Municipal Wastes u paper wastes: 32% –newspapers, books, magazines, packaging –good recycling potential u yard wastes: 19% –grass clippings, brush, leaves –varies seasonally & geographically u glass wastes: 7% –bottles, glass jars –almost all can be recycled u metal wastes: 8% –beverage & food containers, scrap appliances –good recycling potential u plastic wastes: 10% –recycling programs developed –recycling codes u food wastes: 8% –declined from 15% in ‘85 –affected by garbage disposals
Plastic Recycling Codes u Polyethylene terephthalate, PETE-1 u High-density polyethylene, HDPE-2 u Polyvinyl chloride, PVC-3 u Low-density polyethylene, LDPE-4 u Polypropelyne, PP-5 u Polystyrene, PS-6 u Other, 7
Industrial Classes US Dept. of Commerce, Standard Industrial Classification (SIC)
SW Regulations u 1965: Solid Waste Disposal Act –early recognition of MSW –promoted better management –supported R&D u 1970: Resource Recovery Act –more emphasis on recycling & energy recovery –PHS investigated disposal of hazardous wastes u 1976: Resource Conservation & Recovery Act (RCRA) –control of hazardous waste storage, treatment and disposal –has been amended and reauthorized many times
Functional Elements of a SW Management System Waste Generation Waste handling, separation,storage and processing at the source Collection Disposal Transfer & Transport Separation and processing and transformation of SW Small to large truck Truck & routing Recovery or to improve subsequent handling
Recycling Recycling is the recovery and reuse of a product which would otherwise be thrown away. An accurate analysis of the sources and content of the solid waste stream.An accurate analysis of the sources and content of the solid waste stream. Evaluation of any existing recycling programs. Existing programs must be integrated into the new or expanded program.Evaluation of any existing recycling programs. Existing programs must be integrated into the new or expanded program. Identification of public attitudes about recycling.Identification of public attitudes about recycling. Determine what markets exist for the potential recycled materials. (It does no good to collect materials for recycling if no market exists for their use!)Determine what markets exist for the potential recycled materials. (It does no good to collect materials for recycling if no market exists for their use!) Determine the best recycling options.Determine the best recycling options. Preliminary steps for a recycling program:
Recycling Options u Drop-off Centers –can be staffed or unstaffed u Curbside Collection –more effective, but more expensive u Voluntary vs. Mandatory Recycling –enforcement?
Composting controlled aerobic partial degradation of organic wastes natural microbial processes: fungi, bacteria, protozoa especially useful for leaves that used to be burned waste volume reductions of 40-75% wastes placed in windrows which are periodically mixed
Elements of Composting u Collection –curbside, drop-off, required public education u Preprocessing –grinding, separating, wetting, screening u Composting Parameters –oxygen: supplied by natural aeration –nitrogen: C/N ratio varies with season –temperature: heat release –moisture: at least 50%
Elements of Composting (Cont.) u Multi-Level Composting –Minimal-Level: 12x24 ft. windrows turned annually, center become anaerobic, 3 yrs. –Low-Level: 6x12 ft. windrows mixed monthly to quarterly, watered, 1.5 yrs. –Intermediate-Level: same but turned weekly, specialized equipment, 5 wks. –High-Level: 10x200 ft., forced air, water & N added, 2-10 wks., then left for 3-12 month. u Compost Uses: landscaping, gardening, farming
Collection Vehicles Commonly used for trash collection Also used where recyclables are collected Compression to 50% See problem 11.1
Solid Waste Processing u Sorting –at point of generation, transfer station, or at landfill –mechanical or manual »magnets, compressed air, inertia devices u Compaction –low pressure in collection vehicle –high pressure at transfer station or landfill u Shredding
Landfilling u The legal and controlled placement of wastes in the ground u Dumping u Dumping is illegal or uncontrolled u Material undergoes chemical and biological changes Leachate u Water is present which promotes biodegradation and carries away dissolved substances: Leachate u Leachate collection and recirculation
Siting Restrictions The landfill disposal regulations provide the following restrictions on landfill location: Prohibit the placement of a landfill facility near an airport because of dangers from scavenging birds.Prohibit the placement of a landfill facility near an airport because of dangers from scavenging birds. Require the landfill to be located outside the 100 year floodplain or the landfill design must prevent the washout of solid waste during a 100 year flood.Require the landfill to be located outside the 100 year floodplain or the landfill design must prevent the washout of solid waste during a 100 year flood. Prohibit the placement of a new landfill or expansion of an existing landfill into or on a wetland.Prohibit the placement of a new landfill or expansion of an existing landfill into or on a wetland. Prohibit the placement of a landfill within 200 feet of an earthquake fault.Prohibit the placement of a landfill within 200 feet of an earthquake fault. Prohibit the placement of a landfill in an area with a high probability of a strong earthquake.Prohibit the placement of a landfill in an area with a high probability of a strong earthquake. Prohibit the placement of a landfill in an area with unstable soil.Prohibit the placement of a landfill in an area with unstable soil. Require existing landfills which cannot meet the airport, floodplain, or unstable area requirements above, to close within five years. The state may grant a maximum of a two year extension.Require existing landfills which cannot meet the airport, floodplain, or unstable area requirements above, to close within five years. The state may grant a maximum of a two year extension.
Operational Requirements Exclusion of hazardous waste from the landfill. Provide at least six inches of daily soil cover over new solid waste placed in the landfill. Control disease vectors such as rodents and insects. Monitor methane concentrations in the landfill and buildings. (Methane is explosive when combined with the oxygen in air.) Elimination of most open burning. Control public access. Construct run-on and run-off controls for water. Meet water quality discharge requirements (NPDES) to surface water. Prohibit all liquid wastes except small quantities of household liquid wastes. Maintain records indicating compliance.
Design Requirements u Synthetic membrane liner at least 30 mils thick u Soil liner at least 2 ft. thick u Hydraulic conductivity no more than 10 -7 cm/s u Other state-approved designs possible
Landfilling: Area Method From Sincero & Sincero, 1996