The role of reactive chlorine and nitrogen species in micropollutant degradation in UV/monochloramine
Monochloramine (NH2Cl) is applied upstream of reverse osmosis (RO) membranes for biofouling control. Residual NH2Cl can undergo UV photolysis downstream, generating reactive species for an AOP to occur. At the bench-scale, NH2Cl is typically generated from combining sodium hypochlorite and ammonium...
| Main Authors: | , , |
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| Other Authors: | |
| Format: | Journal Article |
| Language: | English |
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2024
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| Online Access: | https://hdl.handle.net/10356/173319 |
| _version_ | 1826117179276263424 |
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| author | Seah, Zi Quan Leow, Shijie Snyder, Shane Allen |
| author2 | School of Civil and Environmental Engineering |
| author_facet | School of Civil and Environmental Engineering Seah, Zi Quan Leow, Shijie Snyder, Shane Allen |
| author_sort | Seah, Zi Quan |
| collection | NTU |
| description | Monochloramine (NH2Cl) is applied upstream of reverse osmosis (RO) membranes for biofouling control. Residual NH2Cl can undergo UV photolysis downstream, generating reactive species for an AOP to occur. At the bench-scale, NH2Cl is typically generated from combining sodium hypochlorite and ammonium chloride or sulfate. This study investigated the degradation of four compounds of interest - acetaminophen, caffeine, sucralose and 1,4-dioxane - in UV/NH2Cl at the bench scale to study their reactivity with reactive chlorine species (RCS) and reactive nitrogen species (RNS). With methanol acting as a scavenger of •OH radicals, the performance of UV/NH2Cl was compared to UV/H2O2 and UV/HOCl. In UV/H2O2, dioxane was severely inhibited at 1-2 mg/L H2O2 and comparable at 5 mg/L to UV/NH2Cl. When ammonium sulfate ((NH4)2SO4) was used as the ammonia source over ammonium chloride (NH4Cl), the overall degradation of micropollutants was higher and caffeine was exclusively degraded. At 1-2 mg/L NH2Cl, dioxane degraded by 16.2-17.8% and 2.92-5.29% from (NH4)2SO4 and NH4Cl respectively while caffeine degraded by 7.45-9.61% with NH2Cl ((NH4)2SO4), but not degrade with NH2Cl (NH4Cl). The higher concentration of chloride ions from NH4Cl significantly influenced the speciation of generated radicals and impacted micropollutant degradation. This suggests that the reactivity of more selective RCS (Cl2•-, •ClO, ClOH•-) and RNS (•NH2, •NO, •NO2, etc.) varies with micropollutants of interest. The presence of higher chloride concentration from the ammonia source inhibited the generation of •OH radicals with •OH consumed by RNS to form NO3- (μg/L levels), showing the impact of the choice of ammonia source and the water matrix on UV/NH2Cl performance. |
| first_indexed | 2024-10-01T04:23:24Z |
| format | Journal Article |
| id | ntu-10356/173319 |
| institution | Nanyang Technological University |
| language | English |
| last_indexed | 2024-10-01T04:23:24Z |
| publishDate | 2024 |
| record_format | dspace |
| spelling | ntu-10356/1733192024-01-24T03:06:26Z The role of reactive chlorine and nitrogen species in micropollutant degradation in UV/monochloramine Seah, Zi Quan Leow, Shijie Snyder, Shane Allen School of Civil and Environmental Engineering Nanyang Environment and Water Research Institute Engineering::Environmental engineering Advanced Oxidation Process Monochloramine Monochloramine (NH2Cl) is applied upstream of reverse osmosis (RO) membranes for biofouling control. Residual NH2Cl can undergo UV photolysis downstream, generating reactive species for an AOP to occur. At the bench-scale, NH2Cl is typically generated from combining sodium hypochlorite and ammonium chloride or sulfate. This study investigated the degradation of four compounds of interest - acetaminophen, caffeine, sucralose and 1,4-dioxane - in UV/NH2Cl at the bench scale to study their reactivity with reactive chlorine species (RCS) and reactive nitrogen species (RNS). With methanol acting as a scavenger of •OH radicals, the performance of UV/NH2Cl was compared to UV/H2O2 and UV/HOCl. In UV/H2O2, dioxane was severely inhibited at 1-2 mg/L H2O2 and comparable at 5 mg/L to UV/NH2Cl. When ammonium sulfate ((NH4)2SO4) was used as the ammonia source over ammonium chloride (NH4Cl), the overall degradation of micropollutants was higher and caffeine was exclusively degraded. At 1-2 mg/L NH2Cl, dioxane degraded by 16.2-17.8% and 2.92-5.29% from (NH4)2SO4 and NH4Cl respectively while caffeine degraded by 7.45-9.61% with NH2Cl ((NH4)2SO4), but not degrade with NH2Cl (NH4Cl). The higher concentration of chloride ions from NH4Cl significantly influenced the speciation of generated radicals and impacted micropollutant degradation. This suggests that the reactivity of more selective RCS (Cl2•-, •ClO, ClOH•-) and RNS (•NH2, •NO, •NO2, etc.) varies with micropollutants of interest. The presence of higher chloride concentration from the ammonia source inhibited the generation of •OH radicals with •OH consumed by RNS to form NO3- (μg/L levels), showing the impact of the choice of ammonia source and the water matrix on UV/NH2Cl performance. National Research Foundation (NRF) This work is funded by National Research Foundation Board (NRF) – Singapore, and administered by Public Utilities Board (PUB) – Singapore, under its RIE2025 USS (Water) Centre of Excellence (CoE) programme – RIE2025-CoE/NEWRI). 2024-01-24T03:06:26Z 2024-01-24T03:06:26Z 2024 Journal Article Seah, Z. Q., Leow, S. & Snyder, S. A. (2024). The role of reactive chlorine and nitrogen species in micropollutant degradation in UV/monochloramine. Chemosphere, 347, 140542-. https://dx.doi.org/10.1016/j.chemosphere.2023.140542 0045-6535 https://hdl.handle.net/10356/173319 10.1016/j.chemosphere.2023.140542 37926167 2-s2.0-85177190013 347 140542 en RIE2025-CoE/NEWRI Chemosphere © 2023 Elsevier Ltd. All rights reserved. |
| spellingShingle | Engineering::Environmental engineering Advanced Oxidation Process Monochloramine Seah, Zi Quan Leow, Shijie Snyder, Shane Allen The role of reactive chlorine and nitrogen species in micropollutant degradation in UV/monochloramine |
| title | The role of reactive chlorine and nitrogen species in micropollutant degradation in UV/monochloramine |
| title_full | The role of reactive chlorine and nitrogen species in micropollutant degradation in UV/monochloramine |
| title_fullStr | The role of reactive chlorine and nitrogen species in micropollutant degradation in UV/monochloramine |
| title_full_unstemmed | The role of reactive chlorine and nitrogen species in micropollutant degradation in UV/monochloramine |
| title_short | The role of reactive chlorine and nitrogen species in micropollutant degradation in UV/monochloramine |
| title_sort | role of reactive chlorine and nitrogen species in micropollutant degradation in uv monochloramine |
| topic | Engineering::Environmental engineering Advanced Oxidation Process Monochloramine |
| url | https://hdl.handle.net/10356/173319 |
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