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A Study on Analytical Techniques and Statistical Design for Tertiary Treatment of Secondary Wastewater Using Zetag-4120 Coagulant
The primary and secondary wastewater treatments from different sewage treatment plants are of great importance not only for removing pollutants but also for using treated water for different purposes. The latter involves using suitable coagulants and their optimal dosages for the treatment. Given this, the present study identified the most suitable coagulant for tertiary treatment and its optimal dosage to achieve the maximum total suspended solids (TSS) and biological oxygen demand (BOD) removal. We used six coagulants (alum, ferric chloride, polyaluminium chloride (PAC), Zetag4120, Mecafloc-25 and Rothfloc-27) and found that Zetag-4120 is the cost-efficient coagulant at varying coagulant dosage. We arrived at this conclusion based on several experiments using varying coagulant dosages. Furthermore, the regression prediction models for BOD and TSS removal for coagulant Zetag-4120 have been generated using statistical models and validated by calculating R2 value, F-test and Lack-of-fit test using ANOVA. Optimization analysis suggests the optimal dosage, initial wastewater pH and settling time to be 1.86 mg/l, 6.73 and 89.12 min respectively. Furthermore, BOD and TSS removal efficiency values are 50.0% and 92.4% respectively. The treated wastewater has BOD and TSS equal to 12.27 and 5.66 mg/l respectively, conforming to the standard for re-usability of treated water for unrestricted irrigation.
Keywords
Polyelectrolytes, regression prediction model, response surface methodology, tertiary wastewater treatment, Zetag-4120.
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