Infiltration/inflow, as discussed earlier in this chapter, is another source of water flow into the collection system. In most cases, the presence of this extraneous water tends to decrease the concentrations of BOD and TSS, depending on the characteristics of the water entering the sewer. In some cases, concentrations of some inorganic constituents may actually increase where the groundwater contains high levels of dissolved constituents ariations in Industrial Wastewater. The composition of wastewater from industrial operations varies widely depending on the function and activity of the particular industry. In some cases, flow values and this variation, it is often difficult to define"typical operating conditions"for industrial activities. For example, the BOD and TSS concentrations contributed from vegetable-processing facilities during the noon wash-up period may far exceed those contributed during working hours. Problems with high short-term loadings most commonly occur in small treatment plants that have limited reserve capacity to such as canneries can cause both the flow and bod loadings to If industrial wastes are to be discharged to the collection system for treatment in a municipal wastewater facility, it will be necessary to characterize the wastes adequately to identify the ranges in constituent concentrations and mass loadings. Such characterization is also needed to determine if pretreatment is collection system. If pretreatment is needed, the effluent from the pretreatment facilities must also be characterized. Further, any proposed future process changes should also be assessed to determine what effects they might have on the wastes to be discharged. Where data are not available, every effort should be made to obtain information from similar facilities. With sufficient characterization of the wastewater from industrial discharges. suitable Variations in Constituent Values in Combined Collection Systems. Flowrates, constituent concentrations, and mass loads emanating from combined collection systems can vary widely. Typical factors influencing the characteristics of wastewater from combined collection systems are shown in Table 3-10. Example variations of BOD, TSS, and fecal coliform measured in a combined system are shown on Fig 3-5, during and after a storm event As shown, the BOD and fecal coliform bacteria concentrations are low during the storm when runoff flows are high. After the storm, when runoff subsides and the flow consists primarily of wastewater, concentrations rise significantly When this rise occurs. it can be concluded that the bod and fecal coliform concentrations in the stormwater are significantly lower than in the wastewater component. Unlike BOD and fecal coliform The combined sewer systems known as the "first flush. The first flush has often been observed following the initial phase of a rainfall event in which much of the accumulated surface contaminants are washed into apable of ds. Together, the res ded material and contaminants washed off surfaces result in high contaminant concentrations. Factors known to contribute to the magnitude and frequency of the first-flush effect include combined sewer slopes; street and catch basin cleaning frequency and design; rainfall intensity and duration; and surface buildup of debris and contaminants Wastewater from combined collection systems usually contains more inorganic matter than wastewater from sanitary collection systems because of the larger quantities of storm drainage that enter the combined sewer system Tab. 10 Typical factors influencing the characteristics of combined wastewater Parameter Quantity-related factors Quality-related factors P Rainfall depth and volume Regional atmospheric quality Storm intensity Wastewater sources Flowrate and variability f contributin Type of contributing urces(residential commercial. etc Drainage basin Pollutant buildup and wash-off characteristics Land-use type Wastewater management practices Runoff control practices Sewer system, Pipe size, slope, and shape Chemical and biological transformations Inter Quantity of infiltration 93-9 Infiltration/inflow, as discussed earlier in this chapter, is another source of water flow into the collection system. In most cases, the presence of this extraneous water tends to decrease the concentrations of BOD and TSS, depending on the characteristics of the water entering the sewer. In some cases, concentrations of some inorganic constituents may actually increase where the groundwater contains high levels of dissolved constituents. Variations in Industrial Wastewater. The composition of wastewater from industrial operations varies widely depending on the function and activity of the particular industry. In some cases, flow values and water quality measurements may vary by several orders of magnitude over a period of a year. Because of this variation, it is often difficult to define "typical operating conditions" for industrial activities. For example, the BOD and TSS concentrations contributed from vegetable-processing facilities during the noon wash-up period may far exceed those contributed during working hours. Problems with high short-term loadings most commonly occur in small treatment plants that have limited reserve capacity to handle "shock loadings." The seasonal impact of industrial wastes such as canneries can cause both the flow and BOD loadings to increase from two to five times average conditions. If industrial wastes are to be discharged to the collection system for treatment in a municipal wastewater facility, it will be necessary to characterize the wastes adequately to identify the ranges in constituent concentrations and mass loadings. Such characterization is also needed to determine if pretreatment is required before the waste is permitted to be discharged into the collection system. If pretreatment is needed, the effluent from the pretreatment facilities must also be characterized. Further, any proposed future process changes should also be assessed to determine what effects they might have on the wastes to be discharged. Where data are not available, every effort should be made to obtain information from similar facilities. With sufficient characterization of the wastewater from industrial discharges, suitable pretreatment facilities can be provided and plant upsets can be avoided. Variations in Constituent Values in Combined Collection Systems. Flowrates, constituent concentrations, and mass loads emanating from combined collection systems can vary widely. Typical factors influencing the characteristics of wastewater from combined collection systems are shown in Table 3-10. Example variations of BOD, TSS, and fecal coliform measured in a combined system are shown on Fig. 3-5, during and after a storm event. As shown, the BOD and fecal coliform bacteria concentrations are low during the storm when runoff flows are high. After the storm, when runoff subsides and the flow consists primarily of wastewater, concentrations rise significantly. When this rise occurs, it can be concluded that the BOD and fecal coliform concentrations in the stormwater are significantly lower than in the wastewater component. Unlike BOD and fecal coliform bacteria, TSS concentrations rise slightly during the storm, and remain unchanged after the storm. The slight rise in the TSS concentration during the peak flow may be due to a phenomenon common to many combined sewer systems known as the "first flush." The first flush has often been observed following the initial phase of a rainfall event in which much of the accumulated surface contaminants are washed into the combined system. In combined collection systems, the increased flows may be capable of resuspending material deposited previously during low-flow periods. Together, the resuspended material and contaminants washed off surfaces result in high contaminant concentrations. Factors known to contribute to the magnitude and frequency of the first-flush effect include combined sewer slopes; street and catch basin cleaning frequency and design; rainfall intensity and duration; and surface buildup of debris and contaminants. Wastewater from combined collection systems usually contains more inorganic matter than wastewater from sanitary collection systems because of the larger quantities of storm drainage that enter the combined sewer system. Tab. 10 Typical factors influencing the characteristics of combined wastewater Parameter Quantity-related factors Quality-related factors Precipitation Rainfall depth and volume Storm intensity Storm duration Regional atmospheric quality Wastewater sources Flowrate and variability Type of contributing sources(residential ,commercial, etc) Type of contributing sources Drainage basin characteristics Size, time of concentration Land-use type Impervious area Soil characteristics Runoff control practices Pollutant buildup and wash-off Wastewater management practices Sewer system, interceptor design Pipe size, slope, and shape Quantity of infiltration Chemical and biological transformations Quality of infiltration