Lw. Sinton et al., INACTIVATION OF ENTEROCOCCI AND FECAL-COLIFORMS FROM SEWAGE AND MEATWORKS EFFLUENTS IN SEAWATER CHAMBERS, Applied and environmental microbiology, 60(6), 1994, pp. 2040-2048
Inactivation in sunlight of fecal coliforms (FC) and enterococci (Ent)
from sewage and meatworks effluents was measured in 300-liter effluen
t-seawater mixtures (2% vol/vol) held in open-topped chambers. Dark in
activation rates (k(D)s) were measured (from log-linear survival curve
s) in enclosed chambers and 6-liter pots. The k(D) for FC was 2 to 4 t
imes that for Ent, and inactivation was generally slower at lower temp
eratures. Sunlight inactivation was described in terms of shoulder siz
e (n) and the slope (k) of the log-linear portion of the survival curv
e as a function of global solar insolation and UV-B fluence. The n val
ues tended to be larger for Ent than for FC, and the k values for FC w
ere around twice those for Ent in both effluent-seawater mixtures. The
combined sunlight data showed a general inactivation rate (k) ranking
in effluent-seawater mixtures of meatworks FC > sewage FC > meatworks
Ent > sewage Ent. Describing 90% inactivation in terms of insolation
(S-90) gave far less seasonal variation than T-90 (time-dependent) val
ues. However, there were significant differences in inactivation rates
between experiments, indicating the contribution to inactivation of f
actors other than insolation. Inactivation rates under different long-
pass optical filters decreased with the increase in the spectral cutof
f wavelength (lambda(50)) of the filters and indicated little contribu
tion by UV-B to total inactivation. Most inactivation appeared to be c
aused by two main regions of the solar spectrum-between 318 and 340 nm
in the UV region and >400 nm in the visible region.