1. BS EN 12255-3:2000 Wastewater treatment plants - Part 3: Preliminary treatment

2. BS EN 12255-4:2002 Wastewater treatment plants - Part 4: Primary settlement

3. BS EN 12255-5:1999 Wastewater treatment plants - Part 5: Lagooning processes

4. BS EN 12255-6:2002 Wastewater treatment plants - Part 6: Activated sludge process

5. BS EN 12255-7:2002 Wastewater treatment plants - Part 7: Biological fixed-film reactors

6. BS EN 12255-8:2001 Wastewater treatment plants - Part 8: Sludge treatment and storage

7. BS EN 12255-9:2002 Wastewater treatment plants - Part 9: Odour control and ventilation

8. BS EN 12256:1998 Plastics piping systems - Thermoplastics fittings - Test method for mechanical strength or flexibility of fabricated fittings

9. BS EN 12257:2002 Transportable gas cylinders - Seamless, hoop-wrapped composite cylinders

10. BS EN 12258-1:2012 Aluminium and aluminium alloys - Terms and definitions - Part 1: General terms