Digester cleaning contractors are in charge of removing the build-up of solids that tend to accumulate in the digester. Sooner or later a clean-out is essential to the proper functioning of the anaerobic digestion plant. If you work in the biogas industry, you know that one of the most important—and difficult—jobs is digester cleaning.
The following blog post will explore the role of digester cleaning contractors in the biogas industry. We will discuss the challenges they face and the importance of their work.
Digester Cleaning – Why Do it?
The most common reason for anaerobic digestion plant digester cleaning by Digester Cleaning Contractors is to restore digesters to optimum biogas output, by removing the inert materials which build up inside.
However, it may also be necessary to empty digester tanks simply to inspect them for wear or corrosion, and cleaning may also be needed in order to gain access to repair leaks.
When digester tanks are drained there will normally always be at least some grit, stones, and general trash left in the bottom. This will need to be removed, and doing this is usually considered to be a specialist job.
The reason why the digester operator is well-advised not to do this using in-house staff is normally due to the health and safety hazards involved.
It is incumbent upon all biogas plant operators globally to ensure that the digester cleaning contractors awarded this work are properly experienced and apply all local regulations both in connection with their work on-site, but also act responsibly to dispose of the materials which are removed from the digester tanks during cleaning.
Some older biogas tank installations have to be emptied before worn-out mixers and other internally fitted equipment can be replaced.
In the UK and Europe, the ATEX Regulations apply to digester tanks, due to the potential for there to be explosive biogas in digester tanks after emptying. Each EU country has its own daughter regulations which apply the ATEX Directives in member states. In England and Wales, the ATEX Directive is applied within the DSEA Regulations.
In the US the National Institute for Occupational Safety and Health (NIOSH), is the point of reference for ensuring safety during these works.
List of Digester Cleaning Service Contractors
1. Carylon Corp (US)
Carylon serves customers across the US and competes for any type of tank cleaning project. They describe themselves as a professional team that removes grit, sand, rags, and other debris in a liquid operation or through mobile dewatering.
Poor digester performance and low solids retention time (SRT) can make it difficult for biogas plant operators to meet stabilisation requirements and can result in high-odour biosolids. To maximise the efficiency of all digestion systems, the Carylon process is designed to be customised to individual client needs.
Carylon Corp offers a service in which trained and experienced personnel are deployed. They bring 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.
They say that they use pressurized water to remove, transport and dispose of residual solids. The remaining material is slurried into a semi-liquid form and easily removed and discharged using pumps that operate at up to 4,500 GPM. via Carylon Corp
2. Burch Hydro (US)
Burch Hydro state that their staff has had extensive experience in the cleaning of many different digesters. They are familiar with the requirements needed to successfully and safely clean any type of digester. via Burch Hydro
3. Synagro (US)
Synagro (Baltimore, US) offers a cleaning and servicing service for aerobic and anaerobic digesters, aeration basins, storage tanks and other municipal and industrial water and wastewater facility tanks. They state that they serve customers nationwide and can complete any type of tank cleaning project.
A team of professionals removes grit, sand, rags and other debris in a liquid operation or through mobile dewatering. They work on your schedule, whether you plan to implement a routine cleaning and maintenance program or simply want a skilled and trusted service provider on a periodic basis.
http://www.synagro.com/offerings/digester-cleaning/
4. Wastewater Solids Management Company
The Wastewater Solids Management Company describes itself as possessing over 30 years of accumulative experience in the real world of digester cleaning. They offer cleaning services for aerobic and anaerobic digesters, as well as all tank structures.
In addition to solids removal, Wastewater Solids Management Company offers interior surface hydro-washing and pressure washing.
If you haven't had your digesters cleaned in four to five years, you could be losing up to 50% of your digester capacity to grit and thick, inert sludge solids. After four years, annual capacity loss accelerates.
5. Fergus Power Pump, Inc
Fergus Power Pump, Inc. has 30 years of accumulative experience in cleaning digesters and tanks. We provide cleaning services for digesters as well as all other tank structures.
This accumulation reduces the effective treatment capacity of the digester and negatively affects proper operation. Fergus Power Pump, Inc. can safely and efficiently remove and manage these solids. via Fergus Power Pump Inc.
6. Conhur (Australia and New Zealand)
Conhur offers specialised pumping and recirculation equipment for digester emptying. It has long-term contracts with large municipal clients for digester emptying and cleaning.
They are said to have a proven system for uplifting and removing material from digesters such as rag, fat, mat, and grits. The plant is diesel-powered and designed specifically to handle digester sludge and contaminants.
Conhur is believed to have well-developed, safe practices in place, as well as trained personnel, for emptying and cleaning municipal and enterprise wastewater treatment plant digesters in potentially hazardous environments. via www.conhur.com
7. Celvac (UK)
Celvac states that they carry out Digester Cleaning operations for many of the leading UK Water Companies Welsh Water, Severn Trent, Thames Water, Wessex Water and United Utilities and Tier 1 main contractors such as Black & Veatch and Costain in various locations across the UK.
Their stated aim is to clean digesters in the safest, most environmentally friendly and cost-effective way whilst ensuring that client downtime is minimised. via www.celvac.co.uk
8. DigesterCleaning.com (US)
This company says that they remove grit and debris that is usually not able to be removed using the sludge pumps that draw the biosolids from the digester. Removal of these materials reduces wear. via www.digestercleaning.com
9. JND Thomas (US)
JND states that they provide experienced digester cleaning that includes biosolids processing and disposal.
