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