N2 yields from monochloramine conversion by granular activated carbons are decisive for effective swimming pool water treatment

Abstract

Inorganic chloramines (mono-, di-and trichloramine) are formed in swimming pool water from the unintended reaction of free chlorine with ammonia that is introduced by bathers. Monochloramine is of particular interest as it is known to react further in pool water forming harmful DBPs, such carcinogenic N-nitrosodimethylamine (NDMA). During pool water treatment with granular activated carbon (GAC) filters, monochloramine is transformed by chemical reactions on the carbon surface to N 2 and ammonia. As ammonia is led back into the pool where it is chlorinated again under the renewed formation of inorganic chloramines, it is recommended to use GACs with a high N 2 yield for monochloramine transformation in pool water treatment.In this study, yields of N 2 and ammonia from monochloramine conversion by commercially available GACs were determined using a fixed-bed reactor system under conditions that are typical for swimming pool water treatment. The N 2 yields remained constant with on-going exposure of the GAC to monochloramine and ranged from 0.5% to 21.3%, depending on the type of GAC used. Correlation analyses were conducted to identify carbon properties that can determine the N 2 yield for monochloramine conversion, such as the amount of oxygen groups, the elemental composition and the trace metal content. It was found that the N 2 yield significantly correlates with the copper content of the tested carbons.Model calculations combining pool hydraulics with formation/abatement of inorganic chloramines and NDMA as well as chloramine transformations in GAC filters showed that the concentration of inorganic chloramines and carcinogenic NDMA can be

Impact of Different Combinations of Water Treatment Processes on the Concentration of Disinfection Byproducts and Their Precursors in Swimming Pool Water

“…Differences in the removal efficiencies between free chlorine and combined chlorine could be explained by the different reaction rates reported for their surface reaction with carbonaceous materials. 73,74 UV(LP) irradiation at the doses applied in this study (Table B.1 (SI)) reduced less-volatile DBPs and combined chlorine than did UV(MP) irradiation. These findings agree with previous results, where it has been shown that concentration levels of THMs could not be reduced by UV(LP) treatment, 75 while a minor mitigation of THMs in pool water has been observed for UV(MP) treatment.…”

“…The layer of PAC on the UF or in the sand filter removed a significant amount of combined chlorine (PAC–sand, 28.2 ± 7.4%; PAC–UF, 38.6 ± 12.6%) but also free chlorine (∼100%). Differences in the removal efficiencies between free chlorine and combined chlorine could be explained by the different reaction rates reported for their surface reaction with carbonaceous materials. , …”

A novel microwave air heater integrated with thermal energy storage

“…Activated carbon (AC) is widely used in gas storage, 1 food, and beverage processing, 2 as an adsorbent for air and water treatments, 3,4 metal recovery, 5 and medical treatments 6 . However, there is limited research on the application of AC for thermal energy storage 7,8 .…”