Environment, Climate Change and Water

Index:

7. Solutions to pollution

HSIE Stage 2 Outcomes

The activities associated with this topic meet the following syllabus outcomes:
Relationships with Places ENS 2.6

Geography Stage 5 Outcomes

The activities associated with this topic meet the following curriculum outcomes in focus areas 5A2 and 5A3:

5.1 Identifies gathers and evaluates geographical information
5.2 Analyses, organises and synthesises geographical information
5.3 Selects and uses appropriate written oral and graphic forms to communicate geographical information.
5.4 Demonstrates a sense of place about Australian environments.
5.6 Analyses the impact of different perspectives on geographical issues at local, national and global scales.
5.9 Applies geographical knowledge, understanding and skills to demonstrate active and informed citizenship.

Science and Technology K-6 Outcomes

The activities associated with this topic contribute towards achievement of the following Stage 2 outcomes:

PS S2.5 creates and evaluates products and services considering aesthetic and functional factors.
DM S2.8 develops, implements and evaluates ideas using drawing, models and prototypes at appropriate stages of the design process.

The activities also have links to the following Stage 3 outcomes:
PS S3.5 creates and evaluates products and services, demonstrating consideration of sustainability, aesthetic, cultural, safety and functional issues.
DM S3.8 develops and resolves a design task by planning, implementing managing and evaluating design processes.

Background information

Background material compiled from:

What We Need Is...A Community Education Project, NSW EPA and Department of Land and Water Conservation, 1997.
Managing Urban Stormwater - Treatment Techniques, NSW EPA, Nov. 1997.
Wake Up Call: Companies Preventing Pollution at Source, video, Oz GREEN, 1999.
Solutions to Pollution: Information Sheets for Small Industries and Businesses, NSW EPA, Environmental Information for Small Business. A series of information booklets for small- and medium-sized businesses to assess their environmental performance. NSW EPA.

Stormwater Pollution Prevention

Innovative approaches to stormwater management are required if our cities and towns are to be ecologically sustainable. In this unit of work students will design an innovative solution to stormwater pollution. Their design could be for a pollution control device, an education program or pollution source control.

When designing a pollution prevention program it is important to preserve existing valuable elements of the natural drainage system. It is also better to manage the quality and quantity of stormwater at the source. Preventing pollution at source can be achieved through on-site source control and community education programs. The installation of stormwater treatment devices such as Gross Pollution Traps (GPT) and Constructed Wetlands (See Table 7.1) are end-of-pipe solutions.

On-site Source Control

The best way of protecting local waterways from stormwater pollution is to prevent pollution at source. Careful planning will enable pollution to be prevented. The following steps can be taken to improve environmental performance:

Transport of materials ~ The risk of stormwater pollution is high during the transport of materials on and off a site. All delivery and dispatch areas should be bunded to ensure that no pollutants can escape to stormwater if an accidental spill occurs.

On-site storage of chemicals and wastes ~Chemicals and wastes need to be stored away from stormwater drains in clearly marked and sealed containers. The storage area needs to be under cover and securely bunded.

Cleaning Practices ~ Outdoor areas should be swept and kept clean of rubbish. It is illegal to hose off surfaces into the stormwater.

Be Prepared for Accidents ~ Plan what to do in the event of an accidental spill. Spill clean-up equipment should be kept on site and close to potential risk areas.

Community Education

Community education is one of the key strategies for preventing pollution at source and involving the people of NSW in actions to protect the environment.

A community that understands the major environmental issues confronting them at home, in the workplace and in the broader community will be more able to make the changes required to achieve improvements in environmental quality.

When planning a community education project, it is important to consider the following questions:

What problem is being targeted?
Who is affected by this problem? (Who are the stakeholders?)
Who is the target group for the project?
What do you want the project to achieve? (outcomes)
How are you going to achieve this?
What kind of support is needed?
What are the steps that need to be taken to achieve the desired outcome? (develop an action plan)
How will you know the project has achieved what you want it to? (monitoring and evaluation)

Useful Community Education Methods ~ The best methods for a community education project will depend on the target group. Some useful techniques include:

audio visual tools (video, slides, photos)
awards
case studies of positive role models
debate
demonstration
displays
focus groups
media coverage
talks, workshops
print material such as posters and brochures

Students may like to conduct a survey to find out the most useful or preferred techniques for their target group. They will also need to plan how they could conduct the education program.

