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Table 1 Compartments of the aquaponic system, their functions, targeted water parameters and expected reactions in each compartment

From: Environmental parameters and microbial community profiles as indication towards microbial activities and diversity in aquaponic system compartments

Compartment

Function

Targeted parameters

Expected reactions

Fish tank (aerobic loop)

Fish holding

Dissolved oxygen close to or at saturation, low total nitrogen, total organic carbon, NH4+ and NO2−

Nitrification, aerobic respiration

Drum filter (aerobic loop)

Removal of the solids via mechanical filtration

Low suspended solids after the filtration

None

Biofilter (aerobic loop)

Oxidation of total ammonia nitrogen and nitrite to nitrate

Dissolved oxygen close to or at saturation, low NH4+ and NO2−

Nitrification, aerobic respiration

UV treatment (aerobic loop)

Water disinfection

None

None

Oxygenation zone (aerobic loop)

Saturation of the system water with oxygen

Dissolved oxygen at saturation

None

Sump (aerobic loop)

The connection between aquaculture and hydroponic part of the system, serving as a hydraulic buffer

High oxygen saturation, high NO3− and low NH4+ and NO2−

Nitrification

Hydroponic table (aerobic loop)

Plant holding on a thin layer of water with floating polystyrene foam rafts

High oxygen concentration, high NO3−, low NH4+ and NO2−

Nitrification, plant nutrient uptake, carbon input by rhizodeposits, microbial respiration

Radial flow settler (aerobic and naerobic loop)

Passive filtration by using gravity to remove settable solids

Inflow: High concentration of suspended solids, total organic carbon and total nitrogen, higher NH4 compared to the outflow

Outflow: Reduced suspended solids and TN compared to the inflow

Nitrification, denitrification, ANAMMOX, microbial fermentation, mineralization

Anaerobic digester (anaerobic loop)

Anaerobic sludge digestion to obtain supernatant rich with nutrients and recycle the water

High nutrient concentration, no/low oxygen, low redox potential, high solids, accumulation of NH4

Denitrification, acidogenesis, hydrolysis, iron and sulfate reduction, sulfate oxidation, carbon mineralization, methanogenesis, dissimilatory nitrate reduction