The Relevance of Phosphorus and Iron Chemistry to the Recovery of Phosphorus from Wastewater: A Review

Abstract

The addition of iron is a convenient way for removing phosphorus from wastewater, but this is often considered to limit phosphorus recovery. Struvite precipitation is currently used to recover phosphorus, and this approach has attracted much interest. However, it requires the use of enhanced biological phosphorus removal (EBPR). EBPR is not yet widely applied and the recovery potential is low. Other phosphorus recovery methods, including sludge application to agricultural land or recovering phosphorus from sludge ash, also have limitations. Energy-producing wastewater treatment plants increasingly rely on phosphorus removal using iron, but the problem (as in current processes) is the subsequent recovery of phosphorus from the iron. In contrast, phosphorus is efficiently mobilized from iron by natural processes in sediments and soils. Iron-phosphorus chemistry is diverse, and many parameters influence the binding and release of phosphorus, including redox conditions, pH, presence of organic substances, and particle morphology. We suggest that the current poor understanding of iron and phosphorus chemistry in wastewater systems is preventing processes being developed to recover phosphorus from iron-phosphorus rich wastes like municipal wastewater sludge. Parameters that affect phosphorus recovery are reviewed here, and methods are suggested for manipulating iron-phosphorus chemistry in wastewater treatment processes to allow phosphorus to be recovered.

Phosphorus recovery as ferrous phosphate (vivianite) from wastewater produced in manufacture of thin film transistor-liquid crystal displays (TFT-LCD) by a fluidized bed crystallizer (FBC)

“…Chemical precipitation has been proved to be more efficient than biology. 15 The reagents that have been used to remove phosphate are Mg 2+ /NH 4+ , Ca 2+ , Al…”

Comparisons Study of Phosphate Removal in Unaerated and Aerated High Calcium Steel Slag Filter System of Different pH Feed

“…Performance of phosphorus removal was affectedby parameters include pH, temperature, concentration of metallic salts, HRTv and many more [12]. Of all these, pH values of the influents are known to contribute significant effects on phosphorus removal.…”

“…Besides that, high dissolved oxygen in aerated conditions causes much more carbon dioxide to be stripped to the atmosphere thus produce little carbonic acid. This results in the increase in pH levels in the system [12]. Therefore, this study was carried out to compare the difference performance of aerated and unaerated high Ca steel slag systems at different pH values for its phosphate removal efficiency.…”

New perspectives for the design of sustainable bioprocesses for phosphorus recovery from waste

“…Wilfert et al (2015) postulate that future energy producing WWTPs will rely on iron addition for P and COD removal, but highlights the problem associated with P recovery from the iron, even though in environmental systems, P is efficiently mobilized from various iron P compounds through (microbial) oxidation and reduction, under alkaline or acidic conditions, etc. Therefore, the authors believe that the current poor understanding of iron and P chemistry in wastewater treatment systems is inhibiting the development of processes to recover P from iron-P rich sewage sludge.…”