COMPARISON OF COAGULANT DOSES DETERMINED USING A CHARGE TITRATION UNIT WITH A JAR TEST PROCEDURE FOR 8 GERMAN SURFACE WATERS

Doses of alum coagulant [Al-2(SO4)(3).18H(2)O] for the treatment of ei ght surface waters from west Germany were determined using a charge ti tration unit (CTU) that included a streaming current detector and a ja r rest procedure for comparison of these two methods. Water samples do sed with alum and analysed using the CTU were tested at pH 6.5, while jar tests were performed with pH control at 6.5 and without pH control . Alum doses determined using the jar test were slightly higher for wa ters with low DOC concentrations and lower for one water with a high D OC concentration than those determined using the CTU. Alum doses deter mined using the jar test without any pH control were mostly similar to doses determined where the pH was controlled at 6.5, based on turbidi ty parameters. However, where the pH was not controlled, higher residu al aluminium and dissolved organics (as measured by absorbance at 254 nm/cm) were generally found in the treated waters.