10.3 Treatment of taste, odour and

10.3 Treatment of taste, odour and appearance problems
In many cases, aesthetic problems will be prevented by optimizing conventional treatment
processes such as coagulation, sedimentation and chlorination. However, if
specific treatment is deemed necessary, aeration, granular or powdered activated carbon
and ozonation are generally effective techniques in removing organic chemicals
and some inorganic chemicals, such as hydrogen sulfide, that cause tastes and odours
(see Annex 5).
Tastes and odours caused by disinfectants are best controlled through careful
operation of the disinfection process and pretreatment to remove precursors.
Manganese can be removed by chlorination followed by filtration. Techniques for
removing hydrogen sulfide include aeration, granular activated carbon, filtration and
oxidation. Ammonia can be removed by biological nitrification. Precipitation softening
orcation exchange can reduce hardness. Other taste- and odour-causing inorganic
chemicals (e.g. chloride and sulfate) are generally not amenable to treatment
(see the supporting document Chemical safety of drinking-water; Annex 1).