System Matrix

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Possible criteria	Fully centralised system	Combination of on-site and centralised system	Cluster system	Fully on-site systems
Physical characteristics of site
Limitation of site or area, (eg, soils climate, groundwater aspect proximity)	Not applicable	The on-site component acts as pretreatment to the central system. This is likely to be a septic tank and/or pump and sump. Suitable area of land required on site. Some limitations of site. Septic tank to be accessible for pumpout servicing	Suitable local site location and area required. Specific site conditions and area required, especially for return of treated wastewater and sludge to the ecosystem	Site area, soils, topography and ground water conditions may limit on-site options. Septic tank to be accessible for pumpout servicing
Resilience to natural hazards	Vulnerable to natural hazards such as earthquakes and floods	Vulnerable to natural hazards such as earthquakes and floods	Impact of natural hazard event less than a fully centralised system. Flood risk	More resilient to natural hazard events. Flood risk
Ecological
Impact on surface and ground water, aquatic and other habitats, ecosystem services, soils	Large conventional sewer network resulting in urban impacts. Older networks can result in stormwater infiltration overflows from sewers and pumping stations. Site and technology specific. Must meet RMA consent requirements. Ecological impact of emissions (treated wastewater, sludges and any odorous gases) will depend on standard of treatment, plant management and sensitivity of receiving ecosystem and proximity of human neighbours	Modified or alternative sewer network required. Site and technology specific. Overflows from infiltration substantially reduced or eliminated. Must meet RMA consent requirements. Ecological impact of emissions (treated wastewater, sludges and any odorous gases) will depend on standard of treatment, plant management and sensitivty of receiving ecosystem and proximity of human neighbours.	Small scale modified or alternative sewer network required. Overflows can be substantially reduced by good design and construction. Site and technology specific. Must meet RMA consent requirements. Each cluster handles a smaller volume than a centralised system, so the ecological impact is likely to be less. Impact will depend on standard of treatment, plant management, sensitivity of receiving ecosystem and proximity of human neighbours.	No sewer networks required. Ecological impact all on-site. Very dependent on system technology and ongoing management. Will also be depend on sensitivity of receiving ecosystem.
Ecological restoration opportunities	Highly treated wastewater could be used for wetland resortoration	Highly treated wastewater could be used for wetland restoration	Highly treated wastewater could be used for wetland restoration	On-site wetlands could be fed with secondary treated wastewater
Resource efficiency – closing of ecological cycles	Often not considered by central authority. Very dependent on design and management of the system	Often not considered by central authority. Very dependent on design and management of the system	Local sewer network may save pumping and consequent energy demand. More recent systems are designed for efficient resource use and closing of ecological cycles	No sewer networks required. Greater opportunity for closing of nutrient cycles
Water recycling	Possible to achieve but would require high-quality treatment as well as provision of separate and readily identifiable reticulation to users	Possible to achieve but would require high-quality treatment as well as provision of separate and readily identifiable reticulation to users	Possible, but would require high-quality treatment and separate reticulation to user.	Very possible, but would require high-quality treatment. Greywater recycling for toilet flushing and garden watering is a viable technology already in use in NZ
Compatibility with Māori perspectives
Issue of passage through land	May be an issue but needs to site specific analysis. RMA process will address these issues	Maybe an issue - site specific. RMA process will address these issues	Cluster schemes provide opportunity for local land application and ecosystem re-entry
Protection of mauri	Dependent on siting and ecosystem re-enty type	Dependent on siting and ecosystem re-entry type	Dependent on siting and ecosystem re-entry type	All effluent applied to land, hence likely compatible. Unlikely to be a problem
Other cultural concerns
Local stewardship/ responsibility	Central system disconnects waste producers from relevant ecosystem's realities	Central system disconnects waste producers from relevant ecosystem's realities	More opportunities to 'tailor fit' local cultural requirements. Community has closer link to receiving ecosystem	Possible to fit to individual's cultural requirements. Very close links with receiving ecosystem "Neighbourly" conflicts possible
Re-use of reclaimed water	Likely to be a general cultural difficulty	Likely to be a general cultural difficulty	Likely to be a general cultural difficulty	Because of individual choice, expect wider acceptance
Public health
Operational safety	Generally a very high standard of public health safety	Generally a very high standard of public health safety.	Generally a very high standard of public health safety.	Dependent on technology and management. Approved systems that are well designed and subject to an inspection and management programme will be safe
