News from Schwing Bioset

Bissell Point WWTP Expands Biosolids Handling Capability


Written by Tom Welch

Version also published in TPO Magazine, October 2020


The Bissell Point Wastewater Treatment Plant, owned by Metropolitan St. Louis Sewer District (MSD), is the largest wastewater treatment plant in metropolitan St. Louis, MO. Schwing Bioset had previously provided six (6) KSP 25 piston pumps with 50 HP power packs and a live bottom receiving station at the facility that have been in service since 1993. The piston pumps conveyed 25% dry cake solids to the multiple hearth incinerators, but due to the high amount of additional silt that makes its way through the plant via inflow and infiltration during wet weather events, the dry solids content can soar to over 40%. While this nearly 30-year-old equipment continues to perform admirably, MSD was seeking a solution for the biosolids produced at its satellite plants and wanted to utilize the excess incineration capacity at Bissell Point.

Due to the long and successful history with the current equipment at Bissell Point, MSD purchased a larger KSP 45 piston pump and piping system to transport the received solids into the facility, as well as a push floor truck receiving station with over 50 cubic yards of capacity from Schwing Bioset. The new system is able to handle a high volume of biosolids and complements the existing equipment.

Schwing Bioset Biosolids Piston Pump

Schwing Bioset worked closely with Donohue and Associates to design and provide the new biosolids receiving station for the WWTP. The new receiving station, designed utilizing push floor technology, allows dewatered biosolids to be received from other Metropolitan St. Louis Sewer District facilities so that disposal costs can be minimized by allowing the biosolids to be incinerated. Push floor technology was chosen over the incumbent live bottom as a more efficient and lower maintenance system that also improves material flow characteristics.

The push floor bunker design consists of two hydraulically-driven push frames that reciprocate along the bunker floor. The action of the frames breaks material bridging and feeds solids into the extraction conveyor, and rectangular bunkers allow multiple trucks to back up to and unload into the bunker simultaneously. The bin also includes a retractable bi-fold cover integral to the system when not receiving biosolids, which assists in containing odors and prevents rain, snow, and other tramp materials from falling into the bunker.

Schwing Bioset Receiving Station

As plant staff are already familiar with the equipment and its operation, integration into existing operations has gone smoothly and the new equipment provides MSD flexibility in their management of biosolids from within their service area into the future.

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Tags: Wastewater Treatment Plant, Biosolids Piston Pump, Receiving Station

Pima County, AZ, Tres Rios WRF Biosolids System Upgrades - Part One: Cake Pumping


Written by Josh DiValentino


Tres Rios Storage w-caption 2Background: The district of Pima County, AZ, operates a total of eight wastewater treatment plants. The Tres Rios Water Reclamation Facility (WRF) is the centralized biosolids processing facility for all Pima County plants. Tres Rios WRF currently operates 24/7/365 at a 30 MGD capacity, with a projected flow of 50 MGD in 2030. The facility process is; BNR, Anaerobic Digestion, Dewatering, Pumping, Truck Loading, and Land Application of biosolids (cotton is common use). For nearly 20 years, Schwing Bioset, Inc. has provided solids handling solutions at Tres Rios with projects ranging from biosolids cake pumping and cake storage bins, to most recently, nutrient recovery and temporary Screw Press dewatering equipment.


Cake Pumping:  Since the early 2000’s to 2012, the Tres Rios WRF had used a piston pump for biosolids cake conveyance to truck loading. In 2012, the facility completed a Regional Optimization Master Plan expansion, which included an upgrade to the centrifuge building and loading building. The upgrade design replaced the existing piston pump with progressive cavity pumps dedicated to each of the three new centrifuges.

After 6 years of struggling with excessive downtime associated with the progressive cavity pumps, the 10+ year-old piston pump was pulled from storage, sent to Schwing Bioset, Inc. to be rebuilt and reconfigured to fit the existing building, and installed to replace one of the progressive cavity pumps.

Since its reinstallation, the plant has used the piston pump as its primary pump, reducing the downtime and maintenance costs associated with the progressive cavity pumps. The facility no longer needs to de-rate the centrifuges and has been able to dewater the biosolids to a higher percent solids content when using the piston pump, significantly reducing hauling costs. The subsequent uptime and increase in dry cake solids production justified the capital cost of buying an additional Piston Pump, as the payback was determined to be 2 years. One progressive cavity pump will remain in service as an emergency backup for pumping thickened sludge, which is usually thickened from 6% to 8% solids.

The second new Piston Pump will come online in 2020. The Schwing Bioset, Inc. Engineering Team also worked with the district to perform a complete pipeline analysis of the existing cake pipeline. This identified the pipeline upgrades required to re-certify the pipeline for higher pumping pressures, resulting from higher cake solids and higher flow via the Piston Pumps to Truck Loading. This pump technology conversion clearly illustrates that while the initial capital expense of a piston pump is higher than a progressive cavity pump, the long-term expenses over the operating life of the equipment, when factoring in hauling expenses, maintenance costs, and operational downtime, heavily favor piston pump technology.


Schwing Bioset Piston Pump


For more information on this project, read the paper below or contact us.  


Additional Info: Biosolids Cake Pumping Life Cycle Analysis - A True Operators Story

Stay Tuned for More on Pima County Projects:

Part Two: Live Bottom Bins

Part Three: Temporary Screw Press Dewatering

Part Four: NuReSys Struvite Management Project


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Tags: Piston Pumps, Biosolids, Biosolids Piston Pump, Water Reclamation Facility