High nitrate concentrations have a major impact on potable groundwater supplies. The costs of conventional surface treatments can be high and where possible, blending is the preferred option. With increasing nitrate in groundwater, cost-effective and sustainable treatment technologies are required for the foreseeable future.
Enhancing the denitrifying capacity of aquifer systems to reduce nitrate would therefore offer technical, economic and environmental advantages over conventional solutions without generating waste streams. Laboratory research by WRc and UK Imperial College London) developed data sets for a biochemical transport model enabling quantitative modelling of the denitrification process using British aquifer material.
Field trials were then undertaken by WRc in 2002 to assess the technical feasibility and process optimisation of in-situ nitrate bioremediation in chalk groundwaters. The research was undertaken with an UK Water Utility and with support from the UK Regulators, the Environment Agency and the Drinking Water Inspectorate.
Initial trials have clearly proven induced denitrification and the technical feasibility of the technique. Additional trials are now proposed to optimise process management and design in both chalk and sandstone aquifers.
The research demonstrated that:
- In-situ bioremediation offers significantly reduced CAPEX and OPEX costs when compared to conventional surface treatment processes such as reverse osmosis, electro-dialysis and ion exchange.
- As no discernible waste stream is produced, the technique removes the financial and environmental burden of wastewater management and disposal.
- The control equipment requires a small and unobtrusive 'ground footprint' compared to other techniques.
- The technique provides an opportunity to reactivate remote sites where other options for high nitrate groundwaters (such as blending) are impractical.