Inflow/infiltration strategic management project

Wady, Ivan (2014) Inflow/infiltration strategic management project. [USQ Project]


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The impact of inflow and infiltration on hydraulic capacity of sewerage systems has long been known. Numerous attempts are made by sewer system operators to reduce the total flow contributed to the wastewater stream to be that of only domestic wastewater. This process of reduction can be a costly and non-beneficial exercise if not implemented correctly. The development and implementation of well-planned short and long term abatement programs will ensure an efficient and effective service for the community.

To develop a strategic management plan it is important to understand the historical design parameters that were used for the system development. In recent years sewer design codes have been developed to provide best practice methods that rely on the use of hydraulic models to simulate the actual system characteristics. These models attempt to replicate the actual system performance with local climatic characteristics.

The majority of sewer systems are designed to convey effluent via gravity flow. As a result of rainfall and groundwater, additional flows enter the system via pipe joints, cracks and illegal stormwater connections. This additional flow in known as Inflow/Infiltration (I/I) and during periods of heavy rainfall excessive I/I can occur. This results in failure of the sewerage network and effluent escaping to the surrounding environment. The design codes have traditionally incorporated defined values for I/I, these values are empirically included into the design to ensure that the system has adequate capacity to prevent overflows from occurring. The I/I values are not customised to the local climatic conditions and this may be the cause of high I/I during heavy rainfall causing failure of the sewer system.

Various case studies have been undertaken in recent years in the development of the models to customise the Inflow/Infiltration (I/I) values. These values are adopted for the design and operation to suit local climatic conditions. Case studies also provide knowledge of the lessons learnt from abatement strategies and the most effective means to identify and reduce high I/I in catchments.

The project uses a known problematic catchment within the Shoalhaven Water network and establishes baseline data of average flow during dry and wet periods.

This data is used with rainfall events to determine the peak weather flows associated with actual rain events.

A methodology is developed from best practice guidelines to undertake a field analysis of the problematic catchment. This enabled a trail investigation to be conducted during a wet weather event. The field results are analysed and the methodology is reviewed to determine the success of the detection of I/I flows as being a result of infiltration or inflow.

Rectification measures will be developed to provide the largest reduction of I/I that is cost effective and obtainable. This also includes improvements that can be made to the design guidelines, gathering/processing of data, field investigations and rectification measures.

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Item Type: USQ Project
Item Status: Live Archive
Additional Information: Bachelor of Engineering (Environmental) project.
Faculty/School / Institute/Centre: Historic - Faculty of Health, Engineering and Sciences - School of Civil Engineering and Surveying (1 Jul 2013 - 31 Dec 2021)
Supervisors: Aravinthan, Vasanthadevi
Date Deposited: 09 Sep 2015 05:17
Last Modified: 09 Mar 2016 05:33
Uncontrolled Keywords: catchment inflow; catchment infiltration; wastewater; sewerage systems; effluent; rainfall; Shoalhaven City Council; New South Wales
Fields of Research (2008): 09 Engineering > 0907 Environmental Engineering > 090701 Environmental Engineering Design
Fields of Research (2020): 40 ENGINEERING > 4011 Environmental engineering > 401199 Environmental engineering not elsewhere classified

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