The Catskill and Delaware watersheds supply New York City with up to 90% of its daily water
demand of 1.2 billion gallons of water. Due to the high raw water quality of these unfiltered supplies
and an extensive watershed protection program, the New York City Department of Environmental
Protection (NYCDEP) has been granted a Filtration Avoidance Determination (FAD) by the US Environmental Protection Agency (USEPA). As
part of the FAD, NYCDEP must proceed with the design and installation of ultraviolet (UV) disinfection
facilities. The purpose of this paper is to review the selection of a lamp technology for the UV
facility and discuss the unique series of challenges that had to be addressed in the process.
The design of a UV disinfection facility for New York City's Catskill and Delaware supplies poses
several unique design challenges due to the scale of the facility (2,020 mgd), the properties of the
unfiltered surface water sources, gravity flow system, and the relative infancy of UV technology in
the U.S. drinking water industry, as regulations continue to evolve. A major challenge has been to
identify manufacturers capable of producing a UV system with a unit capacity of 40 mgd, a size that
has never been built before.
During the development of the UV facility design concept, both low pressure high output (LPHO)
and medium pressure (MP) systems were evaluated and deemed feasible for providing the
disinfection level needed to meet the anticipated regulations for inactivation of Cryptosporidium.
Considerable research and evaluation was conducted on the relative merits and drawbacks of the two
systems, including a series of meetings with potential manufacturers, canvassing of other users, and
site visits to large operating facilities. While no 40-mgd UV unit has ever been constructed, units
capable of treating about 20 mgd for microbial inactivation are now in service.
The paper details the primary features of LPHO and MP systems, outlines their primary advantages
and disadvantages, and presents how New York City arrived at the decision to proceed with the LPHO
lamp technology for its Catskill/Delaware UV disinfection facility. Includes tables, figures.
| Edition : | Vol. - No. |
| File Size : | 1
file
, 430 KB |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 18 |
| Published : | 06/17/2004 |
