This research investigates a novel platform for an energy-yielding wastewater treatment and desalination scheme in which the organic matter present in wastewater is purposely fed to the exoelectrogenic bacteria to produce bioelectricity in a three-compartment bioelectrochemical system called photosynthetic microbial desalination cell (PMDC). The role of an inorganic carbon source in the microalgae biocathode was studied. Addition of sodium bicarbonate (NaHCO3) increased power production, microalgae growth and desalination rate. A power density of 660 mW/m3 was measured which is about 7.5 times higher than the PMDCs without NaHCO3. Desalination rate was more than 40% after 72 h. Overall, the process could be energy-positive while producing 4.21 kWh per m3 of wastewater treated including desalination energy savings and microalgae biomass energy potential.

The synergistic effect of microwave and ultrasound irradiations was evaluated for biodiesel production from microalgae biomass (Nannochloropsis sp.) as raw material. A response surface methodology technique based on central composite design was used to understand the process parametric interdependence and optimize the process reaction variables. Reaction kinetics of algal fatty acid methyl ester (FAME) production was also studied. The optimum reaction conditions were determined as wet algal biomass to methanol ratio of 20 g to 30 mL, 1 wt% catalyst concentration, and 7-minute reaction time at 140 W of microwave power and 140 W of ultrasound power. The estimated activation energy was 17,298 J/mol−1 K−1 for a first-order reaction kinetics. This study revealed that microwave energy dissipation at a low rate of 140 W combined with 140 W of ultrasound intensity is adequate to produce FAMEs at a maximum yield of 48.2%. Results from this optimization study suggest that a more detailed and mechanistic energy optimization study is critical to increase the FAME yield and maximize energy benefits.

Providing clean water for human consumption has become a major challenge at local, regional, national, and global levels due to excess population growth. The direct domestic water demand and the indirect industrial, agricultural, and environmental water needs to sustain this growth is expected to place serious strains on the currently available water resources. Water reuse and desalination technologies can provide a solution to this issue if implemented in a sustainable manner. Provision of clean water inevitably requires energy, which is currently being provided essentially by nonrenewable fossil fuels which is not a sustainable approach. This chapter discusses various options available for enhancing water supply in drought regions. Water reuse and desalination technologies have been discussed in detail. Energy needs and integration of renewable energy sources, energy recovery and process integration concepts have been discussed. Future research directions to develop energy-efficient water supply technologies are provided.

The act of ensuring freshwater is considered the most essential and basic need for humanity. Although the planet is water-rich in some terms, the freshwater sources available for human consumption and beneficial uses are very limited. Excess population growth, industrial development coupled with improving living standards have caused an unprecedented need for freshwater supplies all over the world. Regions once rich in water resources are struggling to meet the ever increasing demands in recent years. In addition, climate change and unsustainable water resource management practices have led to situation called “drought” in many regions. Water supplies in drought conditions can be addressed by taking two major approaches related to management and technology development. The management approaches include demand mitigation and supply enhancement. Demand mitigation can be done by implementing water conservation practices and by enforcing a mechanism to influence user-responsible behavior through higher water fares and other billing routes. Supply enhancement can be achieved by utilizing the methods available for water reclamation, reuse, and recycle including rain harvesting. This chapter provides a critical insight of the causes for drought and the issues caused by persistent drought conditions followed by discussion of management approaches required to maintain adequate water resources in these regions.