Batch anaerobic treatment of tuna fish wastewater sludge: Temperature and moisture content effect

The anaerobic fermentation of tuna fish wastewater sludge (TFWS) using a carbohydrate source and an appropriate lactobacillus strain inoculum seems to be an excellent process to obtain a valuable commercial product that could be used as a feed supplement of high protein content in the animal industry.; The first phase of this research was performed to determine the minimum carbohydrate source required to obtain a preserved end product from TFWS. TFWS was mixed with 0, 5, 10, 15% sucrose (w/w) and inoculated with lactic acid bacteria and allowed to ferment at ambient temperature (27 ± 2°C) during 0, 2, 4, 7 and 9 days under microaerophilic conditions. The second phase of this research was accomplished at three moisture levels 65, 75 and 85% and two different temperatures (30, 40°C) in a batch scale completely mixed anaerobic digester with 16 L of working volume.; The results from the first phase revealed that 5% (w/w) sucrose content in the TFWS fermented during 7 days was enough to attain the desired conditions. The results from the second phase revealed that thermophilic conditions (40°C) tend to accelerate the fermentation process in a favorable way only when the low moisture content was utilized (65–75 ± 1% w/w).