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Sludge valorisation through recycling

Application of raw sludge to agricultural land is an option as long as the sludge is immediately incorporated in the soil. This way of recycling sludge can be problematic due to offensive odors and a potential health risk due to pathogens in the raw sludge.

Stabilized (treated) sludges, for example with lime, no longer have any offensive odors.

Application of treated sludge to agricultural land is considered to be the best practicable environmental option for most sewage sludge. Care must be taken that applying the sludge will not pose any health or environmental hazard due to it's content of pathogens and heavy metals. Furthermore, the sludge should be applied according to the fertilizer requirements of the crops grown on the land to prevent leaching of the nutrients, especially nitrogen.

Neutralac® solution

The following Neutralac® reagent will allow to hygienize, stabilise and improve agronomic values of sludges :

Quicklime - Neutralac® Q

Quicklime - Neutralac® Q SR

Quicklime - Neutralac® Q DB

Hydrated lime - Neutralac® H

Half burnt dolomi - Neutralac® CM

Sludge recovery in agriculture

Managing municipal and industrial waste is a major challenge for modern society. The environmental problems and economic costs associated with land filling have led to current approaches that emphasize viewing waste products in terms of the potentially useful constituents they contain. From this perspective, waste management is transformed from a problem of waste disposal to a challenge for resource re-utilization without adverse environmental effects.

Limed sludge have beneficial effects on soil chemical and physical properties. Application of these waste materials to agricultural land presents an opportunity for recovery of essential plant nutrients, can provide low-cost liming amendments, and may have positive effects on infiltration, drainage, and water-holding capacity by improving soil structure.

However, there are many different types of wastes and recycling them through soil-plant systems requires appropriate solution.

Despite the variability both between and within different classes of waste products (according to their source, their further processing, their location of production), we can describe their general benefits as following:The effects of digested sewage sludge from wastewater treatment plants on plant growth and environmental quality have been extensively studied at many locations. Sewage sludge supplies essential plant nutrients and is a valuable source of organic matter. In many locations, hydrated lime is used as a dewatering agent and sludge conditioner, and the resulting lime equivalent of the sludge is useful in maintaining soil pH.On a dry weight basis, digested sewage sludge commonly contains 3 to 6% N, 1 to 4% P, 0.2 to 1% K, and 50 to 60% organic matter. Sludge often can be used to meet the entire crop requirement for N and P. Supplemental K is frequently necessary, but sludge also supplies plant available Ca, Mg, and essential micronutrients. Sludge organic matter is as effective as manure in improving soil structure, as measured by increases in total porosity and aggregate stability, and improved pore size distribution.

An important parameter to follow for land application of sewage sludge is its trace metal content. Rules have been established, based on ceiling trace metal concentrations and cumulative metal-loading rate limits, for the safe utilization of sewage sludge on agricultural land.

Composted sewage sludge can be used for land application or as a component of the growing medium for container grown plants. Sewage sludge is frequently co-composted with wood chips, sawdust, or MSW. However compost has a lower organic value than the initial sludge, due to the biological degradation of the organic matter.

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