Chlorination breakpoint with nitrite in wastewater treatment: A full factorial design experiments. Issue 1 (February 2021)

• Record Type: Journal Article
• Authors: Khawaga, Rehab; Abouleish, Mohamed; Abdel Jabbar, Nabil; Al-Asheh, Sameer
• Is Part Of: Journal of environmental chemical engineering. Volume 9:Issue 1(2021)
• Publication Date: 2021-02
• Subjects: Chlorination -- Disinfection -- Breakpoint chlorination -- Ammonia-nitrite system -- Wastewater treatment; Chemical engineering -- Environmental aspects -- Periodicals; Environmental engineering -- Periodicals; Chemical engineering -- Environmental aspects; Environmental engineering; Periodicals; 660.0286
• DOI: 10.1016/j.jece.2020.104903
• Languages: English
• ISSNs: 2213-2929

Abstract

Abstract: Contamination of wastewater increases chlorine demand and alter chlorine and ammonia reaction, and affect breakpoint curve. To determine most influential operating variable(s) on breakpoint chlorination, a previously developed model was used in this research, using three input factors (ammonia, nitrite, and contact time), using a three-way four-level factorial design. To reflect on shape of breakpoint curve and depict any changes on chlorination profile, response variables such as, initial slope, maximum TRC, minimum TRC, and length of combined region, were used. Lenvene's test for factorial analysis for all response variables indicated unequal variances and confirmed that homogeneity of variance has not been met, i.e. all response variables have different variability across the three input factors. Although ANOVA results expressed no statistically significant three-way interaction between the three factors on response variables, yet different results for two-way interaction effect, main effect and independent effect between input factors, was exhibited. For example, results showed that contact time influenced disinfection system, and that higher ammonia concentration results in faster NH2 Cl destruction. In addition, this research indicated that ammonia and nitrite might have different effects on chlorination curve depending on A/N ratio, e.g. ammonia at a relatively higher concentration, suppresses effect of nitrite on rising leg and this is in agreement with literature. This study determined the ratio around which this phenomenon occurs (A/N ratio around 3). Graphical Abstract: ga1 Highlights: A mechanistic model for chlorination breakpoint in ammonia-nitrite system was used. The model used 3-way factorial to study ammonia, nitrite, and contact time The response variables are initial slope & length of combined region, and TRC. Ammonia/Nitrite ratio is 3, indicating predominance ammonia effect on chlorination. The factorial designs outcome support dynamic analysis and agreed with literature.