The purpose of this document is to list all slow sand, surface water filtration facilities in New Hampshire. Slow sand filtration is an appropriate technology for meeting the filtration requirements of the US Environmental Protection Agency (EPA) surface water filtration rule.

A slow sand filtration facility typically has a minimum of two filter beds. The beds consist of uniformly fine sand, of approximate size 0.3 mm, supported on a gravel subbase with a network of under-drain collection pipes. The typical design loading rate is 0.05 gpm/ft2.

Operationally, a slow sand filtration plant requires less attention than other filtration technologies. Maintenance consists of removing solids from the top of the sand bed every few months. This removal is typically by hand. A few New Hampshire facilities clean the beds by harrowing and backwashing. These are shown with an asterisk. Other operational duties include testing for turbidity and bacteria, and disinfection using chlorine.

FOR MORE INFORMATION
For an overall listing of water supply related fact sheets, please request DES fact sheet WD-WSEB-15-2. For a list of full water filtration facilities in NH please see WD-WSEB-13-2. Please call the DES's Water Supply Engineering Bureau at 271-3139 for more information. Drinking water fact sheets are available through the DES web site at: www.des.state.nh.us/wseb then select fact sheets. We would appreciate your comments concerning this fact sheet.