Designing water supplies: Optimizing drinking water composition for maximum economic benefit.

It is possible to optimize drinking water composition based on a valuation of the impacts of changed water quality. This paper introduces a method for assessing the potential for designing an optimum drinking water composition by the use of membrane desalination and remineralization. The method includes modeling of possible water quality blends and an evaluation of corrosion indices. Based on concentration-response relationships a range of impacts on public health, material lifetimes and consumption of soap have been valued for Perth, Western Australia and Copenhagen, Denmark. In addition to water quality aspects, costs of water production, fresh water abstraction and CO(2)-emissions are integrated into a holistic economic assessment of the optimum share of desalinated water in water supplies. Results show that carefully designed desalination post-treatment can have net benefits up to €0.3 ± 0.2 per delivered m(3) for Perth and €0.4(±0.2) for Copenhagen. Costs of remineralization and green house gas emission mitigation are minor when compared to the potential benefits of an optimum water composition. Finally, a set of optimum water quality criteria is proposed for the guidance of water supply planning and management.

A sequential zero valent iron and aerobic biodegradation treatment system for nitrobenzene.

The remediation of nitroaromatic contaminated groundwater is sometimes difficult because nitroaromatic compounds are resistant to biodegradation and, when they do transform, the degradation of the products may also be incomplete. A simple nitroaromatic compound, nitrobenzene, was chosen to assess the feasibility of an in situ multi-zone treatment system at the laboratory scale. The proposed treatment system consists of a zero valent granular iron zone to reduce nitrobenzene to aniline, followed by a passive oxygen release zone for the aerobic biodegradation of the aniline daughter product using pristine aquifer material from Canadian Forces Base (CFB) Borden, Ontario, as an initial microbial source. In laboratory batch experiments, nitrobenzene was found to reduce quickly in the presence of granular iron forming aniline, which was not further degraded but remained partially sorbed onto the granular iron surface. Aniline was found to be readily biodegraded with little metabolic lag under aerobic conditions using the pristine aquifer material. A sequential column experiment, containing a granular iron reducing zone and an aerobic biodegradation zone, successively degraded nitrobenzene and then aniline to below detection limits (0.5 microM) without any noticeable reduction in hydraulic conductivity from biofouling, or through the formation of precipitates.

Rigorous uncertainty assessment in contaminant transport inverse modelling: a case study of fluoride diffusion through clay liners.

Inverse methods used in assessing landfill liner design have not yet taken advantage of current developments in inverse procedures. Here, a method for inverting contaminant transport models is presented including a general error model and procedures for differentially weighted multiple response regression. General error models are employed in cases where the residuals are heteroscedastic and correlated, and lead to valid inference on model parameter and predictive uncertainty. The Shuffled Complex Evolution algorithm is used to optimise model parameters. Model parameter uncertainty is assessed by exploring the posterior probability distribution with the Metropolis algorithm, a Markov chain Monte Carlo sampling method. The inverse method is applied to simultaneously determine the sorption and diffusion parameters from laboratory diffusion cell experiments. In these experiments, fluoride migration through kaolin clays was measured by sampling the source and collector cells over time. To uniquely determine the transport model parameters, it was necessary to simultaneously fit the observed data from two independent diffusion cell experiments with different initial concentrations. The jointly fitted transport model parameters compared well with those fitted to independent batch experiments.