The trend in drinking water regulations is to increase the requirements for
pathogen inactivation while decreasing the concentration of disinfection
byproducts (DBPs). The new 80 mgd Lake Pleasant Water Treatment Plant
(WTP) takes an innovative approach to meeting future regulations and protecting
public health by using six barriers for removal/inactivation of pathogens as well
as six barriers for reducing DBP formation. This approach is similar to the
European approach of using processes that produce a low-organics, biologically stable
finished water. The treatment process consists of preoxidation with
chlorine dioxide, coagulation, ballasted flocculation and high-rate sedimentation,
ozonation, biological filtration, adsorption on granular activated carbon (GAC),
and disinfection with ultraviolet light (UV) and chlorine. While chlorine dioxide
is used primarily for preoxidation of iron and manganese, and ozone is used
primarily for taste-and-odor control, both will provide a disinfection barrier. The
high rate sedimentation process and the granular media filtration both will provide
a disinfection barrier by physically removing pathogens. The UV system will be
used for inactivation of Cryptosporidium and chlorine will be used for primary
disinfection of Giardia and viruses and for secondary disinfection. Also, the
integrated disinfection and other treatment processes create a multiple barrier to
reduce DBP formation. Coagulation, biological filtration, and GAC adsorption
will each remove DBP precursors, which will reduce the chlorinated DBPs. And
delaying chlorination until the very end of the treatment process will further
reduce chlorinated DBPs. Although chlorine dioxide and ozone have their own
DBPs, the chlorite from the chlorine dioxide will be removed with ferrous
chloride and bromate formation during ozonation will be controlled with low
ozone doses and with hydrogen peroxide. Includes reference, table, figure.
| Edition : | Vol. - No. |
| File Size : | 1
file |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 7 |
| Published : | 11/15/2004 |
