Most cities across the globe face a plague of water infrastructure problems, from combined sewer overflows to stormwater pollution to deteriorating pipes and treatment plants. As our climate changes, that infrastructure is proving inadequate to the tasks of building resilience to drought or managing severe flooding. Many wastewater treatment plants situated on the coast are directly threatened by impending sea level rise.
A flooded treatment facility. Source: New England Interstate Water Pollution Control Commission.
Moreover, 19th Century water systems cause significant damage to our natural world, something that has been accepted as a necessary cost of modern life. Toxic algal blooms, low flow, stormwater pollution, oxygen depletion, are all consequences of existing water management systems. In the 21st century, new technologies and methodologies make these impacts no longer inevitable. Furthermore, many cities are leading the way in climate adaptation and mitigation. Major metropolitan cities are setting aggressive carbon reduction goals but are struggling to establish clear paths toward meeting them.
Explore this interactive map to see how Boston's coastline could be impacted by sea level rise.
Due to the inherent damage large centralized water systems visit on the environment, Charles River Watershed Association has for 20 years been pursuing a financially responsible approach to re-engineering them to restore nature, build resilience to drought and flooding, and build flexibility into water infrastructure in anticipation of climate changes. With our partners Natural Systems Utilities (NSU) and Industrial Economics (IEc), we conceptually tested a unique concept for distributed wastewater treatment systems, called Community Water and Energy Resource Centers (CWERCs). Throughout the project, our team met and reviewed our work regularly with a dedicated and knowledgeable Technical Advisory Committee (TAC). Our TAC was comprised of: the Massachusetts Water Resources Authority (MWRA), the Massachusetts Department of Environmental Protection (MassDEP), the Built Environment Coalition, the Boston Water and Sewer Commission (BWSC), the City of Boston Energy, Environment and Open Space Department, City of Cambridge, the Massachusetts Department of Energy Resources (DOER), the Boston Planning and Development Agency (BPDA), NRG Energy, and the U.S. Environmental Protection Agency (US EPA) Region 1 (Ex Officio).
A rendering of a Community Water and Energy Resource Center as proposed by CRWA
CWERCs are distributed energy generating and waste recycling plants. CWERCs mine sewage infrastructure, treating 1 to 5 million gallons daily and recycle organic waste in urban and suburban areas where it is produced. In our conceptual design, the CWERCs combine a membrane bioreactor, thermal energy heat pump, anaerobic digester, combined heat and power (CHP) system, nutrient recapture and composting. Utilities and products produced by each CWERC include electricity, thermal energy for heating and cooling, reclaimed water meeting drinking water standards for non-potable uses, and fertilizer and nutrients. Generating energy from sewage and reducing the distance food waste needs to be trucked significantly reduces green house gas emissions.
In this study, CWERC operations are extensively modeled using real-world conditions. A site selection analysis was conducted to identify two local urban neighborhoods to model CWERC operations using actual site conditions. In a three-phase site selection process two neighborhoods were selected for modeling in the City of Boston. The Innovation (or Seaport) District and the Stony Brook neighborhood encompassing parts of numerous Boston neighborhoods including Mission Hill, Fenway and Roxbury, an environmental justice neighborhood, serve as the two study area neighborhoods.
We ran multiple technical and financial scenarios to assess outputs of the prototype CWERCs and analyze their operational feasibility. CWERC 1, designed to treat 2 million gallons daily (mgd) of sewage, has a capital cost of $46.7 million, and generates over $7 million in income from utility sales, renewable energy credits, and tipping fees. Operations and maintenance costs are estimated at $4.9 million. Income is generated from sales of electric and thermal energy, reclaimed water, renewable energy credits, soil amendment products, and tipping fees for the disposal of organic waste. The model does not include a fee for wastewater treatment. CWERC 2, treating 3 mgd daily, has a capital cost of $53.8 million. Income for CWERC 2, without collecting a fee for wastewater treatment, is estimated at $9.6 million against $7 million in operations and maintenance costs. CWERC 1 is modeled to collect 80 wet tons of food waste daily as the neighborhood contains multiple food and beverage production and processing facilities, while CWERC 2 collects 54 wet tons of food waste per day.
