Development and application of continuous monitoring system size flakes in order to optimize the coagulation/flocculation and filtration

Abstract

The objective of this study is to evaluate the floc size formed during the flocculation step in Water Treatment Plants (WTP), its shear strength and the capacity of the sheared floc (breakage) to return to its original size (reversibility) using a metal coagulant (alum), that is the same one applied in the WTP located in Sao Jose dos Campos, Sao Paulo, Brazil - and two polymeric flocculants - nonionic (the same one used in the WTP located in Sao Jose dos Campos), and cationic (the same one used in dewatering of sewage sludge in the Lavapés Wastewater Treatment Plant). For this propose, some modified jar test experiments will be used, in which jar test will be connected to the equipment for continuously monitoring the flocculation process. This equipment was previously developed by another researcher of the same research group. Firstly, a mother-suspension of kaolinite will be prepared, then diluted with groundwater taken from the water well located in DCTA, Sao Jose dos Campos, Sao Paulo, Brazil, so that a turbidity of 25 NTU can be obtained, resulting in a study water. After that, the pair of value 'coagulant dosage x coagulation pH' will be optimized by performing tests using the traditional procedure of jar test; in this stage, it will be used the metal coagulant (alum). Using the pair of values previously defined, some tests concerning the dynamic monitoring of flocculation will be conducted, by applying the metal coagulant independently and also combining the coagulant with the two polymers. The breakage velocity gradient will be varied in order to evaluate the integrity of flocs when they are under shear forces typical of those occurring when water flows through a Rapid-Gravity Filter (RGF). (AU)