Stormwater Treatment Devices

Stormwater treatment devices reduce the pollution load entering a waterway by trapping gross pollutants such as litter, leaves and sediment (eg Gross Pollutant Trap - Figures 7.1, 7.2). They can also slow the flow of a waterway and absorb excess nutrients (e.g. Constructed Wetlands - Figures 7.3, 7.4).

The following ideas need to be put into practice when designing stormwater treatment devices.

Define site-specific objectives and take these into account for optimum performance of the device.
Define existing conditions at the site and in downstream receiving waters.
Consult with landscape architects to landscape the site. Think about the habitat potential.
Develop final design parameters and evaluate the design.
Develop operations, maintenance and monitoring plans.
Consider the safety issues involved and include warning signs and fences where necessary.


Figure 7.1 - Gross Pollution Trap (GPT)	Figure 7.2 - GPT side view


Figure 7.3 - Constructed wetlands	Figure 7.4 - Constructed wetlands, side view
Source Figure 7.2 and 7.4 - Managing Urban Stormwater - Treatment Techniques NSW EPA, 1997 Source Figure 7.1 and 7.3 - Department of Planning,

Table 7.1: Stormwater Treatment Devices

Provides information about the characteristics of different stormwater treatment devices that can be used for "end-of-pipe" approaches to stormwater pollution prevention.

