Small Sewage Treatment Plants

1
Small Sewage Treatment Plants

• CE Marking and Regulations

2
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.

3
History British Standards

• Standards often quoted with regards to Small
  Plants are
• BS62971983 Design of installation of small
  sewage treatment works and cesspools REPLACED
  WITH BS62972007 Cope of practice for the design
  installation of drainage fields for use in
  wastewater treatment
• BS77811994 Procedure for type testing of small
  biological domestic wastewater treatment plants
  NOW WITHDRAWN

4
Current UK Standard BS EN 12566

• EN 12566 Small wastewater treatment systems up
  to 50PT contains the following British
  Standards
• BS EN 12566-12000 Prefabricated septic tanks
• BS EN 12566-32005 Packaged and/or site assembled
  domestic wastewater treatment plants
• BS EN 12566-42007 Septic tanks assembled in situ
  from prefabricated kits

5
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

6
BS EN 12566-32005 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.

7
Key Points of BS EN 12566-3

• BS EN 12566-32005 specifies
• Requirements (e.g. design, structural loads)
• Test methods
• Evaluation of conformity and marking of plants
• Installation, operation and maintenance
  instructions

8
Requirement of Small Plants

• Robust, watertight and corrosion resistant
• Equipped with alarm function
• Inlet/outlet pipe 100mm ID 4m3/d
• 150mm ID gt 4m3/d
• Sized in accordance with national regulations (EA
  and BW CoP, Flow and Loads)

9
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)

10
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

11
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 gt 93 (based on 300mg/l influent conc.)
• SS gt 88 (based on 250mg/l influent conc.)
• Ammonia gt 50 (based on 40mg/l influent conc.)

12
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