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The hydrophobic polymers used in membrane distillation (MD) process was prone to wetting by oil and surfactant, which hindered its widespread industrial application. In this study, an electrically conductive membrane was fabricated by coating a PTFE membrane with graphene layer, and an electric-enhanced direct contact membrane distillation system (EE-DCMD) was developed subsequently. Systematical analysis showed that the EE-DCMD system exhibited a simultaneous anti-wetting and flux-enhancing property, which overcome the trade-off between wetting resistance and water vapor permeability. A mechanistic insight into such excellent performance was proposed from the aspects of electrochemical oxidation, in-situ electro-flotation, and electrostatic repulsion. More specifically, the effect of the in-situ electro-flotation was quantified using a mechanical model based on the Gibbs adsorption equation, showing advantages over the conventional flotation pretreatment. Furthermore, an XDLVO theory coupled with a modified-Poisson-Boltzmann equation (MPB) was used to quantify the interaction energy between foulants and the charged membrane. We believe that the electrically conductive membrane has a promising potential in treating saline water with complex composition, and the proposed mechanism will pave the way for the smart design of the EE-DCMD like systems.

Membrane distillation (MD) is a promising seawater desalination technology for remote areas, although it is still limited by membrane fouling. In this study, a lab-scale direct contact membrane distillation (DCMD) system was designed for seawater desalination, operating in concentrating and non-concentrating modes to characterize the fouling process. Systematic analysis showed that scaling and biofouling are dominant fouling types in MD system, although the high temperature and salinity can inhibit the formation of biofouling layer. Biofouling can accelerate the formation of scaling, and the mixed foulants can block the membrane pores, leading to significant flux drop. With the application of high throughput sequencing, Proteobacteria, Bacteroidetes, Firmicutes and Planctomycetes were found to be the most abundant phyla. Microbial community succession was revealed during biofilm formation, in which Proteobacteria, Planctomycetes and Bacteroidetes played important roles. Additionally, a higher abundance of Firmicutes was observed in concentrating mode, representing the selective pressure from the heating and concentrating process. Finally, a three-phase model was suggested to describe the fouling process, which may reveal the vital fouling stage, and assist the development of anti-biofouling approaches in MD operation.

This paper proposes to investigate the performance of a path planning method for a data acquisition task using multiple cooperative underwater vehicles (MAUV). We present a multiple objective path planning (MOPP) method to find the optimal solutions for the data acquisition task with certain constraints. This method is based on an Interval Programming (IvP) algorithm introduced in [1] for representing and optimizing over multiple competing objective functions. We made improvements to deal with multiple objective optimizations in the underwater environment. The MOPP model is built to respect with different behaviors. Preliminary simulation trials based on two simplified scenarios have been carried out. The results show that the cooperative data acquisition task could be finished satisfactorily and safety.

Underwater Wireless Sensor Networks (UWSNs) are getting growing interest because of wide-range applications. However, the underwater acoustic communication technology is constrained by the nodes' continuous movement, limited communication bandwidth and node energy, which bring great challenges to UWSNs. In order to handle these challenges and to achieve an efficient energy consumption, many researches have been carried. A significant problem in Underwater Wireless Sensor Networks (UWSNs) is the difficulty of energy limit. This paper proposes an AUV-aided acoustic communication protocol, namely AA-RP (AUV-Aided Routing Method Integrated Path Planning), which integrates the AUV's dynamic path planning algorithms into the routing protocol. This integrated communication method relies on two phases: AAR (AUV-Aided Network Routing) and RAPP (Routing Aided Path Planning). AA-RP utilizes the cooperation of multi-tasks to reduce energy consumption for network and avoids hot spot and zone problem with a dynamic GN (Gateway Node) schemes. In order to evaluate the performance of the proposed method, we make the simulation with NS3, which contains a UAN (Underwater Acoustic Network) module. The simulation results show that the method can reduce the network energy consumption with a good delivery ratio.