Environmental sustainability of forward osmosis: The role of draw solute and its management

Forward osmosis (FO) is a promising technology for the treatment of complex water and wastewater streams. Studies around FO are focusing on identifying potential applications and on overcoming its technological limitations. Another important aspect to be addressed is the environmental sustainability of FO. With the aim to partially fill this gap, this study presents a life cycle analysis (LCA) of a potential full-scale FO system. From a purely environmental standpoint, results suggest that significantly higher impacts would be associated with the deployment of thermolytic, organic, and fertilizer-based draw solutes, compared to more accessible inorganic compounds. The influent draw osmotic pressure in FO influences the design of the real-scale filtration system and in turn its environmental sustainability. In systems combining FO with a pressure-driven membrane process to recover the draw solute (reverse osmosis or nanofiltration), the environmental sustainability is governed by a trade-off between the energy required by the regeneration step and the draw solution management. With the deployment of environmentally sustainable draw solutes (e.g., NaCl, Na2SO4), the impacts of the FO-based coupled system are almost completely associated to the energy required to run the downstream recovery step. On the contrary, the management of the draw solution, i.e., its replacement and the required additions due to potential losses during the filtration cycles, plays a dominant role in the environmental burdens associated with FO-based systems exploiting less sustainable draw solute, such as MgCl2

Organic fouling in forward osmosis: Governing factors and a direct comparison with membrane filtration driven by hydraulic pressure

The fouling behavior of osmotically-driven forward osmosis (FO) is widely believed to be superior with respect to hydraulic pressure-driven membrane applications, based on a number of experiments reported in the literature. However, experimental confounders often exist, preventing fair comparison between the different processes, one being the deployment of non-comparable membranes. This study systematically investigates the conditions influencing organic fouling in FO and compares the behavior in FO and in a hydraulic pressure-driven process, under equivalent conditions. The same state-of-the-art polyamide FO membranes were used in the tests, which were run with real feed solutions and under varying conditions to observe the effect of initial flux, draw solution, and feed ionic composition. The results suggest that initial flux and calcium have the strongest influence on the extent of flux decline and recovery. The influence of different draw solutions in FO becomes apparent when the flux is relatively low. Analysis of the fouling indices and of the effective driving force, as well as direct observation of membranes following fouling, support the conclusion that the fouling behavior of the FO process is not necessarily better compared to an analogous hydraulic pressure-driven one, especially under relevant operational conditions and when the two processes work with similar fluxes

A proxy cost model for tramway services

In this paper, we build a proxy cost model for tramway services. we estimate separately: (i) transport services production costs; (ii) infrastructure costs; (iii) maintenance costs; (iv) administrative and general costs and (v) the cost of capital. we apply the proposed methodology to estimate the standard cost of italian tramway services. detailed data about costs, technical and environmental characteristics were collected by means of questionnaires sent to italian companies providing 100% of tramway services in 2012. we perform a simulation study in order to highlight the marginal impact of efficiency gains obtained by manipulating cost-driving variables both under the control of the operators (trains and drivers productivity) and of the local authority who assigns the service (number of train revenue kilometers (trK) assigned within the service contract, average fleet age). the simulations show how the local authority should allocate extra resources if it wants to increase the quality-quantity mix of tramway services. our results might help the decision-maker to define the maximum economic compensation (auction base) in competitive tendering procedures or a benchmark for the bargaining with the local monopolist

Regulation of monocyte cell fate by blood vessels mediated by Notch signalling

A population of monocytes, known as Ly6C(lo) monocytes, patrol blood vessels by crawling along the vascular endothelium. Here we show that endothelial cells control their origin through Notch signalling. Using combinations of conditional genetic deletion strategies and cell-fate tracking experiments we show that Notch2 regulates conversion of Ly6C(hi) monocytes into Ly6C(lo) monocytes in vivo and in vitro, thereby regulating monocyte cell fate under steady-state conditions. This process is controlled by Notch ligand delta-like 1 (Dll1) expressed by a population of endothelial cells that constitute distinct vascular niches in the bone marrow and spleen in vivo, while culture on recombinant DLL1 induces monocyte conversion in vitro. Thus, blood vessels regulate monocyte conversion, a form of committed myeloid cell fate regulation

Regulation of monocyte cell fate by blood vessels mediated by Notch signalling

A population of monocytes, known as Ly6Clo monocytes, patrol blood vessels by crawling along the vascular endothelium. Here we show that endothelial cells control their origin through Notch signalling. Using combinations of conditional genetic deletion strategies and cell-fate tracking experiments we show that Notch2 regulates conversion of Ly6Chi monocytes into Ly6Clo monocytes in vivo and in vitro, thereby regulating monocyte cell fate under steady-state conditions. This process is controlled by Notch ligand delta-like 1 (Dll1) expressed by a population of endothelial cells that constitute distinct vascular niches in the bone marrow and spleen in vivo, while culture on recombinant DLL1 induces monocyte conversion in vitro. Thus, blood vessels regulate monocyte conversion, a form of committed myeloid cell fate regulation