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Landfill Leachate

 

 

What is leachate?

 

Leachate is formed when water passes through the waste in the landfill cell.  The precipitation can be from rain, melted snow or the waste itself. As the liquid moves through the landfill many organic and inorganic compounds, like heavy metals, are transported in the leachate.1  This moves to the base of the landfill cell and collects.

 

The amount of leachate produced is directly linked to the amount of precipitation around the landfill.2  The amount of liquid waste in the landfill also affects the quantity of leachate produced.  A large landfill site will produce greater amount of leachate than a smaller site.     

 

How the landfill has been constructed determines whether the leachate pollutes groundwater. In landfill sites which have been created recently, liners are present and so this greatly limits the leachate leaking and the only way it will leave the cell is if the liner tears.2

 

What are the factors affecting the composition of landfill leachate?

 

 

What are the methods of leachate disposal?

 

Recycling of leachate

 

Leachate is collected at the base of the landfill and instead of being sent away for treatment it is flushed back through the landfill waste many times.  This increases the rate at which the waste material decomposes. 

 

Table 1.  Pros and cons of leachate recycling3

 

Pros

Cons

Enhances landfill stabilisation because rate of landfill gas production is increased due to increase waste moisture content.

Increase rate of groundwater pollution if used in a landfill with single-composite-lining.

Provides a means of leachate disposal.

 

Reduce volume of municipal solid waste leachates.

 Increases toxicity of leachate by concentrating it.

 

However, groundwater pollution is minimal with a double-composite-lined landfill and so recycling is now in practice in some landfill sites.4  Dunbar landfill site recycle their leachates as they have a double-composite-lined landfill.  They carefully monitor the groundwater and a stream which is checked before it reaches the landfill, as it passes and also after the landfill.  There has been no evidence of pollution caused by the leachate recycling.

 

Collection of leachate5

 

Leachate is collected from the bottom of modern landfills by a series of collection pipes installed into the base of the landfill.  The leachate percolates through the waste and into the pipes where it collects.  The leachate can then be recycled or pumped out of the landfill and placed in storage areas or directly into the leachate treatment plant.

 

Extraction of leachate

 

 

Treatment of leachate5

 

Before treating leachate it is necessary to know the following information;

 

  1. The anticipated flow rate that will require treatment.  This mainly depends on the water inflow into the landfill.

  2. Composition of leachate at source which is carried out in an equipped laboratory

  3. Discharge composition required by the authorities

 

What factors determine the chance of contamination by any leachate that is not caught by collection systems?

 

 

What are the potential health effects of leachate?

 

Many studies have investigated the possible health effects caused by landfill sites.  No direct links between diseases, like cancer, and landfill have been found. (See studies into health hazards).  The tables below show the possible health effects of some chemicals that can be found in household waste and which are dumped into the landfill and if not properly controlled could leak out as leachate.

  

Table 2: Health effects caused by acute exposure.7

 

Chemical

Source

Health effects from acute exposure

Toluene/xylene

Glues and paints

Euphoria, excitement, tremor, CNS depression, convulsions, coma

Phenols and cresols

Paint

Burning pain in mouth and throat, nausea, vomiting, diarrhoea, pallor, sweating, shock, coma,

Benzene

Solvent, starting material in chemical manufacture

Single exposure unlikely to cause problem

Nickel

Manufacture of batteries, colouring ceramics and glass

Skin – irritation and dermatitis

Ingestion – stomatitis, gingivitis and possible diarrhoea

Cadmium compounds

Paint and batteries

Inhalation- delayed features 12-36 hrs,

hypersalivation, metallic taste, cough, dysponea, chest pain. Pneumonitis and pulmonary oedema develop within 1-4 days

Ingestion – small amounts ingested GI irritation, nausea and diarrhoea within 15-30 mins. Larger amounts affect calcium and zinc metabolism, cause facial and pulmonary oedema.

Skin – irritation

Lead

Lead paint (apply to older landfill sites), pottery, cosmetics and some ethnic remedies

Severe abdominal pain, diarrhoea with black stools, vomiting, hypotension, cramps, headache, confusion, drowsiness, coma and seizures secondary to cerebral oedema.

Mercury

Lamps, thermometers

Bloody diarrhoea, intestinal mucosal necrosis, dehydration, circulatory collapse, proteinuria and renal failure

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Table 3: Health effects from chronic exposure to chemicals.7

 

Chemical

Health effects from chronic exposure

Toluene/xylene

Ventricular arrhythmias, hepatic and renal necrosis

Phenols and cresols

Renal failure

Benzene

Haematological abnormalities

Nickel

 

Cadmium compounds

Fumes – anaemia, kidney damage, possible prostate and lung cancer.

Lead

Anorexia, abdominal pain and constipation. Toxic megacolon, headaches, fatigue, depression, dropped wrist, proximal renal tubular dysfunction, chronic nephropathy and hypertension.

Mercury

CNS - irritability, tremour, memory loss, seizures, coma

 

Respiratory – necrotising bronchitis, pulmonary oedema, ARDS, pulmonary haemorrhage.

 

GI – metallic taste, vomiting, diarrhoea, stomatatis, blue-line along gum margin

 

Renal – proteuria, haematuria and acute renal failure

 

Eyes – grey or brown lens discolouration, band shaped corneal opacities

 

Haematological – thrombocytopenia, anaemia secondary to GI bleed.

 

 

Conclusion

 

Leachates are a potential hazardous waste from landfill sites.  If not dealt with properly they can cause pollution to groundwater, health problems and effect the environment.  It is important that leachates are treated and contained to prevent these occurrences.  

 

References

  1. Monroe, M. Landfill leachate treatment: VSEP offers a revolutionary solution. Feb 2001. www.vsep.com/company/articles/2.html [Accessed 19.12.02]

  2. Leachate. www.foe.org/site1/ptp/chapter3.html [Accessed 05.12.02]

  3. Fred Lee, G. and Jones-Lee, A. Leachate recycle offers pros and cons to groundwater pollution. August 1994. www.gfredlee.com/slov_rcy.htm [Accessed 19.12.02]

  4. Fred Lee, G. and Jones-Lee, A. Appropriate use of municipal solid waste (MSW) leachate recycling in MSW landfilling. www.gfredlee.com/leachatepapsli.pdf [Accessed 19.12.02]

  5.  Leachate treatment method. http://www.cee.vt.edu/program_areas/environmental/teach/gwprimer/group10/leachate.htm

  6. Eden, R D. Landfill gas and leachate – The selection of technologies to meet the objectives of integrated pollution control. www.leachate.com/Main%20Index.htm [Accessed 19.12.02]

  7. TOXbase