View all publications

1. Natural systems

1.1 Ecosystems

An ecosystem is a community of interacting organisms and the physical environment in which they live. Humans and their buildings and settlements are part of this community, which can include birds, plants and insects, as well as inorganic matter (such as rock and metals) and natural forces (such as the flow of water, fire, or the chemistry of photosynthesis 1). All of these link together and interact as a complex web of life.

Western culture has a tradition of thinking of people as separate from natural systems and not part of their environment, although the natural world can still be highly valued. This separation is so easy on a day-to-day basis because of the ability people have to change and – to a limited extent – control their physical environment. It is also partly because our ordinary day-to-day systems and technologies tend to make it easy to feel separate from the natural processes. You can turn on a tap and get fresh water without having to think about the impact of taking the water from a nearby river or from underground. You can flush the toilet without having to think about where it goes.

This is changing as many people are finding that taking water or the impacts of wastewater are disrupting natural processes that sustain them in other ways. It is becoming more obvious that humans are embedded in their surrounding ecosystem, and that the built and engineered parts of our communities need to fit the processes of the wider natural ecosystem if the whole system is to survive in the long term.

Ecosystems overlap, and also exist at various levels – from a whole estuary to a small community in a single rock pool. But even if it is hard to see where one begins and ends, you can see quite clearly the functions of different systems. What makes each one a system are the links and dependencies of one part on another. These dependencies become obvious when one part begins to fail and stresses appear in other parts of the system.

It is worth thinking about the kind of ecosystem that exists in your area. Some broad types are coastal, estuary, river, lake, forest, agricultural and urban, and various combinations of these.

1.2 The water cycle, water catchments and the 'three waters'

Water plays an essential role in the natural nutrient cycle or 'waste conversion system'. It helps move wastes down into the soils and assists with the absorption of nutrients by plants. The natural water cycle is shown in Figure 1.1.

Figure 1.1 The water cycle

This figure portrays the water cycle. Rainfall hits the ground and either runs off to rivers, lakes, estuaries or sea, or infiltrates the surface. Deep infiltration also discharges to lakes, streams, estuaries and oceans. Evaporation from these bodies of water and transpiration from vegetation send water back up into the sky to continue the cycle.

Catchments

The water cycle shown above takes place everywhere. Where the water flows to, how fast, whether it goes underground and how quickly will depend on the physical shape or 'topography' of the land, the land cover and the soils it falls into. This channelling system is called a catchment – a system of surrounding hills and valleys which channels the water down along streams and through the soils and rock, sometimes into lakes but finally into the sea at a common point. Different catchments can feed into one lake. It is important to understand this process because the lake or sea that might receive some of your community's wastewater may also be receiving wastes from other places.

So when you are thinking about the effect of your community's wastewater treatment system, you will need to think about what is flowing down through the catchment from farms, businesses, the bush and other towns. The run-off may all be flowing into a river, lake or estuary and the total effect may be more than the overall natural system can handle. At the very least, it could have an impact on public health that you may not have taken into account when thinking about the effect of just your own community's wastes.

The ‘three waters’– water supply, stormwater and wastewater

Humans use water for drinking, washing, industrial processes, irrigation and transporting wastes; for recreation, swimming, fishing and spiritual purposes. As a result of some of these activities, wastewater is created. In addition, human settlement contributes to stormwater run-off.

Stormwater is the rainwater that has hit surfaces and runs off rather than seeping down into the soils. There is usually more run-off from impervious surfaces such as roofs of houses, roads and footpaths than from more permeable surfaces such as farmland, sportsfields and lawns. If it is not managed, this stormwater will cause flooding. Generally it is channelled on to roads or into open water courses, then down into a piped system and discharged into the streams, rivers, lakes and the sea. Sometimes – but less often – stormwater is combined with sewage in a drainage system.

There are two reasons why it is important to keep stormwater in mind when thinking about wastewater management:

  • untreated stormwater contains pollutants that will affect the same catchment and 'receiving waters' that receive the treated wastewater
  • stormwater can infiltrate your wastewater treatment system – cracks in pipes or the septic tank can allow stormwater to enter, or some people may have roof downpipes discharging into the wastewater pipes. This can put an extra load on your treatment system and cost extra money.

