The Environment Agency has refused an application by United Utilities to vary an existing environmental permit at its Blackburn Wastewater Treatment Works (WwTW) in Samlesbury, Lancashire.

The purpose of the application was to enable acceptance of up to 2,628,000 wet tonnes poer year of indigenous raw sludge produced at the adjacent WwTW and imported sewage sludges.

Setting out the reasons for its decision, the Environment Agency said it was not satisfied that the following conditions had been met:

• the water company’s proposals would achieve a high level of protection of the environment taken as a whole;
• that all appropriate preventative measure would be taken against pollution and;
• the Best Available Techniques would be applied.

BAT is usually considered to be affordable across the industry sector as a whole for both newly built plant and a “typical” existing plant.

The environmental regulator said that United Utilities had not satisfactorily demonstrated that it was using BAT to prevent, or where that was not practicable, reduce emissions to soil and water in relation to:

• provision of impermeable surfaces
• provision of techniques to reduce the likelihood and impact of overflows and failures from tanks and vessels
• design and maintenance provisions to allow detection and repair of leaks

The refusal notice also sets out the Environment Agency’s concerns about United Utilities’ proposal to prevent or reduce emissions to air – dust, organic compounds and odour in particular.

The Environment Agency takes the view that the water company had failed to demonstrate that the assets associated with the acceptance of sludge from the Nereda system – identified as two enclosed sludge reception tanks, drum thickeners and lamella tank – met BAT or proposed suitable alternatives to provide the same level of environmental protection. Operation of the Nereda assets was proposed to commence operation in 2022.

The Environment Agency also pointed out that no evidence had been provided by United Utilities that the Nereda assets had been designed and built to CIRIA standards - or to at least an equivalent standard. CIRIA C736 guidance is considered the industry standard of choice and is based on the source-pathway-receptor approach to risk assessment.

United Utilities already holds an environmental permit at the site which authorises the combustion of biogas – used principally as a fuel or other means to generate energy. The water company had applied to the Agency to add the following installation and waste activity:

• recovery or mix of recovery and disposal of non-hazardous waste with a capacity exceeding 100 tonnes per day involving biological treatment – specifically, the anaerobic digestion process
• physical treatment of non-hazardous waste relating to acceptance of digested sludge

The activity applied for included an anaerobic digestion (AD) stationary technical unit (STU) and the following directly associated activities:

• pre and post-digestion treatment
• gas collection and storage
• combined heat and power (CHP) engine and boilers
• emergency flare
• raw material storage
• process/surface water collection

As part of its application United Utilities had identified the following key risks with regard to emissions to soil and water:

• leaks/spills from treatment process and plant
• leaks/spillages from connective pipelines
• spillage of sludge
• failure of any of the pipework on the installation
• loss of containment of vessels

Explaining the reasons for its decision to refuse the application, the EA said it had given United Utilities “numerous opportunities” to provide the Agency with further information to a satisfactory standard to enable it to make a properly informed determination – but the information had not been forthcoming.

The Agency commented:

“We consider that we have offered a greater degree of flexibility and advice to the applicant than would normally be given to applicants during a determination of this nature.

“We have determined the application based on the information provided by the applicant and consequently we have decided to refuse the application.”

Click here to download the EA’s full decision document