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BENEFITS AND POTENTIAL RISKS TO HUMANS FROM AGRICULTURAL USE OF SEWAGE SLUDGE

Diana Mariana Cocârță

Abstract

In the European context, storage and recycling of sludge from sewage treatment plants is a highly discussed and sometime a controversial subject. On the other hand, sludge production at the European level it can not to be neglected, being around 13.25 Mt/year. Even if for sewage sludge management there are many alternatives (including incineration or landfilling), its use in agriculture remains a preferred option in many countries due to the results obtained by farmers in terms of productivity levels achieved for a wide range of cultures. The uncontrolled use of sewage sludge in agriculture could lead important concentration of heavy metals in food chain with real negative consequences to human health. This generates important social and legal concerns, but also research in this field for the scientific world. The present work is evidencing a comparative approach between two different real contexts concerning the potential use of sludge in agriculture. It is well-known that the level of contaminant (and not only) in sewage sludge is generally different, depending on the source of the sludge. That is why, in the framework of the present study it was evaluated and evidenced the agricultural use of sludge from two different sewage treatment plants: the first one is an urban wastewater treatment plant that is not collecting industrial discharges into the urban wastewater collection systems, while the second one is collecting the industrial discharges. The heavy metals concentrations in sludge from the first sewage treatment plant did not overcome the maximum values stipulated by the national regulation in force. Nevertheless, the potential impacts of emerging micro-pollutants as Cd and Pb existing in sludge have been investigated through a long-term field experiment with sewage sludge used on agricultural land. It was evaluated the crop (wheat) productivity and quality. At the same time, information on the content of heavy metals in sludge from the second wastewater treatment plant was presented and solutions for the management of this sludge were proposed. The agriculture use was considered as improper considering that Pb and Zn concentration levels in sludge were over the maximum values allowed by the nation regulation. Regarding Pb and Zn concentrations in sludge, a maximum concentration of 367 mg/kgd.w. comparing with 300 mg/kgd.w. for Pb and a maximum concentration of 16.450 mg/kgd.w. comparing with 2.000 mg/kgd.w. were identified.

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