CH2M HILL wastewater experts will be attending and presenting at the Water Environment Federation’s annual 2014 Residuals and Biosolids Conference in Austin, TX this week. David Oerke shares a case study with Green Bay, WI on selecting a sustainable dewatering system.

By: David Oerke, CH2M HILL Residuals Resource Recovery Global Technology Leader

David Oerke will present the paper, “Applying European Experience to Screen and Select a Sustainable Dewatering System for Green Bay”, co-authored by CH2M HILL’s Peter Burrowes and Bill Desing and Northeast Wisconsin, Green Bay’s Bill Angoli, Bruce Bartel, and Nathan Qualls, during the Water Environment Federation’s 2014 Residuals and Biosolids conference in Austin, TX, on Monday, May 19, at 1:30 p.m.

Click here for a complete schedule of CH2M HILL’s conference participation.

This week, representatives from CH2M HILL’s Residuals Resource Recovery group are in Austin, Texas to meet with thought leaders, practitioners, researchers, and clients at the Water Environment Federation’s (WEF) annual 2014 Residuals and Biosolids conference. I look forward to attending this event each year, and especially this year, as I recently took on a new role as CH2M HILL’s Technology Leader for our Residuals Resource Recovery group. It has been a pleasure working with our team of technologists to solve some of our clients’ most challenging issues. We have several presentations and workshops prepared to share and learn the latest technologies in the industry.

Over the last several years, we have seen a trend with more utilities investing in resource recovery technologies as a way to increase optimization of their assets and meet sustainability and environmental compliance standards. Green Bay Metropolitan Sewerage District (GBMSD) is one of the clients we have been working with to address these stricter environmental compliance standards and the solids waste capacity issues they face, only exacerbated by their aging assets.

Rather than dwelling on these challenges, we partnered with GBMSD to identify solutions that would allow them to continue collecting, treating, and reclaiming approximately 38 million gallons of wastewater daily by developing a Solids Management Facility Plan. The plan, known as the Northeast Wisconsin (NEW) Resource Recovery and Electrical Energy or R2E2 Project, covered a planning horizon to 2035 and includes building two anaerobic digesters that will break down biodegradable materials from human, household, and industrial waste.

When the initial plan was developed in 2011, it was assumed that high-solids centrifuges would be used for dewatering; however, during the design phase, we considered alternative methods to ensure GBMSD was able to achieve cake solids concentration of at least 27% in order to produce a material that would combust autogenously (that is, no supplemental fuel would be needed in the fluid bed incinerator following the dewatering process).

However, since the completion of the initial plan, new technologies have been identified that can be used for effectively dewatering anaerobically digested biosolids, including high-solids centrifuges combined with belt and disc dryers, hydraulic piston presses, and thermal vacuum dewatering/dehydration units. By looking at the monetary and non-monetary benefits of the various technologies, such as ease of operation, space requirements, installed capital equipment cost estimates, operation and maintenance costs, and net present worth estimates, the recommendation was made for GBMSD to use three high solids centrifuges with disc dryers. This option yielded several benefits, including:

  • One of the lowest present worth costs
  • Lowest capital cost
  • Autogenous incineration
  • 100% of thermal dryer energy provided by waste heat
  • Minimal footprint – compact, enclosed and proven facilities

The Hamburg WWTP is “energy neutral” and does not buy energy from the grid. It was a good model of what Green Bay’s goal is for the R2E2 Project.

In January, CH2M HILL and NEW water staff visited several facilities in Europe, which have incorporated centrifuges with disc dryers and newer resource recovery methods, to benchmark alternatives and determine what would be the best option for Green Bay. These tours provided us with a deeper understanding of how the technology works. The following lessons learned were included in the revised design plan for Green Bay:

  • Centrifuges and disc dryer provides greater flexibility to achieve autogenous combustion, especially with variable sludge characteristics caused by high strength wastes to the anaerobic digesters
  •  Disc dryers are reliable, easy to operate and required a manageable level of maintenance
  • Progressing cavity cake pumps provide cleaner operation, more redundancy, better maintenance access, and more efficient use of one overhead crane for maintenance of centrifuge and disc dryer
  • Hydraulically driven reciprocating piston pumps are a good option for cake sludge pumping from drier to incinerator

I look forward to sharing more about our findings during my presentation on Monday, May 19.

Learn more about the R2E2 project in CH2M HILL’s Peter Burrowes blog, “Biosolids and Resource Recovery Value Strategy.”

David Oerke is a nationally-recognized biosolids processing specialist and Global Technology Leader of the Residuals Resource Recovery Group with CH2M HILL, with more than 34 years of experience. Dave has been involved in the evaluation, design, startup and optimization of more than 100 thickening and dewatering units throughout the U.S. He was the Senior Technology Consultant on the Green Bay R2E2 project. Mr. Oerke was a principal author and reviewer of the thickening stabilization and dewatering chapters of the 2012 WEF/WERF/EPA Solids Process Design and Management Manual and the 2012 WEF Manual of Practice 8.