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<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>Posted on our sludge listserve....<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
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<p class=MsoNormal><font size=2 color=black face=Arial><span style='font-size:
10.0pt;font-family:Arial'>Sue Dayton</span></font><o:p></o:p></p>
<p class=MsoNormal><font size=2 color=black face=Arial><span style='font-size:
10.0pt;font-family:Arial'>Blue Ridge Environmental Defense League</span></font><o:p></o:p></p>
<p class=MsoNormal><st1:State w:st="on"><st1:place w:st="on"><font size=2
color=black face=Arial><span style='font-size:10.0pt;font-family:Arial'>North
Carolina</span></font></st1:place></st1:State><font size=2 face=Arial><span
style='font-size:10.0pt;font-family:Arial'> Healthy Communities Program</span></font><o:p></o:p></p>
<p class=MsoNormal><st1:place w:st="on"><font size=2 color=black face=Arial><span
style='font-size:10.0pt;font-family:Arial'>PO</span></font></st1:place><font
size=2 face=Arial><span style='font-size:10.0pt;font-family:Arial'> <st1:address
w:st="on"><st1:Street w:st="on">BOX</st1:Street> 44</st1:address></span></font><o:p></o:p></p>
<p class=MsoNormal><st1:place w:st="on"><st1:City w:st="on"><font size=2
color=black face=Arial><span style='font-size:10.0pt;font-family:Arial'>Saxapahaw</span></font></st1:City><font
size=2 face=Arial><span style='font-size:10.0pt;font-family:Arial'>, <st1:State
w:st="on">NC</st1:State> <st1:PostalCode w:st="on">27340</st1:PostalCode></span></font></st1:place><o:p></o:p></p>
<p class=MsoNormal><font size=2 color=black face=Arial><span style='font-size:
10.0pt;font-family:Arial'>(336) 525-2003</span></font><o:p></o:p></p>
<p class=MsoNormal><font size=2 color=black face=Arial><span style='font-size:
10.0pt;font-family:Arial'><a href="mailto:sdayton@swcp.com">sdayton@swcp.com</a></span></font><o:p></o:p></p>
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style='font-size:12.0pt'> <o:p></o:p></span></font></p>
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style='font-size:12.0pt'> <o:p></o:p></span></font></p>
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style='font-size:12.0pt'> <o:p></o:p></span></font></p>
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<p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'><em><i><font
size=2 color=black face="Palatino Linotype"><span style='font-size:10.0pt;
font-family:"Palatino Linotype"'>Our lives begin to end the day we become
silent about things that matter. - Martin Luther King Jr.<o:p></o:p></span></font></i></em></p>
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size=3 color=black face=Arial><span style='font-size:12.0pt;font-family:Arial'><o:p> </o:p></span></font></p>
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style='font-size:12.0pt'> <o:p></o:p></span></font></p>
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style='font-size:12.0pt'> </span><o:p></o:p></font></p>
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<p class=MsoNormal><b><font size=2 color=black face=Tahoma><span
style='font-size:10.0pt;font-family:Tahoma;color:windowtext;font-weight:bold'>From:</span></font></b><font
size=2 color=black face=Tahoma><span style='font-size:10.0pt;font-family:Tahoma;
color:windowtext'> sludge-bounces@lists.ibiblio.org
[mailto:sludge-bounces@lists.ibiblio.org] <b><span style='font-weight:bold'>On
Behalf Of </span></b>Jeffrey G. White<br>
<b><span style='font-weight:bold'>Sent:</span></b> Friday, February 05, 2010
10:52 AM<br>
<b><span style='font-weight:bold'>To:</span></b> Sludge<br>
<b><span style='font-weight:bold'>Subject:</span></b> [Sludge] Study: Impact of
Silver Nanoparticle Effects at ThresholdLevels</span></font><font color=black><span
style='color:windowtext'><o:p></o:p></span></font></p>
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<p class=MsoNormal><font size=3 color=black face="Times New Roman"><span
style='font-size:12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 color=black face=Helvetica><span
style='font-size:12.0pt;font-family:Helvetica'><a
href="http://www.werf.org/AM/Template.cfm?Section=Home&CONTENTID=13156&TEMPLATE=/CM/HTMLDisplay.cfm">http://www.werf.org/AM/Template.cfm?Section=Home&CONTENTID=13156&TEMPLATE=/CM/HTMLDisplay.cfm</a><br>
<br>
<o:p></o:p></span></font></p>
<h1><b><font size=6 color=black face=Helvetica><span style='font-size:24.0pt;
font-family:Helvetica'>Impact of Silver Nanoparticle Effects at Threshold Levels<o:p></o:p></span></font></b></h1>
<p><font size=3 color=black face=Helvetica><span style='font-size:12.0pt;
font-family:Helvetica'>Silver nanoparticles (AgNPs) are a frequently used
nanomaterial with a wide range of industrial and consumer applications,
including fiber coating, detergents, and hydrogels and plastics to prevent
bacterial and fungal growth. Nanoparticles released from various
nanotechnology-enhanced consumer products will inevitably enter our sewers and
wastewater treatment plants (WWTPs). What effects, if any, they have on
treatment processes is the subject of an ongoing WERF research project, <em><i><font
face=Helvetica><span style='font-family:Helvetica'>Impact of Silver Nanoparticles
on Wastewater Treatment</span></font></i></em> (U3R07).<o:p></o:p></span></font></p>
