Efficacy of a Closed Water Depuration System with Charcoal filter on the Bacteriological quality of Villorita cyprinoides var. cochinensis (Hanley, 1866)
Efficacy of a Closed Water Depuration System with Charcoal filter on the Bacteriological quality of Villorita cyprinoides var. cochinensis (Hanley, 1866)
Date
2021
Authors
Antony, Ally C.
Silvester, Reshma
Aneesa, P. A
Francis, Bini
Abdulla, Mohamed Hatha
Journal Title
Journal ISSN
Volume Title
Publisher
Society of Fisheries Technologists (India)Cochin
Abstract
Bivalves are good bio-indicators of the sanitary
quality of the aquatic bodies in which they survive.
The sanitary quality of the shellfish harvesting areas
is assessed based on the faecal coliforms/E. coli levels
of the harvesting water/shellfish tissue; on exceeding
the regulatory limits depuration suggested. In
the present study, the efficacy of a closed water
depuration system attached with a charcoal filter to
depurate Indian black clams (Villorita cyprinoides var.
cochinensis (Hanley, 1866) was evaluated. The depuration
system consisted of a closed water holding
glass tank, with a wall-hung immersion water pump
which re-circulated (18 l min-1) the seawater [salinity
– 10 ppt, pH -7.3, ambient temperature (29-30°C)]
through a coconut shell based activated carbon
(charcoal) filter. Clams were sampled at time
intervals of 0, 6, 12, 24, 72, and 96 h to assess the
reduction of total coliforms (TC), faecal coliforms
(FC) and faecal streptococci (FS). Initial TC, FC, FS
and Salmonella loads were assessed using standard
microbiological methods. Salmonella was not detected
in any of the clam samples. Complete removal
of both FC and FS whose initial loads were 4.6 x
104 MPN 100 g-1 and 1.1 × 105 MPN 100 g-1
respectively was observed within 48 h. Maximum
rate of depuration of TC, FC as well as FS were
observed during the initial first 6 h. However, TC
could not be fully depurated even after 96 h of
depuration. The differences in the depuration rates
of TC, FC and FS were found to be statisticallysignificant (p<0.05). The FC load of the black clams
selected for the study conformed only to the class
C shellfish growing area of EU which could be
reduced to acceptable regulatory limits of <230MPN
100 g-1 of depurated shellfish; which proved the
system used is efficient. The system uses simple,
cost-effective, easily available, natural, and renewable
water treating agent such as coconut shellbased
activated carbon and is suitable for household
purposes. In India, black clams do not have much
export value and is also not preferred to be eaten
raw. Hence less stringent, cost-effective, and simple
depuration measures as mentioned above may be
sufficient enough to meet the required sanitary
quality as it is consumed only after proper cooking.
Description
Keywords
Shellfish; Villorita cyprinoides; Depuration; Faecal coliforms; Activated carbon; Cochin estuary
Citation
Fishery Technology 58(3):160 -165