PubMed · 5639332
The source did not provide an abstract. Follow the original record for more information.
Explore connections, maps & timelines
H L Everett. 1968. How an administrator evaluates a teaching program.. https://doi.org/10.3168/jds.s0022-0302(68)86973-5
Cite the original work for its findings. Save a collection to share your selection of sources.
KEEP EXPLORING
A stratified sand filter column, operated in recirculation mode and treating synthetic effluent resembling high-strength dairy wastewaters was studied over a 342-d duration. The aim of this paper was to examine the organic, total suspended solids (TSS) and nutrient removal rates of the sand filter, operated in recirculation mode, under incrementally increasing hydraulic and organic loading rates and to propose a field filter-sizing criterion. Best performance was obtained at a system hydraulic loading rate of 10 L m(-2) d(-1); a higher system hydraulic loading rate (of 13.4 L m(-2) d(-1)) caused surface ponding. The system hydraulic loading rate of 10 L m(-2) d(-1) gave a filter chemical oxygen demand (COD), TSS, and total kjeldahl nitrogen (TKN) loading rate of 14, 3.7, and 2.1 g m(-2) d(-1), respectively, and produced consistent COD and TSS removals of greater than 99%, and an effluent NO(3)-N concentration of 42 mg L(-1) (accounting for an 86% reduction in total nitrogen (Tot-N)). As the proportional surface area requirement for the sand filter described in this study is less than the recommended surface area requirement of a free-water surface (FWS) wetland treating an effluent of similar quality, it could provide an economic and sustainable alternative to conventional wetland treatment.
Increasing emphasis on maintaining environmental integrity by dairy operations warrants examination of management influence on waste characteristics. Complete profiles of anaerobic dairy lagoons for eleven operations in central Texas, distinguished by use of dry-lot and hybrid (i.e., facilities comprised of free stalls with smaller dry-lot areas) management systems, were analyzed for 15 physicochemical parameters. Although solids, pH and TKN values were similar between housing type, statistical differences in NH4-N, P, K, Mg, Na, Mn, Cu and electrical conductivity (EC) were observed. The discrepancies were attributed to dissimilar cattle activity, where cows spend more time near flush alleys in hybrid systems than dry-lot systems, which facilitates waste transport to anaerobic lagoons. These results suggest a possible difference in N dynamics between lagoon types, which in turn would have implications for NH3 volatilization. Potential salt-stress impact on both lagoon effectiveness and pastures receiving land-applied lagoon effluent may also be enhanced by hybrid systems. This study not only contributes data on anaerobic lagoon characteristics, but also provides additional considerations for dairy producers striving to meet more rigorous regulations while attempting to protect soil resources for crop production.
The removal of COD and oil-grease from dairy wastewater was experimentally investigated using direct current (DC) electrocoagulation (EC). In the EC of dairy wastewater, the effects of initial pH, electrolysis time, initial concentration of COD, conductivity and current density were examined. The COD and oil-grease in the aqueous phase were effectively removed when iron was used as sacrificial anode. The optimum operating range for each operating variable was experimentally determined. The batch experimental results revealed that COD and oil-grease in aqueous phase was effectively removed. The overall COD and oil-grease removal efficiencies reached 98 and 99%, respectively. The optimum current density, pH and electrolysis time for 18,300 mg COD/L and 4570 mg oil-grease/L were 0.6 mA/cm2, 7 and 1 min, respectively. Mean energy consumption was 0.003 kWh/kg of COD.