Reducing Magnesium within Seawater Used in Mineral Processing to Improve Water Recovery and Rheological Properties When Dewatering Clay-Based Tailings

In areas where access to water for mineral processing is limited, the direct use of seawater in processing has been considered as an alternative to the expense of its desalination. However, efficient flotation of copper sulfides from non-valuable phases is best achieved at a pH > 10.5, and raising the pH of seawater leads to magnesium precipitates that adversely affect subsequent tailings dewatering. Seawater pre-treatment with lime can precipitate the majority of magnesium present, with these solids then being removed by filtration. To understand how such treatment may aid tailings dewatering, treated seawater (TSw) was mixed with raw seawater (Rsw) at different ratios, analyzing the impact on the flocculated settling rate, aggregate size as measured by focused beam reflectance measurement (FBRM), and vane yield stress for two synthetic clay-based tailings. A higher proportion of Tsw (10 mg/L Mg2+) led to larger aggregates and higher settling rates at a fixed dosage, with FBRM suggesting that higher calcium concentrations in Tsw may also favor fines coagulation. The yield stress of concentrated suspensions formed after flocculation decreased with higher proportions of Tsw, a consequence of lower flocculant demand and the reduced presence of precipitates; while the latter is a minor phase by mass, their high impact on rheology reflects a small particle size. Reducing magnesium concentrations in seawater in advance of use in processing offers advantages in the water return from thickening and subsequent underflow transport. However, this may not require complete removal, with blending Tsw and Rsw an option to obtain acceptable industrial performance.

Murray-Darling Basin Plan: Case Study in Market-Based Approach to Water Sharing in Australia

The Murray-Darling Basin (MDB) is an area in southeastern Australia that has the largest and most regulated river system in the country. Historically, it has been an area of conflict over water resources, with efforts to bring the different states together to negotiate water sharing since the early 1900s. In the 20th century, the focus of water policy was predominantly on water supply infrastructure: building large-scale dam storages, weirs, and other irrigation region infrastructure. However, increasing problems with both water quality and quantity from the 1970s onwards—such as acid sulphate soils, salinity, declines in vegetation health, and species loss—meant that more attention was turned to water demand management options. These included establishing formal water markets, trade liberalization, and water extraction caps. The National Water Initiative (2004) and the Water Act (2007) laid the groundwork in unbundling water and land ownership and created the Murray-Darling Basin Authority (MDBA). The MDBA was tasked with developing the MDB Plan (Basin Plan 2012) to readjust the balance between consumptive water use and the environment. The Basin Plan when implemented in 2012 aimed to return up to one third of consumptive water extraction to environmental use, making it one of the biggest reallocations of water to the environment in the world. It has predominantly used market-based approaches to do so. However, conflict over water sharing has remained a dominant feature of MDB water reform. Self-interest among states and irrigation interests have impacted environmental water recovery methods, resource expenditure, and allocation—subsequently weakening both the Basin Plan and water policy in general. Given current policy developments, there is real danger of targets not being met, and environmental sustainability being continually compromised. The ongoing issues of drought, climate change, and readdressing First Nations access to—and ownership of—water have emphasized distributional issues in water sharing. It is clear also that the Basin Plan has been wrongly blamed and misattributed for ongoing rural community declines, with current amendments and reductions in water reallocation targets a result of this. What is clear is that the Basin Plan is currently not the fully sustainable solution for water sharing that it set out to be. It will need to continually evolve, along with various institutions to support water governance and rural community economic development in general, to address existing overallocation and future climate challenges. The challenges of equity, rural community development, and distributional fairness lie firmly in the sphere of strong governance, high-quality data, and first-best economic and scientific policies.

Preparation of ECTFE Porous Membrane for Dehumidification of Gaseous Streams through Membrane Condenser

Due to the good hydrophobicity and chemical resistance of poly(ethylene trifluoroethylene) (ECTFE), it has been an attractive potential material for microfiltration, membrane distillation and more. However, few porous hydrophobic ECTFE membranes were prepared by thermally induced phase separation (TIPS) for membrane condenser applications. In this work, the diluent, di-n-octyl phthalate (DnOP), was selected to prepare the dope solutions. The calculated Hassen solubility parameter indicated that ECTFE has good compatibility with DnOP. The corresponding thermodynamic phase diagram was established, and it has been mutually verified with the bi-continuous structure observed in the SEM images. At 30 wt% ECTFE, the surface contact angle and liquid entry pressure reach their maximum values of 139.5° and 0.71 MPa, respectively. In addition, some other basic membrane properties, such as pore size, porosity, and mechanical properties, were determined. Finally, the prepared ECTFE membranes were tested using a homemade membrane condenser setup. When the polymer content is 30 wt%, the corresponding results are better; the water recovery and condensed water yield is 17.6% and 1.86 kg m−2 h−1, respectively.

