PROJECT DESCRIPTION
BACKGROUND
Contamination of groundwater by arsenic represents an environmental issue of global concern due to the severe threats to human health, including malignant cancers and vascular disease. The risk to human health and the widespread occurrence of arsenic contamination have led to the imposition of severe limits to arsenic concentrations in drinking water. Since 1998, the EU has fixed these limits to 10 g/L (Directive 98/83/CE). However, groundwater arsenic levels between 10 and 1 500 g/L have been recorded in regions of Italy, Greece, Croatia, Germany, and Portugal. Although anthropogenic sources contribute to increase arsenic concentration, it is generally determined by natural phenomena such as volcanic activity and alluvial deposits. Water treatment plants specifically designed for arsenic removal exist, but their high capital and operation costs limit their implementation. Adsorption with iron-based materials (Fe) represents the most common solution, even though other technologies are also used, such as absorbents based on titanium dioxide, reverse osmosis and ion exchange. In Italy, operating plants can treat up to 38 400 m3/day of water, covering the needs of about 160 000 citizens. The total cost for Fe-based arsenic removal plants is around 0.16/m3. More than 50% of such cost is covered by the cost of Fe-based adsorbents ($5-10/kg with 1-3 g/kg of arsenic removal). The development of innovative technologies to remove arsenic from groundwater at a reduced cost is fundamental to ensure the sustainable supply of drinking water to EU citizens.
OBJECTIVES
The LIFE BIOAs project aimed at demonstrating a process to produce an innovative bio-adsorbent for the removal of arsenic from contaminated water. A technologically competitive bio-adsorbent was thus produced via the hydrothermal carbonisation of olive pomace, a by-product of the olive oil production industry.
The proposed strategy valorised a by-product of the agro-industrial sector, in line with EU circular economy objectives, and produced an innovative adsorbent for arsenic removal at a cost at least 50% lower (< 3/kg), when compared to the conventional employed granulated ferric hydroxide (GFH) adsorbent for arsenic removal from drinking water.
The performance of the produced bio-adsorbent was demonstrated by its application in a portable skid pilot water treatment unit processing contaminated groundwater from different municipalities of the Lazio region, Italy. In parallel, the bio-adsorbent was tested for replicability on different water collection points in certain zones in the North and Central regions of Portugal, that are well known for their high levels of arsenic.
RESULTS
The LIFE BIOAs project demonstrated at the pilot scale the environmental and economic feasibility of a process to produce an innovative bio-adsorbent through hydrothermal carbonisation of olive pomace (a by-product of the olive oil industry) and to use this sorbent for in-line purification of water having Arsenic content above the limits set by the EU Arsenic Drinking Water Directive.
The project has designed and implemented two prototypes. The first one converts the olive pomace, through an innovative hydrothermal carbonisation process, into a particular Fe-hydrochar in which a metal active in the adsorption of arsenic is dispersed. This hydrochar is subsequently granulated and activated in order to increase its specific surface area. The second prototype implements Arsenic adsorption operations using the Fe-hydrochar instead of conventional Granulated Ferric Hydroxide. The innovative bio-adsorbent has been used for the removal of Arsenic present in drinking water to comply with the limit of 10 μg/L imposed by the European Directive 98/83/EC. Operations include filtering and backwashing in order to concentrate Arsenic in a filter bed which is removed and substituted when saturation is reached.
At the end of the water treatment process, the exhausted bio-adsorbent is a biomass that was experimentally sent to a gasification plant to produce thermal energy. This yielded significant environmental/climate benefits, considering that conventional exhausted Granulated Ferric Hydroxide can be only disposed to special landfills. Based on a specifically developed LCA, as well as on direct experimental measurements carried out during the monitoring campaign, the main benefits achieved were:
- GHG emissions reductions in terms of kg CO2 eq. equal to 84% when compared to a conventional process;
- waste reduction equal to 87% thanks to the gasification treatment of spent bio-adsorbent;
- energy valorisation (production of renewable energy) from the organic fraction of exhausted Fe-hydrochar equal to 3.46 kWh/kg.
Significant economic benefits are related to the lower production costs of production of the bio-adsorbent, mainly catering to using by-product biomasses and reduced consumption of primary resources. Through this innovative process, the overall cost of water treatment is reduced by 68% with respect to conventional techniques.
Replicability and transferability actions sought to demonstrate that the system can work by using different feedstock and can be effective on different waters, thus proving its applicability to different EU rural areas (in which different biomass feedstock and different waters might be available). The performance in water treatment of the innovative bio-adsorbent was also demonstrated for the removal of an emerging contaminant (the antibiotic Sulfadiazine).
Lastly, the project produced a business plan which highlighted sustainability of the whole system. On that basis, the project plans include a significant plan for replication of its technology at the scale of the whole Viterbo province, heavily affected by arsenic-contaminated groundwater. The replication potential relies in the substitution of all existing treatment plants of potable water with new plants working with the novel system in 5 years, in order to cover the need of 660,000 inhabitants eq. of Viterbo Area (48 Mm3/year).
As to the EU policies, a number of beneficial contributions are foreseen for:
- Directive 2000/60/EC (Water Framework Directive), for which the project provides a new water treatment technology that can be widely applied for the safeguard of water bodies;
- Directive 2020/2184/EC (Drinking Water Directive), as the project will contribute to the reduction of arsenic concentration in tap water at levels thanks to the development and demonstration of its innovative technology;
- Directive 96/61/CE (Integrated pollution prevention and control), for which the project provides a new and cheaper technology able to facilitate the removal of arsenic and other pollutants from industrial effluents;
- Directive 2008/98/EC (Waste Framework Directive), as the project avoids olive oil pomace disposal and demonstrates how it can be transformed in a product with high added value for the removal of arsenic from drinking water;
- Directive 2020/741/UE (Minimum requirements for water reuse), as an aqueous by-product is obtained at the end of the process to produce bio-adsorbents, which can be reused for field irrigation.
