How a polymer dosing system can make or break your sludge dewatering process.

DATE POSTED: February 28, 2022


Polymer dosing systems for dewatering.

Polymer is the secret ingredient for maximizing dewatering and achieving high quality filtrate from the Geotube® containers in our Bishop Solids Management Solution. But selecting the right polymer is not enough to get the best results.

Precise dosing is critical to ensure that the operation runs smoothly and that dewatering occurs as required without any unfortunate incidents. Not enough polymer will result in poor dewatering performance, insufficient solids retention and low-quality filtrate. Too much polymer can clog the pores of the Geotube container and prevent water from being released. In such a case, the bag is no longer usable and could burst if operators fail to notice the problem and overfill the container.

VEPAS Polymer Dosing System
VEPAS Polymer Dosing System

Bishop Water’s VEPAS™ (Venturi Emulsion Polymer Activation System) is an easy-to-use and affordable system that mixes and fully activates liquid polymer emulsions in a single step, adds the precise dose directly into the sludge feed line and eliminates the need for messy mechanical mixers and bulky aging tanks.

Compact size, smart controls

VEPAS polymer dosing can be configured to monitor sludge flow and consistency using flow and mass meters, enabling it to automatically adjust polymer dose to achieve the optimum mix and dewatering properties. These smart controls also communicate with 4-20 mA inputs, which enables VEPAS to be integrated to the plant SCADA system and configured to automatically begin operating when sludge pumps are activated.

The compact, skid-mounted VEPAS occupies a fraction of the space of a conventional mechanical polymer system and can be quickly installed for new or retrofit applications in treatment plants, mobile trailers, or utility buildings.

Our Bishop Solids Management Solution with Geotube® dewatering technology and VEPAS is an integrated solution that can work with any wastewater treatment plant or industrial process to collect and dewater slurry materials. This enables any facility to build a compact, rapid dewatering solution that saves time, reduces operating costs, and simplifies sludge management.

A simple test can help us determine precise dosing of the polymer selected for your site and build a skid-mounted system that can be installed quickly. Once installed, our team can provide onsite training and are easily accessible to assist with ongoing maintenance and support.

Geotextile sludge management system provides long-term savings for North Rustico WWTF

Read a recent article that shows how our Bishop Solids Management Solution and VEPAS enabled the North Rustico WWTF to simplify sludge handling and significantly reduce operating costs.

Learn more about VEPAS.

Contact us to discuss a Bishop Solids Management Solution or VEPAS for your treatment plant.

Bishop Solids Management Solution — Dewatering for all occasions

DATE POSTED: September 3, 2021


We’ve dewatered a lot of stuff over the years.

Everything from ordinary wastewater sludge and excess soil from construction sites, to noxious slurries containing really smelly organics, industrial process wastewater, and even low-level radioactive materials. 

Over that time, we’ve learned a couple of things.

First, that our Bishop Solids Management Solution is extremely versatile. It can be used to collect, dewater and consolidate almost any type of slurry material. 

The second thing is that our Solids Management Solution is one of the most efficient and cost-effective ways to get the job done. Our passive, gravity-based dewatering system is often compared against more complex, energy-intensive processes such as centrifuges, belt presses, and filter presses. In most cases, we can demonstrate that the Bishop Solids Management Solution can achieve similar or better dewatering performance at a lower cost and using less energy than alternatives. 

The Bishop Solids Management Solution not only retains and consolidates solids, it also provides water treatment—greatly reducing TSS, nutrients and other contaminants of concern. This can be an effective pretreatment step or, depending on regulatory requirements, the filtrate can meet standards for discharge to the environment or even reuse in non-potable applications. 

Start with a simple sludge test

polymer selection

Our process starts by obtaining a sample of the sludge and performing a dewatering test. The test reveals a lot of important information such as the solids concentration of the slurry, the polymer that will provide the best dewatering performance and how much water can potentially be removed. 

We also need to know the approximate volume of sludge to be dewatered. This information, combined with the results from the dewatering test enables our team to calculate the number of Geotube® dewatering containers that will be needed, how large the dewatering cell will be, how much polymer will be needed and of course, how long the project will take. 

What’s your solids management or dewatering challenge?

We have the solution.


Contact us to discuss your solids management needs and learn how simple, low-energy solutions from Bishop Water can help. 

Learn more about the Bishop Solids Management Solution. 

