Reuse of Sludge as Organic Soil Amendment: Insights into the Current Situation and Potential Challenges

Abstract

Sludge generation as an organic by-product of wastewater treatment has seen a consistent increase worldwide due to population growth and industrial activities. This poses a chronic challenge regarding management options and environmental concerns. The agricultural valorization of unconventional organic materials has become inevitable, especially in semi-arid and arid countries that suffer from depleted soils and shortages in farm manure supply. High-income countries have also been interested in this recycling practice to mitigate landfilling or incineration issues. Sewage and some industrial sludges contain a complex mixture of beneficial and harmful substances, which varies with the origin of effluents. Therefore, sludge land application should be well managed in order to achieve sustainable agro-environmental goals. This review paper focuses on different aspects related to sludge reuse in agriculture, starting by investigating the diversity of sludge types and composition. In addition to the preponderant urban sewage sludge, the less-studied industrial sludges, such as those generated from pulp and paper mills or gas-to-liquid industries, are hereby addressed as well. Then, post-land application effects are discussed in relation to sludge quality, dose, and reuse conditions. The present paper also examines the disparities between guidelines that determine sludge conformity for land application in various countries or regions. Accordingly, special attention is given to increasing risks related to emerging pollutants in sludge such as pharmaceuticals, which have been overused since the outbreak of COVID-19 pandemic. This exhaustive investigation will assist the establishment of sustainable strategies for the safe agricultural reuse of biosolids.

Lead and copper removal from sterile dumps by phytoremediation with Robinia pseudoacacia

“…Generally, the dewatered sludge resulting from urban sewage treatment plants is composed of 20% fats, 50% carbohydrates (sugar, starch, and fiber), 30–40% organic matter, 3% total nitrogen, 1.5% total phosphorus, and 0.7% total potassium, has a C:N ratio of 10–20 and a neutral pH and it is often used as an organic fertilizer for acidic soils improving the soil physico-chemical properties, being an ecological alternative to chemical fertilizers 26 , 64 . The dewatered sludge resulting from the Someș sewage treatment plant did not record traces of heavy metals.…”

Unveiling the bioleaching versatility of Acidithiobacillus ferrooxidans

“…The disposal of such large volumes of sewage sludge raises substantial environmental apprehensions. The application on agricultural land emerges as an attractive option, offering nutrient recycling and augmentation of soil organic content (Mabrouk et al, 2023). However, this approach confronts several constraints, as sludge: (1) harbors numerous pathogens, (2) may contain elevated levels of heavy metals, and (3) its bulkiness and associated transport costs pose logistical challenges (Tytła, 2019).…”

Knowledge, Attitudes, and Intentions of Biosolids use in Agriculture: Perspective from the Agricultural Managers of the Dominican Republic

“…Additionally, the presence of biosolids can suppress soil-borne diseases, reducing the need for synthetic chemical fertilizers and pesticides. However, certain precautions must be taken in the use of biosolids in agriculture, especially about the potential for pathogen transmission and accumulation of heavy metals in the soil [4], [5]. The successful adoption of biosolids as fertilizer relies heavily on farmers' knowledge, attitudes, and intentions regarding their usage.…”