Groundwater treatment to remove organic pollutants is often achieved using granular activated carbon (GAC) or other treatment processes followed by GAC. However GAC is both expensive and has significant environmental impact. Using the Arvia Process® significant cost and environmental benefits were anticipated. This project aimed to quantify these potential benefits by evaluating the results achieved treating pumped groundwater containing a range of complex organics at a site under restoration for development by VertaseFLI. A second site with groundwater containing less complex organics (eg petrol station) was also included within the project.
The aims of this project were:
• To prove that the Arvia® Process can treat real groundwaters
• To compare field results with laboratory trials.
• To compare batch and continuous operation
• To report on the comparable performance of GAC and Nyex® (the absorbent material).
• To calculate the carbon footprint of GAC and Nyex® in a real application.
The Arvia Process® introduces a fundamentally new approach to adsorption technology, using a non-porous, low capacity, carbon adsorbent. To achieve this, a number of innovative elements can be identified.
1. An alternative approach to adsorption – The conventional approach is to use high capacity adsorbents (e.g. activated carbons with high porosities and surface areas) that are excellent adsorbents, but require complex and costly regeneration. The Arvia® process uses a novel, non porous, highly conducting material which can be rapidly and easily regenerated on-site within the Arvia® unit and is an effective but low capacity adsorbent.
2. Electrochemical regeneration – Electrochemical processes for the treatment of low concentrations of organics have suffered from mass transport limitations. Concentrating the organics on the adsorbent surface prior to oxidation eliminates this issue. Unlike the thermal regeneration of GAC (which results in reduced adsorptive capacity and the loss of up to 10% of the starting material), the electrochemical regeneration of Nyex® recovers 100% of the adsorptive capacity with negligible loss of adsorbent.
3. A new adsorbent material – Nyex®, a highly conducting, non-porous, carbon-based adsorbent material has been developed. The non-porous nature of the particles means that adsorption and regeneration are quick with an adsorption/regeneration cycle time of around 60 minutes. This means that although the surface area of the material is low, fresh regenerated surface is continually being renewed, giving a surface area available for adsorption greater than that of the same mass of activated carbon after less than 18 days operation. After this period the Nyex® adsorbent is still operating while the GAC is fully loaded and must be disposed of (landfill or incineration) or sent off site to be regenerated.
4. Continuous & simultaneous adsorption and electrochemical regeneration – A simple mechanism of internal adsorbent recycle allowed a continuous process to be developed. The Arvia® Process is believed to be the first unit where continuous and simultaneous adsorption and regeneration are achieved within a single unit. Scale up has been achieved with a modular design which is easy to manufacture and assemble.