SUSTAINABLE WATER TREATMENT FOR BUILDINGS
BENEFITS TO BUILDINGS
- Affordable, tertiary treatment to reuse standards
- Scales well – single commercial building / building complex / apartment buildings
- Phases well – for multi-unit development centers, build as-you-go, lower up front infrastructure cost - compare to MBR
- Landscape amenity – attractive, silent, odor-free
- Little to no energy use
- Minimal maintenance and license / certification requirements
- Robust: designed to operate in extreme climates
– harnessing nature to purify and reuse a precious resource
– tertiary treatment with attractive landscape amenities (either subsurface wetlands or customized wetland blocks for indoor/outdoor use)
Vertical Shaft Bioreactors
– high volume treatment of biosolids and wastewater to tertiary levels
Advanced recirculating gravel filter systems
– high-performance biofiltration, maximum water reuse (especially useful in arid environments)
WASTEWATER – minimizing "waste", maximizing "water"
The average person in the United States uses anywhere from 80-100 gallons of water per day. Of that 80-100 gallons, the largest single contributor is 1.6 gallons of fresh water that get "sent away" (and deemed "wasted") everytime we flush the toilet. With rising awareness about waning freshwater resources, best development practices focusing on green and sustainability are calling into question the conventional sewer hookups and septic disposal fields that treat water as “waste”. As an alternative, onsite treatment offers a cost-effective way to recapture all of the water used in a home and reuse it for irrigation. Sustainable homes and developments are taking their cue from green standards like LEED and the Living Building Challenge which encourage or even mandate that projects treat and reuse their water on site. Whole Water Systems offers two residential-scale onsite tertiary treatment and reclamation options. For a typical residential application, a CRUCIBLE CWS (constructed wetland subsurface) can be designed into the surrounding landscape such that one would not be aware of its existence. For circumstances where maximum reclamation is required (more arid environments/water shortage areas), a RFB offers tertiary level treatment of wastewater effluent, reusable for subsurface irrigation.
more info about CWB / RFB
What is so bad about conventional Sewage systems?
The goal of conventional sewage treatment is to treat waste effluent to a dischargeable level, a level which will prevent environmental pollution. The process involves transporting large volumes of waste streams through underground pipes to a central treatment plant, concentrating the wastewater, and treating it through physical, chemical, and biological methods to remove contaminants.
Don't see any problem with this? Consider...
ENERGY - nearly 4% of the nations electricity goes towards transfer of wastewater and the treatment process undergone.*
ENVIRONMENTAL CONTAMINATION - any plumber knows that pipes leak (especially underground pipes), at least they will if they don't already. EPA estimates that in Seattle and King County, each year 1.94 billion gallons of untreated sewage and polluted runoff are discharged into Puget Sound and it's tributary waters from combined sewer overflow outfalls.**
MAINTENANCE COSTS - The average life expectancy of a sewage treatment plant is 50 years however, the associated treatment equipment typically doesn't last half of that time. With population growth continually adding strain on existing pipes and sewage treatment facilities, the EPA estimates that with no replacement of existing sewer systems, between 1980 and 2020, the amount of deteriorated sewage pipe will increase from 10% to 44%.***(based on 600,000 miles of sewage pipe in the U.S.)
EXPENSE - The EPA estimates that collection systems typically account for 70% of the overall cost of centralized wastewater systems...this cost is nullified with decentralized treatment.
GOOD SOLUTIONS: Decentralized, Biofiltration
The good news for developers and homeowners is that the truly sustainable solution – treating and reusing the water as close as possible to its source and point of use – brings with it significant benefits to a project.
Affordable, tertiary treatment to reuse standards
A truly decentralized approach removes the need for extensive collection. Since the sewer pipes represent the majority of the cost of the system, the savings can be significant. The EPA recognizes constructed wetlands as providing tertiary treatment to reuse standards so the more attractive solution can also provide high performance.
Scales well – single family / clusters / campus / municipal
Decentralized treatment can be tailored to the job at hand whether it’s for a single family residence, a cluster of buildings or a high-flow municipal scale application. This flexibility can provide tremendous advantages to land use planners and designers. By decoupling the need to facilitate sewer connections, designers and land planners have more choices with lot and building design.
Phases well – build as-you-go, lower up front infrastructure cost
Developers can hedge their financial risk by only building the wastewater and stormwater infrastructure they need – as they need it. With a decentralized approach, if only Phase 1 of a project has been built and is being sold, then only that phase’s water treatment costs have been incurred. And there isn’t any need to feed dog food to a large finicky central treatment plant that needs more occupants before it can function properly.
Landscape amenity – attractive, silent, odor-free
With good design, constructed wetlands can be an attractive asset to the landscaping. Because the water level is kept below the surface, the ground always remains dry and there is no odor and no possibility of breeding mosquitoes. Constructed wetlands can be designed with lush showy plants that invite gardening or with wetland grasses that can be mowed like surrounding turf. Because it is the plants that bring oxygen to the bacteria performing treatment under the surface, there is no need for a noisy blower to pump oxygen.
Little to no energy use
If topology allows, gravity can be used and no energy needs to be consumed for a constructed wetland to treat wastewater to tertiary standards and then to make beneficial reuse through a subsurface drip irrigation system. If the ground is flat, then a lift station is placed between the septic tank and the constructed wetland with a low energy sump pump that only operates long enough to move the intermittent flows.
Minimal maintenance and license / certification requirements
Similar to conventional septic systems, the primary maintenance of decentralized systems consists of monitoring the septic tanks and making sure that they are pumped on a regular basis. This can be easily managed by an HOA by setting up a maintenance contract with locally available pumping services. Unlike more complicated mechanical systems, constructed wetlands qualify for the EPA’s most basic level of operator certification – again, significantly reducing O&M costs.
*Electrical Power Research Institute (2002) Water and Sustainability Volume 4, "US Electricity Consumption For Water Supply and Treatment; The Next Half Century"
***U.S. Environmental Protection Agency (2002) "Clean Water and Drinking Water Infrastructure Gap Analysis"