Published in Scientific Papers. Series E. Land Reclamation, Earth Observation & Surveying, Environmental Engineering, Vol. V
Written by Valentin FEODOROV
In solid waste management, composting is defined as a controlled biological process which takes place under aerobic conditions and causes the production of simple and stable compounds in a solid substrate through the degradation of organic matter derived from animal and vegetative residues. Due to the concerns for public health and the environment, in several countries the term "composting" used in organic waste management has evolved over the years referring to the aerobic stabilization of source-separated organic matter. Sewage sludge, being a waste resulted from anthropic activities, is subject to waste regulations which prioritize their management options in order to reduce the negative environmental impacts, the ultimate option being considered the disposal into a landfill. According to the waste management hierarchy, sewage sludge has to be improved whenever possible before final disposal. Waste water treatment, mainly domestic, results in the concentration and disposal of the materials from the treated wastewater. These concentrated residual materials in admixture with water from the sewage sludge. It contains a variety of dissolved or suspension compounds: with agronomic value (compounds with nitrogen, phosphorus, potassium, calcium, magnesium, silicates, alumina, organic matter, trace elements - boron, cobalt, selenium, iodine etc), with energy value (organic matter) and potential pollutants (heavy metals, volatile organic compounds, pathogenic organisms etc). Composting sludge from sewage treatment plants represents an intensive activity and in the case of large sewage treatment plants, a large-scale activity requiring specific technologies, equipment and activities. This sludge treatment method from sewage treatment plants is an effective solution in order to significantly reduce the costs associated with disposal and also allows the production of excellent compost that can be sold for use as a natural product to improve the characteristics of soil.
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