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 Standards often quoted with regards to Small Plants are: BS6297:1983 Design of installation of small sewage treatment works and cesspools – REPLACED WITH BS6297:2007 Cope of practice for the design installation of drainage fields for use in wastewater treatment BS7781:1994 Procedure for type testing of small biological domestic wastewater treatment plants – NOW WITHDRAWN

Current ‘UK’ Standard – BS EN 12566 EN 12566 “Small wastewater treatment systems up to 50PT” 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 50PE MUST comply to.

Key Points of BS EN 12566-3 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: 100mm ID ≤ 4m3/d 150mm ID > 4m3/d Sized in accordance with national regulations (EA and BW CoP, Flow and Loads)

Test Methods for Small Plants Watertightness Test (different test methods) Treatment Efficiency Test (38-week) incl: Normal, under and over loading periods Power breakdown 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: Name and construction material of plant Watertightness and structural test results removal efficiencies for BOD, SS and Ammonia 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 BOD > 93% (based on 300mg/l influent conc.) SS > 88% (based on 250mg/l influent conc.) Ammonia > 50% (based on 40mg/l influent conc.)

Marsh Sewage Treatment Plants Have been tested and certified to BSEN12566-3 They have passed with a BOD level below 15mg/litre Test certificates are available