Disposal of livestock wastewater effluent (LWE) is a costly expense for dairy and hog farmers. The LWE contains high levels of orthophosphate (PO4-P), ammonium (NH4-N), nitrate (NO3-N), total suspended solids (TSS) and biochemical oxygen demand (BOD). These contaminants are regulated by the Clean Water Act, limiting the discharge of untreated LWE into surface water. One approach for disposal of LWE is to use it as a fertilizer, directly releasing untreated effluent to the topsoil of crop fields by spraying. This is a costly addition to farm production costs, and creates environmental problems such as leaching of NO3-N into groundwater, and deposition of particulate PO4-P to surface waters. As an alternative to direct reuse of LWE, reclamation of nutrients and water from LWE was evaluated using an aerated fluidized bed reactor (aerated-FBR), coupled with constructed wetland treatment (CWT). The aerated-FBR was used to precipitate PO4-P and NH4-N from LWE as struvite (MgNH4PO4●6H2O) fertilizer. Bench scale tests showed removal of 63-95% dissolved PO4-P from LWE, yielding a usable struvite and calcite (CaCO3) mixed fertilizer. Simultaneous thermal analysis (STA) coupled with Fourier transform infrared (FTIR) spectroscopy for evolved gas analysis (EGA) showed that the recovered solid was less susceptible to loss of NH4-N as ammonia gas (NH3(g)) compared to pure struvite. The aerated-FBR effluent was subsequently treated by CWT to reduce BOD and TSS levels to meet wastewater discharge requirements. The aerated-FBR-CWT process improves sustainability and reduces operation costs for livestock farmers by conversion of LWE to fertilizer for livestock crop production, and refurbished water for irrigation.

Reclamation of nutrients and irrigation waters from livestock wastewater

256th National Meeting (2018)

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