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Over the last number of months there has been a huge amount of confusion in relation to which Wastewater Treatment Systems are suitable for use in IRL and which are not.

Hopefully this article will provide a plain English explanation in relation to issues that have arisen over EN 12566-3 and I hope it will help put an end to any confusion.

The most obvious place to start is by answering 3 of the most obvious questions that keep popping up, What is EN 12566? Where did it come from? and what does the term "National Annexe" actually mean?

I have also addressed the current status of the IAB certification and while I have been researching this article I have come across one major issue with the EN 12566-3 process that I feel is worth mentioning and will require further  clarification from the DECLG and EPA.

1. Where did EN 12566-3 originate?

The Constructions Products Directive (CPD) was made by our good friends in the European Council in Dec 1988 with the aim of removing technical barriers to trade in construction products between Member States in the European Union. Over the years the directive has gone through a few changes but what it all boils down to is ensuring the free movement of all construction products within the European Union by harmonizing national laws with respect to the essential requirements applicable to these products in terms of health and safety. An additional objective of the directive was to "standardize the manufacturing of construction products and guarantee the unlimited use of these products within the EU.

The CPD provided the following four main elements:

(i) A system of harmonized technical specifications.
(ii) An agreed system of confirming the conformity for each product family.
(iii) A framework of notified bodies.
(iv) The CE marking of products.

2. What is EN12566?

In 2005, a new European Performance Standard was introduced. EN 12566 requires manufacturers to submit their product to a strict uniform testing regime that will accurately measure and compare the performance of treatment plants up to 50 population. EN12566-1 applies to Prefabricated Septic Tanks while EN 12566-3 applies to Packaged and/or Site Assembled Domestic Wastewater Treatment Plants.

Until recently there were no guidelines in place to define the performance of a sewage treatment system. Manufacturers could make claims about their process or system but there was no consistent approach, leaving us all easily confused by the proliferation of information available.

Basically the tests identify how much pollution the plant removes from the sewage, what level of maintenance is required, what power is absorbed and therefore give the user a true basis for comparison.

EN 12566 requires manufacturers to clearly state the performance results of the plant in the form of a performance chart - this allows easy comparison between the various models available on the market.

The EN 12566-3 tests are done in accordance with the standard or in lay man terms the EN 12566-3 systems are tested in accordance with a set of rules and the results are declared.

It is important to remember that this does not mean that the product has met any specific performance criteria. I have often heard manufacturers say "We are EN 12566-3 Certified." That is akin to a learner driver caught driving an Articulated Truck telling a Guard they have a licence. The fact that the licence is for a Honda 50 is apparently immaterial.

EN 12566-3 standard for packaged systems states “The ratios obtained do not automatically mean that the regulatory requirements on effluent qualities in a given country are met. A calculation should be made to indicate the final effluent qualities which should be compared to the requirements valid in the place of use.” This is where the Irish National Annex comes into play.

3. What is the National Annex?

National Annexes are being introduced in order to set out the performance standard acceptable in Ireland. The Department of the Environment Community and Local Government (DECLG) in conjunction with NSAI and the EPA, has developed the National Annexes for Parts 3 of EN 12566. These set out the performance that must be achieved by a particular wastewater unit in order to be acceptable for use in Ireland.

So in order for a wastewater treatment unit to be acceptable in Ireland it must comply with the EN 12566-3 standard and also comply with the IRL National Annex.

Two of the main point of contention and confusion over the last few years directly relate to (i) the effluent quality required on the outlet of a WWTU and (ii) the strength of influent that a WWTU was tested to.

To comply with the IRL National Annex and be fit for use in Ireland the effluent on the outlet needs to reach as a min requirement 20mg/l BOD, 30mg/l SS and 20mg/l NH4-N.

The wastewater treatment unit recommended influent test range should be 300–500 mg/l BOD5. (EPA CoP pg.9). This is where all the confusion over the last few months and years has originated. Why I hear you saying? Well, Up until approx end 2008 one of the main test centres in Germany (PIA) were testing the wastewater treatment units based on an influent range of 150-350 mg/l. The manufacturers were achieving the correct effluent quality on the outlet BUT unfortunately the strength of influent was not always at the correct strength to comply with the EPA CoP requirements.

Out of curiosity I asked the EPA where the figure of 300–500 mg/l originated and this was the response “the range of 300 – 500mg/l BOD relates to the research carried out by Trinity College Dublin and reported in the STRIVE projects 2000-MS-15-M1 and 2005-W-MS-15 (please check Bedtime reading section under INFORMATION>DOWNLOADS section of this site to access the two reports).”

