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This study investigates the influence of photoperiod and wastewater concentration on the growth of microalgae and cyanobacteria for the removal of environmentally significant parameters (COD, BOD, Cr, Fe, color, chlorides, nitrogen compounds, and phosphates) from dyeing wastewater. A two-factor central composite design with surface response was employed, involving two algae species (Chlorella and Scenedesmus sp.) and two cyanobacteria species (Hapalosiphon and Oscillatoria sp.). The findings indicated that extended photoperiods (>13 h) and higher wastewater concentrations (70–80% v/v) enhanced biomass production across all strains. However, Hapalosiphon and Chlorella sp. (1.6 and 0.45 g/L) exhibited better tolerance to the wastewater’s high toxicity, resulting in higher biomass concentrations and improved COD and BOD removal by Hapalosiphon sp. (75% and 80%, respectively). Further analysis of the obtained biomass revealed their potential applications. Among the cyanobacteria, Hapalosiphon sp. synthesized the highest concentrations of total proteins and lipids (38% and 28% w/w, respectively), while Oscillatoria sp. displayed a high protein content (42% w/w). In contrast, the algae demonstrated a strong propensity for storing substantial quantities of total carbohydrates (65% and 57% w/w for Scenedesmus and Chlorella sp., respectively). These results signify the feasibility of cultivating photosynthetic microorganisms in industrial dyeing wastewater as a sustainable source of nutrients for targeted metabolite production.

A bicarbonate-peroxide (BAP) system was evaluated to improve the quality of industrial tannery wastewater using an I-optimal experimental design with four variables (temperature, initial pH, bicarbonate, and H2O2 concentration). The response variables were COD removal, ammonia nitrogen removal, and nitrate concentration. The most critical variables were optimized using a The process was carried out in 500 mL reactors, the operational volume of 250 mL, and the agitation was at 550 rpm. A new I-optimal reaction surface design at two levels (bicarbonate concentration 0.01–0.3 mol/L and H2O2 0.05–0.35 mol/L) was used to obtain the optimal data of the experimental design. Optimal conditions were validated by one-way ANOVA statistical analysis using Prism software. Temperatures above 50 °C promote the efficiency of the BAP system, and slightly acidic initial pHs allow stabilization of the system upon inclusion of bicarbonate and peroxide in the concentration of bicarbonate, which is critical for the reaction with peroxide and formation of reactive oxygen species. With the validated optimal data, removal percentages above 78% were achieved for nitrites, ammonia nitrogen, chromium, TSS, BOD, conductivity, chromium, and chlorides; for COD and TOC, removal percentages were above 45%, these results being equal and even higher than other AOPs implemented for this type of water.