Strass sewage treatment plant - well equipped for the future

As part of a planned expansion project, the municipal sewage treatment plant in Strass, Austria, has been undergoing extensive rehabilitation since 2019. With the operator insisting on high quality and convincing sustainability in the solutions applied, MC-Bauchemie's special MC-RIM PROTECT coatings have been selected for the sewage-handling facilities.

The village of Strass lies in the Zillertal valley of Austria’s Tyrol region, halfway between Kufstein and Innsbruck. Boasting no more than around 850 inhabitants, it is the location of Tyrol's second largest municipal sewage treatment plant. It currently treats the wastewater of 31 municipalities with 52,000 inhabitants and 8.5 million overnight guests per year, handling an average daily volume of over 28,000 m³.

 

Expansion and rehabilitation

The facility operator, Abwasserverband Achental - Inntal - Zillertal (AIZ), decided in 2018 to expand the capacity of the sewage treatment plant commissioned in 1989 from 167,000 to 200,000 PE. PE stands for “population equivalent” and indicates the number of inhabitants living in the catchment area of a wastewater treatment installation. The expansion project was to be accompanied by extensive rehabilitation and optimisation of the treatment plant over several years. In June 2019, work began on the first of four low-load biological basins with around 1,500 m² of wall area and 540 m² of floor area requiring rehabilitation. The basin was completely enclosed for the duration of the repair work in order to exclude as far as possible weather influences and work interruptions due to precipitation. At the same time, a short-term challenge also arose: Substrate preparation with high-pressure water jetting revealed that the surface tensile strengths of the existing concrete were below par.  On the advice of MC sales representative Hubert Schiffbänker, client AIZ and the coating contractor carried out a series of cost-efficient remedial measures aligned to consolidation and durable protection of the concrete, with no negative impact on the project schedule going forward.

Sustainable surface protection

For example, the wall surfaces were coated with MC-RIM PROTECT, a highly sulphate-resistant, fibre-reinforced surface protection coating formulated for use in the sewerage sector, which was applied in a layer thickness of 7 mm above the exposed aggregate tips. The floor surfaces were coated with MC-RIM PROTECT-H, especially developed for application on horizontal substrates in the sewerage sector, with a layer thickness of 10 mm above the exposed aggregate tips. Both products of the MC-RIM PROTECT system are characterised by their chemical resistance in the range pH 14 to pH 3.35, very high resistance to chlorides and high mechanical resilience. They are also resistant to extreme temperatures, freeze-thaw cycling and de-icing salts They exhibit total porosity values well below those required by German code DVGW W 300-5, thus confirming their extremely dense structure offering maximum protection.

 

The client was fully satisfied with the systems used, the speed  and high quality with which the work was performed, and also the support provided along the way, all of which enabled the rehabilitated basin to be recommissioned on schedule in September 2019. Leveraging the excellent experience gained, work on the next low-load biological basin with the same rehabilitation system commenced in April 2020.