Food By-Product Valorization by Using Plant-Based Coagulants Combined with AOPs for Agro-Industrial Wastewater Treatment

Abstract

Re-using and adding value to by-products is one of the current focuses of the agri-food industry, following the Sustainable Development Goals of United Nations. In this work, the by-products of four plants, namely chestnut burr, acorn peel, olive leaf, and grape stem were used as coagulants to treat elderberry wastewater (EW), a problematic liquid effluent. EW pre-treatment using these natural coagulants showed promising results after pH and coagulant dosage optimization. However, the decrease in total organic carbon (TOC) was not significant, due to the addition of the plant-based natural coagulants which contain carbon content. After this pre-treatment, the photo-Fenton advanced oxidation process was selected, after preliminary assays, to improve the global performance of the EW treatment. Photo-Fenton was also optimized for the parameters of pH, H2O2, Fe2+, and irradiance power, and the best conditions were applied to the EW treatment. Under the best operational conditions defined in the parametric study, the combined results of coagulation–flocculation–decantation (CFD) and photo-Fenton for chestnut burr, acorn peel, olive leaf, and grape stem were, respectively, 90.2, 89.5, 91.5, and 88.7% for TOC removal; 88.7, 82.0, 90.2 and 93.1%, respectively, for turbidity removal; and finally, 40.6, 42.2, 45.3, and 39.1%, respectively, for TSS removal. As a final remark, it is possible to suggest that plant-based coagulants, combined with photo-Fenton, can be a promising strategy for EW treatment that simultaneously enables valorization by adding value back to food by-products.

Treatment of Winery Wastewater by Combined Almond Skin Coagulant and Sulfate Radicals: Assessment of HSO5− Activators

“…The SEM images (Figure 1b) show that the almond skin powder presents dark spaces that correspond to empty spaces, similar to findings in other works involving plant-based materials [38]. These porous materials allow the adsorption of the NaCl solution and the desorption of material from the powder to the exterior, a necessary characteristic to produce the ASE.…”

Removal of Methylene Blue from Aqueous Solution by Application of Plant-Based Coagulants

“…In Table 1, the plants sub species, part collected for this study and the herbarium number attributed by UTAD for the plant's identification are shown. All the plant-based coagulants were prepared in accordance with Martins et al [4].…”

Valorization of Cherry By-Products as Coagulant/Flocculants Combined with Bentonite Clay for Olive Mill Wastewater Treatment

“…As a result, the use of chemical coagulants has been reduced, and the search for greener and equally efficient options has increased [16,17]. Although the use of plants as natural coagulants for water treatment is an ancestral technique, it has only recently been widely studied as an alternative environmentally friendly procedure to the use of chemical-based coagulants [17][18][19]. Natural coagulants are biodegradable, non-toxic, non-corrosive, and cheaper than chemical coagulants [17].…”