System to reuse with health guarantees, sludge from wastewater

(Press-News.org) The water treatment consists of removing the pollution of the same water for the same or better quality. In this process, which takes place in wastewater treatment plants, a sludge is originated which are governed by specific legislation. They are also purified and can be reused in the field as mulch or for composting. Its use is regulated by the EU through an increasingly restrictive Directive. Faced with a possible tightening, the industry looks for viable alternatives to current uses, which enable them to sell this by-product.

The sludge from the wastewater treatment may have different types of pathogens that cause diseases in humans, viruses, bacteria (Salmonella, E. coli), protozoa and helminths (Ascaris) - and cause infections in the soil when applied as agricultural amendment. That is why the chain to ensure food safety from the start, it is essential to sanitize the mud before being used.

Several studies have shown that the addition of caustic lime to the sludge can eliminate pathogens. Specifically, lime can help to create physicochemical conditionswhich can stop the biological degradation of organic matter they contain, avoiding thus the production of odors.

With the dual aim of solving this environmental problem and to demonstrate the effectiveness of the lime as WWTP sludge sanitizing element, GROPO CALCINOR leader in the production of quicklime, calcined dolomite, hydrated lime and refractory products in Spain, in collaboration with Neiker-Tecnalia, which is investigating the agronomic value of WWTP sludge, and Gaiker-IK4, which has a broaden experience in soils, have set a R + D + i proyect in motion.

The results obtained so far show that the WWTP sludge treatment with lime, sanitizes, reducing the concentration of bacteria below the detection limits. It also stabilizes the sludge in the long term by avoiding the decomposition of organic matter and also reduces its moisture, thereby facilitating handling. Thus, the conclusions obtained to date suggest that this study will provide a solution to sanitize the wastewater treatment plant sludge and that they may continue to apply with full guarantees of safety in agriculture.

No risk to health

The project, which started in 2009, with an expected duration of 3 years, aims to demonstrate that the application of lime enables sludge sanitation, either for reuse for soil improvement as an sanitized agricultural amendment , or for regeneration of degraded environments without risk to plant , animal or human health. In fact, this R + D + i project, which is funded by the Basque Government in the framework of INTEK-BERRI programme, will examine its third phase, the effect of sludge inerted and sanitized on a degraded mining environment of the Basque Country . It will also propose a scheme of the facility needed to move the application to an industrial level, the size of which depend on both the type of sludge treatment plant and the volume to be treated.

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