Simplifying arsenic sludge management at a gold mine

DATE POSTED: August 19, 2021


Arsenic sludge management

Arsenic-laden groundwater continually infiltrates the shafts of a gold mine in Western Canada. As it’s pumped out, an onsite treatment system removes the arsenic to produce effluent that can be safely released. But the system also produces large volumes of sludge—about 1,900 litres every 45 minutes. The sludge was a challenge for the site’s existing media filtration system and a faster, more reliable and more cost-effective solution was needed. Learn how the Bishop Solids Management Solution provided a simple, low-energy solution that achieves dewatering, filtration and containment in a single step.

Case study: Lagoon sludge removal provides affordable solution for algae and H2S issues

DATE POSTED: May 25, 2021


  • Lagoon sludge removal and dewatering
  • Bishop Solids Management Solution 
  • O’Leary Wastewater Treatment Facility, O’Leary, PEI, Canada

The challenge: Algae blooms and corrosive gases caused by sludge accumulation

Sludge accumulation was thought to be causing significant operational challenges for the O’Leary Wastewater Treatment Facility (WWTF), a two-cell lagoon system on the west side of Prince Edward
Island, commissioned in the 1990s. 

O’Leary’s treatment lagoon serves about 800 residents, several businesses and, for a period of time, was also receiving wastewater from a potato processing plant. 

Sludge maps are an important step in planning and executing lagoon cleanouts. WSP’s map of the O’Leary lagoon revealed significant accumulation.

The lagoons were experiencing serious blooms of blue-green algae during the summer months and exceedances of TSS, BOD and coliform bacteria in treated effluent. Hydrogen sulfide (H2S) gas, which was also attributed to the algae and sludge, was building up in a below-grade chamber that housed the plant’s UV disinfection system.   

Not only was the gas accumulation a hazard for operators, but it caused corrosion that damaged ductile iron pipes, an electrical panel and the plant’s UV system. 

Operators also saw “islands of sludge” periodically rise out of the water before bursting and releasing clouds of methane and H2S gases.

The solution: Dredging and passive dewatering meets regulatory and budget requirements 

In 2019, the Town of O’Leary began working with engineering consultants WSP to repair the damage to the UV system, alleviate the algae blooms and end the release of corrosive gases from the lagoon. 

WSP began with a comprehensive sludge survey, obtaining sludge depth measurements from several locations in each of the lagoons. 

The results revealed that despite their large area, the lagoons are relatively shallow, with a maximum depth of only 5 ft (1.5 m). Each cell had accumulated about 1.5 to 2 ft (0.45 to 0.6 m) of sludge, which significantly reduced their ability to remove nutrients and settle out solids. 

The team evaluated several options and awarded the project to AJL Contracting and Bishop Water Technologies to desludge the lagoon and dewater removed solids with the Bishop Solids Management Solution. This simple, low-energy system uses Geotube® containers, optimal polymers and gravity to collect, dewater and consolidate dredged sludge. 

Dredging the lagoon enabled it to remain in operation while sludge removal occurred and also complied with a provincial regulation that prohibits tracked heavy equipment from operating in lagoons with clay liners. 

The project began in the summer of 2020, with the construction of a lined laydown area designed to accommodate a layer of three Geotube containers 85 ft in circumference and 114 ft in length (26 x 34.7m) and a second layer of two 95 x 100 ft (29 x 30.5m) containers that would be laid on top. This stacking arrangement minimizes the footprint and cost of the dewatering cell. 

The results: No algae, no gases, no rush to haul away solids

Dredged sludge was first pumped through a 0.6 inch (15 mm) screen to remove debris, trash and improve the quality of the final dewatered biosolids for land application. 

From the screening plant, the sludge was pumped to the Geotube containers. Bishop Water’s VEPAS™ (Venturi Emulsion Polymer Activation System) added and mixed polymer directly in the feed line, eliminating the need for polymer aging and mix tanks. 

The Bishop Solids Management Solution accepts and dewaters solids as quickly as the dredge can pump, dramatically outperforming centrifuges or belt presses for speed and energy efficiency. Low-TSS filtrate released from the microscopic pores of the Geotube container was directed by gravity to cell two. 

Technicians continually monitored polymer performance and dose rates to ensure optimal dewatering and retention of contaminants. Daily sampling showed that the system was achieving about 20% solids
concentration after just a few hours of dewatering.  

The Bishop Solids Management Solution used a two-layer,  stacked arrangement of Geotube dewatering containers to  minimize the footprint and cost of the dewatering cell.

Desludging of cell one was completed in about four weeks. Two more weeks of sludge removal filled the first layer of Geotube containers to capacity and technicians stacked a new container on top of the others. 

