Pilot- and bench-scale testing of faecal indicator bacteria survival in marine beach sand near point sources.
OBJECTIVE
Factors affecting faecal indicator bacteria (FIB) and pathogen survival/persistence in sand remain largely unstudied. This work elucidates how biological and physical factors affect die-off in beach sand following sewage spills.


RESULTS
Solar disinfection with mechanical mixing was pilot-tested as a disinfection procedure after a large sewage spill in Los Angeles. Effects of solar exposure, mechanical mixing, predation and/or competition, season, and moisture were tested at bench scale. First-order decay constants for Escherichia coli ranged between -0.23 and -1.02 per day, and for enterococci between -0.5 and -1.0 per day. Desiccation was a dominant factor for E. coli but not enterococci inactivation. Effects of season were investigated through a comparison of experimental results from winter, spring, and fall.


CONCLUSIONS
Moisture was the dominant factor controlling E. coli inactivation kinetics. Initial microbial community and sand temperature were also important factors. Mechanical mixing, common in beach grooming, did not consistently reduce bacterial levels.


CONCLUSIONS
Inactivation rates are mainly dependent on moisture and high sand temperature. Chlorination was an effective disinfection treatment in sand microcosms inoculated with raw influent.
Mika
K B
KB
UCLA Civil and Environmental Engineering, Los Angeles, CA 90095-1593, USA.
Imamura
G
G
Chang
C
C
Conway
V
V
Fernandez
G
G
Griffith
J F
JF
Kampalath
R A
RA
Lee
C M
CM
Lin
C-C
CC
Moreno
R
R
Thompson
S
S
Whitman
R L
RL
Jay
J A
JA
D015169:Colony Count, Microbial; D004203:Disinfection / Q000379:methods*; D004784:Environmental Monitoring; D004926:Escherichia coli / Q000254:growth & development* / Q000302:isolation & purification; D019015:Geologic Sediments / Q000382:microbiology*; D012621:Seasons; D012623:Seawater; D012722:Sewage / Q000382:microbiology*; D012822:Silicon Dioxide; D013472:Sunlight; D013696:Temperature; D014481:United States; D014867:Water
D012722:Sewage; D014867:Water; D012822:Silicon Dioxide