The practical meaning of the classical optimizing method and Angular Detection Photometer (ADP) in coagulation tests of surface water

Abstract

Because of the growing deficit of clean water, rational use of its supplies through adaptation of purification techniques to the needs is becoming vital. The commonly used coagulation process requires optimization tools and techniques. The following were used in this paper to optimize coagulation of natural water pollutants: the standard jar test method with direct filtration and the angular detection photometry (ADP) method. We tested two aluminium coagulants – PAC with different basicity – and an iron coagulant: PFS. A modified jar test method allowed to obtain results similar to those of the sedimentation method. At the optimum doses 1.3 mg Al/mg C org. and 2 mg Fe/mg Corg – colour (PtCo), A254, A436 – achieved reduction in the 84–96% range and DOC 60–67% after filtration. The titration method using an ADP successfully allows determine optimum coagulant doses. The SD and FI values were determined based on the recorded fluctuations of the signals measured by detectors placed at three angles relative to the IR beam. A variation in SD was observed, depending on the angle of detection and the coagulant and correlates well (R2 =0.6–0.86) with sedimentation time ST, which was twice as long in the case of fine suspension in the PFS.