Nature-Based Water Treatment: Integrating Forest and Wetland Systems for Sustainable Effluent Reuse
Services: Construction, ongoing maintenance and advisory services
Location: Maleny, Queensland
Date: 2010-2023
Early-stage site preparation
Our Scope
Unitywater sought an innovative, sustainable, and community-aligned solution for the beneficial reuse of A-grade effluent from the Maleny Sewage Treatment Plant (STP), located just 10 km upstream of a major drinking water supply dam. A-grade effluent is treated to the highest standard and is safe for a range of non-potable uses, however, residual nutrient loads remained a concern due to the sensitive downstream environment.
Rather than pursuing a conventional advanced treatment facility—an option associated with significant financial and environmental cost—Unitywater partnered with Verterra to deliver an award-winning, nature-based solution. The approach used a constructed rainforest and wetland system to complete final-stage nutrient removal, while also delivering lasting environmental and community benefits.
Challenges
Residual nutrient load in treated effluent that would be costly to remove through engineered water treatment
Proximity to sensitive environmental assets, including Obi Obi Creek and a major drinking water supply dam
Need for cost-effective, low-maintenance, long-term solution that delivered both environmental and community value
Integration of natural and engineered elements, requiring expertise in both wastewater management and ecosystem establishment
Requirement for a safe and sustainable asset management plan to guide operation over a multi-year horizon
Verterra’s Solution
Verterra worked with Unitywater to construct and maintain an ecosystem-based water treatment solution combining an irrigated rainforest and a three-cell constructed wetland.
Design & Construction
Irrigated forest planted across 13.7 ha, with over 100 canopy and understory species (up to 2,500 stems/ha), surrounded by unirrigated buffer and gully zones
A-grade effluent treated via distribution through a purpose-built irrigation network and weather-responsive control systems
Constructed wetland designed as a final filtration stage before water enters Obi Obi Creek
Infrastructure included pumps, soil moisture sensors, weather stations, and extensive revegetation works including landslip remediation and exotic species removal
Community integration through public walkways and recreational access
Ongoing Maintenance & Advisory
A comprehensive 5-year site maintenance plan for Unitywater covering:
Forest and wetland vegetation
Irrigation infrastructure
Wetland flow and filtration systems
Supported ongoing consulting, monitoring, and adaptive management with an emphasis on zero harm, sustainability, and ecosystem function
Maleny constructed wetland, 2018
Project Highlights
Developed a natural system to treat up to 925kL of effluent per day
Converted 18.9 ha of land into a functioning rainforest ecosystem
Delivered a multi-functional landscape: wastewater treatment, biodiversity habitat, and public recreation
Winner of the UN World Environment Day Business Award for Best Specific Environmental Initiative (2015)
Outcomes
Environmental compliance: Achieved nutrient removal targets without adverse impacts to downstream waterways
Cost efficiency: Avoided the need for expensive engineered treatment systems by leveraging ecological processes
Appreciating community asset: Unlike conventional infrastructure, the irrigated forest and wetland improve in value and utility over time
Public and stakeholder support: Delivered visible, accessible green space that benefits both environment and community
Sustainable asset management: Maintenance plan ensures long-term functionality and resilience of the system
Maleny Forest, 2018