Assessing nitrogen recovery in poultryponics for hydroponic lettuce production using treated poultry processing...

Poultry processing wastewater (PPW) is a nutrient-rich effluent suitable for hydroponic irrigation. A nitrogen mass balance was developed for a pilot-scale poultryponics system comprising bioreactors (algal-bacteria consortium vs. bacteria only), clarifiers, filters, UV disinfection and hydroponic grow beds to assess N recovery and lettuce production on treated PPW. Lettuce cultivated on treated PPW showed 5 ± 1 % higher root biomass, 58 ± 10 % lower shoot growth, and nutrient deficiency (K, Mg, Ca, Cu) compared to mineral fertilizer treatments (p < 0.05). pH control (pH = 7.0) and nutrient supplementation (N, P, K and micronutrients) mitigated growth inhibition. Nitrogen was not limiting, as nitrogen utilization efficiency ranged from 3.7 %-6.3 %, with 65.4 %-83.0 % of input nitrogen (∼213 g N) remaining in effluents, indicating the potential for a larger plant production system. These findings highlight the importance of targeted nutrient supplementation to enhance lettuce growth on treated PPW, while balancing nitrogen supply with plant demands.