Search Results (13)

As human living standards have improved, the demand for industrial products—such as food, dyes, cosmetics, pharmaceuticals, and others—has significantly increased. This surge in production has, in turn, led to a rise in industrial wastewater (IW) generation, which is often marked by low biodegradability and a high concentration of toxic or refractory compounds. This review highlights the use of coagulation–flocculation–decantation (CFD) and advanced oxidation processes (AOPs) for treating such wastewater. A comprehensive analysis of CFD is provided, covering the underlying mechanisms, types of coagulants (including metal-based, animal-derived, mineral, and plant-based), and the optimal operational conditions required to maximize treatment efficiency. This review discusses the properties and performance of these coagulants in detail. In addition, this paper explores the methods used in AOPs to reduce organic carbon, focusing particularly on the roles of hydroxyl and sulfate radicals. Emphasis is placed on the enhancement of these processes using radiation, chelating agents, and heterogeneous catalysts, along with their effectiveness in IW treatment. Finally, the integration of CFD as a pre-treatment step to improve the efficiency of subsequent AOPs is provided. Full article

In this study, two by-products resulting from the processing of cherry (stems and pits) were used as natural coagulants to promote the valorization of these wastes and treat olive mill wastewater (OMW). The efficacy of the plant-based coagulants (PBCs) in the coagulation–flocculation–decantation process (CFD) was evaluated through the removal of turbidity, total suspended solids (TSS), total polyphenols (TPh), and dissolved organic carbon (DOC). The CFD process was demonstrated to be effective in turbidity and TSS reduction in OMW. Using cherry stems (CSs), these reductions were 65.2% of turbidity and 58.0% of TSS, while cherry pits (CPs) achieved higher reductions, 78.6% of turbidity and 68.2% of TSS. To improve the effectiveness of OMW treatment, mainly regarding the removal of TPh and DOC, the CFD process was complemented with the adsorption process (using bentonite clay). The adsorption capacity of bentonite was higher in acidic conditions (pH 3.0) and, with a dosage of 3.0 g L⁻¹, reached 17.3 mg of DOC and 13.8 mg of TPh per gram of bentonite. Several adsorption isothermal models were assessed, and the Langmuir (r² = 0.985), SIPS (r² = 0.992), and Jovanovic models (r² = 0.994) provided the best fittings. According to the optimal operational conditions defined throughout the present work, the combination of CFD and adsorption removals were as follows: (1) 98.0 and 91.3% of turbidity, (2) 80.8 and 81.2% of TSS, (3) 98.1 and 97.6% of TPh and (4) 57.9 and 62.2% of DOC, for CSs and CPs, correspondingly. Overall, the results suggest that cherry by-products can be used as low-cost natural coagulants and, when combined with another natural, abundant, and cheap material, such as bentonite clay, can be a sustainable alternative for treating OMW. Full article

This review aims to study in detail the characterization of winery wastewater (WW), the problems caused by its release into the environment without proper treatment, and the processes that can be applied for its treatment. Several works showed that the WW has a composition based on soluble sugars, organic acids, alcohols, and high molecular weight compounds. Among these, the phenolic compounds are considered to be very toxic, due to the difficulty of degradation by microorganisms, and also because they represent toxicity to humans and animals. To solve this issue, biologic treatments are considered to be cheaper and more effective for biodegradable WW, with the possibility to store biogas with anaerobic treatments. To complement biological treatments, physical-chemical processes based on adsorption, coagulation-flocculation-decantation (CFD), and advanced oxidation processes (AOPs) are also discussed in this review. Full article

Olive washing wastewater (OWW) is generated before the olive oil extraction process in a preliminary step which consists of washing the olives with potable water. The discharge of OWW without suitable treatment can create serious environmental issues. Hence, in this work, a coagulation–flocculation–decantation (CFD) process was initially studied using ferrous sulfate, optimizing the operational conditions. Afterwards, the CFD process was combined with a UV-A LEDs/Fenton as pre- and post-treatment process, evaluating the use of the remaining ferrous ions in both situations. After finding the best operational conditions (CFD: natural pH, [Fe²⁺] = 3.60 mM, fast mixing = 150 rpm/3 min, slow mixing = 20 rpm/20 min, and 360 min of sedimentation; UV-A LEDs/Fenton: natural pH, [Fe²⁺] = 3.60 mM, [H₂O₂] = 116.4 mM, and 120 min of reaction) and combining both processes, the CFD followed by UV-A LEDs/Fenton allowed us to achieve the best removals: 91.0% of DOC, 97.5% of COD, 95.7% of turbidity, and 89.8% of TSS. Full article

