• Types of Reedbeds

• Types of Septic Tanks

• Types of Package Sewage Treatment Plants

• Case Studies

• Conclusions from Case Studies

• Questions

Contents

Horizontal Flow Reedbed

Liner

1mm LDPE

Gravel media

6-20 mmØ

Stone inlet

150 mmØ

Stone outlet

20-40 mmØ

Depth

600 mm

Horizontal Flow Reedbed

Flow

Lateral;

in real time

Reeds

Phragmites

australis

@ 4 per m2

Plant

April to August

Flood or Cut?

No to both

Horizontal Flow Reedbed

Reduce

BOD

SS

NH3 X

P X

Compact Vertical Flow Reedbed

Liner

1mm LDPE

Gravel media

6-20 mmØ

on base

Sand media

Well drained

Depth

>1000 mm

Compact Vertical Flow Reedbed

Flow

Downwards;

A dosed flow

onto surface

Reeds

Phragmites

australis

@ 4 per m2

Plant

April to August

Cut?

Yes?

Compact Vertical Flow Reedbed

Reduce

BOD

SS

NH3

P

Septic Tanks

Onion shape, cone baffle Cylindrical shape, twin chamber

Rotating Biological Contactors (RBC)

Rotating plastic media discs ‘dip’ the biomass on the discs in and out of the effluent & air alternately

Kee Process (>50 PE)

Klargester (6-50 PE)

Trickle Filters (TF)

Klargester (6-25 PE)

* Titan (6-375 PE)

Effluent splashes over a fixed block of hollow plastic media and the effluent passes over the biomass as it drops down through the media

Submerged Aerated Filters (SAF)

Biokube (6-50 PE)

Conder (30+ PE)

Air is blown into the base of the tank circulating & mixing the effluent over fixed plastic media

Mobile Media Bio-Reactors (MMBR)

Balmoral (6-50 PE)

Oaklands (6-50 PE)

Klargester (30+ PE)

Air is blown into the base of the tank circulating & mixing the effluent over mobile plastic media

Activated Sludge (AS)

Conder (6-25 PE)

Viltra (6-12 PE)

WPL (6-25 PE)

Air is blown into the base of the tank circulating & mixing the effluent.

No media.

• Every one of those package sewage treatment plants is sold on the basis of achieving a final effluent discharge quality standard of at least:

20 mg/l BOD 30 mg/l SS 20 mg/l Ammonia

• Almost all manufactures have EU Certification to back them up (EN 12566) for both package sewage treatment plants & septic tanks

• How do reedbeds compare?

• IEMA Constructed Wetlands Conference in Edinburgh University, Dec 2007

Paul Cooper said that we do not have enough data regarding the performance of existing reedbed systems and good quality datasets were probably limited to around 50 in number

• I agreed and set out to sample as many sites as possible during the course of my normal daily work and during scheduled maintenance visits

Data collected from a wide range of systems

How Do They All Compare?

Methods of Analysis

BOD Probable value using a Permanganate method

SS Jackson Turbidity Units (JTU) which are equivalent to SS

NH3 & P PhotometerBOD after 30 minutes

3 stay pink = <15 mg/l

2 stay pink = 15 – 30 mg/l

1 stay pink = 30 – 45 mg/l

0 stay pink = >45 mg/l

Single Dwellings (various)

SitePE(persons)

Type ofPSTP

Sample DateBOD

(mg/l)SS

(mg/l)NH3

(mg/l)

Dumfries 6 (2) TF 10th July 2008 nd 100 8.00

21st Aug 2009 15 – 30 20 2.80

18th March 2011 15 – 30 10 10.70

Paisley 6 (2) TF 17th Feb 2012 nd >150 nd

26th Feb 2013 >45 200 nd

Neilston 6 (2) MMBR 19th May 2011 30 – 45 100 27.40

14th May 2013 30 – 45 100 23.80

Strathblane 6 (4) MMBR 17th Feb 2012 nd >150 nd

26th Feb 2013 >45 40 6.10

Poor emptying by tanker drivers? Influence of diet e.g. FOG?

Hamilton Golf Club, Lanarkshire

Commissioned in April 2011.

Broken down in March 2012.

