Anna Nowacka, Maria Włodarczyk-Makuła
The purpose of the present study was to compare the effectiveness of coagulation process conducted using classical non-hydrolyzed coagulant - aluminum(VI)sulfate and pre-hydrolyzed coagulants: Flokor1ASW/B and Flokor 105 V. Water samples subjected to coagulation were collected from selected water treatment plant after pre-ozonation process. Instantaneous samples were taken in winter season. True colour of water amounted 7.0 mg Pt/L and turbidity was 7.29 NTU. The study in laboratory scale was carried out with the usage of a six beaker flocculator. Volumetric coagulation was performed in water samples of the volume of 1 L. In six beakers, rapid-mixing (3 min at the rotational speed of 200 rpm) was followed by 30 min slow mixing (at 30 rpm). After coagulation the samples were subject to 60 min sedimentation. The coagulant dose was optimized for minimum colour, turbidity and UV254 absorbance values using conventional jar testing procedures. The coagulation performance was examined with a range of dosages 0.4-1.4 mg Al/L for pre-hydrolyzed coagulants. In case of aluminum(VI)sulfate ranged from 1.6-2.6 mg Al/L. The optimum dose for aluminum(VI)sulfate amounted 2.2 mg Al/L. For prehydrolyzed coagulants, the doses were much lower, i.e. 1.4 mg Al/L. Also less wear of water alkalinity was obtained than in case of aluminum(VI)sulfate. The effectiveness of removal of turbidity for ALK, Flokor 1ASW/B and Flokor 105V was 62.6%, 73.0% and 69.0% respectively. Effectiveness of coagulants was compared on the basis of concentration of selected water quality indicators (turbidity, absorbance at 254 nm) after coagulation process (for optimal doses). For the assessment if the differences were statistically significant Student's t test for difference of two independent trials was used. In all examined cases it was found that the use of different types of coagulants is statistically significant for the achieved effects of coagulation. Calculated values were higher than theoretical. (td>tt). The use of pre-hydrolyzed aluminum coagulants improves the efficiency of the coagulation process, and reduce the wear of coagulants in comparison with previously used aluminum(VI)sulfate. After application of Flokor 1ASW/B the best results (among the investigated coagulants) for the chosen contaminant removal were obtained, more than 46,3% decrease of DOC and 75,0% decrease of UV254 absorbance.
koagulanty glinowe, jakość wody, absorbancja
Impact of Selected Pre-Hydrolyzed Aluminum Coagulants on Improving of Treated Water Quality
aluminum coagulants, water quality, absorbance
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