What’s happening behind the scenes when drinking water gets to our taps or our wastewater is discharged – and how might climate change get in the way?
The Science Media Centre asked experts to provide an overview and their thoughts on the current state of different water infrastructures in Aotearoa New Zealand. Experts commented on:
Professor Michael Baker, Professor of Public Health, University of Otago, Wellington, comments:
“Clean drinking water and effective sewage disposal (often described as “sanitation”) is fundamental to public health. So much so that we take them for granted. That is why the Havelock North campylobacter outbreak in August 2016 was such a shock. It was caused by surface water contaminated with sheep faeces entering the untreated drinking water system, resulting in an estimated 8320 infections, 58 hospitalisations, and at least four deaths, making it the largest campylobacter outbreak ever reported.
“The subsequent Havelock North Drinking Water Inquiry recommended a major overhaul of drinking water supply in New Zealand, which was subsequently broadened into the Three Waters Reform Programme.
“The first component of this reform has already occurred with the setting up of a new regulator, Taumata Arowai. The next step is currently underway with legislative change to shift responsibility for drinking, waste, and stormwater from local authorities to four new publicly-owned regional entities. This stage is currently at select committee for consultation.
“There are multiple public health and environmental problems and threats that these reforms need to address, in addition to reducing the risk of a repeat Havelock North outbreak:
- Regular microbial contamination of drinking water systems, particularly following floods which are becoming more common with climate disruption, resulting in frequent breaches of the drinking water standards and boil water notices.
- Concerns about intensified farming and increasing microbial contamination of source water, including with protozoa (cryptosporidia and giardia) which are harder to remove from drinking water with conventional methods.
- Increasing levels of nitrate contamination of drinking water, particularly in intensively farmed areas, from application of nitrate fertiliser and urine from cattle.
- Problems with monitoring of fluoride levels, as seen in Wellington, and potentially an issue in other supply systems.
- Concerns over lead contamination of drinking water, as seen in Dunedin, and potentially in other water distribution zones.
- Hugh inequalities in access to clean drinking water with smaller rural and more deprived communities having poorer access.
- Wider environmental issues, including sedimentation, and nutrient, bacterial, and heavy metal contamination of freshwater and coastal areas which causes direct ecosystem damage, and potential human health effects.
“Whatever new regulatory and deliver system we adopt, it will be important that these public health and environmental needs are kept as a central focus. The Havelock North Drinking Water Inquiry emphasises the need for a highly systematic approach to improving the quality and safety of drinking water. A similar need applies to wastewater and stormwater management.
“The first part of the water reforms has already been operating for a year. Taumata Arowai became New Zealand’s dedicated regulator of drinking water when the Water Services Act came into effect on 15 November 2021. It published a Statement of Intent for 2022 – 2026. Key outputs we can expect from this agency are a comprehensive monitoring system of drinking water quality, and drinking water standards that incorporate the best scientific evidence we have about the health effects of contaminants such as nitrates. There will need to be a strong focus on addressing major upstream risks to the safety of drinking water supplies, such as increased intensification of pastoral farming and climate disruption.”
No conflict of interest.
Dr Lokesh P. Padhye, Senior Lecturer, Civil and Environmental Engineering, The University of Auckland, comments:
“When it comes to three waters infrastructure, New Zealand is far behind the developed world. As evident from the recent detections of pathogens and trace level chemicals in our source waters, the pollutants will find a way to our glass of drinking water if we do not manage wastewater and stormwater runoffs well. Most wastewater treatment plants in New Zealand are non-compliant, meaning many exceed one of the discharge criteria related to effluent parameters. With a high number of wastewater treatment plants discharging their effluent in rivers and polluted runoffs from irrigated lands ending up in our waterways, it is not surprising that New Zealand’s freshwater rivers are among the most polluted in the developed world.
“The major challenges for wastewater treatment plants in New Zealand relate to resources, as most of the treatment plants implement cheap treatment of ponds and lagoons and thus produce inferior quality effluent compared to advanced treatments. Considering the sparse population spread over many remote regions of the country, centralised wastewater treatment won’t work for everyone. However, having efficient community-owned treatment plants and making those compliant by providing enough resources and imposing strict penalties for non-compliance will be a good start towards improving our environment. There is an urgent need to manage the water cycle holistically and start prioritising the treatment of wastewater and stormwater runoff if we want safe drinking water and a clean environment.”
No conflict of interest.
