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sewer main is reached. Then repeat steps 3 to 12 for the sewer main until the connection to the next lateral is reached 14. Repeat steps 3 to 13, beginning with the outermost pipe in the next sewer lateral. Continue designing the sewer main until the outlet point of the sewer system is reachecd The design procedure described here is usually automated to some degree and is most ly implemented using a spreadsheet program. The design procedure is illustrated by the following example EXAMPLE 3.32 wer system is to be designed to service the residential area shown in Figure 3.56 he average per-capita wastewater flowrate is estimated to be 800 L/d/person, and the infiltration and inflow (I/1) is estimated to be 70 m3/d/km. The sewer system is to jon an existing main sewer at manhole (MTI) 5, where the average wastewater flow is 0.37 m%, representing the contribution of approximately 100,000 people contribution main at MI1 5 is 1065 mm in diameter, has an inyert elevation of 55.35 m, and is laid on a slope of 0.9%. The layout of the proposed sewer system Section 3.6 Design of Sanitary Sewers 249 . The I/I to the flow in the main sewer at MH 5 is negligible. The existing sewer shown in Figure 3.56 is based on the topography of the area. Pipe lengths, contributing areas, and ground-surface elevations are given in the following table Ground surface elevation UpperLower Manhole no.Length Contributing end end area (ha) (m) Line tion From o(m) no Main Street 60.04 1 A Street A Street A Street 4 A Street 65.00 63.80 62.40 60.04 61.88 60.04 60.04 60.04 63.80 62.40 0.47 0.50 0.44 0.90 0.17 2 100 89 Main Street 65.08 63.20 63.60 63.20 63.20 62.04 62.72 62.04 62.04 60.04 61.88 60.04 60.04 60.20 58 6 B Street 7PAvenue 8 B Street 9 Q Avenue 10 | B Street 0.39 0.88 0.45 0.90 0.28 12 12 11 BStreet 12 Main Street12 125
Explanation / Answer
I/I is inflitration and inflow it will be same for all the entries. there will a length entry. multiply 75 with every km that you have. if we have length 100km then I/I will be 7500 m3/d. now for the next length it will be again length * I/Ifor total flow it will be incremental.