Water Recovery from Bioreactor Mixed Liquors Using Forward Osmosis with Polyelectrolyte Draw Solutions

This paper reports on the use of forward osmosis (FO) with polyelectrolyte draw solutions to recover water from bioreactor mixed liquors. The work was motivated by the need for new regenerative water purification technologies to enable long-duration space missions. Osmotic membrane bioreactors may be an option for water and nutrient recovery in space if they can attain high water flux and reverse solute flux selectivity (RSFS), which quantifies the mass of permeated water per mass of draw solute that has diffused from the draw solution into a bioreactor. Water flux was measured in a direct flow system using wastewater from a municipal wastewater treatment plant and draw solutions prepared with two polyelectrolytes at different concentrations. The direct flow tests displayed a high initial flux (>10 L/m2/h) that decreased rapidly as solids accumulated on the feed side of the membrane. A test with deionized water as the feed revealed a small mass of polyelectrolyte crossover from the draw solution to the feed, yielding an RSFS of 80. Crossflow filtration experiments demonstrated that steady state flux above 2 L/m2·h could be maintained for 70 h following an initial flux decline due to the formation of a foulant cake layer. This study established that FO could be feasible for regenerative water purification from bioreactors. By utilizing a polyelectrolyte draw solute with high RSFS, we expect to overcome the need for draw solute replenishment. This would be a major step towards sustainable operation in long-duration space missions.

Soil water deficit and recovery under different vegetation types on the Chinese Loess Plateau

Characterizing soil water content (SWC) dynamics is a prerequisite for conducting sustainable vegetation restoration on the Chinese Loess Plateau. However, quantifying the variations of the SWC in the deep soil layers remains a challenge because of the different driving factors and the complexity of surface processes. In this study, SWC in 0–10 m of artificial forestlands (AF), apple orchard (AO), native forestland (NF), farmland (maize; FL), and native grassland (NG) were monitored during 2019–2020. The deficit size (DS) and recovery index (RI) were used to explore the effects of vegetation types on SWC. The results showed that the SWCs of forestlands were significantly lower than the SWC of native grassland (12.32%) and tree species significantly affected the SWC. The monthly DS values in forestlands were negative, while those of FL were positive. The DS value in 0-10 m and predictive values below 10 m were negative of forestlands. Thus, tree planting may have consumed soil water at a depth of > 10 m. During the investigation period, soil water was restored in 0–1 m with the positive RI values. In addition, artificial forestlands showed good performance in deep soil water recovery. Canopy density was the controlling factor for soil water restoration. Our results demonstrated that the current afforestation mode used more soil water but was conducive to deep soil water conservation. Therefore, reasonable adjustments should be made according to the local soil and water resources for future vegetation selection and management.

Design suggestions on modified self-sustainable space toilet

The present research investigates the design of compact and lightweight waste collection system (WCS) for interplanetary missions such as Mars, and the Moon as well as the space with the required features of NASA’s lunar loo challenge (released date: 25th June, 2020). Existing space toilets’ WCS store waste in small plastic bags and these bags are thrown in the space which increases the space junk. If these WCS are used on planets, they could pollute the planets. The newly designed—unisex and self-sustainable space toilet meets its objective of intimacy and warmth for the astronauts as it is equipped with all essential features such as (a) the basin for vomit collection, (b) the rotating waste storage based on the mechanism of artificial gravity, and (c) the noiseless bellow pump for air flow flushing system (AFFS). The WCS is designed for the storage of urine, faeces, vomit, diarrhoea, and menses. In the first half of the research article, the focus is kept on improving self-sustainability of the present WCS. In the second half of the present investigation analyses are done for multiphase flows of the CFD analysis in ANSYS fluent to simulate the flow of air through the nozzle provided with (a) the seat, (b) the urine funnel, and (c) the basin for air flow flushing system (AFFS). The design of the present self-sustainable space toilet proposed herewith is justified suitable for different gravitational conditions such as (a) Mars (3.721 m/s2), (b) the Moon (1.62 m/s2), and (c) the zero—or microgravity i.e., the space gravity. The proposed solar-operated WCS could be integrated to function with (a) water recovery and management (WRM) system, (b) the inbuilt composting unit, and (c) the bioregenerative life support system (BLSS). Furthermore, the assessment of the required electrical energy derived from the solar energy (harnessed using efficient solar photovoltaic (PV) modules) is conceptualized for the effective functioning of the present self-sustainable WCS. Article highlights The present investigation explores into the design of lightweight and compact WCS for interplanetary missions such as Mars and the Moon, as well as space missions with the functionality listed by NASA's lunar toilet competition (released date: 25th June, 2020). The actual space toilets, which are used on the International Space Station (ISS), are not designed to withstand varying gravity circumstances. The new advanced—unisex and self-sustaining space toilet achieves its goal of intimacy and warmth for astronauts by including all necessary features such as (a) a vomit collection basin, (b) rotating waste storage based on artificial gravity mechanism, and (c) a noiseless bellow pump for air flow flushing system (AFFS).