The purpose of this document is to list all slow sand, surface water filtration facilities in New Hampshire. 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. 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. Please call the DES's Water Supply Engineering Bureau at 271-3139 for more information.