Onsite and Decentralised Sewerage and Recycling Conference12th – 15th October 2008Benalla, Victoria
Appropriate Technology Selection for Decentralised Wastewater Systems
The Decentralised Wastewater Treatment and Recycling Systems Electronic Decision Support
Tool (DeWaTARS EDST)
Professor Goen Ho, Emma Tomren & Dr Martin AndaMurdoch UniversityPerth, Western Australia
Tomren, E., Anda, M. and Ho, G. (2008) Appropriate technology selection tool for decentralised wastewater treatment systems. In: Onsite and Decentralised Sewerage & Recycling Conference, 12 - 15 October, Benalla, Vic, Australia.
Centralised sewerage systems
and wastewater
treatment plants
TRADITIONAL
THE CURRENT
TRANSITION
FUTUREDistributed
(onsite and decentralised)
wastewater treatment and
recycling
BENEFITS OF DISTRIBUTED WASTEWATER TREATMENT
Ability to treat different waste streams separately
Increased reuse and recovery of treated water
Improved energy efficiency
Improved nutrient management
BARRIER TO IMPLEMENTATION: APPROPRIATE TECHNOLOGY SELECTION
extensive range of commercially available distributed wastewater treatment technologies
implementers often have limited knowledge regarding technologies
many factors must be considered to determine appropriate technology:
- environmental sensitivity - required effluent quality - cost - available energy, etc.
DECISION SUPPORT TOOLS (DST)
DST: takes into account a large array of factors that must be considered when choosing appropriate technology
e.g. SANEX which determines appropriate sanitation technology for developing countries by:
1. Screening out inappropriate technologies
2. Evaluating remaining technologies
Figure 1: Illustration of the two stage evaluation process incorporated into the SANEX program.
THE DEWATARS EDST
Decentralised Wastewater Treatment And Recycling System Electronic Decision Support Tool
developed by Shaun Jamieson in 2006
addresses appropriate technology choice for decentralised
wastewater treatment for the Perth Metropolitan Region (PMR)
two main concepts: source separationsustainable water management
HOW IT OPERATES: PRACTICAL
follows the SANEX framework, utilising filters to eliminate and evaluate different technologies
binary algorithm: a number of questions asked of the user over a series of flow sheets
has been programmed into MS Excel
allows uncomplicated use of the tool
Is the soil type sandy?
A sandy soil type is rapidly drained and has a limited ability to retain nutrients (PRI generally less than 5).
No
Yes
Figure 2: An example of the DeWaTARS EDST user interface
ELECTRONIC ADAPTATION
HOW IT OPERATES: THEORETICAL three main filters:
1. Local geographical factors (nutrient risk)
2. Development characteristics (scale of collection: lot, cluster or village)
3. Specific user preferences (e.g. combination of waste streams, reuse or disposal)
end point: technology options and additional components for appropriate wastewater treatment and reuse/disposal are recommended
user can compare options in the DeWaTARS database
THE DEWATARS DATABASE
7 technology categories in the database:1.Aerobic Treatment Units2.Soil, Sand & Peat Filters3.Composting Systems4.Ponds & Wetlands5.Anaerobic Systems6.Physico-Chemical Systems7.Greywater Treatment Systems
These are evaluated and given a score according to:- removal of organics - removal of
nutrients- energy use - maintenance costs- capital costs - footprint- required maintenance - sludge production
CURRENT RESEARCH
Examine the DeWaTARS EDST for application to a wider range of
wastewater situations, particularly remote tourism areas, with the main
focus on energy efficiency and nutrient management.
METHODS
Case study application of the DeWaTARS EDST:
- determination of strengths and weaknesses
- redevelopment of the algorithm to broaden scale of application
- redevelopment of the algorithm to incorporate improved energy efficiency and nutrient management if required
Case Study Site Nutrient Risk
Scale of Collection
Other Factors
Nambung National Park, Pinnacles Desert
Medium Lot or cluster
-Energy produced onsite by PV cells & a backup generator-No sewer connection
Single Residence, Mt Nasura
Low Lot -Energy efficiency desired by homeowners-No sewer connection
Timbers Edge Residential Resort, Dawesville
High Lot, cluster or village possible
- No sewer possible
Banksia Tourist Village, Hazelmere
Medium Lot, cluster or village possible
- No sewer connection
Bridgewater Lifestyle Village, Erskine
High Cluster - This site was examined into wastewater treatment from the community clubhouse
RESULTS e.g. Nambung National Park:
Medium Nutrient Risk & Lot Scale of Collection
Blackwater Greywater
Toilet type Dual flush Greywater Type Including kitchen
Scale of collection
Lot Scale of collection
Lot
Core treatment Amended Soil Trench
Core treatment Amended Soil Trench
Additional components
Primary humus filter
Additional components
-
End application Infiltration & Evapo-transpiration
End application Infiltration & Evapo-transpiration
FINDINGS: ENERGY
the DeWaTARS EDST made the assumption that energy is available at all sites, without limitations
aerobic treatment units were often recommended, many of which are relatively high energy consumers
the energy assessment of the technologies was ‘post-algorithm’ in the DeWaTARS database evaluation; technologies are first selected, then evaluated for energy use
FINDINGS: NUTRIENTS
an adequate site nutrient assessment is already incorporated into the algorithm
levels of nutrients in the wastewater sources are assumed to be uniform; where in situations such a Nambung, short visits to the site would result in a higher nitrogen content due to increase urine input
urine separation is recommended on the basis of provision of a fertiliser, rather than the need to reduce nitrogen content in the wastewater
there is also limited focus on the potential inputs of cleaning products that are high in phosphorus
FINDINGS: OTHER LIMITATIONS
Scale of collection: while this allows appropriate application for urban developments, it complicates application to non-residential buildings and other establishments such as visitors centres in national parks
Toxicity: there is the possibility of tourists emptying caravan and campervan chemical toilets into the wastewater stream at tourist locations, it is essential that wastewater treatment technologies are capable of dealing with such inputs
REDEVELOPMENT OF THE DEWATARS EDST FOR APPLICATION TO REMOTE TOURIST AREAS 1
Primary filters for the new DeWaTARS EDST:
1. Local geographical factors (nutrient risk)
2. Energy availability (no energy, limited, unlimited)
3. Development characteristics wastewater flow rate: high, medium or lowwastewater type: blackwater only or combined
blackwater and greywater
REDEVELOPMENT OF THE DEWATARS EDST FOR APPLICATION TO REMOTE TOURIST AREAS 2Other factors incorporated into the algorithm:
land availability/footprint - can land be cleared to allow for technology implementation?
maintenance issues – remote tourist areas require technologies that do not need regular maintenance
urine separation to reduce nitrogen levels in wastewater influent
variable flow – is there significant variation in wastewater flow at the site? Which technologies can deal with this?
toxicity evaluation – must the technology be resilient to possible toxic contamination of the wastewater due to misuse of facilities?
ACKNOWLEDGEMENTS
Wendy Green & Shaun Jamieson for their work in developing the DeWaTARS EDST and Database
The Premier’s Water Foundation for funding Shaun’s research
Department of Environment and Conservation (WA) for funding the research of Emma Tomren to further develop the DeWaTARS EDST for nutrient management and energy efficiency in remote tourist locations
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