A Holistic Approach to Water and Wastewater Management
By Jonathan Kaiser
As populations continue to grow and shift, all aspects of the water cycle will need to be optimized for sustainability. Instead of simply continuing to bandage old or install new, costly centralized infrastructure, the goal should be to move toward a dependable, safe, and sustainable water cycle that includes wastewater. Implementing alternative cost effective, efficient, and environmentally friendly methods of water and wastewater management that reduce resource consumption has broad benefits including reduced power demands and aquifer recharge. In a 2014 study comparing resource consumption for centralized and decentralized wastewater treatment systems, it was determined that decentralized systems have a 75 percent reduction in consumed energy, 73 percent reduction in released carbon dioxide, and 68 percent reduction in cost during production and manufacturing compared to centralized systems. For communities, new approaches to improve infrastructure financing is critical to enable communities to implement next generation holistic water and wastewater treatment strategies. The value of preserving the world’s water resource is recognized as one of the greatest challenges of our time.
The evolution of drinking water and wastewater management shifted toward a centralized scheme due to urbanization and the resulting increase of pollutant concentration. The centralized model became the “norm” and public perception followed that centralized management is superior. Meanwhile, globally there are trends of water tables dropping, saltwater intrusion, sewers polluting surface water, and stormwater systems failing to meet the demands of growing populations. The US Environmental Protection Agency’s (EPA) Office of Water published, The Clean Water and Drinking Water Infrastructure Gap Analysis, which identified the potential gap in funding from the year 2000 through 2019 at approximately $270 billion for wastewater infrastructure and $263 billion for drinking water infrastructure.
Recharging the Diminishing Aquifer
Historically water scarcity was limited to the arid west. However, water resource concerns have been occurring in non-historical locations. In coastal areas where water tables are low and wells are beginning to run dry, saltwater is intruding inland, leaving an increasing number of people without a reliable source of life-sustaining water and damaging agricultural lands. One cause is centralized wastewater infrastructure; water is drawn from an aquifer, then consumed, and then discharged a great distance from the source, thus short circuiting the natural water cycle for aquifer replenishment. Also, each wastewater district may have thousands of miles of piping for collection and that piping system consisting of old and new pipes is far from watertight. The resulting inflow and infiltration further depletes the aquifer as does water supply wells for municipal water systems. Coupled with lean rainfall amounts and in some cases drought conditions these factors are extracting a water resource toll in unexpected areas.
Decentralized Treatment Systems Provide Land Use Options and Restore Local Aquifers
If developers and builders had to solely rely on centralized sewering to dispose of wastewater from their projects, development in many areas would be unfeasible due to a lack of capacity to accommodate additional flows, the high unit cost of sewering, or a lack of funding to expand the centralized wastewater treatment plant.
The decentralized model collects, treats, and discharges to the subsurface at or very close to the point of origin, recycling the original water resource to the local aquifer at a low energy cost. Properly designed, installed, and maintained decentralized wastewater treatment systems have the capacity to process large quantities of wastewater into the underlying soils, making this option a passive and sustainable form of aquifer recharge; providing both wastewater treatment and groundwater recharge in one step. Via this sustainable practice, the replenished aquifer can supply wells, recharge wetlands for wildlife, maintain base flow for streams, and counteract saltwater intrusion in coastal cities and towns.
Expanding acceptance of decentralized wastewater treatment systems is critical to environmentally and economically vulnerable areas. Replacing or rehabilitating outdated onsite systems such as cesspools, installing wastewater treatment where none previously existed, and eliminating surface discharge and nitrogen pollution have been leading initiatives. Finding less capital extensive solutions that can extend the life and expand the capacity of existing centralized systems is also a high priority in many communities open to smart sustainable development, but that have aging or undersized wastewater treatment plants.
Reducing Combined Sewer Overflows (CSOs) with Decentralized Strategies
In the United States, there are approximately 75,000 Sanitary Sewer Overflows (SSOs) each year resulting in the discharge of an estimated 10 billion gallons of untreated and partially treated wastewater. The US EPA estimates that there are 5,500 annual illnesses due to exposures to contaminated recreational waters. Another source of watershed and surface water contamination is Combined Sewer Overflows (CSOs). In the city of New York alone there are 996 discharge points of untreated and partially treated wastewater and the US EPA estimates an astounding 1.2 trillion gallons of water from CSOs is discharged in the US each year, acoording to the US EPA Report to Congress on Implementation and Enforcement of the CSO Control Policy.
