Small Sewage Treatment Plants CE Marking and Regulations

Small Sewage Treatment Plants CE Marking and Regulations

Introduction • Small sewage treatments plants are characterised as plants serving 50 Population Equivalents (PE) or less • There has been a large number of changes in the regulation and standards that these systems are now expected to comply with.

History – British Standards often quoted with regards to Small Plants are: • BS 6297: 1983 Design of installation of small sewage treatment works and cesspools – REPLACED WITH BS 6297: 2007 Cope of practice for the design installation of drainage fields for use in wastewater treatment • BS 7781: 1994 Procedure for type testing of small biological domestic wastewater treatment plants – NOW WITHDRAWN

Current ‘UK’ Standard – BS EN 12566 “Small wastewater treatment systems up to 50 PT” contains the following British Standards: • BS EN 12566 -1: 2000 Prefabricated septic tanks • BS EN 12566 -3: 2005 Packaged and/or site assembled domestic wastewater treatment plants • BS EN 12566 -4: 2007 Septic tanks assembled in situ from prefabricated kits

Current ‘UK’ Standard – BS EN 12566 Code of Practice: • TR 12566 -2 Code of Practice for in-situ constructed soil infiltration systems and Standards in preparation: • EN 12566 -5 Pre-treated Effluent Filtration systems • EN 12566 -6 Prefabricated treatment units used for septic tank effluent • EN 12566 -7 Prefabricated tertiary treatment units

BS EN 12566 -3: 2005 – Confusion over Status The EN standard includes for a period of “co-existence” of national standards, however there are no existing/conflicting standards in the UK. Therefore, BS EN 12566 -3 is the ONLY standard that all small treatment plants up to 50 PE MUST comply to.

Key Points of BS EN 12566 -3: 2005 specifies: • Requirements (e. g. design, structural loads) • Test methods • Evaluation of conformity and marking of plants • Installation, operation and maintenance instructions

Requirement of Small Plants • Robust, watertight and corrosion resistant • Equipped with alarm function • Inlet/outlet pipe: 100 mm ID ≤ 4 m 3/d 150 mm ID > 4 m 3/d • Sized in accordance with national regulations (EA and BW Co. P, Flow and Loads)

Test Methods for Small Plants • Watertightness Test (different test methods) • Treatment Efficiency Test (38 -week) incl: o Normal, under and over loading periods o Power breakdown o Low occupation stress (holiday simulation) • Structural Test (different methods, incl. physical and calculations)

Compliance and Marking of Plants • Compliance of plants is tested and certified by independent test facilities in Europe (none in the UK) • Manufacturers shall affix CE-certificate stating: o Name and construction material of plant o Watertightness and structural test results o removal efficiencies for BOD, SS and Ammonia o Energy consumption

UK Foreword of BS EN 12566 -3 • UK foreword was amended in May 2007 • Plants shall demonstrate a minimum effluent quality of 20/30/20 (BOD/SS/Ammonia), e. g. achieve removal efficiencies of 1. BOD > 93% (based on 300 mg/l influent conc. ) 2. SS > 88% (based on 250 mg/l influent conc. ) 3. Ammonia > 50% (based on 40 mg/l influent conc. )

Marsh Sewage Treatment Plants • Have been tested and certified to BSEN 12566 -3 • They have passed with a BOD level below 15 mg/litre • Test certificates are available