3 Analysis and Selection of Wastewater Flowrates and Constituent Loadings Determining wastewater flowrates and constituent mass loadings is a fundamental step in initiating the conceptual process design of wastewater treatment facilities. Reliable data for existing and proiected flowrates affect the hydraulic characteristics, sizing, and operational considerations of the treatment svstem components. Constituent mass loading. the product of constituent concentration and flowrate, is necessary to determine capacity and operational characteristics of the treatment facilities and ancillary uipment to ensure that treatment objectives are met. 3-1 Components of Wastewater Flows The components that make up the wastewater flow from a community depend on the type of collection system used and may include Domestic(also called sanitary) wastewater. Wastewater discharged from residences and from commercial institutional and similar facilities 2. Industrial wastewater. Wastewater in which industrial wastes predominate 3. Infiltration/inflow(I/D. Water that enters the collection system through indirect and direct means Infiltration is extraneous water that enters the collection system through leaking ioints. cracks and breaks. or porous walls. Inflow is stormwater that enters the collection system from storm drain connections (catch basins), foundation and basement drains, or through access port(manhole)covers 4. Stormwater. Runoff resulting from rainfall and snowmelt Three types of collection sy stems are used for the removal of wastewater and stormwater: sanitary collection systems, storm collection systems, and combined collection systems. Where separate collection systems are used for the collection of wastewater(sanitary collection systems) and stormwater(storm collection systems), wastewater flows in sanitary collection systems consist of three maior components: (D domestic wastewater.(2) industrial wastewater. and (3) infiltration/inflow Where only one collection system(combined) is used, wastewater flows consist of these three components plus stormwater. In both cases, the percentage of the wastewater components will vary with local conditions and the time of the 3-2 Wastewater Sources and flowrates Data that can be used to estimate average wastewater flowrates from various domestic, commercial, institutional, and industrial sources and the infiltration/inflow contribution are presented in this section Variations of the flowrates that must be established before collection systems and treatment facilities are designed are also discussed Domestic wastewater Sources and flowrates he principal sources of domestic wastewater in a community are the residential areas and commercial districts. Other important sources include institutional and recreational facilities. For areas n with collection systems. wastewater flowrates are commonly determined from existing records or by direct field measurements. For new developments. wastewater flowrates are derived from an analysis of Water consumption records may also be used for estimating flowrates. In the United States, on the average about 60 to 90 percent of the per capita water consumption becomes wastewater. The higher percentages( 90%)apply to the northern states during cold weather; the lower percentages(60%)are applicable to the semiarid region of the southwestern United States where landscape irrigation is used extensively. When water consumption records are used for estimating wastewater flowrates, the amount of water consumed for purposes such as landscape irrigation(that is not discharged to the collection system), leakage from water mains and service pipes, or product water that is used by manufacturing establishments must be evaluated carefully Residential Areas. For many residential areas, wastewater flowrates are commonly determined on population and the average per capita contribution of wastewater. For residenti and anticipated population densities. Where possible, these flowrates should be based on actual flow data projections for use in estimating wastewater flowrates was often the responsibility of the engineer b,? from selected similar communities, preferably in the same locate. In the past, the preparation of populatio today population projection data are usually available from local, regional, and state planning agencies Wastewater flowrates can vary depending on various situations such as economic, social. and other3-1 3 Analysis and Selection of Wastewater Flowrates andConstituent Loadings Determining wastewater flowrates and constituent mass loadings is a fundamental step in initiating the conceptual process design of wastewater treatment facilities. Reliable data for existing and projected flowrates affect the hydraulic characteristics, sizing, and operational considerations of the treatment system components. Constituent mass 1oading, the product of constituent concentration and flowrate, is necessary to determine capacity and operational characteristics of the treatment facilities and ancillary equipment to ensure that treatment objectives are met. 3-1 Components of Wastewater Flows The components that make up the wastewater flow from a community depend on the type of collection system used and may include: 1. Domestic (also called sanitary) wastewater. Wastewater discharged from residences and from commercial, institutional, and similar facilities. 2. Industrial wastewater. Wastewater in which industrial wastes predominate. 3. Infiltration/inflow (I/I). Water that enters the collection system through indirect and direct means. Infiltration is extraneous water that enters the collection system through leaking joints, cracks and breaks, or porous walls. Inflow is stormwater that enters the collection system from storm drain connections (catch basins), foundation and basement drains, or through access port (manhole) covers. 4. Stormwater. Runoff resulting from rainfall and snowmelt. Three types of collection systems are used for the removal of wastewater and stormwater: sanitary collection systems, storm collection systems, and combined collection systems. Where separate collection systems are used for the collection of wastewater (sanitary collection systems) and stormwater (storm collection systems), wastewater flows in sanitary collection systems consist of three major components: (1) domestic wastewater, (2) industrial wastewater, and (3) infiltration/inflow. Where only one collection system (combined) is used, wastewater flows consist of these three components plus stormwater. In both cases, the percentage of the wastewater components will vary with local conditions and the time of the year. 3-2 Wastewater Sources and Flowrates Data that can be used to estimate average wastewater flowrates from various domestic, commercial, institutional, and industrial sources and the infiltration/inflow contribution are presented in this section. Variations of the flowrates that must be established before collection systems and treatment facilities are designed are also discussed. Domestic Wastewater Sources and Flowrates The principal sources of domestic wastewater in a community are the residential areas and commercial districts. Other important sources include institutional and recreational facilities. For areas now served with collection systems, wastewater flowrates are commonly determined from existing records or by direct field measurements. For new developments, wastewater flowrates are derived from an analysis of population data and estimates of per capita wastewater flowrates from similar communities. Water consumption records may also be used for estimating flowrates. In the United States, on the average about 60 to 90 percent of the per capita water consumption becomes wastewater. The higher percentages(90%) apply to the northern states during cold weather; the lower percentages(60%) are applicable to the semiarid region of the southwestern United States where landscape irrigation is used extensively. When water consumption records are used for estimating wastewater flowrates, the amount of water consumed for purposes such as landscape irrigation (that is not discharged to the collection system), leakage from water mains and service pipes, or product water that is used by manufacturing establishments must be evaluated carefully. Residential Areas. For many residential areas, wastewater flowrates are commonly determined on population and the average per capita contribution of wastewater. For residential areas where large residential development is planned, it is often advisable to develop flowrates on the basis of land-use areas and anticipated population densities. Where possible, these flowrates should be based on actual flow data from selected similar communities, preferably in the same locate. In the past, the preparation of population projections for use in estimating wastewater flowrates was often the responsibility of the engineer, but today population projection data are usually available from local, regional, and state planning agencies. Wastewater flowrates can vary depending on various situations such as economic, social, and other