Development of a hybrid technology for treating recalcitrant water contaminants: assessing e-beam potential.

Manufacture is faced with the escalating challenges of resource limitation, conservation of water and the treatment of waste, whilst attempting to reduce its carbon foot-print. There is increasing realisation within industry that it is a long way from achieving the efficiency of natural systems where resources such as water, metals and organics are apparently effortlessly recycled or transformed to clean energy. This is challenging enough but it is even more daunting with the realisation that end-of-pipe industrial effluent from key manufacturing processes, such as metal working and plating, and landfill leachate are chemically mixed with high concentrations, are toxic and temporally fluctuate enormously in terms chemical composition. Until now such effluents have been considered to be significant environmental problems, costly to deal with and reliant on high capital and energy demanding technologies, such as reverse osmosis and ultra-filtration. However, with climate change and increasing pressure on natural resources industry's attitude has changed with the drive now on resource recovery and treatment on site, in order to reduce the carbon footprint associated with transportation. A growing concern is the increasing realisation that current wastewater technology procedures aimed at end-of-pipe recovery from recalcitrant effluent are all energy demanding and inefficient. This requires radical new thinking in an important but neglected area.

The objective of this study is to develop new approaches and in particular test novel technological combinations (biocatalysis, zero valent nano-Fe [nZVI] and electron beam accelerators) for treating recalcitrant and chemically mixed industrial waste waters. The primary focus is to reduce the energy demand of the developed process and to harmonise the complementary technologies to sustainably degrade the organic component and precipitate, immobilise and enable metal recovery, whilst recovering the water. Chemically mixed wastewater and chlorine contaminated ground will be assessed for treatability by exploiting microbes able to biotransform such contaminants. This step will remove the readily degradable component of the effluent leaving the recalcitrant residues, that will be transferred to subsequent treatment exposures including addition of zero valent nano-Fe (nZVI). This is a highly reactive step, catalysing the chemical disintegration of recalcitrant residues, including large polymers and chemical complexes, so making them more conducive to a final biodegradation step. Biologically pre-treated recalcitrant effluent residues will also be treated by exposure to the e-beam, leading to radiolysis, production of H+ and OH radicals, resulting in vigorous reducing and oxidations conditions, and the organic becoming more bioavailable to microbiological treatment. The novel combination of nZVI with the e-beam, with a final biodegradation step, we believe will lead to the destruction of most recalcitrant residues. Parallel lab tests will be established to determine the effectiveness of all three treatments (microbiological, nZVI and e-beam) on the chemical state of the metals, immobilisation and recovery by precipitation.

A broad range of waste waters will be investigated, both end-of-pipe industrial and contaminated ground-waters. A key issue will be the feasibility of converting developed technologies for transforming the organic component to useful products and recovery of the metals are feasible, scaleable and can with some development be commercialised.

The primary focus of this study will be the e-beam component, in particular assessment of procedures for improving its efficiency, lowering its energy requirement since will be a key requirement in order to being commercially viable. We will also determine the most effective microbial cells at the end of the biodegradative component of the treatment.

Economics- The longer term aim of this research is to deliver an effective sustainable technology/treatment train for treating hazardous, chemically mixed recalcitrant industrial waste waters and from this achieve complete resource recovery, including the water, metals and organics. To date there has been little technological development in terms of establishing more innovative sustainable approaches for treating such problematic waste waters, generated by many industrial processes (metal working, pharmaceuticals, dye, petroleum, paper). However, what has changed most recently is the realisation that many of the chemical constituents of waste waters, in particularly metals, are resources of increasing market value, in particular the metals. Added to this is the fact that under the Water Framework Directive there is a legal obligation for the UK to meet specific standards for end-of-pipe contaminant release. If these are not met by the polluter, then they are liable to have to pay heavy fines. A significant impact of this technology will be the saving made by recovering the metals, transformation of the organic to value products (bio-energy as methane and production of bioplastics) and water recycling on site. These together could represent an enormous saving on production costs for industry and environmental fines. It represents a technology which would have an enormous international market.

An additional potential economic impact is the inclusion of a recently patented (by Bristol) method for immobilising nano-scale iron and its application. If these technologies prove to be effective, they could have enormous economic and environmental impact.

Environment/Society- The key beneficiary of the proposal will be the environment, through tackling water pollution more effectively. Some contaminants are known to be very toxic even at trace levels, so a more effective technology for water treatment will also benefit human populations by reducing exposure risk. The best industrially utilised technologies, such us ultra-filtration and reverse osmosis, can work well for water treatment, but are very energy demanding with a large carbon foot print, thus not good for the environment. Furthermore these conventional technologies require high capital cost equipment that is expensive to operate and maintain. The absence of economic methods for dealing with toxic and persistent effluent means that large quantities still inevitably enter the environment. There is a lot to suggest that a consequence of such discharge is the 50% decline in sperm counts and increased incidence of Parkinson's disease, both of which have been directly correlated to the presence of contaminants in drinking water. The availability of better technologies to clean-up end-of-pipe contamination will put regulators in a stronger position to impose tighter
legislation on emissions.

Technological development- What we propose here is a move towards development of a novel complementary combination of technologies (biodegradation, nanotechnology and electron accelerator) which could revolutionise the field of environmental clean-up. If it proves successful it will impact positively on the field of nanotechnology and e-beam applications - the potential of biodegradation is already well known. Siemens will be associated with the proposal and see it very much as a means to access the potential application of e-beam accelerators in a broad range of applications. One potential impact of this study will be for Siemens to further investigate the economic feasibility of developing a small footprint mobile, low energy electron accelerator, which could be applied in water treatment systems.

RCUK- The development of a sustainable technology which enables water and resource recovery addresses many of the RCUK challenges, in particular Living with Environmental Change, including Resources, Ecosystems and Health programmes.