One more week of dredging and pumping completed the project.  The total volume of wet sludge removed was 26,480 m3, which corresponds to 872 bone dry tonnes. 

A major advantage of Geotube containment is that the solids can remain at the site for months or even years, allowing ample time for the town to find a suitable location for land application and arrange funding for hauling. Throughout that time, passive dewatering will continue further consolidating the material. 

A seasonal freeze-thaw cycle also significantly improves dewatering, potentially elevating the solids concentration of the dredged material to 40% or more in this case. 

Since completing the project, operators report that there have been no issues with gas accumulation in the below-grade chamber or blue-green algae growth in the lagoons. 

Learn more about the Bishop Solids Management Solution for lagoon sludge cleanouts. 

Download the case study.

Contact us to discuss your sludge removal and solids management challenges. 

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Partial lagoon cleanouts help balance performance and budgets

DATE POSTED: August 28, 2020


If you’re going to clean out a cell or two at your wastewater lagoon, there are circumstances when a partial cleanout might be the best, fastest way to quickly fix an urgent capacity or performance issue until the lagoon is ready for a full desludging.

Partial cleanouts, using the Bishop Solids Management Solution, can most often be completed while the lagoon remains in operation, so there’s no need to decommission the cell or disrupt the process flow. Bishop Water can quickly diagnose lagoon performance issues caused by excess sludge and determine the volume and locations of sludge that should be removed from the cell. 

Once a plan is ready, the team can mobilise a dredge, its mobile polymer conditioning system and prepare a laydown area for Geotube® containers, are used to collect, dewater and consolidate the solids. Or, if the volume of sludge is small, they can be filled and removed inside 30-yard roll off boxes, making transportation and disposal fast and simple.

Partial sludge cleanouts can also become part of an ongoing lagoon maintenance program to ensure optimum performance. Rather than waiting until sludge accumulation reaches a critical level, lagoon operators or Bishop Water technicians can monitor sludge accumulation in the lagoon and when needed, proactively perform a partial cleanout to maintain an optimized level of performance.

Partial lagoon cleanouts have been used by many lagoon operators to achieve operational and economic benefits including: 

  • Quickly restore lost storage and treatment capacity in the lagoon; 
  • Correct flow issues caused by sludge accumulation that create short-circuiting of lagoon flow and reduced retention time; 
  • Defer the cost of a full lagoon cleanout over an extended period of time; 
  • Maximize the capacity and dewatering of each Geotube® container. Partially filled containers can remain onsite for continued filling at the next cleanout interval. They will experience significant volume reduction between fill intervals, which will reduce the number of containers needed as well as hauling and disposal costs.

Learn more about Bishop Solids Management Solutions for partial lagoon cleanouts. 

Contact us to discuss your lagoon clean out needs. 

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Why does freezing improve Geotube® dewatering performance?

DATE POSTED: February 27, 2020


Geotube containers that are filled late in the year are often left onsite over the winter to experience the dewatering advantages that the freeze-thaw cycle brings. Once the thawing begins, those previously frozen Geotube® containers can give up a lot of water—in some cases up to 50% of their volume.

This dramatic reduction in volume means that the containers can be topped up with additional slurry materials once they are fully thawed. Or, if the solids are destined for disposal, the reduced volume will mean much less material to transport and lower costs for hauling and tipping fees.

Expansion helps with consolidation of solids

Dewatering benefits from the freeze-thaw cycle because water expands as it freezes. The Bishop Solids Management Solution, with Geotube® containers, can attain 15 – 18% solids within a few days of dewatering, but that means there’s still a good amount of water remaining as cold temperatures set in. The formation of ice crystals and the expansion of the water compress the solids and once the thaw occurs, more water is released and the solids are further consolidated.

The results can be quite dramatic. At a recent wastewater lagoon desludging project, our crew filled Geotube® containers to a maximum height of 7.5 feet. The containers were left on site over the winter and after thawing in the spring, the height was reduced almost by half.

Some of our clients that are equipped with a permanent Bishop Solids Management Solution take full advantage of freeze-thaw cycles in their sludge management plans.

Geotextile sludge management system provides long-term savings for North Rustico WWTF

The North Rustico Wastewater Treatment Facility in Prince Edward Island, Canada uses several large Geotube® containers setup outdoors to dewater waste sludge, with a smaller container in a greenhouse that is used during the winter months. The outdoor containers are left to freeze over the winter and can be topped up in the spring once they thaw and release more water. This enables the plant to use Geotube containers for several seasons, replace them less often, and reduce operating costs.

