In November 2012, the Beaver Water District (BWD) switched primary oxidants from free chlorine to chlorine dioxide (ClO2) to curb formation of trihalomethanes, a regulated group of organic disinfection byproducts (DBPs). Because ClO2 is reduced to chlorite (ClO2-), a regulated inorganic DBP, BWD incorporated ferrous salt into their coagulation regime to quench chlorite to chloride. In this study, two ferrous salts - ferrous chloride (FC) and ferrous sulfate (FS) - were compared as secondary coagulants in combination with alum, the primary coagulant. Ferrous salts were dosed stoichiometrically to reduce chlorite and alum was dosed at percentages (0-100%) relative to a typical alum dose at the BWD, 30 mg/L as alum. Settled water turbidity, dissolved organic carbon (DOC), chloride to sulfate mass ratio (CSMR), solids settleability, and water filterability were assessed in laboratory scale bench tests and pilot plant studies as a function of percent alum dose reduction (ADR). Results from bench scale jar tests and pilot plant study showed that settled water turbidity and DOC were not compromised up to ~40% ADR (18 mg/L as alum) and were indifferent to the type of ferrous salt added. As expected, CSMR, a corrosion surrogate, increased with increasing ADR (or decreasing sulfate addition) and was higher for the FC-treated waters compared to the FS-treated waters. However, CSMR remained below the suggested threshold of 0.6 for ADR values up to 60%, indicating both ferrous salts were viable options for chlorite quenching at BWD. Notably, the headloss rate during filtration in the pilot plant study was lower for the FS-treated waters at all values of ADR tested, and thus is the recommended secondary coagulant for the BWD.
","abstract_html":"<p>In November 2012, the Beaver Water District (BWD) switched primary oxidants from free chlorine to chlorine dioxide (ClO2) to curb formation of trihalomethanes, a regulated group of organic disinfection byproducts (DBPs). Because ClO2 is reduced to chlorite (ClO2-), a regulated inorganic DBP, BWD incorporated ferrous salt into their coagulation regime to quench chlorite to chloride. In this study, two ferrous salts - ferrous chloride (FC) and ferrous sulfate (FS) - were compared as secondary coagulants in combination with alum, the primary coagulant. Ferrous salts were dosed stoichiometrically to reduce chlorite and alum was dosed at percentages (0-100%) relative to a typical alum dose at the BWD, 30 mg/L as alum. Settled water turbidity, dissolved organic carbon (DOC), chloride to sulfate mass ratio (CSMR), solids settleability, and water filterability were assessed in laboratory scale bench tests and pilot plant studies as a function of percent alum dose reduction (ADR). Results from bench scale jar tests and pilot plant study showed that settled water turbidity and DOC were not compromised up to ~40% ADR (18 mg/L as alum) and were indifferent to the type of ferrous salt added. As expected, CSMR, a corrosion surrogate, increased with increasing ADR (or decreasing sulfate addition) and was higher for the FC-treated waters compared to the FS-treated waters. However, CSMR remained below the suggested threshold of 0.6 for ADR values up to 60%, indicating both ferrous salts were viable options for chlorite quenching at BWD. Notably, the headloss rate during filtration in the pilot plant study was lower for the FS-treated waters at all values of ADR tested, and thus is the recommended secondary coagulant for the BWD. </p>","abstract_has_math":false,"creators":["Doyle, Jenny"],"institution":null,"degree_name":"Master of Science in Civil Engineering (MSCE)","degree_level":"Thesis","degree_discipline":null,"degree_department":null,"school":null,"contributors":["Pifer, Ashley","Zhang, Wen"],"advisors":["Fairey, Julian L."],"committee_chairs":[],"committee_members":[],"year":2014,"date_issued":"2014-05-01T07:00:00Z","date_published":"2014-05-01T07:00:00Z","updated_at":"2026-07-24T00:59:32Z","subjects":["Chlorite Reduction","Coagulant","Drinking Water","Ferrous","Civil Engineering","Environmental Engineering"],"languages":[],"rights":[],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"https://scholarworks.uark.edu/etd/2279","outbound_label":"Repository record","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Pifer, Ashley","Zhang, Wen"]},{"key":"dc:contributor.advisor","label":"Advisor","values":["Fairey, Julian L."]