A STEP in the Right Direction

Effluent Pumping Is the ‘Alternative’ to Consider

The concept of a Septic Tank Effluent Pumping (STEP) system dates back thousands of years, evolving from before Rome’s Coloca Maxima in the 6th century BC to more modern designs of the 21st century CE. Early STEP systems were basic, comprised of common septic tanks and an unscreened centrifugal effluent pump elevated by a cinder block in a tank. Today, a modern STEP system includes pumps, fiberglass or plastic tanks, passively self-cleaning filters, plug-and-play electrical and control connections, and remote monitoring capabilities. 

Despite its long, established history, a STEP system is still referred to as an “alternative wastewater collection system” by many regulating bodies, including the Florida Department of Environmental Protection. Furthermore, very few design professionals understand the costs, benefits, and design principles for effluent-only sewer.  

STEP, as the name implies, conveys only effluent from the wastewater source to a treatment facility. The solids and scum stay behind inside an onsite processor, which provides passive, low-cost primary treatment prior to its conveyance.  

Without solids in the wastewater, highly efficient, high-head pumps combine with small-diameter pressure mains to move liquids from large communities to treatment centers without the need for lift stations. Collection mains are pressurized and above the water table, mitigating the inflow of extraneous water and preventing overflows at sanitary sewers. Like water mains, collection lines can be looped for redundancy, creating multiple routes between service areas and treatment plants. 

As a result of the pretreatment that STEP sewers provide, wastewater treatment plants will save money. How? Headworks are not required. Aeration basins, blowers, clarifiers, and digesters can be downsized. The treatment plant will use less energy and produce fewer biosolids by volume. In addition, for areas that may utilize reclaimed water, local treatment centers can pull wastewater from the collection system to manage and use it in their communities.  

Here are some examples of communities that benefitted from a STEP system: 

• Case Study: STEP Project Profiles – In Montesano, WA, the savings from a new effluent-only sewer allowed the town to reduce the size of its wastewater treatment plant while converting its existing sewer to a storm sewer. Crews installed a STEP sewer system with more than 1500 connections in half the time as installing a gravity sewer – and at a lower cost. 

• Case Study: Orenco Effluent Sewer Protects Lagoon – Engineers found that a STEP system was the most cost-effective solution for Vero Beach, FL, community. In fact, the expected cost of a STEP system was half of a gravity sewer. The reason? Directional boring, which required minimal construction to connect each onsite collection tank to the city’s central wastewater treatment facility. 

• Case Study: South Alabama Utilities – South Alabama Utilities (SAU) in Mobile County worked with developers to install more than 60 miles of liquid-only sewer lines. The infrastructure will be able to handle 4000 new homes, plus schools, apartments, and business parks – with ability to grow, thanks to the modular design of AdvanTex® AX100 wastewater treatment units.    

Today, more than ever, the coastal areas across the United States have a need for watertight, sustainable, economical, adaptable wastewater collection systems. Effluent-only sewer is a viable and proven technology that is much more than an “alternative wastewater collection system.”