Challenges of treating and dispersing the effluent at Castle Dargan

When planning wastewater treatment in hospitality settings, effluent quality and land integration present unique challenges, especially when dealing with both greywater and stormwater runoff.

At Castle Dargan Estate, onsite monitoring showed consistently high levels of COD (Chemical Oxygen Demand) and organic pollutants, along with strong cleaning agents commonly used in hotel operations. While effluent composition remained stable throughout the day, peak flow rates required careful consideration when sizing both the MBBR treatment system and the subsurface PED dispersal area.

The proposed treatment plant location offered ample space for multiple below-ground tanks. The only limiting factor was a small stream area, which influenced the final position of the supply tank and pump skid.

In collaboration with the client, the plant was designed with future expansion in mind—a requirement clearly outlined in early project meetings.

The most significant challenge came in identifying a suitable 2.0-hectare area to safely and sustainably disperse up to 70m³ of treated effluent daily using a subsurface PED system.

While the initial plan proposed installing the dispersal system under the 9th fairway, concerns about disrupting the golf course led to re-evaluation. After consultation with the head greenkeeper and careful consideration of course integrity, the solution was clear: the driving range.

Now, the driving range integrates 2,500m of subsurface drip line installed at 600mm depth. Typography, groundwater table sampling and a full hydrological report confirmed that the saturation levels of the proposed site were ideal from the PED. This shows the importance of data-driven site planning to ensure compliance and performance of subsurface effluent dispersal systems.

MBBR technology at the Castle Dargan Estate

At the heart of the MBBR system is free-floating plastic biomass carriers called biomedia, which provide a surface area for biomass to attach. These helpful bacteria and microorganisms break down organic compounds present in the wastewater.

For this installation, Warden Biomedia’s Bioflo+ filter media was selected—a premium solution known for high efficiency and installer confidence.

Key advantages of Bioflo+:

• 800m²/m³ surface area – the highest in its class, ideal for effective biofilm growth
• Internal fins – protect the biofilm while maximising contact with the wastewater
• Open structure – ensures optimal water flow and oxygen exchange
• Specific gravity of 0.96 – offers ideal buoyancy for even distribution in MBBR tanks

This choice helped meet the client’s requirement for high treatment performance while supporting future expansion.

Modular MBBR plant design

To protect Lough Dargan and nearby watercourses, treated wastewater at the Castle Dargan Estate site is pumped to a dedicated dispersal area using a Precision Effluent Dispersal (PED) system installed beneath the driving range. The system uses flexible dripline with pressure-compensating (PC) emitters, buried 200–500mm deep, to distribute effluent slowly and evenly across a large area. Unlike outdated PVC percolation systems, this modern subsurface method eliminates leaks, surface ponding, runoff, and soil erosion. It also offers a more sustainable and environmentally safe alternative to surface water discharge, significantly reducing nutrient loading in sensitive water bodies.

Designed for performance, proven in the field!

The new MBBR plant was successfully commissioned in July 2024. Biomedia seeding with a specialist bacterial culture ensured rapid biofilm development, and by the time the primary settlement tank reached capacity, the system was consistently producing high-quality treated effluent suitable for subsurface PED dispersal. The plant achieved COD removal rates of approximately 99%, with effluent levels well below the target of 100mg/L—demonstrating the reliability and performance of the MBBR process from day one.

Bosta UK supplied the PED System, and JCR Water supplied the new WWTP with Montgomery EHS (MEHS) as the designer of the system.