A crocodile conservation zoo in Oxfordshire has enhanced its onsite wastewater treatment capabilities with the installation of a bespoke HiPAF system designed and manufactured by WCS Environmental Engineering (WCSEE). The upgrade supports a planned expansion and addresses the site’s off-mains drainage constraints.
The zoo is home to more than 100 reptiles, representing 18 crocodile and other reptile species, including the critically endangered Siamese Crocodile from Cambodia and the Komodo dragon. To support the diverse reptile pools, visitor facilities, and an onsite restaurant, a tailored solution was required to handle fluctuating wastewater loads.
Modular wastewater treatment design
WCSEE collaborated with wastewater specialist Soma Services to create a modular HiPAF packaged treatment plant with a 7m3/day capacity. The design accommodates both the backwash flows from crocodile pools—operated similarly to swimming pools—and the variable flows generated by visitor activity.
Graham Hyde, Sales Director at Soma Services, said:
“The site has unique and complex requirements. The backwash flows from the crocodile pools are intermittent, so detailed calculations were essential to determine what needed treating and how best to spread the load. The HiPAF system offered the flexibility and performance needed for such a specialist application.”
Photorealistic illustration showing the chamber layout of a WCSEE HiPAF system.
Environmental compliance and installation
Before installation, a discharge permit was secured from the Environment Agency. Based on technical input from Soma Services, the HiPAF was designed to meet a consent of 20mg/l BOD, 10mg/l ammoniacal nitrogen and 30mg/l suspended solids. A balance tank was installed upstream to regulate flow and manage fluctuations.
The zoo team and Soma Services worked with Christ Church, University of Oxford, and property agency Savills to repurpose a corner of a nearby field for the installation, completed in June 2025. A cut-and-fill method was used to create a level platform while minimising landscape impact.
Three-stage biological treatment process
The HiPAF operates using a three-stage treatment process:
- Primary settlement: Solids settle to prepare wastewater for biological treatment.
- Biological treatment: Lightweight media within the aerated biozone support beneficial bacteria, enabling efficient breakdown of organic pollutants. Segmented chambers prevent short-circuiting and support variable loading.
- Final settlement: An airlift system returns settled humus sludge to the primary chamber for co-settlement and later desludging. The final effluent is discharged via gravity.
The zoo expects to expand further in the coming years, which may require an additional HiPAF unit and continued collaboration between WCSEE and Soma Services.
Steve Holt, Technical Sales Manager at WCSEE, said:
“This has been a unique and rewarding project, demonstrating how adaptable the HiPAF technology can be. The system has been tailored to meet the zoo’s operational needs while ensuring high environmental standards for the long term.”
