An empirical determination of the whole-life cost of FO-based open-loop wastewater reclamation technologies

Abstract

Over the past 5-10 years it has become apparent that the significant energy benefit provided by forward osmosis (FO) for desalination arises only when direct recovery of the permeate product from the solution used to transfer the water through the membrane (the draw solution) is obviated. These circumstances occur specifically when wastewater purification is combined with saline water desalination. It has been suggested that, for such an "open loop" system, the FO technology offers a lower-cost water reclamation option than the conventional process based on reverse osmosis (RO). An analysis is presented of the costs incurred by this combined treatment objective. Three process schemes are considered combining the FO or RO technologies with membrane bioreactors (MBRs): MBR-RO, MBR-FO-RO and osmotic MBR (OMBR)-RO. Calculation of the normalised net present value (NPV/permeate flow) proceeded through developing a series of empirical equations based on available individual capital and operating cost data. Cost curves (cost vs. flow capacity) were generated for each option using literature MBR and RO data and making appropriate assumptions regarding the design and operation of the novel FO and OMBR technologies. Calculations revealed the MBR-FO-RO and OMBR-RO schemes to respectively offer a~20% and 30% NPV benefit over the classical MBR-RO scheme at a permeate flow of 10,000 m 3 .d-1 , provided the respective schemes are applied to high and low salinity wastewaters. Outcomes are highly sensitive to the FO or OMBR flux sustained: the relative NPV benefit (compared to the classical system) of the OMBR-RO scheme declined from 30% to~4% on halving the OMBR flux from a value of 6 L.m-2 .h-1 .

Low-pressure membrane technology for potable water filtration: true costs

“…The above outcomes are consistent both with expectations and cost analyses reported elsewhere for low-pressure membrane installations both for potable water (Campinas et al, 2021;Guo et al, 2014) and wastewater (Jalab et al, 2019). Whilst the absolute values of the labour costs are much lower than those determined for wastewater membrane plants (Qiblawey and Judd, 2019;Young et al, 2013), they none-the-less contribute more significantly to the total OPEX due largely to the relatively low energy demand of potable water membrane filtration compared with membrane bioreactors used for wastewater treatment.…”

“…The PV is a function of the CAPEX (LC) and OPEX (LO) cost contributions (Jalab et al, 2019): Annualising all scheduled OPEX, including membrane replacement, simplifies this equation:…”

Water reclamation and reuse

“…Further, this practice could still ensure that the economic activity in that region is feasible and that the groundwater aquifer is not overexploited. Jalab et al (2019) performed a whole-life cost analysis of three process schemes, MBR-RO, MBR-FO-RO, and osmotic MBR (OMBR)-RO for wastewater reclamation at a permeate flow of 10,000 m 3 /day. The MBR-FO-RO and OMBR-RO schemes offered an increased net present value benefit by 20% and 30%, respectively, compared to the MBR-RO scheme for both high-and low-salinity wastewater reclamation.…”

Techno-economic analysis of combining forward osmosis-reverse osmosis and anaerobic membrane bioreactor technologies for municipal wastewater treatment and water production

“…Reverse osmosis (RO) stands as the most used technology to produce clean water from diluted draw solutions (Awad et al, 2019;Luo et al, 2014). The combination of FO and RO is particularly interesting for open-loop seawater desalination schemes (once-through systems), where seawater is used as a draw solution and, subsequently, clean water is produced by RO from the diluted seawater (Blandin et al, 2016;Jalab et al, 2019). It is worth to mention that FO-RO system is not thermodynamically favourable when compared to sewage direct RO due to the higher osmotic pressure of the diluted seawater in comparison to municipal sewage (Shaffer et al, 2015).…”