Local ecological solutions
It is also possible to devise total ecological production methods for treatment of effluent water from intensive fish farming, not just by using it in more extensive forms of aquaculture such as polyculture. Such a system is shown above using integrated treatment systems for the water and local use of the sludge (Fig. 5.15).
The fish farm must employ water re-use technology to reduce the amount of outlet water. A micro-screen is used as the first step to remove the larger particles. Then the purified outlet water may be sent to a ground filtration unit or constructed wetland for further purification. The sludge produced by the microscreen can be sent to a locally installed liquid composting unit together with animal manure and eventually be used as fertilizer on nearby agricultural land, so avoiding long distance transport of the sludge. A solution with no effluent, either of nutrients, organic matter or micro-organisms is achieved in this way.