• Universitat de València
• Universitat Politècnica de València
• Università degli Studi di Genova

• Amparo Ribes Greus
• Carmen Primaz
• José David Badía Valiente
• Roberto Teruel Juanes
• Óscar Gil Castell
• Elisabetta Arato
• Barbara Bosio
• Cristina Elia Moliner Estopiñan

Nitrate pollution is currently a growing issue that affects surface water and groundwater. The use of chemical fertilisers has increased considerably in recent decades, leading to noxious environmental processes, including pollution of water resources. Water pollution can have effects on human health due to ingestion, either dissolved in water or in food. Water intake with high nitrate concentrations poses a health risk, as nitrates can form nitrosamines and nitrosamides, which are potentially carcinogenic compounds. Although some methods help to remove nitrates from water, these methods often leave bacterial or organic residues in the water after use.

The present invention provides a process to modify silica from rice straw ashes. The invention includes a series of steps that involves the mixing of rice straw ash with a number of components. By this modification, the silica is activated and acquires the property of nitrate adsorption. The activated silica is then introduced directly into water or an aqueous solution to reduce the number of nitrates it contains. When the activated silica is in the water, an exchange process takes place that transforms the nitrates into chlorides.

Tests have been carried out to calculate the percentage of nitrates adsorbed by activated silica in two different types of water:

• Well water (46.67 ppm nitrate concentration)
• Wastewater (172.24 ppm nitrate concentration)

The tests were conducted in a continuous water flow system in which the water flowed through the activated silica. The silica adsorbed 87.67% of the nitrates in the well water and 90.18% of the wastewater. This percentage decreased over time as the silica became saturated.

The technology development level in this case, using the Technology Readiness Level (TRL) scale, is 4.

Assessment of agricultural residues such as rice straw.

This invention provides an alternative method of rice waste assessment. In addition, this technique of removing nitrates from water using activated silica leaves no residues in the water. This is a great advantage over alternative technologies, such as the use of micro-organisms or acetic acid, methods which leave organic residues in the water.

• Patent granted