Phycoremediation of wastewater with microalgae is a viable option and is considered a process for cleaning up toxic waste using microalgae or macroalgae. Most water is modified by its use and must be treated before discharge. Given this situation, and following the example of other researchers around the world, our study focuses on the filtration method and combines it with the microalgae method to treat domestic wastewater. The aim of our work is to study the effects of using the microalgae system in combination with the decontamination and filtration system to reduce the nutrient content of domestic wastewater. The coupling of the two methods produced very significant results. However, the removal efficiencies for the filtered effluent increased to 86.34%, 100%, and 91.12% for COD, ammonia, and phosphate, respectively. The algae treatment offers an ecologically safe and less expensive system for nutrient removal and eliminates the need for tertiary treatment, which refers to the filtered treatment effluent, allowing us to conclude that the Chlorella vulgaris species has a very interesting influence on dissolved oxygen and that it had a very remarkable effect on COD, with a maximum reduction that reached 80%. The results obtained show that the phosphate content of the treated wastewater was significantly reduced during the cultivation period. In time, a decrease in solids was observed within the microalgae treatment system, influenced by the use of two different types of microalgae and the incorporation of the filtration system, which is based on the use of biosorption of methylene blue by biomass. The parameters analyzed in this study are hydrogen potential (pH), ammonia (NH₃), phosphate ion (PO₄³⁻), chemical oxygen demand (COD), electrical conductivity (EC), total solids (TS), total dissolved solids (TDS), total suspended solids (TSS), nitrates, and dissolved oxygen (DO).

The rising influence of greenhouse gas (GHG) emissions from burning fossil fuels on climate change has led to a demand for clean energy. The only consequence of H2's combustion is water vapor, making it a clean energy source. As a clean energy source, hydrogen contributes significantly to energy and environmental sustainability and helps mitigate the world's energy problem and climate change. Microalgae have recently been found to hold tremendous promise for producing biodiesel and biohydrogen. Under certain conditions, sunlight is used by green microalgae to split water particles, resulting in the production of molecular hydrogen and oxygenation. With an emphasis on green microalgae, this review outlined possible algal strains for hydrogen production. In addition, a comprehensive review procedure aimed at presenting the importance of using microalgae to produce green hydrogen. More significantly, this review included an overview of present constraints and potential future directions for the sustainable synthesis of biohydrogen from microalgae.