Read the feature article about the North Rustico WWTF in Go With the Flow magazine published by the Atlantic Canada Water and Wastewater Association.


Learn more about Geotube® containers for solids dewatering.

 Contact us with your questions about the Geotube® freeze/thaw/consolidation cycle and to arrange for a dewatering test of your solids.

Dewatering with Geotube® vs belt press – which one wins?

DATE POSTED: August 21, 2019


Gravity or pressure—which is more effective when dewatering wastewater sludge? Both are proven methods to remove water from slurry and produce a cake that can be handled for disposal or land application. But there are several important economic and operational factors to consider before choosing between a Bishop Solids Management Solution (BSMS) that uses passive, gravity-based Geotube® dewatering or a pressure-based mechanical system such as a belt press.  

Cost

There are only four major components to the BSMS — a non-mechanical polymer mixing and activation system, feed pumps, hoses and Geotube® containers. This low-complexity system not only keeps capital costs low, it also requires little electricity for pumps and control equipment. By comparison, a belt press is a complex system that is costly to rent or buy and requires a significant amount of electricity to operate. 

Easy to operate

Mechanical belt press systems typically require full-time staff to monitor and adjust the process, especially if the sludge varies in organic matter concentration and percent solids. The BSMS requires continuous staffing during setup to install the equipment, optimize sludge flow and polymer feed rates, but after that, the system can function largely automatically. Sludge can be pumped continuously and systems can be set up to automatically adjust polymer dose and feed rates according to sludge characteristics. Technicians may only need to monitor the system every few hours.

Dewatering performance  

When dewatering biosolids, both the BSMS and belt presses can achieve about 18-20 percent solids – depending on the characteristics of the sludge and polymer that is used. However, if time and space permit, Geotube® containers can remain at the site to continue dewatering by gravity and potentially achieve 25 percent solids or more. This simple step to further reduce residual mass can help dramatically reduce hauling and disposal costs of the dewatered solids.

Retention of solids and contaminants

The BSMS provides dewatering and containment in a single step. Optimized polymer conditioning helps to retain up to 95% of total suspended solids as well as nutrients, metals and other contaminants. This containment also minimizes or eliminates the potential for spills and operator exposure to odors, pathogens and contaminants. Solids from a belt press, on the other hand, are open to the atmosphere and can potentially expose operators to spills, odors and contact with hazardous material. Additional handling is also needed to move solids from the belt press to a storage or staging area for disposal.

Processing rates

Newly introduced Geotube® Durability Engineered Composites offer even more robustness and abrasion/damage resistance for shoreline projects. This advanced container incorporates a highly UV stabilized crimpled fiber that shields and cushions a woven geosynthetic underneath and also enables sand and soil entrapment so vegetation can easily be established. Watch our future e-news issues for more info. 

*Based on information from: Use of Geotube® dewatering containers in environmental dredging, B.J. Mastin and G.E. Lebster


Learn more about the Bishop Solids Management Solution.

Contact us to discuss your dewatering project and arrange a sludge test.

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Freeze-thaw cycles: bad for roads, but really good for dewatering.

DATE POSTED: April 9, 2019


How does a Bishop Solids Management Solution fare in the wintertime?

For most municipalities, springtime freeze-thaw cycles are a problem, causing damage to roads, bridges and other infrastructure. But for the Bishop Solids Management Solution, with Geotube® containers, freezing and thawing is a natural wonder that provides a tremendous boost to the dewatering process and can help reduce the volume of a container by as much as 50%.

geotube, freeze-thaw

This happens because water expands when it freezes, so the ice crystals that form inside the Geotube® container cause compression of the solids and force more water to be squeezed out. Once the Geotube® container thaws, the water is released and the solids are further consolidated. The best part is that the freeze/thaw/consolidation process happens naturally, costs nothing, and requires no oversight from plant operators.

It’s not unusual to see the volume of a Geotube® container shrink by as much as 50%. This volume reduction frees up space in the bag, and enables it to be refilled with solids— though we recommend that you wait until the Geotube® container is fully thawed before pumping into it again. A full thaw can take several weeks due to the size of the container, but as a general rule, once the ground is free of frost your Geotube® container is ready to accept more solids.

Once the Geotube® container is full again–and if you have space–let it sit over winter and freeze again. In some cases, the dewatering and consolidation may be sufficient to allow you to refill the container again. Some of the sites we service have been using the same Geotube® container for three or four seasons. But even if the container can’t accept more solids, the additional dewatering and volume reduction will help reduce the time and cost of hauling the solids off-site.

