Treatment of saline wastewaters from marine‐products processing factories by activated sludge reactor

Abstract

An activated sludge reactor, operated at room temperature (20–30° C) was used to treat saline wastewaters generated by marine‐products industries. The system was operated continuously and the influence of the organic loading rates (OLRs), varying from 250 to 1000 mg COD 1⁻¹ day⁻¹, on chemical oxygen demand (COD) removal was investigated. The system, inoculated with NaCl‐acclimated culture, removed up to 98% and 88% of the influent COD concentrations at OLRs of 250 and 1000 mg COD l⁻¹ day⁻¹, respectively. Since the organic pollution is essentially composed of proteins, microorganisms, which produced proteolytic enzymes, were isolated from the activated sludge culture. One bacterium with the highest protease activity, identified as Bacillus cereus, was chosen for protease production in fishery wastewaters of different concentrations containing combined heads and viscera powder. Protease synthesis was strongly enhanced when cells were cultivated in two times diluted fishery wastewaters. The enhancement of protease synthesis could have been due to the presence in effluent of organic matters or salts, which stimulated the growth of the strain and protease production.

Key words:

• Saline wastewaters
• biological treatment
• activated sludge
• continuous culture
• organic loading rate (OLR)
• protease