The agro-industry has increased over the years as a necessity to supply the needs of the population in regard to food and drink. This increase has led to the significant production of agro-industrial wastewaters characterized by a high content of organic matter, polyphenols, suspended solids, and turbidity, making these wastewaters dangerous if released into the environment without proper treatment. In this work, recent findings concerning the feasibility of coagulation–flocculation–decantation (CFD) and advanced oxidation processes (AOPs) for the treatment of agro-industrial wastewaters were collected and reviewed. More specifically, the mechanisms, limitations, operational conditions, and relevance of the different treatment processes for wastewater treatment and reuse are discussed. As a result, it was concluded that CFD processes and AOPs could be performed either separately or combined to achieve high efficiency in agro-industrial wastewater treatment.

Five different plant-based coagulants were used with the objective of removing methylene blue (MB) color aqueous solution. The plant-based coagulants were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM) and Brunauer–Emmett–Teller (BET) which showed that these materials had high porosity and could adsorb the contaminant MB from the aqueous solution. To increase the efficiency of the plant-based coagulants, bentonite was applied as a flocculant. Results showed MB removal of 90.9%, 91.9%, 91.4%, 86.9% and 88.9%, respectively, for seeds of Chelidonium majus L., Dactylis glomerata L., Festuca ampla Hack., Tanacetum vulgare L. and rachises of Vitis vinifera L. In conclusion, plant-based coagulants mixed with bentonite are a biologic, sustainable and cheap alternative for MB removal.

In this work, the effect of the combined coagulation–flocculation–decantation (CFD) with the sulfate radical oxidation process on the treatment of two winery wastewaters (WW1 and WW2) was investigated. The oxidation process was optimized by the application of a Box–Behnken design of the Response Surface Methodology. Under the best CFD conditions: [potassium caseinate] = 0.4 g/L, [bentonite] = [PVPP] = 0.1 g/L, pH = 3.0, rapid mix (rpm/min) = 150/3, slow mix (rpm/min) = 20/20, sedimentation time = 12 h, and oxidation conditions: [sodium persulfate (SPS)] = 51.9 mM, [Fe²⁺] = 0.90 mM, pH = 3.0, radiation UV-A (365 nm), time = 300 min, a total organic carbon (TOC) and a chemical oxygen demand (COD) of 38.9 and 45.3%, respectively, were achieved for WW 1, and 51.2 and 73.3%, respectively, for WW2. The combined process shows a good potential for WW treatment.

In the present work, winery wastewater (WW) was treated by a combined coagulation–flocculation–decantation (CFD)/photo-Fenton/adsorption process. The aim of this work was to (1) optimize the CFD process with the application of polyvinylpolypyrrolidone (PVPP); (2) optimize the photo-Fenton process; (3) evaluate the efficiency of combined CFD/photo-Fenton/adsorption process. Under the best conditions ([PVPP] = 0.5 g/L, pH = 6.0, rapid mix (rpm/min) = 150/3, slow mix (rpm/min) = 20/20, sedimentation 12 h), the CFD process achieved a total organic carbon (TOC) of 46.9 %. With the application of photo-Fenton ([Fe²⁺] = 2.5 mM/[H₂O₂] = 225 mM/ pH = 3.0), a TOC removal of 69.1 and 76.0%, respectively, for UV-A and UV-C radiation was achieved. Electric energy per order (E_EO) achieved 641 and 170 kWh m⁻³ order⁻¹, respectively. The application of adsorption ([Bentonite] = 1.5 g/L, pH = 6.0, agitation = 350 rpm, sedimentation = 2 h) achieved a TOC removal of 72.0 and 76.0%, respectively. In conclusion, the combined treatment is energy efficient for WW treatment.

The present study aimed, for the first time, to evaluate the production and application of NaCl plant extracts in a coagulation–flocculation–decantation process (CFD process) for the optimization of the microfiltration process (MF process) for the treatment of winery wastewater (WW). To evaluate the efficiency of the NaCl extracts, aluminum sulfate (10%) was applied as a comparison. The CFD process was optimized by varying the WW pH, coagulant dosage, agitation, type and dosage of flocculants before the microfiltration process. The application of Chelidonium majus L. (seeds) achieved 29.7, 99.7 and 95.3% total organic carbon, turbidity and total suspended solids removal, respectively, with 108 mg of filter consumption. In conclusion, NaCl plant extracts are a promising technology for WW treatment.

The horticulture development of several plants, such as Acacia dealbata Link. (pollen), Quercus ilex L. (acorn skin), Quercus ilex L. (peeled acorn), Platanus × acerifólia (Aiton) Willd. (seeds) and Tanacetum vulgare L. (seeds), in organic coagulant powder (OCP), was utilised to treat winery wastewater (WW) through a coagulation–flocculation–decantation process (CFD). The plants were characterized by Fourier-transform infrared spectroscopy (FTIR), which showed the presence of protein, lipids and carbohydrates. The CFD results demonstrated that application of Acacia dealbata Link. (pollen) achieved similar turbidity, total suspended solids and chemical oxygen demand removal (97.6%, 94.7% and 46.6%) than aluminium sulfate (99.5, 95.3 and 43.5), with the advantage of low sludge production (66 mL/L) and low aluminium leaching concentration (0.10 mg Al/L). In conclusion, OCPs are a promising technology in horticulture development.