Water gets clean bill of health — mostly
Some water supplies fail to meet criteria
Horowhenua came through the latest Ministry of Health drinking water quality report with almost flying colours . . . but not quite. An issue was identified at the Tokomaru water plant, where one of the four criteria used in the report to evaluate the quality of drinking water was not met in the past year.
The water supply in Tokomaru is from surface water and is treated with filtration and UV, and is chlorinated.
The failed standard is the chemical one “as a disinfection byproduct produced as part of the disinfection process exceeded MAV (maximum acceptable values in mg/litre for inorganic determinands of health significance in drinking water) and council took inadequate action to address the issue”, the report says.
In Foxton, Foxton Beach, Levin, and Shannon, all standards were met.
The four standards that need to be met are: compliance with the Health Act, as well as specific bacterial, protozoal and chemical standards.
All Palmerston North drinking water supplies passed with flying colours, though a few private supplies had problems.
In Longburn, Brandlines Ltd, using groundwater without disinfection, and Longburn Adventist College, using groundwater that is treated with filtration and UV, failed three of the four standards.
The report says it wasn’t known whether either Brandlines or Adventist College had complied because no information was available. Only the chemical standard was met in both cases.
According to the report, at Longburn Adventist College, E. coli was detected in 18.5 per cent of monitoring samples and no attempt was made on compliance, the reason the college also failed the protozoal standard.
At Ohakea, three of the four standards failed because sampling was inadequate and it could not demonstrate compliance.
Ohakea failed to meet monitoring requirements. It uses groundwater, which is treated with coagulation, filtration and UV, and is chlorinated.
At Linton Army camp only the protozoal standard failed because the infrastructure is deemed inadequate. Its supply is from groundwater, which is treated with filtration, is chlorinated and fluoridated.
In the Manawatu¯ district only the Halcombe-Stanway water supply had an issue with the protozoal standard because the infrastructure was inadequate. Water used is surface water, which is treated with filtration and is chlorinated. Supplies at Feilding, Himatangi Beach, Rongotea, Sanson and Waituna West all passed.
Massey University passed all four standards with flying colours.
The report states Covid-19 has severely interrupted the review, making checks on data provided difficult.
“Failing to comply with the protozoal standards does not necessarily mean that pathogenic protozoa (Giardia spp. and Cryptosporidium spp.) were present in the drinking water. Complying with the protozoal standards is based on the likelihood that the treatment processes in operation will adequately protect the community if pathogenic protozoa are present in the source water.
“To comply with the protozoal standards, the drinking water supplier must meet the following two requirements:
They must either use groundwater complying with the secure bore water criteria of the standards or have treatment processes in operation that can remove or inactivate an adequate percentage of any protozoa present in the source water.
They must be able to show that they are operating the treatment processes sufficiently well to meet the target percentage of protozoal removal or inactivation.
“Failure to comply with the protozoal standards is therefore due to a lack of infrastructure or failure to meet the compliance criteria.
“The majority of protozoa are freshwater organisms that have no public health significance. However, two groups of protozoa can cause adverse health reactions:
Enteric protozoa that live in the gut of humans and other animals, such as some species of Cryptosporidium and Giardia
Free-living organisms that are opportunistic pathogens in humans and may cause serious illness, such as Naegleria fowlerii and some species of Acanthamoeba.
“Cryptosporidium has been identified as one of the most important waterborne human pathogens in developed countries and is responsible for many outbreaks.
“Even very low numbers of protozoa of either of the groups identified above can cause illness in people. Therefore the presence of any of these organisms in the drinking water supply can put public health at risk,” the report says.