Activated carbon leachate treatment can be used to remove organic chemicals and reduce toxicity in water to allow safe discharge of treated landfill leachate into groundwaters, and streams.
Used in granular form as GAC or powdered (as PAC), it is highly effective for odor removal and for the sequestration of soluble organic chemicals (COD and, BOD), pesticides, endocrine disruptors and other contaminants of emerging concern.
Reading this article should make it a whole lot simpler to be a success at leachate treatment using activated carbon. To learn the best way to use leachate treatment activated carbon adsorption polishing treatment techniques, continue reading.
The 1st step is to understand that leachate treatment using activated carbon is normally accomplished using the activated carbon (also referred to as the GAC method) as a final tertiary treatment stage in conjunction with at least one previous “primary treatment” stage.
When used in combination with biological pre-treatment Granular activated carbon (GAC) treatment is a leading technology for the final stage of treatment of landfill leachate.
A biological process such as an extended aeration SBR will remove well over 90% of all contaminants in one stage. But in certain regulatory regimes final polishing treatment will still be needed, to attain the degree of purity necessary for a final water quality which is suitable to be discharged.
Landfill Leachate Treatment via the Activated Carbon Adsorption Process
In most developed countries, almost all municipal drinking water is filtered through activated carbon, as part of a multi-step purification process. It is the world's most powerful adsorbent, and it can cope with a wide range of contaminants.
Leachate from landfills contains various organics and contaminants that can have an environmental impact on groundwater and surface water. Some “trace” levels of certain substances found in many landfill leachates must be removed down to very low levels due to their high toxicity.
Trace Compound Removal by GACs
In not removed, some trace compounds although only present in minute concentrations, could have a substantially negative impact on human health.
Granular activated carbon (GAC) in combination with biological pretreatment is a leading technology for the treatment of landfill leachate.
Granular activated carbons remove organic chemicals and reduces toxicity in water to allow safe discharge into groundwater. It is highly effective for odor removal and for the treatment of soluble organic chemicals, pesticides, endocrine disruptors and other contaminants of emerging concern.
Different contaminants may be present in the same discharge and carbon may be used to treat the total flow, or it may be better utilised to remove specific contaminants as part of a multi-stage approach. via ww.chemviron.eu
More on the Contaminants Removed by GAC Treatment
Leachate treatment can achieve:
- a high removal of color (100%),
- pollutants (>90%),
- chemical oxygen demand (∼80%) and
- NH4+-N (100%).
Laboratory studies and field applications have also demonstrated activated carbon's capability to sequester:
- hydrophobic organic compounds such as polychlorinated biphenyls (PCBs),
- polycyclic aromatic hydrocarbons (PAHs),
- dioxin and pesticides …
Activated Carbon Suppliers to the Water Treatment Industry
Activated carbon suppliers are available which supply and recycle/ replenish a wide range of these products for the treatment of water.
Powdered activated carbons (PACs) are used in batch treatment processes, whereas granular (GAC) grades are generally used in fixed filter beds, with the water passing through the filtration medium.
The advantage of using GAC for water treatment is that the spent carbon can normally be regenerated via thermal reactivation. CPL Activated Carbons has separate facilities dedicated to the reactivation of spent carbons from food/potable and industrial/environmental applications. via activated-carbon.com
How PACT Takes Place
Biological treatment and carbon adsorption using powdered activated carbon treatment (PACT) are combined into a single, synergistic treatment step.
This is not surprising as powdered activated carbon treatment is also used in the processing of drinking water at treatment facilities, primarily on a seasonal basis in order to deal with aesthetic problems with the water such as odor and taste issues associated with Geosmin and 2-MIB.
Today there are over 100 PACT systems worldwide.
Some of these installations have been retrofits to existing conventional activated sludge processes (at Wastewater Treatment Works) to meet more stringent effluent requirements.
