A review of methods, influencing factors and mechanisms for phosphorus recovery from sewage and sludge from municipal wastewater treatment plants

Phosphorus is related to global human food security, and the global reserves of phosphate rock are gradually depleting. Phosphorus recovery from wastewater is urgently needed, both in terms of laws and regulations and food security. This article reviews the methods, influencing factors and mechanism of phosphorus recovery from sewage and sludge. These methods include crystallization precipitation, adsorption, electrochemical, membrane separation and biological methods. The recovery rate of crystallization precipitation can reach 80%. pH value and different ions can affect the formation of precipitated crystals. Considering the operability and economy, the adsorption method is the first choice, but the adsorption efficiency is affected by factors such as adsorption time and adsorbent dosage. The electrochemical method generates OH- by electrolyzing water at the cathode to increase the pH value, thereby producing phosphate precipitation. In addition, membrane separation can recover more than 95% of total phosphorus in wastewater, but high investment and membrane fouling limit its application. For the bio-absorption of phosphorus-accumulating microorganisms/microalgae is the main mechanism for biological enrichment of phosphorus. Besides, the recovery of phosphorus from sludge mainly relies on chemical and heat treatment. The core idea of the chemical method is to release phosphorus from the sludge through pretreatment and thermal treatment laws focus on the effect of temperature on phosphorus production and recovery. In addition, the latest research progress and achievements are introduced, and the shortcomings and future research directions of various phosphorus recovery methods are pointed out.