The biodigestion sewage treatment plant in Griesheim Industrial Park, Germany was extended in 2001 by adding a nitrate stripping facility. This was the first time that an abrasion and UV-resistant GRP piping system had been used for sludge recirculation. Due to the zero maintenance requirement, these pipes had paid for themselves within a short time. An inspection was carried out in mid-2003 and no signs of defects or damage in service were observed.
When the management of the Griesheim sewage treatment plant decided to upgrade the system in 2001, the plans included a project to install a sludge recirculation pipeline. „The active sludge has to be recirculated from the plant’s biodigesters in order to operate the nitrate stripping unit“ says Plant Manager Frank Birringer. „Owing to the abrasive properties of the sludge and its aggressive ingredients, it was important to find a long-lasting, rugged and maintenance-free material for this application.“
In the light of previous good experience with GRP piping systems for pigment manufacture, the owner of the plant decided to request Fibagroup Europe, located in Aldenhoven, to design and supply the new sludge pumping line.
According to Alexander Bamberger, the Fibagroup Sales Manager responsible for Northern Germany, Hesse and Rhineland-Palatinate, „the main requirements of the Griesheim plant were complete corrosion and abrasion resistance with good weathering and anti-UV characteristics, together with a pressure resistance of 10 bar. In addition, the manufacture of all pipe spools as well as all pre-assembly and installation work on site needed to be completed by a single specialist contractor in the shortest possible time scale.“
Fibagroup provided technical support to the client by preparing full calculations and drawings for the GRP system and ensuring its compliance with all relevant standards. After discussing the complete spectrum of technical and structural system requirements with the client, it was decided that Fiberdur CSVE 10 piping should be used. This is a proven system of filament-wound pipes manufactured with a vinyl ester resin and provided with an additional chemical and abrasion-resistant internal liner.
Fibagroup standard piping systems are manufactured by filament winding with glass fibres and polyester, vinyl ester or epoxy resin systems with diameters from DN 25 to DN 2300 and lengths of 10 m. Pressure ratings from 6 to 16 bar are available. A special curing process ensures high mechanical strength and the quality of the filament-wound structure. The machine-wound structural core of the pipe has a high glass content and a reinforced corrosion and abrasion-resistant inner liner, and is externally finished with a resin-rich UV protective layer.
For the sewage treatment plant project in Griesheim, Fibagroup installed two main pumping circuits with a pipe diameter of 250 mm each and a length of 130 m, including 24 15° elbows. The system was prefabricated in the Fiberdur factory in 12 spools which were assembled on site.
Fibagroup additionally supplied two fabricated 37.5° double-elbow units, each about 12.5 m long, to cross an existing concrete drainage channel without any disruption to the concrete structure. „We were surprised how quick and trouble-free the installation was“ says Birringer. „The order was placed in mid-June 2001 and within 3 months the new circulation system was operational.“
Convincing cost results
Since its installation, the entire system has met and indeed exceeded all expectations regarding both GRP reliability and costs. In spite of the relatively high initial outlay for the system, the zero maintenance requirement has ensured that it is extremely cost-effective to run and the investment has undoubtedly paid off.
In mid-2003 the plant owner arranged an inspection of the system to ensure that the pipes were still in top condition. The examination revealed no signs whatsoever of wear or damage to the piping system. As a result of the successful cooperation with Fiba-group on this project and earlier schemes, it is envisaged that GRP will also be specified for future work.