Wastewater includes natural liquid wastes created by humans (such as urine and bathwater), and water that has been combined with other wastes (such as faeces and the end-product of some industrial processes) to allow their easy transportation. More on this later.

The important point here is that the 'three waters' – water, stormwater and wastewater – must be taken into account when thinking about human wastewater management. They are created either when humans divert water from the natural water cycle for their needs, or because of human settlement. The human water cycle and the three waters and their inter-relationships are shown in Figure 1.2.

Figure 1.2 The three waters

This figures describes the three waters. Water as rain hits built and paved surfaces, becoming human-created stormwater, and is reinserted into the natural cycle. Rain is also collected for human via dams and roof tanks. Human-created wastewater from this is also reinserted into the natural cycle, along with water as natural run-off or groundwater. All three waters then join with lakes and oceans.

1.3 The nutrient cycle

The various parts of an ecosystem are intricately interwoven by food chains and the 'nutrient cycle'.

Figure 1.3 A simplified nutrient cycle

This figure portrays a simplified nutrient cycle in which animals and birds eat plants; humans eat plants, animals and birds – and waste products from all of these are returned to the soil. Nutrients from falling leaves and other plant material also return to the soil, helping the plants grow to continue the cycle.


Different nutrients (eg, phosphorus and nitrogen) are subject to different mechanisms, but they all follow the same basic pathways of Figure 1.3. 'Waste materials' from one organism are either used directly by another, or are converted (by natural processes) to something that is usable by something else. For example, when an animal dies its body decomposes (via bacteria) and becomes part of the soil. The soil holds minerals and nutrients from a variety of sources, which are taken up by plants, the plants are eaten by animals or harvested and eaten by humans, and then returned to the soil as wastes, which are then absorbed back into the soil as nutrients.

The breakdown of organic waste is the most important step in the nutrient cycle. It involves many types of microscopic plants and animals, mainly bacteria, fungi and protozoa. One organism may break down an organic compound making some residual by-products available as food for other organisms. Or it may itself provide a meal for another micro-organism. These in turn will go through the same process, with the continuing breakdown cycle eventually yielding nutrients and minerals in the soil in a form that is available for use by higher plants and animals.

The nutrient cycle does not only take place on land. Rain and surface-water run-off will carry un-decomposed organic matter, nutrients, minerals and gases dissolved from the air into streams, rivers, lakes and the sea. Here, a similar break-down process takes place. This water cycle is sometimes made more complicated in that fish and other aquatic life have to compete with the micro-organisms for the oxygen dissolved in the water. If the micro-organisms' food supply is too high, they proliferate and use up most of the dissolved oxygen, leaving insufficient for the rest of the aquatic life.

This oxygen-deficient environment then enables a new group of micro-organisms, called 'anaerobes', to flourish. They also break down organic matter, but instead of producing carbon dioxide as a by-product they generate methane, hydrogen sulphide and other smelly sulphurous gases often associated with septic systems.

The nutrient cycle can be viewed as the natural waste management system, although in reality there is no such thing as 'waste', since one organism's waste is another's resource. Nutrients and substances such as metals move around the cycle, sometimes accumulating at different places in the food chain. This 'bio-accumulation' can be an issue for human health.

1.4 Ecosystem services

This nutrient cycle, which is common to any ecosystem, can be seen as a free service to all ecosystem members, from micro-organisms, soils, plants and birds, through to animals, including humans. It provides food, and deals with materials that might be harmful unless absorbed back into soils or water. This idea of an 'ecosystem service' was first used by economists, who recognised that nature was providing humanity with a wide range of services that were not being valued.

These services, which are essential to human survival, include:

  • keeping water clean and uncontaminated
  • keeping the air clean
  • pollinating plants, which then provide food
  • recycling nutrients – in effect a waste management system
  • providing a gene bank for crops.