One of my only saving graces is I have plenty of contacts with more letters behind their names than in front of their names so I asked one Chemical Process Engineer who has spent the last 30 years of his life playing with sewage for his interpretation on the issue of 300 – 500mg/l BOD and this is what he said:

"The relationship between water used in a household and the strength of the sewage is what the EPA criterion of 300-500mg/l BOD comes from. Historically the daily flow per head was 180L (200L in UK) as that is what the water companies used, and as they supplied the data that was that. We now know (for the last 20 year) that actually people use a lot less water and the difference was made up of the water/sewage companies bypassing the consumer and leaking up to 30% of the water supplied back to the environment, some passing through the sewage works! So the water use is now closer to 150 litres a day so the concentration of the sewage increases. At 200 litres a day it is 300mg/l, at 150 litres a day it is 400mg/l. If we get down to 120 litres a day, the concentration will be 500mg/l.

The removal percentage achieved in the 12566 testing isn’t strictly extrapolated to different strength incoming sewage.

The final effluent standard of 20:30:20 is concentration based so makes no allowance for the reducing water use in the household. This means the treatment plant has to work harder, and there is actually less pollutant in the treated effluent, so the impact on the environment is less.

Most treatment plants rely on a gravity settlement process, so achieving an average of 10 to 15mg/l SS in the final effluent. The BOD in the effluent is generally accepted to be approximately 2/3rds of the SS plus a small fraction of remaining soluble BOD, resulting in a BOD discharge of 7 to 10mg/l.

However, the discharge consent imposed by the EPA is a 95%ile figure, which works out to be double the average. Thus the treatment plant can comply with a 20:30 BOD/SS discharge.

The reduction in flow to the plant when the households use less water increases the concentration and this means the removal efficiencies have to be higher.

300mg/l to 20mg/l BOD is 93.33% removal

500mg/l to 20mg/l is 96% removal.

To achieve 96% removal at 300mg/l would require the plant to achieve 12mg/l or about 20g/l solids, but on an average basis this becomes 10mg/l SS and 6mg/l BOD!!

In reality the treatment plant will achieve the required effluent concentration, the problem is the “powers that be” don’t really understand the process and so think they can just “pro rata” the performance to different concentrations. A process that we know to be totally unfounded and as misleading as the published nitrification and total nitrogen standard.

Talking of which, the total N standard of 15mg/l is much harder to achieve as the incoming sewage strength increases. That’s assuming that somebody has actually worked out what total nitrogen is!

At the end of the day, the pollution released to the environment from single dwellings or small developments should be based the mass (grams) released, totally ignoring the flow, especially if discharge is to a soak away. Problem is it would cost more to work out what the mass is, as nobody knows the flow!!!

But, everything in the EPA requires the flow to be known!"

At this point I would like to state that I fully sympathise with both large and small manufacturers up and down the country who have tested their systems pre 2008 and have now found themselves in the position that their WWTU are not fit for purpose in Irl. There are approx 30 companies providing local and national employment and to suddenly find themselves in this position is hard to stomach. I have talked to a number of manufacturers who simply can not now afford to resend their WWTU to a certifying body as the fees can reach 60K. As we all know the market has shrunk considerable and the return on investment is simply not there. Other manufacturers (all non concrete) have headed for the export market with France being the country of flavour.

4. EN 12566-3 accredited Test Centres

Another point that needs to be clarified for local authorities and the site assessor community is the issue in relation to where WWTU have been certified. There are no less than 38 accredited test centres in Europe. The majority of systems in Ireland have been tested in PIA, Aachen, Germany. I have often wondered why most Irl manufacturers ended up going here to have their systems tested and jokingly one manufacturer commented “Monkey See Monkey Do”! However it is worth noting that PIA is one of the biggest test centres/institutes in Europe with a huge amount of experience and expertise. I have personally had the pleasure of dealing with some of their staff and they are extremely helpful and professional. Other manufacturers like Molloy Precast had their system tested in MFPA Weimar and Biotank by Gillespie Concrete was tested in Rostock, Germany.

5. Changes to the EN 12566-3 format

On 26/10/11 Eamonn Smyth, Technical Advisor within the Building Standard Section of the DoECLG made a presentation at a wastewater conference held in Portlaoise. The Title of the presentation was "EN Certification and National Annexes."

During the presentation he outlined changes that would be needed to be made to original EN 12566-3 certs in order for them to clearly display information to determine compliance with the National Annex. In other words all required and relevant information is to be listed on the one cert.

Personally I welcome such a proposal and even though it was a long time coming at least we in the wastewater community can see at a quick glance if the wastewater system is EN 12566-3 certified AND complies with the Irl National Annex.

Unfortunately some manufacturers found themselves on the back foot with obtaining revised certs from the various test centres. It appears that the DoECLG might have assumed that PIA was the only test centre that Irl manufacturers used so when other manufacturers contacted their respective test centres there was and still is a delay in getting the original certs modified.

