Performance evaluation of deep eutectic solvent as a draw solute and vertical up-flow forward osmosis module for desalination of seawater.

Forward osmosis (FO) has gained prominence in recent years particularly in desalination due to its ability to operate at low or no hydraulic pressure, with relatively limited membrane fouling and high-water recovery. However, pre-treatment of seawater is required to reduce membrane fouling caused by the presence of suspended solid particles. Also, a significant area of research in forward osmosis is still finding a suitable draw solute (DS) with the ideal characteristics. In this study, a novel deep eutectic solvent (DES) draw solute was used and able to extract water after the 500% dilution of DS. This signifies it as the potential candidate for the ideal DS. A comparative study of plate and frame and vertical up-flow forward osmosis (VUF) FO modules has been evaluated to eliminate the drawbacks associated with FO in terms of membrane fouling and draw solute. In addition, the performance of a novel DES as reline (choline chloride-urea) has been tested in both the modules. In VUF module, significantly less fouling was observed than in the plate and frame module. The initial water flux in plate and frame module was 2.30 LMH with seawater (without pre-treatment) as feed. However, it dropped to 1 LMH after 26 h of run. However, initial water flux in VUF was 1.90 LMH, and it was maintained to 1.50 LMH after 89 h of run. Regeneration of draw solute was carried out using a phase separation method and it was observed that phase separation was only observed for 10% dilution of DES.

A novel concept of Vertical Up-Flow Forward Osmosis reactor: Design, performance and evaluation.

Performance of the forward osmosis (FO) process is limited due to the decline in water flux and increase in reverse salt flux. In this study, a novel Vertical Up-Flow Forward Osmosis (VUF-FO) reactor was designed and evaluated for eight different contacting patterns of feed and draw agent (DA). The best contacting pattern was compared with the basic H-shape reactor. Pulsating inlets were used for the recirculation of the feed and DA which helped in improving the performance by reducing the concentration polarization on membrane. Water flux in FO (active layer facing feed side) and PRO (active layer facing draw side) mode was 12.75 and 16.28 L/m2hr (LMH) respectively for the contacting pattern R3 and R5 after 8 h of the process. While the water flux in the H-shape reactor was 9.12 and 12.54 LMH for FO and PRO mode respectively. Diffusional behavior of water flux and reverse salt flux were also evaluated for both the FO reactors. Water flux in the H-shape reactor was declined to more than 60% from its initial value in both the modes (i.e. FO and PRO) due to the concentration polarization on membrane. Only 10% decline in water flux was observed for the VUF-FO reactor. This showed a better consistency of water flux in the VUF-FO reactor. The reverse salt flux in the VUF-FO reactor was less than 85% compared to the H-shape reactor. Therefore, a novel designed reactor improved the overall performance of FO in terms of water flux and reverse salt flux.

Physico-chemical and biological treatment strategies for converting municipal wastewater and its residue to resources.

An increase in urbanization and industrialization has not only contributed to an improvement in the lifestyle of people, but it has also contributed to a surge in the generation of wastewater. To date, conventional physico-chemical and biological treatment methods are widely used for the treatment of wastewater. However, the efficient operation of these systems require substantial operation and maintenance costs, and the application of novel technologies for the treatment and disposal of sludge/residues. This review paper focuses on the application of different treatment options such as chemical, catalyst-based, thermochemical and biological processes for wastewater or sludge treatment and membrane-based technologies (i.e. pressure-driven and non-pressure driven) for the separation of the recovered products from wastewater and its residues. As evident from the literature, a wide variety of treatment and resource recovery options are possible, both from wastewater and its residues; however, the lack of planning and selecting the most appropriate design (treatment train) to scale up from pilot to the field scale has limited its practical application. The economic feasibility of the selected technologies was critically analyzed and the future research prospects of resource recovery from wastewater have been outlined in this review.

Technologies for the recovery of nutrients, water and energy from human urine: A review.

The global demand for a constant supply of fertilizer is increasing with the booming of the population. Nowadays more focus is given to the recovery and reuse of the nutrients rather than synthesis of the fertilizer from chemicals. Human urine is the best available resource for the primary macronutrients (Nitrogen, Phosphorus and Potassium) for the fertilizer as it contains 10-12 g/L nitrogen, 0.1-0.5 g/L phosphorous and 1.0-2.0 g/L potassium. For the recovery of these nutrients from human urine, various technologies are available which requires source separation and treatment. . In this review, a wide range of the technologies for the treatment of source-separated human urine are covered and discussed in detail. This review has categorized the technologies based on the recovery of nutrients, energy, and water from human urine. Among the various technologies available, Bio-electrochemical technologies are environmental friendly and recovers energy along with the nutrients. Forward Osmosis is the best available technology for the water recovery and for concentrating the nutrients in urine, without or minimal consumption of energy. However, experimental work in this technology is at its prior stage. A single technology is still not sufficient to recover nutrients, water and energy. Therefore, integration of two or more technologies seems essential.