Some examples of the services provided by a number of ecosystems are provided in Appendix 1. Often these services are ignored when people make decisions about wastewater management systems. Considering them doesn't mean that a community now has to look at completely different wastewater treatment systems than in the past. It does mean that you will need to:

  • understand your local ecosystem services and how they work in your area
  • recognise that these ecosystem services are at least as important as the services provided by the economy
    (a wastewater system needs to provide not just for the needs of local industry, the local school or residents, but also for the needs of the overall ecosystem which includes these things)
  • design a system that avoids overloading natural processes (eg, reducing the volume of wastewater entering the system, reducing the toxicity of the waste entering the system, or avoiding discharge at one single point)
  • choose a system that 'mimics' natural processes as much as possible.

It really means understanding your wastewater system as a subset of natural systems – not as an alternative. This theme will be looked at again later.

Questions your community needs to think about when looking at the natural water cycle and the 'three waters'
  1. What is the effect of taking water from the natural processes (eg, the amount of water flowing in the local river)?
  2. What are the connections between the three waters? How do the water supply and the plumbing fixtures affect the wastewater quality and quantity? 2
  3. How can you manage your wastewater to minimise this kind of impact?
  4. Do you really need to generate the amount of wastewater or stormwater you do?
  5. How is the re-entry of the stormwater and wastewater being managed now? (Eg, is it completely bypassing the natural process of water percolating into soils and going straight to streams or rivers? Is there an alternative?)
  6. What nutrients are being transferred as part of the water streams? Where do they come from and where are they returned to? What happens to the nutrient cycle?
  7. How well can our community design its wastewater system to mimic these natural processes?

These are not idle questions. Remember the idea of ecosystem services? Understanding the water cycle will be a key to maintaining them. In particular, how wastewater re-enters the natural water cycle and what wastewater has in it will have a profound effect on the nutrient cycle and its life-supporting capacity.

1.5 Māori concepts of natural systems

So far this account of natural systems or ecosystems has emphasised the physical. However, for many people there is something more than this. Many cultures hold a spiritual belief in the environment. The nature of this spiritual dimension will vary across and between cultures. Groups may also have beliefs about the 'right way' to behave in relation to the environment, whether or not there is an obvious physical outcome from their actions. In other words, a person's relationship with the environment results in a series of principles about the best way to behave. Environmental effects are important but are not always the main driver for behaviour. Views on how these principles will be given effect will vary from culture to culture and between individuals.

The issues of waste management can bring these more complex feelings to the surface. Often, there is uneasiness about the idea of drinking water that contains even treated reclaimed water from an upstream community, whether or not it can be proved that there is no physical human or ecosystem impact. The reason for this uneasiness can be difficult for people to explain. The idea of stewardship and care is often overlooked in formal processes in favour of a focus on effects. Communities often attempt to group these ideas into categories such as effects on landscape, heritage values, character and amenity. Sometimes these categories will align with and indicate these beliefs – sometimes they will not.

This focus on effects, especially physical effects, can deny a view that there are principles of behaviour that should be considered in wastewater management. This is an important issue in New Zealand. Many Māori have a very clear view of the world, which goes well beyond a purely physical focus. It is one that leads to an equally clear position about what makes a good wastewater system.

This perspective is often described as being a holistic approach to the environment, deriving from a view of the world that links people and all living and non-living things. Although the degree to which individual Māori, iwi or hapū adhere to these ideas and views will vary, it is clear that a traditional relationship with the environment remains an important part of the lives of many Māori today. Accordingly, decisions about the right way to act may often be based on principles linked to the relationship between humans and the environment, rather than effects. Recognising this is a key step to understanding the different priorities Māori may have in terms of wastewater management, and the different issues it may create.

Such a view of the world also appeals to many non-Māori. This section describes some of the concepts that have been identified as fundamental to Māori in relation to wastewater management. Although these ideas may be well known to many Māori readers, it is important that the concepts that often become a part of wastewater decision-making at a local level are also well understood by the wider community.

The concept of mauri

The traditional Māori world view involves a belief in a spiritual dimension that permeates the physical world, binding all things together. Each life form is imbued with its own force or essence, through which it makes its contribution to the cosmos, and to everything around it. This essence is known as mauri.

