From: Elizabeth Klein

Sent: Thu Oct 12 09:58:03 2017

To: Gerald Fisher

Subject: Re: Definition of NTU

Importance: Normal

Thank you!

Elizabeth KleinCity CouncilCity of Molalla503-829-6855eklein@cityofmolalla.com


----- Original Message -----
From: Gerald Fisher <gfisher@cityofmolalla.com>
To: Jimmy Thompson (Mayor) <jthompson@cityofmolalla.com>, Elizabeth Klien (City Council) <eklein@cityofmolalla.com>, Leota Childress (City Council) <lchildress@cityofmolalla.com>, Glen Boreth (City Council) <gboreth@cityofmolalla.com>, Keith Swigart (City Council) <kswigart@cityofmolalla.com>, Delise Palumbo (City Council) <dpalumbo@cityofmolalla.com>, Cindy Dragowsky (City Council) <cdragowsky@cityofmolalla.com>
Cc: Dan Huff (Molalla) <dhuff@cityofmolalla.com>
Sent: Wed, 11 Oct 2017 21:18:11 -0700 (PDT)
Subject: Definition of NTU

All,



In answer to the question asked about NTU here is a good definition from
Hach which makes measurement equipment. See also Gerald's simple
definition at bottom.



NTU stands for Nephelometric Turbidity Unit and signifies that the
instrument is measuring scattered light from the sample at a 90-degree
angle from the incident light.

NTU is most often used when referencing the USEPA Method 180.1 or Standard
Methods For the Examination of Water and Wastewater.



Gerald's definition of NTU for wastewater - the cloudiness of the treated
effluent due to the number of particles suspended in the effluent. Needs
to be below 2.0 NTU to meet our permit for irrigation. See attached image
providing an example of levels of NTU.



Hope that helps, especially the image, to describe the level of treatment
this community is required to provide before discharging effluent water to
Coleman Ranch.



Regards,

Gerald Fisher, P.E. | Public Works Director

City of Molalla

117 N Molalla Ave. | PO Box 248 |Molalla, OR 97038

Office: <callto:503.829.6855> 503.829.6855 | Direct:
<callto:503.759.0218> 503.759.0218

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