GRIT REMOVAL: PISTA® vs. Stacked Tray Systems
 
Let's see how the PISTA® Grit Removal System stacks up to stacked tray systems.
 

Key Differences You Need to Know about Stacked Tray:

Conventional Settling Utilizing Internal Plastic Plates
 
Much Higher Initial Purchase Price  
 
Higher Installation Costs -- Greater Concrete Volume Tankage and Total Footprint
 
Higher Annual Energy & Utility Costs
 
Greater Headloss for Systems 20 MGD and Under
 
S&L systems are Completely USA Made and Developed by an American company.
A stacked-tray manufacturer has a history of misrepresenting S&L PISTA® technology (lumping it with other conventional sloped-floor vortexes), using questionable, embellished, and/or non-sourced data and reports, while attempting to shift conversation away from what matters relative to PISTA® system design.
 
Installation Cost Factors

Stacked-Tray Design / Installation Cost Factors vs. S&L

Stacked-tray has a significantly higher purchase price.
 
Stacked-tray requires larger concrete basin / construction costs 
 
Stacked-tray has a higher total installed cost
 
Stacked-tray has smaller max. capacity units (up to 36 MGD through 12-tray system).
 
The PISTA 360® offers a lower footprint & much lower installation costs than Stacked-tray systems.
Stacked tray footprints will vary depending on project requirements. However, stacked-tray units can often require deeper settling basins to house their settling devices inside (especially when adding a grit collection hopper). Compare below the average grit tank footprint (area) between both system types based on the average of more than 30 published project design specifications.
 
Side-by-Side Project Example
Location: Texas
Bid Time: November 2015
 
Operational Cost Factors

Stacked-Tray Design / Operational Cost Factors (vs. S&L)

Most stacked-tray relies on 24/7 continuous grit pumping = higher energy costs
 
Stacked-tray requires higher utility water reqs. (at least 65,000 gpd) = higher op costs
 
If Stacked-tray systems are designed to remove 75 micron particles, organics will necessarily be captured and processed in the grit handling system, creating higher odor potential and additional grit washing needs. Residual organics are continuously recycled.
 
Stacked-tray systems must require basin draining in order to periodically clean build-up of grease and oil on the trays (which can collect other debris over time if not cleaned). Likewise grit can build up in the bottom of the basin over time.

 
Performance Factors

Stacked-Tray Performance Factors (vs. S&L)

A stacked-tray manufacturer claims 95% removal down to 75 microns, but in actuality they derate for peak flows: Peak flow 18 MGD: 95% of all grit 100 micron (140 mesh) and larger. Average flow 6 MGD: 95% of all grit 75 micron (200 mesh) and larger.
 
Significantly fewer proven installations over time
 
Stated removal efficiencies decrease for peak flows
 
Removes untreated organics along with grit
 
75 microns (200 mesh) can be size of organic particles and their grit dewatering equipment cannot possibly differentiate from a silt-like grit and organics so essentially, these are continuously recycled.
 
Maintenance: oil / grease build-up on trays requires dewatering to clean. One designer indicated to us that they always include money to allow for this circumstance.

Next Topic...
Grit Testing
 

We Help Protect Your Plant and the Bottom Line
With decades of grit science and experience drawn from more than 2,600 global grit removal system installations, Smith & Loveless delivers innovative solutions that effectively meet the needs of your plant over time.

Grit removal success starts with understanding how to manage flow velocity for superior removal efficiency, which is achieved through constant R&D, field experience, and forward-thinking engineering. Beyond that, because all systems are indeed different, one must analyze how purchase price, installation cost, energy use and utility cost will affect the value of the grit system investment.

American-made PISTA® Grit Removal Systems, with continued new developments from Smith & Loveless reign as the standard of excellence that all others attempt to emulate. With new products such as the PISTA® 360™ with V-FORCE BAFFLE™, OPTIFLOW 270™, the PISTA® VIO™ and PISTA®Works™, we prove once again that at Smith & Loveless, we do more than develop industry firsts. We build industry bests.

 

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