Evaluation of COD and color removals of effluents from UASB reactor treating olive oil mill wastewater by Fenton process

Olive mill wastewater treatment strategies to obtain quality water for irrigation: A review

The olive mill industry is a relevant sector in the economy of Mediterranean countries, while it involves high consumption of water and the production of effluents with high environmental impact. The efficient treatment of olive mill wastewater (OMW) is of high relevance, particularly for these countries. Climate changes are leading to increasing periods of droughts, and water recovery from polluted streams is essential to ensure the sustainability of this scarce resource. A combination of various technologies involving physical, chemical, and biological processes has been developed for OMW treatment. However, the treatments studied have limitations such as the operation costs, difficulty of industrial scale-up, and the fact that the vast majority do not lead to suitable treated water for discharge/reuse. As such, it is urgent to develop a solution capable of efficiently treating this effluent, overcoming the disadvantages of existing processes to convert OMW from a serious environmental problem into a valuable source of water and nutrients. In this review, several studies based on the OMW treatment are critically discussed, from conventional approaches such as the physical (e.g. centrifugation, filtration, and adsorption) and biological (anaerobic digestion and anaerobic co-digestion) processes, to the most recent technologies such as advanced membrane filtration, advanced oxidation processes (AOPs) and sulfate radical based AOPs (SR-AOPs). Due to the complexity of the effluent, OMW cannot be efficiently treated by a single process, requiring a sequence of technologies before reaching the required characteristics for discharge into water courses or use in crop irrigation. Reviewing the published results in this matter, it seems that the sequence of processes encompassing ozonation, anaerobic digestion, and SR-AOPs could be the ideal combination for this purpose. However, membrane technologies may be necessary in the final stage of treatment so that the effluent meets legal discharge or irrigation limits.

Treatment of Olefin plant spent caustic by combination of Fenton-like and foam fractionation methods in a bench scale

Spent Merox caustic (SMC) is a hazardous waste that is produced during the Merox desulfurization process in the petroleum refinery industry and should be treated before discharging to environment. In the present study, treatment of SMC was investigated by three methods including Fenton-like process, foam fractionation, and a combination of both processes. Immobilized TiO₂/Fe⁰ on modified silica nanoparticles was used as a heterogeneous Fenton-like catalyst. The chemical and physical characteristics of the catalyst were determined using Fourier-transform infrared spectroscopy, X-ray diffraction, diffuse reflectance spectroscopy, thermogravimetric analysis, differential scanning calorimetry, and transmission electron microscopy techniques. The treatment performance of the combined method was measured as a cost-effective method with chemical oxygen demand (COD) removal percentage. The effect of parameters including pH, gas flow rate, surfactant type and concentration of hydrogen peroxide, catalyst, and chelate were investigated. It is found that the prepared heterogeneous catalyst has high activity for the treatment of SMC. In addition, the results showed that the combined method achieved 97.6 ± 0.5% COD removal, while the measured values for Fenton or foam fractionation methods alone did not exceed 85.5 ± 1% and 47.2 ± 0.4%, respectively. The advantage of combination process over foam fractionation was the use of an advanced oxidation process in the separating column to eliminate or reduce the secondary phase contamination load. Besides, the role of the column in the effective contact of contaminants with the rising bubbles improved the degradation performance of the proposed process and reduced the consumption of hydrogen peroxide by 46% compared to the Fenton-like method.

Comparison of kinetics and costs of Fenton and photo-Fenton processes used for the treatment of a textile industry wastewater

In this study, the treatment of textile industrial wastewater by Fenton and Photo-Fenton oxidation processes was investigated. For this purpose, the pH, Fe²⁺ and H₂O₂ concentrations with the best organic matter and color removal were determined in the Fenton process and comparison with Fenton was made by Photo-Fenton oxidation at the optimal Fe²⁺/H₂O₂ ratio. The influent COD and TOC values of the wastewater used in the study were 848 mg/L and 253 mg/L, respectively. With the Fenton process, the best organic matter and color removal was obtained at pH 3, at 200 mg/L Fe²⁺ and 300 mg/L H₂O₂ concentrations. Under these conditions, 88.9% COD, 84.2% TOC and over 97% color removal were obtained with Fenton oxidation, and 93.2% COD, 88.9% TOC and 98% color were obtained with Photo-Fenton oxidation. However, when Fe²⁺ and H₂O₂ amounts were reduced to 50 mg/L and 75 mg/L, both organic matter and color removal were reduced with Fenton process, while higher organic matter removal and color removal were achieved with Photo-Fenton process. The total cost was changed between 9.56-16.88 €/m³ and 13.46-20.13 €/m³ with Fenton and Photo-Fenton oxidation process for all Fe²⁺/H₂O₂ ratios, respectively. With the Photo-Fenton oxidation process, higher organic matter removal was obtained at optimum Fe²⁺ and H₂O₂ concentrations. In addition, less Fe²⁺ and H₂O₂ chemicals were used in Photo-Fenton oxidation process to achieve the same removal efficiency compared to the Fenton oxidation process.

Environmental assessment of refectory waste based on approaches zero-waste project in Turkey: the production of biogas from the refectory waste

The zero-waste project in Turkey, which was started in 2017, is planned to be implemented until 2023, starting from public institutions and organizations. However, in refectories where high amounts of organic waste are generated, these organic wastes are generally transported to the landfill site by the municipalities and, consequently, they go beyond the scope of the zero-waste project. In this study, the anaerobic treatment of refectory wastes based on the scope of the zero-waste approach in Turkey has been developed as an innovative and holistic approach. As a result of the informing studies in the refectories, the waste of bread could be zero, while the waste of meals could not be zero, but a significant decrease in meal waste was found. In addition, this holistic approach has also strengthened recycling. Anaerobic digestion was selected to complete the zero-waste target for food wastes that are still generated. In the study using the UASB reactor operated in mesophilic conditions (36.5-37 °C), feeding has been done with approximately 21.9 kg VS_added m^-3 OLR in 10-day HRT. As a result, it was observed that the production of biogas and organic fertilizers from food waste using anaerobic technologies is an important solution on behalf of realizing the zero-waste application. The results showed that 1 kg of food waste with 62 ± 3.2% solid content could produce 640 L of biogas with approximately 62.2 ± 0.6% methane content. In addition, a 26.2-L bio-fertilizer with an average COD concentration of 3354 ± 106 mg L^-1 was produced. This research paper with a successful method at the Adıyaman University in Turkey focuses on the goal of zero waste. This study illustrated how it is possible to implement an effective initiative to reduce food waste with a holistic approach.