Water Recovery Technology Research Articles

Comprehensive mass transport modeling technique for the cathode side of an open-cathode direct methanol fuel cell

A systematic method for the steady-state modeling of mass transport phenomena and electrochemical behavior focusing on the cathode side of a direct methanol fuel cell (DMFC) with an open-cathode design is presented and demonstrated using an experimental system. The architecture features an internal water-recovery technology that promotes back-convection of water from the cathode to the anode through a polymer electrolyte permeable membrane that includes laser-drilled holes. Eight adjustable modeling parameters are estimated from experimental data from a prototype system, and a model validation study shows that predictions of water venting rates and of cell voltage have errors better than 9% when extrapolating to conditions not used for parameter estimation. Illustrations of the use of the model include an analysis of performance at various flow rates of feed air, operating temperatures and currents, and a prediction of the effect of alternative material designs for selected cell layers. The approach serves as a paradigm for the development of general models for open-cathode active-feed DMFC systems.

Membrane processes for a sustainable industrial growth

This review gives an overview of the key results in various fields of membrane technology with special emphasis to their exploitation in sustainable industrial applications. Considerable progress has been made in short time in a number of important application areas: membrane technology and engineering for water treatment, gas separation, purification and recovery in petrochemical, chemical, pharmaceutical, electronic industry, regenerative medicine etc. The basic properties of membrane operations (generally a-thermal; simple in concept and operation; modular and easy to scale-up; with a potential for more rational utilization of raw materials and recovery and reuse; compatible to a retrofit strategy) are at the basis of their integration into industrial practice.

Membrane Condenser as a New Technology for Water Recovery from Humidified “Waste” Gaseous Streams

The potentialities of a membrane condenser for the selective recovery of evaporated wastewater from industrial gases have been investigated in the present paper. Membrane modules have been prepared and their performance has been evaluated in an artificial flue gas stream. A simulation study of the process has been carried out for predicting the membrane-based process performance. The achieved results indicate that a 20% water recovery (the amount to make the plant self-sufficient) can be achieved with temperature reductions less than 5 °C if flue gas is in common conditions (i.e., 50 °C < T < 90 °C and 90% < RH < 100%). To verify the results achieved by the simulation analysis a membrane module with microporous hydrophobic PVDF hollow fibers has been built, and its performance has been evaluated by feeding an artificial flue gas stream. The experimental results showed good agreement with the simulation ones, obtaining deviations less than 2.24%.

A Model for the Prediction of Bubble Detachment Diameters in Vapor Compression Distillation Assembly

The vapor compression distillation assembly is a phase-change water recovery technology which will reclaim water from urine, whose evaporator is a rotating container involving boiling heat transfer. The production rate of the apparatus depend on the bubble detachment diameter. In the article, based on the force equilibrium of bubble, the bubble detachment diameter formula is obtained, in which, the flow velocity along axis is neglected because it is very slow. The formula is very significant to the design of the apparatus and other relative apparatus.

Coal power plant flue gas waste heat and water recovery

An advanced waste heat and water recovery technology has been developed to extract a portion of the water vapor and its latent heat from flue gases based on a nanoporous ceramic membrane capillary condensation separation mechanism. The recovered water is of high quality and mineral free, therefore can be used as supplemental makeup water for almost all industrial processes. The technology was first developed and proven at industrial demonstration scale for gas-fired package boilers, and already commercialized. The technology was thereafter further developed to a two-stage design tailored to coal power plant flue gas applications. The recovered water and heat can be used directly to replace power plant boiler makeup water to improve its efficiency, and any remaining recovered water can be used for flue gas desulfurization (FGD) water makeup or other plant uses. The technology will be particularly beneficial for coal-fired power plants that use high-moisture coals and/or FGD for flue gas cleanup.

Zero discharge fermentation plant design

In recent years, there has been an increasing thrust towards zero-discharge operation of waste-water treatment plants. This has been driven by increasingly stringent discharge standards, as well as financial benefits stemming from the recycling of water around such facilities. The molasses-based fermentation industry is associated with high consumption of water and a high generation of high-strength effluent, due to the widespread use of molasses feeds. Traditional biological treatment for this effluent is incapable of meeting stringent discharge and reuse standards; therefore it must be supplemented with tertiary treatment options. The main options for water recovery are reverse osmosis (RO) membrane filtration and evaporation. The main problems for these treatment options is the high energy consumption associated with their use and the requirement for pre-treatment leading up to the RO stages. This paper will compare potential treatment options for high water recovery from the high-strength effluent generated by distill-eries and yeast production plants on an economic basis, incorporating both operating costs and capital costs. Treatment options are considered for several different effluent sources. This includes a comparison of the use of both reverse osmosis and evaporation technology for water recovery on end-of-line effluent streams. The potential for a salt recycle from the end-of-line streams to pre-fermentation stages is explored as well as decolourisation of the molasses feed. This paper will also demonstrate the potential for energy integration between the biological treatment stages and the tertiary “polishing” stages. The biogas produced in the anaerobic digestion stage can be used to generate enough electricity to power the following treatment stages, while maintaining a high water recovery (>80%). This paper builds upon the work of Ryan et al. [1]. In their paper, the authors overestimated the levels of TDS reaching the RO stages. They failed to account for the ability of both the aerobic digesters and the nanofiltration treatment stages to remove TDS from the effluent. This paper then focuses on the potential for water recovery from a molasses-based fermentation plant and compares treatment technologies for this water recovery.

