Maximizing nutrient recovery from aquaponics wastewater with autotrophic or heterotrophic management strategies

Aquaponics uses bacterial processes and plant nutrient uptake to recover nutrients from aquaculture wastewater. However, little is known about which wastewater management strategy is best suited for nutrient recovery. We compared four aquaponics water management strategies: pH 6 or pH 7 with autotrophic bacterial populations (pH 6, pH 7), and pH 6 or 7 with heterotrophic bacterial populations (pH6M, pH 7 M). The results indicated that nutrients recovered with greater efficiency in pH 6 and pH 6 M than in pH 7, with higher plant biomass and food quality. pH 6 displayed the highest nitrogen (N) use efficiency (NUE = 65.5 %) and the lowest N loss as gas (34.5 %), followed by pH 6 M, suggesting that lower pH in aquaponics could enhance NUE and reduce N loss. pH 6 M had the highest phosphorus (P) use efficiency (PUE = 65.0 %) suggesting that lower pH and heterotrophic bacterial populations facilitate P recovery from wastewater. Plant nutrient uptake was improved when heterotrophic bacterial populations were established in an environmental pH of 6.