Modeling Results CWERC 1 Scenario (output volume and value will differ with different locations and scenarios)
|Mined wastewater||2 mgd||$0|
|Renewable Energy Credit (accounting for 90% utilization)||6,732 MWhr/yr||$439,400|
|Thermal Energy (includes energy input to heat pump)||273,181 MMBtu/yr||$2,326,000|
|Thermal Energy from CHP||26,145 MMBtu/yr||$223,000|
|Total Electricity Generation (for demand with excess to grid)||7,480 MWh/yr||$665,720|
|Sludge compost (Class A biosolids)||770 cu yd/yr||$19,200|
|Food Waste Tipping Fees||29,200 tons/yr||$2,336,000|
|Reuse Water Sales||1.5 mgd||$1,201,000|
|Food Waste Digestate Soil Amendment||12,650 cu yds/yr||$151,800|
|Food Waste Digestate Nitrogen Recapture (Ammonium Sulfate)||85,100 lbs-N/yr||$59,600|
|Operating and Maintenance (O&M) Expenses|
|Electricity Demand||3,870 Mwh/yr||$432,600|
|Natural Gas Demand (Heat pump and CHP)||188,466 MMBtu/yr||$1,840,100|
|Labor, Chemicals, Maintenance||$2,602,800|
Through modeling, our team determined scenarios in which plants are financially viable without charging a fee for wastewater treatment. Under existing site and regulatory conditions, if CWERCs receive favorable public financing of 0% to 2% interest and require no capital investment for the property they are built on, CWERCs will “break even.” Break even conditions are defined as a scenario in which the net present value of the infrastructure is equal to zero over a twenty year life span (including capital replacement reserves) with no additional revenue or capital investment required (i.e., the CWERC is self sustaining). Collecting a small wastewater treatment fee, a third or less of Boston’s current rate, would make the CWERCs viable in every public and private financing scenario investigated. The modeling further revealed that site specific conditions such as organic waste availability, sewage availability, and markets for reclaimed water and thermal energy influence financial conditions. Therefore consideration of these conditions, neighborhood input, and local water management impacts should drive site selection.
In the study area neighborhoods, CRWA also examines historic natural hydrology. CWERCs are introduced to restore natural hydrology using a portion of the water reclaimed. With such restoration, neighborhoods gain improvements in flood control and drought resilience, heat island mitigation, reductions in polluted stormwater runoff, enhanced groundwater recharge, and an increase in open space amenities. In Neighborhood 1, we propose 44 new acres of green infrastructure across the district, enough to filter runoff from a 1 inch rain storm. Multiple opportunities to create new or restore historic water features using CWERC effluent are also presented including reestablishing buried canals by daylighting two large stormwater culverts.
Greening plan for Neighborhood 1
Rendering of proposed stream for Neighborhood 1
An ambitious design for a 300 acre floodable wetland is also presented. This large wetland area recreates flood storage for what was once an historic open water bay. Allowing this area to flood would protect the neighborhood against fresh water flooding, and modest storm surge and sea level rise, while also providing new, unique recreational opportunities in an urban setting.
Existing View of Future Open Space Identified in 100 Acre Plan
Rendering of 100 Acre Wetland
Neighborhood 2, the Mission Hill/Stony Brook neighborhood, is a densely developed area that overlays the historic confluence of the Stony Brook, Muddy River, and Charles River tidal estuary. Currently the Stony Brook is completely buried in culverts, the dammed Charles River is no longer tidal, and nearly all the rivers natural flood plain wetlands have been filled and developed. Our greening plan for the neighborhood identifies 14 new acres of green infrastructure, enough to filter or infiltrate runoff from a half-inch rainfall event. A site identified within the neighborhood hosts CWERC 2, and the design includes a constructed urban stream for treated water to flow to the Muddy River, mimicking the historic confluence of the Muddy River and Stony Brook. Base flow to the restored tributary would come from CWERC reclaimed water.
In addition to our analysis of the financial viability of CWERCs, we also looked at the social welfare benefits of CWERCs and associated greening plans. Social welfare benefits include the value of both resource recovery (renewable energy generation, emissions reduction, reclaimed water) and environmental restoration (wetland services, ecosystem services, carbon sequestration, recreation potential, property value enhancement).
For Neighborhood 1, the assessment of potential benefits including annualized energy production and savings, reduced carbon emissions, air quality improvements, greening enhancements, and property value enhancements produce a range of economic benefits from $7 million to $14 million annually. If the 300 acre proposed wetland is included in the analysis, the social welfare economic benefits increase the range to $9 million to $20.5 million annually. For Neighborhood 2, the estimated potential benefits range from $11.75 million to $24 million annually. If groundwater recharge to preserve wooden building supports are included in the analysis, the range jumps to between $20 million to $47 million due to the avoided cost of replacing rotted wooden pilings.
|Benefit||Estimated Annual Benefits||Comments|
|Lower Estimate||Upper Estimate|
|Annual Welfare Benefits, Excluding Fort Point Channel Wetland|
|Energy Production and Savings||$1,150,058||$1,338,025|
|Reduced Carbon Emissions||$94,957||$455,056|
|Reduced Criteria Pollutant Emissions||$177,852||$443,419|
|Green Infrastructure Carbon Sequestration||$1,690||$3,390|
|Air Quality Improvements from Green Infrastructure||$13,932||$47,232|
|Avoided Stormwater BMP Costs||$4,997,222||$9,994,444||Partial overlap with wetland services estimate|
|Quantified Welfare Benefits that Overlap with Other Categories|
|Annual Wetland Services||$6,858||$21,439||Reflects only the wetland services associated with the two medium-scale wetlands; overlaps with avoided BMP costs.|
|Annual Property Value Enhancements from Greening||$6,992,375||$13,984,751||Reflects broad set of amenities and therefore overlaps with other benefits (e.g., energy savings, recreational benefits); Annualized assuming 7% discount rate and 50-year useful life.|
|Annual Welfare Benefits Associated with Fort Point Channel Wetland|
|Fort Point Channel Recreation||$1,237,500||$3,888,000|
|Fort Point Channel Wetland Services||$122,810||$774,203|
|Avoided Stormwater BMP Costs for Fort Point Channel Wetland||$7,914,013||$15,828,025|
Site specific social welfare benefits are an important aspect of managing water, energy, and waste more holistically. Benefits are significant, and will alter the quality of life in the affected districts. Further, property value enhancement and associated increases in property taxes as a direct consequence of the greening can help provide the revenue necessary to fully implement and maintain new green spaces.