Given the interconnectedness of all things in the Māori theory of the origin of the universe, any actions that change or degrade the mauri of one thing will have a corresponding impact on the form or integrity of another. In the traditional context, for instance, it was never simply enough to demonstrate respect for the physical environment; a corresponding obligation to protect and safeguard the mauri at the heart of it was also created.

Indeed, it is the kaitiakitanga and protection of the mauri of each part of the natural environment – and of people – that is still the focus of environmental management for many Māori today.

Kaitiakitanga

In the traditional world view that has been maintained through to the present day, care for the environment is not seen as being limited to stewardship, but is inseparable from care for oneself and for others. The exercise of this responsibility is known as kaitiakitanga, and it requires the active protection and responsibility for natural and physical resources by tangata whenua – the people of the area.

Persons charged with this responsibility are known as kaitiaki.

The water cycle

A highly simplified interpretation of the traditional Māori view of the water cycle reflects this idea of parallel and linked physical and spiritual worlds. Water passes in its purest spiritual form (waiora) as rain down to the earth. Here the mauri is at its most pure. Reaching the earth it will be affected by a range of natural events and actions. Failure to protect water quality harms not only its physical nature, but also its very essence, or mauri, which can only be restored as the water passes through the earth and into the sea (and then back to rain). In a purely physical sense this reflects the idea that water can be cleansed of many pollutants by passing through vegetation and the earth before entering the sea. If the spiritual dimension is to be restored, water must pass through the earth, or Papatuanuku.

A very simple form of the water cycle is depicted by the following diagram:

Figure 1.4 Traditional Māori view of the water cycle

This figure describes a simple form of the water cycle in the Māori world view. Waiora, water with the purest mauri or life force, falls as rain. Rain that hits the earth becomes waiMāori, and can be used for daily activity. The mauri is a force for good if well treated. This can then become polluted or waimate (the mauri can become evil and harmful). To be cleansed, the water must pass through the earth (Papatuanuku). From there it becomes waitai as it enters the sea and the mauri is restored, before becoming waiora once again.

The mixing of waters

It is notable that in the traditional Māori world, harm to one part of the environment could not simply be offset by protecting and improving another. The mauri of each aspect of the natural environment is particular to that aspect – to a specific stream, river, bush, tree, mountain or person. If the mauri of one place was mixed with that of another it could cause harm.

This is especially relevant in terms of streams, rivers, lakes and harbours. If waters from a river in one catchment are transported into another catchment, these spiritual forces will be mixed. Something that often happens with wastewater systems, where water might be collected in one catchment and piped to another for use by a community, with the wastewater system emptying into yet a third catchment, is likely to be significant for Māori and others taking a traditional approach to ecosystem or environmental management.

The human place in the natural world

The traditional Judeo-Christian view, which has fashioned much of the heritage of non-Māori New Zealanders, sees humans as apart from nature but having a duty to God to care for its well-being. The traditional Māori view, however, is premised upon a knowledge, which defines the origins of the universe and the place of humans and other life within it. All life forms – animate and inanimate – have divine origins, with each having a genealogy or whakapapa back to the gods as the source of their life and being.

These traditional views should not be seen by non-Māori as threatening. In fact, there are many similarities between these beliefs and modern environmentalism, in which people, all living things and the inanimate world are interlinked in mutually beneficial ecosystems. Some environmentalists see the earth as a single living organism, or Gaia, and view their relationship to this natural system in a spiritual way.

1.6 Taking a systems approach

Taking a systems approach means thinking about the relationship between wastewater management and the social and economic systems or structures that encompass your community. This has three parts:

  • the physical and natural resources and the environment within which a community lives
  • the kind of local economy and social community that currently exists
  • the pressures for change that may alter these arrangements.

All are important. Your wastewater system needs to fit current circumstances. For example, your community may be primarily a beach settlement with some permanent residents and some visitors in the summer and weekends. It may also have one or two families that make a living from fishing, running the local garage and shop, or perhaps some other small business. It is important to design your wastewater system so that it has the capacity to cover all these needs, and to see provision for business wastes – no matter how small – as part of the package, not as an afterthought.

