Combination of Coagulation-Flocculation-Decantation and Ozonation Processes for Winery Wastewater Treatment

Winery and olive mill wastewaters treatment using nitrilotriacetic acid/UV-C/Fenton process: Batch and semi-continuous mode

In this work, both red and white winery wastewaters (WW) and olive mill wastewater (OMW) were submitted to a treatment by Fenton-based processes (FBPs). The main aim was to evaluate the most efficient and economic process. Initial tests, resorting to a batch reactor, demonstrated that UV-C/Fenton (λ = 254 nm) was the most effective process. Operational conditions such as pH, H2O2 and Fe2+ concentrations revealed to have a superior influence within dissolved organic carbon (DOC) removal as well as regarding the reactor's energy consumption. As a means to prevent iron precipitation, the addition of nitrilotriacetic acid (NTA) was tested. With experimental conditions pH = 3.0, [H2O2] = 194 mM, [Fe2+] = 1.0 mM, [NTA] = 1.0 mM, radiation UV-C (254 nm), time = 240 min, the kinetic rate related with DOC removal showed a kredWW = 0.0128 min-1 > kOMW = 0.0124 min-1 > kwhiteWW = 0.0104 min-1 and both the WW and OMW achieved the Portuguese legal limit values for wastewater discharge. Furthermore, comparative experiments were performed in a semi-continuous reactor, being that the results put in evidence that the concentration of H2O2 added and the flow rate of reagents' addition (F) had a significant effect on the efficiency of the reactor. Under an optimum experimental procedure pH = 3.0, [H2O2] = 97 mM, [Fe2+] = 1.0 mM, [NTA] = 1.0 mM, radiation UV-C (254 nm), F = 1 mL min-1, time = 240 min, there were observed higher DOC removal kinetic rates (kOMW = 15.20 × 10-3 min-1 > kredWW = 11.64 × 10-3 min-1 > kwhiteWW = 11.57 × 10-3 min-1) and a cost ranging between 0.0402 and 0.0419 €/g.DOC. These results showed that semi-continuous reactors have the potential to be applied to large scale treatments, with low reagents consumption and reduced energy requirements.

Enhancement of EDDS-photo-Fenton process with plant-based coagulants for winery wastewater management

To achieve an efficient remediation of a winery wastewater (WW), it was studied a physical-chemical process (coagulation-flocculation-decantation - CFD) involving plant-based coagulants (PBC) with advanced oxidation processes (AOPs), aiming to achieve the Portuguese legal limits. Initially, one invasive (Acacia dealbata) and three native species (Quercus ilex, Platanus x acerifólia and Tanacetum vulgare) were collected and used as plant-based coagulants (PBCs). The combination of Platanus acerifólia (P.a.) seeds with polyvinylpolypyrrolidone (PVPP) achieved high turbidity (97.3%) and chemical oxygen demand (COD = 48.2%) removals, from raw WW, with [PBC] = 0.1 g/L, [PVPP] = 5 mg/L, pH = 3.0, fast mix = 150 rpm/3 min, slow mix = 20 rpm/20 min, sedimentation time = 12 h. Different AOPs were studied to treat raw WW, with photo-Fenton process revealing the highest COD efficiency (88.0%). To enhance the capabilities of photo-Fenton, ethylenediamine-N,N'-disuccinic acid trisodium salt (EDDS) was assessed as a chelation agent, reducing iron precipitation. The pre-treatment of WW by PBCs followed by EDDS/photo-Fenton (pH = 6.0, [H₂O₂] = 175 mM, [Fe²⁺] = 5 mM, [EDDS] = 1 mM, T = 298 K, time = 240 min) increased the COD removal, whatever the radiation source applied (UV-C, UV-A and solar). Among the different processes, the combined P. a. seeds and UV-C/EDDS/Fenton allowed increase the WW biodegradability from 0.26 to 0.46, and achieved a COD removal of 95.7%, reaching the Portuguese legal limits. As final remark, the synergy of PBCs and EDDS/photo-Fenton is considered effective and sustainable process for raw WW remediation and water reuse.

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

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.

Combined organic coagulants and photocatalytic processes for winery wastewater treatment

