Technologies, such as composting toilets, gray-water reuse and on-site treatment of wastewater for beneficial reuse have been proposed as best practices for treating and reclaiming water and waste, says the 145-page report of the $125,000 study, funded by the Russell Family Foundation.
“However, regulatory obstacles, cultural fears and a lack of information have largely prohibited their uses in all but a few ‘demonstration’ projects,” the report says.
In places, decentralized treatment and net-zero water use, under which a building or a site operates within the water budget available rather than using utility water, is outright illegal, said Spataro.
The research, carried out with the civil firm 2020 Engineering, Bellingham, Wash., and green product developer Ecoform, Knoxville, Tenn., presents life-cycle analysis comparisons regarding environmental impact for passive systems, such as composting toilets and gravity-fed wetland treatment systems, and more energy-intensive systems, such as recirculating biofilters and membrane bioreactors. The results are separated into two sections: environmental impact associated with conveyance and those related to treatment.
The report concludes that the lower-energy systems, among them composting toilets and constructed treatment wetlands, have fewer negative environmental impacts compared with a baseline centralized system, while the more energy-intensive decentralized treatment systems, including biofilter and bioreactors, have substantially greater negative impacts.
Conveyance gets a big black mark. “Operating energy associated with pressuring and pumping waste far outweighs the impacts associated with the material and excavation components of the systems,” says the report.
Pumping wastewater to its point of treatment represents a significant portion of the overall negative environmental impact. But as population density increases, negative environmental impacts associated with conveyance decrease.
The report says further research is needed to evaluate, among other things, the water reuse potential of decentralized systems and to apply the findings broadly to communities at different scales.
A policymaking guide is in the works, funded by a $15,000 grant from the Sustainable Path Foundation. “We are building the case for resilient water systems,” said Spataro.