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Digester Cleaning – Purposes and Services

Digester Cleaning is fast becoming an established business sector within the Anaerobic digestion industry. In the UK half a dozen companies actively market their service specifically to the AD and biogas sector.

The build-up of grit and debris in biogas plant reactors is all too often being found to negatively impact the operation of digesters, and severely reduce biogas yield, as more AD Plants come on stream, and existing plants age.

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Early AD plant designers often paid too little attention to the build-up of unwanted materials in reactors, but now there are more powerful mixing systems which, to some extent can re-mobilise and re-suspend silty materials and reduce this problem. The Landia GasMix is one such product. Some digester designs now include for digester cleaning in a “hopper-like” funnel shaping to the base of these tanks, to allow withdrawal of silt etc., from the tank bottoms during normal digester operation.

The buildup of grit and debris (hair, sand, rags etc.) can negatively impact the operation of a digester by reducing its retention time and not allowing the full proper digestion process to take place.  This grit and debris is usually not able to be removed using the sludge pumps that draw the biosolids from the digester, and that which is able to be removed is very harsh on typical pumping and heating equipment that is in place, causing higher maintenance costs. via American Process Group – Digester Cleaning

Sampling-during digester cleaning workWhen this occurs, immediate and thorough digester tank cleaning is required.

At this point the wise anaerobic digestion plant operator will seek to appoint a professional digester cleaning contractor to come and as rapidly as possible clean – out the problem digester tank or tanks.

This is a painful process for biogas plant operators, due to the inevitable lost production time and loss of biogas plant revenue.

The best digester cleaning contractors will provide:

… trained and experienced personnel …deployed with all of the necessary flushing, pumping, venting and safety equipment, to quickly and safely remove all organic and inorganic materials that interfere with the operation of the digester.

Using pressurized water they can remove, transport and dispose of residual solids. Remaining material is slurried into a semi-liquid form and easily removed and discharged using pumps that operate at up to 4,500 gpm.

They also have the capabilities and equipment to dewater the removed sludge, grit, trash and other material, allowing for landfill disposal. via Digester Cleaning – Specialized Maintenance Services

And, do it as quickly as possible.

Taking a Pragmatic View of Digester Cleaning

No matter how advanced your digester is, it will eventually need to be cleaned. Otherwise, solids build up and the efficiency levels go down.  It’s no different than replacing a filter in your furnace. Once the filter is clogged up, it stops proper air flow and affects the performance of your furnace.

We recommend regular cleaning of your digester from top to bottom every 4 to 7 years. At the same time, it’s an ideal time to inspect your digester system and tank to ensure everything is in proper working order.

All of this requires a high level of expertise, extensive safety training, and of course, equipment that is designed to get the job done the right way.  Our team is trained in every aspect of the cleaning process from inspection to pumping, vacuuming, dewatering, and more. They use special, high powered vacuum trucks as well as mobile screening units to bring your digester system back to peak performance.

Digester cleaning requires the removal of heavy material (ie: the scum blanket and heavy build up) from the digester. via How do you clean digesters? – Wessuc

The Digester Cleaning Contractor will normally also be tasked with treating the water content of the digester. Therefore, all digester cleaning contractors worthy of the name nowadays, base their cleaning bids on using their own specialised dewatering and water treatment machinery.  The result is that they provide an indispensable service to biogas plant operators by bringing overloaded and even inoperable digester tanks back to full operating capacity.

So, we have said that:

Overloading, lack of adequate mixing, loss of gas recovery, or grit and trash, can cause a wastewater digester to slow-down and function at only a small percentage of its designed capacity, or not at all.

But this is not a reason to close down a biogas plant because highly trained and experienced personnel are available. These are trained specialists who can be deployed with all of the necessary digester cleaning equipment to quickly and safely remove all organic and inorganic materials that interfere with the operation of a digester.

Some also provide composting for the organic sludge, and indeed:

“All wastes generated as a result of our cleaning procedures can be delivered to our own EPA licensed composting facility, or any of the other number of facilities to where we deliver wastes.” via AQS Environmental Solutions : Digester Cleaning

Hydroblasting

Hydro-blasting is used to mobilise settled silt, and to meet any of the Client’s high-pressure application needs.

Emptying

Is the removal of all unwanted material in the base of a biogas digester tank with the waste removal and disposal capabilities to handle any job

Hydro Excavation

Hydro Excavation, is an effective alternative to digging out firmly compacted materials, where heavy machinery is not practical or to use it may even be unsafe

… And Chemical Cleaning

Chemical Cleaning can be the most efficient, cost-effective method for cleaning sensitive contaminated surfaces or areas that are only accessible by flow, via Hydro Excavation | Industrial Chemical Cleaning …

Digester Cleaning is Often a Challenge to Achieve

Removal of residual sludge from digesters and other storage and process tanks can often be unexpectedly challenging. The material itself is often very dense and gritty with significant amounts of large debris.

The work environment is harsh and often requires confined space entry.

Successful completion of these types of projects requires a contractor specialised in handling challenges such as these. via Digester & Sludge Tank Cleaning | Burch Hydro Inc.

Finally, all digester cleaning projects hold plenty of potential hazards for injury or even death. All confined space entry, for example, will require to be done to the highest health and safety standards, to avoid either explosion or asphyxiation.

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