A novel membrane distillation-thermophilic bioreactor system: Biological stability and trace organic compound removal

The removal of trace organic compounds (TrOCs) by a novel membrane distillation-thermophilic bioreactor (MDBR) system was examined. Salinity build-up and the thermophilic conditions to some extent adversely impacted the performance of the bioreactor, particularly the removal of total nitrogen and recalcitrant TrOCs. While most TrOCs were well removed by the thermophilic bioreactor, compounds containing electron withdrawing functional groups in their molecular structure were recalcitrant to biological treatment and their removal efficiency by the thermophilic bioreactor was low (0-53%). However, the overall performance of the novel MDBR system with respect to the removal of total organic carbon, total nitrogen, and TrOCs was high and was not significantly affected by the conditions of the bioreactor. All TrOCs investigated here were highly removed (>95%) by the MDBR system. Biodegradation, sludge adsorption, and rejection by MD contribute to the removal of TrOCs by MDBR treatment. © 2014

Evaluating energy consumption of air gap membrane distillation for seawater desalination at pilot scale level

This study aimed to optimise an air gap membrane distillation (AGMD) system for seawater desalination with respect to distillate production as well as thermal and electrical energy consumption. Pilot evaluation data shows a notable influence of evaporator inlet temperature and water circulation rate on process performance. An increase in both distillate production rate and energy efficiency could be obtained by increasing the evaporator inlet temperature. On the other hand, there was a trade-off between the distillate production rate and energy efficiency when the water circulation rate varied. Increasing the water circulation rate resulted in an improvement in the distillate production rate, but also an increase in both specific thermal and electrical energy consumption. Given the small driving force used in the pilot AGMD, discernible impact of feed salinity on process performance could be observed, while the effects of temperature and concentration polarisation were small. At the optimum operating conditions identified in this study, a stable AGMD operation for seawater desalination could be achieved with specific thermal and electrical energy consumption of 90 and 0.13 kW h/m3, respectively. These values demonstrate the commercial viability of AGMD for small-scale and off-grid seawater desalination where solar thermal or low-grade heat sources are readily available

Scaling control during membrane distillation of coal seam gas reverse osmosis brine

We systematically assess the efficiency of chemical cleaning and report a simple but elegant approach to control scaling during membrane distillation (MD) of brine from reverse osmosis (RO) treatment of coal seam gas (CSG) produced water. Results reported here show that increased feed water salinity and the permeation of CO2 from the feed solution resulted in only a small and gradual decrease in water flux. On the other hand, the precipitation of sparingly soluble salts on the membrane at high water recovery (\u3e70%) led to a significant flux decline. Among the three chemical cleaning agents investigated, a reverse osmosis scale cleaning agent (denoted as MC3) was the most effective at restoring the water flux; however, MC3 cleaning was not able to completely remove scale deposits from the membrane and restore its surface hydrophobicity to the original value because of the complexation of scalants with CSG RO brine. The remaining scalants (i.e., silicates) reduced the membrane surface hydrophobicity and could possibly enhance concentration polarisation and act as seeding for further scale formation. Thus, a gradual decrease in MD performance with respect to both water flux and salt leakage was observed after each MC3 cleaning cycle. It was noted that the chemical cleaning agents themselves did not alter the hydrophobicity of the membrane; thus, the gradual decline in MD performance was attributed to the remaining scale deposits on the membrane after each cleaning cycle. Results reported here highlight the need to prevent membrane scaling and only use chemical cleaning as the last resort during MD treatment of CSG RO brine. Moreover, membrane scaling could be prevented by reducing concentration polarisation via limiting feed temperature and thus water flux. MD treatment of CSG RO brine with up to 80% water recovery without any observable membrane scaling was achieved at the feed temperature and the water flux of 35°C and 10L/m2h, respectively

Membrane Bioreactor Pretreatment of High-Salinity O&G Produced Water

Produced water (PW) from oil and gas production contains variable constituents that are difficult to remove with conventional treatment processes. The focus of this study was to explore the long-term performance of a membrane bioreactor (MBR) for the removal of organic constituents from PW and how performance and microbial community composition are affected by progressively increasing salinity and introduction of PW from different shale basins around the United States. Dissolved organic carbon removal from the PW remained consistent throughout the study, averaging 86% from the Denver-Julesburg basin PW and 66% removal from the Permian basin PW. Surfactant removal was less consistent, showing 87% removal of poly(ethylene glycols) (PEGs) at a total dissolved solid (TDS) concentration of 40 g/L but only 58% removal at a TDS concentration of 100 g/L. Diversity in the microbial community decreased during reactor establishment but increased at TDS concentrations above 80 g/L. The results of this study suggest that MBRs can be effective PW pretreatment processes even at high salinities

Innovation and the public sector

Brine management is a major bottleneck for coal seam gas (CSG) production in Australia. This study investigated the concentration of CSG reverse osmosis (RO) brine using a pilot membrane distillation (MD). The system was equipped with a novel spiral-wound air gap membrane distillation (AGMD) module. By operating the pilot MD system at low feed temperature and a small temperature gradient, a stable distillate production rate could be maintained. The resulting low permeate flux can be offset by a high packing density of the spiral-wound membrane module. Here, using a module with diameter, height, and total membrane surface area of 0.4 m, 0.5 m, and 7.2 m2, respectively, the pilot MD system sustainably achieved 80% water recovery and produced 10 L/h of distillate from CSG RO brine. Overall, 95% water recovery could be obtained from CSG produced water for beneficial uses by a combination of RO and AGMD without any observable membrane scaling. A preliminary thermal energy demand analysis suggests that if installed in New South Wales (Australia), 1 ha of flat-plate solar thermal collector arrays could provide sufficient thermal energy to treat 472 m3/day (2970 bbl/day) of CSG produced water using the proposed RO/AGMD treatment train

Net Zero Urban Water from Concept to Applications: Integrating Natural, Built, and Social Systems for Responsive and Adaptive Solutions

Innovation in urban water systems is required to address drivers of change across natural, built, and social systems, including climate change, economic development, and aged infrastructure. Water systems are complex socio-technical systems that interact with biophysical systems to supply and reclaim water. We present a vision for enhancing urban water system resilience through a net zero urban water (NZUW) approach, which meets the needs of a given community with a locally available and sustainable water supply, without detriment to interconnected systems or long-term water supply. NZUW is an integrative approach with progressive targets assessed using a quantitative framework to expand adaptive and responsive solutions for urban water self-sufficiency. Decision makers can use NZUW to understand trade-offs between future interventions to urban water systems across spatial and temporal scales. We present the overall NZUW approach, drivers of change, applications, and research gaps

Net Zero Urban Water from Concept to Applications: Integrating Natural, Built, and Social Systems for Responsive and Adaptive Solutions

Innovation in urban water systems is required to address drivers of change across natural, built, and social systems, including climate change, economic development, and aged infrastructure. Water systems are complex socio-technical systems that interact with biophysical systems to supply and reclaim water. We present a vision for enhancing urban water system resilience through a net zero urban water (NZUW) approach, which meets the needs of a given community with a locally available and sustainable water supply, without detriment to interconnected systems or long-term water supply. NZUW is an integrative approach with progressive targets assessed using a quantitative framework to expand adaptive and responsive solutions for urban water self-sufficiency. Decision makers can use NZUW to understand trade-offs between future interventions to urban water systems across spatial and temporal scales. We present the overall NZUW approach, drivers of change, applications, and research gaps