Your community may also experience long-term change. Coastal communities, especially those close to a major centre (eg, Waikanae on the Kapiti coast) may be growing rapidly. A small rural community in the south may be experiencing population decline. Your community may be dependent on one major business, such as a dairy company, meat works or food-processing factory. That business may grow, it may decline, or it may simply move if it can see that it is cheaper to operate somewhere else.

How your community designs its wastewater system around these changes will be important. This section briefly discusses some of these issues.

Coping with a growing community

The physical pattern of settlement of houses and buildings that exist to support your community will have been created by four main factors:

  • the original historical reasons for the settlement
  • past population growth pressures
  • consequent decisions that were made about wastewater systems
  • how the local council regulates and controls growth
  • economic drivers.

Your community may have been established as a service town. It may have grown up as a small coastal port or landing area, as a beach resort, or as an employment base for a local industry. To some extent, the size of the sections will have been set by the ability to manage wastes on-site.

The kind of wastewater management system you have inherited will depend in part on how fast your town grew, or was expected to grow. If the population pressures were large, even in the early years, then the sites would probably have been relatively small, pushing the community into alternatives to on-site privies and septic tanks. Sometimes a wastewater system will have been built in the expectation of growth or as a way of attracting growth – by providing businesses and developers with certainty about waste disposal.

Since the introduction of the Town and Country Planning Act in 1953 (now replaced by the 1991 Resource Management Act), a local authority has had the ability to manage growth. Local communities can control the amount of land that is released for development and the effects of activities on the environment via rules in their district plan. This means the community has a significant say in the direction the settlement takes and the kind of investment it wants in wastewater systems.

But the process of settlement change is more complex than the development of simple growth-control rules. In reality, a council will manage growth with two tools.

  • Deciding the level of community investment in infrastructure, including wastewater systems: this, along with the natural ecosystem, will set the capacity for growth and change. For example, if you have on-site systems, it will be difficult to subdivide. Your community may increase but it will be dependent on the release of new land. If that land can't be released, then your community will remain relatively small. In some cases the decision to fund infrastructure is a direct decision to manage growth pressures.
  • Setting rules for the extent of settlement: these rules will be influenced partly from a community's vision of what it wants, partly by whether there are adequate services to deal with the effects of development. Even if land is released, if the wastewater system is inadequate then development will not be possible. Or it will be made much harder.

Sometimes a community will be examining its wastewater system because of growth pressures. There may be community agreement that population or business growth would be good for the local economy. A barrier to that may be that the wastewater system cannot cope with the growth, or there may be pressures from individual developers to allow more settlement and the general community is opposed to that. They are opposed not just because it would require investment in a new wastewater system (and other services), but also because it would fundamentally change what the community is. There will be many and varied views of how development should or should not occur.

Often local authorities have used decisions about whether they will extend access to a network to small rural communities, or pay for a local treatment system, as a way to control growth pressures. Lack of access to more treatment capacity becomes the rationale for limiting growth.

Oneroa Village, Waiheke Island, Auckland City

Waiheke Island has traditionally been serviced by conventional septic tank and soakage field systems. Clay soils and difficult topography limit the use of this approach, however, and over recent years a variety of alternative systems have been utilised, such as pre-treatment via aerobic treatment plants or sand-filter units, and disposal via evapo-transpiration beds or drip irrigation systems. These can be satisfactory for lower-density residential development, but for the commercial centre of Oneroa Village, with its high water-use activities, on-site systems have become unsatisfactory.

During the late 1990s council consultants undertook a detailed options study, which included community input. One objective set by the community was to examine a part on-site, part off-site scheme whereby the site capacity to handle effluent soakage was determined for each lot, and any excess wastewater unable to be accommodated was then to be diverted off-site to a limited-capacity community reticulation scheme.

