An integrated bioaugmentation/electrocoagulation concept for olive mill wastewater management and the reuse in irrigation of biofuel plants: a pilot study

Synergistic effects (adsorption and biodegradation) of Streptomyces hydrogenans immobilization on nano-reed biochar for further application in upflow anaerobic sludge blanket

Water pollution due to wastewater is a serious issue that needs to be studied as many organic compounds are released from wastewater, affecting the ecosystem. Therefore, appropriate treatment methods should be used to prevent these effects. Phragmites australis biochar immobilized with bacteria was prepared in this study for use as an adsorbent in a pilot-scale up-flow anaerobic sludge blanket (UASB) to remove organic matter from wastewater in a buffalo farm. Combining reed biochar and immobilized Streptomyces hydrogenans introduces a synergistic effect: reed biochar serves as a substrate for microbial colonization and provides a conducive environment for microbial growth while Streptomyces hydrogenans, immobilized on the biochar, enhances the degradation of organic matter through its metabolic activities. Suitable techniques were employed, including infrared spectroscopy (FTIR) to determine the functional groups before and after adsorption, scanning electron microscopy (SEM) to determine the morphology of the composite before and after adsorption, X-ray diffraction (XRD) to examine the mineralogical changes through reflectometry, high-resolution diffraction and Brunauer-Emmett-Teller (BET) analyses to determine the surface area that always carried out by nitrogen adsorption/desorption technique based on the BET isotherm. Two-level factorial design experiments optimized using biochar, immobilized with bacteria, were employed to enhance the UASB performance. Chemical oxygen demand (COD) removal and biogas production were studied as a function of four experimental parameters: biochar dose, buffalo sludge dose, pH, and bacteria type. The buffalo sludge (manure) dose negatively affected the model's performance. The results showed better COD removal with Streptomyces hydrogenans S11 inoculation. The optimum biochar dose, buffalo sludge dose, and pH were 20 g L-1, 0%, and 7.5, respectively. The COD removal efficiency under these experimental conditions reached 92.70% with a biogas production of 5.0 mL. The experimental results of a validated point from the model were 90.80% for COD removal ratio and 4.80 mL for biogas production at 2 g L-1 biochar dose, 0% buffalo sludge dose, and pH 7.5 using Streptomyces hydrogenans S11 bacteria. A buffalo wastewater (BWW) anaerobic digestion experimental model was best fitted to the data under optimal conditions. This study aligns with the United Nations Sustainable Development Goals (SDGs), specifically SDG 6 (clean water and sanitation) and SDG 12 (responsible consumption and production). The implications of our work extend to large-scale applications, promising a greener and more sustainable future for wastewater treatment.

Recent Applications of the Electrocoagulation Process on Agro-Based Industrial Wastewater: A Review

Agro-based final discharge is one of the major contributors to wastewater in the world. It creates high demand for efficient treatment. The electrocoagulation process can be used for agro-based wastewater treatment. The performance of the electrocoagulation process is based on several parameters, including the electrode materials, electrolysis time, current density, and electrolyte support. Agro-based industrial wastewater (AIW) treatment processes depend on the characteristics of the wastewater. The removal of organic content from various sources of AIW can reach up to more than 80%. Some studies show that the performance of the electrochemical process can be increased using a combination with other methods. Those other methods include biological and physical treatment. The results of previous research show that organic content and color can be degraded completely. The relationship between the energy consumption and operating cost was analyzed in order to show the efficiency of electrocoagulation treatment.

Application oriented bioaugmentation processes: Mechanism, performance improvement and scale-up

Bioaugmentation is an optimization method with great potential to improve the treatment effect by introducing specific strains into the biological treatment system. In this study, a comprehensive review of the mechanism of bioaugmentation from the aspect of microbial community structure, the optimization methods facilitating application as well as feasible approaches of scale-up application has been provided. The different contribution of indigenous and exogenous strains was critically analyzed, the relationship between microbial community variation and system performance was clarified. Operation regulation and immobilization technologies are effective methods to deal with the possible failure of bioaugmentation. The gradual expansion from lab-scale, pilot scale to full-scale, the transformation and upgrading of wastewater treatment plants through the combination of direct dosing and biofilm, and the application of side-stream reactors are feasible ways to realize the full-scale application. The future challenges and prospects in this field were also proposed.

Organic Pollutants Removal from Olive Mill Wastewater Using Electrocoagulation Process via Central Composite Design (CCD)

Electrocoagulation (EC) was studied in this study as a potential alternative approach for treating Olive Mill Wastewater (OMW). Aluminum plates were utilized as anode and cathode to evaluate the removal of Chemical Oxygen Demand (COD) from OMW and the aluminum electrode’s weight loss. Central Composite Experimental Design (CCD) and Response Surface Methodology were used to optimize its performance. Anodes were weighed before and after each electrocoagulation experiment, to compare the experimental and the theoretical dissolved aluminum weights calculated using Faraday’s law. We discovered the following EC conditions for CCD: current density = 15 mA/cm2, pH = 4, and electrolysis time of 30 min. Under these conditions, the maximum COD removal ratio was 41%, equating to an Al weight loss of 288.89 g/m3 at an estimated operating cost of 1.60 USD/m3. According to the response optimizer, the most economical operating settings for COD removal efficiency of 58.888% are pH 4, a current density of 18.41 mA/cm2, electrolysis time of 36.82 min, and Al weight loss of 337.33 g/m3, with a projected running cost of 2.00 USD/m3.

Tanning process promotes abiotic humification: separation and characterization of humic acid-like polymers complex

Humic-like substances are essential components of soluble organic matter in tannery wastewater. However, the tannery process can promote the abiotic humification in wastewater. Therefore, it is of great significance to clarify the pathway and degree of abiotic humification and the properties of the as-derived humic acid-like (HAL) complex polymers in the tannery process in order to control the refractory organic compounds. In the present study, considering the catechol-Maillard system and commercial humic acid (HA) as control, the polyphenol-Maillard humification in the tannery process was simulated under the catalysis of MnO₂. Moreover, physicochemical and spectroscopic techniques were used to characterize the separated fractions of HAL further. As a result, it was found that the catechol-Maillard system with small molecule organic matter as precursor had higher humification degree. Furthermore, the ultraviolet-visible (UV-Vis), Fourier transform infrared (FTIR), and excitation-emission matrix (EEM) fluorescence spectrum of humic acid-like 0 (HAL0) derived from it was different from those of humic acid-like 1 and 2 (HAL1 and HAL2) of polyphenol-Maillard system, indicating the differences of polymer structure between them. In the polyphenol-Maillard system, tannin was the skeleton of polymerization or polycondensation reaction, and the high content of N and the H/C value of HAL2 indicated that in adding to amino acids, proteins promoted the humification, forming industry-specific HAL polymers with a high degree of aliphatic nature. Therefore, it can be concluded that controlling the raw materials in the tannery process (especially tannins), in order to reduce the occurrence of abiotic humification may be the key to improve the efficiency of wastewater treatment.