Determination of ferric chloride dose to control struvite precipitation in anaerobic sludge digesters
1994; Wiley; Volume: 66; Issue: 7 Linguagem: Inglês
10.2175/wer.66.7.8
ISSN1554-7531
AutoresDaniel Mamais, Paul Pitt, Yao Cheng, Jon Loiacono, David Jenkins,
Tópico(s)Constructed Wetlands for Wastewater Treatment
ResumoABSTRACT: Anaerobic digestion of sludges favors the formation of struvite because ammonia, phosphate, and magnesium are solubilized by the digestion process. Struvite (MgNH 4 P0 4 · 6H 2 0 (s) ) can cause problems through scale formation. This paper provides a rational method for predicting the optimum FeCl 3 dose for preventing struvite formation during anaerobic digestion. Based on continuous flow anaerobic digestion experiments, the minimum dose to prevent struvite formation in the San Francisco Southeast Water Pollution Control Plant is 13.5 mM FeCl 3 /L or 100 kg FeCl 3 /ton total solids (TS). Approximately 68% of the total magnesium and total phosphorus present in the feed was available for chemical precipitation and the average ratio of soluble P0 4 ‐P removed to Fe added was 0.37. Additional iron demand was attributed to FeS (s) and FeC0 3(s) precipitation. Anaerobic sludge digestion batch studies showed similar soluble P0 4 ‐P removal efficiencies by FeCl 3 and FeS0 4 dosing, indicating that Fe(III) is reduced readily to Fe(II) in anaerobic sludge digesters.
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