The large production of wine and almonds leads to the generation of sub-products, such as winery wastewater (WW) and almond skin. WW is characterized by its high content of recalcitrant organic matter (biodegradability index < 0.30). Therefore, the aim of this work was to (1) apply the coagulation–flocculation–decantation (CFD) process with an organic coagulant based on almond skin extract (ASE), (2) treat the organic recalcitrant matter through sulfate radical advanced oxidation processes (SR-AOPs) and (3) evaluate the efficiency of combined CFD with UV-A, UV-C and ultrasound (US) reactors. The CFD process was applied with variation in the ASE concentration vs. pH, with results showing a chemical oxygen demand (COD) removal of 61.2% (0.5 g/L ASE, pH = 3.0). After CFD, the germination index (GI) of cucumber and corn seeds was ≥80%; thus, the sludge can be recycled as fertilizer. The SR-AOP initial conditions were achieved by the application of a Box–Behnken response surface methodology, which described the relationship between three independent variables (peroxymonosulfate (PMS) concentration, cobalt (Co²⁺) concentration and UV-A radiation intensity). Afterwards, the SR-AOPs were optimized by varying the pH, temperature, catalyst type and reagent addition manner. With the application of CFD as a pre-treatment followed by SR-AOP under optimal conditions (pH = 6.0, [PMS] = 5.88 mM, [Co²⁺] = 5 mM, T = 343 K, reaction time 240 min), the COD removal increased to 85.9, 82.6 and 80.2%, respectively, for UV-A, UV-C and US reactors. All treated wastewater met the Portuguese legislation for discharge in a municipal sewage network (COD ≤ 1000 mg O₂/L). As a final remark, the combination of CFD with SR-AOPs is a sustainable, safe and clean strategy for WW treatment and subproduct valorization. Full article

The removal of dissolved organic carbon (DOC) and total polyphenols (TPh) from agro-industrial wastewater was evaluated via the application of coagulation–flocculation–decantation (CFD) and Fenton-based processes. For the CFD process, an organic coagulant based on Acacia dealbata Link. leaf powder (LP) was applied. The results showed that the application of the LP at pH 3.0, with an LP:DOC ratio of 0.5:1 (w/w), achieved a high removal of turbidity, total suspended solids (TSS), and volatile suspended solids (VSS) of 84.7, 79.1, and 76.6%, respectively. The CFD sludge was recycled as fertilizer in plant culture (germination index ≥ 80%). Afterwards, the direct application of Fenton-based processes to raw WW was assessed. The Fenton-based processes (UV/Fenton, UV/Fenton-like, and heterogeneous UV/Fenton) showed high energy efficiency and a cost of 1.29, 1.31 and 1.82 €/g/L DOC removal, respectively. The combination of both processes showed the near complete removal of TPh and DOC after 240 min of reaction time, with high energy efficiency. In accordance with the results obtained, the combination of CFD with Fenton-based processes achieves the legal limits for the disposal of water into the environment, thus allowing the water to be recycled for irrigation. Full article

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. Full article

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. Full article

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. Full article

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. Full article

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. Full article

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. Full article

This research assessed a novel treatment process of winery wastewater, through the application of a chemical-based process aiming to decrease the high organic carbon content, which represents a difficulty for wastewater treatment plants and a public health problem. Firstly, a coagulation–flocculation–decantation process (CFD process) was optimized by a simplex lattice design. Afterwards, the efficiency of a UV-C/ferrous iron/ozone system was assessed for organic carbon removal in winery wastewater. This system was applied alone and in combination with the CFD process (as a pre- and post-treatment). The coagulation–flocculation–decantation process, with a mixture of 0.48 g/L potassium caseinate and 0.52 g/L bentonite at pH 4.0, achieved 98.3, 97.6, and 87.8% removals of turbidity, total suspended solids, and total polyphenols, respectively. For the ozonation process, the required pH and ferrous iron concentration (Fe²⁺) were crucial variables in treatment optimization. With the application of the best operational conditions (pH = 4.0, [Fe²⁺] = 1.0 mM), the UV-C/ferrous iron/ozone system achieved 63.2% total organic carbon (TOC) removal and an energy consumption of 1843 kWh∙m⁻³∙order⁻¹. The combination of CFD and ozonation processes increased the TOC removal to 66.1 and 65.5%, respectively, for the ozone/ferrous iron/UV-C/CFD and CFD/ozone/ferrous iron/UV-C systems. In addition, the germination index of several seeds was assessed and excellent values (>80%) were observed, which revealed the reduction in phytotoxicity. In conclusion, the combination of CFD and UV-C/ferrous iron/ozone processes is efficient for WW treatment. Full article