In January 2007, the town of Troy, New Hampshire completed a lagoon upgrade designed to meet ammonia nitrogen limits imposed in their reissued NPDES discharge permit. The plant was required to meet a summer limmit of 8.7 mg/l from May 1st through September 30th and a winter limit of 13.2 mg/l from October 1st through April 30th.
The Troy lagoons were originally constructed in 1983 and consisted of three aerated cells utilizing a combination of an older style fine bubble tubing aeration system and surface aerators. The original design flow was 0.265 MGD. The upgrade construction was started in the fall of 2006 and completed in January 2007. Due to the loss of flow from a major industrial contributor, the first lagoon was removed from service in an effort to decrease excessive detention times and conserve temperature. All influent flow was directed to cell #2. The process was converted to a LemTec™ (Lemna Environmental Technologies, Inc.) Biological Treatment System consisting of LemTec™ Modular Insulated Floating Covers (full cell coverage), and a diffused aeration system...Phase 2 of this project, if needed, would be to install a fixed film polishing reactor to further enhance nitrification and provide for a greater degree of reliability.
To continue reading the full article, click here: Improving Cold Temperature Nitrification Using Insulated Covers
Author Details: Wes Ripple, Operations Specialist, Wastewater Engineering Bureau, New Hampshire Department of Environmental Services (NHDES)
Originally Published In: The Collector: NH Water Pollution Control Association, April 2010 Issue