Skip to main content

DESIGN OF A HIGH-RATE WET WEATHER TREATMENT FACILITY IN NASHUA, NEW HAMPSHIRE

Buy Article:

$9.50 plus tax (Refund Policy)

Or sign up for a free trial

This paper presents the design of a wet weather flow treatment facility (WWFTF) in Nashua, New Hampshire. This facility, which will employ a ballasted flocculation technology, is the centerpiece of Nashua's innovative, cost-saving, and environmentally responsible wet weather pollution control program. Nashua's CSO control plan, currently being implemented under an Administrative Order issued in 2003, represents an improvement over the previous sewer separation plan because the plan will result in greater water quality benefits by reducing annual bacterial loading to the rivers from CSOs without increasing stormwater discharges. Furthermore, the current plan will be implemented in less than half the time it would take to separate all of the sewers in Nashua and as a result will achieve environmental benefits much more quickly. The current plan will maximize the use of existing infrastructure by maximizing system storage through the implementation of system optimization measures, an approach which is consistent with State and National CSO control policies. The estimated cost of the current CSO control plan is 50 million compared to nearly 250 million for complete sewer separation.

At the heart of the current plan is a high-rate WWFTF. With a sophisticated hydraulic model of the collection system, it was possible to demonstrate that Nashua's existing, large-diameter interceptors were capable of conveying wet weather flow in excess of the current Nashua Wastewater Treatment Facility (NWTF) capacity to the treatment plant site. By maximizing wet weather flow to the NWTF, discharge at several upstream CSOs will be eliminated in storms with recurrence intervals of between 1 and 2 years. Upstream CSOs that will continue to discharge in an average rainfall year following maximization of flow to the NWTF will be controlled using site-specific off-line storage or flow-through treatment technologies.

The high-rate WWFTF will be located at the existing NWTF site. In dry weather, the NWTF provides full secondary treatment for approximately 13 mgd, and can handle up to 38 mgd through the secondary process during wet weather events. Flow in excess of secondary treatment capacity currently receives primary treatment during wet weather, with primary effluent blended with secondary effluent prior to disinfection.

With a 60 mgd capacity, the high-rate WWFTF will enable up to 110 mgd of wet weather flow to be conveyed to the existing NWTF site. The first 50 mgd will continue to be treated by the primary and secondary treatment processes as described above. Once the capacity of the existing NWTF is exceeded, new pumps, screens, ballasted flocculation treatment units, and disinfection equipment will treat the excess wet weather flow. Following treatment, effluent from the high-rate WWFTF will be blended with existing primary and secondary treated flows, creating a “3- part” effluent blend that will be required to comply with the current 30 mg/l monthly average, 45 mg/l weekly average, and 50 mgyl maximum day BOD5 and TSS limits.
No Reference information available - sign in for access.
No Citation information available - sign in for access.
No Supplementary Data.
No Data/Media
No Metrics

Document Type: Research Article

Publication date: 2005-01-01

More about this publication?
  • Proceedings of the Water Environment Federation is an archive of papers published in the proceedings of the annual Water Environment Federation® Technical Exhibition and Conference (WEFTEC® ) and specialty conferences held since the year 2000. These proceedings are not peer reviewed.

    A subscription to the Proceedings of the Water Environment Federation includes access to most papers presented at the annual WEF Technical Exhibition and Conference (WEFTEC) and other conferences held since 2000. Subscription access begins 12 months after the event and is valid for 12 months from month of purchase. A subscription to the Proceedings of the Water Environment Federation is included in Water Environment Federation (WEF) membership.

    WEF Members: Sign in (right panel) with your IngentaConnect user name and password to receive complimentary access. Access begins 12 months after the conference or event
  • Subscribe to this Title
  • Membership Information
  • About WEF Proceedings
  • WEFTEC Conference Information
  • Learn about the many other WEF member benefits and join today
  • Ingenta Connect is not responsible for the content or availability of external websites
  • Access Key
  • Free content
  • Partial Free content
  • New content
  • Open access content
  • Partial Open access content
  • Subscribed content
  • Partial Subscribed content
  • Free trial content
Cookie Policy
X
Cookie Policy
Ingenta Connect website makes use of cookies so as to keep track of data that you have filled in. I am Happy with this Find out more