The transition from the linear economy paradigm to the circular economy in industrial wastewater treatment systems is on the global agenda. The search for new simple, eco-innovative, and low-cost processes for treating industrial wastewater, which can also be used by small and medium-sized industries, has been a constant challenge especially when environmental sustainability is considered. So, a new integrated industrial wastewater treatment system has been developed that includes the immediate one-step lime precipitation process (IOSLM) and atmospheric carbonation (AC), followed by constructed wetlands (CWs) or adsorption. The current review provides an overview of industrial wastewater treatment strategies for high- and low-biodegradable wastewater. A background on functionality, applicability, advantages and disadvantages, operating variables, removal mechanisms, main challenges, and recent advances are carried out for each process that makes up the IOSLM+AC+CW/adsorption integrated system. The prospects of the IOSLM+AC+CW/adsorption integrated system are also discussed. Not neglecting the improvements that still need to be made in the integrated treatment system as well as its application to various types of industrial wastewater, this review highlights that this treatment system is promising in industrial wastewater treatment and consequent by-product recovery. The IOSLM+AC integrated system showed that it can remove high amounts of organic matter, total suspended solids, oils and fats, phosphorus, and ammonium nitrogen from industrial effluents. On the other hand, constructed wetlands/adsorption can be alternatives for refining effluents still containing organic matter and nitrogen that were not possible to remove in the previous steps.

A short review on the treatment of effluents from food processing industries by electrochemical oxidation (EO) was performed. Olive mill wastewater (OMW) and boron-doped diamond (BDD) are the most reported effluent and anode material, respectively. The addition of NaCl or Na₂SO₄ as supporting electrolytes is common in these studies, and their influence on the EO performance depends, among other things, on the anode material, since the electrolyte oxidation mechanism is different when active and non-active anode materials are utilized. A case-study on the application of a pilot plant, working in batch mode with recirculation, equipped with a BDD anode, to treat 4 L of OMW, slaughterhouse (SW) and winery (WW) wastewaters, with initial chemical oxygen demands (COD) of 20.5, 3.6 and 0.26 g L⁻¹, respectively, is presented and discussed. In 16 h assays, 94% COD removal was achieved for OMW, and for SW and WW the Portuguese COD legal discharge limit of 150 mg L⁻¹ was accomplished. Process efficiency decreased for lower organic load. NaCl addition increased COD removal in SW and WW, but presented an adverse effect for OMW COD removal, when compared to Na₂SO₄ addition. Nevertheless, lower specific energy consumptions were attained in chloride medium (48 Wh (g COD)⁻¹).

This study aimed to assess the degradation and mineralization of the toluene present in a gas stream by application of a liquid phase persulfate-based advanced oxidation process in a bubble column reactor. Up to the authors' knowledge, this is the first time where the oxidizing agent has been activated through the presence of transition metal ions and pH change, to treat a toluene-containing gas stream. A detailed parametric study was performed, with the objective of analyzing the effect of some of the main operating variables in the process performance, varying parameters such as catalyst concentration (from 0 to 0.27 g/L of Fe²⁺), oxidizing agent dosage (0.80 - 2.40 g/L of S₂O₈^2-) and initial pH (from 2.0 to 6.8). The best treatment performance was achieved for the following operating conditions: [Fe²⁺] = 0.20 g/L, [S₂O₈^2-] = 1.70 g/L and initial pH = 3.0, with the process being extended for 6 h before saturation of the liquid with toluene. Under these conditions, the toluene transferred from the gaseous effluent to the liquid phase, wherein it was then degraded by the radicals, reached a value of 7.8 x 10^-2 mol/L, showing an improvement of 13 times when compared with toluene solubility in water; still, it was found that under the optimum acidic conditions, sulfate radicals have a higher contribution than hydroxyl radicals for the oxidative process. Finally, it was evidenced that the amount of toluene transferred almost duplicated when compared to other studies reported in the literature that applied Fenton's reaction to degrade toluene.

The transition from the linear economy paradigm to the circular economy in industrial wastewater treatment is on the global agenda. The search for new simple, eco-innovative and low-cost processes for treating industrial wastewater, which can also be used by small- and medium-sized industries, has been a constant challenge to ensure environmental sustainability in all types of industries. The present work aimed to evaluate the suitability of the treated slaughterhouse wastewater (SWW) obtained by the integrated process composed of immediate one-step lime precipitation (IOSLM) and atmospheric carbonation (AC) for the production of aromatic plants by hydroponics. Results showed a significant increase in plant height of 177 and 147% and root length of 64 and 37% for Pennyroyal and Chocolate Peppermint plants, respectively, after 26 days. No signs of toxicity or symptoms of micronutrient deficiency were detected in aromatic plants.