Warm/Arid Warm/Humid Cold/Humid
Operating time Operating cost
Seasonal Higher More Low
Biosolids storage Salt accumulation in the soil Leaching potential Runoff potential
Higher Most Moderate
Source: Adapted from USEPA, Process Design Manual: Land Application of Municipal Sludge, EPA 625/1-83-016, CERI, Cincinnati, OH, 1983.
The regional climate has a direct effect on the potential biosolids management options, as shown in Table 2.11. Climatic factors are not included in the rating procedure for wastewater systems, because seasonal constraints on operations are already included as a factor in the land area determinations. Seasonal constraints and the local climate are important factors in determining the design hydraulic loading rates and cycles for wastewater systems, as well as the length of the operating season and stormwater runoff conditions for all concepts. The pertinent climatic data required for the design of both wastewater and biosolids systems are listed in Table 2.12. At least a 10-year return period is recommended, although some agencies require a 100-year return period (see NOAA references).
The location of wastewater and biosolids systems within a flood plain can be either an asset or a liability, depending on the approach used for planning and design. Flood-prone areas may be undesirable because of variable drainage characteristics and potential flood damage to the structural components of the system. On the other hand, flood plains and similar terrain may be the only deep soils in the area. If permitted by the regulatory authorities, utilization of such sites for wastewater or biosolids can be an integral part of a flood-plain management plan. Off-site storage of effluent or biosolids can be a design feature to allow the site to flood as needed.
Maps of flood-prone areas have been produced by the U.S. Geological Survey (USGS) in many areas of the United States as part of the Uniform National Program for Managing Flood Losses. The maps are based on the standard 7.5-minute USGS topographic sheets and identify areas with a potential of a 1-in-100
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