Responsible reduction of nitrates in the comprehensive water cycle

PROJECT DESCRIPTION

BACKGROUND

The use of chemical fertilisers has increased from 14 million tonnes in 1954 to a predicted 200.5 million tonnes in 2018. Nitrogen fertilisers trigger harmful environmental processes, such as eutrophication, acidification, pollution of water resources and emission of nitrogen oxides (NOx).

In Europe, 87% of groundwater contains excess nitrates (European Environment Agency). In intensive farming and cattle-rearing areas, nitrate concentration in groundwater can reach up to seven times the legal limit. The number of areas vulnerable to this pollution has increased, especially in Romania, Belgium, Spain, Sweden, Germany and the UK.

Various studies show that the efficacy of soil management measures for decreasing nitrate levels in rivers and groundwater is limited. New strategies are needed in order to speed up the recovery of EU water bodies from nitrate pollution.

OBJECTIVES

Life LIBERNITRATE aims to reduce the concentration of nitrates in the entire water cycle through an integrated innovative, cost-efficient and highly transferrable technology. The proposed solution was implemented in a pilot plant and consists of an adsorption bed made of active silica, obtained from waste ashes generated during the controlled incineration of rice straw. The active silica was obtained through a second prototype for treating this ash.

The project’s specific objectives are to:

Demonstrate a prototype for depuration of water with a high nitrate content through an adsorption bed of active silica, obtained from controlled incineration of rice straw in a spouted bed reactor specifically adapted for this purpose;

Validate the active silica beds for reducing nitrate concentrations in the water cycle, acting on groundwater from a well and effluent from an osmosis plant, also reducing the energy costs of the osmosis treatment;

Implement a comprehensive awareness-raising procedure for farmers to promote the reduction of nitrates at source; and

Develop a study to assess the project’s environmental, social and economic impact.

 

The results of Life LIBERNITRATE were expected to have high potential for replication and are clearly aligned with the objectives of the Water Framework Directive (2000/60/EC) and the Nitrates Directive (91/676/EEC). At national level, the project focuses on good agricultural practices (Royal Decree 261/1996) and on areas vulnerable to nitrate pollution (Decree 13/2000 of Valencia).

Expected results:

Direct purification of at least 26 m3/day of well water, reducing the nitrate concentration below 50 ppm and close to 25 ppm. The prototype will be directly transferrable to municipalities of 200 inhabitants or fewer;

30% reduction in the concentration of nitrates in 130 litres/day of water effluent - below 50 ppm in drinking water to facilitate compliance with the Nitrates Directive, and in the reject water of a reverse osmosis plant;

Reduction of 0.97 kWh per m3 of wastewater treated in the osmosis plant;

A guide for farmers designed to facilitate a 20% reduction in their use of nitrogenated fertilisers; and

Development of a business plan supporting the replication and transfer of the project and job creation.

 

RESULTS

LIFE LIBERNITRATE demonstrated reductions in nitrate concentrations in the entire water cycle.

 

To achieve this, the project team implemened an integrated innovative, economical, sustainable and transferable system for treating wastewater with a high nitrate content. This was based on the use of an adsorption bed made from active silica obtained from ash produced by a controlled burning of rice straw. Furthermore, they designed a prototype for valorising the rice straw, to produce silica for use in water treatment plants.

 

In total, the project team burned 1 624 kg of rice straw and produced 68.2 kg of useful silica. Two types of pilot plant were designed and constructed to treat nitrate-rich wastewater using the produced silica (with capacities of 130 l/day and 15 552 l/day). In three phases of implementation, they obtained reductions of nitrates up to 29.7%. Their main conclusion was that the technology needs to be further optimised. Post-LIFE, the beneficiaries continue to test the system to increase its technology readiness level (TRL) and bring it closer to market.

 

The beneficiaries conducted a comparative LCA with the project technology, reverse osmosis, and bottled water. The results showed that, from the environmental perspective, reverse osmosis has the lowest impact, but the project process is favourable compared with bottled water. The project solution would be competitive to treat water in small towns (up to 200 inhabitants) where it is not viable to install reverse osmosis technology. From the economic side, the system is competitive only when a significant amount of silica is produced. For instance, according to their calculations, for 15 000 kg of silica produced, the project treatment would cost €0.64/m³ of water treated, compared to an average price of €0.62/m³ with reverse osmosis and €0.95/m³ with ion exchange.

 

The comprehensive nitrates reduction approach also utilised low-release fertilisers, which the project team showed they did not negatively impact crop production (citrus, kaki and rice) though they are favourable for the environment. The beneficiaries created a guide for farmers on the use of nitrogenous fertiliser to facilitate reductions in their use, a six-module training course that is available online (e.g. the LIFE LIBERNITRATE channel on YouTube), and other supporting materials. The beneficiaries continue to promote the course among farmers to expand the impact of the project.

 

Further information on the project can be found in the project's layman report (see "Read more" section).