Alkimos Strategic Ocean Outlet Monitoring (ASOOM)

Background

In November 2007, the Water Corporation received Ministerial approval to construct and operate a wastewater treatment plant (WWTP) at Alkimos. The WWTP is situated on the Alkimos-Eglinton dunal system, on the coast between Yanchep and Quinns approximately 40km north of Perth, Western Australia. The Alkimos WWTP will receive and treat domestic wastewater Perth’s north-western urban corridor—which has grown rapidly over the last few years.

Secondary treated wastewater (TWW) will be carried offshore via a pipe of dimensions 1.0-1.2m in diameter. The TWW will be discharged 3.7 km offshore into the water 20m below the water surface.

The Water Corporation acknowledges that the secondary TWW will contain concentrations of nutrients, metals, herbicides, pesticides and organic particulates that are higher than those found in seawater naturally.

To avoid the potential for negative effects on marine communities, the Water Corporation has committed to a comprehensive environmental monitoring programme (ASOOM). Each of the monitoring components has a different set of environmental management triggers. All of the triggers were developed in consultation with the Office of the Environmental Protection Authority.

The approach involves comparing the results of the surveys with two types of triggers, which requires further investigation and/or management (depending on the level of the exceedance). The first trigger is an Environmental Quality Guideline (EQG). Exceedance of the EQG requires further investigation against the Environmental Quality Standard (EQS). If the EQS is exceeded, then management is required to restore the health of the environment. Any exceedance of the EQG or EQS is required to be reported to the regulatory authorities within one working day of discovering the exceedance.

Details of the ASOOM marine monitoring program are included below.


Marine Monitoring Programme

Treated wastewater characterisation

Comprehensive analysis of TWW, incorporating over 100 analytes, is undertaken annually to determine the concentration of metals, organics, nutrients and bacteria contained within the wastewater stream. Further testing for a smaller sub-set of analytes is undertaken seasonally. The concentration of analytes is then compared against the national ANZECC/ARMCANZ (2000) guidelines for contaminants. This provides a comprehensive cross-check of potential contaminants with the national guidelines, which ensures human health and marine flora & fauna are protected.

Initial dilution calculations

Initial dilution modelling is used to determine the extent of TWW dilution around the ocean outlet under calm (worst case for dilution) sea conditions. The initial dilution modelling is undertaken annually during summer. These data are used to ensure all contaminants contained within the TWW meet the national guidelines for protection of marine species following the initial dilution stage—which is typically complete within meters of the diffuser.

Whole-of-effluent toxicity (WET) testing

Ministerial Conditions require that whole-of-effluent toxicity (WET) testing is undertaken as part of the Alkimos monitoring programme. WET testing involves exposing organisms to different concentrations of TWW effluent and then measuring the growth or reproductive capability after a selected period of time. All tests, where required, are undertaken in the laboratory with the appropriate animal ethics approval.

Results of WET testing to date have indicated that the dilution of treated water (between the outlet diffuser and the surface of the water column) is sufficient to reduce contaminant concentrations to levels well below ANZECC/ARMCANZ (2000) guideline trigger levels.

Water quality compliance monitoring

The concentration of nutrients (ammonia, nitrite & nitrate, ortho-phosphate) and chlorophyll a is monitored at a number of locations, including: adjacent to the ocean outlet, at increasing distances downstream of the outlet and at appropriate reference sites (located so as to be representative of surrounding conditions, beyond the influence of the plume).

Water quality monitoring enables scientists to clarify the effect of TWW on the biological components (i.e. microalgae and seaweed communities) of the ecosystem over the summer period. Summer is specifically targeted as this is when the effects of nutrients are more likely to be detectable. This has the added advantage of enhancing the sensitivity of the program.

An additional objective of the water quality monitoring program is to ensure concentrations of bacteria do not exceed the recommended levels for primary and secondary contact recreation, and/or the guidelines for sea food consumption.

Water quality monitoring commences in the first week of summer and continues at fortnightly intervals between December and March.

Algae community monitoring

One of the novel aspects of the Alkimos monitoring program is the inclusion of sea-weed (or macroalgae) as an indicator of environmental health. The development of this program required extensive groundwork, including: towed video surveys, two base line studies conducted prior to the commencement of TWW discharge; and a comprehensive review of the scientific literature.

Baseline surveys were undertaken in February and January of 2009 and 2010 respectively. Four study locations were established: one situated in the disturbance zone immediately north of the outlet and three reference sites. Within each of the four locations, five study sites were established based on previously determined depth, algae and reef rugosity criteria. The results of the towed video surveys ensured that each of the study locations was characterised by medium and high relief reef.

Seaweed health is assessed annually in January/February by a team of marine ecologists from Oceanica. The scientists use SCUBA to measure the composition of seaweed communities and to collect samples for chemical analysis. In turn, these measures are used to determine whether the seaweeds are assimilating sewage based nitrogen and whether or not the communities have changed as a result.

