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Source: STANDARD HANDBOOK OF ENVIRONMENTAL ENGINEERING
SOLID WASTEEugene A. Glysson, Ph.D., P .E.*
Solid waste management continues to progress from conventional collection techniques and disposal methods to an integrated approach focused on source reduction and recycling. As land becomes more limited and regulations increase, the environmental engineer also directs attention to development and application of advanced disposal technologies. Solid wastes are those materials, other than liquids or gases, that are deemed by their owner to no longer possess value and are discarded. They are generated by almost every activity, and the amount varies by source, season, geography, and time. Historically, solid waste disposal consisted of open dumping but now is carried out in double-lined landfills with collection of and controls for gases and/or leachate. Other disposal means include composting and various incineration processes, which also may be used for codisposal of wastewater treatment sludges. These disposal means typically require controls for created pollutants, such as leachate and odor from compost operations and chemical and particulate emission from incinerator combustion. Recovery and reuse are practiced widely. Source or central facility separation is used for a variety of products including paper, glass, plastics, ferrous metals, and nonferrous metals. Also, refuse-derived fuels may be used for energy production, and yard wastes may be composted to produce a humus soil conditioner.
SOLID WASTE 8.2CHAPTER EIGHT
Residential Waste Generation. Wastes generated by residential households are usually calculated in pounds (kilograms) per capita per day. This measurement is suitable for gross estimates for use in sizing disposal facilities and resource recovery operations, but is not appropriate for the design of collection systems (1). Collection systems are more appropriately designed utilizing the annual average weight (pounds) per household (or stop) per week (PPHW). Households are an easily observed unit along a collection route. The U.S. Environmental Protection Agency (2) reports a range of from 46.2 to 71.0 lb per household per week from nine cities with curbside pickup in the 1970s. The average was 57.3 lb per household per week, which might be considered a typical value. In 1981 two studies (1) showed generation rates to be between 48.7 to 52.0 lb per household per week. One state department of natural resources recommends 52.0 lb per household per week for residential refuse collection (3). One pound per household per week (PPHW) equals 0.454 kg per household per week. Estimates for household waste generation should be based on actual measurement. This means actually counting the residences on residential routes and weighing the refuse collected. Care must be taken to include the entire spectrum of residential premises and the various seasons of the year. Attempts have been made to correlate residential solid waste generation to several measurable factors including population served, households served, value of property, size of living area, and household income. Statistical analysis has led to the conclusion that population served is the most significant variable. Measurement of residential refuse picked up at the curbside indicates that weekly refuse generation can be expressed by the following equation: G = a + bP where G = generation of household refuse in mass per week per household a, b = constants determined by waste measurement survey P = average persons per household in sample area (see Figure 8.1.) Typical values of a and b as derived by field measurement are as follows: Field Study I Field Study II a = 45.0, b = 3.3 a = 44.4, b = 2.8
Residential waste generation is not uniform throughout the year. An EPA report (2) shows average weekly rates per household for each month in 11 cities scattered throughout the United States. These data have been reduced to a monthly multiplier (Table 8.1) for use with the annual average weekly generation rate. Table 8.1 gives monthly multiplier and the maximum and minimum multipliers based on the data from these 11 cities. These data are also shown graphically in Figure 8.2. Nonresidential Waste Generation. Refuse generation from various other sources has been evaluated by various agencies. These waste-generation rates are shown in Table 8.2. Effect Solid waste has a prevailing characteristic that sets it aside from the liquid and gaseous wastes produced by society. The characteristic is that it remains highly visible in the environment in which we live. Liquid wastes are quickly relegated to a sewer and are out of sight, and gases disperse into the atmosphere. Solid wastes, however, are stored and transported in and through societies living space and have great potential for adversely affecting the quality of the environment. The environmental effect of solid waste management begins with on-site storage. This aspect of management has a profound impact on the local environment, since improperly stored refuse may attract insects and
SOLID WASTESOLID WASTE
FIGURE 8.1 Household refuse collection (1).
rodents, present a fire hazard, be an unattractive nuisance, and produce odors, litter, and other unsightly conditions. On-site storage involves proper containerization in order to minimize these possible adverse effects. Various containers are available: galvanized steel and cans, plastic cans, plastic and paper bags for residential use, and steel bulk containers for commercial and other wastes. For residential use, single-use plastic and paper bags have, in general, been shown to be most suitable from all aspects, while plastic cans with good covers are next. Metal cans have the least capability to cope with all the conditions of proper on-site residential refuse storage. The frequency of refuse collection should include consideration for reducing or eliminating as many of the adverse effects of on-site storage as possible.
TABLE 8.1 Multiplier for Annual Average Solid Waste Generation (2) Month January February March April May June July August September October November December Average 0.876 0.871 0.972 1.050 1.125 1.107 1.085 1.024 1.010 0.994 0.985 0.901 Maximum 0.983 1.028 1.123 1.162 1.256 1.268 1.163 1.195 1.083 1.105 1.049 1.098 Minimum 0.786 0.726 0.872 0.956 0.986 0.979 0.991 0.931 0.922 0.890 0.886 0.769
SOLID WASTESOLID WASTE
TABLE 8.2 Unit Waste Factors for Various Generators Category or generator Commercial (SIC 5099) Industrial (SIC 1949) Transportation equipment (SIC 37) Nonelectrical machinery (SIC 35) Electrical machinery (SIC 36) Hospitals Patient care Food service Rehabilitation care Prisons Universities with student housing Colleges without student housing Office buildings Multiple housing units Wood industry Demolition/construction debris Street sweepings Agricultural Campgrounds Family picnicground Group picnicground Organization camp Resort area Rented cabin (with kitchen) Lodge room (no kitchen) Restaurant Residence Ski area Overnight lodge (all facilities) Day lodge (all facilities) Observation site Visitor center Swimming beach Concession stand Administrative residenceNote:1 lb = 0.454 kg.
Unit waste factor 5.75 lb/employee/day (4) 10.6 lb/employee/day (4) 20.5 lb/employee/day (5) 25.5 lb/employee/day (5) 23.5 lb/employee/day (5) 2 to 4.5 lb/staff/day (6) 8.6 lb/bed/day (6) 2.7 lb/bed/day (6) 6.4 lb/bed/day (6) 4.5 lb/inmate/day (7) 1.0 lb/student/day (7) 0.6 lb/student/day (7) 1.5 lb/employee/day (7) 2.7 lb/resident/day (7) 151.0 lb/employee/day (4) 1.2 lb/capita/day (4) 0.3 lb/capita/day (4) 13.0 lb/capita/day (4) 1.3 lb/camper/day (5) 1.0 lb/picnicker (5) 1.16 lb/picnicker (5) 1.81 lb/occupant/day (5) 1.46 lb/occupant/day (5) 0.59 lb/occupant/day (5) 0.71 lb/meal served (5) 2.31 lb