Ecological Engineering - Maleny Effluent Irrigated Rainforest and Wetland

1. Irrigation Australia Conference 2-6 June 2014 Ecological Engineering - Maleny Effluent Irrigated Rainforest and Wetland

2. Ecological Engineering Defined as: • The design of sustainable ecosystems that integrate human society with its natural environment for the benefit of both. Ecological Engineering involves: • The development of new sustainable ecosystems that have both human and ecological value. Spawned by: • Realisation that not all pollution problems can be solved through technological means; and • Realization that with technological means, pollutants are just being moved from one form to another.

3. Key principles of Ecological Engineering • It is based on the self-designing capacity of ecosystems; • It can be the acid test of ecological theories; • It relies on system approaches; • It conserves non-renewable energy sources; and • It supports biological conservation; • It involves the design of the natural environment through quantitative approaches that rely on basic science; • Primary tool is the self-designing ecosystem.

4. The challenge • Pre-existing Maleny STP (designed for 2000 EP) was operating beyond its hydraulic and biological capacity. • Infrastructure was at the end of its serviceable life. • Maleny is located in the headwaters of Obi Obi Creek, approximately 10 km upstream of Baroon pocket Dam (i.e. within the water supply catchment). • Maleny population forecast to grow to 5000 EP (185 L/EP/d average dry weather flow) by 2026. • With no change to treatment systems, nutrient loads to surface waters will more than double. • The marginal cost of an engineered system to remove residual nutrients from the Maleny STP is high (diminishing returns).

5. Licence considerations * At 925 Kl/day = 5000 EP ** For an average rainfall year, (expected concentration higher in wet years)

6. Indicative marginal cost of treatment

7. Implications of load-based licencing

8. Proximity to water supply dam Baroon Pocket Dam Effluent irrigation site

9. Objectives • To provide a safe, environmentally and financially sustainable method of releasing treated water back to the environment. • Water discharged to the environment should have no negative impact on the water quality of Obi Obi Creek. • Zero harm, both during construction and ongoing operation. • Whole of life project cost is minimised.

10. The solution • Construction of a MBR treatment plant producing “Class A” effluent • Irrigation of a constructed rainforest and wetland system. • “Treatment” via the forest and wetland system to remove 70% of residual N and P and achieve residual nutrient loads of: • 0.9 mg/l N (in an average rainfall year at the design horizon); • 0.07 mg/l P (in an average rainfall year at the design horizon); • Irrigation to forest to remove N, reduce P and utlise water. • Lateral seepage though the soil profile to remove P. • Passage through a wetland system to further remove N, equilibrate the water with natural aquatic ecosystem conditions, and manage high flows. • Final discharge to Obi Obi Creek.

11. Key design approaches • Forest water use and deep drainage – Tchobanoglous & HYRDRUS 1D modelling • Soil phosphorous absorption - Langmuir isotherm • Wetland N and P removal – MUSIC modelling, Kadlec and Wallace Model • Seepage and ET correction - Muskingum-Cunge

12. Treatment process flow Forest N = Uptake P = Uptake E = Transpiration Soil N = Transmission P = Sorption E = Evap/Drainage 0-1 ADWF Flow rate STP N = 5-10 mg/l P = 1-2 mg/l E = 925 Kl/day Wetland N = Metabolism P = Sediment E = Transp/Evap 1-3 ADWF 3-5 ADWF Baroon Pocket Dam Obi Obi Creek N = 0.9 – 2.2 mg/l P = 0.07-0.43 mg/l E = <365 Kl/day

13. Overview of irrigated forest & wetland system • Designed to treat 925kL of effluent per day • Established within the Maleny Community Precinct on ex grazing pasture land. • Irrigated forest area of 13.7 hectares with 6 ha of unirrigated buffer. • Palette of over 100 canopy and understory rainforest species established at a stocking of up to 2500 stems/ha. • Wetland system of 3 ha to manage high flows.

14. System features • A 45 kW 3 phase pump and control system. • Over 25,100 metres of mainline, sub-mains and lateral irrigation pipe (225mm to 16mm). • Over 2,500 pop up sprinklers. • Irrigation of up to 925kL/day over 10 hours. • Autonomous operation 8:00pm to 6:00 am. • Feedback control from weather and soil moisture sensors. • 2,500 mixed rainforest seedlings per irrigated hectare and associated dry buffer plantings. • Extension of the existing walking track system. • Land slip restoration, stabilisation and construction of gully check dams. • Practical completion March 2014.

15. Pump and control systems

17. Irrigation and wetland layout

18. Forest and wetland “treatment system” co-benefits • Community recreational facility; • Enhance biodiversity by providing habitat linking remnant vegetation; • Provide floodwater attenuation, energy dissipation and erosion control; • Improve visual amenity; • Sequester carbon; • Landslip remediation; • Improve water quality (reduced sediment) • Low operating and maintenance costs; • Appreciating community asset with economic, environmental and community benefits.

19. Tree Crop Technologies Level 14, 97 Creek Street • Brisbane QLD 4000 • Tel: 07 3221 1102 www.treecroptech.com.au

20. Topic Summary Topic:  Ecological Engineering - Maleny Effluent Irrigated Rainforest and Wetland Abstract:  The marginal cost of removing nutrients from sewage effluent increases significantly as the required nutrient concentration falls, but even at low concentrations, total discharged nutrient loads may be significant.  Unitywater’s Maleny Irrigated Forest and Wetland presents an innovative solution.  This “ecological engineering” based approach is designed to remove 70% of residual nitrogen from treated sewage effluent to achieve total nitrogen values <1mg/l.  The forest will double as a community recreational facility, enhance biodiversity by providing habitat linking remnant vegetation, provide floodwater attenuation, energy dissipation and erosion control and improve visual amenity, with low operating and maintenance costs.  Significantly, the forest and wetland “treatment system” represents an appreciating community asset with economic, environmental and community benefits. Presenter: Dr Glenn Dale, Managing Director, Tree Crop Technologies Pty Ltd