Chloramine Stability in the MWRA System
Massachusetts Water Resources Authority, 6/20/2001-11/30/2002
Consultant Partner: Black & Veatch
PI: Reckhow
Undergraduate Students: Alex Bonnar, Shem Stygar
Research Assistant: Chunshan Li
The purpose of this study was to assess the chlorine demand and chlorine decay kinetics, and DBP levels for two UV absorbance levels. Two source waters were studied. One collected at Cosgrove Intake (A) in early June 2001 when UV-254 is close to 0.060. Another sample was to be collected from the Quinapoxet and mixed with Quabbin water collected at Winsor Dam (B) to simulate a worst-case water. (This project began throught direct payment to Alex for the summer of 2001; then transitioned to a conventional contract with UMass through B&V). Prof. Irvine Wei at Northeastern conducted parallel studies focusing on ozone demand.
Proposal, Plans and Reports
- General Meeting Packets:
- Final Report:
Project Data
- MWRA Utility Information and related projects
- Project-specific background
- Northeastern ozone setup
- Model
- Experimental runs: 1/28/03, 4/1/03, exp2
- ?? lab notebook
Conference presentations based on this work
Theses/Dissertations based on this work
Additional Background: Wachusett reservoir water is a mixture of Wachusett tributaries and Quabbin water. Quabbin transfer tends to occur in June/July and can last up to March/April of next year. Wachusett tributaries have much higher TOC and UV absorbing organics (up to 0.1 to 0.2 Abs/cm at 254 mn). Quabbin water UV-254 is typically around 0.02 to 0.03 Abs/cm). It is not uncommon to see water at Cosgrove Intake reach UV readings of 0.08 to 0.10 Abs/cm when Quabbin transfer has ceased.
Research Program: This work was carried out by University of Massachusetts in Amherst and Northeastern University in Boston.
Ozone: Nominal ozone dose under summer max flow conditions can be 2.0 mg/L for 2-log inactivation of cryptosporidium. A range of 1.5 to 2.5 mg/L can be studied. Ozone generation for this study should be with oxygen to minimize the potential of forming nitrous oxides, which can then turn to nitrous and nitric acid. This is an experimental artifact that would not occur under Walnut Hill. Ozone contact time shall be between 40 and 60 minutes.
Free chlorine: Nominal free chlorine dose can vary from 0.5 to 1.0 mg/L. Contact time can be 4 hours, although a range of 5 to 240 minutes can be investigated. Current thinking is to add free chlorine after corrosion control (pH of 9), but a pH from 7 to 9 can be investigated.
Chloraimnation: Chioramine dose can vary from 1.5 to 2.5 mgIL and the preferred chlorine to ammonia-N ratio is 4.5 to 4.8 (5 is the theoretical stoichiometric ratio). To prevent the introduction of atmospheric gases that can impact pH, pre-treated water (ozonation, corrosion control, fluoridation, with or without free chlorine) will be partitioned into acid-washed chlorinedemand-free BOD bottles. These will be kept under constant temperature (15 or 20°C are acceptable) and remain headspace-free until the proper target contact time (daily up to 10 days will be acceptable). For other drinking water collaborations between UMass and MWRA click here.
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