WASTE MANAGEMENT

Future SEA is working with companies around the world to assist them in meeting a range of challenges. Fish farmers recognise they require a continuous supply of fresh, clean water for their own operations. In addition to meeting their requirements for clean water, fish farmers face increasing pressure to improve environmental performance. Concern for the environment world wide is creating enormous pressure to control waste discharges of all kinds, including those of fish farms. Public pressure is ultimately applied to fish farm operators through new laws and operational restrictions by governments. Working in co-operation with several clients, Future SEA has developed waste capture technology that is effective in both fresh water and salt water environments. The application of Future SEA's waste capture technology has enabled these clients to increase production in environmentally sensitive sites or to add new production sites.

Developing and refining waste management technology presents many difficulties. Firstly, there isn't a lot of waste produced by fish. Fish are very clean and efficient in their use of feed and the consequent production of waste. They produce the least amount of waste of all the animals we farm. For example, a fish's production of waste per kilogram of body weight produced is about one eighth of that produced by a cow. Secondly, there is a lot of water moving through a bag. The SEA System™ pumps the equivalent of a small city's effluent water through each bag to ensure that the rearing environment stays clean and the fish get all the oxygen they need. This combination of very low waste production and high volumes of water flow means that the solids content in the water is very, very low.

So how do we do it? We utilise some of the characteristics of the material and the flow within the bag to separate out the solid wastes. When fish eject a faecal pellet it is coated with a mucus sheath and is quite dense. With time, the mucus sheath and the pellet will turn to mush which is far more difficult to separate and remove. The trick is to get the pellets out of the bag before they turn to mush. The bag design is a key feature in getting the pellets separated from the water stream quickly. The SEA System™ bag sweeps faecal pellets into the trap in less than 10 minutes and provides a clean healthy environment for the fish, separating them from their wastes.

Once the pellets are in the patented Future SEA waste trap, this is where the magic begins. Energy that has been applied to pump the water is now used to separate the pellets from the water flow in the patented SEA System™ waste trap. This keeps energy costs low aided by using additional "free" energy in the form of gravity to settle out and concentrate the faecal material. The shape of the waste trap and related components is integrated so that the separation is effective and energy efficient. The exit stream discharged from the waste trap has, on occasion, been "cleaner" than the inlet stream entering the bag with a lower solids content. The waste trap removes some solids present in the incoming water, further reducing the environmental impact.

(above: sludge being pumped from waste concentrator)

For waste management technology to be practical it must also be cost effective. Reducing the volume of the waste reduces shipping and treatment costs. We are able to concentrate solids to an extent that makes transport and processing practical, depending on distances and local infrastructure. Future SEA has developed waste concentrator "silos" to concentrate and store the material extracted by the waste traps. After the initial prototypes were tested at our Nanaimo marine site, further development work of these "silos" was undertaken by Future SEA in conjunction with our client Aquatas Pty. of Margate, Tasmania. The prototype waste concentrators at Aquatas were designed to provide storage for a week's concentrated waste production from a single waste trap and bag. To empty the concentrators a boat with a sealed hold comes alongside and connects to the discharge pipe. Each concentrator is pumped out in turn until all eight concentrators have been emptied. The contents of the boat are pumped out at a nearby dock into a sewage pump truck, which carries away the "sludge" for treatment or composting. Farmers have demonstrated their willingness to use fish wastes for fertiliser in a number of different countries. The use of fish farming wastes as an effective fertiliser for a wide variety of agricultural crops has been well documented by the Aquacultural Engineering Society.

Another alternative that Future SEA is able to offer our clients is the ability to broadly disperse the bag discharge in preference to waste capture. Depending on the site, this may be a more practical and attractive alternative than waste capture. Every installation undertaken by Future SEA is custom engineered based on the client's requirements, so we can provide a solution that works for a specific site.

The current state of Future SEA's waste trap technology is such that it can be applied to both fresh water and salt-water applications. Aquatas' entire eight-bag system has been equipped with waste traps and concentrators. Future SEA waste traps are also in use in fresh water applications. There are some limitations in that waste trap technology is not applicable to all sizes of SEA System II™ bags. Future SEA waste trap technology has been developed with the support and assistance of Industry Canada, BC Science Council, the National Research Council of Canada, Fisheries and Oceans Canada and COFRI. Future SEA is continuing to refine and improve waste management technology for aquaculture.