The Environment Agency has launched a new consultation on an application by United Utilities to vary an existing environmental permit for its Ellesmere Port Wastewater Treatment Works (WwTW) sludge treatment facility involving “substantial change.”
The water company’s existing permit under the Environmental Permitting (England and Wales) Regulations 2016 for the Ellesmere Port WwTW currently allows the operation of the biogas Combined Heat and Power (CHP) plant and flare as waste activities, along with other directly associated activities.
The sludge treatment activity has not previously required an environmental permit as the digested sewage sludge from the site is normally sent for recovery to land. However, United Utilities has submitted the application based on the Environment Agency’s recent conclusion that sewage sludge is a waste and therefore the treatment of sewage sludge by anaerobic digestion for recovery is a permittable activity.
Announcing the consultation, the Environment Agency said the application to vary an environmental permit under the Environmental Permitting (England and Wales) Regulations 2016 involved “substantial change” at the regulated facility.
United Utilities has applied for the variation for re-designation of the facility to an installation undertaking treatment of sewage sludge for recovery, including the screening, thickening and anaerobic digestion of indigenous and imported sewage sludge at the Ellesmere Port works.
Combustion of biogas produced at the facility is already permitted as a waste operation and no changes are proposed to this operation. The biogas is combusted in two on-site combined heat and power (CHP) engines, generating electricity for the process, and three boilers, generating heat and steam for the process.
The waste treated consists of sludges imported from other WwTWs and indigenous sludges produced from Ellesmere Port WwTW (on-site) from the urban wastewater flow.
Additional associated activities include:
- Raw sludge storage;
- Sludge screening (solids separation);
- Sludge thickening by gravity belt thickeners (GBTs);
- Dewatering of digested sludge by centrifuge;
- Sludge and digested sludge cake storage;
- Raw material handling and storage;
- Storage and combustion of biogas in CHP engines and boilers;
- Flaring of excess biogas;
- Siloxane removal from the biogas;
- Disposal of process liquors; and
- Odour abatement.
The additional permitted activities require a change to the current permit boundary and a new layout and emissions point plan for the site. The activities already authorised under the permit remain operational.
The variation includes the requirement for effluent from the sludge treatment process to be returned to the head of the WwTW flow to full biological treatment. The effluent returned primarily comprises filtrate from the GBTs, filtrate from SAS thickeners and centrate from the centrifuges. Lower volume constituents include: biogas condensate, boiler blowdown, leachate from the contingency cake bay and surface water drainage (including rainfall).
Deadline to comment on the consultation is 18 September 2023. Click here to access the consultation documents and comment online
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