Unflushables: designing new intervention pathways for sewer blockages and environmental pollution in the Anglian Water region, UK

What are unflushables? This report addresses the topic of unflushables, products commonly found to be causing problems in sewerage and water systems having been disposed of via the toilet. The most problematic unflushables include a variety of wet wipes (also known as wet towels, moist towelettes, baby wipes and used for a range of bodily and household purposes) and menstrual absorbents (e.g. sanitary pads, tampons and applicators). Other products include incontinence pads, cotton buds, condoms, bandages, disposable nappies, syringes, razors, and dental floss. These products cause damage to wastewater treatment systems and contribute to sewer blockages.

What is the problem? In the UK, the cost of fixing sewer blockages reaches £88 million per year and around half of these blockages are caused by unflushables. Aside from the expense, blockages can contribute to flooding of wastewater systems, resulting in damage to properties and the environment. Often unflushables are not contained by wastewater retention systems and end up on our shores and in our water streams, contributing to aquatic ecosystem pollution. Flushing toilets are a substantial component of UK water demand, and disposal of unflushables via the toilet increases demand for toilet flushing. In each flush, water that has been treated to drinking water standard is used to remove products that could be disposed of in other ways (e.g., via solid waste streams). At the same time, water efficiency activities – particularly low flow toilets – reduce the input of water into sewer systems, impacting on the ‘self-cleansing’ of blockages within the sewer systems under conditions on reduced water flow. As the UK moves towards lower levels of domestic water use as standard, a projected increase in water efficiency activities to reduce use in periods of drought, and increased impact of climate change on watercourse flooding through storm events, there is a need to reduce the inappropriate disposal of unflushables.

How and why have unflushables become a challenge in our sewers? Unflushables present a distributed problem, one that is not the direct consequence of individual behaviour, product design or infrastructural decline, but the outcome of myriad social, cultural and material developments in society (Box 1). The formation of blockages in sewers is a complex process in which unflushable products combine with fats, oils and greases (FOG) and other solids in the sewer. There are infrastructural factors, such as the size of pipes and velocity of wastewater flows; and material dimensions including the design of unflushable products, how readily they breakdown, and the design of the spaces in which they are used. There are also social aspects to the unflushables challenge. These include cultural and gendered diversity in cleanliness practices; the historical evolution of conventions around cleanliness and hygiene; infrastructural imaginaries and expectations; and political dimensions of infrastructural development and maintenance...