The objectives of this project were to:
quantify the level of contamination of filters by various organisms (amoebae, aerobic spores, E.
coli, nematodes, etc.) through a survey performed on several production sites, with various resources and
associated water treatment works;
optimize filter washing to prevent or minimize health risks; and,
define cleaning protocols in order to allow operators to decontaminate filter media. Protocols have
been established from tests at laboratory and pilot scale before application on industrial sites.
The first part of the study focuses on a worldwide survey of more than 15 filters from water treatment plants (WTPs) in Europe
(France, Hungary, United Kingdom) to develop detailed information on filter contamination. The information
collected includes process design, water resource characterization, and contamination level of
filter media and filtered water quality with details on biological particles.
Results of this survey revealed a wide variety of organisms causing the contamination of the filters.
The mode of contamination of the filter beds (1st stage and 2nd stage filter) is primarily due to the
accumulation of biological particles coming from the resources, and secondarily a consequence of direct
development within the filters.
Backwashing applied under standard operating conditions (in terms of air, water flow rates and
frequency) efficiently removed organisms retained in the inter-granular space of the filter media
during the first two steps; however, backwashing does not efficiently release the organisms (particularly amoebae and
zooplankton) protected by the biofilm occurring on the media surface.
Regarding the media cleaning, the most appropriate reagents for obtaining elimination of
organisms, particularly amoebae fixed on a media, were chosen through batch tests with various
chemicals (salts, oxidants, acid, base). Salts and oxidants were found to be the most efficient
reagents for removal of organisms from the media. Includes 18 references, tables, figures.
| Edition : | Vol. - No. |
| File Size : | 1
file
, 820 KB |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 16 |
| Published : | 11/01/2008 |
