1 research outputs found
Carbon and Phosphorus Removal from Primary Municipal Wastewater Using Recovered Aluminum
In
this work, recovery of aluminum from coagulated primary sludge
and its reuse potential as secondary coagulant were investigated.
The recovery process consisted of releasing the particle-bound aluminum
from primary sludge by acidification (HCl or H<sub>2</sub>SO<sub>4</sub>), followed by separation using centrifugation for dissolved coagulant
recovery. The recovered coagulant was then reused for treating primary
wastewater and overall coagulation efficiency was determined. While
with fresh alum, the removal efficiencies of total suspended solids,
chemical oxygen demand, total phosphorus, and total nitrogen were
85%, 65%, 80% and 33%, respectively, a drop in removal efficiency
of total suspended solids and chemical oxygen demand was observed
for recovered aluminum (85–60% and 65–50%, respectively).
Nitrogen concentration remained almost constant with each cycle, while
phosphorus in the effluent increased by 1 mg/L and 3 mg/L in the first
and second cycle, respectively. Precipitation of various aluminum
species was modeled for determining the recovery potential of aluminum
at low pH. Preliminary cost analysis indicates that optimum recovery
of aluminum occurred at a pH of 1.5 for both acids. Struvite precipitation
effectively removed increased phosphorus solubilized by acidification
at the end of second cycle, however, it also decreased the amount
of aluminum available for recycle