The seaweed health program has adopted a two-pronged approach to environmental management. The approach involves comparing the results of the surveys with two types of triggers, which requires further investigation and/or management (depending on the level of the exceedance). The first trigger is an Environmental Quality Guideline (EQG). Exccedance of the EQG requires further investigation against the Environmental Quality Standard (EQS). If the EQS is exceeded, then management is required to restore the health of the environment. The EQG and EQS triggers are outlined below:

Environmental Quality Guideline: To exceed the EQG, there must be a significant shift in both the %N content and stable isotope of N in at least one or more of the three algae species with a requirement that at least one of the species must be Ulva sp (a sensitive species chosen for its ability to respond rapidly to nutrients).

Environmental Quality Standard: Several triggers have been developed, all of which must be exceeded simultaneously in order to exceed the EQS. The rationale was to set an appropriate EQS, that if triggered, would indicate beyond reasonable doubt that the Environmental Quality Objective for ecosystem integrity had been compromised.

Trigger 1. The EQG must be exceeded: i.e. detection of a significant increase in the concentration of tissue nitrogen (%N) and a significant shift in stable isotopes of N consistent with assimilation of sewage based N. This eliminates, to a large degree, any chance that the EQS may be exceeded as a result of natural small changes in community assemblages.

Trigger 2. A significant shift in algal community super-categories including a corresponding increase in the proportion of Ulva sp: This will involve a multivariate test for significant shifts in Impact location community assemblages relative to Reference location community assemblages - with the drivers for the shift being an increase in the proportion of Ulva sp. Drivers of the change will be teased out using post hoc tests in PERMANOVA+ (PRIMER V6). Oceanica is presently running simulations using synthesised impact data with the intention of developing an appropriately sensitive test.

Trigger 3. Temporal component: The temporal trigger will require that Triggers 1 and 2 listed above are exceeded in 3 consecutive years.

Sentinel mussel monitoring

Sedentary, filter-feeding shellfish (such as mussels), are often used as biomonitors. Filter-feeding shellfish process large amounts of water from a fixed location, and have the tendency to accumulate contaminants, where contaminants are present – including microbiological pathogens.

In water measures will be conducted at approximately fortnightly periods as part of the water quality compliance monitoring for microbiological contamination. The actual accumulation of thermo-tolerant coliforms in the flesh of the mussels will initially be conducted during the fist summer after the commencement of licensed discharge from the Alkimos ocean outlet and thereafter every 5 years, or following exceedance of a guideline.

Field sites are differentiated into two categories, (1) water quality monitoring sites where concentrations of thermo tolerant coliforms in water will be measured immediately above the seafloor, and (2) sentential mussel deployment sites located north of the ocean outlet above the nearest suitable reef. At each site, three replicates mussel lines will be deployed. Mussels will be suspended in mesh brackets 2-3 m below the surface at the height of the reefs surface.

Mussels will be deployed for approximately six weeks with cleaning of the mussels and mesh brackets three weeks after deployment to prevent fouling which could smother and kill the mussels. After the 6 week deployment period mussels are retrieved and the number of live mussels are recorded and sent to the analytical laboratory. The Water Corporation will report to the department of health if sentential mussel tissue exceeds relevant environmental and health guidelines.

Sediment quality monitoring

Concentrations of potential contaminants in sediments can provide for an effective time-integrated measurement of the distribution and accumulation of contaminants from marine TWW outlets. These measurements have particular applicability to the accumulation and/or toxicological effects of contaminants in/on benthic organisms in the vicinity of the Alkimos ocean outlet.

Environmental monitoring at Alkimos included implementing sediment surveys to determine the spatial variability in concentrations of potential wastewater contaminants in sediment sites in the vicinity of the Alkimos ocean outlet. Sediments will be collected prior to the initial discharge of effluent from Alkimos ocean outlet, and then every five years thereafter. Sediment samples will be analysed for:

  • Grain-size distribution (laser diffraction and sieving);
  • Organic matter content (loss on ignition at 550ºC);
  • Carbonate content (loss on ignition at 1000ºC);
  • Pesticides and herbicides;
  • Nutrients (TKN, TKP); and
  • Metals (aluminium [Al], arsenic [As], cadmium [Cd], cobalt [Co], copper [Cu], lead [Pb], mercury [Hg], nickel [Ni], selenium [Se], silver [Ag], zinc [Zn]).

Results from the sediment quality monitoring programme are compared against ANCECC/ARMCANZ (2000) guidelines to provide an indication of trigger levels for contaminants in sediments that may have the potential to cause ecological effects in marine communities.

ASOOM team

The ASOOM project team comprises of a multi-disciplinary group of technical staff, scientists and ecologists. Personnel from each organisation are responsible for carrying out monitoring and/or analytical tasks specific to their area of expertise.

ASOOM Program Team
InvolvementTeam MemberOrganisation
Water Corporation Project ManagerCraig ByersWater Corporation
Oceanica Project DirectorDr Karen HillmanOceanica
Project ManagerDr Glenn ShiellOceanica
Treated Wastewater CharacterisationDr Karen HillmanOceanica
Initial Dilution ModellingKellie HollowayOceanica
Water Quality MonitoringKris WienczugowMAFRL, Murdoch University
Phytoplankton MonitoringStuart HellerenDalcon Environmental
Ecotoxicity TestingDr Rick KrassoiEcotox Services Australasia
Annual ReportingDr Glenn ShiellOceanica