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Control of WWTP sludge for agricultural use in Spain

The ambition of the current legislation, with over 20 years old, is far from the current trend in the EU

imagen noticia
02/05/2012 - Environmental
In Spain, the generation of sludge from Wastewater Treatment Plants (WWTP) and its subsequent destination for agricultural use are regulated and permitted by Royal Decree 1310/1990 (transposition of Directive 86/278 of the European Union). But the reality is, as AGQ environmental area´s members explained, that "a legislation over 20 years old can hardly adapt to the development experienced by the company on environmental matters."

During the process of purification of urban waste water, they are formed what is known as WWTP sludge. These residues accumulate organic matter, nutrients and pollutants (heavy metals, microorganisms and dioxins, etc.) that were present in the water that has been treated. The composition of this sludge is subject, therefore, to the origin and composition of the water that is purified and the type of treatment they undergo.

Agricultural use of sludges

The agricultural use of sludge is one of the most common destinations of WWTP sludge worldwide as it allows the reuse of waste, as well as supplies shortages of organic matter in regions mainly arid and semiarid increasingly extended. It is necessary, therefore, a strict control and regulation in this matter to avoid possible harmful effects on soil, plants, animals and humans.

According to the Ministry of Agriculture, Food and Environment, sludge production in Spain shows a constant growth in recent years, reaching in 2009 the figure of 1,205,124 tons. The 83% is destined for agricultural soil use, 8% is stored and then eliminated in controlled landfills, 5% is incinerated and 4% is included under "other destinations". In the absence of official figures in later years on the production of sludge and its application in Spain, European Union sources (Eurostat) predicted, in a study based on 2007 figures, a production of 1,280,000 Tn of sludge for 2010, a figure that will not change for 2020. Agricultural use, according to this source, would remain around 70%. It is certainly striking the limited official information about actual numbers on the generation and subsequent purpose of sludge.

José Luis Ganivet, director of AGQ Environment Area , reminds that the legislative control in Spain in terms of sludge "falls to a lower level than the very tendency of the EU and its member states legislation." Thus, the EU trend in recent years is to reduce the maximum permitted values of heavy metals in sludge and soils about 50% over current levels. Control is one of the strengths, from the current six-monthly to proposals that become monthly for plants with a production of over 4,000 tons / year. Finally, as discussed Manuel Martin, AGQ environmental technician, "not only seems enough to have more analytical control and higher demands regarding the maximum permitted values but the controls need to focus not only on heavy metals, and parameters such as microorganisms, dioxins and other organic compounds pass into the foreground.”

In this regard, countries like Germany, Austria, Holland and Denmark have already evolved in these lines with legal requirements much higher than those in our country, when it comes to the maximum permitted values and periodicity in their control, and the analyzed parameters (As, Mo, Co and microorganisms, for example).

AGQ Labs has years of experience in this sector, being one of the major references on a national and international level. From our Environment and Agriculture areas, we don´t only interpret the implications of the obtained values from the legal standpoint, but we are specialists on agricultural chemistry and therefore on the soil-plant-water system, promoting good practices in agriculture and a controlled use of fertilizers. In this sense, AGQ has performed joint collaborations with the Metropolitan Corporation for Water Supply and Sanitation of Seville (EMASESA) and the Lebrija Marshes Cooperative, among others. Thus, our departments of Agriculture and Environment were able to evaluate the effects of composts from an EMASESA's sewage treatment plant which the Lebrija Cooperative had applied in soils with tomato production. As key results, a significant increase in production was found and also the quality of the crop was verified.

We analyse in AGQ more than 9,000 soil samples a year and about 1,500 sludge samples. We also advise about 600,000 hectares of crops around the world in which we implement successfully our nutritional monitoring system with which we supply, in a way that respects the environment, soil deficiencies in their contribution to the plants.

Moreover, as an accredited laboratory in UNE-EN-ISO/IEC 17025, we offer sludge and soil analysis (See pack LD-0007 and S-0291), in compliance with the legislation in force, while providing specialized advice according to the needs of our customers.