Conference Agenda

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Session Overview
Session
Session 28A: Facility Operations and Maintenance: Wet Weather Treatment
Time:
Wednesday, 11/Sep/2019:
8:00am - 10:15am

Session Chair: Gregg Thompson, Jacobs;
Location: E143-144

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Presentations
8:00am - 8:45am

Pitfalls of Using HDPE for Process Piping

John Koch

HDR, United States of America;

The construction industry, engineering community, and utilities strive to trim costs and develop the maximum project from ever-shrinking budgets. HDPE pipe is being promoted as a cost saving alternative that provides superior performance and very low head loss characteristics. Testing by the Plastic Pipe Institute (PPI) has documented Hazen-Williams flow coefficients greater than 160 even with the internal fusion beads left inside the pipe test sections. The PPI’s Handbook of Polyethylene Pipe, Second Edition, suggests a design C of 150, as does the Chevron Phillips Chemical Company Bulletin PP-901. AWWA Manual M55 also recognizes PE pipe as a viable material.

This presentation will focus on two facilities where HDPE was used for process piping within a treatment plant. The flow coefficients used in the hydraulic calculation were conservative when compared to the published PPI test data.

In one facility, a distribution structure splits flows to three process trains. At start-up the total design flow could not be routed through the distribution structure. At two-thirds of the design flow, the water level over-topped the emergency bypass weir. Methodical field testing determined the conservative flow coefficients used by the designers did not account for the internal beads at each fabricated elbow, tee or flange connection. The longest pipe run had 40 beads between the flow splitter and existing basins.

In another facility, HDPE pipe was used for the suction piping in pumping system. The designer used a conservative flow coefficient; however, testing at start-up revealed the calculated suction pressure and the actual measured suction pressure were substantially different. This piping configuration had 10 internal weld beads.

In both case studies fielding testing and verification determined that multiple interior weld beads imparted a resistance coefficient (K) greater than 0.15.



8:45am - 9:30am

Innovative Strategies and New Technologies for Wet Weather Treatment in the PNW.

Jim Fitzpatrick, Ho-ping Wei

Black & Veatch Corporation, United States of America; ,

Wet-weather flow management for wastewater treatment utilities in the Pacific Northwest is challenging, because of the unpredictable size and nature of wet weather events that are even more complicated by climate change, and the uncertainty of what future requlations will require. The planning and planning of new treatment facilities need to consider a wide range of strategies for source control, conveyance, and treatment to provide the optimum long-term solution for each watershed.

Fortunately, municipal utilities now have a larger variety of feasible treatment alternatives than ever compared to just a generation ago, when most of North America’s water quality regulations and policies were crafted. Significant advances have been made since then, both in treatment technologies and in the profession’s understanding of wet-weather problems. Many of these "new" treatment technologies have been in operation for over a decade, proving their capabilities. This paper discusses regulatory drivers for wet weather treatment and different strategies for addressing them. The strategies include advanced technologies, examples of how and where they have been applied, their potential advantages and disadvantages and how each might fit into an existing treatment strategy and contribute to a utility’s water quality goals.



9:30am - 10:15am

Designing for BioMag®

Ray Busch1, Nigel Beaton2, Steve Flett3, Andy McCaskill4, Brett Woods5

1City of Klamath Falls; 2Carollo Engineers, Inc.; 3Stantec / Slayden Constructors; 4HDR, Inc.; 5Evoqua Water Technologies;

Carollo Engineers, Inc., recently completed the design of a new BioMag® system at the Spring Street Sewage Treatment Plant (STP) in Klamath Falls, Oregon. The BioMag® system is intended to minimize the bioreactor footprint and associated capital costs required to reliably meet more stringent nutrient requirements without the use of primary clarification. Once constructed, this would be the first installation of a BioMag system anywhere on the West Coast.

In the BioMag® system, active biomass in the secondary process is bound to denser magnetite granules suspended in the mixed liquor, which allows for a higher biomass concentration than in a conventional activated sludge process, as well as more rapid settling of suspended solids during the clarification process. The increased concentration of active biomass and improved settling allows for enhanced nutrient removal with minimal reactor volumes. The biologically inert magnetite granules are recovered from waste sludge via rotating magnetic drum separators and fed back into the secondary treatment process.

This presentation will discuss key challenges, considerations, and solutions identified during the process of designing a BioMag® system at the Spring Street STP, including:

  • Designing the magnetite recovery facility to maximize magnetite recovery rates and minimize costs, including by recovering magnetite from secondary scum and avoiding sending any internal plant recycle flows containing magnetite to the head of the plant.
  • Building a brand-new second bioreactor to operate in series with an existing aeration basin.
  • Modifying existing facilities and aging infrastructure for this new system, including repurposing pumps, piping, and equipment; greatly expanding internal recycle flow capacity, and providing additional process redundancy.
  • Keeping ballasted biosolids suspended throughout the treatment process through strategic placement of mixers, diffusers, and valves; ensuring sufficient air flow to final zones of aeration basins to prevent sedimentation, and providing a suction header mechanism in the secondary clarifiers capable of removing magnetite.


 
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