Coastal water quality, Adelaide's port waterways

Current or emerging issues paper
Australian Government Department of the Environment and Heritage and South Australian Environment Protection Authority
prepared for the 2006 Australian State of the Environment Committee, 2006

This document was commissioned for the 2006 Australian State of the Environment Committee. This and other commissioned documents support the Committee's Report but are not part of it.

Contents

PDF file

Citation

Department of the Environment and Heritage and South Australian Environment Protection Authority 2006, 'Coastal water quality, Adelaide's port waterways' paper prepared for the 2006 Australian State of the Environment Committee, Department of the Environment and Heritage, Canberra,


Background

Adelaide's Port waterways comprise the Barker Inlet and the Port River Estuary. The Barker Inlet is a nationally significant wetland, and both waterways are important to Adelaide residents for recreational and scenic values. A Dolphin Sanctuary has been proclaimed in these waterways.

Historically, a range of pollutants has been discharged to the waterways, although nutrients (nitrogen and phosphorus) are of most concern, being associated with the loss of seagrass and mangroves. Elevated nutrient levels are causing seasonal growths of macroalgae (sea lettuce) and toxic algal blooms such as 'red tides' (dinoflaggelate blooms).

There have been considerable efforts to reduce pollutant discharges to the waterways over the past ten years, including the closure and upgrade of polluting industries. These include the relocation of a treated sewage discharge from the inner Port River - part of the Port waterways - to the upgraded Bolivar Wastewater Treatment Plant (WWTP).

Current efforts

With support from the Natural Heritage Trust's Coastal Catchments Initiative, the South Australian Environment Protection Authority (SAEPA) is developing a Water Quality Improvement Plan (WQIP) to reduce nutrient discharges to these waterways.  An assessment of all inputs to the waterway has confirmed that two point sources, Penrice Soda Products and the Bolivar WWTP, account for most of the nutrient inputs (see table 1).

Table 1: Current and proposed loads for nutrient sources to the Port Waterways
Pollutant Source Current load
(t/yr)
Target load for 2015
(t/yr)
Required load reduction
N P N P N P
Industrial point sources
Penrice Soda Products
Bolivar WWTP (SA Water)

820
596

0.7
248

200
100

0.7
40

-76%
-83%

0%
-84%
Total point sources 1416 249 300 41 -79% -84%
Land based diffuse sources
Groundwater
Atmospheric deposition
Local stormwater discharges
Catchment Discharges:
 – Dry Creek
 – Barker Wetlands
 – Little Para
 – Range & Magazine Wetlands
 – Helps Road Drain

10
32
2

34
7
6.1
2.5
nd

0.25
2
0.2

8.5
3
1.4
1
nd

10
32
2

34
7
6.1
2.5
nd

0.25
2
0.2

8.5
3
1.4
1
nd

0%
0%
0%

0%
0%
0%
0%
0%

0%
0%
0%

0%
0%
0%
0%
0%
Marine sources
West Lakes outfall
Internal loading (sediments)

52
100

11
10

52
100

11
10

0%
0%

0%
0%
Total current and targetloads 1662 286 546 78 -67% -73%

Note: N = nitrogen, P = phosphorus

Source: South Australian EPA Draft Water Quality Improvement Plan for Adelaide's Port Waterways.

Comprehensive water quality modelling has quantified the load reductions needed to prevent the impacts of these point source discharges, and has identified reductions in the order of 80 per cent are required from these sources. At this time reductions from other sources, such as land-based or marine sources, are considered cost-ineffective or impractical.

Improvement projects

The SAEPA is negotiating with Penrice Soda Products and SA Water to develop plans to reduce nutrient discharges from their plants. The complexity of this process and the time needed to develop and implement reductions from these sources is considerable, however at this time:

  • SA Water is developing improvement projects for its Bolivar WWTP as part of an overall strategy for all Adelaide metropolitan wastewater treatment plants. They are committed to their plants not causing environmental harm and are exploring interim actions to reduce their environmental impacts while the capital works program is being developed. Wastewater re-use is an option that has a number of other benefits for the Adelaide community and the potential for this is being explored with the Natural Resource Management Boards; and
  • Penrice Soda Products has committed to reduce its nitrogen discharge to 575 tonnes by 2010. They have agreed that this target should be enforced through their discharge licence with the SAEPA. They have also agreed to aim to reduce their discharge to 200 tonnes of nitrogen by 2015, although cost-effective technology to allow this is not yet available. In the meantime they will maintain an active role in seeking to adapt emerging nitrogen reduction technologies to their process and pursuing incremental reductions of nitrogen discharge from the site.

These commitments ensure that at least an 18 per cent reduction in nitrogen discharges will be achieved during the five-year period of the Water Quality Improvement Plan. Though unquantified at this stage, greater reductions will be achieved implementing the capital works program being developed for the Bolivar WWTP in the future.