This conference paper was presented at 5th International Conference on Advances in Civil Engineering (ICACE 2020).
Date: 4th March, 2021
Presenter: Tahsina Alam
Author: Ishrat Rashid, Tahsina Alam, Tasnim Ahmed, Dr. Muhammad Ashraf Ali
Proceeding Link: icacecuet.org/P...
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Abstract
Precipitation of CaCO3 has long been a concern in water treatment/distribution systems; however, this problem has been identified only recently in some areas (e.g., Meherpur) of Bangladesh. Scaling is the most obvious manifestation of CaCO3 precipitation in water distribution systems, resulting in flow restrictions and head lossand accelerates equipment depreciation. Globally, the scaling issue is reemerging due to climate change. The potential methods for control of CaCO3 precipitation in the context of Bangladesh include lowering of pH, removal of Ca, and delaying/preventing precipitation using scale inhibitor. Lowering of pH adversely affects removal of iron (and also arsenic). Removal of Ca by raising pH has a number of major operational difficulties, while removal of Ca by other means (e.g. ion exchange resins) at municipal/city scale often becomes prohibitively expensive. This study presents an assessment of the potential effectiveness of Zn as scale inhibitor in delaying precipitation of CaCO3 in water treatment and distribution system. Effect of Zn on precipitation of CaCO3 was evaluated as a function of Zn concentration (varying from zero to 5 mg/l), mixing time (varying from 30 minutes to 5 hours), and the degree of super-saturation (varying from about 3 to 10). For a particular degree of super-saturation and mixing time, precipitation of CaCO3 decreased as Zn concentration increased. One interesting observation from the experiments was the positive effect of increased mixing time on inhibitor performance. Results for this study suggests that Zn applied at low doses (complying with drinking water standard of 5 mg/l) could effectively prevent/delay CaCO3 precipitation/scaling in water treatment and distribution.
Keywords
CaCO3, Scale, Inhibitor, Zinc
11 сен 2024
