Capri, situated in the Gulf of Naples, is one of the most famous islands in the world, there is of course a large touristic interest and each year the impact of dozens thousands tourists on the water main is impressive. Therefore, the town council decided to build a water purifier that could treat all waste waters with advanced criteria also during periods of intense touristic rush. Some important problems immediately appeared : the few available space to work and to stock materials and the fact that it wasn’t possible, for obvious environmental reasons, to build a very high structure. The access to the construction site was very narrow and circuitous. The company responsible for the works decided to build a temporary access road to enable building machines to reach the construction site and to let building materials arrive. Even with this solution, it wasn’t possible to use big building equipment, so they chose small, agile and polyvalent machines : mini-loaders, telescopic handlers and for the purifier concrete structures, a B100 screw pump manufactured by Bunker from Casandrino in the region of Naples.

The pump has been used for all concrete needs of the construction site included the piles used to stabilize the excavation front : there were 400 m2 of piles and two rows of 15 metres of anchor ties made before earth moving executed by a 10 tons excavator with crushing hammer. After excavating, the company started to pump concrete into the formworks of the purifier, designed by “Degremond” from Milan which is the proprietor of the patent. It has extremely complex shapes and dense reinforcements. The structure design is really innovative (it’s the largest water purifier of its kind in Europe) and includes the realization of several “Biofor” 5,40 meters high filtering tanks put 5 m above ground level. Purification muds are stored in these tanks, once they are dry, they are powdered and brought to the dump on firm earth.

The muds enter Biofor tanks after being treated in other tanks with particular shapes (3,50 x 3,50 x 4,95 metres high with steel plates as dividing parts) made of reinforced concrete with additives where they are selected and treated once again. After that, it’s pushed by pumps in the 4 stocking tanks. Another cycle is previewed for non-totally depurated water, all depuration water is stocked and used again and again for next cycles. The purifier’s cover has been made with HEA 300 steel beams on which were put formworks filled with light concrete. Concrete has been prepared to guarantee an extremely high chemical resistance and keep its waterproof qualities in the long-term.

Mr. Dell’Aversano, construction supervisor, underlines the difficulty of concrete pumping and tells us : “Until now, we pumped more than 500 m3 concrete with Bunker’s screw pump without any problem also for special concretes like the Leca light floor screed, we never had pumping problems. With the B100, you can manage very easily fluid or viscous concrete and concrete with additives. We used the pump for the piles, the outer structure and tanks.” We chose the B100 for its versatility : it’s a polyvalent concrete screw pump for grain sizes up to 25 mm, for special and traditional mortars, fibre-reinforced mortars, self-levelling floor screeds, light concrete. It’s adapted to spray plasters and concrete up to 8 mm, inject cement or special mixes into walls, micropiles and anchoring ties. The B100 pumps materials until 45 meters horizontally and can reach 15 metres high. The machine is controlled by an hydraulic power-pack with silenced 18,5 kW Diesel engine (also available in electric version) with an hydraulic output of 60 l/min. Such features make possible reaching a regulable theoretical output of 250 l/min and a theoretical working pressure of 12 bars. All versions are equipped with hopper and feeding screw. The pump can be powered by its power-pack or whatever building machine with appropriate P.T.O : excavators, loaders, drilling rigs.