Failing septic systems nationwide and the Clean Water Act helped spur the development and adoption of a system that revolutionized wastewater collection and transport. Since the days of the Roman aqueducts, common sense dictated that wastewater always ran downhill. In the latter half of the 20^th century, a new technology changed that reality. Previously orphaned sites that existed in areas of high water table, below grade or heavy rock strata could now be sewered economically and in a more environmentally sensitive manner.

The low-pressure sewer (LPS) system, also known as a pressure sewer, consists of a network of pressure pipes and grinder pumps, which may be installed at each home site. The grinder pumps collect all wastewater from the home and grind it into slurry. The wastewater is then pumped to a larger sewer main or directly to a wastewater treatment plant.

Grinder pumps were first developed 40 years ago. Today's state-of-the-art grinder pump is more reliable and durable than ever before.

The modern pressure sewer system employs sophisticated technology known for its reliability, minimal maintenance, low upfront costs, reduced operating expenses and ability to be installed at any site, regardless of topographical challenges.

It uses an unobtrusive small-diameter pipe installed below frost line and conformed to the natural topography. Unlike conventional gravity central sewers, which can use up to 24-inch pipe and require deep excavation, the pressure sewer system employs small diameter 1½- to 6-inch pipe, and is not destructive to natural or built features.

Case Studies

Athens, Tennessee

The inadequate, aging conventional gravity system could no longer handle the amount of wastewater produced in Athens, Tenn., a small rural town of 14,128. The increase of water infiltration and inflow levels made things worse.

Athens faced a daunting task, and the situation was dire. "The town had been under a state-ordered sewer connection moratorium since 1990, preventing much needed growth of industry, manufacturing and population," said Wayne Scarbrough, Athens Utility Board (AUB) assistant general manager.

A $20 million wastewater treatment facility renovation, completed in 2005, was part of the solution but was still not sufficient. One town project was particularly effective in eliminating infiltration and inflow. Rather than exchange the archaic conventional gravity array with a newer version of the same technology, the AUB opted to abandon the old for an alternative replacement in a particularly problematic, wastewater-challenged section of town.

"Rainwater run-off that bypassed the pump station contributed considerably to the problem, especially in spikes during wet weather flow. We had to replace the gravity system and decided on a low pressure system with grinder pumps," said Randy Harrison, AUB wastewater construction supervisor.

"Because we installed smaller mains, construction was much less intrusive on our customers and in some cases not recognized except for the installation of the [grinder pump] station. Using the grinder pump system we have now permanently eliminated all infiltration and inflow," said AUB Superintendent Jill Davis. 

Not only did it reduce operational costs, but this low pressure scheme also yielded savings in excavation, infrastructure and materials costs and minimally disrupted the surrounding area.