Reusing Water and Wastewater to Boost Natural Resources
One holistic approach is to embrace water reuse including wastewater. While standards vary depending on the specified use of the reclaimed water, technologies are currently available to treat wastewater to acceptable standards prior to reuse. For example, irrigation water for landscaping may require lower levels of treatment as compared to reuse for non-potable indoor uses such as toilet flushing that requires higher levels of treatment.
Both public stigma and regulations can be barriers to the acceptance of water reuse. The perception of using wastewater as a potable water source seems unnerving and dangerous without proper education; in reality – we are continuously reusing water/wastewater! In fact, all municipal water systems that draw water downstream from a wastewater treatment plant are implementing de-facto water reuse. Decentralized water reuse simply offers a more direct and sustainable form of water reuse.
A still largely untapped water source is rainwater. From small residential rainwater harvesting systems to those designed for large-scale commercial applications, the technology in components, filtration, and controls is propelling this water supply alternative to the forefront. With little treatment, rainwater can be used for irrigation, toilet flushing, and cooling. With further treatment, rainwater becomes viable as a source of a potable water supply.
CSO Challenges in Washington, Indiana
The decentralized solution found by Washington, Indiana, cleaned up a polluted waterway, saved tens of millions of dollars in construction cost, and has lowered operating costs. Washington had problems with CSOs. Like many communities, the city’s centralized infrastructure was old and decaying — most of it vintage 1930. Its storage capacity was minimal. As little as 2.5 mm (0.10 in.) of rain produced CSOs. To make matters worse, between rain events, the water pooled and then dried up, concentrating pollutants. The city struggled with this problem for decades. Early attempts to abate the pollution included enclosing drainage ditches and creeks in large pipes, but these fixes didn’t address overall water quality. Facing federal mandates to clean up its water, the city was in a desperate situation.
The city hired various firms to study the problem and create a solution. The studies proposed conventional, centralized solutions with the most cost effective solution estimated to be in the $53 million range. Given the average income of the city’s 12,000 residents this cost was not a viable solution. The town knew they needed to find an alternative solution that the town’s people could afford.
Water Reuse at Gillette Stadium, Foxboro, Massachusetts
The well-known stadium that serves as the home of the 2019 National Football League Champions, New England Patriots, also carries the record of having one of the largest recreational water reuse systems. When the Town of Foxboro advised the private developers that constructed the stadium that they could not furnish enough water or treat the wastewater from the planned 68,000-seat stadium, it became apparent that the reuse of reclaimed water was the only answer. To meet the demand for water, engineers proposed to incorporate a water reclamation scheme into the design. The design would allow wastewater from the stadium and the community to be collected, treated and reused for such purposes as toilet flushing, irrigation, cooling water and flushing of streets and sidewalks.
The solution to Foxboro’s problem was to capture the wastewater from the stadium, treat it to a high degree, and store it for reuse when necessary. The treatment process is based upon the application of membrane bioreactor technology. These reactors allow the organic wastes (including ammonia) to be biologically degraded by microorganisms, minimizing the need for excess power or chemicals. The solids in the treated wastewater are separated from the liquid fraction by membranes whose pores are small enough to capture viruses. Additional treatment is provided to biologically convert the nitrates formed from the destruction of the ammonia to nitrogen gas. The treated water is re-aerated and disinfected using ultraviolet radiation, eliminating the discharge of bacteria. The community keeps the treated water aerated and stored for use at the stadium or elsewhere, if necessary. Excess water is discharged below the surface of the parking lot by a series of Infiltrator Chamber Beds, allowing recharge of the local aquifer.
With aquifers rapidly becoming depleted and water tables dropping, minimizing the impacts to the water cycle that are under our control is critical for sustainability. Implementing next generation decentralized wastewater treatment, water reuse, and rainwater harvesting approaches are three potential solutions to move toward a dependable, safe and sustainable water cycle.
Jonathan Kaiser joined Infiltrator Water Technologies (Infiltrator) in 2016 as a Project Engineer after graduating with his B.S. in Environmental Engineering from the University of Vermont. Jonathan spends his time at Infiltrator working on septic system design, product regulation, and research and development initiatives. He can be reached at email@example.com.