Evaluation of some methods for fish canning wastewater treatment

A fish canning facility processes 1900-2000 tons of mackerel and sardine an nually at a rate of 10-15 tons per day for a total of 200 days yr(-1). This factory generates an average of 20 m(3) of industrial wastewaters per day. The objective of our study, which was carried out on a bimonthly basis fro m December 1995 to November 1996, was to determine the overall pollutant lo ad associated with this effluent in relation to the applicable Egyptian Sta ndards and to propose methods for pollutant load reduction before dischargi ng it to the local sewer. The methods were to benefit through the recovery of wasted organic load and transform it into an environmentally safe residu e amenable for either immediate reuse or final disposal thereafter. Five ch emical coagulation/flocculation treatments were tried using ferric chloride , alum, lime, ferric chloride and lime, and alum and lime. The best method involved the use of FeCl3 and Ca(OH)(2) (0.4 g Fe L-1 and 0.2 g Ca L-1, res pectively) which reduced the average influent BOD5 from 989 to 204 mg L-1, the COD from 1324 to 320 mg L-1, TSS from 4485 to 206 mg L-1, total protein content from 812 to 66 mg L-1 and oil and grease from 320 to 66 mg L(-)1. The separated dried precipitate averaged 50 g L-1 which was found to contai n 40% by weight recovered protein and 20% recovered fat. The solid was idea l for on-site reprocessing as animal feed. As well, the final effluent, if not discharged to the area sewer, was safe for controlled use in some irrig ation applications or forestry projects at the desert area surrounding the factory.