Products > Cloth filters > Cloth filters: advantages and application

Cloth filters: advantages and application

System advantages

  • Gravity filtration with limited head loss
  • Continuous filtration without standby units for the backwash phases
  • Cloth filter in polstoff free fibre provided with high mechanical strength
  • High filtration rate (concentrations of TSS < 5 mg/l at discharge)
  • Cloth backwash with very low energy consumption
  • No aerosols and noise pollution
  • Flexibility in case of overloading and self-regulating with regard to the input parameters
  • Minimum dimensions
  • Reduced electrical consumption (max. 1.9 kW per equipment)
  • Low backwash water volumes
  • Simple operation, in monobloc or concrete tanks models
  • Limited maintenance
  • Direct access to all utilities
  • Limited environmental impact

Application fields

  • Tertiary treatment: the cloth filters are used with great success for tertiary filtration downstream of secondary settling tanks in biological wastewater treatment plants, both civil and industrial. Their application was brought forth from the need to have an increasingly high water quality at the inflow point of the receiving water body. The rate of removal of suspended solids is very high and the concentration upstream of the filter is of < 5 mg/l. The MITA Water Technologies cloth filters often perform an important barrier function to light sludge spillage that would otherwise exceed the limit of suspended solids concentration in the discharge. The simple construction and operation of these machines are fundamental, as well as theminimum need for routine and supplementary maintenance.
  • Phosphorus reduction: in purification plants, the reduction of phosphorus concentration in wastewater discharged into bodies of water can be done with two types of treatment: simultaneous phosphorus precipitation in an activated sludge oxidation tank, with the right chemical dosage; further phosphorus precipitation in a solution in dedicated tanks called “post-precipitation” downstream to the secondary settling, again with the right chemical. In both cases the cloth filterinserted as the last filtration step resolves the key function of sludge separation contained in the phosphorous. Given the very high rate of solids removal( TSS < 5 mg/l), very low concentrations of this element are obtained.
  • Upstream pre-filtration disinfection with UV: the disinfection of purified wastewater before the inflow of receiving water bodies is increasingly done with UV systems. These systems for reasons of UV functioning efficiency, reducing energy consumption and fouling on the surfaces of UV lamps require that water to be treated should have a very low content of suspended solids; in general a concentration under 10 mg/l is requested. The cloth filter can be perfectly included in the upstream UV treatment, generously ensuring the quality of the water requested and therefore the efficiency of the disinfection system.
  • Downstream filtration of chemical-physical treatments: some production processes in the industry field lead to the production of polluted water from metals for example, in ionic-soluble form that can be separated in the form of sludge flakes due to the dosage of the right chemical compounds. The separation of this sludge may be obtained by using the cloth filters, which cloth also adapts to the type of chemical sludge.
  • Secondary sedimentation downstream of immobilized biomass processes: the cloth filter is used to replace the secondary settling only in cases in which the biological treatment is carried out with technologies such as immobilized biomass, biodiscs and percolating filters. In these cases, the wastewater from the biological stage has such a high sludge concentration that it can be treated directly with a cloth filter (without a secondary sedimentation stage), which ensures that the discharge has a content of suspended solids surely less than 35 mg/l and almost always less than 10 mg/l. In this regard, MITA Water Technologies developed acompact biocombi plant which combines biorulli® and the secondary sedimentation with the cloth filter, which represents the application of above examples.
  • Upstream membrane pre-filtration processes: in the case of very thorough civil or industrial wastewater treatments with the purpose of reusing the same water in the industrial and at times in the civil fields, ultrafiltration and reverse osmosis technologies are used with the membranes. The use of reverse osmosis requires a water supply with a very low content of suspended solids in order to protect the membranes from fouling as much as possible thus limiting the frequency of necessary washes to maintain the performance of the system. Even in this case the cloth filter is an optimum filtration system for an upstream treatment with reverse osmosis membranes.
  • Pre-filtration of superficial waters: superficial waters, often used for the supply of drinking water undergo a pre-filtration, as first treatment, suitable for the separation of solid particles in the form of silt, microalgae and others.The cloth filter is a useful filtration system to for this purpose with or without an upstream flocculation treatment.

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