Modelling of the leachate treatment plant with membrane bioreactor process

Abstract

The widely used method of waste disposal is landfilling both worldwide and in Turkey. This method is conventionally adhered to regardless of the fact that it is the last, therefore the last desirable, step in the waste management pyramid. There are numerous negative effects of landfills, including, deforestation, greenhouse gas emissions, and groundwater pollution. Control systems are utilized for detection and minimization of environmental pollutants, such as the gas collection and leachate collection systems being installed during the construction phase. Methane (CH4), carbon dioxide (CO2) and various other low rate gases, along with highly polluted leachate are handled at well-designed landfill sites. Environmetal conditions and leachate properties may change over the course of the landfill life. Precipitation directly affects the leachate characteristics. High groundwater levels and leackage of the landfill leachate (LL) may result in groundwater pollution. Landfill properties may alter leachate characteristics; such as waste composition, pH and redox potential of the landfill. The literature shows, it is showen that increasing plastic usage affects the leachate composition. About 17 different plastic types are included in leachate with varying concentrations of 0.5-25 item in a liter of leachate. Another substantial factor affecting the leachate characteristics is landfill age. It directly alters the characterization of leachate pollution parameters; namely Chemical Oxygen Demand (COD), Biochemical Oxygen Demand (BOD), total nitrogen (TN), ammonium nitrogen (NH4-N), total phosphorous (TP), alkalinity, and pH. BOD or alkalinity levels are indicator of treatability. High BOD levels shows that the leachate can be well treated . In the new landfilled wastes, low-chain and weak organic molecules exist which are categorized as easily biodegradable. In the old aged leachates, heavy molecular weight matters are dominant. If BOD level of a leachate is low, this leachate is generally categorized as old with low treatability of old leachates is low. Additionally, phosphorous (P), alkalinity and organic matter addition is necessary for biological treatment of leachate. In terms of the COD parameter, medium-strength leachate is 16 times polluted than medium-strength domestic wastewater. The BOD/COD ratio is different for several leachate types because treatabilities vary. Landfill leachate is classified in 3 categories according to landfill age. Landfills with age of 5 years or less generate young leachate. When the landfill age is in between 5-10 years, leachate is categorized as medium. Old leachate results from 10 years and older landfills. The BOD/COD ratio is greater than 0.5 for young leachate, equal to 0.5 for medium leachate and less than 0.3 for old leachate. In summary, young leachate has the highest level of treatability while medium leachate is almost as high. Organic matter addition is possible sometimes in medium leachates. Old leachate has the lowest treatability. All the parameters change with landfill age as provided in the literature review section of thesis. This thesis investigates how different LL types affect the current treatment capacity of the leachate treatment plant.