Investigating techniques to determine magnesium addition requirements for the operation of a struvite crystallization process|
Fattah, K.P. & Mavinic, D.S.
The recovery of phosphorus from wastewater
has gathered strength due to its acceptance as a sustainable
method for solving wastewater treatment plant struvite
problems and the low global reserves of phosphorus ore.
Although the chemistry and successful operation of phosphorus
recovery plants are well documented, there still
exists opportunity to reduce and optimize the use of
external resources, such as magnesium, that is required for
the nutrient recovery. One of the primary operational costs
arises from the need for external magnesium addition, and
therefore, the proper (and timely) detection of the element
is necessary. In this study, methods were tested which
could provide information, on-site, on the rate of application
of the element and its concentration in the various
water matrices. A method was developed that utilizes the
combined use of pH and conductivity to determine the
amount of external magnesium that needs to be added to a
water sample. The amount required was determined by
locating a transition point in the pH–conductivity—external
magnesium added graph and the phosphate concentration
in the water. For each mole of phosphorus removed,
the molar ratio of Mg:P was 1.3–2.0 at the transition point.
The magnesium concentration in the water matrix was also
determined by the hardness test method; this method was
found to be suitable for quick, on-site testing.
Centrate; Magnesium; Phosphorus removal; Struvite; Wastewater