9 Struvite Crystallization: An Effective Technology …
161
of NH 4 −N was removed at pH 6 and Cl/NH 4 −N wt. ratio of 8.2:1. Additionally,
more than 92% of NH 4 −N in LL could be removed using the recycled product, in
which nearby 34% of the chemical cost could be saved. Siciliano et al. (2016) tested
the effectiveness of struvite residues obtained through acid decomposition, using
different kinds of acids. The authors proved that hydrochloric (HCl) and acetic acid
(CH 3 COOH) were highly effective in releasing ammonium at only 50 °C and pH 5.5.
Besides, they reported a cost saving of nearly 74% after reusing the decomposition
residues.
From a practical point of view, the applicability of those approaches is somehow
different from one case to another based on different aspects, such as the initial concentration of pollutants (NH 4 −N, P, Mg and heavy metals) and the applied reagents.
Moreover, the energy and manpower costs are rarely considered in the studies. The
marketing potentiality of struvite as a fertilizer is a vital issue that has to be counted,
because struvite is a slow-releasing fertilizer, which cannot be applied for all types
of plants. If the cost of struvite production is very high, the fertilizing industry would
prefer other kinds of P fertilizers that give the same fertilization efficiency as struvite, such as monocalcium phosphate (Ca(H 2 PO 4 ) 2 · H 2 O)) and dicalcium phosphate
(CaHPO 4 · 2H 2 O) (Hao et al. 2013). Furthermore, all related investment and running
costs should be studied carefully for each individual case, to be able to achieve a
complete economic feasibility assessment of the final product (Yetilmezsoy et al.
2017).
9.6.3 Research Need and the Way Forward
Considering the aspects mentioned in the previous sections, several research needs
should be highlighted. In general, a low-cost process of NH 4 −N recovery is one
of the main challenges that face the researchers in MAP technology. Applying the
waste bone ash, together with MgO, could be an efficient alternative replacing pure
chemicals. In fact, such combination has not been investigated before. Looking at the
effect of foreign ions, it seems that the interaction effect of pH, Mg:N molar ratio, K
and G value is not clear. Essentially, there is a need to understand more of this aspect,
to facilitate the application of MAP technologies in high-K wastewaters. Besides, as
wastewater contains high loads of organics, the influence of the individual organic
substances should be evaluated. Furthermore, some industrial wastewaters contain
high concentrations of heavy metals. Thus, the investigation of the potential effect
and sorption mechanism of these heavy metals is important, as heavy metals have
the ability to be included in MAP structure.
161
of NH 4 −N was removed at pH 6 and Cl/NH 4 −N wt. ratio of 8.2:1. Additionally,
more than 92% of NH 4 −N in LL could be removed using the recycled product, in
which nearby 34% of the chemical cost could be saved. Siciliano et al. (2016) tested
the effectiveness of struvite residues obtained through acid decomposition, using
different kinds of acids. The authors proved that hydrochloric (HCl) and acetic acid
(CH 3 COOH) were highly effective in releasing ammonium at only 50 °C and pH 5.5.
Besides, they reported a cost saving of nearly 74% after reusing the decomposition
residues.
From a practical point of view, the applicability of those approaches is somehow
different from one case to another based on different aspects, such as the initial concentration of pollutants (NH 4 −N, P, Mg and heavy metals) and the applied reagents.
Moreover, the energy and manpower costs are rarely considered in the studies. The
marketing potentiality of struvite as a fertilizer is a vital issue that has to be counted,
because struvite is a slow-releasing fertilizer, which cannot be applied for all types
of plants. If the cost of struvite production is very high, the fertilizing industry would
prefer other kinds of P fertilizers that give the same fertilization efficiency as struvite, such as monocalcium phosphate (Ca(H 2 PO 4 ) 2 · H 2 O)) and dicalcium phosphate
(CaHPO 4 · 2H 2 O) (Hao et al. 2013). Furthermore, all related investment and running
costs should be studied carefully for each individual case, to be able to achieve a
complete economic feasibility assessment of the final product (Yetilmezsoy et al.
2017).
9.6.3 Research Need and the Way Forward
Considering the aspects mentioned in the previous sections, several research needs
should be highlighted. In general, a low-cost process of NH 4 −N recovery is one
of the main challenges that face the researchers in MAP technology. Applying the
waste bone ash, together with MgO, could be an efficient alternative replacing pure
chemicals. In fact, such combination has not been investigated before. Looking at the
effect of foreign ions, it seems that the interaction effect of pH, Mg:N molar ratio, K
and G value is not clear. Essentially, there is a need to understand more of this aspect,
to facilitate the application of MAP technologies in high-K wastewaters. Besides, as
wastewater contains high loads of organics, the influence of the individual organic
substances should be evaluated. Furthermore, some industrial wastewaters contain
high concentrations of heavy metals. Thus, the investigation of the potential effect
and sorption mechanism of these heavy metals is important, as heavy metals have
the ability to be included in MAP structure.