In many cases, aesthetic problems will be prevented by optimizing conventional treatment
processes such as coagulation, sedimentation and chlorination. However, if
specifi c 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 sulfi de, 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 fi ltration. Techniques for
removing hydrogen sulfi de include aeration, granular activated carbon, fi ltration and
oxidation. Ammonia can be removed by biological nitrifi cation. Precipitation softening
or cation exchange can reduce hardness. Other taste- and odour-causing inorganic
chemicals (e.g. chloride and sulfate) are generally not amenable to treatment