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An Introduction to Drinking Water Contaminants, Treatment and Management

1 Introduction

2 Roles and Responsibilities in the Production of Drinking Water

3 Water Supply Management – Information Sources

4 Origins of Contaminants in Drinking Water Sources

5 Water Treatment

Appendix 1: Activities and the Contaminants That May Contribute to Source Waters

Appendix 2: Treatment Processes and Their Efficacies

2 Roles and Responsibilities in the Production of Drinking Water

2.1 Introduction

Several organisations and groups play a part in the production and management of drinking water. These are:

• water suppliers, who produce and supply drinking water for their consumers

• health protection officers and drinking water assessors working within public health units, who have responsibility for checking whether water suppliers are meeting the requirements of regulations and for providing advice

• the Ministry of Health, which develops regulations, ‘tools’ to encourage the good management of water supplies, support material to assist water suppliers in managing their supplies, and distributes support funding when it is available.

2.2 Drinking water suppliers

Most of New Zealand’s population is supplied with water by their local authority water suppliers (city or district councils). In Auckland and Wellington, residents receive their water from the local authority’s retailers who in turn receive their water from bulk water suppliers. The bulk water supplier in Auckland is the quasi-public-owned company, Watercare, and in Wellington it is the regional council. In addition to these suppliers, there are supplies owned and operated by:

• government departments, such as Defence (military bases), Justice (prisons), Conservation (national parks)

• schools

• large industries, which may provide water to a substantial number of workers

• camping grounds

• private individuals or groups of individuals, including marae supplies.

Water supplies run by local authorities will have an engineer or manager who has overall responsibility for the operation of the water supply. Treatment plant operators run treatment plants (see section 3.2 for more discussion on treatment plant operators).

The water supplier is responsible for providing safe drinking water to their consumers.¹

2.3 Public health units and drinking water assessors

The Ministry of Health and the district health boards have responsibilities for public health,² which include them undertaking activities to protect health and prevent population-wide disease. Public health units, which operate within district health boards, carry out these activities. These include some activities related to drinking water supplies. If water supplies become contaminated, they can cause widespread illness, and for this reason the Ministry of Health and public health units are responsible for overseeing the good management of water supplies.

Twelve public health units provide core public health services³ across the country; some cover more than one district health board. They deliver both health protection and health promotion activities.⁴

As noted in section 2.1, two types of staff in public health units may have responsibility for public health aspects of water supplies: health protection officers and drinking water assessors.⁵ Health protection officers have post-graduate training in public health and may have responsibility for water supplies only, or they may have broader responsibilities that require them to work in other health protection areas or health promotion.

Drinking water assessors have received additional training to increase their expertise in water supplies, water treatment and the regulations associated with these areas. The key responsibilities of drinking water assessors are:

• assessing the compliance of water supplies with the Drinking-water Standards for New Zealand (DWSNZ)

• undertaking the public health grading of water supplies (see section 3.6)

• assessing the adequacy of public health risk management plans and their implementation (see section 3.5).

2.4 Ministry of Health

The Ministry of Health develops regulations and legislation designed to ensure that New Zealand’s drinking waters are safe. To support regulatory and legislative initiatives, it has developed a suite of ‘tools’. These gather information about the way in which water supplies are being managed and also aim to help water suppliers provide a safe product by better managing their supplies. Several of these tools are introduced in this document. The ministry is also responsible for distributing funding the government has allocated to assist water suppliers in improving their supplies. The DWAP (Drinking-water Assistance Programme) has been established for this purpose. There are two components to this programme: the TAP (Technical Assistance Programme) and CAP (Capital Assistance Programme). The TAP aims to help water suppliers provide safe water to their consumers using their existing resources. Financial assistance from the CAP may be sought by a water supplier if they are unable to adequately address the public health risks to their supply, even after the improvements made with the help of the TAP.

2.4.1 Health (Drinking Water) Amendment Act 2007

The Ministry of Health produces Drinking-water Standards for New Zealand. The purpose of these standards is to protect public health by explaining how to assess the quality and safety of drinking water. They do this by (i) defining maximum acceptable concentrations of contaminants that can be present in drinking water and (ii) specifying compliance criteria to be used to assess the quality of drinking water.⁶

Until recently, compliance with the DWSNZ was voluntary. New health legislation passed in October 2007 changes this situation. The Health (Drinking Water) Amendment Act 2007 requires drinking water suppliers to take all practicable steps to ensure they provide an adequate supply of drinking water that complies with the DWSNZ.

Other key elements of the Act include:

• requiring drinking water suppliers to introduce and implement public health risk management plans

• ensuring drinking water suppliers take reasonable steps to contribute to protecting sources from which they obtain drinking water from contamination

• requiring officers appointed by the Director-General of Health to act as assessors to determine compliance with the Act

• requiring record keeping and publication of information about compliance

• providing for the appropriate management of drinking water emergencies

• improving enforcement by providing an escalating series of penalties for non-compliance.

Further information about the Act can be found on the Ministry of Health’s website: www.moh.govt.nz/moh.nsf/indexmh/drinking-water-proposed-legislation.

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