EVALUATION OF WEEPING WALL EFFICIENCY OF SOLID LIQUID SEPARATION

Abstract

The objectives of this project were to evaluate the effectiveness of a settling basin with large dewatering surface area (weeping wall separation system) in removing total solids (TS) and fixed solids (FS) and to characterize particle size and nutrient content of influent and effluent streams. The study was conducted on an 1100 cow commercial dairy in California. A total of 350 influent and 77 effluent samples were obtained from a total of 20 flushes collected over four sampling periods. Influent mean percent TS concentrations within a flush were variable and ranged from 0.37 +/- 0.01% to 1.95 +/- 0.67% TS for an overall influent TS mean of 1.52 +/- 0.53% TS. Fixed solids ranged from 37.02 +/- 1.02% to 45.92 +/- 2.88% of TS. The corresponding values for TS concentration in effluent samples were less variable and ranged from 0.46 +/- 0.03% to 0.71.0.26% TS and FS ranged from 37.68 +/- 1.91 to 43.47 +/- 1.11% of TS. Percent of TS removed was 63.41%, 59.65%, 63.07%, and 49.29% for each sampling period. Mean electrical conductivity of influent and effluent samples was not different 4.33 +/- 0.37 and 4.16.0.23 mS cm-1, respectively. Particle size fractionation was conducted on 39 influent and 15 effluent samples. Screen sizes were 2, 1, 0.5, 0.25, 0.125 mm. Percent of influent TS retained on each screen was 10.48, 12.26, 13.80, 14.27 and 18.28, respectively (30.90% of influent TS passed through the 0.125-mm screen). Percent of effluent TS retained on each screen was 0.63, 1.79, 3.45, 5.43, and 8.18, respectively (80.51% of effluent TS passed through the 0.125-mm screen). Although mass was removed by the separation system the nutrient concentrations of soluble elements (NH4-N+, K, P, Ca, Mg, Na, and Cl) in representative influent (n = 14) and effluent (n = 4) samples were not different. Concentration of organic-N was not different between select influent (184 +/- 49) and effluent (223 +/- 46) samples analyzed.