Low Energy Solar Pumps

Landfill is no longer the first choice for waste disposal but there are still sites in the UK generating leachate. However, energy efficient pumps and digital tools can help minimise its impact, James Lloyd reports.

Solar-powered pumping systems use minimal energy to help prevent leachate contamination (credit: Enital)

The amount of waste going to landfill may have decreased owing to changes in legislation, an increase in recycling and the generation of energy from waste. But there are still many active and closed landfill sites in the UK, requiring responsible management to prevent pollution of the surrounding area.

It was previously believed that it takes about 25 years for landfill sites to stop producing significant amounts of environmental contaminants once they have stopped receiving waste. However, most people in the industry now agree that it can take more than 50 years of managing these sites, which is clearly a long-term responsibility and economic burden for landfill operators.

Landfill leachate, the liquid that moves through decomposing waste or drains from a landfill, is a potential source of pollution if it leaches into the surrounding area. Even low concentrations of leachate from landfill sites can be damaging if it migrates offsite, particularly if it gets into nearby groundwater, surface water and watercourses.

Landfill sites in the UK that have been operational since 1992 are required by regulations from the Environment Agency (EA) or the Scottish Environment Protection Agency (SEPA) to monitor, report and control leachate levels. Provision must be made to control the discharge of leachate and protect the surrounding environment for at least 40 years after the site has stopped taking waste, making leachate a major long term liability.

The EA and SEPA specify criteria for leachate levels within environmental permits issued to landfill sites and operators risk hefty fines if levels exceed compliant levels. Operators use monitoring systems to identify breaches or risks to compliance. If there are any problems, they can adjust, repair or replace the system to prevent pollution to the surrounding area.

Leachate is usually monitored at landfill sites by measuring the depths of the liquid within the waste at numerous points, such as boreholes and wells, to ensure that levels remain compliant. Traditionally, these data are obtained manually by measuring the liquid level from the top of boreholes or wells using a dip meter, and recorded on paper for transferral to a bespoke electronic database. The levels are then quality checked and used to produce reports which demonstrate compliance to the EA and the SEPA, and are needed for a site’s environmental permit. These reports are also used to detect breaches so that the operator can make changes to the leachate control system if necessary.

Pumping at wells

Landfill operators in the UK have adopted the pumping of leachate at wells, most commonly by pneumatic pumps, to control levels and aid compliancy. They are safe, self-regulating and do not need to be powered by cables to the mains. However, they have high power and maintenance costs, as well as being difficult to link with electronic communication systems.

Electric submersible pumps are used where there are greater leachate volumes to deal with or where the pumps need to be connected to electronic communication systems. They have similar running and capital costs to pneumatic pumps but cost less to maintain. However, electric submersible pump systems are generally not as reliable, lack effective integration between the pump system and the monitoring database and require an extensive network of power cables. The type of electric submersible pumps used are of a far higher pumping capacity than the well recharge rates.

Solar-powered low-energy pumping systems offer a solution. They have no power costs and low service and maintenance overheads. These pumps operate using solar irradiance rather than ’sunshine’ and can be used in the most northern parts of the UK. These systems suit even the most remotely located landfill sites which do not have ready access to power from the national grid.

The system pumps leachate to control the level of liquid within the waste at numerous points while recording data that can be easily integrated into electronic communication systems. This type of leachate management system can be operated remotely and highlights any issues when they happen which is suitable for closed landfill sites that are not staffed full time.

The demand to capture data electronically and report it in real time is growing. This used to be a paper-based process and it is only now that electronic field data collection has developed to a point where monitoring using mobile technology is practical and affordable.

Electronic field data software improves efficiency, eliminates the possibility of transcription errors and reduces inaccurate readings inherent in manual data transcription. Self-validation allows technicians to check environmental data against historic trends on site to ensure inaccurate readings are minimised.

Electronic data collection speeds up the job of data management and the production of reports. Depending on the system, the date, time and GPS location of monitoring activities can be automatically recorded which provides traceability. Photographic evidence at the time of monitoring can also be provided if necessary.

Automated monitoring has been available for years but has been either costly or reliant on slow telecoms links. Broadband and wireless networks make the remote upload of large volumes of data realistic and the real-time scheduling of a monitoring event feasible. The ability to stray beyond routine and factor changing risk conditions into the monitoring process will make data more relevant to risk evaluation.

Landfill is no longer the first option for waste disposal. However, the UK has a legacy of landfill sites still generating leachate but at reducing levels. New technology is available to improve the efficiency of, and add value to, site monitoring while helping to minimise the environmental impact of landfill sites.

James Lloyd is the Site Services business manager at Enitial