Once bar screens remove debris from wastewater, stormwater, or other critical projects, the debris must be conveyed to a disposal location. There are many different types of conveyance technologies that can be used for this purpose, including sluices, screw conveyors, belt conveyors, and washer compactors. The right technology depends on a vast number of factors. Engineers and project managers who are designing new headworks or upgrading an existing operation need to take them all into account to develop a system with the lowest operational cost and least overall maintenance.
Conveyance technologies
The most frequently used conveyance technologies include:
Shafted auger conveyor - This type of conveyor is a helical screw-like device with a central shaft that moves debris inside a cylindrical tube or trough. While effective, augers are vulnerable to tacky or stringy debris, which can catch on the shaft, causing jams and other maintenance issues.
Shaftless screw conveyor - A single shaftless screw moves debris forward using positive displacement within a fully enclosed trough. Unlike an auger, there is no shaft for material to catch or stick to. These systems can carry debris upwards at a 25-degree angle and can be fitted with drains to return liquids into the channel.
Belt conveyor - One of the more common conveyance options, belt conveyors rely on motors and rollers to move debris. However, they consume a lot of energy and, without expensive modifications, are mostly limited from horizontal to approximately 10 degrees of incline.
Serpentine type belt conveyors - These can make bends and inclines up to 45 degrees but are costly and require additional maintenance.
Discharge extension option (DEO) - The DEO is a unique offering by Duperon that can move debris from the discharge end of its washer-compactor up to 40 feet in any direction, including vertically. The DEO chute system requires no additional motors, relying on the unique geometry of the compactor’s dual augers to push the plug through the discharge tube.
Sluice - This conveyance technology moves debris in a partial or fully enclosed trough with flowing water. This is ideal for moving wet screenings, particularly when transporting to a washer-compactor or other dewatering system, although it is limited to only horizontal bends/movement.
Factors to consider
Engineers need to take all of the following considerations into account before designing a conveyance system:
Plant layout. The most significant factor (but far from the only one) is the overall layout of the plant. For example, sluices can carry material around a bend and through tight spaces where long horizontal distances aren’t available. However, many facilities have multiple levels or floors and while sluices can move material horizontally or downward, if the debris must be conveyed upward then a shaftless screw or DEO would be a better fit.
Washer-compactors. Related to layout is whether the facility uses a compactor and where it is positioned relative to the screens and the dumpster. After all, many washer-compactors dewater debris, which means that plant managers are not going to want the plug transported via sluice (although a sluice can send debris to the compactor). Instead, a compactor can be followed by a belt conveyor or DEO.
Type of debris. Just as the ideal bar screen will depend on the type of debris, so will the method of conveyance. For example, combined sewer overflows tend to produce a range of debris, such as construction material, chunks of concrete, trash, metals and more, particularly during wet-weather events. The largest of such debris can be a challenge to convey. Shaftless screw conveyors have slightly larger openings — depending on the size of the conveyor — which make them better suited to such applications than a sluice. While belts usually have no enclosure, large and uneven debris can potentially fall off, creating a safety risk to personnel.
Maintenance and safety. Belt conveyors use numerous rollers, each of which is a tangle hazard, which makes them both a safety risk and a potential source of maintenance and downtime. Similarly, shafted auger conveyors can become wrapped/jammed with stringy or tacky debris. Shaftless screws and DEOs, on the other hand, have less chance of wrapping with fewer or no moving parts. They are also fully enclosed. In addition to the obvious safety benefits, this keeps odors and bacteria contained, which makes for a healthier and more comfortable working environment. When maintenance or cleaning is required, both conveyance systems can be fitted with lids and hinges at strategic points.
Synergy and design. Achieving the best performance from a conveyance system requires a holistic understanding of how manufacturing processes and design elements interact to maximize efficiency and functionality in the space allotted. Duperon offers a complete suite of technologies, including bar screens, washer-compactors, and all of the conveyance systems mentioned above, each of which is customizable to the application and inherently compatible with each other. This ensures both maximum flexibility in design and peak operational efficiency.
Ultimately, selecting the right conveyance technology for debris management is a complex decision. In many cases, multiple technologies may be needed. Duperon’s integrated suite of customizable solutions maximizes design synergy and operational efficiency. By prioritizing a holistic understanding of the operational environment and leveraging innovative technologies, it is possible to optimize debris management while reducing downtime, enhancing safety, and driving overall cost savings.
