Table 12.2 Scoping the options: less common systems – benefits and limitations
| Type of system | Brief description and possible benefits | System and site limitations |
|---|---|---|
| Reclaimed water recycling | Reclaimed water sourced from treated wastewater effluent can be recycled for non-potable water uses, although this requires a high standard of treatment. Such systems include multi-stage treatment, recirculating sand filters and disinfection. Recycling of reclaimed water for on-site toilet flushing, laundry and car washing and irrigation is possible. This is an appropriate option to consider if potable water is expensive or in short supply. | Careful consideration must be given to potential health
risks. Such systems require a high standard of treatment, disinfection
and management. Separate and clearly labelled plumbing and outlets are
necessary. No NZ guidelines are yet in place to cover such on-site recycling uses, so local authorities are unlikely to grant approval until the Ministry of Health has assessed risks and devised appropriate guidelines for risk elimination. |
| Composting toilets | Composting toilets are waterless (dry) or minimal water use (wet) toilets that use aerobic bacteria and other micro-organisms to biodegrade the faeces and other organics. There are various designs suitable for outdoor installations (eg, forest parks) and domestic installations. Modern composting toilets are designed for domestic use as clean, odourless facilities. Benefits include low water use, and recycling of organic matter and nutrients | Well-designed domestic composting toilets can be expensive and require competent, consistent and dedicated management. Some require sufficient under-floor clearance for the composting chamber. The composted solids require handling and appropriate safe burial. Most composting toilets will not accept greywater, so a separate and approved greywater system will be required. Many councils are reticent about approval because of perceived health risks if compost toilet systems are not properly operated and maintained. Compost removal must be undertaken to strict hygiene standards, so regulatory obstacles often face people seeking to use this type of system. |
| Vacuum toilets | Vacuum toilets for domestic applications are not common in NZ (the only system is at Turoa Skifield, Mt Ruapehu). They have been used in countries where water is expensive or in short supply. These toilets use very low water volumes (0.5–1.5 L/flush). Benefits include low water use and wastewater volumes. Concentrated blackwater offers better technological opportunities for nutrient recovery (eg, liquid composting). | The vacuum unit, toilets and vacuum pipes are expensive
and require skilled installation and design. For some people the noise
of the vacuum can be off-putting, although recent designs have eliminated
this problem. Technology and expertise are not common in NZ. |
| Separated systems: greywater blackwater, faeces and urine | Separation of the various wastewater components enables separate management and recovery of the water and the wastewater nutrients. Most nutrients are contained in the urine, while most of the water is in the greywater. Urine-separating toilets are available and plumbing can be installed to separate these streams | Separate plumbing is required and will increase building costs. No cost benefits are gained if connected to centralised system. On-site systems require suitable treatment systems for each component, and land area and soils for ecosystem re-entry. Many councils are not familiar with these options |
