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

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.

Key principles of Ecological Engineering 1. It is based on the self-designing capacity of ecosystems; 2. It can be the acid test of ecological theories; 3. It relies on system approaches; 4. It conserves non-renewable energy sources; and 5. It supports biological conservation; 6. It involves the design of the natural environment through quantitative approaches that rely on basic science; 7. Primary tool is the self-designing ecosystem.

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 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).

Licence considerations Nutrient Target max mass load based on old licence (kg/yr) Release from STP to forest & wetland (mg/l) Implemented licence limits to Obi Obi Creek (mg/l)* Expected discharge concentrations from wetland (mg/l)** N P * At 925 Kl/day = 5000 EP ** For an average rainfall year, (expected concentration higher in wet years)

Indicative marginal cost of treatment

Implications of load-based licencing

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

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.

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.

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

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

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.

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.

Pump and control systems

Irrigation and wetland layout

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.

Tree Crop Technologies Level 14, 97 Creek Street Brisbane QLD 4000 Tel:

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