EISU Seminar Mission South Korea

Environmental Industries Sector Unit

EISU Seminar Mission South Korea

Leachate treatment from a UK perspective

Dr Robert EdenDr Robert EdenManaging DirectorManaging DirectorOrganics Group plcOrganics Group plc


• UK company delivering equipment for waste management systems around the world

• Originally working with landfill gas and leachate technologies

• Now also involved in waste to energy systems

• Global experience with particular emphasis in Europe, the Far East and China

Organics Group plc



What is leachate ?What is leachate ?

A toxic liquid that forms in landfills as water passes through deposited wastes and mixes with chemicals in the wastes



How is leachate a threat ?

Leachate can leak from landfills causing toxic contamination of ground and surface water, hazards to human health and damage aquatic ecosystems



Saturated sites



DRY/CONTAINED SITE

Dry sites



Soil cover

Low permeability barrierR* R

ETJ P ET

Sb

LLr

L1Ig

Ig

Is

Us

Hydrological balance of a landfill site

P Precipitation R* External runoff Us Soilwater Is

Ig

Water from natural aquifers

J Irrigation ET Evapo-transpiration S Sludge

water Li Leachate in drains

R Surface runoff b water production Li Infiltration toaquifers Lr Total leachate

production



The UK approach to leachate management has for many years been based on:

• Applied and experimental research data• Site-specific risk assessment• Best Practical Environmental Option• BATNEEC • Principles of Sustainability



• Used extensively in sewage sludge treatment. • Particularly effective for acetogenic leachates, although may become inoperative once methanogenesis commences. • Ammonia removal not achieved.

Anaerobic biological treatment



• Used to remove non-degradable organic compounds, although often used after some prior form of treatment to 'polish' effluent.

• The technique is, however, expensive and can produce a high-strength concentrate which must in turn be disposed of.

Reverse osmosis



• Effective, economical means of reducing BOD and ammonia

• Aerated lagoons have been used successfully to remove BOD and nitrify ammonia. Can be adversely affected by low values of BOD

Aerobic biological treatment







• This method has the potential to remove COD, ammonia, nitrate and suspended solids, although researchhas yet to establish optimum conditions of operation.

Reed beds





Ammonia is found in raw domestic sewage in concentrations of about 30 mg/litre. In leachate it may rise to several thousands of milligrams per litre



Ammonia is toxic to fish. Lethal concentrations range from 2.5 to 25 mg/l

As ammonia is biologically oxidised to nitrate it exerts an oxygen demand on the receiving water

Ammonia acts as a fertiliser



Ammonia nitrogen is present in water in two forms.

The first is as dissociated ammonia, NH4+,

also referred to as the ammonium ion. The second is as undissociated ammonia,

NH3, known as ammonia gas



NH4+ + OH- NH3 + H2O

f = [NH3] / [NH3] + [NH4+]

The relationship between the ammonium ion and ammonium gas



The effect of temperature and pH on "f"

6 8 10 129 117

1.0

0.5

0.75

0.25

0

pH

'f'

35 deg C

10 deg C



Air stripping of ammonia involves the passage of large quantities of air over the exposed surface of the leachate, thus causing the partial pressure of the ammonia gas within the water to drive the ammonia from the liquid phase to the gas phase



NENT LTP

Flow rate: 1,400 m3/d Influent concentration: 6,700 mg/l NH3-N

Effluent concentration: 100 mg/l NH3-N







Thermal Destructor Emissions

Gas Feed concentration

Exit concentration

% Destruction

Methane 50% <0.002% 99.996

Ammonia 91,573 mg/m3 47 mg/m3 99.994

NO 3.7 mg/m3 9 mg/m3 n/a

NO2 3.8 mg/m3 17 mg/m3 n/a


There are no technical obstacles to the treatment of landfill leachate to extremely high standards



www.organics.comwww.organics.com

Organics Group plc


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EISU Seminar Mission South Korea