The aims of the research programme are to examine the waste outputs from land based fish farm operations from a variety of culture systems. The farms investigated are equipped with different forms of waste management systems, and a major part of the study is concerned with assessing the physical efficiency and cost efficiency of such installations. Through a detailed study of such operations, it will be possible to produce a working model of fish farm waste loadings, based on operational activity, species cultured, feed type, and water treatment system.
An examination was made of the waste output from land based fish farm operations from a variety of culture systems.
Waste loadings at Scottish sites:
With the exception of the dissolved phosphorus budgets, little difference in the waste output of the 2 years of production has been observed on the basis of unit mass of production. The results are broadly in line with those expected from salmonid facilities.
Waste loadings at Danish sites:
Preliminary net effluent loadings from the 3 Danish sites have been found to be, unlike the Scottish sites, highly variable involving large levels of variation in the suspended solid (SS) and total nitrogen budgets. The indication is that large quantities of allochthonous solid material pass into the fish farm site; as a consequence, the setting of budgets for solid bound material are unlikely to be accurate.
SS and biochemical oxygen demand loads are found to be greatly in excess of Danish loadings.
There a continuously changing waste output problem for fish farms to contend with and also a need for waste treatment systems employed to respond to a wide variation in the quality of that solid waste output. For the bulk of the working day, little impact can be made on reducing the concentration of the main waste parameters as they exist in dissolved form. Traditional methods of waste treatment can only have an inadvertent impact upon those dissolved wastes. Only at specific times can waste reduction at a meaningful level take place.
The comparatively poor water quality of the inlet waters in Denmark, coupled to the small contribution to effluent concentrations by fish farms demonstrates that to adequately monitor waste outputs, the method of regulation which Danish legislators have chosen, which also embraces feed use, has merit in such environments.
Both the contractor and subcontractor will be engaged in a 24 month water quality monitoring programme on land based aquaculture projects, which will reflect not only the diversity of species cultured, but also the technologies used to ameliorate waste loads produced by such farms. The project is split into two main pieces of work: an effluent loading study, a waste treatment study.
The two studies will be combined into the period of fieldwork. Each contractor will be monitoring at sites which produce the major economically important species cultured in their respective countries: juvenile Atlantic salmon (Salmo salar) and rainbow trout (Oncoryhnchus mykiss) in the UK, and eels (Anguilla anguilla) in Denmark. Studies will be performed in parallel, using similar sampling technologies and standardised laboratory procedures. Sampling at sites will be done on 24 hr cycles, at various times through the year, in order to examine the effect of the growing cycle and changing farm management practice throughout the period of observation. In this period, both the British and Danish collaborators will be involved in sampling programmes of approximately equal intensity and size: which will involve visits on site every 2-4 weeks. In between these visits, analysis of samples and farm production data will be continued. Waste parameters to be measured include suspended solids, biochemical oxygen deman , ammoniacal nitrogen, total oxidised nitrogen, total nitrogen, and dissolved reactive phosphorus, pH, temperature, and dissolved oxygen. Comparative measures of these parameters will be made between inflow water, and outflow waters, pre and post treatment, in order to collect data for both the waste loading and effluent treatment sections of the project. Waste loadings will also be evaluated in terms of farm management, through the use of biomass and feed records, together with periodic analysis of feed given to stocks.
During the last year of the study, an economic evaluation of the systems observed will be undertaken, in order not only to examine the suitability of systems examined to maintain quality of farm effluent at levels which fall within EC requirements, but also to identify whether or not such systems are cost effective in achieving this objective.
