Using an angular detection photometer (ADP) in analyzing the humic acids coagulation process

Abstract

This paper presents a simply and novel design of an angular detection photometer (ADP) based on detection of infrared radiation from sources placed at various angles. The device allows for real-time monitoring of the coagulation process in in-situ samples. This paper assesses capabilities of the ADP compared with the standard method of the jar test in optimizing the coagulation process of humic acids in a synthetic raw water solution using Al2(SO4)3. Various parameters affecting the coagulation process were tested. The determined optimal doses were: 2.5, 3.5, 4.0 mg Al/L respectively for the reagent system: coagulation with pH adjustment, with polymers aid and for Al2(SO4)3 only. A 87.6 % reduction in A254 and 86.1 % reduction in A436 in a solution of humic acids using the optimum dose of Al2(SO4)3 at 4 mg of Al/L with pH = 6.95 was observed. Optimal process conditions (dose, pH) determined using an ADP match the parameters determined via the jar test method. Based on the standard deviation (SD) of measurement signal fluctuation, a linear relationship with R2 = 0.84 was observed between the SD and sedimentation time of post-coagulant suspensions. In-situ qualitative studies have shown that macromolecular polymers: anionic and nonionic polyacrylamides exhibit strong flocculation abilities with formation of larger particles, respectively SD = (7.3–10.7) and SD = (9.7–19.7), than the cationic polyacrylamide, SD = (1.4–2.1). It was proved that measurements of particle dispersion, regardless of the angle of incidence of the light beam, are justified in analyzing coagulation and can therefore complement analytical procedures used when optimizing the coagulation process.