Technologies
Water Treatment and Equipment
Water treatment equipment turns the principles of recirculation and pond management into working systems. This page describes the main categories of equipment, what each does and what it demands in maintenance. It does not recommend brands or designs.
Mechanical filtration
Mechanical filters remove suspended solids before they decompose into ammonia and consume oxygen. Rotating drum filters with fine mesh screens are the standard in larger RAS; settling tanks, swirl separators and bead filters serve smaller systems. All require regular backwashing, and the backwash water forms part of the farm's waste stream.
Biological filtration
Biofilters provide surface area for nitrifying bacteria. Moving bed bioreactors use plastic media kept in constant motion by aeration; trickling filters pass water over stationary media exposed to air; fluidised sand filters offer very high surface area. Biofilter sizing depends on daily feed load, temperature and target ammonia levels.
Degassing and aeration
Carbon dioxide accumulates in recirculated water and lowers pH; degassing columns or aerated cascades strip it out. Aeration adds oxygen using blowers and diffusers, while oxygen cones and low-head oxygenators dissolve pure oxygen for high-density systems.
Disinfection and conditioning
Ultraviolet units and ozone generators reduce pathogen loads in recirculated or incoming water. Ozone must be used with care because residuals are toxic to fish. Foam fractionators remove fine particles and dissolved organics, particularly in saline systems. Heat exchangers and chillers maintain temperature. Alkalinity and pH are adjusted by dosing bicarbonate or lime.
Pumps and pipework
Pumps move water through the loop and are usually the largest consumers of electricity on a RAS. Low-head designs that move water with minimal lift save energy. Pipework should be sized to avoid excessive velocity and allow cleaning. Airlifts are an alternative in low-head systems.
Monitoring instruments
Dissolved oxygen probes, pH and temperature sensors, ammonia and nitrite test kits, salinity refractometers and flow meters give operators the information they need. Sensors drift and foul; calibration and cleaning schedules matter as much as the sensors themselves. The digital monitoring page covers how instruments connect to alarms and automation.