Commercialization in the meat-processing industry has emerged as one of the major agrobusiness challenges due to the large volume of wastewater produced during slaughtering and cleaning of slaughtering facilities. Slaughterhouse wastewater (SWW) contains proteins, fats, high organic contents, microbes, and other emerging pollutants (pharmaceutical and veterinary residues). It is important to first characterize the wastewater so that adequate treatment techniques can be employed so that discharge of this wastewater does not negatively impact the environment. Conventional characterization bulk parameters of slaughterhouse wastewater include pH, color, turbidity, biochemical oxygen demand (BOD), chemical oxygen demand (COD), total organic carbon (TOC), total suspended solids (TSS), total nitrogen (TN), total phosphorus (TP), and coliform counts. Characterization studies conducted have revealed the effects of the pollutants on microbial activity of SWW through identification of toxicity of antibiotic-resistant strains of bacteria. Due to the high-strength characteristics and complex recalcitrant pollutants, treatment techniques through combined processes such as anaerobic digestion coupled with advanced oxidation process were found to be more effective than stand-alone methods. Hence, there is need to explore and evaluate innovative treatments and techniques to provide a comprehensive summary of processes that can reduce the toxicity of slaughterhouse wastewater to the environment. This work presents a review of recent studies on the characterization of SWW, innovative treatments and technologies, and critical assessment for future research.

In many nations, particularly those experiencing water scarcity, novel approaches are being applied to clean wastewater. Heterogeneous photocatalysis is the most widely used of these approaches because it entails the decomposition of organic molecules into water and carbon dioxide, which is a more ecologically benign process. In our study, we studied the photocatalytic degradation process on the effluent flumequine. This treatment is made through a solar pilot reactor in the presence of immobilized titanium dioxide with three light intensities and two types of water as solvents. A variety of factors that might influence the rate of deterioration, such as flow rate, light intensity, and initial concentration, have been investigated. The maximal degradation of flumequine was achieved at more than 90% after 2.5 h under optimal conditions (an initial concentration of 5 mg/L, three lamp light intensities, and a flow rate of 29 L/h). By combining the oxidized agent H₂O₂ with this process, the photocatalytic activity was improved further to 97% under the same conditions. The mineralization of this product has also been tested using total organic carbon (TOC) analysis. A high mineralization rate has been recorded at around 50% for a high initial concentration (20 mg/L) at a flow rate of 126 L/h. The results demonstrated the highly effective removal of flumequine and the efficacy of this photocatalytic system.

Flax shives and beech wood residues represent biomass streams that are abundant in Northwest Europe. These primary feedstocks were evaluated for their suitability to produce biochar as a low environmental-impact adsorbent. The efficacy of the produced biochars was tested by their adsorption capacity towards methylene blue (MB). A series of adsorption tests with carbamazepine is also presented, focusing on the better performing beech wood biochar. Post treatment of the biochars with citric acid (CA) and oxidation of the surface by heating at 250 °C in a muffle oven were carried out to enhance the adsorption capacities of both flax shives biochar (FSBC) and beech biochar (BBC). The resulting physicochemical characteristics are described. The thermally treated biochars have specific surface areas of 388 m²·g⁻¹ and 272 m²·g⁻¹ compared to the untreated biochars with 368 and 142 m²·g⁻¹ for BBC and FSBC, respectively. CA treatment leads to enhancement of the oxygenated surface functional groups and the adsorption capacities of both studied biochars. The non-linear Langmuir and Freundlich models show the best fit for both the isotherm data for MB and the CMZ adsorption with a good correlation between the experimental and calculated adsorption capacities. The effect of adsorbent dosages and initial concentrations of MB and CMZ on the adsorption efficiency is discussed. It can be concluded that beech biochar is a very promising pollutant adsorbent only requiring a mild, low-cost, and low-environmental impact activation treatment for best performance.

Graphitic carbon nitride (g-C₃N₄) based photocatalyst was synthesized and the photocatalytic performance was investigated for the removal of Eriochrome Black T (EBT) and Bromophenol Blue (BPB) under UV irradiation. The prepared materials were characterized by SEM-EDX, XRD, Raman, FTIR and DRS. Higher degradation efficiency for the same initial concentrations of EBT and BPB in presence of TiO₂/g-C₃N₄ have been achieved within 160 min of irradiation. The kinetic study showed that the photodegradation of BPB by TiO₂/g-C₃N₄ follows pseudo-first-order kinetics with an R2 value of 0.98. The addition of persulfate (PS) in BPB solution improved the degradation yield from 8.81% to 80.14% within 20 min of UV light irradiation. A Box-Behnken model was developed from three factors and Response surface methodology (RSM) was employed to identify the optimum conditions for the treatment of BPB solution by TiO₂/g-C₃N₄. The experimental values of degradation of BPB agreed with predicted values obtained from central composite design (CCD) analysis with an R² value of 0.9999. The scavenger study revealed that superoxide radical anion (O₂^•−) plays a key role (68.89% of contribution) followed by OH^• and h⁺ with 22.40% and 15.55% of contribution, respectively. This study has obviously exhibited the potential of TiO₂/g-C₃N₄ composite as a promising catalyst for photocatalytic purposes.

ZnO thin film were deposited by Spray and Spray Pyrolysis methods on glass substrates at 370 °C. The structural characterization by XRD, Raman spectroscopy, FTIR, EDS, TEM, SEM, RPE and XPS revealed the purity of ZnO Wurtzite variety in both samples. The use of a new loop reactor configuration for the photocatalytic activity was evaluated against/with respect to the degradation of two textile dyes as well as their binary mixture. The ZnO thin film prepared by Spray Pyrolysis kept its photocatalytic properties even after 20 reuse cycles (148 h). The treated solution showed better biodegradability and the absence of phytotoxicity.