Table 8.3 Examples of on-site treatment technologies

Combined blackwater and greywater systems (all waste)
On-site treatment option	Comments
Conventional septic tank	Septic tanks can be single-chamber or multi-chamber. They must be constructed to meet required standards (eg, AS/NZS 1546.1-1998). Septic tanks require de-sludging every few years depending on loading rate, composition of wastewater and temperature.
Improved septic tank (equipped with an effluent outlet filter)	There are various types of septic tank filters available to reduce carry-over of suspended solids. These require routine cleaning.
Improved septic tank with subsurface flow wetland.	The wetland size and dimensions need to be designed for the wastewater loading. Wetland plants are grown in aggregate, with the effluent water level maintained just below the aggregate surface. They need to be designed and installed by qualified and experienced persons.
Improved septic tank with intermittent or recirculating sand filter	These produce very high-quality effluent suitable for drip-line irrigation into or onto land within landscaped areas, or providing a source of reclaimed water for recycle uses. They need to be designed and installed by qualified and experienced persons.
Aerated wastewater treatment package plant (AWTS)	These are small domestic wastewater treatment package plants capable of treating the wastewater to a high standard suitable for drip-line irrigation into or onto land within landscaped areas.

Separated greywater and blackwater system – blackwater components
On-site treatment option	Comments
Dry-vault blackwater systems: compost toilets dehydrating toilets incineration toilets	These require informed on-site management procedures to ensure safe handling and subsequent disposal of solids. Composting toilets in particular must have informed and dedicated users in order to achieve effective performance.
Wet-vault blackwater systems: pump-out vaults hybrid toilet chemical toilet low-flush systems	Pump-out vaults and chemical storage units require routine road tanker collections. The hybrid toilet system has been designed to use zero or very small volumes of flush water (about 0.3 L/flush). Such a system provides treatment of the low volume of blackwater to a high standard by anaerobic fermentation.

Separated greywater and blackwater system – greywater components
On-site treatment option	Comments
Conventional greywater septic tank system (outflows from hybrid and chemical toilet systems can be transferred to greywater treatment tanks for further treatment)	Must be constructed to meet required standards (eg, AS/NZS 1546.1-1998). Tanks require desludging periodically.
Improved (large-volume) grease trap preceding a constructed subsurface wetland	The wetland size and dimensions need to be designed and installed by qualified and experienced persons for the greywater loading. The grease trap will require regular (up to weekly) maintenance.
Greywater reclamation units	Use for recovery of bathroom and laundry waters for recycle for water closet (toilet) flushing.