Page 463 - Fundamentals of Water Treatment Unit Processes : Physical, Chemical, and Biological

418 Fundamentals of Water Treatment Unit Processes: Physical, Chemical, and Biological

5. Sand recovery. What is done with the sand after it GLOSSARY
is taken through the door? Recommend what
Air binding: The presence of gas bubbles in the sand bed,
should be done?
causing increased headloss and possible rupture of
6. Depth of sand bed. How many years will the sand
the schmutzdecke on their release.
bed last until the sand bed must be rebuilt?
Appurtenances: Accessories, such as meters.
7. Headwater. State the elevation of the headwater
2
above the bottom of the filter box? About how Atmosphere: Unit of pressure. 1 atm ¼ 14.7 lb=in. ¼
101.325 kPa ¼ 760 mmHg.
much operating headloss is available? Could
Attachment coefficient, a: Ratio of particles attaching to
there be more? Or should the headloss available
collector surface=particle striking collector surface.
be less?
Backfilling: Saturation of the sand bed by filling slowly from
8. Describe the water quality provided by the slow
the bottom upward, to displace air in the bed.
sand filter?
Biologically mature: See mature.
9. Describe other points that come to mind after your
Biologically mature: This term was used by Bellamy et al.
visit. For example, is there provision for overflow
(1984) to mean that the sand bed had developed sand
in case the operator does not scrape the filter bed
grain biofilms to its near-maximum extent. The
before overflow? Was there erosion of the sand
extent of biofilm development depends upon the
around the inflow? Were there multiple points of
influent nutrient concentration. See also mature.
inflow discharge?
Bleeding: Allowing faucets to drip in order to avoid freezing.
Breakthrough: Passage of contaminants through the sand
ACKNOWLEDGMENTS
bed.
This chapter drew, to a large extent, from Hendricks, D.W. cfu, colony forming unit: A measure of bacteria concentra-
(Ed.), Manual of Design for Slow Sand Filtration, a project of tion.
the Water Research Foundation (formerly Awwa Research Chlorine demand: The chlorine fed into the water that
Foundation) and American Water Works Association, Den- reacts with oxidizable impurities and may, therefore,
ver, Colorado, 1991. Coauthors of the manual were Joy M. not be available for disinfection, reported in units of
Barrett (director of training and technical services, Rural mg=L.
Community Assistance Partnership, RCAP); Jack Bryck Chlorine residual: The concentration of chlorine, in mg=L,
(Dayton & Knight, Ltd., Consulting Engineers, Vancouver, remaining in the water after the chlorine demand has
British Columbia, presently with Malcolm Pirnie Consulting been met.
Engineers), M. Robin Collins (University of New Hamp- Cholera: Waterborne disease caused by Vibrio cholerae.
shire), Brain A. Janonis (presently director of utilities, City Clean-bed headloss: Headloss amount due to sand bed and
of Fort Collins), and Gary S. Logsdon (retired from the gravel support prior to formation of schmutzdecke or
Environmental Protection Agency, Cincinnati, Ohio, and biofilm development within the sand bed.
later retired from Black and Veatch Consulting Engineers, Clearwell: A facility for the storage of treated water.
Cincinnati, Ohio). The project manager was Martin J. Allen Coliform: A gram-negative, nonsporing, facultative rod that
(WRF). ferments lactose with gas formation within 48 h at
The author gratefully acknowledges the permission from 358C (Prescott et al., 1993, p. G6). See also enteric
the Water Research Foundation for the use of figures and bacteria. The coliform group includes E. coli, Enter-
tables from the manual, which included Figures 13.1, 13.3 obacter aerogenes, and Klebsiella pneumoniae
through 13.5, 13.7 through 13.9, 13.11 through 13.13, 13.15, (p. 839).
and 13.22, and Tables 13.3, 13.5, and 13.6. Sherry Morrison, Coliform removal, coliform removal efficiency: The extent
senior administrative assistant, Publishing Group, American of retention of coliform bacteria by a filter (see also
Water Works Association, Denver, arranged for permission to Unger and Collins, 2008).
use these figures and tables. Constant head box: A device which controls flow rate to the
Jack Bryck, PE, presently senior associate, Malcolm Pirnie, filter(s) by maintaining a constant head of liquid over
Phoenix, formerly with Dayton & Knight, Ltd., gave permis- fixed orifices; used in pilot plant studies.
sion to use Figure 13.16 and 13.17b, i.e., each of which includes Control building: A facility that houses meters, valves,
his photograph. Brian Walker, formerly principal and owner, laboratory instruments, office, etc.
Dayton & Knight, West Vancouver, British Columbia, gave Cryptosporidium parvum: A pathogenic protozoan which
permission to use Figure 13.17a and b, each of which includes causes enteritis and=or severe diarrhea; the oocyst
his photograph. In addition Jack Lee, PEng, Vice President, is resistant to chlorine disinfection.
Operations, Dayton & Knight kindly gave permission to use CT: The product of residual disinfectant concentration (C)in
Figures13.13,13.14,13.16 through 13.18,13.20,13.21;Lee mg=L and the corresponding disinfectant contact
also gave permission to use Figure 14.16 which shows a dia- time (t) in min.
tomaceous earth pilot plant (photograph and cross-section Cumulative flow demand: The total volume of flow calcu-
drawing) at 100 Mile House, British Columbia, c. 1983. lated over a given time period; the cumulative flow