Electrocoagulation of Dairy Manure Using Low-Carbon Steel Electrodes for Phosphorus Removal

Abstract

With the recent trend of increasing size for the dairy operations, dairy manure, due to its high content of phosphorus and relatively low nitrogen/phosphorus ratio, is limited when applied in the area where phosphorus is saturated in the soil. Electrocoagulation is a potential method to treat dairy manure for phosphorus removal and the operation parameters of this process can significantly affect the process efficiency. In this study, an 800 mL electrocoagulation reactor equipped with low carbon steel electrodes was investigated on its operation parameters, including current, agitation speed, initial pH, aeration time, and anaerobic digestion as pretreatment. The results showed that higher current and higher initial pH could improve the phosphorus removal efficiency. Agitation assisted the formation of coagulants, but high speed of agitation did not contribute further separation and removal of phosphorus. Pretreatment, i.e., aeration or anaerobic digestion before electrocoagulation, was beneficiary for phosphorus removal. The suggested operation parameters are with current under 1 A, agitation of 75 rpm, and higher initial pH. Pretreatment with 10 days of anaerobic digestion or 60 min of aeration before electrocoagulation is also recommended, and phosphorus removal efficiency in this condition can reach 97%. Overall, electrocoagulation with low carbon steel electrodes is an efficient method to remove phosphorus in dairy manure, and the process may potentially reduce the environmental impact of dairy operations on local water systems and increase the manure application scope and its competitiveness compared with chemical fertilizers.