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