Modified slow sand filtration is being successfully applied throughout North America to treat raw
water that would not normally be considered suitable for slow sand filtration. This technology
involves the combination of one or more unit processes with slow sand filtration. These unit
processes may include pre-treatment ozonation, pre-treatment advanced oxidation, roughing
filtration, post-treatment limestone contact or post-treatment biologically-active carbon filtration.
The advantages of modified slow sand, including the relatively low operations and maintenance
requirements, are of benefit to many small systems applications.
The ability of modified slow sand filtration, and biological filtration in general, to deal with high
levels of natural organic matter (NOM) and emerging contaminants has been a topic of recent research. This paper
presents the results of analyses of several emerging contaminants from finished water produced
by operating conventional and modified slow sand filtration plants, along with pilot scale
research studies conducted in the US northeast and in Ontario, Canada. A summary of available
information on the removal of emerging contaminants and pathogens using biological processes
typical of slow sand filtration is also presented. The ability of biological filtration to effectively
treat a wide range of parameters, particularly the more exotic compounds, while retaining a
practical and sustainable operation for small systems is reviewed, with an emphasis on the
effective application of this technology. The pathogens examined include Aeromonas sp.,
Cryptosporidium parvum and Giardia lamblia. Indicator microorganisms such as Bacillus spores
and MS2 bacteriophage were also studied. Emerging contaminants included in these studies
consist of endocrine disrupting compounds such as bisphenol-A (BPA), pharmaceuticals and the
cyanobacterial toxin microcystin-LR. A brief discussion of the capacity of biological filtration to
reduce geosmin and 2-MIB with and without ozone application is also included. Includes 29 references, figure.
| Edition : | Vol. - No. |
| File Size : | 1
file
, 580 KB |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 42 |
| Published : | 06/01/2007 |
