Salinity and pH effect on
the colloidal properties of suspended particles in super intensive
aquaculture systems
G. Ritvo, O. Dassa, M. Kochba-2003
Aquaculture, 218(1-4): 379-386
Abstract:
A large amount of feed and other organic material is
found as suspended matter in super intensive fish production tanks. Both
treatment and recycling of these organic materials depend on the size and
stability of the particles in suspension. The stability of suspended
material and the states of dispersion or flocculation were studied
extensively by colloid chemists. The effects of pH and electrolyte
concentration on colloidal stability of suspended particles collected in
super intensive hybrid tilapia (Oreochromis niloticus×Oreochromis
aureus) tanks, operated as an active suspension pond (ASP), were studied
here. Higher salinity led to better flocculation of the suspended matter.
The point of zero salt effect (PZSE) of the particles was found to be at a
pH range of 2.8–4.2, similar to the isoelectric point (IEP) range commonly
found in bacteria. Using multiple regression analysis, 92% of the colloidal
dispersion variation was attributed to changes in solution ionic strength;
addition of pH to model increased the model adjusted-R2
from 0.92 to 0.98. Our results suggest that in intensive fish production
tank, the lower the water salinity and the higher the pH, the more stable
would be the colloidal suspension.
(Department
of Agricultural Engineering, Technion, Israel Institute of Technology, Haifa
32000, Israel, e-mail:
gritvo@hotmail.com)