Treatment Device	Description	Advantages	Limitations	Costs
Treatment Device	Description	Advantages	Limitations	Installation	Maintenance
Litter Basket	A wire or plastic `basket' installed in a stormwater pit	Collects litter at a single location Useful in high litter areas e.g. shopping centres, schools Can be placed in existing drains	Can cause flooding if blocked Potential smells and health hazard Can overflow Does not trap pathogens, nutrients or sediment Barely trap oil or grease	Low	High
Litter Rack	A series of metal bars across a channel	Usually used as part of a gross pollutant trap Collects litter at a single location Can be placed in existing drains	Can cause upstream flooding Litter may wash upstream if tidal Can be ugly Potential for odour and health risk Can overflow Does not trap pathogens, nutrients or sediment Barely trap oil or grease	Low	High
Litter Boom	Floating booms with mesh skirt placed in a channel	Removes floating rubbish Improves downstream appearance Mobile Can be placed in existing drains	Litter can get under the boom in flood Can be damaged by large litter, e.g. Logs Litter can blow over the boom Easy potential for vandalism Often accessible only by boat Trap only litter	Low	High
Catch Basins	Stormwater pit with a lower base to collect sediment	May be used upstream Can be fitted into existing channel Below ground therefore unobtrusive	Needs regular cleaning Traps sediment and litter but not pathogens, oil and grease	Low	High
Water Quality Inlet	Three underground retention chambers designed to remove coarse sediment and oils	best suited to small catchments with potential for oil pollution e.g. car parks, petrol stations below ground therefore unobtrusive	Fine sediment and soluble material not trapped High flow periods can cause remobilisation of trapped material Trapped sediment may be high in heavy metals, nutrients and other toxic chemicals	Moderate	High
Filter Strips (Buffer zones)	Grassed or vegetated strip adjacent to water course.	Can reduce run-off volume Trap pollutants by binding to organic matter and soil particles Effective at removing most types of pollutant Can be used to pre-treat run-off prior to other stormwater devices Visually attractive Increases available habitat	May require large area of land Slopes must be less than 5 degrees High failure rate due to poor maintenance, sparse vegetation cover and erosion channels Only suited to shallow "sheet" flow	Low	Low
Grass Swales	Open grass lined channels often with check dams, for conveying runoff from roads and other impervious surfaces.	Can reduce runoff velocity Remove coarse particulates Cost effective Can be used to pre-treat runoff More visually attractive than kerb and guttering	Requires greater area of land than kerb and guttering. Can be damaged by regular parking of cars Swales need to be well vegetated before carrying runoff If not maintained well problem such as mosquitoes, weed infestations and erosion may arise	Low	Low
Sediment Traps	Structures trap coarse sediment. They can be in the form of a tank or pond.	Trap coarse sediments upstream of a treatment measure such as a wet basin or constructed wetland Reduced coarse sediment loads to stormwater systems or receiving waters Can be installed underground	Limited removal of fine sediment or soluble pollutants Above ground sediment traps can be visually unattractive	Moderate	Moderate
Gross Pollutant Traps	A sediment trap with a litter rack, usually located at the downstream end of the GPT.	Trap coarse sediments before they can enter a wetland, pond or other stormwater treatment device Concentrate litter at a single location ready for easy removal Feasible for catchments larger the 8 ha Appropriate for retrofitting	Limited removal of fine sediments Potential to increase upstream flooding if trash rack becomes blocked by debris Visually unattractive Potential odours and health risks to workers when handling trash When the rack is full debris can be remobilised Can be a barrier to fauna migration	Moderate	Moderate - High
Extended Detention Basin	A series of channels and ponds which can store runoff for 1-2 days	Can be used to trap coarse sediment Can be used as a sports field when dry Reduces erosive floods downstream. Most practical for catchments over 8 ha Doesn't require top ups in dry areas which wet basins may require	Limited removal of fine sediments Potential safety hazard due to intermittent nature of flooding Nuisances of mosquitoes and odours Large amount of land needed May be a barrier to fauna migration	Low - Moderate	Low - Moderate
Wet Basin	A structure similar to a small lake or dam with a permanent and relatively deep body of water	Generally applicable for catchments larger than 5 ha Can be retrofitted within dry basins. Potential for integrating stormwater reuse into the design Potentially high habitat, aesthetic and recreational value Can be used at steeper sites than constructed wetlands	Cannot be placed on unstable slopes May cause habitat degradation upstream and downstream of the pond Potential for odours, debris, mosquitoes May be a barrier to fauna migration May aggravate upstream flooding if blockage occurs at the inlet or outlet Possible adverse impact on downstream water quality	High	Moderate
Constructed Wetlands	A shallow water body with a large proportion of its water surface covered by macrophytes	Can provide habitats, recreational areas and be used in community education programs Visually attractive Useful for catchments larger than 8 ha Can fit into existing urban areas where space is available	Cannot be placed on steep or unstable slopes Wetlands generally need a reliable source of water to remain wet all year round Stream weir structures may require fishways to provide fish passages May contribute to groundwater pollution May impact on public safety from a physical, chemical or biological perspective	Moderate - High	Moderate
Infiltration Trenches	A shallow excavated trench filled with gravel into which runoff drains	Useful for urban catchments less than 2 ha Appropriate for permeable soils. Recharges groundwater	Cannot be places on steep slopes Runoff requires pre-treatment to avoid blockage Possible risk of groundwater contamination Unsuitable in areas prone to instability	Low	High
Infiltration Basins	Open excavated basins, which incorporate groundwater, recharge concepts into their design	Appropriate for areas with high permeability soils Recharges groundwater Reduces run-off rates and volumes, reducing downstream channel erosion	Large land consumption High failure rates have been reported Possible risk of groundwater contamination Potential for mosquito breeding and boggy base of basin May exacerbate flooding if basin becomes blocked Can suffer from hydraulic overload due to catchment flows exceeding infiltration capacity	Low	High
Sand Filters	A bed of sand overlying a subsoil drainage system	Applicable for catchments <2 ha Good for groundwater protection Well suited to retrofitting Can be used to treat outflows from a wet basin or constructed wetland	Require pre-treatment to remove litter and coarse sediment High head loss and relatively low flow Easily clogged, needs regular maintenance Can aggravate upstream flooding if blocked and cause odour problems Large sand filters with no grass cover are visually unattractive	Low - Moderate	Moderate - High