},{"key":"dc:creator","label":"Author","values":["Doyle, Jenny"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2014"]},{"key":"dc:date.available","label":"Dc Date Available","values":["2024-02-06T08:00:00Z"]},{"key":"thesis:degree_level","label":"Degree Level","values":["Thesis"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Master of Science in Civil Engineering (MSCE)"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Chlorite Reduction","Coagulant","Drinking Water","Ferrous","Civil Engineering","Environmental Engineering"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["https://scholarworks.uark.edu/etd/2279"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["In November 2012, the Beaver Water District (BWD) switched primary oxidants from free chlorine to chlorine dioxide (ClO2) to curb formation of trihalomethanes, a regulated group of organic disinfection byproducts (DBPs). Because ClO2 is reduced to chlorite (ClO2-), a regulated inorganic DBP, BWD incorporated ferrous salt into their coagulation regime to quench chlorite to chloride. In this study, two ferrous salts - ferrous chloride (FC) and ferrous sulfate (FS) - were compared as secondary coagulants in combination with alum, the primary coagulant. Ferrous salts were dosed stoichiometrically to reduce chlorite and alum was dosed at percentages (0-100%) relative to a typical alum dose at the BWD, 30 mg/L as alum. Settled water turbidity, dissolved organic carbon (DOC), chloride to sulfate mass ratio (CSMR), solids settleability, and water filterability were assessed in laboratory scale bench tests and pilot plant studies as a function of percent alum dose reduction (ADR). Results from bench scale jar tests and pilot plant study showed that settled water turbidity and DOC were not compromised up to ~40% ADR (18 mg/L as alum) and were indifferent to the type of ferrous salt added. As expected, CSMR, a corrosion surrogate, increased with increasing ADR (or decreasing sulfate addition) and was higher for the FC-treated waters compared to the FS-treated waters. However, CSMR remained below the suggested threshold of 0.6 for ADR values up to 60%, indicating both ferrous salts were viable options for chlorite quenching at BWD. Notably, the headloss rate during filtration in the pilot plant study was lower for the FS-treated waters at all values of ADR tested, and thus is the recommended secondary coagulant for the BWD.
"]},{"key":"dc:title","label":"Title","values":["Comparing Ferrous Chloride and Ferrous Sulfate as Secondary Coagulants at the Beaver Water District Drinking Water Treatment Plant"]}]}],"canonical_facts":{"dc:contributor":["Pifer, Ashley","Zhang, Wen"],"dc:contributor.advisor":["Fairey, Julian L."],"dc:creator":["Doyle, Jenny"],"dc:date":["2014"],"dc:date.available":["2024-02-06T08:00:00Z"],"dc:description.abstract":["In November 2012, the Beaver Water District (BWD) switched primary oxidants from free chlorine to chlorine dioxide (ClO2) to curb formation of trihalomethanes, a regulated group of organic disinfection byproducts (DBPs). Because ClO2 is reduced to chlorite (ClO2-), a regulated inorganic DBP, BWD incorporated ferrous salt into their coagulation regime to quench chlorite to chloride. In this study, two ferrous salts - ferrous chloride (FC) and ferrous sulfate (FS) - were compared as secondary coagulants in combination with alum, the primary coagulant. Ferrous salts were dosed stoichiometrically to reduce chlorite and alum was dosed at percentages (0-100%) relative to a typical alum dose at the BWD, 30 mg/L as alum. Settled water turbidity, dissolved organic carbon (DOC), chloride to sulfate mass ratio (CSMR), solids settleability, and water filterability were assessed in laboratory scale bench tests and pilot plant studies as a function of percent alum dose reduction (ADR). Results from bench scale jar tests and pilot plant study showed that settled water turbidity and DOC were not compromised up to ~40% ADR (18 mg/L as alum) and were indifferent to the type of ferrous salt added. As expected, CSMR, a corrosion surrogate, increased with increasing ADR (or decreasing sulfate addition) and was higher for the FC-treated waters compared to the FS-treated waters. However, CSMR remained below the suggested threshold of 0.6 for ADR values up to 60%, indicating both ferrous salts were viable options for chlorite quenching at BWD. Notably, the headloss rate during filtration in the pilot plant study was lower for the FS-treated waters at all values of ADR tested, and thus is the recommended secondary coagulant for the BWD.
"],"dc:identifier":["https://scholarworks.uark.edu/etd/2279"],"dc:subject":["Chlorite Reduction","Coagulant","Drinking Water","Ferrous","Civil Engineering","Environmental Engineering"],"dc:title":["Comparing Ferrous Chloride and Ferrous Sulfate as Secondary Coagulants at the Beaver Water District Drinking Water Treatment Plant"],"thesis:degree_level":["Thesis"],"thesis:degree_name":["Master of Science in Civil Engineering (MSCE)"]},"updated_at":"2026-07-24T00:59:32Z"}