They say that to keep digesters performing at their maximum capacity, thorough cleaning and removal of materials is imperative. Our cleaning methods include flushing, screening, pumping, and removing accumulated material that impairs the functioning of your digester. The debris is removed through a dewatering process that allows us to treat the material and dispose of it properly. via JND Thomas
10. Harpers Environmental – Digester Cleaning Contractors (UK)
Harpers offer various methods to suit the anaerobic digestion plant operator's particular needs and scope of work.
Using pressurized water they can remove, transport and dispose of residual solids. The remaining material is slurred into a semi-liquid form and easily removed and discharged using pumps that operate at up to 4,500 GPM. via Harpers-Environmental
11. IWJS Digester Cleaning Contractors (UK)
IWJS state that they have been working for the wastewater utility sector since also the very beginning in 1977 so their experience of cleaning assets in sewage treatment works should be wide.
Special operations teams are chosen to deliver high-hazard projects as large digester tank cleans. via www.iwjs.co.uk
12. Veris Environmental (US)
Many treatment plants require periodic cleaning of digesters and other sludge-holding tanks, but most do not have the capacity to perform this work in-house.
Veris Environmental provides this service to its clients. Personnel with permit-required confined space entry certifications are on their team. This certification enables their employees to enter a digester safely and finish the cleaning by washing the interior to remove accumulated solids, grit, and debris.
They also have hydraulically powered pumps that mix the digester contents in place. The digester cleaning residuals can be transported as a liquid or piped to one of their mobile dewatering systems. The dewatered cake can be applied to the land or landfilled as needed.
Veris has expanded from the original owner operating the equipment to over sixty employees with contracts in Arizona, Colorado, Idaho, Kansas, Montana, Nebraska, Nevada, New Mexico, Oregon, Texas, Utah, and Washington. via verisenvironmental.com
13. Green South Solutions (US)
Green South Solutions describes itself as being familiar with the requirements needed to successfully and safely clean any type of digester.
While needs alter, Green South Solution's promise remains constant. They will increase the efficiency of any digestive system while saving AD plant operators time and money. via www.greensouthsolutions.com
How Often Should Digesters Be Cleaned?
UTAH, Gov Suggests the following guidance on how frequently Digester Cleaning Contractors should be engaged:
“A reasonable cleaning frequency is once every three to eight years, depending on grit accumulation within the digester, with the digesters losing 20 to 25 percent of volume during this time period. It is recommended that the digesters be cleaned after their fourth year of operation; however, some facilities have been able to extend their operation a few more years before cleaning was required. Monitoring grit accumulation within the digesters once per year after an initial three years of operation will help determine when cleaning is required at the facility.”
“Failure analyses of the digester mechanical, electrical, and instrumentation systems, as well as implementation of upgrades and/or replacement, should be considered prior to the execution of a digester cleaning project. Cleaning projects should also include the chemical and/or mechanical cleaning of the various piping systems.” via Utah.gov
Digester Cleaning Contractors – Article Conclusion
When it comes to biogas digester cleaning, nothing is as important as the digester. The digester is responsible for breaking down solid waste so that it can be properly disposed of and without it the AD plant won't create biogas at all. This type of waste includes sewage, animal waste, and food waste.
There are a number of companies that specialize in digester cleaning. These companies use a variety of methods to clean the digester, including pressure washing, steam cleaning, and chemical cleaning.
In this blog post, we explored the different types of digester cleaning contractors, their company names and the services they offer. We also provided a brief overview of the cleaning process and the benefits of having a clean digester.
We hope you found this article useful.
Please provide your comments on Anaerobic Digestion Plant Digester Cleaning (Biogas Plant Tank cleaning) Contractors in the comment box below:
[Published August 2017. Updated August 2022.]
It would have been more helpful if you had included more on:
1. The frequency of cleaning, rather than just including the Utah Governor’s comments, which could be taken to trying to extend the period as much as possible? For example, how do the economics stack up of overall biogas production .v. cleaning cost & repairs? Does anyone have a curve of this over time i.e. how performance declines with years (if not cleaned)?
2. Typical costs of cleaning each time, and whether these differ in relation to smallsize and larger size?
3. Whether all contractors dispose of the cleaned-out contents, or rely on the plant owner/operator to do so?
Please consider a further article?
Regards,
Brian
I concede to you having a lot of fantastic info. Saved this to my bookmarks (:. Can anyone tell me how they monitor for the trash and grit level at any time in their tanks? How is it done?
Hello. Neat post. One thing missing. Who has a portable de-silting water clean-up rig for hire? Northwest UK availability? Not everyone can afford a digester cleaning contractor.
The article doesn’t include any information about the block in pumping lines that I assume causes the solids accumulation in the first place. How were the pipes cleaned during the cleanup process? What is the solution to stop these build-ups?
Tremendous things here.
Cleaning the digester is a cost to allow for for few do that.
How can we best avoid grit and silt?
Will you kindly drop me a e-mail?
Hey guys, we’re in the cleaning game too, but what you do is soo much muckier than our windows!
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