New Era For Wastewater Treatment Industry

Alison Anderson explains how a new European standard for small wastewater treatment plants will bring much-needed conformity to the industry

Comparing the quality and effectiveness of small wastewater treatment systems will soon be much easier, thanks to a new European standard, which comes into force in 2008.

The standard - EN12566 Part 3: Small Wastewater Treatment Systems - covers up to 50 population equivalents Package and/or Site Assembled Domestic Wastewater Treatment plants.

It will bring much-needed clarity to an industry where purchasers are faced with an array of products that achieve results in different ways and use a wide variety of biological processes.

The standard will define the minimum requirements for small wastewater treatment systems. It will also challenge manufacturers' performance claims by asking them to submit their products for rigorous tests, which are being conducted over a 38-week period by independent researchers in Germany, Belgium and Finland.

The key results of these tests will be clearly stated on the CE (Communauté Européenne) marking label, which allows approved manufacturers to trade across the European Union.

The minimum requirements include the fact that the products must be structurally durable, watertight and corrosion resistant. They should also be fitted with an alarm to indicate an operational problem, such as electrical, mechanical, or hydraulic failure.

Plants may be constructed from concrete, steel, PVC-U, Polythene (PE), Polypropylene (PP) and Glass Reinforced Polyester (GRP), and the standard lays down the individual requirements for each type of material.

The standard also states that the hydraulic design of the plant, internal pipework and connections must ensure no back-flows, blockage or surcharging occur during normal operation.

Depending on the end use, factors given by national regulations, or codes of practice valid in the country of use, will determine the loads for which the plants are designed.

During the performance tests, all plants must be assessed against the following core parameters - total chemical oxygen demand (COD), biochemical oxygen demand (BOD), suspended solids (SS), power consumption, daily hydraulic flow and temperature.

Treatment efficiency ratios for BOD and SS are mandatory. However, other treatment efficiencies may also be declared to provide added reassurance for purchasers. These may include levels of ammonia, phosphate, sludge production,etc. Once determined, these treatment efficiency ratio percentages can be used to predict a numerical effluent quality. It is expected that the usual effluent quality required by the regulators will be in the order of 20mg/L BOD, 30 mg/L SS and 20 mg/l NH4.

Performance tests are mostly conducted under "normal" (i.e. nominal flow) usage conditions, which include defined intermittent flows during a 24-hour period. The performance of the product in the event of a problem, such as power failure, underloading, or overloading, is also assessed.

Following the successful completion of the tests, the product's key statistics, including its daily hydraulic load, treatment efficiency and electrical consumption, will be clearly recorded in documentation. Other tested performance indicators, such as the nitrogen parameters and total phosphorus, may also be included. In addition, the manufacturer's name and address will also be clearly identified, and a label indicating the product's test status may be supplied.

Other significant information highlighted in the test report includes how much maintenance was required during the testing, how easy it was to access the components and how much power was required to operate the unit.

The standard has been prepared by the Technical Committee CEN/TC 165 "Wastewater Engineering" under a mandate provided by the European Commission and the European Free Trade Association, and supports key EU directives.

Klargester completed the testing in June 2005, with its BioDisc sewage treatment plant passing with flying colours. The company believes that it was the first manufacturer in the UK to complete the performance testing.

Manufacturers now have a transition period in which to carry out the performance and other specified tests enabling them to ensure that their products comply with the standard's requirements. The normal 12-month transition period has been extended to allow for the lengthy performance test and expires in July 2008.

Manufacturers who do not test their products to the standard will not be able to export them for use in other European Union countries, unless they can prove to regulators by some other means that their goods will perform and are of a sufficiently high quality. It is understood that the UK environmental regulators will recommend the installation of CE marked products.

To conclude, wastewater treatment plants are effective, yet complex solutions for off-mains drainage properties. With so many different makes and models on the market, the new standard will bring much-needed clarity to the industry, making it easier for customers to ensure they choose a safe and effective solution.

This article was written by Alison Anderson, who is process manager for leading sewage solutions provider Klargester and a member of the team which developed the new European standard for small wastewater treatment systems

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