From: Gerald Fisher

Sent: Wed Oct 11 21:18:10 2017

To: Jimmy Thompson; Elizabeth Klien (City Council); Leota Childress; Glen Boreth; Keith Swigart (City Council); Delise Palumbo (City Council); Cindy Dragowsky (City Council)

Cc: Dan Huff

Subject: Definition of NTU

Importance: Normal

Attachments: 3 NTU samples.jpg;

Microsoft Exchange Server;converted from html;

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: 503.829.6855 | Direct: 503.759.0218

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