Existing Reed Bed System Assessed for New Residential Development – Capacity Found Insufficient
When a developer planned new homes on a former business park site, WCI Water & Wastewater Engineers was appointed to assess whether the existing treatment system could support the new development.
Summary
- 57 PE - the existing system's design capacity
- 184 PE - the capacity required by the proposed 26-home development
- 175–200m² - existing reed bed area; 920m² minimum required for the new flows
- 4 package treatment plant manufacturers consulted on replacement options
Project in numbers
57 PE
Existing system capacity
184 PE
Capacity required by the proposed 26-home development
175–200m²
Existing reed bed area
920m²
Minimum required for the new flows
4
Package treatment plant manufacturers consulted
Overview
A developer engaged WCI Water & Wastewater Engineers to assess whether the existing private sewage treatment system on a former business park site could be repurposed to serve a proposed development. The site had a long and complex operational history, with the current treatment system having been designed and installed by WCI back in 2010 for a very different pattern of use.
The Challenge
The existing system – comprising a primary tank, six horizontal flow reed beds, pond and clarifier – had been designed in 2010 to serve 14 full-time residents and a business park population equivalent of 57 PE. The proposed residential development would generate a population equivalent of 184 PE using the same British Water Flows and Loads 4 methodology. The reed beds, measuring approximately 175–200m² in total, were showing signs of stress. The developer needed a clear technical answer on capacity, compliance and the path forward before committing to the development.
The WCI Solution
WCI Water & Wastewater Engineers carried out a full assessment of the existing system against the requirements of the proposed development. The capacity analysis was unambiguous: a 184 PE residential development would require a minimum reed bed area of 920m² to provide adequate secondary treatment – more than four times the existing provision. The existing system was not suitable for reuse for the proposed development. With no public sewers confirmed in the vicinity of the site, on-site treatment would be required regardless.
The Outcome
The assessment provided the developer with a technically robust, clearly evidenced conclusion: the existing system could not serve the proposed development, and a new package sewage treatment plant with an Environmental Permit would be required.
The options appraisal gave the developer the information needed to select the most appropriate treatment solution and proceed with confidence.
To discuss your installation or groundworks project, contact WCI today.
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