In an effort to better control formation of disinfection byproducts (DBPs), the US
Environmental Protection Agency's recently promulgated Disinfectants/DBP Rule requires
that US surface water treatment plants whose influent and effluent waters meet certain
criteria practice enhanced coagulation. Although this treatment technique has been shown
to effectively reduce natural organic matter, and consequently DBPs, questions have been
raised concerning its effect on other aspects of water treatment such as particle and
pathogen removal. The current study was designed to investigate the influence of decreased
coagulation pH levels (an integral component of enhanced coagulation) on removal of
Cryptosporidium oocysts as well as on reduction of total organic carbon (TOC), turbidity, and
particle counts. A series of pilot-plant trials was conducted in which commonly used
coagulants (ferric chloride, alum, and polyaluminum chloride) were used at various pH
levels to treat river water spiked with large numbers of Cryptosporidium oocysts. The results
showed that TOC removal is significantly enhanced by coagulation at lower pH levels and
that all three coagulants are effective in removing Cryptosporidium oocysts during
conventional treatment (mean removal = 4.3 log units). However, turbidity and particle
counts appear to be unreliable indicators of oocyst removal. Finally, the investigation
suggested that lowering coagulation pH does not interfere with removal of Cryptosporidium.
However, questions remain concerning the use of alum at pH 5.
Includes 22 references, table, figures.
| Edition : | Vol. 94 - No. 11 |
| File Size : | 1
file
, 380 KB |
| Note : | This product is unavailable in Ukraine, Russia, Belarus |
| Number of Pages : | 11 |
| Published : | 11/01/2002 |
