Review on transformation behavior of heavy metals and phosphorus in sewage sludge pyrolysis biochar

Abstract

Large amount sewage sludge (SS) is produced from the wastewater-treatment system, which contains many microorganisms, organic pollutants and a variety of heavy metals. In addition, it also enriches nitrogen, phosphorus, potassium and other nutrients. The safe and reasonable disposal of SS without secondary pollution has become a hot issue of current research. Traditional treatment and disposal methods of SS include landfill, incineration, land utilization, etc. SS pyrolysis is expected to become an efficient and clean treatment and disposal method in the future. It has attracted extensive attention of researchers. The basic physical and chemical properties of biochar, the migration and transformation of heavy metals and phosphorus and the influence of additives on the SS-pyrolysis biochar are reviewed. It is found that the additives have the effects of optimizing the basic properties of sludge biochar, fixing/removing heavy metals in biochar, improving the bioavailability of phosphorus. On this basis, the research direction of further study is prospected. It is of great importance to using model compounds to study the co-deposition mechanism of phosphorus and heavy metals during sludge pyrolysis, and provide theoretical support for the wider application of SS-derived biochar in soil amendments, adsorbents, electrochemical materials and other fields.

Keywords

• sewage sludge
• pyrolysis
• biochar
• heavy metals
• phosphorus