Effect of different technologies and animal manures on solid-liquid separation efficiencies

Solid-liquid separation is a widely used manure treatment option. However, little information is available to predict separator performance in a specific operating condition. This study investigates the effect on the separation efficiency of animal species (cattle and swine), use of flocculants, and separator construction and operating characteristics (filtration, pressurised filtration, settling and centrifugation). Using data available from published experiments, we evaluated correlations of the separation efficiencies with the physical and chemical characteristics of the inlet slurries (dry matter, total nitrogen, ammoniacal nitrogen, phosphorus and potassium). Dry matter concentration of the input manure was found to be the best parameter used to calculate and validate regression equations. Regres sions for the operating conditions of 7 of the 14 subgroups evaluated were significant (P<0.05) for at least one parameter. Pressurised filtration seems to be the process best represented by these regressions that can predict dry matter and nitrogen efficiency with relative root mean squared errors of less than 50%. However, they could only be used for some of the parameters and separation techniques. Therefore, it was not possible to use the available experimental data to define and validate empirical predictive models for all the conditions. Specific studies are needed to define more precise and physically-based models.