Septage receiving unit contributes to green energy plan

Problem

 The Silicon Valley Clean Water facility in Redwood City, California, serves more than 220,000 people and businesses. Its grease receiving facility faced challenges in receiving and processing grease off-loaded by haulers. Lack of proper screening and removal of contaminants resulted in frequent cleaning of receiving pits, digesters and transfer pipes.

Solution

 The facility pilot tested and then chose a FOG BEAST 1200 receiving and screening unit from Enviro-Care. It removes the debris and allows the remaining fats, oils and grease to be directly injected into the digester. Trucks can unload in 15 minutes or less by gravity feed. The system also speeds up washdown of the truck tank and discharge pit before switching from grease to septage, as required by California law.

Result:

The system optimized performance of the receiving station, significantly reduced maintenance, and reduced the frequency of digester cleaning. 224-302-0303; www.enviro-care.com

---

Oxygen injection system answers odor concerns

Problem

 A 9,000-foot-long force main at the Granby RV Park in Granby, Colorado, was going septic, causing a huge odor problem in a pristine area 30 miles south of Rocky Mountain National Park. In the mountain location, frigid weather sometimes made it difficult for field technicians to work on issues. There were plans for a 300-unit residential development nearby, making odor reduction all the more important.

Solution

 The FORSe oxygen injection system with remote digital telemetry (Anue Water Technologies) was tested for six months and ultimately chosen. It replaces chemical treatment and related operating requirements. The system has capability to inject ozone or a combination of oxygen and ozone. The remote digital telemetry makes it safe and easy for operators to monitor and control dissolved oxygen levels. Technicians at Anue Water can also log in and monitor.

Result:

The system eliminated the odors, bringing hydrogen sulfide levels nearly to zero. The system is paying for itself in chemical and operating cost savings. Operators can monitor and control remotely, important during winter and under the COVID-19 pandemic. 760-727-2683 www.anuewater.com

---

Venturi aeration keeps odors at bay

Problem

 The Delano and Reedley wastewater treatment plants in central California needed to store and process biosolids from the secondary clarifiers as part of their expansions. The biosolids were to be sent to three uncovered holding tanks (110,000 gallons each) to thicken before dewatering by centrifuges. The tanks had to be kept from going septic to prevent odors and avoid operational issues downstream.

Solution

 Each holding tank was equipped with a venturi aeration system consisting of an injector (Mazzei Injector Co.) and a chopper pump, both installed outside the tank.  The systems can operate in a single-pass configuration drawing directly from the clarifiers or as a recirculation configuration drawing from the sludge holding tanks. Each can run continuously or can be shut off for extended periods.

Result: 

The systems provide flexibility to optimize the process. The Delano plant aerates the sludge as it enters the tank; the aeration system is turned for decanting. The Reedley plant constantly aerates and mixes the tank to prevent settling of solids. Due to the injectors’ lack of small orifices and sharp edges, there has been no plugging and no maintenance on the injectors since startup. The biosolids are sent to farmland or to a composting facility. 661-363-6500; www.mazzei.net

---

Headworks upgrade retrofits existing grit chambers and second-stage equipment

Problem

 The Dallas Water Utilities’ Southside Wastewater Treatment Plant headworks included four 30 mgd forced vortex grit chambers that had been in operation more than 17 years. The utility sought to improve grit removal efficiency through augmentation of the existing scheme or replacement of the grit removal system.

Solution

 The utility worked with Smith & Loveless to optimize the primary grit chamber devices and the second-stage grit dewatering and classifying equipment, instead of building a new headworks facility. Cutting-edge analysis, retrofits and factory and field testing of equipment were applied as part of the evaluation and trial. The utility and engineers worked with the manufacturer to achieve the desired results without the full capital expense of a large grit system overhaul.

Result:

 Project goals were realized without building a new facility. The upgrade improved performance, yielding more than 95% removal of grit particles down to 100 microns, while reducing capital and maintenance costs. 800-898-9122; www.smithandloveless.com

---

Finnish sewage plant reduces operating costs

Problem

 The Seinäjoki sewage treatment plant in Finland is designed for 100,000 inhabitants and operates at 90% capacity. However, the plant also receives wastewater from industries including a large dairy, which produces wastewater higher in fats.

Solution

 The company replaced its existing decanter centrifuge with a new decanter centrifuge from Flottweg Separation Technology. Juha Korpi, plant manager, observes, “Good results were obtained in nationwide tests, so the decision was not difficult.”

Result:

The plant reduced its sludge treatment costs by 25%. “We are very happy with the Flottweg machine,” says Korpi. “The commissioning went very smoothly, and the delivery took place on schedule. The machine’s high performance enables us to amortize the investment within approximately two years.” 859-448-2331; www.flottweg.net

---

Water reclamation plant conveying pebble lime pneumatically ends elbow failure

Problem

 The Upper Occoquan Water Reclamation Plant in Centreville, Virginia, reclaims over 30 mgd. Its chemical treatment system relies on pebble lime that raises pH to levels at which phosphorus can be removed. The lime is conveyed pneumatically to six indoor silos during off-loading, but it wore through pipe elbow walls due to its 3%-4% grit content and high conveying velocities. “It’s very difficult for us to replace an elbow,” says Robert Forgione, director of operations and maintenance. “The elbows at ground level are not easily accessed and the ones on top of the silos are four stories up. It’s a safety and a cost concern.”

