Phosphorus reduction in dairy effluent through flocculation and precipitation
Abstract
Phosphorus (P) is a pollutant in freshwater systems because it promotes eutrophication. The dairies in the North Bosque and its water body segments import more P than they export. Dairies accumulate P-rich effluent in lagoons and use the wastewater for irrigation. As more P is applied as irrigation than is removed by crops, P accumulates in the soil. During intense rainfall events, P enters the river with stormwater runoff and can become bio-available. Reducing the P applied to the land would limit P build up in the soil and reduce the potential for P pollution. Since wastewater P is associated with suspended solids (SS), the flocculants, poly-DADMAC and PAM, were used to reduce SS. To precipitate soluble P from the effluent, NH4OH was added to raise the pH. Raw effluent was collected from a dairy in Comanche County, TX, and stored in 190-L barrels in a laboratory at Texas A&M University. Flocculant additions reduced effluent P content by as much as 66%. Addition of NH4OH to the flocculated effluent raised the pH from near 8 to near 9, inducing P precipitation, further reducing the P content. The total P reduction for the best combination of treatments was 97%, a decrease from 76 to 2 mg L-1. If this level of reduction were achieved in dairy operations, P pollution from effluent application would gradually disappear.
Subject
manurephosphorus
flocculation
precipitation
dairy effluent
eutrophication
dairy wastewater treatment
Citation
Bragg, Amanda Leann (2003). Phosphorus reduction in dairy effluent through flocculation and precipitation. Master's thesis, Texas A&M University. Texas A&M University. Available electronically from https : / /hdl .handle .net /1969 .1 /1646.