96. Net-Zero Non-Potable Water Strategy: On-Site Storm and Wastewater Treatment
As human population and industry have grown, so have demands on natural resources making water supply and water pollution issues one of the most critical environmental concerns for this generation. Although treatment methods have improved, the standard model of collect-treat-discharge for wastewater has not changed in over 100 years. From a sustainability perspective, this status quo method for dealing with our ever-growing water problems cannot endure. The nation’s aging wastewater management systems discharge billions of gallons of untreated sewage in U.S. surface waters each year, disturbing aquatic habitats. As our population grows, the facilities that treat this water will expand, intruding into natural areas. And, 99% of potable water is over treated, contributing to a carbon footprint that is approximately 20% of national stationary energy use.
A tremendous breakthrough can happen when considering both the water use and wastewater side of the equation. Maximizing water conservation will require on-site sourcing of recovered and recycled wastewater for non-potable uses. This highly implementable and scalable solution can be accomplished while reducing carbon footprint, creating habitat, providing a superior user experience, and providing an educational opportunity. Google is proposing a net-zero water strategy at its Bayview Campus that has these very ambitious, but attainable goals. The key to the goal of reducing potable water usage is onsite wastewater treatment which will utilize site-collected rainwater and treated wastewater effluent to meet the demands of toilet flushing, cooling tower make-up, and landscape irrigation. Typically, these needs are met by using potable water transported 170 miles to the City of Mountain View. Approximately 99% of this water is not used for drinking and does not need the same level of treatment. This project will reduce the distance from source to point to less than ¼ mile, and treat it to the level appropriate for its use, reducing the energy required for non-potable water uses. Additionally, potable water usage will be reduced by 60% and 100% of the non-potable water demand will be met with site resources through this ambitious recycling system. Wetlands play a major role in the Bayview on-site water infrastructure strategy. There are two non-potable water sources that combine to offset all compatible demands: storm water collected from the site and stored in seasonal wetland ponds, and wastewater that is treated using constructed subsurface wetland filtration. These wetland systems blur the line between developed and natural conditions and embrace the environment in which the campus is located. Rainwater and treated wastewater are blended to optimize water quality and match seasonal demands. Each of these applications uses natural ecosystem performance to provide water management benefits that support the natural patterns of nature and are ecologically restorative. Bay Area native wetland plants are planned as an integrated landscape element, to provide an extension of adjacent ecological opportunity. Paths, bridges, and educational signage provide direct opportunity for campus users to understand the connection between human and ecological processes in a way that highlights that connection experientially, rather than hiding it in a pipe or mechanical room. Creating a system that is sustainable must also include fiscal responsibility and resiliency. The water use reduction program developed for Bay View will drive the system payback with attractive total cost of ownership. Not only financially beneficial to the owners, but on-site wastewater treatment and Net-Zero water strategies will benefit the municipality by putting less stress on the existing system. Ultimately though, resiliency is critical with the goal of being self-sustaining. Google has developed a system with adaptable components that can provide grid independence that is easily scalable from an individual project level to an Eco-District scale capable of providing a continual, reliable supply of non-potable water. The technology that makes this possible is even scalable to a larger city-wide system where “satellite” or private infrastructure, like Bayview, can actually take pressure off of the city system on an as-needed basis if properly sized. Similar to private electricity generation that is put into the grid, a series of water treatment facilities connected to the larger system would divert waste from city infrastructure for local treatment adding extra capacity to the system by distribution of the treatment. These satellite systems then provide a source of non-potable water which will take pressure off of the potable water delivery systems. This idea could shift the current strategy of sending ALL water through a Collect-Disinfect-Store-Deliver-Use-Collect-Treat-Release to a local, even site-by-site approach. Diverting increasing amounts of non-potable water use to a localized Collect-Treat-Blend-Deliver-Use-Repeat model will give us a more sustainable and future-proof infrastructure system as water sources become more constrained. Laying the groundwork for these systems before our water sources become critically constrained is paramount.
Why it should be recognized:
Of the thousands of ideas available to create a more sustainable planet, sometimes going back to a simple natural system is optimal. On-site treatment of wastewater for non-potable uses is a low tech, highly implementable, and scalable idea that can have a huge positive effect on the environment and aging municipal infrastructure. Through the creation of habitat and educational opportunities, we can simultaneously help to eliminate some of the billions of gallons of untreated sewage that is discharged into our national waterways, reduce potable water usage considerably and reduce unnecessary energy consumption.
Submitted: Jan 31, 2013
Author: Catherine MINOR
  • Resource/Waste Management (Regional)