Synergistic cooperation and interaction between algae and bacteria had made it easy by using one single step only to efficiently eliminate the impurities found in wastewater. High pollution levels triggered by the disposal of untreated wastewater and the harsh social and economic conditions, together with high construction and operation costs of conventional wastewater treatment systems, made it vital to find simple, efficient, cost-effective treatment systems. In this research work, a hybrid microalgae-bacteria pilot outdoor system comprised of a series of Algaewheel® rotating algae contactors (RACs) that receive preliminary treated domestic wastewater at a hydraulic retention time (HRT) of 8 hours was monitored for a period of 5 months. An average dissolved oxygen (DO) value of 3.04 ± 1.02 mgL⁻¹ was obtained in the effluent-treated wastewater. While the average removal efficiencies recorded for the parameters monitored were 90.73% for BOD5, 89.10% for COD, 93.45% for TSS, 77.05% for NH3-N, and 70.40% for TN. All the effluent values for the parameters monitored were below the limits of both the local and international standards. The pilot system was found to be suitable and adaptable for small communities with low discharges of 5000 m³/day or less due to its low operation and maintenance requirements, as its electricity consumption is 80% less compared with the conventional wastewater treatment systems. Doi: 10.28991/CEJ-2024-010-11-09 Full Text: PDF

This study evaluated the efficiency of an on-site household greywater treatment system for indirect human reuse and for domestic lawn irrigation. This helps in the reduction in the disparity between water demand and supply that is facing the rapidly increasing global populace. Natural household greywater was settled and then conventionally filtered by using two types of non-woven geotextile media; thermally bonded and needle punched. A third woven cotton textile media was also experimented and all the non-woven geotextile media were tested in single and double layers and combined with the woven cotton textile layer. The different filter media configurations were tested for a period of one year operation (six runs) with two filtration rates of 15.00 and 25.00 m³/m²/day for each run. For all runs, the final treated effluent was disinfected using calcium hypochlorite prior to reuse. The double layer needle punched non-woven geotextile media together with the woven cotton textile media gave the best removal efficiencies; 96.34 ± 1.85% for turbidity 81.87 ± 6.43% for BOD₅, 97.49 ± 1.68% for TSS, 75.35 ± 3.99% for CODt, 99.59% for E.coli. The soluble CODs removal efficiencies were negligible (below 3%) in the first four runs with non-woven geotextile media and increased to 28.05 ± 4.29% when the woven cotton textile media was added. In general, the system was found to save about 63% of the daily water consumption reflecting a net 22.50% reduction in the daily water billing costs for the whole household.

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.