1. Treatment – pH Correction / Conditioning
Matt Bower
DWQR Risk Assessment Training
2018

2. Overview Many Scottish waters have low pH & alkalinity
This makes water corrosive to metals, concrete
If lead pipes – will make problem worse
Need to increase pH / alkalinity artificially
Simple filters available
Consider pH / alkalinity when investigating metal fails

3. Overview

4. Overview Lead Nickel Copper Zinc Iron
Metal
Possible Sources
Effects
Lead
Lead piping and tanks; solder; some brass fittings; stabiliser in some PVC pipes
Developmental issues in children; raised blood pressure in older people.
Nickel
Plumbing fittings made from metal alloys, stainless steel and plated products
Chronic exposure may cause heart and liver damage. Dermatitis in those sensitised.
Copper
Piping, brass fittings and fixtures.
Taste, discolouration of fittings and hair, possibly gastro-intestinal effects. Toxic to people with Wilson’s disease.
Zinc
Galvanised piping and tanks, brass fittings
Taste and potential gastro-intestinal effects at high concentrations.
Iron
Iron or steel piping or tanks
Primarily aesthetic – sediment and brown discolouration. Substrate for accumulating contaminants from upstream sources.

5. Usage on small water supplies
Neutralising Filters
Often upflow
Media:
Limestone
Magnesium Oxide
Dolomite
Need to get reaction time right!
Media will gradually be used up – replace!
Alkali dosing
Sodium hydroxide
COSHH issues
Does not raise alkalinity only pH – water could be >pH6.5 and still corrosive

6. Key Points to Watch For Evidence of excessive corrosion
Is water clean enough for neutralising filter?
Is contact time / media appropriate? Refer to mfrs’ spec.
Is there a maintenance plan (topping up)?
Is location of pH correction relative to disinfection appropriate?
Suitable disinfection process needed downstream

7. Questions
TPH1
Is there a risk of water supplied being of incorrect pH?
Many natural waters in the North and West of the UK are naturally of low pH. Consequently, many private water supplies require pH correction to ensure that the water is not corrosive to metal plumbing fittings. Care needs to be taken to ensure that any pH correction process is tightly controlled, as over- or under-correction can occur. 5
TPH2
Is there a risk or evidence of corrosion of fittings?
This may be evident through staining of sanitary ware (often green if copper is present) and by an increased rate of leakage.
TPH3
Is there a risk of any installed pH correction failing or being inadequate?
Any pH correction treatment should be designed to deal with the quality of the incoming water at all operating flow rates. Although pH itself is usually fairly consistent, rapidly changing flows can be an issue and pH correcting filters can block if incoming water is not of the correct quality. 4
TPH4
Is the plant inadequately maintained according to the design specification?
A pH correction plant will only perform effectively if it is correctly designed and operated in accordance with the initial specification. These should be documented to ensure requirements are clear. On-going maintenance will be required to ensure performance continues to be optimal.
TPH5
Is there a risk of inadequate pH correction due to the lack of a programme in place to monitor and replace media on exhaustion?
Many pH correction processes rely on contact with an alkaline media that is gradually used up. It will need periodic topping up with fresh media, however, this may significantly raise the performance of the filter to the point that over-correction is possible. Where only a proportion of the flow is treated, the blend may need to be adjusted to compensate. Regular monitoring of pH is essential.
TPH6
Is precipitate build up an issue (is it monitored / controlled)?
Raising the pH of the water may cause certain dissolved minerals (especially iron and manganese) to precipitate out, which can lead to the gradual clogging of the filter. If this is an issue, measures may be needed to periodically remove deposits from the filter.