Overall, in Kansas City landfills, after the first stages of waste decomposition which induce acidification of the medium that can reach a pH of around 4, the consumption of VFAs causes a rise in pH which also stimulates methanogenic activity.
Eventually, the pH can reach values above 9, gradually inhibiting methanogenesis, in particular by the significant production of ammonia (NH4+). Among the microorganisms involved in the biodegradation of matter organic, the methanogenic microflora is the most vulnerable. Research shows a summary of the important parameters involved in the process of methanogenesis.
Deep anaerobic conditions, optimal humidity (55 at 80% relative to the total weight, Senior 1992) and pH between 6.8 and 8 are essential for the good progress of methanogenesis. It is also good demonstrated that a thermophilic diet (around 55 ° C) is particularly favorable to methanogenesis. A more acidic pH and concentration high in salts and particularly in sulphates (found in particular in soils near the sea or in certain construction waste) are, on the other hand, conditions favoring sulfato-reducing bacteria.
These microorganisms found in dumpsters and landfills, also strictly anaerobic, use hydrogen, acetic acid, alcohols and AGVs to form CO2 and hydrogen sulfide (H2S). This molecule, easily detectable thanks to its rotten egg smell, being particularly toxic and volatile, the development of these bacteria, in particular from the same substrates than methanogens, in general tend to rapidly inhibit all of microflora.
Hydrogen sulfide is also harmful to the environment, this bioconversion must be limited therefore doubly. As we have seen, aerobic / anaerobic and pH conditions influence the development of the different populations of microorganisms involved in biodegradation processes. However, it is an essential parameter, the content in humidity, the impact of which is of primary importance on all processes biological. Indeed whether for the enzymes, but also for acid-and acetogenic bacteria or methanogens the activity increases according to the moisture content middle.
It is therefore important to have a good understanding of these waste management parameters depending on the objective pursued, whether to prevent or promote the biodegradation of organic material. In particular, We should focus on the impact of these parameters in the case of biological processes that develop within household waste landfills. dumpster rentals near me
The landfill, a bioreactor to manage
In a landfill, the phenomena that develop, following biodegradation of organic matter, will be more complex than the volume of waste will be heterogeneous and imposing (a few tens to a few million cubic meters). Indeed, the landfill brings together waste of various kinds (materials weakly or rapidly biodegradable, plastics, metals, glasses and ceramics) and mixed populations of endogenous microorganisms (which come from waste, the surrounding atmosphere or the basement of the dump).
The heterogeneity, the presence of biodegradable materials and the influence of external parameters, such as rainfall and temperature, are the source of chemical, physical and biological processes influencing each other and generating flows of gases and liquids. Liquids from a landfill are commonly referred to as leachate.
The gases, for their part, are qualified of biogas. Microorganisms being responsible for most of the changes physicochemical properties of leachate and biogas, we will often assimilate discharge to a biochemical reactor, or bioreactor. Incoming flows in the landfill correspond to the entry of water as well as the supply of waste during filling.
Water, the element with the greatest influence on the evolution of waste in Kansas City, comes from three main sources:
• runoff arriving at the landfill (parameter depending on the design and site management),
• precipitation (parameter depending on climatology and management of the site)
• the water constituting the waste (parameter depending on habits and level of the population).