The quality of freshwater and its supply, particularly for domestic and industrial purposes are waning due to urbanization and inefficient conventional wastewater treatment (WWT) processes. For decades, conventional WWT processes have succeeded to some extent in treating effluents to meet standard discharge requirements. However, improvements in WWT are necessary to render treated wastewater for re-use in the industrial, agricultural, and domestic sectors. Three emerging technologies including membrane technology, microbial fuel cells and microalgae, as well as WWT strategies are discussed in this chapter. These applications are a promising alternative for manifold WWT processes and distribution systems in mitigating contaminants to meet acceptable limitations. The basic principles, types and applications, merits, and demerits of the aforementioned technologies are addressed in relation to their current limitations and future research needs. The development in WWT blueprints will augment the application of these emerging technologies for sustainable management and water conservation, with re-use strategies.

Adsorption of Pb, Cr, and Ni ions from spent lubrication oil (SLO) by sulphuric acid modified clay (SAMC) was investigated considering the effect of contact time and temperature of the adsorption system. The removal percentage of the heavy metals was found to be temperature and contact timedependent. Adsorption of the heavy metals increases with an increase in temperature and contact time with 95.0% -100% adsorption recorded at the temperature of 331 K with the equilibration time of 12 hours. The thermodynamic and kinetics investigation of the adsorption process showed that the adsorption of these metals by the modified adsorbent is a spontaneous and endothermic physical adsorption process that followed the pseudo-secondorder kinetic model.

Lignocellulosic biomass has gained increasing recognition in the past decades for the production of value-added products (VAPs). Biomass feedstocks obtained from various sources, their composition, and pretreatment techniques employed for delignification into bioenergy production are discussed. The conversion processes of biomass into VAPs involve various methods. Notable among them are biochemical conversions; namely, anaerobic digestion and ethanol fermentation, and thermo-chemical conversions; namely, pyrolysis and gasification which are considered in this chapter. Microalgae can adapt to changes in the environment, producing biomass that serves as a precursor for a variety of biomolecules, such as proteins, which find their application in pharmaceutical, cosmetic, and biofuel industries. Suitable strains of freshwater microalgae biomass contain high levels of lipid which can be harnessed for bioenergy production. Hence, the advancement in the conversion of biomass into VAPs could help scientists and environmentalists for sustainable use of biomass in future developments.

The remediation of the contaminated environment using the physical, thermal, or chemical methods has been criticized due to their high-cost implication, non-eco-friendly and inability to meet remediation objectives. Bioremediation offers the application of environmentally benign and cost-effective biological techniques for the remediation of contaminated sites. This chapter provides an overview of bioremediation technologies for the remediation of hazardous substances in the environment while highlighting the application of bioturbation as a promising bioremediation tool for the effective treatment of organic and inorganic contaminants. Given the success of bioremediation, most of these technologies are yet to be applied on a large scale which presents a drawback to this technique. Challenges and prospects for the effective application of bioremediation technologies were discussed.

Microalgae are unicellular, eukaryotic organisms which possess unique qualities of replication, producing biomass as a precursor for biofuels, nutraceuticals, biofertilizer, and fine chemicals including hydrocarbons. Microalgae access nitrates and phosphates in wastewater from municipalities, industries, and agricultural processes to grow. Wastewater is, therefore, culture media for microalgae, and provides the needed nutrients, micronutrients, inorganic and organic pollutants to produce microalgae biomass. Suitable strains of microalgae cultivated under mesophilic conditions in wastewater with optimized hydrodynamics, hydraulic retention time (HRT), luminous intensity, and other co-factors produce biomass of high specific growth rate, high productivity, and with high density. The hydrodynamics are determined using a range of bioreactors from raceway ponds, photobioreactors to hybrid reactors. Carbon dioxide is used in the photosynthetic process, which offers different growth stimuli in the daytime and the night-time as the microalgae cultivation technique is navigated between autotrophy, heterotrophy, and mixotrophy resulting in microalgal lipids of different compositions.