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Jan 24, 2017

Driving Performance, Efficiencies and Lowering Costs In Wastewater Management


What was once a problematic by-product, forward thinking water companies are now exploiting sludge as an important fuel in their businesses.

 

Improving the efficiency of wastewater management and sewage sludge processing using robust bulk material handling solutions and advanced digestion systems are now commonplace in reducing fuel costs and carbon emissions.

Category: Product News
Posted by: GSPR

Saxlund-truck-reception-at-Budds-Farm-sewage-worksImproving the efficiency of wastewater management and sewage sludge processing using robust bulk material handling solutions and advanced digestion systems are now commonplace in reducing fuel costs and carbon emissions.

 

What was once a problematic by-product, forward thinking water companies are now exploiting sludge as an important fuel in their businesses.

 

Indeed, many businesses have invested in well-developed sludge strategies and built advanced anaerobic digestion (AAD) plant and thermal hydrolysis infrastructures near cities and urban areas.

 

Reducing Costs in Wastewater Management

 

Companies investing in satellite stations to buffer wastewater residue before transportation to larger hubs are reducing loading times by up to 50%.

 

Selecting the right technical, environmental and economical solution for water companies’ current requirements and their anticipated future needs, makes sound sense.  Extensive experience and a full understanding of the processes and risks are essential.

 

Dewatering sludge into cake makes the residue easier to transport and helps with storage, it also contributes to making it more friable, stable, and safer to manage, while minimising odour.

 

Truck loading silos (TLS) can fill larger rigid trucks or articulated tipper trailers, reducing the waiting time for a truck delivery, and the number of return trips required. They also ensure greater security from foreign object debris (FOD) contamination which can damage pumps and cause restrictions in the downstream plant.

 

Where the sludge has traditionally been produced in settlement tanks at 6% dry solids (DS) and pumped into the tanker for shipment off site, operators are weighing up the cost/benefits of investing in centrifuges and downstream cake handling equipment.

 

This process has resulted in volumetric and mass efficiencies, ie transportation, storage and handling of Slurry @ 6% DS compared with Cake @ 22% DS.

 

Typically, the saving to wastewater management is around £10,000 to £17,000 per month for a 100m3 truck loading silo (TLS) compared with an existing 2-3 RO-RO container system.  For a 240m3 truck loading silo, the saving could be in the region of £27,000 per month.

 

Driving Efficiencies in Wastewater Management

 

Saxlund-truck-reception-Southern-Water-Sewage-worksTLS using the latest sliding-frame technology and screw conveyors enable greater volumes of sludge handling in a shorter space of time than traditional hook lift container storage.

 

Ideally, sludge should be discharged on a ‘first in first out’ basis, when handling materials with a shelf-life.  A sliding frame mechanism can be used to undercut the full section of the contents of the silo to prime a screw trough. Since the whole section is undercut, the pile section discharge is termed “mass-flow” (like the laminar flow in a pipe) from the silo.

 

It is worth mentioning that, while some storage silos may be cheaper, they may be of an inferior design and quality which can result in problems with bridging and discharge.  Wastewater management storage systems need to be large enough to accommodate up to four days’ fill, taking account of reduced workforce over four-day-long bank holiday weekends:  cheaper silos have been known to collapse when they cannot properly contain the weight of the sludge.

 

Technological innovations such as these in use by Southern Water and Anglian Water are completely changing the way the waste water industry deals with converting sewage sludge to energy.  To maintain the economy of scale, efficiencies in advanced anaerobic digestion at each hub, indigenous waste needs to be topped up, which means transferring sludge from satellite sites to central hubs.

 

Driving Performance in Wastewater Management

 

Friable sludge, free from foreign objects, handled without excessive force and with an accurate DS%, is what anaerobic digester operators require for optimum performance.

 

A constant precisely metered volumetric flow of friable sludge is critical to anaerobic digestion and thermal hydrolysis systems and requires properly engineered solutions that take account of the materials’ non-free flowing properties to avoid the risk of blockages. A steady flow ensures a homogenous discharge to the next process.  The thermal hydrolysis process involves heating sludge to destroy any pathogens and degrading cell structures to create better flowing, good quality sludge making it easier for bacteria to digest and to produce methane.

 

For more information about the benefits of driving performance and efficiencies in wastewater management, you can download our white paper "The Financial Argument for Improved Sludge Handling In The Waste Water Industry" below.

 

The Financial Argument for Improved Sludge Handling In The Waste Water Industry