Remove and recover phosphorus during anaerobic digestion of excess sludge by adding waste iron scrap
2013
In the current investigation, the feasibility of phosphorus removal in the
anaerobic digestion of excess sludge by adding waste iron scrap (WIS) was
studied. The results show that the removal efficiency of phosphorus increases
with the amount of WIS, and the maximum removal efficiency could reach 39%,
93% and 99% at WIS dosages of 1, 2 and 3 g/L, respectively. Sterilization
greatly decreases the removal efficiency of phosphorus, having only -6%, 53%
and 64% at WIS dosages of 1, 2 and 3 g/L, respectively. This means that
iron-reducing bacteria and hydrolytic bacteria enhance 45%, 40% and 35% of
phosphorus removal at WIS dosages of 1, 2 and 3 g/L, respectively. The first
and the most important mechanism of phosphorus removal using WIS is
hydrolytic bacteria, which reduce the pH of sludge to corrode the WIS,
followed by precipitation of phosphorus by ferrous iron generated from the
iron-reducing bacteria. Phosphorus adsorption onto the WIS is the second
probable mechanism. The removed phosphorus is recovered up to 56% using
magnet. This method is characterized by high removal efficiency, easy and
steady operation, low cost, recovery and reuse, making it better than other
physical and chemical treatments.
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