Contract signed for microfiltration pilot design at Elva WWTP
AS Emajõe Veevärk (EVV) has signed a contract following a public procurement procedure for the designing of pilot unit at Elva wastewater treatment plant (WWTP). The pilot will focus on removing microplastics (MPs) from sludge reject water, an internal stream in the treatment process that can contain concentrated amounts of microplastic particles. The delivery and installation of the microfilter unit will be carried out under a separate procurement.
Targeting microplastics within the treatment process
“The pilot project at the Elva WWTP is important because studies have shown that microplastics are accumulated into sewage sludge and significant amount is recirulated back into wastewater treatment process steps via reject water line. Using the pilot unit, we aim to prevent MPs recirculation and lower the release of microplastics to the environment – both in the treated effluent and through the land application of sewage sludge as fertilizer” – Rainer Spuul, Chief Technology Officer, AS Emajõe Veevärk.
During wastewater treatment, a large share of microplastics is transferred into sludge. When sludge is thickened and dewatered, part of these particles return to the treatment process via reject water. Without additional treatment, microplastics can continue circulating within the plant and eventually be discharged into receiving waters or remain in sludge destined for further use.
At Elva WWTP, the new microfiltration unit will be designed and installed on the reject water line. The system is designed to:
- retain microplastic particles using a fine-pore stainless steel membrane
- concentrate them into a separate stream
- reduce their recirculation within the treatment process
The retained material will be handled separately to prevent re-entry into the water cycle. The contractor, Mativesi OÜ, will design the microfiltration system for the reject water stream at Elva WWTP.
“It is an interesting project to determine what pollutants are present in the stream from the centrifuge, how these pollutants can be captured, and whether the designed solution will help to improve the overall water quality” – Matthias Eichhorst, CEO, Mativesi OÜ.
Supporting harmonised monitoring and research
The Elva pilot is one of two technical demonstrations carried out within the cooperation framework. In parallel, piloting experiments are made with the incoming wastewater after existing screening treatment by using commercial cross-rotational filter at Mikkeli WWTP in Finland.
Scientific partners, including the National Institute of Chemical Physics and Biophysics (KBFI), are responsible for validating sampling and analytical methods and for evaluating the performance of the pilot installations.
The activities support the broader objective of decreasing microplastics loads entering the Baltic Sea from urban wastewater sources and contribute to preparedness for the revised EU Urban Wastewater Treatment Directive, which will introduce stricter monitoring and advanced treatment requirements for micropollutants, including microplastics.
Next steps
Following the contract signing, the project will move into the next phase: the detailed design stage. The final design is scheduled to be completed by the end of May. A separate procurement process will then be launched to select the supplier and construction partner to implement the previously designed solution.