Due to the consumers demand for quality wines, washing and disinfection operations are necessary in wine productions, leading to the generation of large volumes of winery wastewater (WW) with a high organic content which has the potential to cause irreversible environmental impacts. The aim and novelty of this work is the production of natural organic coagulants (NOCs) to be applied in coagulation-flocculation-decantation (CFD) process. To complement this treatment process, it is also aimed the performed a photo-Fenton process, combining hydrogen peroxide (H₂O₂) and potassium persulfate (KPS). The Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscope (SEM) showed that NOCs are carbon-based materials with adsorption capacity. Under the best operational conditions, NOCs achieved a turbidity removal between 86.2 and 98.9%, a total suspended solids (TSS) removal ranging between 85.0 and 94.9% and a dissolved organic carbon (DOC) removal ranging between 14.1 and 44.9%. To degrade the DOC present in the WW, different advanced oxidation processes (AOPs) were tested. Results showed that KPS-photo-Fenton, under the best operational conditions [Fe²⁺] = 2.5 mM, [KPS] = 1.0 mM, pH = 3.0, radiation UV-C mercury lamp (254 nm), agitation 350 rpm, temperature 298 K, reaction time 240 min achieved a DOC removal of 91.2 and 96.8%, with a H₂O₂ consumption of 156.9 and 199.0 mM, respectively for red and white WW. With application of combined CFD-KPS-photo-Fenton process, it was observed an increase of DOC removal with lower H₂O₂ consumptions. The energy consumption of the photosystem was evaluated by application of electric energy per mass (E_EM). The application of KPS-photo-Fenton process achieved an E_EM of 0.308 and 0.0309 kWh/g/L DOC, with a cost of 2.05 and 2.59 €/g/L DOC respectively for red and white WW. The combination of CFD-KPS-photo-Fenton decreased significantly the costs of treatment and the treated wastewater achieved the Portuguese legal values for wastewater discharge. This work shows that NOCs are a promising technology that can be an alternative to traditional metal salts, the combination of sulfate radicals with hydroxyl radicals can achieve high DOC removal and the combination of CFD with KPS-photo-Fenton process can decrease the operational costs.

Degradation of Agro-Industrial Wastewater Model Compound by UV-A-Fenton Process: Batch vs. Continuous Mode

The degradation of a model agro-industrial wastewater phenolic compound (caffeic acid, CA) by a UV-A-Fenton system was investigated in this work. Experiments were carried out in order to compare batch and continuous mode. Initially, batch experiments showed that UV-A-Fenton at pH 3.0 (pH of CA solution) achieved a higher generation of HO•, leading to high CA degradation (>99.5%). The influence of different operational conditions, such as H2O2 and Fe2+ concentrations, were evaluated. The results fit a pseudo first-order (PFO) kinetic model, and a high kinetic rate of CA removal was observed, with a [CA] = 5.5 × 10−4 mol/L, [H2O2] = 2.2 × 10−3 mol/L and [Fe2+] = 1.1 × 10−4 mol/L (kCA = 0.694 min−1), with an electric energy per order (EEO) of 7.23 kWh m−3 order−1. Under the same operational conditions, experiments in continuous mode were performed under different flow rates. The results showed that CA achieved a steady state with higher space-times (θ = 0.04) in comparison to dissolved organic carbon (DOC) removal (θ = 0−0.020). The results showed that by increasing the flow rate (F) from 1 to 4 mL min−1, the CA and DOC removal rate increased significantly (kCA = 0.468 min−1; kDOC = 0.00896 min−1). It is concluded that continuous modes are advantageous systems that can be adapted to wastewater treatment plants for the treatment of real agro-industrial wastewaters.

Biotreatment Potential and Microbial Communities in Aerobic Bioreactor Systems Treating Agro-Industrial Wastewaters

The thriving agro-industry sector accounts for an essential part of the global gross domestic product, as the need for food and feed production is rising. However, the industrial processing of agricultural products requires the use of water at all stages, which consequently leads to the production of vast amounts of effluents with diverse characteristics, which contain a significantly elevated organic content. This fact reinforces the need for action to control and minimize the environmental impact of the produced wastewater, and activated sludge systems constitute a highly reliable solution for its treatment. The current review offers novel insights on the efficiency of aerobic biosystems in the treatment of agro-industrial wastewaters and their ecology, with an additional focus on the biotechnological potential of the activated sludge of such wastewater treatment plants.

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

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 with a Combination of Adsorption and Thermocatalytic Processes

The release of winery wastewater (WW) into the environment, without proper treatment, can cause severe problems to freshwater quality and natural fauna and flora. Therefore, in this work a treatment process was studied, combining adsorption and thermocatalytic oxidation processes. In a more specific way, it optimized the combination of activated sodium bentonite (Na-Mt) and potassium persulfate (KPS)/sodium percarbonate (SPC) as oxidant agents. With the combination of best operational conditions of adsorption ([Na-Mt] = 5.0 g/L, pH = 3.0, V = 500 mL, agitation 350 rpm, T = 298 K, t = 24 h) and thermocatalytic oxidation processes (S2O82−/H2O2 ratio = 1:0.25, S2O82−/H2O2 dosage = 0.1:0.025 (g/g), pH = 7.0, T = 343 K, agitation 350 rpm, t = 2 h), a total organic carbon, chemical oxygen demand and total polyphenols removal of 76.7, 81.4 and >99% was achieved, respectively. Finally, it was evaluated the effect of the treatment processes in the germination index (GI) of different plant seeds. A GI > 80% was achieved, showing a low phytotoxicity effect of the processes applied in the winery wastewater treatment.