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This paper documents the results of 12 months of monitoring of an upgraded hybrid moving bed biofilm reactor-conventional activated sludge wastewater treatment plant (MBBR-CAS WWTP). It also targets the assessment of the increment of the hydraulic load on existing treatment units with a zero construction and land cost. The influent flow to the plant was increased from 21,000 m3 d−1 to 30,000 m3 d−1, 40% of the existing CAS reactor volume was used for the MBBR zone with a carrier fill fraction of 47.62% and with Headworks Bio ActiveCell™ 515 used as media; no modifications were made for the primary and secondary tanks. The hybrid reactor showed high removal efficiencies for biochemical oxygen demand (BOD5), chemical oxygen demand (COD) and total suspended solids (TSS), with average effluent values recording 33.00 ± 8.87 mg L−1, 52.90 ± 9.65 mg L−1 and 29.50 ± 6.64 mg L−1 respectively. Nutrient removals in the hybrid modified biological reactor were moderate compared with carbon removal despite the high C/N ratio of 12.33. Findings in this study favor the application of MBBR in the upgrading of existing CAS plants with the plant BOD5 removal efficiency recording an increase of about 5% compared with the plant before upgrade and effluent values well within the legal requirements.

The human health, aquatic life and environment are greatly affected by the existence of industrial waste in water especially the textile dye. Advanced oxidation processes (AOPs) are considered more effective in removing the toxic pollutants from the waste water in comparison with traditional biological, physical and chemical processes. The later have the limitations of high energy requirement, cost and production of secondary pollutants during the treatment process. AOPs received significant attentions to eliminate the recalcitrant dyes from the aqueous environment owing to the production of highly reactive hydroxyl radicals produced via light irradiation. This study focused on using the response surface methodology (RSM) to evaluate its prediction and optimizing capability in the deployment of AOPs in removing obstinate pollutants from industrial waste water. The data were obtained from the existing literature related to the decomposition of textile dye [reactive red (RR-147)] under UV illumination in the presence of hydrogen peroxide (H2O2) and the photocatalyst, i.e., titanium dioxide (TiO2). The influence of different process parameters like dye concentration, pH of the solution, H2O2 contents, UV illumination time and photocatalyst were studied on dye removal percentage. The input parameters for efficient removal process were optimized using developed RSM models. Four different scenarios were created to see the effect of selected parameters while keeping the remaining process parameters maintained at fixed values. The predicted results depicted that the dye removal percentage was mainly affected by the tested variables, as well as their synergistic effects which was observed compliant with the experimental results. Performance analysis of the developed RSM models showed a high coefficient of determination value significantly higher than R2 = 0.99), thus guaranteed a satisfactory prediction equations of the second-order regression models. The observed results showed that for 50 ppm dye concentration, H2O2 0.9 ml, pH 3.4, TiO2 0.6 g and UV irradiation time 60 min, the maximum breakdown of 92% was observed. The degradation of the RR-147 dye is tested to be more effectively accomplished by the UV/H2O2/TiO2 system.