There are a number of creative ways progressive cities across the nation have used to pay for the broadcast introduction of “green infrastructure.” In “Opportunity: Stormwater Trading”, we introduce Blue Cities Exchange, CRWA’s stormwater trading website based on trading pounds of phosphorus. Cost differentials between introducing green infrastructure to dense, impervious urban sites compared to less dense and more permeable sites support a market for trading stormwater treatment credits.
Finally, extrapolating from the financial and economic analyses of the two CWERC and neighborhood greening plans, we investigate expanding CWERCs to all 43 communities in the Massachusetts Water Resources Authority wastewater system. Recognizing the limitations in such an extrapolation, particularly given the site-specific nature of expenses and income, and that the two sites modeled for this study are located in two of the most dense and therefore most expensive areas in Massachusetts, the analysis remains useful. In the analysis, we introduce additional storage to each CWERC at 3 and 5 times the daily volume treated, and introduce collection of residential food waste to increase power generation. We estimate that a system of CWERCs could be operated at costs very similar to the cost of operating and maintaining the existing system. For a fee covering the operations and debt for its existing centralized system, regional authorities operating those systems could over time shift treatment responsibilities to a mix of their own CWERCS and others operated by city departments, neighborhood organizations, and private entities. Given the social welfare benefits, the enormous environmental benefits, and the climate change preparedness gained, CWERCs and the greening and restoration of natural hydrology presented here make for a compelling argument to transform our wastewater and stormwater systems over time.
Deer Island Treatment Plant Service Area Communities
CRWA started this investigation 20 years ago as we systematically studied the Charles River and its myriad issues. The analysis in Transformation represents our take on what is necessary to fully restore the Charles River, prepare eastern Massachusetts for many of the vagaries of climate change, and achieve those ends in a financially responsible and economically desirable way.
The key to constructive restorative change lies in managing water, carbon, and nutrients in a way that replicates their natural cycles. Our team applied the principles of nature to develop a plan for a new generation of water infrastructure that effectively provides for human demand and restores nature while building resilience to drought, flooding, and warming. CRWA rejects the concept of “waste” and proposes generating significant energy from organics currently being thrown away. We restore the natural water cycle by breaking up centralized systems into distributed networks of interconnected water and energy facilities which mine sewer pipes to reuse the water, reducing potable demand, and producing local, renewable energy. We recreate natural hydrology through stream and wetland restoration and the introduction of green infrastructure. By reconnecting stormwater and reclaimed water to restored urban water resources, our landscapes flourish and we build natural and social resilience. We accomplish all this while capturing new revenue streams and in the process both adapt to and mitigate global climate change.
CWERCs are replicable and adaptable. Through integration of water, energy and waste management, CWERCs integrate the function of multiple facilities that individually are resource and capital intensive. This dramatically reduces system wide costs and environmental externalities inherent to the current single-function, linear, take-make-waste infrastructure model.
CRWA’s case studies reveal that CWERCs are self-sustaining while charging users only a fraction of current water rates for non-potable reuse water and wastewater treatment. In our Boston case studies, based on local input factors for commodity costs and sales, CWERCs are sustainable at roughly 30% of the current potable water charge and $0 wastewater treatment fees. A single CWERC, treating 2 to 3 million gallons per day (mgd) of wastewater reduces annual CO2 emissions by as much as 30 million pounds. Finally, our economic models show that we can construct a distributed network of CWERCs to replace existing centralized systems while remaining cost neutral in the near term and likely profitable in the medium and long terms.
Based on the results of this study, CRWA is actively seeking partners to work with on a CWERC implementation project. Through our robust advocacy program we are also seeking regulatory and policy changes necessary to encourage and incentivize our holistic approach. In many ways, cities are leading the way on climate change adaptation planning, and the City of Boston is one of the leaders in this movement. Cities are recognizing the benefits of district scale energy generation both for resiliency and to improve efficiency and help achieve greenhouse gas reduction targets. Green infrastructure is also being identified as a method of achieving multiple goals such as flood mitigation, CO2 sequestration, cooling, energy reduction, CSO compliance, improving air and water quality, and more.
It is essential that the infrastructure we invest in today is ready to face the challenges climate change will bring. It is imperative that we transition away from a fossil fuel based economy as soon as we possibly can. This will require significant investment in renewable sources and employing all renewable energy generation opportunities at hand. Nature’s remarkable endurance and self-healing abilities must be guiding forces as we chart our course forward. We can no longer just live on the Earth, we must instead, using Nature’s own principles, learn to live with the Earth.