A review of phosphorus recovery from different thermal treatment products of sewage sludge

Abstract

Phosphorus (P) is an indispensable element of living organisms and plays an irreplaceable role in the growth of crops. As a non-renewable element, the reserves of phosphorus rock, the primary source of phosphorus in nature, are facing the danger of exhaustion. As a phosphorus-rich solid waste, sewage sludge has gradually become a main renewable phosphorus resource. The combination of effective recycling of phosphorus and innocuous disposal of sewage sludge can not only alleviate the crisis of phosphate rock resources shortage but also reduce the environmental hazards of sewage sludge. This study reviewed the application of thermal treatment in sewage sludge disposal. Besides the advantages of reducing waste volume, decomposing organic pollutants, generating valuable byproducts, it can also significantly promote the recycling of phosphorus. Studies have shown that thermal treatment (incineration, pyrolysis, and hydrothermal) can enrich phosphorus in the products and transform the speciation of phosphorus to increase the bioavailability. The physical and chemical properties of different thermal treatment products and the speciation of phosphorus are different. The transformation and migration of phosphorus affect the efficiency of subsequent phosphorus recovery and reuse. At the same time, this study compared several general phosphorus recovery methods (wet extraction, thermochemical, and electrochemical methods), and further summarized the advantages and disadvantages of various methods and application conditions. This review summarizes recent advances in phosphorus recovery from sewage sludge, identifies challenges and knowledge gaps, and provides the foundation for future research aimed at achieving efficient, economic, and eco-friendly reclamation of phosphorus in sewage sludge.

Hydrochar derived from municipal sludge through hydrothermal processing: A critical review on its formation, characterization, and valorization

“…Wet-chemical extraction and/or coupled with precipitation is the most common method for nutrient recovery from MS-derived hydrochar, as shown in Table 12. The reason is because of its simple procedure and relatively low expenditure (Meng et al, 2019). Our recent review article has detailed the feasibilities and challenges of P recovery from hydrochar using wet-chemical processes (H. .…”

“…Followed by precipitation or crystallization of liquid extracts, P and/or N can be recovered in the form of struvite and calcium phosphates (Ca-P), by adding Mg 2+ and NH 4 + or Ca 2+ solutions, respectively, with adjusted pH. Detailed recovery mechanisms can be found elsewhere (Meng et al, 2019;Peng et al, 2018;Tansel et al, 2018).…”

Migration and transformation mechanism of phosphorus in waste activated sludge during anaerobic fermentation and hydrothermal conversion

“…In addition, the global distribution of phosphorus ore is uneven (e.g. Morocco and Western Sahara occupy more than 70% of phosphate ore in the world) and could lead to significant fluctuation and instability in the price of the resource (Heilmann et al, 2014;Meng et al, 2019).…”

New developments in biological phosphorus accessibility and recovery approaches from soil and waste streams

“…The amount of SSA produced is 1.7 Mt a –1 worldwide, with the P content of SSA ranging from 7 to 11% which is 70 g P kg SSA ‐ 110 g P kg SSA [96]. The common SSA P recovery method is the dry thermal or wet chemical method using strong acids or bases [12,97]. The wet chemical SSA extraction method performed with strong acids can be replaced by a P recovery via bioleaching.…”

“…Here, the ability of both prokaryotes and eukaryotes, such as fungi, bacteria, algae, higher plants and animals, is used to store P in their cells. In bacteria, fungi and algae P is stored in form of poly P [10], in plants P is organically bound as phytate, predominantly in seeds and grains [11,12], while in animals P can be found in tissue, bones and scales. Apart from storing P in their cells, living organisms can release P by dissolving poly‐P or provide P by biomass degradation processes.…”