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, 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 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 do this using in-house staff is normally due to the health and safety hazards involved.
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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 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 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
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. 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
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
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.
Wastewater Solids Management Company
Wastewater Solids Management Company possesses over 30 years accumulated experience in the field of digester cleaning. They offer to provide cleaning services for both aerobic and anaerobic digesters as well as all other tank structures. In addition to the removal of solids, Wastewater Solids Management Company provides both hydro-washing and pressure washing of interior surfaces.
If you haven't had your digesters cleaned in four to five years, you may have lost up to 50% of your digester capacity to grit and thick, inert sludge solids. Yearly capacity loss accelerates after four years.
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 effects proper operation. Fergus Power Pump, Inc. can safely and efficiently remove and manage these solids. via Fergus Power Pump Inc.
Conhur (Australia and New Zealand)
Case Study for Christies Beach STP: Contract to empty and clean 2 no. 4000m3 Digesters, dewater the resulting sludge and off-site disposal of biosolids using Conhur owned and operated truck and trailer units, under an EPN held by Conhur. via Conhur
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
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
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
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. Remaining material is slurred into a semi-liquid form and easily removed and discharged using pumps that operate at up to 4,500 gpm.
Geotech Developments (UK)
Using our unique technology, developed for the drilling industry, we are now able to offer and effective and efficient way to solve the issues associated with Digester cleaning. Pease contact us for further details. via Geotech Developments
IWJS Digester Cleaning Contractors (UK)
IWJS state that they have been working for the waste water utility sector since also the very beginning in 1977 so their experience of cleaning assets on sewage treatment works should be wide.
Special operations teams are chosen to deliver high-hazard projects like large digester tank cleans. via www.iwjs.co.uk
Flohawks Digester Cleaning Contractors (US)
Dewatering, cleaning, and sludge removal provided for a wide range of applications. via www.flohawks.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
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