Structure and Design
2.5 Sump
The sump is the lowest point of the system and where water collects to be distributed as needed throughout the system. Water quality samples can be taken here and amendments can be made without overwhelming the fish or hydroponic components. While not a requirement, the addition of a sump prevents the water level from changing in either the fish tank or hydroponic component. In other cases where safeguards are put in place, the fish tank or hydroponic component can be used as the sump.
· Kentucky State University2.4 Plant Culture or Hydroponic Subsystem
The hydroponic portion of the system encompasses the majority of the facility footprint. Three primary designs are used: media beds, deep water culture (DWC), and NFT. Media-based systems: The design of media-based systems, sometimes called flood-and- drain, is fairly straight forward. A container filled with substrate is periodically flooded with water from the fish tank. Water then drains back to the sump (or fish tank) drawing oxygen into the substrate for plant roots and nitrifying bacteria.
· Kentucky State University2.3 Biological Filtration
Biological filtration refers to the breakdown of ammonia (NH~3~ and NH~4~+) into nitrite (NO~2~) and then further into nitrate (NO~3~) by naturally occurring, nitrifying bacteria. These bacteria live on the surface area of media contained in a tank collectively called the biofilter. The process of converting ammonia to nitrate will be detailed in the section on water quality. In RAS, the biofilter is designed to operate at low pressure. There is a dedicated tank filled with substrate like Kaldnes media, granular media, plastic balls, or other inert materials that have a large specific surface area or surface area of the media per unit volume.
· Kentucky State University2.2 Solids Filtration
Effective solids filtration is a key component to a well-functioning system and potentially the most important aspect as it influences the efficiency of all other processes. Solids are mostly produced from uneaten feed, fish waste, and bacteria biofilms (classified as suspended solids) (Timmons and Ebeling 2013). If waste is not removed, it can settle on plant roots (preventing uptake of nutrients), collect in areas of low water flow (resulting in poor water quality), cause the build-up of noxious gas, and clog pipes (preventing sufficient water flow) (Somerville et al.
· Kentucky State University2.1 Fish Culture
Fish tanks for aquaponics come in a wide range of shapes, sizes, and materials, with selection being largely based on culture species. The majority of large systems use round tanks that either have a flat- or cone-bottom. Use of tangential flow will prevent dead zones when used in round tanks (Figure 2). Cone-bottom tanks allow solids to concentrate at the bottom (in the cone) and be easily flushed from the system.
· Kentucky State University