TechnologyTowards a circular water economy: 4 lines of work

Towards a circular water economy: 4 lines of work

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On the horizon of 2050, the competitiveness of the agri-food industries will depend to a large extent on their ability to face the main challenges in terms of sustainability. Consumers, more informed thanks to advances in digitization and social networks, will only accept responsible companies that have a firm commitment to the environment.

In fact, the scarcity of resources such as water is beginning to be one of the main concerns both nationally and internationally. About what are the advantages of applying circular solutions, as well as the main technological innovations in reduction, recycling and reuse of water, we reflect in this article.

Industry consumes a large amount of water. After agriculture, it is the largest user of fresh water in the world. About 22% of water is used in industry, compared to 8% used in our homes. Specifically, the food and beverage industry represents about 2% of total water consumption in the European Union. These facts require the development of strategies that increase the efficiency in the use of water resources.

R+D+i must propose solutions that allow industries to change the linear model of using and purifying water for circular models where the use of water is optimized and the concept of wastewater, liquid currents that are considered valuable resources, is abandoned. to recycle and reuse. The presence of these measures in the production plants of the agri-food industries will show that the company is moving towards excellence.

Solutions: towards a Circular Economy of water

Reduce water use

Cleaning and sanitizing operations are often the highest water-using activities in food and beverage industries. The high hygienic requirements mean a high dedication of resources such as water and the generation of large volumes of wastewater.

In fact, according to the BREF ( Best available techniques Reference document ), the average consumption of equipment and facility sanitization processes, for example in dairy industries, can be twice as many liters of water as milk produced or in fish processing companies it can reach up to 16 litres/kg of product.

But, how can we optimize the cleaning and disinfection processes? The incorporation of hygienic eco-design can reduce between 40 and 50% of the use of water in industrial facilities. This fact has been demonstrated in the industrial plants of Calidad Pascual (Aranda de Duero, Burgos) or Pescanova (Porrino, Pontevedra) where the LIFE Ecodhybat project has been developed. The execution of this project has made it possible to obtain the necessary evidence so that hygienic design is included as BAT in the draft of the latest BREF.

On the other hand, the optimization of cleaning operations through the application of new eco-efficient technologies, such as the pigging system for emptying pipes by compressed air, maximize water savings, significantly reducing consumption.

Recycling of process streams

The recycling of internal currents derived from production processes allows the use of water as an alternative source of drinking water, thus reducing the need to use external well or network water. This fact achieves, in addition to increasing the efficiency in the use of the hydrid resource, minimizing the costs derived from the sanitation canon.

The water can be recycled in the same stage of the production process where it is generated, or in others, and directly or with conditioning. Technologies based on oxidative or separative processes are innovative solutions that allow regenerating water up to the quality required for reuse: fit for use .

An example is the innovative solution developed in the Eco3wash project, a prototype made up of a train of technologies based on advanced oxidation processes, capable of recycling up to 1,000 liters of water every hour from washing fruit and vegetables from cooperatives and agricultural industries.

For their part, the separation processes through the use of commercial polymeric nanofiltration membranes allow the recovery not only of water but also of caustic and acid solutions from CIP (Clean in Place ) streams at temperatures up to 70⁰C.

In addition, electrodialysis technology with bipolar membranes has great potential for the valorization of residual brine streams from ion exchange resins, as well as from the agri-food industry ( eg , olives or salting), obtaining as products: treated and recyclable water, soda and hydrochloric acid.

Reuse of treated water

Spanish legislation, through RD 1620/2007, which establishes the legal regime for the reuse of treated water, determines the qualities and uses allowed for regenerated water, such as crop irrigation, street washing, industrial vehicle washing or cooling towers.

The reuse of water favors the objective of zero discharge, as in the case of the success of the J. Garcia Carrion plant located in Andevalo (Huelva), where zero net water consumption has been achieved. 100% of the volume of water used in the juice manufacturing process is later used to irrigate the 1,500 hectares of orange trees that the company itself cultivates around the factory. The J. Garcia Carrion juice plant uses 500,000 m3 of water per year and 5 Hm3 to irrigate its orange plantation.

80% of the industrial plant’s water consumption is used in CIP and single-use cleaning systems, while the other 20% is used for washing oranges. The application of a multi-stage treatment system that includes high-load anaerobic, MBR (in English, membrane bioreactor ) and disinfection with hypochlorite has allowed the company to reuse all the water consumed in the factory for irrigation, complying with RD 1620/ 2007.

Use of wastewater resources

Wastewater contains usable resources such as nitrogen and phosphorus, nutrients that can be valued through the application of different water treatment technologies.

One of the mature technologies is the biological process based on the synergistic combination of microalgae and bacteria, which is an alternative for the purification of agri-food wastewater. These systems are especially advantageous with respect to activated sludge due to the high nutrient recovery through recoverable biomass, as well as its positive energy balance.

An alternative to this microalgae-bacteria pairing is the coupling of the duckweed culture ( Lemna ) to a conventional anaerobic treatment. Lemna is a small, free – floating macrophyte plant that has a high capacity to extract nutrients from the water in which it grows, especially nitrogen and phosphorus. Compared to other autotrophic microorganisms used in purification, Lemna has advantages such as ease of harvesting and its high potential for biomass production with high added value. In fact, the resulting biomass is a high-value protein source that can be valued for the production of feed and biofertilizers.

One last innovative solution for nutrient recovery is the one being developed by the Mahou San Miguel brewery at its plant in Alovera (Guadalajara). This alternative, made up of a technology train based on electrocoagulation processes and bioelectrochemical reactors, allows, in addition to reusing water and producing energy, recycling residual aluminum from cans as a flocculating agent in the electrocoagulation pretreatment. The electrodes obtained from the recovered aluminum dissolve and generate salts that allow the recovery of nutrients as fertilizers.

According to the conclusion of the Technical Seminar “Circular Economy in the Management of Water by Agrifood Companies”, organized by AINIA Technological Center, agrifood companies must adopt the principles of the circular economy in water management through a comprehensive vision and the incorporation of new innovative technologies. If your company requires technological solutions in the field of environment, energy and water, please contact us.

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