Sample DateBOD

(mg/l)SS

(mg/l)NH3

(mg/l)

20th Sept 2011 15 – 30 10 2.80

22nd March 2012 nd 200 nd

26th Sept 2012 15 – 30 60 nd

21st March 2013 15 – 30 80 1.70

Site

Clubhouse

Restaurant

Toilets & locker rooms

Design

110 PE

6.96 m3/day

System

120 PE RBC

License

50 BOD : 100 SS

Purclewan Mill, Ayrshire

Sample DateBOD

(mg/l)SS

(mg/l)NH3

(mg/l)

19th Aug 2009 30 - 45 25 23.40

23rd April 2010 30 – 45 15 28.20

5th Nov 2010 0 – 15 10 8.20

17th May 2011 30 – 45 30 39.50

17th Oct 2011 15 – 30 5 12.60

19th April 2012 30 - 45 30 nd

17th Oct 2012 15 - 30 5 9.70

2nd May 2013 30 - 45 5 27.4

Site

6 Dwellings

Design

36 PE (18 persons in 2010)

Reedbed @ 3.45 m2/PE

(actual 6.90 m2/PE)

System

8,000 litre Septic Tank

3,800 litre Septic Tank

124 m2 HF Reedbed

License

30 BOD : 30 SSCommissioned & planted in July 2008.

Purclewan Mill – HF Reedbed

Strathaven Rural Centre, Lanarkshire

Sample DateBOD

(mg/l)SS

(mg/l)NH3

(mg/l)

PSTP RB PSTP RB PSTP RB

3rd Dec 2009 15 – 30 0 – 15 17 5 13.90 5.40

8th Feb 2010 15 – 30 15 – 30 50 20 23.40 9.50

15th April 2010 nd 0 - 15 60 5 44.50 8.30

11th June 2010 nd 15 - 30 150 15 >50 8.10

15th July 2011 nd 15 – 30 175 15 55.00 4.90

14th Oct 2011 nd 15 – 30 90 5 32.60 2.40

3rd May 2012 nd 15 – 30 nd 10 nd nd

31st Oct 2012 30 – 45 15 – 30 100 20 14.00 7.30

1st May 2013 >45 15 – 30 150 5 30.40 0.10

Site

Offices / Country Store /

Vets Practice / Café

Design

47 PE

6.18 m3/day

System

50 PE MMBR

Pump station

60 m2 CVF Reedbed

License

10 BOD : 5 NH3 : (100 SS)

Plant commissioned Sept 2009 / Reeds planted June 2010.

Started regular service visits in July 2011 / Major overhaul Oct 2011.

Flexible air hose was replaced with a rigid plastic pipe in May 2012.

S.R.C. CVF Reedbed Outlet – pH, SS, BOD & NH3

MMBR air hose replacement

Strathaven Rural Centre – MMBR & CVF Reedbed

Conclusions from Case Studies

Septic Tank + HF Reedbed

Not suitable for full secondary biological treatment (20:30:20) at the current design standard of 5 m2/PE

Package Sewage Treatment Plant

Full secondary treatment (20:30:20) can only be achieved by a regular maintenance regime (service & empty) appropriate to loading and even then lifestyles appear to have a big impact on treatment performance

HF & CVF Reedbeds

Best as final polishing, tertiary treatment systems

CVF have a greater potential to reduce contaminants especially ammonia

Package Sewage Treatment Plant + HF Reedbed

Capable of reducing BOD & SS (Ammonia) to low values

Package Sewage Treatment Plant + CVF Reedbed

Capable of reducing BOD, SS & Ammonia to very, very low levels

Questions for the Authorities & Regulators

Is the Design Consultant competent?

Architects & Engineers all too often pay very little attention to sewage treatment and is usually last on their list of priorities

Is the Installer competent?

House Builders & Ground Workers all too often install reedbeds badly

Has the sewage system been installed & commissioned properly?

Has anyone from the Local Authority, EA or SEPA checked on site?

Is the sewage system being serviced and emptied properly & regularly?

All too often end-users think reedbeds do not require maintenance as this is what they were told

Questions for Us

How do we react to EN-12566? (Part 1 septic tanks / Part 3 sewage plants <50 PE)

Reedbeds are not certified systems

Reedbeds don’t work in cold weather

How do we combat the negative marketing by others?

How do we collect more performance data?

MSc & PhD thesis are good but we also require studies that concentrate on applied, methodical, data gathering science

How do we promote our basic design standards?

BRE 41 & 42 are well out of date and need a radical update and promotion to Local Authorities, Architects & Engineers

How do we promote the CWA to a wider audience & increase membership?

We Need to Stop This

and This

Thank you