The practical implications of splitting wastewater effluent flows for individual property on-site soakage and off-site diversion proved unmanageable, and led to the finding that a full off-site reticulation and cluster treatment scheme was the most appropriate option. A council-conducted consultation process involving the public and iwi then proceeded to develop a centralised scheme for the village commercial area and several surrounding residential streets. Nevertheless, many residents were not satisfied that the consultation process was adequate.

The final scheme was commissioned in 2002. The council consultation identified the most appropriate effluent discharge method to be via a constructed horizontal-flow wetland into an existing natural wetland. A recirculating sand-filter system was selected as the most appropriate secondary treatment system prior to tertiary treatment in the constructed wetland. The sand-filter system has a stable treatment process, low maintenance requirements, and the ability to accommodate large load fluctuations. The whole treatment plant site has had a native tree and shrub planting programme to provide visual screening, and to offset the loss of native plants due to upgrading the site access.

Development can encourage growth

Sometimes communities press for a community system because they feel it is the only way to solve public health or environmental issues. This may increase the capacity for growth. For example, even if new land is not released, the limits set by septic tanks on existing sites no longer apply. Subdivision can now take place. Many people may not be aware that changes to the ways the community deals with sewerage open up opportunities to increase growth.

This is a key issue for coastal communities. For example, do you want to stay a low-key bach community, or do you want to grow? There will be tensions, and often they will be played out around what seems to be a simple question of providing a better wastewater system. Improving the water supply and disposal facilities may increase the desire of others to live there, encouraging growth. This is a complex issue. Decisions about wastewater systems can become decisions about your overall community vision.

Developing a better wastewater system does not have to lead to this kind of problem if there is clear community debate about what kind of community people want – and careful selection of a system that fits that vision. It is very important that each player in the process thinks about and is prepared to debate how their views on issues and risk will affect the community's vision about the size and nature of their community.

Coping with a declining community

Some parts of New Zealand are dealing with population decline. Much thinking about wastewater systems is focused on the relationship with population growth and the impacts of increased volumes of wastewater on the environment. Not much has been said to help a community deal with population loss and what it means.

A community experiencing population loss will be placing less pressure on the environment, but it may face problems because the wastewater management system no longer fits the social and economic realities. Your community may find that the system developed in the past is no longer needed, yet it still has to be paid for.

For your community the real question is: Should you disinvest ('get out of') your current system and develop something more in keeping with your needs? This is a question that is not often asked or contemplated. It seems that once a community has gone down one path it cannot turn back and try something different. But it is possible.

You may decide that it is better to abandon the old system and reinvest the money you spent on maintenance on a new, lower-key technology. You may even decide a return to on-site systems is possible. This is radical stuff, but just because you have one system now doesn't mean you can't change. It is not an issue of going from the primitive (on-site systems) to the modern (centralised). It is an issue of finding the system that best fits your community.

If you were to do something as radical as abandoning your existing system, you would need to be very sure that the population would not stabilise or even increase in the future. At the very least, you would need to be reasonably sure that this would not happen during the life of your wastewater management system. For example, most pipes have a life of 80 to 100 years and treatment plants will probably have a similar life if well maintained. ('Life' in this context means how long they will last before they wear out). You would need to be sure that your community is likely to continue to decline or stabilise at a level that does not need the current system.

A local authority is required to fund the depreciation of its physical assets; in other words, to fund the replacement of those assets over time. This requirement means that a community would have to make a transparent decision that it wished to change the level of service, or re-invest in a different kind of system. Levels of service include both provision for health concerns and such things as convenience of service. It is important to make a distinction between levels of service to do with health and environmental issues and those standards that relate to the particular kind of system your community has. For example, on-site systems may be less convenient because they require more monitoring by residents, but they may provide a higher level of service in terms of environmental impacts. These issues would need to be worked through carefully.

If you are considering this kind of approach, the important questions become:

  • When should we think about investing in a different system?
  • How can we maintain health and environmental standards while the changes are achieved?
  • Is it cheaper to invest in trying to capture growth than to find a new system? Is that a realistic goal?

