What Is Leachate? And How Is It Collected From The Bottom Of A Landfill?

Rainfall enters the landfill cell, and what isn't absorbed into the waste moves down to the basal filter. It passes through the pipe network, and rests in the sump. Pumps remove it from the sump, and may have to lift it 30 to 80 metres upward out of the top of the landfill. Make no mistake about how difficult this is. Even with modern pump technology to help, it is no easy feat to achieve this in the demanding conditions deep inside a landfill.

Leachate collection systems must be planned. The number, location, and size of the sumps are vital to an efficient operation of the landfill.

When designing sumps, the amount of leachate and liquid expected is the foremost concern. Areas in which rainfall is higher than average typically have larger sumps. This is called leachate management.

Leachate Management

A further criterion for leachate management sump planning is accounting for the pump capacity. The relationship of pump capacity and sump size is inversed. If the pump capacity is low, the volume of the sump should be larger than average. It is critical for the volume of the sump to be able to store the expected leachate between pumping cycles.

This relationship helps maintain a healthy operation. Sump pumps can function with preset phase times. If the flow is not predictable, a predetermined leachate height level can automatically switch the system on. Other conditions for sump planning are maintenance and pump drawdown.

Leachate Collection

Collection pipes typically convey the leachate by gravity to one or more sumps, depending upon the size of the area drained. Leachate collected in the sump is removed by pumping to a vehicle, to a holding facility for subsequent vehicle pickup, or to an on-site treatment facility.

Sump dimensions are governed by the amount of leachate to be stored, pump capacity, and minimum pump drawdown. The volume of the sump must be sufficient of hold the maximum amount of leachate anticipated between pump cycles, plus an additional volume equal to the minimum pump drawdown volume.

Sump size should also consider dimensional requirements for conducting maintenance and inspection activities. Sump pumps may operate with preset cycling times or, if leachate flow is less predictable, the pump may be automatically switched on when the leachate reaches a predetermined level.

Leachate Pipes

The leachate pipes should allow all the leachate to be pumped away, where it can be treated and the resultant slurry reintroduced either to the same landfill or sent to another. However, they can easily become clogged either by precipitation caused by chemical reactions due to the composition of the material that's in the landfill, or from a build-up of micro-organisms in the pipes, or due to the fact that unless designed correctly by experts the pipe walls may be crushed under the many thousands of tonnes of rubbish piled on top of them.

Summary

In the narrow environmental context leachate is therefore any liquid material that drains from land or stockpiled material and contains significantly elevated concentrations of undesirable organic and inorganic material derived from the material that it has passed through.


To prevent it building up inside landfills and escaping from the landfill liner, it has to be lifted out through  leachate collection system deep inside every modern landfill, using very robustly made pumps. This is an often costly challenge for pump manufacturers and landfill engineers alike, but the land around landfills and frequently also the drinking water supplies of the local people, depend upon this being done effectively both now, and for very many years into the future.

Find out more at the Leachate Website - www.leachate.co.uk.

Leachate from Waste and What Dribbles From Many Garbage Collection RCVs

Leachate Keeps on Getting a Bad Press!

A leachate soakaway lagoon excavated on the top of a
landfill to avoid leachate escapes from the
landfill perimeter, in the summer after heavy winter rain.

Leachate isn't that hard to handle when the right level of expertise is applied, but it does cost a fair amount of money, and leachate managers need to take care to provide constant vigilant, and mindful attention to leachate flow rates, especially to ensure that the site operator adequately controls rising rates of leachate production due to periods of wet weather.

Leachate spilt during collection from premises during wet weather is a big factor in high rainfall countries and regions such as around Kuala Lumpur in Malaysia, and it really does need collection in tanks beneath the refuse collection vehicles. But, the collection service operator then also often has to treat the leachate once it is brought back to the waste depot, and that may be harder to achieve than collecting it in tank below the bodies of the refuse collection vehicles in the first place.

Also, many landfill operators have been caught out when, after wet weather, landfill leachate flows can rise from previously created leachate just when least expected, and this can be several months after the rainfall that caused it to be produced has had time to percolate down, and out of the waste again, under gravity. in our second article the authority responsible seems to have set up good contingency haulage plans if case of high future wet weather leachate flows.

The extracts form the two articles which follow, have been selected to illustrate the points we make above.

ᔥLeachate leaves a stinking trail - New Straits Times:

FOUL SMELL: Residents in Kepong are complaining about the stench left behind by the garbage compactors servicing their areas

KUALA LUMPUR: THE problem of leachate leaking onto the streets as garbage compactors move around to collect rubbish is a common occurrence in many neighborhoods despite an instruction from a former Alam Flora   chief executive officer a decade ago to install buckets on the trucks to stop spillage.  It is raising the ire of residents.

Two locations checked by Streets had the same problem.

Taman Kepong resident Sue Ng said that every morning when the Alam Flora truck turns up behind Restoran Lima Bintang, it leaves a trail of leachate on the road.

"The stench is unbearable," she said. "At the same time, the restaurant workers have refused to wash down the leachate from their garbage, despite being asked to."

"The contractors should either given a stern warning or have their contracts cancelled," [resident, Jack Tan] said.

ᔥThe county signs contract for stinky liquid overflow - The News Herald

The harder the rain, the bigger the leachate load.

Heavy precipitation means more water runs through the county landfill, slipping and sliding through the refuse, eventually draining out as a clear, stinky liquid called leachate. And Bay County must haul the end product to a treatment facility at Panama City Beach.

Big rains mean the county needs a back-up hauler and now a New Jersey company will help out. The County Commission recently approved a contract with Dana Transport Inc., which has a Panama City office. It was the low-bidder, offering $23.50 per 1,000 gallons hauled. The second-place bidder offered $60 per 1,000 gallons.

“It’s really a contract to supplement our efforts,” said Glenn Ogborn, the county’s solid waste superintendent.

The amount of leachate hauled per year varies by rainfall. In fiscal year 2012, the county moved 5.8 million gallons from the Steelfield Road Landfill, but in 1999, it carried 14.7 million gallons, due to major storms, Ogborn said.

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