ALUMINIUM in raw water at a plant serving 50,000 people in Londonderry twice last year exceeded a level some scientists believe sufficient to induce Alzheimer's disease if consumed regularly.
According to Northern Ireland Water's （NIW） annual report for 2009 treatment difficulties at Carmoney Wastewater Treatment Works （WTW） over August 17-19, 2009 and again over August 31-September 10, 2009, led to aluminium exceedences in raw water thatwas bound for the taps and teapots of 50,000 people in Londonderry.
A spokesperson for NIW told the Sentinel the exceedences were caused by heavy rainfall, affected raw water at the WTW only, and that the aluminium tinged water did not end up in any customer's taps.
Equally, the spokesperson argued that the levels of aluminium in the WTWs were not of a sufficient level to cause concern on health grounds.
Scientists have suggested a link between aluminium in drinking water and Alzheimer's disease - a study by French experts published last year found a daily aluminium intake of 0.1mg/litre was associated with greater cognitive decline.
The World Health Organisations says: "On the whole, the positive relationship between aluminium in drinking-water and Alzheimer's Disease, which was demonstrated in several epidemiological studies, cannot be totally dismissed.
"However, strong reservations about inferring a causal relationship are warranted in view of the failure of these studies to account for demonstrated confounding factors and for total aluminium intake from all sources.
"Taken together, the relative risks for AD from exposure to aluminium in drinking-water above 100mg/litre, as determined in these studies, are low （less than 2.0）。"
A spokesperson for NIW explained: "The regulatory limit （PCV） for aluminium is 200ug/l. The Health Notification Value （HNV） for aluminium is 500ug/l.
"The HNV is the value at which NI Water must inform the Public Health Agency that there has been a Water Quality exceedence. NI Water was not therefore required to notify to the Public Health Agency.
"The exceedences of the regulatory limit at the water treatment works were a result of extreme heavy rainfall which caused the deterioration of the raw water quality at the works.
"All samples taken at customers' properties during this period were all found to be below the regulatory limit of 200ug/l. This incident was dealt with through the regulatory reporting requirements and to the satisfaction of the Drinking Water Inspectorate （DWI）。
"NI Water carried out remedial work to restore the water quality at the Carmoney Water treatment works. In addition, routine and enhanced monitoring of water quality throughout the distribution system was carried out by sampling and reviewing aluminium levels that occurred during this period.
"NI Water is also investing ?3.5 million in a major upgrade of the Carmoney Water treatment works which is due for completion in spring 2011. Customers will benefit from increased security of supply and drinking water quality."
Five further incidents were also reported in the North West in 2009 where NIW blotted its annual report card.
During February 23-25, 2009, a potential contamination incident caused by damage to a water mains in Carnhill resulted in NIW issuing a "Do Not Use Notice" to 350 properties.
On April 22, 2009, treatment difficulties at the Ballinrees WTWs - serving 127,000 people in Limavady, Coleraine and Ballymoney - resulted in aluminium above the "Prescribed Concentrations or Values."
During June and July 2009 there were problems removing the powerful pesticide MCPA from the raw water source at the Derg WTWs which treats drinking water for 42,500 people in Strabane.
And last winter 30 properties in Claudy suffered taste and odour failures in their drinking water supply following operational work over December 8-10 in the Cumber road area, and homes all over the North West were affected by frozen pipes and burst mains due to freezing weather between December 26, 2009, and January 21, 2010.
In the annual report Chief Executive Laurence McKenzie wrote: "NI Water aims to provide high quality drinking water, in a cost effective manner, to meet the requirements of existing and future customers.
"By doing this we contribute to the health and well being of the community, the needs of commerce and the protection of the environment.
"Drinking water is regularly monitored and tested for quality. This report summarises NI Water's results from 1 January 2009 to 31
December 2009 to meet the requirements of the Regulations under which we operate.
"During this reporting period, 99.74 per cent of all tests carried out on samples taken from customers' taps and authorised supply
points, complied with the regulatory standards assessed using the Mean Zonal Compliance （MZC） method of assessment （MZC is the method required by the drinking water regulator in Northern Ireland）。
"This demonstrates a continued improvement in overall drinking water quality compared to previous years' results. （2008 MZC-99.49%）
"As part of NI Water's reporting requirements, this report also incorporates for the first time data to meet the requirements of the Water Supply （Water Fittings） Regulations （NI） 2009."
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