This quip refers to the next phase of operational start-up requiring initial seeding of the anaerobic digester. The anaerobic digestion process harnesses natural bacteria to treat wastewater biosolids. At WSSC, these biosolids will first flow through the new thermal hydrolysis process (THP) followed by the anaerobic digesters (ADs). When initially commissioned, anaerobic digestion facilities require seeding with biologically active sludge to produce the population of methanogenic and acid-forming bacteria required for the anaerobic digestion process to work effectively. To accelerate the process of acclimation of the bacteria to the new environment, the preference is to seed with biologically active sludge that has gone through similar processes, in this case THP.

DC Water, located less than 15 miles from the WSSC Piscataway WRRF, also incorporated THP and anaerobic digestion at their Blue Plains AWWTP facility with the Main Process Train project, which was completed by PC in 2015. As a fully established facility, DC Water was happy to provide “bugs” that are “trained” to jump start the anaerobic digestion process. Beginning last night, tanker trucks containing this biologically active sludge began rolling into WSSC’s bioenergy facility and this sharing of special resources will continue over the next five days. Click here to watch last night’s excitement.

Once the seeding process is complete, initiation of full-time operation of the THP processes will begin. In preparation for this, the WSSC operations team has concurrently begun pre-dewatering activities, processing the indigenous biosolids produced by the Piscataway WRRF and storing the dewatered cake in the new cake storage silos. The volume of biosolids processed will ramp up from 4 dry tons per day to 16 dry tons per day over a 30-day period. Once this is complete, the facility will operate for another 60 days solely processing Piscataway WRRF biosolids before bringing biosolids from WSSC’s four other facilities to the site for processing through the new systems.

The Piscataway WRRF Bioenergy Project utilizes cutting-edge green technology to transform the way WSSC handles biosolids from all six of their water resource recovery facilities, significantly reducing the volume and creating Class A biosolids. The process will also reduce operating costs by more than $3 million per year and reduce greenhouse gas emissions by 15% by capturing and cleaning the digester gas to help power the facility through the CHP facility.

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A key component of the thermal hydrolysis process (THP), the cooling heat exchangers (CHEX), are tube-style heat exchangers that lower the sludge temperature leaving the thermal hydrolysis process from 194°F to 100°F prior to arrival at the anaerobic digestion tanks.

These particular units were manufactured with specialty superalloy piping, sourced out of China, to prevent microbial induced corrosion. The PC team released the units for fabrication in December 2020 and diligently tracked their fabrication and delivery to the project site. On Monday, the long journey officially ended. After a trip across the Pacific to Seattle and then across the country to Maryland, the equipment was delicately set on the waiting concrete pads.

With the CHEX units, each weighing nearly 25,000 pounds, now set in their final position, work will proceed on the UV and Odor Control Facility as well as piping interconnecting the THP, the CHEX units, and the anaerobic digesters.

The post The Slow Boat from China Arrives at Piscataway WRRF appeared first on PC Construction.

The WSSC Piscataway Bio-Energy project reached another key milestone this month with the erection of the 12,400-square-foot solids building. In just eight days, PC’s partner, Nitterhouse Concrete, erected the 43 precast exterior wall panels and 14 double tee roof components that form the building. The building will house both the pre- and post-dewatering presses, chemical storage tanks, a laboratory, and an electrical room. PC Construction set the belt filter presses in place prior to the erection of the building to streamline the installation process.

The post Solids Building Erected at the Piscataway WRRF Using Precast Wall Panels appeared first on PC Construction.

The excitement on site was visible when the first truck delivering the Cambi unit arrived at the Piscataway site. Over the course of three days, nine trucks arrived delivering the modular Cambi components for installation by the PC team.

This was not PC’s first Cambi installation. The onsite team had the experience and lessons learned from installing the largest Cambi system in the world at DC Water’s Blue Plains AWWTP. The benefits of the planning process was evident as the trucks arrived in a set sequence and the modular equipment was offloaded directly to the awaiting concrete pad. Always with an eye on safety, PC’s team first erected the four smaller reactor tanks, followed by the feed pump skid, the flash tank and pulper tank and finally the walkway platforms and piping connecting the system.

This fall, a secondary pulper and feed tank will be delivered and installed. These components will ensure continuous operation during maintenance and inspection periods and will be the first Cambi system in the world with this additional operational capacity.

While the delivery and installation of Cambi was a key milestone, several other components have continued to progress. Dutchland has made significant progress on the deammonification tanks. After pouring the three base slabs, each sitting on a different elevation, they began erecting the 89 wall panels that form the tank as well as the 30 additional beam, walkway, roof and floor panels. With everything erected, large steel tendons were pulled through the panels and tensioned to achieve structural integrity and watertightness. The tanks are now ready for testing.

The PC team has also completed the cake storage pad facility, which will house the final Class A biosolids before it is hauled offsite. Work continues on the foundation for the cake receiving facility where trucks from other WSSC sites will deliver sludge to be processed through the THP facility.

DN Tanks is nearing completion on the two 1.5-million-gallon digester tanks. Foundations for the CHP, gas cleaning and storage facilities are being prepped and poured in anticipation of the equipment delivery.

Looking forward, Nitterhouse will soon be back on site erecting the precast concrete wall and roof system for the Solids building.

