Scottish Government

3.6 Summary of Complaints About Drinking Water Quality

Scottish Water is required to record details of any complaints and enquiries it receives from consumers concerning drinking water quality. These complaints may be received by telephone, letter or email. Table 3.6a and Figure 3.6b show the number and type of complaints recorded by Scottish Water in 2006. The meaning of the categories is described below:

Appearance of the Water

Discoloured Water

Water with a discernable taint or colour caused by suspended or dissolved matter. Two of the most common causes are a yellow taint caused by dissolved organic matter arising from peat in upland sources and more general orange, brown or black discolouration caused by suspended particles of iron (orange/brown) and manganese (black). Iron discolouration may occur through natural iron present in the raw water passing through inadequate treatment or from corrosion of cast iron distribution mains. Manganese is present in some raw waters and may not be removed if treatment is inadequate

Aerated (Milky or Cloudy) Water

Water which has a milky appearance caused by tiny bubbles of entrained air which dissolve in the water under pressure but come out of solution at the consumer's tap. A number of causes are possible including burst mains, malfunctioning pumps and throttled consumer stop taps. If air is the cause of the milky water, the cloudy appearance will clear in a glass of water from the bottom up.

Stained Washing

Brown or black staining of clothes can occur on clothes inadvertently washed in discoloured water. If clothes are kept damp, the staining may often be removed by gently acidifying with a suitable substance such as citric acid. However, staining may also arise from a fault with the washing machine.

Particles in water

Visible particulate matter in water which is otherwise not discoloured. This can be caused by corrosion of iron mains or deposits of sand, grit or other material which may be present in the main and is re-suspended following a flow disturbance.

Organisms in water

Complaints of insects or other animals in the water supply. Most complaints arise where an insect has crawled up a tap or is present in the sink. Very occasionally water systems can contain animals which may arise from the raw water, treatment works or within the mains themselves. This is extremely rare, however organisms such as midge larvae ( Chironomid) or water shrimp ( Aesellus) have occasionally been found in domestic supplies.

Taste or Smell of the Water

Chlorine or Phenolic

Excess residual chlorine or the reaction of chlorine with phenolic compounds which may be present in household plumbing can result in taste and smells. Chlorine taste and smells should dissipate if the water is left to stand in the fridge for a few hours. It will also not be present after boiling. Phenolic tastes can be more persistent. Common descriptions used by customers include TCP, medicinal, swimming pool, bitter, and chemical. Common sources of phenol include washing machine hoses, tap washers and kettles. British Standard approved plumbing products which do not contain phenol should be used in all plumbing installations.

Metallic

Metallic tastes may arise from an excess of iron, aluminium or other metal dissolved in the water, although normally there will also be visible discolouration. Occasionally phenolic complaints may be described as metallic.

Musty or Earthy

Musty or Earthy tastes can arise due to naturally occurring compounds present in raw waters that have not been removed by the treatment process. Geosmin is one such compound commonly associated with earthy/musty tastes. Complaints are more common in the summer months when biological activity is highest - algal blooms in raw water sources are common causes of widespread musty tastes.

Fig 3.6a Complaints About Drinking Water Quality Received by Scottish Water in 2006 by Category

Table 3.6b Complaints About Drinking Water Quality Received by Scottish Water with Comparison Against 2005

The chart and table show that the appearance of drinking water generates by far the largest proportion of consumer complaints. This is mainly due to complaints relating to discoloured water which accounted for almost six complaints out of every ten in 2006. In the North West it is likely that many of these complaints result from highly coloured peaty waters where existing treatment is inadequate to fully remove the colour-causing compounds. In other areas the deteriorating condition of old cast iron mains, leading to an accumulation of iron sediment, is most likely to be the primary cause of dissatisfaction. Although the complaint rate for discolouration fell slightly in 2006, there remains much to be done to reduce the number of consumers who have concerns about the appearance of their water supply. Scottish Water is addressing the discolouration problem by further investment in improved treatment and the rehabilitation of ageing water mains during the current investment period.

Areas which experienced a particularly high rate of complaints about discolouration include Camphill Supply Zone, serving the area around Largs in North Ayrshire (383 complaints per 10,000 consumers) and Penwhirn Supply Zone in the Newton Stewart area of Dumfries and Galloway (211 per 10,000). Both of these areas are currently the subject of Undertakings and Authorised Departures granted by Scottish Ministers to ensure that Scottish Water carries out the work necessary to improve water quality in these areas.

Complaints about the taste of chlorine accounted for 13% of the total in 2006. It is essential that supplies receive adequate disinfection in order to protect public health, however the DWQR expects Scottish Water to monitor the use of chlorine carefully and to use no more than is necessary to maintain microbiological safety. This includes proactively reviewing chlorine concentrations in areas where improvements to water treatment and the distribution system mean that chlorine persists at higher concentrations through the supply. Areas which experienced a particularly high chlorine complaint rate include the parts of Edinburgh and West Lothian served by Marchbank WTW (around 60 complaints per 10,000 consumers - partly due to an incident in the Summer of 2006), Dodburn Supply Zone around Hawick (28 per 10,000) and Forehill Supply Zone serving Peterhead in Aberdeenshire (28 per 10,000).

One of the main causes of taste complaints is large fluctuations in the chlorine residual leaving a water treatment works due to deficiencies in the control of the chlorine dosing. The DWQR uses a disinfection index to assess control of chlorine at treatment works, and has set Scottish Water targets linked to the investment process to ensure improvements are made at the sites in most need of improved control. A higher disinfection index indicates less consistent dosing of chlorine. Scottish Water has been set the target of ensuring all treatment works have a disinfection index below 100 by 2010. The number of treatment works falling within each disinfection index category over the last three years is shown in Fig. 3.6c. It can be seen that the number of treatment works in the poorest performing category (greater than 100) has significantly reduced over the three years. Information at a regional level may be found in Section 4. It is anticipated that improvements to chlorine monitoring and dosing instrumentation as well as robust arrangements for providing adequate contact time at sites where this is not currently in place will bring about further reductions in disinfection indices.

Figure 3.6c No. of Treatment Works in Disinfection Index Category by Year