Dr Ricardo Bello Mendoza, Senior Lecturer and Co-Director Humanitarian Engineering, Department of Civil and Natural Resources Engineering, University of Canterbury, comments:
“I see that New Zealand is getting behind other developed countries in implementing new technologies for wastewater treatment and, in particular, recovering resources from waste streams. Many wastewater treatment plants use low-rate technologies (i.e., they are slow) that require significant energy inputs, generate large volumes of biosolids and emissions, and produce treated effluents of less than optimal quality (e.g., with substantial levels of nutrients).
“In my view, one of the most critical challenges in addressing the problem is the high level of investment required. For starters, we need to upgrade our aging sewer networks. For example, inflow and infiltrations from groundwater and stormwater often result in overflows at the wastewater treatment plans. This is ‘diluted’ wastewater discharged directly into the environment without treatment. Most of these overflows are unconsented. In terms of wastewater treatment, we need more sustainable technologies. That is to say, processes that use less energy, produce less waste sludge, and allow the recovery of resources such as nutrients (e.g., struvite), energy (e.g., methane), or metals. We need to move from seeing wastewater treatment as a necessary evil to seeing it as an opportunity for closing loops in a circular economy.
“Another critical challenge is that many of the New Zealand population is not connected to a wastewater network. These on-site treatment systems are mainly unmonitored and unregulated. I think that the New Zealand model of housing growth, characterised by suburban sprawling with low-density housing, makes the collection and treatment of wastewater even more expensive and challenging than in other places.”
No conflict of interest.
Dr Tom Logan, Lecturer, Civil Systems Engineering. University of Canterbury, comments:
“Climate change is increasing the risk to our infrastructure, and water infrastructure is not immune. We’re all very familiar with how increased severity of rainfall events are affecting our stormwater and leading to flooding, but there are other, less obvious risks. Key among these for many New Zealand towns and cities is groundwater rise (67% of our population live in coastal areas). Sea level rise causes groundwater rise as well as salt intrusion in some areas (that is, the groundwater becomes more salty). This causes several issues. The first is that increased groundwater and higher sea levels mean that stormwater systems are less effective, which means floods will be worse. Additionally, groundwater rise can damage our buried infrastructure; if it’s saline, these infrastructures will deteriorate faster and simply the rise and fall of the water level increases the pressure on the pipes, potentially leading to displacement.
“Adaptation planning and asset management must consider these factors. When deciding on the appropriate course of action for a community threatened by hazards, we need to take into account number of people at risk, threat to assets, and the cascading and compounding impacts that may arise as a result. To achieve this, local government or utility providers need to know the characteristics and condition of their assets. Unfortunately, this is not always well known or documented. National standards for asset information would simplify and streamline risk assessment and support adaptation planning. However, we also must seek integrated decision approaches rather than further siloing. Maintaining or improving an approach that integrates with other co-dependent and interdependent infrastructures is going to be an essential task as the reform of the three waters management proceeds.”
Conflict of interest statement: “I do research on risk, climate adaptation and resilience. I am the technical director of Urban Intelligence Ltd. that consults to councils and utility companies on resilience.”
Graham Elley, Principal Scientist – Environmental Monitoring, NIWA, comments:
“Irrigation currently accounts for about two-thirds of all consumptive water allocated in New Zealand and production from irrigated agriculture is projected to increase further.
“That’s why it’s important to encourage the development and uptake of better irrigation management tools, practices, and systems – these can help farmers better understand what water resources are available, the best time and methods to use water, and to consider what land use options are best suited to the resources they have.
“We recently completed a five-year project called Irrigation Insight. Working with a group of South Island dairy farmers, researchers, industry, and regulators, we investigated opportunities to encourage the optimal use of water for land-based production activities, and identified barriers that currently discourage optimal use of water.
“A focus of the research was investigating and demonstrating the benefits of using weather forecasts to help shape irrigation decisions.
The programme also involved asking some hard questions regarding land use suitability and dealing with water constraints, such as:
- What could you do with the land if you understood what water was available now and into the future?
- Would irrigation allow you to do more with the land? If yes, do you have the water resources to support irrigation, or would you need water storage?
- Once you understood how much water you were likely to have during each season of the year, could you identify different types of production, better suited to your land?
“We used feedback from our collaborators to develop tools which can help farmers review their irrigation decisions, as well as the impact of those decisions on their pasture growth, soil moisture management and drainage events.
“The principal outcomes of the research include: improving the ability of farmers to see the cause and effect of their irrigation decisions, and giving farmers the capability to make changes to their farm management using readily available data, as well as information derived from their own learning experiences.
“A lot of the work in this area is about how to make the most of the water that is available, employing ‘smart thinking’, and using high resolution weather forecasts to drive actions around water use.
“By applying technology, we can help farmers make economically sound decisions while also being environmentally responsible.”
No conflict of interest.