Design of Sanitary Wastewater Collection Networks

Assume saturated project areas for population density and ultimate sewage flows; set the design period by material age; conduct field surveys and soil borings to guide sewer design.

Identify the final connection point for a sanitary sewer by linking to an existing manhole or the inlet of a sewage treatment plant, guided by elevations and survey data.

Understand the cylindrical manhole structure formed by multiple rings with side openings, a fixed frame and removable cover, and how drop manholes resolve elevation differences to minimize excavation.

Identify manhole locations at ends of lines and intersections, with changes in size, direction, or grade, and space them by pipe diameter using maximum distances 120, 150, and 180.

Set trench width Bd from pipe diameter Bc, Bd = Bc + 800 or Bd = Bc + 600; align sewers along centerlines away from utilities, 150 mm sand bedding.

Define alignments and flow directions for sanitary networks using topography, gravity flow, and costs, then apply numbering conventions for lines and manholes, including main lines, branches, and inlets and outlets.

Explore pipe materials: asbestos cement, ductile iron, reinforced concrete prestressed concrete, PVC, vitrified clay, and design sewage flows using peak domestic sewage, infiltration, P, q, F, Harmon and Babbitt formulas.

Learn how the Chezy–Manning flow formulas compute velocity and discharge in full sewer flow, using hydraulic radius, wetted perimeter, and the Manning equation and nomograph with a practical example.

Examine partial flow in sewers where depth and slope create full, pressurized conditions; use Manning's equation and d/D, q/Qf, v/vf indicators to assess design against velocity criteria.

Define sanitary sewer design criteria based on local codes, including minimum sewer size and building sewer connections, and maintain velocities between 0.3 and 3 m/s by adjusting slope.

Set sewer slopes to maintain flow velocity within limits; for a 200 mm pipe, min slope is 0.005 and max 0.05, while ensuring basement depths and minimum cover.

Design sanitary sewer network for residential area using an Excel sheet, applying 102 litres per capita per day wastewater and velocity 0.3 to 3 m/s with 100 millimetre sewer size.

Trace branches from manholes to map sanitary wastewater networks, name lines (line five, line seven, 7A, 7.1, etc.), finish branches before moving on, and assign survey or assumed lengths.

Explore how population density and accumulated population across hectare areas drive the design of wastewater lines between manholes, calculating flows for each segment.

Compute population as the area times population density (persons per hectare) for each line, then accumulate populations along lines to update each branch and manhole.

Calculate the design flow by applying the Babbitt and Harmon peak-factor formulas using population in thousands and accumulated flows, then derive average flow from wastewater production divided by 1000.

Compute design flow for sanitary wastewater networks using absolute references in formulas to copy flows, convert units, and accumulate branch flows into main lines.

Set sewer diameter to 100 millimeters and select slope within the minimum to maximum range, using the minimum or 0.01 higher.

Compute full velocity (Vf) and full flow (Qf) in a sewer using the Manning equation, with R = D/4 and A = πD^2/4 to derive Vf and Qf.

Explain flow percentages in wastewater networks using Q over Qf and Manning equation, and adjust diameters from 100 to 300 mm to achieve a 70% optimum for Q/Qf and d/D.

use vlookup to map q/qf to d/d and v/vf from a reference table, interpret the results to assess pipe diameter adequacy and adjust diameters as needed.

Calculate the actual velocity of sanitary sewer flow and keep it between 0.3 and 3 m/s; adjust slope to raise velocity when needed.

Explore sewer layout by linking ground surface and invert elevations, define upper and lower manholes, and apply equalities between main line and branch manholes.

compute sewer invert elevations for sanitary networks by calculating manhole inverts from ground elevation, minimum cover, and pipe diameter, then propagate along the main line with slope and length.

Follow sewer layout by linking invert elevations of manholes between main line and branch, copying equations to propagate changes, and keeping slopes within the maximum while preserving existing fixed elevations.

Design sanitary wastewater networks by calculating manhole depths from ground and invert elevations, adjusting slopes in small steps, and verifying Q over Qf, d over D, and velocity.

Design with additional flows adds industrial, commercial, or institutional discharges to manholes, recalculating design flow, diameters, and slopes to keep velocity and Q over Qf within limits.