Question

(a) Explain in detail organic and inorganic stabilization of waste disposal sites.

(b) What are the hydrological factors to be considered in design of landfills?

Answer 1

A) the stabilisation of refuse occur due to decomposition of organic matter in due course of time and getting converted into stable products.the entire period of stabilisation can be divided into five phase

1) aerobic bacteria and fungi are dominant,deplete the available oxygen as a result the temperature of landfill increase

2)now anaerobic and facultative bacteria deviled to decompose organic matter and HE and CO2 gases are revolved

3)methanogenic bacteria deviled to cause evolution of methane gas

4) methanogenic activity get stabilised

5) methanogenic activity subsided ,representing depletion of organic matter and ultimately the system returns to aerobic condition within the landfill

B)

Hydrological considerations play a major role in the selection of landfill sites and in the design and performance of landfills for hazardous waste management. A landfill is a form of a biochemical reactor where the municipal solid waste (MSW) comes into contact with moisture, a catalyst, and gets decomposed into solid waste, gases and liquid contaminants (leachate) resulting in the release of heat. The design of the control and recovery systems requires the estimation of amount and composition of gas and leachate accurately, as also the changes in these with time. Lysimeters are used to simulate the landfill performance.

Landfill leachate contaminant concentrations are of primary importance from the point of view of the study. These include organic matter, nitrogen compounds, anions, metals and volatile organic compounds. Chemical and biological reactions modify the compound composition with age of the landfill, and are of concern in environmental hydrology studies. Permeability and hydraulic conductivity measurements for the liners and natural barriers provide basic parameters for the landfill design. Various field and laboratory experiment methods are available for estimating these. These, along with the estimation of various soil parameters like porosity, field capacity, wilting point, saturated hydraulic conductivity and soil retention capacities are a valuable input in studying hydrology.