<p><font size=3 color=black face=Helvetica><span style='font-size:12.0pt;
font-family:Helvetica'>Researchers from the <st1:place w:st="on"><st1:PlaceType
w:st="on">University</st1:PlaceType> of <st1:PlaceName w:st="on">Missouri</st1:PlaceName></st1:place>
are evaluating how silver nanoparticles will affect bacterial growth during
wastewater treatment. The team, led by Dr. Zhiqiang Hu, assistant professor of
civil and environmental engineering, has set up several lab-scale wastewater
treatment modular units using activated sludge processes designed to remove
organic matter and nutrients in wastewater. After a prolonged period of
operation (>300 days), the researchers took the activated sludge samples for
nanotoxicity testing.<o:p></o:p></span></font></p>
<p><font size=3 color=black face=Helvetica><span style='font-size:12.0pt;
font-family:Helvetica'>Results to date demonstrate that nitrifying bacteria are
especially susceptible to inhibition by silver nanoparticles. Researchers found
that at a concentration of 0.4 mg/L total Ag, a mixture of positively charged
silver ions and AgNPs inhibited the growth of nitrifying bacteria by 11.5
percent. In an experiment on shock loading of 100% AgNPs (lasting for 12
hours), researchers detected a peak concentration of 0.75 mg/L total Ag in the activated
sludge basin, and about 50% nitrifying bacterial growth inhibition (or
nitrification inhibition) accompanied with a slight accumulation of nitrite
concentration in wastewater effluent was observed.<o:p></o:p></span></font></p>
<p><font size=3 color=black face=Helvetica><span style='font-size:12.0pt;
font-family:Helvetica'>The results suggest the accumulation of silver could
have a detrimental effect on wastewater treatment, if the concentration reaches
threshold levels. Preliminary results from parallel studies of anaerobic
digestion, a commonly used solid stabilization process in wastewater treatment
plants, indicate that AgNPs at concentrations of 19 mg/L (19,000 ppb) or above
in biomass started to inhibit anaerobic microbial activities. Because most of
the silver particles are in the activated sludge or biosolids, the researchers
will continue to examine the impact of these nanoparticles on anaerobic
digestion.<o:p></o:p></span></font></p>
<p><font size=3 color=black face=Helvetica><span style='font-size:12.0pt;
font-family:Helvetica'>The U.S. Environmental Protection Agency has instituted
a secondary drinking water standard for silver of 100 ppb. Though typical
silver effluent concentrations from sewage plants are low (at ppb levels or
below), increased use of nanosilver products poses new threats to sensitive
water bodies. U.S. EPA has set water quality criteria values for silver in salt
and fresh water at 1.9 and 3.2 ppb, respectively. The research team will
provide a summary that identifies threshold levels of silver nanoparticles in
various treatment processes. Awareness of these threshold levels will directly
benefit wastewater treatment operators and state regulatory officials in making
informed decisions with regard to silver nanoparticles in wastewater treatment
plants.<o:p></o:p></span></font></p>
<p><font size=3 color=black face=Helvetica><span style='font-size:12.0pt;
font-family:Helvetica'>Look for the final published report <em><i><font
face=Helvetica><span style='font-family:Helvetica'>Impact of Silver
Nanoparticles on Wastewater Treatment</span></font></i></em> (U3R07) in May
2010.<o:p></o:p></span></font></p>
<h5><b><font size=2 color=black face=Helvetica><span style='font-size:10.0pt;
font-family:Helvetica'>February 4, 2010<o:p></o:p></span></font></b></h5>
<p class=MsoNormal><font size=3 color=black face="Times New Roman"><span
style='font-size:12.0pt'><br>
<br>
<o:p></o:p></span></font></p>
<pre><font size=2 color=black face="Courier New"><span style='font-size:10.0pt'>-- <o:p></o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'>Jeffrey G. White, Ph.D.<o:p></o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'>Associate Professor<o:p></o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'>Dept. of Soil Science<o:p></o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'>3207 Williams Hall<o:p></o:p></span></font></pre><pre><st1:place
w:st="on"><st1:PlaceName w:st="on"><font size=2 color=black face="Courier New"><span
style='font-size:10.0pt'>North Carolina</span></font></st1:PlaceName> <st1:PlaceType
w:st="on">State</st1:PlaceType> <st1:PlaceType w:st="on">University</st1:PlaceType></st1:place><o:p></o:p></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'>Campus <st1:address
w:st="on"><st1:Street w:st="on">Box</st1:Street> 7619</st1:address><o:p></o:p></span></font></pre><pre><st1:place
w:st="on"><st1:City w:st="on"><font size=2 color=black face="Courier New"><span
style='font-size:10.0pt'>Raleigh</span></font></st1:City>, <st1:State w:st="on">NC</st1:State> <st1:PostalCode
w:st="on">27695-7619</st1:PostalCode></st1:place><o:p></o:p></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'>Tel: 919-515-2389 Fax: 919-515-2167<o:p></o:p></span></font></pre><pre><font
size=2 color=black face="Courier New"><span style='font-size:10.0pt'>email: <a
href="mailto:jeff_white@ncsu.edu">jeff_white@ncsu.edu</a><o:p></o:p></span></font></pre></div>
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