As of yet there is no national authority website that is hosting the systems that are suitable for use in Irl. However the EPA has informed me” We (EPA) have agreed with the DECLG that the EPA will host a list of wastewater systems that have been tested in accordance with EN 12566 and satisfy the requirements of the National Annex (and therefore CoP). The requirement to meet the EN standard has been introduced in the new Building Regulations and does not apply retrospectively to old systems.

The web page will include an introduction that outline what the list is, include a disclaimer and comment that it is not an endorsement of products. It would also refer to installation requirements as outlined in CoP.

The list has been requested by the DECLG to enable LA and others to make informed decisions in relation to products on the market. The DECLG proposes to establish a committee on which the EPA will participate, to review and approve or otherwise the systems for inclusion on the list. Any queries in relation to the placement of products on the list are to be directed back to the DECLG.

6. Building Regulation H & TGD H

In general, this document applies to works, or buildings in which a material change of use takes place, where the works or the change of use commences or takes place, as the case may be, on or after 1 June 2011. There has been a one year transitional arrangement but the document comes into effect on 1 June 2012 i.e. 06 weeks time.

This doc calls up relevant sections of the EPA Code of Practice 2009 and it requires wastewater products to comply with the harmonised EN 12566 standards and their National Annexes.

In relation to Secondary Wastewater Treatment Systems the CoP states that products should be certified (certification may include a European Technical Approval, an Agrément Certificate or equivalent), be fit for the purpose for which they are intended, the conditions in which they are used and meet the performance requirements of this CoP.

Up until recently I thought that the IAB certs were no longer valid from May 31st 2012. I was wrong. The NSAI clarified this for me stating “Part D of the building regulations states that an Irish Agrément certificate is a method of showing compliance with regulations. Therefore all current certificates are valid. However, no product will be certified by us unless it has been tested to ISEN12566-3 and shown to meet the requirements of the new TGD Part H and the national annex to the standard.”

The most obvious question that arises is why would a manufacturer pay for IAB certification/recertification if they already have spent 60K + attaining EN12566-3 certification?

7. EN 12566-3 Issues that need further clarification.

While I was researching this article I noticed one issue in relation to the certification process of a wastewater treatment system. The issue is centred on the sizing of various units i.e. 6pe, 10 pe etc.

Before I raise the issue I will try and very briefly explain the testing procedure.

Part of the EN 12566-3 certification process requires a manufacturer to test the smallest tank in the range and record the standard of effluent quality. i.e. 20mg/l BOD, 30mg/l SS, 20mg/l NH4-N.

In order to certify a range of products up to 50PE i.e. 6PE 9PE 15PE etc the manufacturer must submit all his calculations for all the intervening sizes, calculations, are to a very specific DIN standard and these calculations are then approved by the testing house, PIA, MFPA etc.

More often than not the testing house would expect at least a specialist degree qualification in WWT before they would accept the calculations submitted. Once the test house has verified the calculations then the manufacturer will be issued with a test report for that size of unit.


So if we examine the following cert as an example and lets assume that this manufacturer has only tested ONE tank as they simply don’t have another tanks in their range.



A few small calculations:

In this instance the wwtu is capable of dealing with 0.22kg/d organic loading which equates to 3.6PE based on the 0.06kg per person per day (EPA) and the wwtu is capable of dealing with 0.72m³/d hydraulic loading based which based on 0.15 m³/d per person (EPA) equates to 4.8PE.

Therefore this unit is sized on the smaller of the two figures and is actually a 3.6 or 4PE system. If this manufacturer has no other tanks in their range that has been certified by the testing house this manufacturer can only sell the system that was tested for 4PE. i.e. one double bedroom house.

If in the future a manufacturer wanted to increase his range of tanks and sell a system as an 8PE, he would have to submit the larger tank and the new calculations to the testing house for certification.

So if a manufacturer has only tested One tank and that tank has obtained EN 12566-3 certification and is compliant with the Irish national Annex it is NOT possible for that manufacturer to scale up the range of tanks to 50 persons. In my opinion it would also be incorrect for a manufacturer to sell the tank that obtained certification on the pretence that it can service a population equivalent larger than it has obtained certification for? i.e. 4PE system should not be sold as an 8PE system without clarification on the summary single page test cert.

In order to clarify this the DoECLG should simply request that the testing houses clarify this on the EN 12566-3 cert by inserting the range of tank sizes that individual manufacturers has to offer.

8. Conclusion

So if you are a site assessor, homeowner or member of a local authority it might be no harm if you ask the following few questions before you purchase your wwtu.

• Is the unit EN 12566-3 certified?

• Does the unit comply with the Irl National Annex?

• Does the SIZE ( PE6 PE8 etc) of the unit that I am specifying or purchasing have the correct certification?