Company ProfileCase Study: Fish Processing—Ilhavo, Portugal
The Problem
A cooperative formed by a number of fish processing companies in Portugal needed assistance with waste disposal. The companies were involved in a variety of ventures, including the dressing, drying, salting and freezing of fish and produce for the home market and for international export. They also canned shellfish and sardines, giving rise to oil and fats in the waste.
The cooperative asked EversTech to design a treatment system to handle all wash waters and fish waste, including offals and some melt water. The resultant mixed waste had a COD of over 40,000mg/l at times with an average of about 27,000mg/l COD and a salinity of 1-2%. The current disposal route, which was direct discharge to the local river, was to be stopped and the wastewater was not acceptable at the local sewage works because of its high salinity. Land filling of fish waste and offals was being stopped.The EversTech Solution
Led by EversTech’s Principal Consultant, a team of technicians completed a successful pilot trial of fish processing effluent. They also created a design for a central processing plant to service all of the cooperative's collective wastes. The value of the project was
6 million Euros.
The process was engineered to optimize treatment and thus maximize the production of by-products, using the principles of bio-augmentation to enhance resource recovery. Electricity generating capacity would be in the region of 3 Megawatts continuous (72 Mw/day) and heat recovered from electricity generation would be about 4 Megawatts continuous (96 Mw/day). This would be converted via an induction cooler into refrigerated water and recycled to the member factories for their de-freezing processes. Bio-solids or biomass, which would be high in Nitrogen or Single Cell Protein, would amount to about 20 tons/day.
The net benefit to the cooperative would be between 1.8 – 2.3 million Euros annually.Pilot Trial and Feasibility Study
The following results and treatment efficiency diagram demonstrates the highly successful treatment capability of the EversTech design utilizing bio-augmentation which results in the high quality of the by-products generated.
It was felt that though the system as designed would cope with high salt levels in the combined effluent, trials should be carried out with high salinity, until a fall off in efficiency occurred.
Oil and Grease
Oil and grease levels were satisfactorily controlled, and in excess of what would be expected to be contributed by the canning activities in the full scale. No deterioration of performance occurred in oil and grease digestion or in COD removal with the increased salinity.
Salinity Tests
Salination tests were carried out on the facultative and aerobic phases to gauge the system’s response to salinity levels of up to 2%. Since the anaerobic phase would not be subjected to the same higher salinity levels, the salination tests were not directly applied to the anaerobic digester, though there was obviously a carry through of salt from the liquor in which the macerated fish were suspended and homogenized.
However, the levels of salinity increased to 3% in the anaerobic digester incidentally, presumably from the macerated fish off-cuts and offals themselves. This high level of salt did not, however, affect the performance of the anaerobic digester, and the homogenous biomass showed full digestion, including all heads and bones. There was no fall off in gas production quantity or quality.