Abstract:
Commonly the food processing industry consumes a huge amount of water. Food industry
effluent characterizes high Biological Oxygen Demand (BOD), Chemical Oxygen
Demand (COD), Total Dissolved Solids (TDS), fats, nutrients, oil, and grease. Fish
processing wastewater mainly shows high TDS due to releasing of blood, small pieces of
fishes, and chemicals at the filtering, cooling, washing, cooking, pre-cooking, and
thawing steps. High TDS can be interference for wastewater treatment steps like
biological treatment and this situation, a cost-effective pre-treatment is suitable.
Adsorption theory has also been used in previous researches to remove TDS, and in this
research, the effect of contact time and adsorbent dose were investigated to remove TDS
from fish processing wastewater. A batch test was performed using limestone as an
adsorbent. Wastewater samples were kept at pH 7 using 0.1 N HNO3 and 0.1 N NaOH.
Using sieve shaker, >0.063 mm, >0.125 mm, >0.15 mm, >0.5 mm, > 1 mm, >2 mm
and >3.14 mm particle sizes were separated. As >1 mm particle recorded highest removal
efficiency as 83.85% (adsorption capacity 1297.5 mgg
-1
). >1 mm particle was used for
remaining experiments. When increasing contact time, the highest removal efficiency was
recorded at 5-hour contact time as 72.55%. When increasing adsorbent dose, the
maximum removal efficiency was recorded at 4 g L-1
as 79.64%. The results indicated
that the removal efficiency of TDS depends on the adsorbent dose and contact time.
Though, limestone is an alkaline material because of containing CaCO3 as a predominant
material, with no high increment of pH in the wastewater sample after adsorption.
Adsorption data also fitted with Langmuir Isotherm and according to results, this can be
indicated as favourable adsorption.
Keywords: Food processing industry wastewater, Limestone, TDS, Adsorption