Impacts on community health	Central systems generally remove and treat wastewater well away from public contact, thus minimising health risks. Treated effluent discharge to receiving waters must meet health standards for recreation and shellfish harvesting. Stormwater overflows from sewer networks can pose short term health risks. Strict controls apply to land application by spray irrigation	Central systems generally remove and treat wastewater well away from public contact, thus minimising health risks. Treated effluent discharge to receiving waters must meet health standards for recreation and shellfish harvesting. Stormwater overflows from sewer networks can pose short term health risks. Strict controls apply to land application by spray irrigation	Local cluster schemes mean public closer to treatment and re-entry areas. Health risk low if management of treatment and re-entry system maintained at a high standard	Risk low provided well designed and managed. Neglected systems can give rise to failure conditions, effluent surfacing, and high health risk to property dwellers and immediate neighbours
Residual management	All residual products are managed centrally	All residual products are managed centrally	All residual products are managed by the cluster management agency	Treated wastewater is managed on-site. Sludge must be managed off-site at an approved location. Composting toilets not favoured in urban areas by MoH
The technical system
Reliability	Usually reliable. Older sewer networks can present a significant infiltration problem. New networks are also subject to infiltration	Reliable. Infiltration can be minimised	Most modern systems will be reliable. More dependent on management structure, knowledge and skill	Dependent on technology quality, knowledge and skill, and a regular inspection and management programme
Serviceability	Usually easily serviced, although dependent on system design and management structure	More geographically dispersed, therefore serviceability more difficult. Dependent on system design and magagement structure	Usually easily serviced, although dependent on system design and management structure	Dependent on type of system installed and servicing protocol
Operational requirements	Operated by trained technicians	Operated by trained technicians	Should be operated and maintained by trained technicians	Operation and maintenance requirements must be diligent to avoid failure. Council organised management programme or independent operation and management contracts will reduce such risk of failure
Engineering life of the system	Long life	On-site components possess a medium to long life, whilst central components possess a long life	Medium to long life.	Medium to long life when subject to a management programme
Resilience to acts of vandalism.	Depends on system design and management. Because of centralised location, easier to reduce acts of vandalism	Depends on system design and management. Because of mostly centralised location, easier to reduce acts of vandalism	Generally located away from public eye, creating higher risk of vandalism	Systems are not normally secure, but vandalism not normally a significant problem
Linkages with other opportunities and services (eg water supply)	There are opportunities to recycle water and nutrients, recover energy, restore/create wetlands and provide an ecological education facility. Short-term economics usually constrains implementation	There are opportunities to recycle water and nutrients, recover energy, restore/create wetlands and provide an ecological education facility. Short-term economics usually constrains implementation	There are opportunities to recycle water and nutrients, recover energy, restore/create wetlands and provide an ecological education facility. Short-term economics usually constrain implementation	There are opportunities to recycle water and nutrients, recover energy, restore/create wetlands and other on-site landscaping. Implementation is dependent on individual motivation, funding and regulatory constraints
Ability to be changed
Extendability	Depending on design, most of the older, centralised systems are not so extendable or adaptable to changing requirements. Sewer infrastructure (and required flow velocities) can restrict future changes to other parts of the system. Land can be limiting. Infrastructure locks in system capacity, limiting adaptability. Normally adaptable to trade waste inflows	Depending on design, these system tend to be more recent and therefore extendibility may have been included in the design	Depends on design, but more likely to be adaptable due to being a smaller system. Funding may limit extendibility and adaptability	It is the individual property owner's responsibility to build in extendability and adaptibility. Most likely funding but also land area will limit the ability to respond to changes. On-site secondary treatment systems have limited opportunity to be extended for increased loading
Adaptability/flexibility		These systems tend to be a little more adaptable due to the lower cost of reticulation. However, adaptability will be rather limited. Normally adaptable to trade waste inflows
Management
Ownership	Normally owned and managed by city/district council	Normally owned and managed by city/district council	Can be owned and managed by city/district council or by corporate body	Owned by property owner. Normally managed by property owner, although owners can form a body corporate to oversee O&M
Convenience	Having all the operation at a central location simpifies management requirements	With some components on-site and most central, management will be less convenient	Management of cluster systems may be perceived as less convenient than a larger centralised system and more convenient than on-site systems. Centralised management of a group of cluster systems is recommended	Management requirements will depend on type of system installed. Traditionally, management responsibility lies with the property owner. Management may be by contract, or by a management agency, thus providing maximum convenience to the owner
