Options for Adding Alkalinity
Sodium Bicarbonate, a.k.a. Baking Soda (NaHCO3) – Sodium bicarbonate is most often recommended for alkalinity addition because it is not a strong base and it has a pH of 8.3. It is beneficial to alkalinity addition by providing the bicarbonate species at a pH near neutrality.
Sodium Carbonate, a.k.a. Soda Ash (Na2CO3) – Soda ash is safer to handle than other alkalis and tends to maintain stable prices over time, hence more and more treatment plants are choosing soda ash for their alkalinity needs. While soda ash is less expensive than sodium bicarbonate, it is generally less effective than sodium bicarbonate and sodium hydroxide. Soda ash is a moderately fastacting agent, but it generates carbon dioxide, which can lead to foaming problems.
Calcium Oxide, a.k.a. Lime (Ca(OH)2) – Lime is available in various forms and is relatively inexpensive. Lime compounds dissolve slowly and require longer contact times than the other chemical options. The use of lime causes more sludge production due to calcium sulfate precipitation. This results in maintenance problems within the basin, especially with pH, DO, and ORP probes.