Phosphorus removal and recovery from dairy manure by electrocoagulation

Livestock manure waste, containing high level of phosphorus (P) will impair water environment if it is directly discharged to water body or improperly land applied. P recovery from animal manure not only addresses its environmental concerns, also provides a value added product as a fertilizer for better managing P. Electrocoagulation (EC) is proved to be an efficient approach that can be applied in the municipal and industrial wastewater for P removal and recovery; however, its application in the livestock manure management is less researched, especially with different selection of the electrode materials. In this study, EC process was evaluated on P removal and recovery from dairy manure. Four commonly seen electrodes, including Al, stainless steel, low carbon steel and cast iron, were compared. The results showed low carbon steel achieved the most efficient P removal (96.7%). The average particle size of manure solids was increased from 32.2 to 126.9 μm. The simulation experiment suggested that iron release and hydrolysis, which then worked as coagulants, is the major mechanism for P removal. EC by low carbon steel is an effective method for P separation from liquid phase of dairy manure to solid phase.