SOLID AND HAZARDOUS WASTE.pdf
- 1. SOLID AND HAZARDOUS WASTE
- 2. SOLID WASTE
- 3. Typical composition of MSW from a developed nation
- 22. Hazardous wastes must be deposited in secure industrial landfills, which provide at least 3 metres (10 feet) of separation between the bottom of the landfill and the underlying bedrock or groundwater table. A secure hazardous- waste landfill must have two impermeable liners and leachate collection systems.
- 30. Things to be practiced • Source reduction: decreasing the amount and/or toxicity of waste that must be disposed of by producing less waste to begin with. • Recycling & Reuse: Increasing recycling of materials such as paper, glass, steel, plastic and aluminum, thus recovering these materials rather than discarding them. • Providing safer disposal means by improving the design and management of incinerators and landfills.
- 31. Waste Disposal Facilities 1. Landfilling (open dumps, engineered landfills, bioreactor landfills) 2. Incineration (pyrolysis, gasification) Other means (Organic waste) (a) Anaerobic digestion (biomethanation) (b) Compositing (windrow composting, vermi- composting)
- 32. Landfilling 1. Open dumps 2. Engineered landfills
- 33. What are the main components of an engineered landfill/sanitary landfill? An engineered landfill essentially consists of a barrier layer or liner which is a low permeable zone to prevent the migration of leachate from the landfill to the subsurface soil and water. Above the liner, a drainage layer is placed which collects the leachate from the waste for treatment. Such a layer also minimizes the head causing flow in liner due to the timely removal of leachate from the landfill. The third important layer is the cover to the landfill, which is a multi-layered system to cut off the release of landfill gases into the atmosphere and at the same time to prevent the infiltration of surface runoff into the waste. It also keeps away the scavengers and rag pickers from entering the landfill.
- 34. Incineration CO2, CO, N2O, H2O, SO2, ash
- 36. Pyrolysis • Pyrolysis is the thermochemical decomposition at high temperature (4500C to 8000C) and in the absence of oxygen or in an atmosphere of inert gases. • Nowadays, pyrolysis is getting attention for its flexibility to generate a combination of solid (char), liquid (bio oil) and gaseous (synthetic gas) products in different proportions just by the variation of operating parameters such as temperature or heating rate. • It also provides an opportunity of transforming materials of low energy density into bio-fuels of high-energy density, at the same time recovering high value chemicals. • Diesel engines, gas turbines, steam turbines and boilers can be used directly to generate electricity and heat in using syngas and pyrolysis oil. Syngas may also be used as a basic chemical in petrochemical and refining industries. Char is almost pure carbon and can be used in the manufacture of activated carbon for water treatment applications or as an agricultural soil amendment. • The fractions of MSW subjected to pyrolysis mainly consist of paper, cloth, plastics, food waste and yard waste. The glass, metal and other inert fractions are removed. • Types of reactors include bed reactors, rotary kilns, fluidized bed reactors, plasma or solar reactors. Catalysts are also employed at times to make the process rapid
- 37. Gasification • Gasification of municipal wastes involves the reaction of carbonaceous feedstock with an oxygen-containing reagent, usually oxygen, air, steam or carbon dioxide, generally at temperatures above 800°C. • The process is largely exothermic but some heat may be required to initialise and sustain the gasification process. • Produces syn-gas (synthetic gas/producer gas) consisting of CO2, CO, H2 and CH4 • It is utilized as a gas fuel being combusted in conventional burner or in a gas engine and then connected to a boiler and a steam turbine or gas turbine to utilize the heat or produce electricity. Also, it can be used as a building block for producing valuable products such as chemicals and other forms of fuel energy
- 38. Other methods adopted for organic fractions in MSW Composting • Transformation of organic matter into soil like material (compost) • Uses bacteria and fungi • Entire process in the presence of oxygen • End product is compost, by product is CO2, H2O and little NH3 Anaerobic digestion • Entire process in the absence of oxygen in a closed chamber • Uses anaerobic and facultative bacteria • End product is biogas (methane, CO2) and stabilized nutrient rich organic matter • Require sprinkling water, nutrients to maintain temperature, pH, nutrients, moisture level required for decomposition of organic waste.
- 39. Refuse Derived Fuel • RDF consists largely of combustible components of MSW, such as non recyclable plastics, paper, cardboard and materials recoverable calorific value. • These fractions are separated from the rest of the MSW by different processing steps, such as screening, separation of ferrous and non ferrous materials, glass, stones and other foreign materials. • These fractions are then air dried, shredded into a uniform grain size, and pelletized by applying mechanical pressure in order to produce a homogeneous material which can be used as substitute for fossil fuels in e.g. cement plants, lime plants, coal fired power plants.