You can continue to maintain the system for the normal length of its life and then change when it needs replacing. Or you can reduce the levels of maintenance, which will shorten the system's life, invest the money short term in other methods to protect environmental and public health, and reinvest in new systems over time, which might risk non-compliance with consents. Or, you can simply cut your losses and reinvest in a new system, provided there is an overlap in terms of protecting public health and the environment. It will come down to a simple matter of cost. Does it cost more to continue or less to reinvest now or later?

Coming to grips with this kind of question means a community needs to step well outside the immediate issue of wastewater management to think about what might be the real nature of the future population and economic opportunities. The essential point is that a community does not have to be locked into increasingly complex wastewater systems. It can choose.

The people in your community: now and over time

The issue of population decline makes the link between wastewater management systems very real. If the system does not fit the social make-up of the community as well as ecosystem processes, it won't work. Because there will be intense external pressures to maintain the system – from public health authorities and regulatory agencies – the cost of this 'poor population fit' will be borne by individual households. This will either be in the form of rates payments or, if wastewater charging is brought in, as a direct charge. This has huge implications for what are often poor and isolated communities. While a new treatment system may seem desirable, the costs may themselves contribute to social and health problems.

This is also true for communities which, even if they are not declining, may be ageing or may have a high proportion of families on small or fixed incomes. You will need to make some estimates about the changing nature of your community over time. You may have a young working population now, but it will get steadily older and will probably be replaced by fewer younger people. This is a national trend, but your community may age at a faster-than-average rate. You will need to consider this when choosing a system.

Managing your wastewater system

The issues of population decline and change may well force you to think about whether a large and/or expensive system with a very long life is the best kind of approach to take. The ability of people to manage the systems they have, particularly on-site systems, needs to be thought about carefully. Older people on a fixed income may not be able to afford the upkeep and maintenance of a septic tank. Seasonal visitors may not understand the need to do so.

There is a range of solutions available. For example, the community may pay a small rate to the council to have them undertake the maintenance. Or they could band together more informally to take care of the issue. A technical engineering response of moving to a centralised or cluster system, say, may not be necessary. Management of the final system should be seen as part of the wastewater system design – in effect, linking wastewater management to the local social make-up of the community.

Whatever else is done, it is a good idea for all communities to consider the benefits of continual monitoring of local systems (see Section 6 for a discussion of management and monitoring and Section 11 on management and funding of wastewater systems).

Human systems: the issue of flexibility

What this adds up to is the need for a more subtle or sophisticated way of thinking about how wastewater management systems fit the 'human bit' of your local ecosystem. The changing nature of that human bit is often not well thought through. This is not just a simple issue of making sure that cost is not a hardship for communities. It has a great deal to do with the kind of system you choose. How flexible is it? Can you add to it and take away from it? How long are you locked into that system? What sort of future does it push your community towards? Can people manage it over time?

It is extremely important in making your decisions about what wastewater system and what technology you want that you think about these long-term issues.

Castlepoint sewerage scheme: development follows wastewater

Castlepoint is an historic beach settlement located to the east of Masterton in the Wairarapa. As late as the 1990s the area continued to have some long-drops, but most sites had on-site systems. A community scheme was suggested in the 1970s but this was rejected. By the 1990s there was increasing concern about beach pollution and the community began to take action. The process was one of initial community concern, followed by consultants developing options, with one option finally chosen by the community. The final choice was for a central treatment system with oxidation ponds.

The implications for development were never discussed as part of the options development process. Since installation of the system, the area has developed rapidly. The problems of beach contamination were solved but as a result the pressure to develop this quiet seaside settlement has increased. Smaller lots have been created and there has been a rapid increase in property values and population. This may be acceptable to the community, but the changes were unanticipated at the time. The opportunity to think through both wastewater and development issues was passed over.

Footnotes:

1 Photosynthesis occurs in all green plants. It is the process by which sunlight is used to turn carbon dioxide and water into sugar and oxygen. return

2 For example: The use of copper pipe and brass fittings can cause heavy metals to leach into the water supply. They then reappear in the sludge at the sewage treatment plant and may end up in any compost made from the sludge. return