ProRheno AG has awarded to WABAG Water Technology Ltd. in Winterthur the expansion of the Basel wastewater treatment plant by means of an additional treatment stage for micropollutant removal. This contract was awarded in May 2016. The operator of one of the country’s largest WWTP’s has thus reacted quickly to Switzerland’s new water conservation legislation, which defines the elimination rates for organic trace substances. WABAG has established itself as an expert for these special requirements and will apply to the Basel plant a combined process using ozonation followed by PAC dosing and tertiary deep bed filtration (BIOZONE® – PACOPUR®). The start-up of this EUR 7.5 million contract is scheduled in 2021.
Micropollutants in wastewater – small cause, major effect.
A continual improvement in analysis methods means that the presence of micropollutants, i.e. substances that occur in water in extremely low concentrations, can be detected to an ever increasing rate. Growing industrialisation, population densities and use of medication has resulted in potentially damaging active hormonal substances, pharmaceutical ingredients, chemicals and pesticides penetrating our eco-systems, largely via wastewater disposal systems.
Consequently, with effect from 1 January 2016, Switzerland, who has always been a water technology trailblazer, became the first nation to pass legislation that stipulates elimination rates for trace substances. The aim is to protect both aquatic eco-systems and drinking water resources.
For its part, over the past decade WABAG has also carried out pioneering activities in this area and has been working on the development and testing of suitable technologies.. Numerous research projects have been implemented e.g. in co-operation with the Swiss Federal Environmental Protection Office, the Swiss aquatic research institute Eawag and the Vienna University of Technology in Austria. As a result, WABAG is currently one of the few companies able to offer the complete range of relevant technologies including ozonisation and the activated carbon adsorption process, as well as their combination. In 2013, the first BIOZONE® customer plant went into operation in St. Pourçain-sur-Sioule, France and since then WABAG has received contracts in in Reinach, Thunersee, Altenrhein and Porrentruy in Switzerland for ozonisation and/or adsorption, or deep bed filtration.
A complete WABAG system in Basel
In Basel, the BIOZONE®-PACOPUR® process combination will be implemented as a complete plant for the removal of problematic trace substances. Put simply, the technological principle can be explained as follows. Micropollutants are partially “cracked” using ozone and combine together with those micropollutants not attacked by adhering to the surface of the activated carbon (adsorption). The “loaded” activated carbon is then filtered out of the wastewater, by means of a deep bed filtration, while the oxidation by-products from ozonisation are degraded biologically. The plant has a maximum total capacity of 3,000 l/s (mean daily volume: 93,000 m3/d, max. 260,000 m3/d) and the ozonisation unit a maximum performance of 52 kg O3/h.
WABAG is responsible for the design, engineering, equipment supply, installation and commissioning. Completion of the services is subject to the condition that all necessary approvals for the overall project are received.
The Basel contract again underlines WABAG’s technological leadership and will provide an important reference in this specific field. This is significant in view of current needs and their recognition, as indicated by the fact that other European countries are discussing the topic of micropollutants in wastewater and the search for legal and technical solutions are already underway.