Several PACT systems have been built in China in recent years as a result of higher treatment regulations for difficult-to-treat industrial wastewaters. via en.wikipedia.org
Activated Carbon (AC) is an adsorbent having high surface area which makes the process of removing heavy metals from wastewater (such as landfill leachate) very effective.
A recent study explored the utilization of three methods of modification of AC produced from coconut shell by treating it with nitric acid (HNO3), potassium permanganate (KMnO4) and heating at 600°C to improve the adsorption capacity.
The AC can remove multi-pollutants by filtration through a packed cylinder of AC when used to treat landfill leachate.
The water quality parameters such as pH, TSS, Ammonia-Nitrogen and some characteristic heavy metals were considered in the study.
Results showed that the removal of these parameters was proportional with the increase of contact time and the bed depth of AC. via ink.springer.com
Activated Carbon Defined
Granular activated carbon is defined as the activated carbon being retained on a 50-mesh sieve.
Carbon can now be produced from a variety of materials. Methods of optimizing the carbon structure for maximum adsorption and degree of activation.
This produces activated carbons designed to meet the demands of a wide array of leachate contaminants.
Intensive research into the use of activated carbons for water and wastewater treatment purposes has been ongoing for decades. This means that its use is no longer considered innovative, and the technology is tried-and-tested/ ready to use.
Use of Activated Carbon in Leachate Treatment
Due to current stringent technical requirements regarding leachate composition, combined processes using activated carbon are being studied with more emphasis. The use of activated carbon as a single-step treatment is rarely found.
However, studies have shown that the single-step treatment of recalcitrant leachates can by GAC packed cylinders can be effective.
When used as a pre-treatment method, the adsorption capacity of activated carbon filter columns is rapidly used up for normal strength sanitary landfill leachate. Treatment becomes very expensive as a result,
However, combined treatment using AC as the final unit treatment process after extended aeration SBR treatment, can be very cost effective and a robust method for old and mature sanitary landfill leachates.
“The use of activated carbon as a final treatment step is also commonly used to reduce to an acceptable level the concentrations of non-biodegradable organic and chlorinated organic compounds, as well as to treat the leachate colour.”
Only Suitable for Very Low Strength Landfill Leachate
Leachate treatment activated carbon supplies are an energy intensive product and this makes them expensive, if used as the primary treatment stage. The activated carbon in each cylinder would very quickly be expended. This would make the AC process simply too costly to use the method as the first stage in leachate treatment for all but the very lowest contaminant levels.
All modern full-strength MSW landfill leachates pumped from landfill cells filled in accordance with modern standards globally, would be considered too strong for treatment solely by activated carbon..
At the same time, avoid rejecting the consideration of leachate treatment activated carbon adsorption methods out-of-hand. They certainly have their legitimate place in leachate treatment when used correctly. By this we mean, only after 95% to 99% of the contaminants have been removed from the leachate before a GAC or PAC stage is used.
To put it crudely, you've got to accomplish the first step completely and properly. If not, the leachate treatment activated carbon becomes fouled up too quickly for its use to be feasible.
The 2nd step is to appreciate what leachate treatment activated carbon adsorption achieves.
The process can be very valuable for those leachate treatment projects which have particularly stringent discharge water quality requirements.
Activated Carbon Treatment Costs
Leachate treatment activated carbon has costs associated with the disposal, or preferably recycling of the spent GAC material which is usually removed by the GAC supplier, heated to volatilize and destroy the contaminants and returned rejuvenated for re-use.
The 3rd step is designing a process which successfully integrates leachate treatment activated carbon into the leachate treatment process. The reason why this will be relevant is as stated earlier GAC treatment is normally implemented after the Primary Treatment Process (eg Biological Aeration Treatment) Stage.
It must be implemented as part of an overall treatment train including other primary processes. Make sure you avoid the error of assuming that you can adopt leachate treatment activated carbon solutions off-the-peg.
Just stick to these 3 easy steps. If you do, you will be able to very usefully include leachate treatment activated carbon techniques into a low cost and reliable leachate treatment plant facility for your landfill site.