Updated: Jan 17, 2021
Victor Luca, 13-Jan-21.
The township of Whakatāne with a current population of ca. 22,000 and Ohope source their drinking water from the Whakatāne river about 8 Km upstream from the river entrance.
In chemical engineering terms the plant is a pretty stock-standard affair.
The simplified multi-step flowsheet incorporates a number of filtration, coagulation and disinfection stages using a range of chemicals. Chemicals used included the following:
Alum is a double salt of aluminum sulfate, XAl(SO4)2·12H2O, where X is an alkali metal cation such as Na+ or K+.
Poly stands for polyaluminum, a popular coagulant used in the water treatment industry. The general formula for this compound is (Aln(OH)mCl(3n-m))x.
Alum reacts in water to produce aluminum hydroxide and as a by-product sulfuric acid. The metal hydroxide precipitates out of solution and entraps neutralized charged dirt particles (turbidity), as well as coagulating soluble color and organics by adsorption.
PAC stands for Activated Carbon.
Lime is calcium carbonate (CaCO3).
Fluoride is added to our drinking water in the interests of preventing tooth decay.
In 2026 the resource consent for this plant is up for renewal. What was once successful may not cut it going forward.