Gas collection networks are crucial to effective gas extraction, whether for migration control or gas utilisation. They are therefore a most critical element in effective long-term site management. These systems (including wells, pipework and manifolds) are often buried and unseen, and for this very reason are most vulnerable to shortcuts or neglect; and poor design or installation will seriously affect the efficiency of a system and may render it useless.
At Biogas we believe that there is no substitute to getting the system 'right first time'. Remedial work, whether required immediately or at a later date, is both costly and disruptive.
Minimising the Risk
As an acknowledged leader in landfill gas control and leachate management, Biogas Technology is one of the very few companies able to offer a comprehensive fieldwork capability. We have the in-house technical expertise and practical experience to design and install a gas collection system which you will be assured operates efficiently and reliably.
Central to achieving this standard of performance is careful design and layout of the system to both optimise the extraction of gas from the waste and ensure effective dewatering - to remove condensate which can collect in the pipework and reduce effectiveness and eventually cause blockages.
Design and Installation
The precise specification of fieldwork services required will differ according to each site. Typically we will undertake the following:
Assesment and Preparation
A site inspection is carried out with the client to establish the general extent of works required. in some cases this may include the excavation or drilling of test holes and/or pumping trials where necessary.
Drilling of Boreholes
A drilling technique is selected to suit the site conditions as well as the depth and nature of the material to be drilled. For long life and good performance boreholes must have an adequate diameter and include a non-calcareous gravel surround to the slotted well liner. The top section of the borehole is then sealed around the liner with bentonite.
Wellheads and Well Chambers
The well head assembly fitted to the top of each well draws off the gas from the buried collection pipework. A range of different designs are available to suit site requirements and customer preferences. Each assembly might typically include:
Standard Biogas multi-turn valve to provide accurate control of gas flow. Monitoring points for gas quality and suction pressure, with optional built-in flow measurement facility. Full bore access for cleaning and leachate level monitoring.
Biogas wellheads and chambers are available for conventional vertical wells and also horizontal collection systems, where the site is shallow or the gas is only available close to the surface of the site above the prevailing leachate/water level. Biogas wellheads can also be adapted to enable the simultaneous extraction of gas and leachate.
Biogas offers a range of chambers to suit any local environment, including a small lightweight unit where the risk of settlement is likely.
Each gas wellhead will either be connected directly to its associated collection main or via a local manifold, where appropriate, with the collection main trenched to provide sufficient falls to facilitate reliable condensate dewatering. Where the natural gradient is not adequate to ensure condensate flows to a dewatering point, staggered in-line dewatering points will be used to create artificial falls.
installation of pipework is undertaken according to the strictest UK and European standards. Pipe jointing is completed using butt-fusion or electro-fusion methods, or where appropriate by flange adapter. By using only these methods and keeping the number of pipe joints to a minimum, we are able to maintain reliable performance of the system.
And particular care is taken in reinstatement of trenches, to prevent uncontrolled ingress of air or water to the waste.
The minimum necessary number will be installed at natural low points in the collection system or at artificial low points established where required. Biogas dewatering points automatically return all condensate back to the landfill mass. installed in excavated pits or within boreholes, each dewatering point is designed to provide access for condensate level and gas measurements. Pumped dewatering pots may be used to facilitate dewatering of the gas main where it runs off the landfill.