TWO-FACTOR DESIGN FOR COAGULANT /FLOCCULANT DOSES EFFECT FOR SOLID-LIQUID SEPARATION OF DAIRY MANURE

摘要

Screened dairy manure, with a total solids content equal to 34.7 g TS l~(-1), was subjected to a coagulation-flocculation treatment using FeCl_3 as coagulant and a medium cationic polyacrylamide (MCP1). The effect of changing doses of the additives (FeCl_3 and MCP1) on the properties of supernatant fractions was studied by means of design of response surface using 'Statgraphics Plus 3.0" program. The results showed that the values of concentrations found in supernatants obtained after settling of the flocs for two of the dependent variables studied, filtrate chemical oxygen demand (CODf) and total organic carbon (TOC), were significantly influenced by both the FeCl_3 and MCP1 doses at an error lower than 5%. The values of concentrations of the remaining variables studied (TS, VS, CODt, CODvfa) were significantly influenced only by the MCP1 dose at an error lower than 5%. The predictive model obtained the best satisfactory parameters for TOC supernatant's concentration (R~2=0.980, F-ratio=438.89 (p-value < 0.05)) and the worse for VS (R~2=0.783, F-ratio=33.43 (p-value < 0.05)).