Low pH Water
Allowable Scale 6-9 in SA
The pH of natural waters is the result of complex acid-base equilibria of various dissolved compounds, mainly the carbon dioxide-bicarbonate-carbonate equilibrium system, which is also affected by temperature. Conditions which favour production of hydrogen ions result in a lowering of pH, referred to as an acidification process. Alternatively, conditions which favour neutralisation of hydrogen ions result in an increase in pH, referred to as an alkalinization process.
The pH of water does not indicate the ability to neutralise additions of acids or bases without appreciable change. This characteristic, termed buffering capacity, is controlled by the amounts of acidity and alkalinity present.
The pH of a water does not have direct health consequences except at extremes. The adverse effects of pH result from the solubilisation of toxic heavy metals and the protonation or deprotonation of other ions. The pH of most raw water sources lies within the range of 6.5 – 8.5. The main significance of pH in domestic water supplies relates to its effects on
water treatment.
The main significance of pH in domestic water supplies relates to its effects on water treatment processes. The pH of water can be adjusted up or down by the addition of an alkali or an acid.
Commonly used alkaline reagents are sodium carbonate, sodium hydroxide and lime. Acidic reagents commonly used are carbon dioxide (a gas which forms carbonic acid in water), hydrochloric acid or sulphuric acid. The reagent is usually added in dilute form using a dosing pump controlled by a pH monitor.
The adjustment of pH in water will inevitably increase the salinity of the water by adding ions such as sodium, carbonate, hydroxyl, sulphate or chloride. Reagents should be chosen to minimise secondary effects. For certain purposes the pH of the water will need to be stabilised to within a chosen range by the addition of buffering reagents.
The handling of acids and alkalis is often hazardous requiring special precautions in the form of protective clothing and in materials used in the manufacture of the dosing equipment.
Changes in pH affect the degree of dissociation of weak acids and bases. This effect is of special importance because the toxicity of many compounds is affected by their degree of dissociation.
Corrosion in the water supply system is a major source of metal contamination in drinking water. Metals that have the potential for causing such contamination are lead, copper and zinc. Lead is subject to corrosion at a pH higher than 12.
Corrosion of cadmium is only significant below pH 6. Other metals which are frequently used in household plumbing and that may be affected by pH are copper and zinc.
Neutralisation is a realatively simple solution and we offer many options