Project objectives:
The main objective is to show the technical, economical and environmental viability of these processes application in leachate treatment:
> To show the effectiveness and the environmental interest of the leachate treatment by the SHARON-ANAMMOX processes and to define the operation parameter
to that treatment in this particular instance.
> To show the effectiveness and the environmental interest of the leachate treatment process by Thermal dry technique.
> To show the economic and technique viability of both processes combined (SHARON-ANAMMOX and Thermal dry) in leachate treatment and its interest to landfills
management, as well as to show, its environmental interest.
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Project
Summary:
Wastewater generated in an urban landfill (i.e, 'leachate'), presents high contaminant levels, mainly due to its high organic matter, nitrogen and salt contents.
One of the most important problems is the complex nitrogen removal, almost composed of ammonium and organic nitrogen, caused by:
> A high and increasing over time nitrogen concentration
> A low carbon-nitrogen (C:N) ratio. The available organic matter for denitrification purposes using a classical activated sludge process is not enough
to ensure high denitrification efficiencies.
> The use of physical-chemical treatments (i.e. ammonia stripping plus ammonium sulphate recovery) present high technical and manipulation complications
because of control, stability and hazard aspects.
Thus, application of innovative techniques to reduce the economical and environmental impact when treating landfill leachates must be considered. The
leachate treatment must be applied in order to solve different shapes of the problem: i) the high nitrogen contents, ii) an increasing over time of the non-biodegradable
organic matter faction, iii) the high contents of inorganic salts (i.e. chloride). In spite of is not possible to solve the global problem applying a unique
technology, combination of different physical, biological and chemical technologies could be a suitable option to reduce the contamination levels of leachates.
Nitrogen removal from leachates could be conducted by the application of biological processes, especially with those based in an Anaerobic Ammonium Oxidation
(ANAMMOX) where no organic matter is used to transform the ammonium to nitrogen gas. The anammox process is based on the activity of autotrophic bacteria, which
transforms ammonium plus nitrite to nitrogen gas under anaerobic conditions. Thus, dissolved oxygen is not needed and only inorganic carbon (carbon dioxide
or bicarbonate) is used for new cell synthesis. Nevertheless, application of the anammox technology requires the use of a suitable composition of the wastewater
to be treated, mainly because of the use of ammonium plus nitrite. Therefore, because of nitrogen present in leachate is mainly ammonia, a partial conversion
of ammonia to nitrite must be conducted prior to the anammox process. Such partial ammonia conversion to nitrite can be easily conducted by means of an aerated
biological nitrification using a continuous stirred tank reactor without biomass retention and working at temperatures around 40ºC, the Sharon Process.
The demonstration of the application of these processes to the leachate treatment could represent one of the most effective solutions in the leachate treatment
due to:
> The nitrogen cycle will be close with this treatment. At the moment treatment used don't close the cycle, so they have negative effects on the environment.
SHARON-ANAMMOX processes will be positive in environmental preservation.
> It is a biological treatment.
On the other hand, to close the waste cycle, a thermal dry technology will be applied after the Sharon-Anammox process. This technology, used nowadays in
other sectors like the food industry, will be applied for the first time to an urban waste leachate treatment. Another newness in the process will be the use of
energy recovery techniques associated with the methane combustion from the landfill: the biogas combustion generated in landfill will produce enough thermal
energy to allow the drying of the free nitrogen liquid emission obtained after the Sharon -Anammox process application. At the same time, this combustion will
generate electric energy, which will be used in the landfill installations. As a consequence of the thermal dry process, some solid and gaseous emissions are
obtained. Gaseous emissions must be not contaminants and solid emissions must have security analysis of contaminants and inflammable power, in order to make
the final disposal in landfill.
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Professor Paul Bardos