Anaerobic treatment as a core technology for energy, nutrients and water recovery from source-separated domestic waste(water)

Based on results of pilot scale research with source-separated black water (BW) and grey water (GW), a new sanitation concept is proposed. BW and GW are both treated in a UASB (-septic tank) for recovery of CH4 gas. Kitchen waste is added to the anaerobic BW treatment for doubling the biogas production. Post-treatment of the effluent is providing recovery of phosphorus and removal of remaining COD and nitrogen. The total energy saving of the new sanitation concept amounts to 200 MJ/year in comparison with conventional sanitation, moreover 0.14 kg P/p/year and 90 litres of potential reusable water are produced.

Integrated evaluation of a sequential membrane filtration system for recovery of bioreactor effluent during long space missions

Performance of an integrated membrane filtration system was investigated for treatment of the effluent from an aerated rotating membrane bioreactor system (ARMS). The ARMS is developed and operated at the Kennedy Space Center (KSC) as a potential technology for water recovery and recycling during long space missions. The 3 L bioreactor utilizes a rotating membrane module consisting of silastic hollow fibers for aeration and biofilm growth. Effluent from the ARMS contains high levels of dissolved inorganic solids. A sequential membrane filtration system consisting of prefiltration and reverse osmosis (RO) membranes was evaluated for treatment of the bioreactor effluent. To select an appropriate prefiltration membrane, a series of membrane screening experiments were conducted with two UF membranes (MWCO 10,000 and 50,000 Da) and a nanofiltration (NF) membrane using stirred filtration cells. In addition, integrated membrane filtration tests were conducted with the NF and RO membranes using a cross-flow membrane filtration unit. Effectiveness of the integrated membrane filtration system was evaluated in terms of flux and total solids rejection of the individual filtration steps as well as the overall system performance.

Shortcut model for water-balanced operation in fuel processor fuel cell systems

In a fuel processor, a hydrocarbon or oxygenate fuel is catalytically converted into a mixture rich in hydrogen which can be fed to a fuel cell to generate electricity. In these fuel processor fuel cell systems (FPFCs), water is recovered from the exhaust gases and recycled back into the system. We present a simple mass balance analysis based on the assumption that the off-gas leaving the system is just saturated (perfect condenser). The model results in simple expressions for the net amount of water produced, and the critical condition for water-balanced operation in FPFCs. The analysis includes the composition of the hydrocarbon or oxygenate fuel, the air-to-fuel inlet ratio, humidity, ambient temperature and pressure, and the temperature and pressure in the condenser. The analysis can be used to quickly assess under what conditions operation is critical and additional measures or alternative water recovery technologies are required. The simple analysis is in agreement with the more extensive mass balance analysis by Ahmed et al. [Water balance in a polymer electrolyte fuel cell system, J. Power Sources 112 (2002) 519–530] and shows the same dependencies of the water balance on the H/C ratio, condenser pressure, ambient temperature, etc. The analysis shows that as long as these parameters remain invariant, the actual amount of water that is used in the system is of no importance from an overall water management perspective. For instance, high steam loads in the reformer, or in the fuel cell (e.g., in case of a polyelectrolyte membrane fuel cell) do not burden the overall water balance in the least.

Evaluation of Reverse Osmosis for Electroplating Effluent Treatment

A South African developed tubular cellulose acetate reverse osmosis (RO) system from Membratek (Pty) Ltd was evaluated for the treatment of nickel rinse water and mixed electroplating effluent. Spiral wrap polyamide (DuPont) and thin film composite (FilmTec) membranes were evaluated for cadmium and chromium rinse water treatment, respectively. Preliminary laboratory results have shown that nickel rinse water should be treated economically with tubular RO. Approximately 92% of the rinse water could be recovered for reuse. The RO brine is of suitable quality for reuse in the electroplating process. Plant payback for a 5 m3/h nickel/water recovery RO plant was determined to.be 1.3 years (approximately 2 000 mg/ℓ Ni in feed). No severe membrane fouling was encountered during the investigation. However, membrane fouling can affect the process adversely and this will be studied further. Approximately 90% water, of suitable quality for reuse as rinse water in the plating process, could be recovered from mixed electroplating effluent. Effluent volume for subsequent treatment with lime was significantly reduced. It may also be possible to treat cadmium and chromium rinse waters with RO. Approximately 92% and 91% water, of suitable quality for reuse as rinse water, could be recovered with spiral wrap polyamide and thin film composite membranes, respectively. Membrane fouling was experienced during cadmium rinse water treatment. However, water flux could be restored by chemical cleaning. Very little fouling was experienced during chromium rinse water treatment. The fouling potential of the rinse waters for the membranes and subsequent cleaning procedures will be studied further. Preliminary results have shown that payback for 5 m3/h RO cadmium/water and RO chromium/water recovery plants should be 3 and 7 years, respectively. Reverse osmosis has been shown to be a very effective technology for water and chemical recovery and for effluent volume reduction. The electroplating industry causes serious pollution and wastes large volumes of water. Consequently, RO is a technology that may be applied to good effect in the electroplating industry to control pollution and to save scarce water.