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It's inevitable. Wet wipes, sticks, croquet balls (yup, we've seen it) and other random objects somehow make their way to wastewater treatment plants. That's what screens are for right? Despite step, perforated or drum screening systems at wastewater treatment plants, debris finds a way through. Where screens fail, solids reducing equipment steps in. But which is right for your process?
Flushable wipes, string, rags, hair, plastic fragments, applicators, plastic bags, can all pass by screens, causing clogging, blockages, and damage to downstream pumps, valves, and processing equipment. We don't have to tell you how this affects your overall maintenance time and contributes to parts and labor costs.
If your plant has considered implementing a solids reduction system to curb the rising costs attributed to debris, read on. We'll break down the differences between popular solids reduction equipment, and where they're best applied.
Outside of screening systems, solids reduction equipment falls into two categories: macerators and twin-shaft grinders.
Maceration technology provides the best results when installed after primary screening or headworks systems. These units are specifically designed to sheer cut any material that flows through. Some designs provide heavy debris removal traps, as macerators are not designed to cut hard solids like rocks and metal.
Twin-shaft grinders operate using two counter operating shafts with cutting blades attached. As the cutting blades turn, they pull moving solids around the radius of the housing into the center between the cutting blades. This is a straight through process, moving product through the grinder without a debris trap.
Macerators are designed for in-line pipe installations. Macerators need to have liquid flowing through the pipe, as they cannot run dry. These units tend to do better with small solids like hair, wipes, rags, and plastics as compared to large heavy solids. But don’t be fooled, wadded up rags and wipes are just as troublesome to pumps as wood or metal. In this case, macerators can provide ideal protection. Remember, macerators are best suited for refined cutting after the headworks of a wastewater treatment plant.
Twin Shaft Grinder
Twin shaft grinders are designed for both in-line pipe installations and channels. These units can run dry continuously and can handle both medium-to-large solids.
Here are two examples of cutting results between the two solids reduction categories.
Solid: 10mm Nylon Rope: The twin-shaft grinder shredded the rope. The macerator exposed and cut the inner filament.
Solid: Q-Tips: The twin-shaft grinder cut most of the shafts and shredded the cotton. The macerator produced fine consistent pieces.
Because a twin-shaft grinder is often placed in front of the headworks or in lift stations far from a treatment plant, it could encounter much larger debris. That might not always include a boot or a pair of jeans, but know that a well-designed unit should be able to handle such material as shown here in a testing run done by Vogelsang USA using an XRipper Twin Shaft Grinder.
In wastewater treatment plant applications, twin-shaft grinders and in-line macerators can be added or retrofitted into several applications. Some of these applications include:
This diagram will provide you with a general sense of where the two units are most applicable.
Every situation is different, and while a twin-shaft grinder is suited for most any application where solids reductions is needed, you’ll find that a macerator often provides much better performance as you move further into the wastewater process.
Still not sure which is right for your process? Ask us about it! We gladly provide technical assistance to businesses and municipalities in Wisconsin and upper Michigan.