loop. The pressure from the water column above will force the oxygen into the water. The advantage of the deep shaft is that pumping costs are low but the installation is troublesome and more expensive.
2. Water treatments a. Solids capture Solids capture methods Important methods for removing suspended solids are sedimentation, filtering and flotation. Suspended solids settle relatively easy because of their weight and the settlement can for instance take place in settling tanks with low water velocities that also stimulate settlement. Filtration can occur in sieves or spongy material. In flotation, particles are adsorbed by air bubbles due to the surface tension of the particles and they can be removed again when bubbles reach the water surface (foam fractionation). Sedimentation Sedimentation occurs as a result of gravity forcing particles heavier than water to “settle� to the floor. Since the wet density of solid wastes 3 from trout farming operations ranges averages 1.07 g/cm , settling chambers must provide for quiescent conditions for effective sedimentation at the end of raceways (Figure 14). In turbulent flow conditions, such light solids will be easily re-suspended in the water column and removal efficiency will be compromised.
Figure 14. Schematic diagram of a raceway (Drawing: V.I.Gunnarsson) Sludge traps are positioned at the bottom of the production units (Figure 15). 51