Operation and maintenance implications	The centralised nature of this system makes operation and management uncomplicated	The operation and maintenace programme will need to be designed for a combination of on-site and centralised requirements		Operation and maintenance requirements will depend on the type of system installed. Servicing contracts are often employed, and inspection and management programmes are recommended to ensure long life of the system
Economic factors
Capital and operating costs	City/district council responsibility. Capital and annual operating costs are normally evenly spread across the community served. User-pays possible with water metering	City/district council responsible for off-site costs, and maybe on-site costs. In some situations on-site costs may lie with property owner. Capital and annual operating costs are normally evenly spread across the community served. User-pays possible with water metering.	Capital costs may be the responsibility of the developer or city/district council. Operating costs may be the responsibility of city/district council or a specially constituted corporate body	Capital and operating costs are the responsibility of the property owner. Where a council or body corportate management programme is in place, annual charges will be levied for O&M
Funding	Rates	Rates	Rates, or built into purchase price	Individual capital funding, and individual or body corporate or managment agency fees for O&M
Local community impacts
Level of local control	Community generally has minimal input into the design, operation and management of these systems	Community generally has minimal input into the design, operation and management of these systems	More opportunity for community input into the design, operation and management of these systems	Greater degree of control lies with individual property owners.
Need for external expertise/management	Usually a significant external input into the design, operation and management of these systems	Usually a significant external input into the design, operation and management of these systems	External expertise for the design is normally required. Management can be local or centralised	External expertise for technology selection and design is normally appropriate. Management can be on-site or centralised
Community change
Pressure for future growth	Stimulates urban growth, including commercial and industrial growth	Stimulates urban growth, including commercial and industrial growth	The cluster system will enable domestic localised growth. Less conducive to commercial and industrial growth	Local geophysical and hydrological conditions can restrict urban growth. Recent systems can overcome some of these constraints
Capacity to absorb growth	Depends on both total system design capacity and individual capacity for each component. Modern systems can be designed to accommodate future growth	Depends on both total system design capacity and individual capacity for each component. Modern systems can be designed to accommodate future growth	Cluster systems tend to be designed for a given cluster of homes. May be possible to absorb some growth, or additional cluster systems may be require.	Growth will be dependent on the suitability of the property's site for on-site management. However, growth within site boundaries is very rarely an issue
Other potential benefits
Leisure and recreation	Restored wetlands may be integrated with an urban park. Health risks would have to be minimised by appropriate pre-treatment prior to wetland re-entry	Restored wetlands may be integrated with an urban park. Health risks would have to be minimised by appropriate pre-treatment prior to wetland re-entry	Restored wetlands may be integrated with an urban park. Health risks would have to be minimised by appropriate pre-treatment prior to wetland re-entry	N A
Education	Opportunities to develop community education activities centred on wastewater, and social and ecological issues	Opportunities to develop community education activities centred on wastewater and social and ecological issues	Opportunities to involve local community in educational activities centred on wastewater and social and ecological issues	Opportunities to educate community to take greater responsibility for their waste
Research	Many research opportunities to study the resource value of wastewater	Many research opportunities at the centralised level to study the resource value of wastewater	Many research opportunities at the local level to study the resource values of wastewater	Many research opportunities at the individual level to study the resource values of wastewater
Formal processes
Familiarity to decision-makers	Decision-makers are familiar with these types of systems and traditionally place confidence in them	Decision-makers are less familiar with these types of systems but normally have confidence in them because of the final centralised management	Decision-makers are less familiar with these types of systems and subject such systems to greater scrutiny	Decision-makers are familiar with on-site systems, but often very unfamiliar with recent innovations and the benefits of inspection and management programmes
Technical demands	Requires expert engineeering input for design. Requires skilled operators	Requires expert engineeering input for design. Requires skilled operators	Requires expert engineeering input for design Requires skilled operators	Requires expert engineeering input for design Requires trained inspection, operation and maintenance personnel
Public health service	Strict health standards	Strict health standards	Strict health standards	Strict health standards
Ease of the consent process	Site and system dependent. Consenting process usually well resourced	Site and system dependent. Consenting process usually well resourced	Site and system dependent. Consenting process usually less well resourced	Consent under council building controls.

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