DECENTRALIZED LOW COST SEWERS -- BETTER, FASTER, CHEAPER
Decentralized sewer systems are mini-sewer systems. Rather than lay big pipes all over town, neighborhoods needing treatment can be serviced one by one, thus saving moving wastewater great distances to one place where the wastewater usually gets wasted by being dumped into the ocean. Decentralized sewers save taxpayer money. EPA favors decentralized sewers over centralized sewers as better for the environment and more affordable for communities. So does the Conservation Law Foundation and national environmental organizations such as Clean Water Action.
The first chart below shows how decentralized and centralized systems differ. The conventional centralized system lays big pipes deep under streets and drains all the wastewater to one location, as in Chatham's case above Cockle Cove, to drain into the cove and Nantucket Sound. Along the way it picks up a great deal of drinkng water from the water table, which also winds up wastedin Nantucket Sound.
This second chart shows some of the basic differences and notes why decades-old centralized sewers are still thought of as the standard, though they are far more expensive and are environmentally disruptive. In centralized sewers, big pipes are laid deep under roads, often invade and deplete water tables since they leak. Decentralized mini-sewers are far less expensive and better for the environment since they use smaller pipes that generally don't leak at all, are installed above water tables and recycle cleansed wastewater to the water table. Decentralized systems are in wide use throughout the U.S. (though not yet much in Massachusetts) and Canada. DEP will be putting more emphasis on decentralized systems because of the need to do the job of nitrogen removal from coastal waters affordably.
This third chart notes the great number of decentralized systems are in operation across the United States. Because they use less resources, involve shorter piping distances, no deep ditch digging, don't tie up streets with construction, they can be built much quicker and show improvement in water quality sooner.
Slides courtesy of Jim Kreissl, former top researcher at EPA National on alternative systems.
To view JIm Kreissl's full PowerPoint presentation at the Mashpee December 5, 2009 conference on "Rethinking Sewers on Cape Cod," click on the link below.