Premium
Enhanced Softening: Effects of Lime Dose and Chemical Additions
Author(s) -
Roalson Shay Ralls,
Kweon Jihyang,
Lawler Desmond F.,
Speitel Gerald E.
Publication year - 2003
Publication title -
journal ‐ american water works association
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.466
H-Index - 74
eISSN - 1551-8833
pISSN - 0003-150X
DOI - 10.1002/j.1551-8833.2003.tb10496.x
Subject(s) - chemistry , magnesium , lime , adsorption , calcium carbonate , softening , dissolved organic carbon , hydroxide , bromine , sulfate , calcium hydroxide , inorganic chemistry , nuclear chemistry , water treatment , hard water , environmental chemistry , organic chemistry , environmental engineering , metallurgy , materials science , engineering , composite material
Enhanced softening is the removal of natural organic matter (NOM) during precipitative softening, with an objective of reducing the formation of disinfection by‐products (DBPs). A moderately hard water source (Lake Austin, Austin, Texas) was softened using a wide range of lime dosages and various other chemical additions (magnesium, iron, phosphate, silica, and sulfate). The results for hardness ions (calcium and magnesium), NOM (indicated by dissolved organic carbon and ultraviolet absorbance at 254 nm), and 21 DBPs formed after chlorination at pH 9 are reported. Magnesium hydroxide, which precipitated above pH 11, was a better adsorbent for NOM than calcium carbonate (CaCO 3 ) (which precipitates at lower lime doses), but removal of NOM by CaCO 3 was by no means inconsequential. DBP formation generally followed the NOM trends but was complicated by the formation of bromine‐substituted DBPs because of the moderately high bromide concentration in this water.