Stay tuned for updates as the Piscataway landscape continues to change!

Check out the progress:

The post The Cambi THP System Arrives at WSSC Piscataway Bio-Energy Project appeared first on PC Construction.

PC’s self-perform team has set the seven belt filter presses at what will be the solids building housing all the pre- and post-dewatering activity for the facility. These are just a few of the large pieces of equipment being set into place prior to erecting the pre-cast concrete panels that will form this more than 16,000-square-foot building.

Nitterhouse Concrete has started to place the precast panels on several buildings including the chemical storage building, sidestream pump station and gas storage blower building. They will also begin erecting the solids building once PC completes the equipment installation.

Work continues on the two 1.5-million-gallon anaerobic digesters, including the massive cast-in-place concrete domes. Work is being completed on the structural integrity of the tanks and making them watertight through the process of wrapping and shotcreting the tanks.

The sidestream treatment tanks are starting to take shape as well. Dutchland’s team is onsite placing the foundations for the pre-cast post-tensioned tanks that will be erected in June.

Additionally, the cake receiving vault has been completed in preparation for the cake hoppers and cake storage bins. Foundations are being prepped for the generators, boilers and gas storage facility.

While so much has happened in the past month, the flurry of activity won’t end anytime soon. Stay tuned for more updates coming soon!

The post Big Changes at WSSC Piscataway Bio-Energy Project appeared first on PC Construction.

PC has partnered with DN Tanks to complete these circular prestressed concrete tanks. Each tank consists of 17 individual panels that are 50 feet tall and vary in width to create an approximately 78-foot-diameter tank. The largest panel weighed in at more than 30 tons.

The panels were cast on site in eight casting beds, four near each tank location. Once the casting was complete, each bed contained four or five stacked panels. Using a 500-ton crane, the panels were lifted from their beds and flown into place. Each tank took only two days to complete.

Now that the panels are in place, work can begin on the installation of the shoring and formwork to cast the digester domes. The tank joints still need to be infilled and the tanks wrapped with prestressing wire and coated with shotcrete. The tanks are expected to be fully constructed in Spring 2021.

The $271 million bio-energy project will use thermal hydrolysis process (THP) and anaerobic digestion to treat the biosolids and a sidestream process to treat the resulting effluent. The project is also designed to capture and clean the digester gas to feed back to the Washington Gas pipeline and/or to be used in the new CHP facility to generate electricity and steam to feed the THP process. The entire project is expected to be complete by the fall of 2024.

The post Stonehenge Recreated at WSSC’s Piscataway WRRF appeared first on PC Construction.

In April, the WSSC Water Commissioners approved Phase 2 funding, allowing PC to begin construction of the design-build Piscataway WRRF Bio-Energy Project in Accokeek, Maryland. The $228 million for Phase 2 brings the total investment in the green-energy project to $270 million and marks the final funding needed to construct WSSC Water’s largest and most technologically advanced project. At the heart of the project is how WSSC Water handles biosolids produced by the wastewater treatment process.

This new bio-energy facility will use thermal hydrolysis process (THP) and anaerobic digestion to treat the biosolids and a sidestream process to treat the nutrient rich effluent from the dewatering process. The project is also designed to capture and clean the digester gas to feed back to the Washington Gas pipeline and/or to be used in the new CHP facility to generate electricity and steam to feed the THP process. Surplus electricity generated can also be fed back to the electrical grid.

The facility has been designed to meet WSSC Water’s anticipated 2040 capacity with the THP’s capacity of 88 dry tons per day. The two digesters have a combined volume/capacity of more than 3 million gallons.

In addition to the major process facilities, the project also includes gravity thickening, a cake receiving facility that will accept solids from WSSC Water’s other WRRF’s, pre- and post-dewatering facilities, digested sludge storage, odor control facilities, a post-dewatering cake storage facility, and a gas storage and cleaning facilities.

Using cutting-edge “green” technology, the new facility will significantly reduce the amount of biosolids resulting from the treatment process, thus reducing costs to haul and dispose of the product. The remaining biosolids will be significantly cleaner (Class A), making the disposal process much easier and allowing the final product to be suitable for sale and distribution as fertilizer. This new process will reduce operating costs and is anticipated to save WSSC Water customers more than $3 million per year. Additionally, by recovering the digester gas and using it to help run the facility, WSSC Water will reduce their greenhouse gas emissions by 15 percent.

PC is underway with Phase 2 work as we continue toward completion of Phase 1 early work activities, referred to as the enabling work package, which includes demolition of existing facilities, hazardous materials abatement, site preparation and site utilities enhancements. This Phase 1 work is about 75% complete with most major demolition nearing completion. All work associated with the Phase 1 site preparation is scheduled to be complete in late August 2020.

To complete this project, PC is teaming with leaders in these specialized facilities – Stantec and Hazen and Sawyer. This winning combination brings together PC’s construction experience – including the largest THP facility in the world – with Stantec’s history of designing nearly half of the world’s THP facilities and Hazen and Sawyer’s biosolids and sidestream treatment expertise.

We are excited to collaborate with WSSC to move this environmentally significant project to successful completion. Stay tuned for more updates as this project progresses.

Photos: A look at the Piscataway WRRF site prior to construction (top) and currently (bottom).

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