Hydraulic Performance Assessment Of Sewer System: The Case Of Kazanchis Addis Ababa, Ethiopia

Abstract

Sewage Is A General Term Used For Wastewater From Homes, Commercials, And Industries. And Sewer System Is A System That Is Designed To Adequately Collect And Transfer The Sewage To A Treatment Plant For Treatment And Disposal Or Reuse Safely. Although Addis Ababa City Provides Sewer Service To Its Residents By Connecting Their Internal Sewer Lines To The Sewer Network, The Level Of Service Is Still Very Low And Is Around 29%. The Study Area Of Kazanchis, Addis Ababa Is Characterized By Dynamic Change, In Terms Of Population Structure And Land Use Causing An Increase In Water Demand, Consumption, And Sewage Production. Some Sewer Overflows, Manholes Below Minimum Cover Constraint, And Broken Or Lost Manhole Covers Are Major Problems In The Area. Accordingly, The Main Purpose Of This Research Was To Evaluate The Hydraulic Performance Of The Existing Sewer System In The Area, Considering The Uncertainties Involved In Selecting The Design And Analysis Parameters. It Was Also Important To Check Its Present Performance And Its Capacity To Withstand Future Change. In This Study, The Current Sewer Network Is 7238 M With Upvc Circular Pipes Of 200mm, 250mm And 400mm In Diameter. The Ground Elevation Of Manholes Was Collected Using Gps And The Sewer Load For The Full Network Was Calculated From The Water Supply Billing Data Of Service Customers Of Aawsa. The Total Water Consumption Calculated From The Water Customers Of The Area That Are Connected To The Existing Network Is 16.82 L/Sec. A Model Has Been Established For An Existing Network Using Bentley Sewercad V8iand The Loading Simulated Is A Total Average And Peak Sewage Flow The Outfall Of The Network Is 13.46l/S And 33.65 L/S Respectively. The Minimum Velocity Is Found To Be < 0.6m/S For 56.9% Of The Pipes Which Do Not Satisfy The Minimum Design Constraint During Both Average And Peak Flow Thus It Is Said That An Overflow Is Occurring Due To The Deposition Of Tree Roots, Accumulation Of Fats, And/Or Other Objects Failure And Failure Of Inspection And Removal Of This Accumulations. Even Though The Current Performance Of The System At Peak Flow For The Currently Existing Load Assures Its Adequacy In Terms Of Size, Slope, And Minimum Velocity Is Not Acceptable. The Analysis Predicted That The Sewer Networks Will Not Be Sufficient For Future Development.