Containment of recycled wastewater is an essential part of its safe management. Environmental legislation imposes strict requirements on the water industry to ensure systems are designed and operated to minimise potential for adverse social and environmental impact. PBJ & Associates is experienced in assessing systems to ensure they comply with these requirements, including the development of options for upgrading.
The State Environment Protection Plan and the EPA reclaimed water guidelines requires all reclaimed water infrastructure to be designed and constructed to contain all wastes in at least the 90th percentile wet year. Usually, discharge to a waterway is only permitted by the EPA licence during particularly wet years when excess wastewater cannot be disposed of to land.
Our Approach
We have developed a methodology to assess compliance with these requirements using a statistical model. We create a water balance model for the system which considers all the inputs and outputs.
The water balance model requires long-term rainfall and evaporation data which can be obtained from the Bureau of Meteorology. A long-term treatment plant inflow record is generated using the relationship between catchment wetness, rainfall and observed inflows.
Irrigation demands are calculated using climate data, crop factors and farming practices. Seepage from the treatment plant and storages are estimated from knowledge of asset condition.
The water balance model outputs include winter storage levels and the timing and volume of overflows from the storage. This can be used to assess compliance with the containment requirements.
The water balance model may be constructed using REALM, a water supply system simulation package which was developed for the Department of Sustainability and Environment (DSE). REALM incorporates a module to determine irrigation demands, making it ideal for this application.
Options Assessment
The model can also be used to assess the options for upgrading an existing system to comply with the legislation. Options such as inflow management, increasing storage and irrigation areas or changing customer demands for recycled water can be quickly and easily assessed.
Your Business Needs
PBJ & Associates is experienced in the assessment of wastewater systems. Containment is a key driver for all wastewater management activities and we can assist with the analysis and management of your systems to meet regulatory requirements.