Solution

 Forgione chose Smart Elbow deflection elbows from HammerTek. The elbow has a spherical chamber that protrudes slightly beyond the 90- or 45-

degree flow path, causing a loose ball of material to rotate slowly in the same direction as the air stream that powers it, gently deflecting incoming material around the bend. The ball gradually releases material in a first-in, first-out progression. Five 45-degree, 4-inch-diameter elbows were installed where the trucks off-load lime, and twelve 90-degree, 4-inch-diameter elbows were installed at the tops of the silos. A custom alloy was specified based on characteristics of the pebble lime and the length and velocity of the pneumatic conveying system. 

Result:

The elbows have been in place for more than 16 years without a blowout. “With the Smart Elbow deflection elbow, we’ve eliminated the primary source of lime dust along with the hazardous conditions it creates,” Forgione says. Maintenance and labor costs have been reduced, safety and air quality have been upgraded, and the buildings are visibly cleaner. 800-505-9665; www.hammertek.com

---

Drying system helps city lower costs

Problem

 The City of Buffalo, Minnesota, faced rising biosolids handling costs, odor issues and an increase in plant capacity with an increase in population from 15,000 to 30,000 by 2025. The city had to meet U.S. EPA 503 Class A standards in a limited site footprint.

Solution

 Veolia’s BioCon ERS dewaters biosolids with thermal drying. Dewatered cake is pumped from a bin into the dryer cabinet through oscillating depositors that extrude thin ribbons through nozzles onto a slowly moving belt. The ribbons provide a large surface area for efficient drying at temperatures lower than a conventional oven (less than 350 degrees F). Heat is transferred to the biosolids by circulating air between heat exchangers and the ribbons. Moist air is continuously extracted air from the dryer, transferred through a condenser, and fed back to the dryer. The temperature decreases as the solids dry. Screw conveyers transport the material from the dryer to a solids hopper for use as fuel in the energy recovery system.

Result:

 The plant increased its capacity to 1,850 tons of dry biosolids per year. The energy recovery system provides over 80% of heat for the dryer from renewable fuels. The dryer reduces biosolids volume by 95%. The solution, executed in a small footprint, contains odor and meets Class A requirements while reducing thermal energy required by 70%-80%. 919-677-8310; www.veoliawatertech.com

---

Dredge system helps crew clear lagoons

Problem

 The wastewater lagoons in Philipsburg, Montana, had not been dredged for 40 years and were half full of biosolids. The two 6-acre, 5-foot-deep lagoons were built in 1961. Public works director Sam Dennis and operators decided to dredge the primary lagoon. 

Solution

 The town rented a Crisafulli FLUMP with pivoting traverse system and 500 feet of floating pipe. The crew dredged the lagoon for six weeks. “The dredge with the pivoting traverse system worked really well and did what was promised,” says Dennis. The system accelerates dredging by enabling the operator to dredge, pivot, and dredge again. Pioneer Technical Services surveyed elevations, provided advice on chemical inputs and pipe sizing, and assisted in compliance with Department of Environmental Quality regulations. 

Result:

 The crew added polymers to the biosolids arriving at the lagoon bank and used a manifold system to direct the flows into 20 lined geobags 45 feet wide and 100 feet long. The bags are held in a 3-acre containment.  Water is recycled as it drains from the bags back into the lagoon. 800-442-7867; www.crisafullipumps.com 

---

Centrifuges upgraded to increase life span

Problem

 Two old 44-inch screen bowl centrifuges were possibly in need of refurbishing. They operated 24/7 in a fine-coal-recovery process requiring moistures between 15% and 23%.

Solution

The centrifuges were sent to Centrisys/CNP for a condition evaluation. Using SOLIDWORKS to engineer and retrofit the older planetary gearbox to a smaller, a more efficient Viscotherm Rotodiff backdrive will prolong the centrifuges’ working life and achieve the necessary results. The backdrive is proven to produce the dry cake needed for the coal recovery process.

Result:

The system optimizes solids retention time (the time the solids stay in the centrifuge under G-force). This reduces the coal fines’ moisture. 262-654-6006; www.centrisys-cnp.com

---

Water reclamation facility utilizes screw press trailers for temporary dewatering

Problem

 The Tres Rios Water Reclamation Facility in Tucson, Arizona, needed to take down its entire centrifuge dewatering facility for contractors to install a second cake pump. Operators had to find a reliable way to divert flow from the entire 30 mgd facility.

Solution

 Schwing Bioset provided FSP1103 and FSP703 screw press dewatering trailers. Thickened biosolids were fed from the anaerobic digester to both presses. Once the feed was connected via camlock hoses, power connected to the trailer, and the drainlines hooked up, the screw presses were ready to run. Technicians dialed in the polymer dose, screw press floc tank pressure, screw rotation speed and discharge cone pressure to optimize performance. 

Result:

The screw presses provided reliable dewatering during the few weeks while the cake pump was installed. The presses produced cake and filtrate quality near that of the plant’s existing centrifuges, an average of 17% cake solids, while running near design capacity. 715-247-3433; www.schwingbioset.com