Learn more about the Bishop Solids Management Solution for containment and dewatering of solids.

Contact us with your questions about the Geotube® freeze/thaw/consolidation cycle and to arrange a dewatering test of your solids.

 

 

How to redesign septage lagoons to accept more loading in less space

DATE POSTED:


It’s getting harder to find nearby wastewater lagoons that accept septage. Whether a site has limited capacity or is unable to handle high-strength septage, it means many haulers are unable to empty their trucks locally, forcing them to travel farther to reach lagoons that can accept them.

lagoons, geotube, septage, loading

 

A simple, easy-lagoons, geotube, septage, loading to-operate upgrade to wastewater lagoons could enable virtually any site to accept significantly more septage without expanding the lagoon footprint, operate more efficiently and potentially increase revenue from septage disposal.
The Bishop Solids Management Solution enables septage lagoons to make a simple process modification that enables it to accept high-strength waste and more solids without process upset or compromising capacity.
To achieve these benefits, the Bishop Solids Management Solution, with Geotube® containers becomes the septage receiving point instead of the lagoon. Septage is pumped directly from the truck, or from a holding tank, to a Geotube®lagoon, loading, reduced footprint container, which provides both containment and dewatering of the septage.

 

lagoons, geotube, septage, loading As the septage is pumped into the container, it first passes through a 1/2-inch bar screen to separate unwanted solids such as trash and other debris. Then, a specially selected polymer is added, which enables the solids to begin dewatering and filtrate to flow through the container’s tiny pores almost immediately. This filtrate is collected by a non-permeable membrane and directed into the adjacent treatment lagoon.

To cope with the high levels of contaminants and nutrients that this filtrate may contain, Bishop Water can also retrofit a lagoon with its BioCord Reactors, a self-regulating, low-energy technology to achieve enhanced biological removal of nutrients and BOD. The modular reactors provide a high density, vertically oriented surface area—like a condominium for bacteria—that functions as an ideal medium on which to establish a stable, concentrated biofilm. This robust population of microorganisms is resistant to high hydraulic and organic loadings and dramatically improves the performance of the lagoon under normal and upset conditions.

 

Learn more about using Bishop Water’s solids management solution at a WTP.

Read our recent article in OOWA Onsite Magazine.

Contact us to discuss affordable process upgrades to your septage lagoon.

 

 

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A simple, affordable solution for high TSS washwater

DATE POSTED: February 1, 2019


Ontario growers prove Bishop Solids Handling System is ideal to reduce TSS in washwater

Washing vegetables can be a dirty job that produces a tough to treat waste stream of soil particles, vegetable debris and nutrients such as nitrogen and phosphorus. In many cases, farms must treat water to restore clarity and remove nutrients before discharge to a receiving body.

This is typically done using settling ponds, but for farmers in Ontario’s Holland Marsh, the soil is fine-textured and peat-like with low specific gravity that does not readily settle in conventional treatment ponds.

Bishop Water was invited by the Holland Marsh Growers’ Association (HMGA) to assist in developing a simple, affordable solution for washwater treatment after the group learned about the company’s success and experience in agricultural applications. Prior to this, the HMGA was experimenting with another type of non-woven fabric filter bags, but the bags were experiencing clogs, ruptures and poor solids retention — they were unable to reduce TSS to an acceptable level.

Water samples from the Bishop Solids Management Solution show wash water (left), one minute after the addition of coagulant (centre) and treated filtrate from the Geotube® container (right.)

Bishop Water installed a pilot system of its Solids Handling Solution. In this case, two 25-foot (7.6-metre) Geotube® containers were set up near the farm’s settling pond. Washwater was pumped at a rate of 350L (92.5 US gallons) per minute, treated with polymer to aggregate the small soil particles and then directed to the Geotube® containers.

Once inside, solids remained trapped, while clean filtrate trickled out through the tiny pores of the Geotube® container. The reduction in TSS averaged about 91%, with significant reductions in nitrogen and phosphorus also achieved.  A report of the pilot project, issued by the HMGA, stated that Geotube® dewatering is a viable option to treat vegetable was and flume water.

A Geotube® solution provides a much more reliable method to capture the organic muck and achieve major reductions in solids and nutrients that are entering receiving bodies. Once full, a Geotube® container can be cut open and the soil inside can be reclaimed for continued agricultural use.

Learn more about using Bishop Water’s solids management solution at a WTP.

Contact us to discuss dewatering options for your WTP.

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