)) (28.0134 g/mol)

= 0.0138 g/litre

~ 0.0138 g/kg

Since air is the sum of Nitrogen and Oxygen:

ca = (0.0089 g/litre) + (0.0138 g/litre)

= 0.0227 g/litre

~ 0.023 g/kg

Calculating air dissolved in water for some other pressures at temperature 25oC (77oF) can be summarized to:

Pressure, abs (atm) 1 2 3 4 5 6
Dissolved Air in Water (25oC) (g/kg) 0.023 0.045 0.068 0.091 0.114 0.136

Dissolved Oxygen in Fresh Water

oxygen solubility in fresh water

Deariation

For maximum deaeration the water should be heated up to 212 oF (100 oC) at atmospheric pressure. This is common in steam systems where fresh water is supplied to the system through an heated deaeration tower on the top of the condensate receiver tank.

It is also common to install deaeration devices on the hot sides of heat exchangers in heating distribution systems to force the dissolved air out of the system.

Note! Since the maximum deaeration is limited by the minimum static pressure and maximum temperature in the system – the best deaeration result is achieved in positions at the hottest and highest levels of the systems – and/or at the suction side of pumps.