Efficiency of Different Moringa oleifera (Lam.) Varieties as Natural Coagulants for Urban Wastewater Treatment

There is a great need to find cheaper but still efficient treatment methods for wastewater. This study aimed to test the purifying performance of three different Moringa oleifera varieties that were cultivated in Tunisia on raw (RUW) and secondary treated urban wastewater (TUW). The seeds of the Mornag, Egyptian, and Indian varieties were powdered, added to the water (at concentrations of 0, 50, 100, and 150 mg·L−1), and stirred for 45 min at 120 rpm, and then left to settle for two hours. A physicochemical characterization of the wastewater was carried out before and after treatment. The investigated treatments decontaminated both types of urban wastewater. The best treatments were obtained with the Egyptian variety (at 150 mg·L−1), which excelled at the reduction of EC, TSS, BOD5, Cl, SO4, Ca, Na, Cd, and Fe in RUW and BOD5, EC, Na, Mg, Cl, and Cd in TUW. High amounts of TKN was found in both types of Moringa-treated wastewater, meaning that it could be used in agricultural irrigation, leading to less use of chemical nitrogen fertilizers and thus improving sustainability for crops, soils, animals, and humans. The Egyptian Moringa variety constitutes a cost-effective and environmentally friendly adsorbent that can be used as a replacement for more expensive treatment technologies.

Urban Wastewater Treatment in African Countries: Evidence from the Hydroaid Initiative

This study is based on the evidence collected during the “Technical e-Learning Course on Wastewater Treatment”, an international training project developed in 2020 in Italy by the Hydroaid Association, in collaboration with Turin Polytechnic. This work intended to address the sustainability of urban sanitation in various African countries, which the world of international cooperation has been looking at in recent years with growing interest. A comparative analysis of the current strategies and technological solutions was conducted. Data and information reported by the project participants were elaborated and verified. Four African countries—Benin, Egypt, Ethiopia, and Malawi—were considered and two relevant case studies among those proposed by the participants were presented. Starting from this analysis, significant elements about the status and coverage of wastewater management were extracted and reported. The analysis of existing wastewater treatment plants (WWTPs) allowed evaluating their design features and current status of operation. Considerations about the environmental, economic, social, and technical sustainability of wastewater treatment and management were finally reported. Conducting such an analysis provided support in identifying the best practices and the most recurrent problems linked to the various African contexts, which need to be considered for a complete definition of the planning strategy for accessible, efficient, and sustainable sanitation infrastructures.

Application of the anaerobic co-digestion method to sewage sludge treatment toward recover green energy and utilize nutrients for agriculture

Sewage sludge after urban wastewater treatment needs to be treated intelligently to get maximum benefits. This study proposes a method of anaerobic co-degradation of agricultural sludge and residues to both solve environmental problems and recover a large amount of biogas and organic fertilizers. The results show the potential for energy recovery from biogas and impact assessment of the application directly on the rice fields. It is estimated that biogas recovery from sludge treatment from wastewater treatment plants gives a calorific value of about 76 × 106 MJ/year. Results from the trial crop showed that fertilizer shows good supportability to the plant. The results show that the fertilizer from sewage sludge can be reduced and replaced by 50% to 100% of the number of chemical fertilizers but still give the same yield. The data show that the anaerobic co-digestion method is a suitable method for sludge treatment. The dual objective is to provide valuable benefits from recovered biogas and anaerobic digestion products.

Extremophilic Microalgae Galdieria Gen. for Urban Wastewater Treatment: Current State, the Case of “POWER” System, and Future Prospects

Over the past decades, wastewater research has increasingly focused on the use of microalgae as a tool to remove contaminants, entrapping nutrients, and whose biomass could provide both material and energy resources. This review covers the advances in the emerging research on the use in wastewater sector of thermoacidophilic, low-lipid microalgae of the genus Galdieria, which exhibit high content of protein, reserve carbohydrates, and other potentially extractable high-value compounds. The natural tolerance of Galdieria for high toxic environments and hot climates recently made it a key player in a single-step process for municipal wastewater treatment, biomass cultivation and production of energetic compounds using hydrothermal liquefaction. In this system developed in New Mexico, Galdieria proved to be a highly performing organism, able to restore the composition of the effluent to the standards required by the current legislation for the discharge of treated wastewater. Future research efforts should focus on the implementation, in the context of wastewater treatment, of more energetically efficient cultivation systems, potentially capable of generating water with increasingly higher purity levels.