Value propositions of the water footprint concept for sustainable water utilities

The water footprint concept has been used by agricultural, commercial, and industrial water users to measure and report their water consumption, assess the magnitude of potential environmental impacts arising from this consumption, and identify opportunities for risk mitigation strategies that promote sustainable water use. However, water and wastewater utilities have not studied and documented the application of this concept in the same manner that other industries have. This article summarizes the growing body of information on the water footprint concept and the opportunities for integrating the concept into water utility planning efforts as a broader means of achieving and maintaining sustainable communities. The application of the water footprint concept for capital improvement planning, water resources decision-making, operational benchmarking, and stakeholder communications is discussed, as is how the methodology, developed by the International Organization for Standardization, can be used for a water utility

Current and Emerging Techniques for High-Pressure Membrane Integrity Testing

Ideally, pressure driven membrane processes used in wastewater treatment such as reverse osmosis and nanofiltration should provide a complete physical barrier to the passage of pathogens such as enteric viruses. In reality, manufacturing imperfections combined with membrane ageing and damage can result in breaches as small as 20 to 30 nm in diameter, sufficient to allow enteric viruses to contaminate the treated water and compromise public health. In addition to continuous monitoring, frequent demonstration of the integrity of membranes is required to provide assurance that the barrier to the passage of such contaminants is intact. Existing membrane integrity monitoring systems, however, are limited and health regulators typically credit high-pressure membrane systems with only 2 log10 virus rejection, well below their capability. A reliable real-time method that can recognize the true rejection potential of membrane systems greater than 4 log10 has not yet been established. This review provides a critical evaluation of the current methods of integrity monitoring and identifies novel approaches that have the potential to provide accurate, representative virus removal efficiency estimates

Energy Efficient Strategies and Renewable Energy Technologies for Desalination

ABSTRACT Energy is often the most significant factor in the affordability and sustainability of treating various different source waters with reverse osmosis membrane facilities. More than 33% of the cost to produce water using reverse osmosis (RO) technology is attributed to electrical demands. The largest energy-consuming component of the overall treatment are the high pressure pumps required to feed water to the process. Because of the high energy burden and production of greenhouse gas (GHG) emissions, renewable energy is being increasingly considered for desalination projects. The selection of the appropriate renewable energy resource depends on several factors, including plant size, feed water salinity, remoteness, availability of grid electricity, technical infrastructure, and the type and potential of the local renewable energy resource. The cost of desalination with renewable energy resources, as opposed to desalination with conventional energy sources, can be an important alternative to consider when reduced environmental impact and lower gas emissions are required. Considering the proposed climate protection targets that have been set and the strong environmental drivers for lowered energy usage, future water desalination and advanced water treatment systems around the world could be increasingly powered by renewable energy resources. In addition to renewables, energy optimization/minimization is deemed critical to desalting resource management. Methods employed include enhanced system design, high efficiency pumping, energy recovery devices and use of advanced membrane materials

Galerkin difference methods and applications to wave equations

May 2019School of ScienceThe Galerkin Difference (GD) method, a finite element method built using standard Galerkin projection but employing nonstandard basis functions, was originally developed for one space dimension in [J. W. Banks and T. Hagstrom, On Galerkin difference methods, J. Comput. Phys., 313 (2016), pp. 310-327]. The C^0 basis was derived by considering standard piecewise continuous polynomial interpolation. The resulting GD approximations were found to have excellent properties both in terms of their accuracy and computational efficiency. Here the method is extended to two space dimensions and to higher derivative operators.Additionally, we further extend GD by considering higher derivative operators, such as those commonly found in beam or plate models of solid mechanics. These higher-order PDEs necessitate higher continuity basis functions. To derive this smoother basis, we introduce the Difference Spline, and subsequently the d-Difference Spline, which is a locally constructed C^1 (C^d) polynomial interpolant using only discrete data at p + 1 consecutive grid points. We show that the D-1-Spline interpolant is a p-th order accurate approximation, and basis functions associated with each grid point are derived. The basis is then used in a standard weak-form finite element approximation of the PDEs, and classical finite element theory shows that the method is p-th order accurate in the L_2 norm. Numerical convergence studies on the Euler-Bernoulli Beam and the Kirchhoff-Love Plate are preformed and verify the theory.To reach two space dimensions, a tensor product construction is leveraged. Theoretical and computational evidence shows the method behaves as expected for the acoustic wave equation. For the elastic wave equation, the approximations are found to be at least as accurate as predicted. In the special case of a free surface the scheme is more accurate than expected, exhibiting unexpected superconvergence. Extension to curvilinear mapped grids is also considered for acoustics. In all cases, the use of a tensor product construction allows for efficient solution of the linear system involving the mass matrix, which implies optimal linear time solutions with respect to the number of degrees of freedom.Ph