Centralising wastewater treatment can restrict options for effluent reuse due to the challenges of re-directing large volumes of reclaimed water back into a serviced area. Decentralization fosters local reuse of reclaimed effluent. Increasingly, communities are committing to improve their water balance by reusing wastewater effluent for urban, agricultural, industrial, recreational and environmental uses including replenishment of aquifers.
This project reviewed different residential and industrial wastewater treatment systems, identifying potential uses for the resulting effluent as well as the volume that can be processed. A selection criteria matrix was developed addressing potential usage of the output effluent, the volume handled, space requirements, maintainability, and energy demands.
It is useful to consider technologies within the categories of Now, New and Next: ‘Now’ systems are currently available; ‘New’ systems are at pilot stage; and ‘Next’ systems are in the research phase or at laboratory scale.
‘Now’ technologies for recovery of wastewater include
- green filters
- biological filters
- catalytic wet air oxidation
- electrocoagulation and photolysis.
‘New’ strategies include
- membrane filtration systems
- psychrophilic anaerobic digestion
- aerobic granular biomass.
Looking further ahead, ‘Next’ strategies include
- hydrodynamic separation
- algae ecosystems.
Agricultural uses of recovered wastewater include irrigation of crops and pasture land.
Environmental applications include recharge of aquifers, irrigation of wooded and green areas, and maintenance of water bodies.
Urban uses encompass, for example, irrigation of gardens and parks, street cleaning, firefighting supplies and industrial washing vehicles.
Industrial applications include water for processing and cleaning, cooling towers and evaporative condensers.
Recreational uses include ponds, water bodies (not used for swimming) and ornamental streams and irrigation of golf courses.
This project developed new guidance for selecting wastewater treatment systems suited to the opportunities and resources available, taking full account of the potential local uses of the quantity and also the quality of the effluent that can be reclaimed.