Welcome to Water Talk! This is a place where we offer to share ideas, and exchange information. But most importantly, this is where to come for help. Questions pertaining to water treatment can be posted so that fellow operators and other water industry professionals may respond with their experiences and recommendations. We encourage all to participate and weigh in on the conversations. There’s a lot of expertise and experience out there that needs to be shared. 

Disclaimer: The information contained in this forum is provided for your review and convenience. Comments are opinions and are not intended to be a sole solution or provide legal advice with respect to any federal, state, or local regulation, nor are they endorsed by, or reflect the view or opinions of CTAWWA. You should consult with your appropriate authorities before undertaking any specific course of action or interpreting any regulations. Comments are moderated before being posted.

Water Talk

Coagulation and Flocculation

What is UV254 testing and how can I use test results to enhance my treatment process?


  1. Dave

    Apr. 6, 2016

    Something else to consider is an online, continuous monitoring UV analyzer, Chemtrac and Hach both make them. We use a Chemtrac at our plant to continuously monitor the raw water (plant influent) and our filtered water with one instrument. We use the readings as "another tool in the toolbox" to let us know what's in the reservoir water and how our treatment is doing.

  2. Sam

    Oct. 30, 2015

    UV254 measures the amount of UV light absorbed or transmitted through the water, providing an indication of the amount of natural organic matter (NOM) in the water. It is useful for determining the general level of organic matter in water during jar testing (to establish best treatment practices) and can become part of the daily testing to verify that treatment is on track. We use the Hach 6000 spectrophotometer and adjust coagulant(alum) based on these results.

    1. Stephen Olson

      Jan. 12, 2016

      Some additional information - you will need a spectrophotometer with a UV lamp to measure UV. You should filter your samples through a 1 micron glass fiber filter prior to testing. Typically, a UV measurement of 0.040 to 0.035 for filter effluent suggests good treatment for NOM removal and the control of DBPs.

Return to list




Leave a Reply

CTAWWA • 90 Sargent Drive • New Haven, CT 06511
Telephone: (860) 604-8996 • Fax: (860) 953-3051 • Email: info@ctawwa.org