Client: Regency Living
Location: Forest Glades, Dorset
Project: This project successfully restored a failing sewage treatment system to full operational compliance while enhancing natural drainage and environmental protection through carefully engineered refurbishment and ditch reinstatement works.
Project Background
Mantair Ltd were appointed by Regency Living to carry out the refurbishment of an existing Marsh sewage treatment plant at Forest Glades, Dorset. The system was suffering from operational failure, poor historical installation practices, and significant hydraulic issues caused by high groundwater levels and blocked surrounding ditches.
The brief was to restore the treatment plant to full operational compliance, improve long-term reliability, and reinstate natural drainage routes to protect both the system and the surrounding environment.
The Challenge
A detailed site inspection identified that the existing sewage treatment plant was not functioning correctly and posed a risk of environmental pollution. Key issues included:
- Non-standard and excessively raised risers restricting safe access for maintenance;
- Uneven and ineffective aeration caused by failed pipework and diffusers;
- Complete loss of aeration in secondary treatment zones;
- A blocked recirculating airlift preventing correct biological treatment;
- An incorrectly installed blower kiosk with poor ventilation and exposed services;
- Multiple failed or underperforming blowers from mixed manufacturers;
- A gravity outlet vulnerable to backflow due to high groundwater levels.
In addition, surrounding ditches had become blocked or infilled over time, causing surface and groundwater to pool around the treatment plant. During periods of heavy rainfall, this increased the likelihood of backflow into the system and further compromised treatment performance.
Our Solution
Mantair Ltd designed and delivered a comprehensive refurbishment and upgrade solution, addressing both the mechanical performance of the treatment plant and the wider site drainage constraints.
Sewage Treatment Plant Refurbishment
- Full emptying of the treatment plant with tanker support to allow safe man-entry;
- Confined space working with gas monitoring, rescue team and full PPE protocols;
- Internal CCTV inspection of all chambers prior to works;
- Removal of existing media, diffusers and damaged pipework;
- Installation of new diffusers and inspection of all internal pipework;
- Clearance and refurbishment of the recirculating airlift;
- Sealing of the existing gravity outlet to prevent groundwater ingress;
- Installation of new retrofit pump kits to upgrade the system to a pumped discharge;
- Full internal clean and recommissioning of the treatment plant.
Blower & Kiosk Upgrade
- Removal of the existing kiosk, concrete base, blowers and air mains;
- Installation of two new single-door kiosks on new concrete bases;
- Installation of four new air blowers;
- New ducted air mains and electrical services installed correctly through kiosk bases;
- Installation of a high-level alarm for enhanced system protection.
All electrical works were completed and certified by Mantair’s approved NICEIC contractor.
Ditch Clearance & Environmental Improvements
To resolve the site’s hydraulic constraints and protect the upgraded treatment system, Mantair reinstated the natural drainage network surrounding the plant:
- Clearance of two significant blockages within existing ditches;
- Reinstatement of the rear ditch running parallel;
- Re-establishment of flow to a natural reed bed, providing additional natural filtration;
- Reduction of standing water around the treatment plant and outlet.
These works restored historic drainage routes, reduced groundwater pressure on the system, and significantly improved long-term operational resilience.
Health, Safety & Planning
Given the complexity of the works, Mantair managed the project under strict health and safety controls, including:
- Full RAMS, Construction Phase Plan and confined space procedures;
- Controlled site set-up with fencing, welfare and traffic management;
- Detailed photographic records before, during and after works;
- Close liaison with Regency Living and relevant stakeholders throughout.
The project was carefully programmed to align with Environment Agency requirements, including landowner consultation periods for ditch reinstatement.
The Result
The refurbished sewage treatment plant at Forest Glades is now fully operational, compliant and resilient to high groundwater conditions. The system delivers effective biological treatment, prevents backflow, and discharges safely via reinstated natural drainage routes.
Key outcomes include:
- Restoration of compliant treatment performance;
- Reduced environmental risk and improved discharge quality;
- Improved access for future maintenance;
- Enhanced reliability and longevity of the system;
- Environmentally sensitive drainage improvements using natural reed beds.
Client Outcome
By refurbishing and upgrading the existing infrastructure rather than replacing it entirely, Regency Living achieved a cost-effective, sustainable solution that protects both residents and the surrounding environment while meeting regulatory expectations.
