This is the first in a series of blogs we will be releasing most every week on CRWA’s Urban Smart Sewer and Blue Cities work. Each post will build on its predecessors. Rather than start at the end, however, with our conclusions and current projects and objectives, it occurred to me that I should start with our rationale, because it is important to understand.
I’ve attended a few professional conferences lately that have me thinking. They were attended by a collection of the leading water organizations from across the nation identified by their new approaches to centralized urban drinking water, stormwater, and wastewater infrastructure. Their focus was on efforts to introduce greening to reduce stormwater runoff on the one hand, and enhance methane production in wastewater treatment to generate energy and reduce carbon emissions at end-of-pipe wastewater treatment plants on the other. There were also several financing approaches discussed, including notions around something like 100-year municipal bonds.
What struck me was that the starting point for each investigation is the managed water/wastewater system itself. The systems are analyzed within an environmental regulatory framework, and additions to those systems are made to meet regulatory requirements, control costs, and reduce energy demand.
The general notion is that by introducing greening to cities (rain gardens, swales, trees, infiltration chambers) we can capture stormwater runoff, reduce water pollution, and depending on the size of the green areas, store one to three inches to help reduce flash flooding. On the wastewater side, greening can dampen combined sewer overflows (CSOs). At the end of the wastewater collection system, at the sewage treatment plant, the plan is to capture methane from wastewater treatment and burn it to generate energy. By adding food waste to the treatment stream, the digesters at these plants can produce more methane to generate more energy. The whole system energy generation process reduces carbon dioxide and methane emissions over putting food waste and organics in landfills, and makes the plants more efficient, meeting their own energy demand and selling any additional electricity to the electric grid.
This is all good stuff. But to my way of thinking, the solutions are limited by the perspectives of the investigations. Adding greater efficiencies to existing systems is good, but given the analyses we’ve conducted at CRWA over the past 25 years, together with the complexities our changing climate presents, makes me wonder whether these efficiencies will prove good enough.
There’s another way to understand urban water and wastewater. Urban systems are built to convey potable clean water, send it through pipes to homes and businesses, collect it again once used, and then treat it and discharge it. Compare our water systems to those in a forest. Rain falls and is collected where it falls by soil and flora. It is slowed by leaves and soft ground, infiltrated, collected in aquifers, large wetlands, vernal pools, ponds, lakes – keeping water local for use and reuse. There is no wastewater treatment plant in nature – the waste of one process becomes the energy for the next in a cycle of resource-to-waste-to-resource.
Examining only how existing urban systems might become incrementally more efficient, we miss how they sit on the land, their larger impacts on habitat and water quality, and the pressures they put on nature.
In fact, the forest is a water system. Unlike our current urban engineered systems, however, it dramatically reduces the amount of water needed for all things to flourish through its highly interconnected nature.
Examining only how existing urban systems might become incrementally more efficient, we miss how they sit on the land, their larger impacts on habitat and water quality, and the pressures they put on nature. They contribute mightily to low flow in rivers and tributary streams, particularly in summer months, as clean groundwater seeps into cracked pipes, is contaminated, and whisked off to treatment plants where we expend energy to clean it again. As an example, reservoirs supplying potable water to Boston have reduced flow in the Nashua River by roughly 64 percent and in the Swift River by as much as 74 percent. Even the best urban systems among them, and Boston’s is among the very best, continue to dump some sewage into rivers, lakes, and oceans from CSOs, failed pipes, and illegal cross-connections. And in the face of endemic drought, most will not sustain us.
Over the past 25 years, CRWA has investigated our urban water/wastewater infrastructure from the perspective of how our systems sit on the land. And we’ve been working hard at translating the lessons we’ve learned from studying the land to our urban systems. Think about it. The forest as a system generates tremendous energy in the same places it is used. It can handle catastrophic events, and has identifiable principle working parts. The question is whether we can apply the principles of the forest system to our own water problems.
Image source: Roman Boed, Wikimedia Commons (CC Attribution 2.0 Generic)