Abstract
Fish canning industry wastewaters have high organic matter, oil and grease and salt (NaCl) content, which make difficult a proper treatment before discharge. In this work, their treatment was evaluated via activated sludge aerobic biological process through respirometric tests. Inhibition was found to be significant for NaCl concentrations higher than 17.5 g/L. On the other hand, the oil and grease content affects the wastewater biodegradability in the same way that the organic matter content expressed as chemical oxygen demand: the lower oil and grease and organic matter concentrations, the lower the percentage of wastewater biodegradability. As a final conclusion, the aerobic biological treatment process by activated sludge proved to be appropriate to treat fish canning industrial wastewaters, leading to high organic matter degradation rates (average value of 4900 mgO2/gCOD.d). Additionally, the experimental results achieved with the respirometric tests may be useful for the design of activated sludge plants to treat this type of wastewaters.
Highlights
There has been an increase in the number of fish canning industries across the world
In the subsections below we describe and discuss the results from the characterization of the fish canning wastewater samples, as well as the ones obtained from the respirometric tests
The fish canning wastewater characteristics vary according to the production process in a specific fish canning industry
Summary
There has been an increase in the number of fish canning industries across the world. The wastewaters produced in this type of industries vary widely, depending on the production period, on the type of fish and/or on the process used. Their treatment is complex due to their saline nature (they present high NaCl concentration) and due to the presence of oils and other organic compounds (Cristova~o et al, 2015). Conventional biological treatment processes, in particular activated sludge systems, are widely used in wastewater treatment plants (WWTPs). Toxic and inhibitory compounds such as volatile organic compounds (VOCs), salts, heavy metals, oils and greases, aromatic or chlorinated organics are usually found in industrial wastewaters and their negative impact on microorganisms' activity requires specific attention (Ricco et al, 2004). Toxicant effects are quite complex, not predictable, and could include biological sludge inhibition, decreasing the organic waste biodegradation and leading to the modification of the sludge settleability properties, which often decreases the solideliquid separation efficiency
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