Sewerage

Modelling Sewer Inlet Capacity Restrictions - Modelling Guide

Reference: 23/SW/01/27-(1)
ISBN: 978-1-84057-990-1
Published Date: 01/01/2099

This new 1D modelling approach has been devised by combining the findings from the literature review and the development of semi-empirical relationships from academic studies investigating factors that affect inlet capacity, utilising the modelling functionality of InfoWorks Integrated Catchment Modelling (ICM) software, which is the most commonly used tool by the UK water industry. 
The new approach was developed to meet the following requirements:
•    Evidence-based approach;
•    Focus on restrictions caused by road gullies (on the basis that no evidence was found as part of this project to justify modelling restrictions from roof drainage);
•    Applicable to existing and new build Type II 1D hydraulic models (i.e. models used for drainage planning purposes);
•    Based on readily available gully data, without the need for additional survey;
•    Simple method(s) based on current InfoWorks ICM software capabilities representing two hydraulic mechanisms:
o    Runoff bypassing a gully on a steep road and never entering the sewerage system, and 
o    Water ponding over a gully and attenuated before draining into the sewerage system.
•    Represents gullies that are partly blocked or not operating as designed.

Understanding the scale and impact of privately owned drains and sewers on sewer capacity

Reference: 23/SW/01/24
ISBN: 978-1-84057-973-4
Published Date: 23/04/2024

It is important to invest in reducing storm overflow usage to create a sustainable water environment. Groundwater infiltration directly into the public wastewater network is a known cause of increased storm overflow, but the contribution arising from infiltration into the private network is unknown.

The length and condition of private pipes that carry foul water, surface water, or a combination of the two is unknown. However, the private sewer network is believed to be longer than the public sewer network. Furthermore, private pipes are likely to be in a worse condition than the public network due to lack of inspection and maintenance.

To help ensure investment decisions are informed and targeted to maximise value with the goal of eliminating uncontrolled discharges from sewers by 2050, this UKWIR project led by Frazer-Nash Consultancy, and in collaboration with Bath University, has:

• developed a national model that can estimate the length, condition, and material type of privately owned wastewater drainage pipes.
• combined predictions for privately owned wastewater drainage pipes and water levels to estimate the volume of infiltration resulting from leakage in domestic wastewater pipes on a national scale.
• compared the estimated cost and benefits of improving the condition of pipes in the private network to reduce groundwater infiltration with the cost of increasing the capacity of the public network to deal with the increased load.

Learning and recommendations from customer behaviour campaigns on blockage reduction

Reference: 23/SW/01/28
ISBN: 978-1-84057-992-5
Published Date: 20/12/2023

The issue of uncontrolled discharges from sewer overflows has generated strong media interest over the last 3 years. The frequency of these discharges continues to be under significant regulatory, political and media scrutiny.

Blockage reduction represents one part of the solution to this challenge, with water companies across the UK and Ireland needing to find ways of changing customer behaviour, addressing key barriers to the disposal of fats, oils and greases, and other blockers such as wet wipes.

In this study, we gathered insight from across the water industry into the effectiveness of current and past behaviour change campaigns undertaken by individual water companies (and other organisations in the sector), with the aim of identifying what works.   

Above all, this research indicates that there is still much work to be done to develop effective behaviour change interventions on blockage reductions.

A series of foundational steps are required at an industry level if we are to develop evidence-based approaches to tackling this huge challenge.

The project highlights the need for a strategic and disciplined approach to blockage campaigns to enable the industry to both monitor and improve effectiveness and maximise return on investment.