Crystal clear technologies for water treatment in nonwovens production: idrosistem specializes in recycling water in spunlace manufacturing.

Idrosistem energy srl has specialized in the treatment of water from spunlaced plants for many years. During this time, the company has analyzed the main problems of spunlace production and developed technologies to solve them.

The Problems

* Clogged Jet Strips and Streaks in Fabric: When water is not totally free of all suspended solids, it creates clogged jet strips, which lead to streaks in the spunlace fabric and frequent replacement of filters bags in the final filter.

* Bacteria Growth: Suspended solids in water can also enhance bacteria growth. Experience in similar sectors has shown that the removal of suspended solids from water remarkably reduces bacterial growth inside pipes. It has been proved that, when no suitable treatment takes place, solid particles of the processed material are deposited in the pipes located upstream from the jet. These deposits become an ideal place for the multiplication of bacterial mass, making the plant useless for the manufacture of antibacterial products.

* Incrustations: The incrustations, in addition to making the adhesion of solid particles easier, can damage the stainless steel "strips" in the jet. In fact, the presence of even the smallest particles of incrustations above the strips may cause them to be scratched when cleaned.

* Loss of Sand: In some cases plants suffer from sand filtration loss with the consequence of excessive discharge of water in the filter's back washing.

The Solutions

Idrosistem Energy has developed a treatment system based on flotation (DAF) and newly conceived forms of sand filtration. The flotation system is the ideal solution when it is necessary to remove substances from water that are, by nature, lighter than water, which is the case with cellulose fibers. A filtering system using sand guarantees the absence of suspended solids in the water.

* Special Sand Filtration: The main aim of sand filtration is to remove suspended solids, oils and surface agents from the water coming from the air/water separators or the flotation stage. This alone can achieve 99% reduction in suspended solids in hydroentanglement water systems, 60% reduction in surface agents and 50% reduction in oil. In the case of pulp water treatments, combined with a flotation unit, the filtration efficiency is increased to 80% reduction in surface agents and 95% reduction in oil.

* Co-Flow: Idrosistem's filters operate the "co-flow" using a fixed bed of sand. Traditionally, during the filtering stage the filtered substances cause an increase in head loss. When the pre-set value is reached, backwashing occurs automatically using filtered water. However, because of the weight of filtered substances, just using water doesn't adequately clean the filter medium. So Idrosistem's system backwashing uses both water and air.

* Anti-Clogging Water Distribution: The quality of filtration depends mostly on a good distribution of inlet water, the water and air backwashing and an homogeneous drainage in each point of filtering volume. The best drainage and distribution of backwashing water are obtained by means of a "double bottom" plate: the top of which has at least 40 to 50 nozzles per mC, allowing the inlet water to pass through the sand layers while retaining the filtered substances. The nozzles for the water and air backwashing system are made of polypropylene and have elongated ends with holes through which air can pass. In this way an homogeneous air cushion forms between the plate (supporting the nozzles) and the filter bottom. This creates a uniform distribution of air. The efficiency of this type of filter can reach five microns.

* Fixed Bed: The filtering system is carried out from the top to the bottom of the filter on a fixed bed of sand. With these filters it is never necessary to carry out re-integration or replacement of sand and the reduction of suspended solids is much greater than systems that use filters on a fluctuating bed. This backwashing solution completely stops loss of sand during processing and there is never a need to replace the sand.

* Backwashing System: Traditionally, the filter medium is made from fine granulometries that allow for an effective filtration process, but this has the disadvantage of requiring frequent backwashing operations (and consequent filtering interruptions). On the other hand, using a coarse filter medium, backwashings are reduced but the filtration results are not as good. Therefore, to benefit from the advantages of different granulometries, Idrosistem uses a multi-layered filter (with a granulometry range from 0.3 mm to 8 mm).

* Sand Filters With Internal Flotation: The flotation inside the filters is carried out through a recycling mechanism where the water is saturated with air (similar to the one installed in the flotation unit). The filters operate automatically and add peace of mind in respect to the danger of blockages in case the flotation unit is not working at full efficiency. In addition, the system helps to reduce the problems of the foam inside the plant. This means increased efficiency in the removal of any finishing products, for example, surface agents and oils. It is now possible for spunlace producers to use cotton to treat wastewater directly in the sand filters without having to pre-treat in a flotation unit.

* Band-Float: Idrosistem's most recently patented development is an original system that combines Band Filtration and Flotation in one machine. It is used for recycling water back to the production process, for pre-filtering prior to sand filtration and reverse osmosis and TSS and oil removal. The Band-Float is a machine where the water to be filtered enters and comes out clean after the flotation process, which takes place at the top side of it and after the band filtration at the lower side.

In addition to the high levels of efficiency reached, the Band-Float requires less space than a normal flotation and band filtration, requires minimal maintenance and can be either constructed for low and high levels of flow or combined as modules according to clients' needs.