Integrated management of hydroponic wastewater for complete water recycle and cyanobacteria cultivation using an electric conductivity-based tool

Abstract

This work presents an integrated management process for hydroponic wastewater (HWW) reuse, by developing an electric conductivity-based tool that calculates recycled nutrient solutions' enrichment requirements and indicates their proper treatment. Treatment includes advanced methods and Synechococcus elongatus PCC 7942 (S7942) cyanobacteria cultivation for the removal/recovery and utilization of nutrients contained in HWW. The results showed that HWW can be utilized as substrate for S7942 cultivation. Increasing initial substrate nitrate‑nitrogen concentration from 389 ± 3 mg L−1 to 2132 ± 17 mg L−1 increases nitrogen assimilation from 0.131 mgNO3-N mgVSS−1 to 0.163 mgNO3-N mgVSS−1. Similarly, increasing initial substrate phosphate-phosphorous concentration from 8.4 ± 0.2 mg L−1 to 138.2 ± 5.0 mg L−1 increases phosphorous assimilation from 0.022 mgPO4 mgVSS−1 to 0.133 mgPO4 mgVSS−1. The advanced ion exchange treatment had efficiency >98 %. Adsorption with activated carbon and nanomaterials showed selective removal of nitrates, phosphates, calcium and magnesium. Sonication further increased nanomaterials' selectivity. © 2022 Elsevier Ltd