Page 223 - Materials Chemistry, Second Edition

204 Life Cycle Assessment of Wastewater Treatment

adsorption, phycoremediation using algae was examined for the removal of phospho-
rus from wastewater generated from high–organic content wastewater. A filamentous
microalga having high autoflocculation competence along with immobilized cells
was studied for the removal and recycling of phosphorus in this integrated system
(Olgui, 2003). Phosphorus-contaminated runoff water from a simulated plant nursery
in Australia was treated using subsurface horizontal flow reed beds (Huett et al., 2005).
Pratt and his team attempted to remove phosphorus from effluent generated from a
waste stabilization pond using melter slag filter. The results indicated that adsorption
of phosphorus was taking place on the surface of the slag, which contained metal
oxides and oxyhydroxides (Pratt et al., 2007). Szogi and researchers developed a novel
process for removal of the phosphorus from livestock effluent generated from a swine
lagoon. The new treatment included bionitrification followed by the precipitation of
phosphorus by increasing the pH of the contaminated effluent. Along with this, solid
residual calcium phosphate was generated from the process, which could be reused
as fertilizer in the farms (Szogi et al., 2009). A chemical precipitation method was
adopted by Naseef (2012) during the removal of phosphorus from industrial wastewa-
ter. Lanthanum compounds doped with natural materials such as red mud, bentonite,
zeolite, and montmorillonite have been used by several researchers as highly activated
species for phosphorus adsorption. But still, these are not widely available and are not
economically viable. An efficient adsorbent was developed using a by-product (lithium
silica fume) from the silicon industry, which was found to be highly effective in remov-
ing phosphorus from wastewater (Xie et al., 2016).
Wetlands are often constructed for the treatment of different phosphorus-contain-
ing industrial effluents, employing several natural and modified filters. Phosphorus
from a subsurface flow constructed wetland was adsorbed by bed-sand medium. The
choice of the sand best suited for effective removal of phosphorus was governed by
the calcium content. After a variety of sands, clay aggregates, powdered marbles,
and so on were examined, calcite and marble were considered to have high phospho-
rus-binding abilities. The authors suggested that the addition of calcite or marble to
sand may considerably increase the uptake of phosphorus, thereby removing phos-
phorus from constructed wetlands (Brix et al., 2001).
Both serpentinite and modified and unmodified steel slag obtained from an elec-
tric arc furnace were investigated for their adsorption capacity for the adsorption of
phosphorus from wastewater. Steel slag showed 100% efficiency in adsorbing phos-
phorus due to the presence of metal hydroxides and precipitation of hydroxyapatite.
It was found that lime-doped steel slag and serpentinite had lower efficacy. Steel
slag was concluded to be the promising solution for removal of phosphorus from
constructed wetlands and filter beds using adsorption followed by a precipitation
mechanism (Drizo et al., 2006). Vymazal (2007) suggested harvesting of above-
ground biomass of emergent vegetation to be the best solution for the elimination
of phosphorus from wetlands at low concentrations. A hydrated oil-shale ash sedi-
ment obtained from a thermal power plant was employed to remove phosphorus from
constructed wetlands in Estonia. Batch experiments resulted in a high phosphorus
uptake capacity of about 67%–85%. The adsorption capacity of the material was
due to the presence of reactive calcium minerals (Kaasik et al., 2008). Phosphate
is considered to be one of the major pollutants in wetlands (Naushad et al., 2018).