{"title":"Quantifying drought-driven temperature impacts on ozone disinfection credit and bromate control†","authors":"Bilal Abada, Ariel J. Atkinson and Eric C. Wert","doi":"10.1039/D4EW00042K","DOIUrl":null,"url":null,"abstract":"<p >Climate change and drought can lead to unprecedented changes in surface water temperature requiring utilities to examine their ozone system's disinfection capability while minimizing bromate production. This pilot-scale study investigated temperature (15–30 °C) as a single/isolated variable affecting ozone operating performance (demand, decay rate, exposure (CT)) and the ability to achieve a <em>Cryptosporidium</em> log reduction value (LRV) of 0.5–1.5 logs, as defined by the United States Environmental Protection Agency (USEPA). When dosing 3.0 mg L<small><sup>−1</sup></small> of ozone into a surface water with 2.5 mg L<small><sup>−1</sup></small> of total organic carbon, an increase in temperature from 15 °C to 30 °C increased ozone demand in the dissolution zone from 1.0 mg L<small><sup>−1</sup></small> to 1.6 mg L<small><sup>−1</sup></small> (60%) and ozone decay rate from 0.07 min<small><sup>−1</sup></small> to 0.27 min<small><sup>−1</sup></small> (385%). Despite more rapid demand/decay, the required ozone dose to achieve an LRV of 1.5 logs remained at 2.4–2.8 mg L<small><sup>−1</sup></small> due to the reduction in USEPA's CT requirement at higher temperatures (9.35 mg min L<small><sup>−1</sup></small> at 15 °C <em>vs.</em> 2.31 mg min L<small><sup>−1</sup></small> at 30 °C). Bromate formation exceeded the USEPA maximum contaminant level of 10 μg L<small><sup>−1</sup></small> when ozone was dosed to achieve LRV > 0.5 log at all temperature conditions. Chlorine–ammonium pretreatment (0.5 mg L<small><sup>−1</sup></small> Cl<small><sub>2</sub></small>, 0.1–0.5 mg L<small><sup>−1</sup></small> NH<small><sub>4</sub></small><small><sup>+</sup></small>-N) lowered bromate formation to <5 μg L<small><sup>−1</sup></small> under ambient (80 μg L<small><sup>−1</sup></small>) and elevated (120 μg L<small><sup>−1</sup></small>) bromide concentrations at all temperatures. These results were applied to evaluate a full-scale ozone system designed to achieve an LRV of 1.5 logs if drought increases temperature from 13 °C to 26 °C. The study systematically examined the role of temperature on ozone system performance, which can assist utilities planning for future drought-driven changes.</p>","PeriodicalId":75,"journal":{"name":"Environmental Science: Water Research & Technology","volume":null,"pages":null},"PeriodicalIF":3.5000,"publicationDate":"2024-04-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://pubs.rsc.org/en/content/articlepdf/2024/ew/d4ew00042k?page=search","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Environmental Science: Water Research & Technology","FirstCategoryId":"93","ListUrlMain":"https://pubs.rsc.org/en/content/articlelanding/2024/ew/d4ew00042k","RegionNum":4,"RegionCategory":"环境科学与生态学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q3","JCRName":"ENGINEERING, ENVIRONMENTAL","Score":null,"Total":0}
引用次数: 0
Abstract
Climate change and drought can lead to unprecedented changes in surface water temperature requiring utilities to examine their ozone system's disinfection capability while minimizing bromate production. This pilot-scale study investigated temperature (15–30 °C) as a single/isolated variable affecting ozone operating performance (demand, decay rate, exposure (CT)) and the ability to achieve a Cryptosporidium log reduction value (LRV) of 0.5–1.5 logs, as defined by the United States Environmental Protection Agency (USEPA). When dosing 3.0 mg L−1 of ozone into a surface water with 2.5 mg L−1 of total organic carbon, an increase in temperature from 15 °C to 30 °C increased ozone demand in the dissolution zone from 1.0 mg L−1 to 1.6 mg L−1 (60%) and ozone decay rate from 0.07 min−1 to 0.27 min−1 (385%). Despite more rapid demand/decay, the required ozone dose to achieve an LRV of 1.5 logs remained at 2.4–2.8 mg L−1 due to the reduction in USEPA's CT requirement at higher temperatures (9.35 mg min L−1 at 15 °C vs. 2.31 mg min L−1 at 30 °C). Bromate formation exceeded the USEPA maximum contaminant level of 10 μg L−1 when ozone was dosed to achieve LRV > 0.5 log at all temperature conditions. Chlorine–ammonium pretreatment (0.5 mg L−1 Cl2, 0.1–0.5 mg L−1 NH4+-N) lowered bromate formation to <5 μg L−1 under ambient (80 μg L−1) and elevated (120 μg L−1) bromide concentrations at all temperatures. These results were applied to evaluate a full-scale ozone system designed to achieve an LRV of 1.5 logs if drought increases temperature from 13 °C to 26 °C. The study systematically examined the role of temperature on ozone system performance, which can assist utilities planning for future drought-driven changes.
期刊介绍:
Environmental Science: Water Research & Technology seeks to showcase high quality research about fundamental science, innovative technologies, and management practices that promote sustainable water.