Evaluation of a Weeping Wall Solid-Liquid Separation System for Flushed Dairy Manure

Abstract

A two-stage weeping wall solid-liquid separation system was evaluated to assess its solids and nutrient retaining/capturing capabilities at a cooperating dairy in east central Texas. The dairy had 3,500 lactating cows in six free-stall barns bedded with sand. Flow measurements and liquid samples were taken simultaneously at four locations; a channel where flushed manure from free-stalls flowed into a chamber of the first stage (primary chamber), an outlet where effluent from the primary chamber flowed into a concrete storage tank, a pipe inlet where effluent from the tank was pumped into the second stage (secondary chamber) weeping wall, and the outlet where effluent drained out from the secondary chamber. Flow measurements and liquid sample collection at these locations were carried out at 5 and 10 min intervals for high and low flow rates, respectively. Samples were analyzed for total solids (TS), total volatile solids (TVS), Total Kjeldahl nitrogen (TKN), phosphorous (P), and potassium (K). Solid and nutrient concentrations were significantly higher in untreated flushed manure flowing into the primary chamber than those in the treated effluent from the secondary chamber. Estimated overall percent reduction in TS, TVS, TKN, P, and K concentrations were 35%, 40%, 10%, 18%, and 7%, respectively. In the primary chamber, estimated capture efficiencies for TS, TVS, TKN, P, and K were 67%, 67%, 60%, 55%, and 54%, respectively. Overall capture efficiencies for TS, TVS, TKN, P, and K were 88%, 89%, 84%, 86%, and 84%, respectively. This study showed that a two-stage weeping wall system can be effectively used for solid-liquid separation of flushed dairy manure.