A study by the BETA Technology Centre of the UVic-UCC and the ICRA helps the livestock sector to reduce antibiotics in slurry.

The effectiveness of the technologies installed in livestock manure treatment plants (slurry and manure) to remove or concentrate nutrients and to generate organic fertilizers of high agricultural value has been widely demonstrated. To date, however, the information available on the ability of these systems to reduce the concentration of other pollutants, such as veterinary drugs and antibiotics, is very limited. In part, the lack of information is attributed to the lack of measures in the Spanish regulatory framework that sets maximum permitted amounts of these emerging contaminants.

Related to this issue, the European Union has proposed to take some measures, within the framework of the EU Zero Contamination Action Plan, such as the entry into force of the regulation on veterinary medicinal products and medicated feeding stuffs. This regulation aims at reducing the consumption of veterinary antibiotics and the restriction of others for human consumption only. Thus, from 28 January 2022, pharmacovigilance of veterinary antibiotics will be compulsory and the rules on environmental risk assessment will be revised.

In this context, the BETA Technological Centre of the University of Vic - Central University of Catalonia (UVic-UCC) and the Catalan Institute for Water Research (ICRA) have just presented a technical guide  that compiles the results of a study on the presence of veterinary drugs and antibiotics in livestock manure and makes recommendations on how these pollutants can be reduced with current technologies applied in the treatment of slurry and manure. The handbook is intended as a tool to guide companies in the livestock sector on which technologies are most effective and to propose mitigation strategies to ensure that the use of slurry and manure does not pose a risk to the environment, animal and public health.

The guide Demostración de la capacidad de reducción de antibióticos en tecnologías de tratamiento de purines: Guía técnica de asesoramiento para el sector ganadero compiles the results obtained in three real livestock manure treatment plants in Central Catalonia. According to Meritxell Gros, ICRA researcher: "the study confirms that, despite the improvements that have been made in recent years in the livestock sector to reduce the supply of drugs and antibiotics, the concentrations of these substances detected in pig slurry and cow manure are remarkable, up to mg / L in liquid fractions and mg / kg in solids". These concentrations are higher in pig slurry. "The most frequently detected compounds are antibiotics of the tetracycline group, fluoroquinolones, macrolides, lincosamides and tiamulin, which are used for the treatment of gastrointestinal and respiratory diseases, together with flubendazole, a drug to treat intestinal parasites, and the anti-inflammatory flunixin," adds Gros.

Four consolidated technologies

The study conducted by the consortium formed by CT BETA and ICRA has been carried out in the framework of the project "Aids for Demonstration Activities" of the rural development programme 2014-2020 of the Department of Climate Action, Food and Rural Agenda of the Generalitat de Catalunya. The work focuses precisely on evaluating the effectiveness of four consolidated technologies to reduce the occurrence of drugs, antibiotics and antibiotic resistance genes in pig slurry and cattle manure.

One of these technologies is phase separation, which consists of separating the liquid and solid fraction of the slurry and manure. Another technique is anaerobic digestion, to degrade organic matter, produce biogas to generate energy and a solid digestate that can be valorized as a bio-fertilizer. The third technology evaluated is nitrification-denitrification, which reduces nitrogen and organic matter concentrations in liquid slurry fractions. Fourthly, composting has been studied to reduce the biodegradable organic matter in the solid fraction and obtain a product with a high nutrient content that can be used as a biofertilizer in agriculture.

Additionally, an innovative treatment, reverse osmosis, which concentrates salts and nutrients and obtains a liquid stream, called permeate, with a low content of solids, colloidal matter, ions, pharmaceuticals and antibiotics has also been evaluated. Finally, this work also analyses the need to implement additional treatment technologies to minimize the potential risk associated with the use of the products obtained as fertilizers in agriculture.

"The results of the case studies show that, although the livestock manure treatment technologies studied are designed for the concentration or removal of nutrients, they can also be useful for reducing the concentration of veterinary drugs and antibiotics," explains Lidia Paredes, researcher at CT BETA.

Recommendations for the livestock sector

The technical guide concludes with a series of recommendations for the livestock sector regarding the management of livestock manure and its use as agricultural fertilizer. Firstly, it notes that solid-liquid phase separation systems or reverse osmosis systems produce liquid effluents

(concentrate in the case of osmosis) and solid fractions in the case of separation, with a high content of veterinary drugs and antibiotics. In addition, osmosis yields effluents with low concentrations of these compounds. The research found that during the osmosis stage, the removal of pharmaceuticals and antibiotics was high (more than 90%); in composting, the removal percentages were moderate-high (more than 70%); during nitrification-denitrification they were moderate (between 40% and 80%) and with anaerobic digestion they were moderate-low (10-60% with some exceptions of compounds with high removals).

Secondly, the research determines that treatments based the nitrification-denitrification (NDN), which are used to remove nitrogen from liquid fractions of slurry, are also particularly efficient for the reduction of pharmaceuticals and antibiotics in liquid fractions.

A third conclusion is that anaerobic digestion (AD) systems generally have low drug and antibiotic removal efficiencies and therefore the application of complementary post-treatment systems is recommended.

Finally, the study also concludes that composting is the preferred option to treat the solid fraction of slurry and manure and the dewatered sludge from the NDN process, as this technology has a high performance in reducing the concentration of drugs and antibiotics. This is of particular interest, as most of the drugs and antibiotics are concentrated in this fraction.

"As the study points out, the potential applicability of these technologies is very high in Catalonia, where there are more than 20,000 livestock farms. In the design of new slurry treatment plants, it would be advisable to consider the results of this research," says Paredes. The new plants should include, in addition to the elimination of nutrients, the reduction and elimination of drugs, antibiotics and antibiotic resistance genes.


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