Recycling Coagulant Sludge from Water Treatment

In this WRc Portfolio project funded by UK water companies, WRc explored the recycling options for coagulant sludge in order to improve the sustainability of water treatment operations across the water industry.

Evaluated

current sludge recycling data as well as possible future options and their economic implications

Informed

UK water companies of current and possible future end-of-waste routes, including alternatives to recycling

Encouraged

further investigation into the technical and economical feasibility of identified sustainable solutions

Addressing the challenge of an underutilised material

The UK water industry produces over 90,000 tonnes dry solids of coagulant sludge annually via the potable water treatment process. This sludge, though potentially valuable, is currently underutilised and recycling of this stream presents an opportunity to improve the sustainability of water treatment operations.

Finding solutions for more sustainable water treatment

To address this challenge, a WRc Portfolio project funded by several UK water companies was initiated with the aim of expanding knowledge and exploring recycling options for alum and ferric coagulant sludges. The project had three key objectives:

Producing a national dataset

The project team collected existing data on the characteristic properties of different types of coagulant sludges, benchmarked the characteristics against other commonly recycled organic materials, and identified knowledge gaps.

Identifying favourable recycling options

An extensive assessment was conducted, evaluating various established and novel recycling options within and outside the UK, to create a prioritised list of options with the greatest potential for single, blended, or amended waste streams. From this list, potential recycling options, suitable for use at either centralised (large) or localised (small-size) treatment centres, were selected for further investigation.

Conducting a cost analysis

To evaluate the economic viability of the selected recycling options, the project team performed a detailed evaluation of their benefits, limitations, and basic cost implications. A simple cost evaluation exercise was carried out, considering the size and capacity of the treatment works, to determine the suitability of each recycling option.

Project outcomes informing circular economy strategies

1. The quantity of alum sludge and ferric sludge landfilled or recycled annually was quantified.
2. Basic compositional datasets were collated – e.g. dry solids, volatile solids, aluminium, iron, other metals, nutrients and organic matter.
3. The feasibility of an end-of-waste route for recycling coagulant sludge was assessed.
4. A significant number of alternative applications were identified such as reed bed treatment, in constructed wetlands systems, composting for use on agricultural land or as a soil improver.

WRc recommended further research to investigate the technical and economic feasibility of the identified recycling options in collaboration with industry stakeholders.

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WRc Portfolio

Portfolio allows companies to share knowledge and jointly fund research focused on specific needs in the industry, from operational problems and regulatory issues to preparation for future challenges. It has been running for over 20 years, with project ideas being proposed by experts within WRc, based on contact with our clients across the industry.

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