DRAIMAD® sack filter
Descriptionback to top
The DRAIMAD® system dewaters and bags sludge from industrial effluent and domestic wastewater treatment plants. The system is capable of treating up to 200 kg D.S. of sludge a day. The DRAIMAD® system has been designed and manufactured by TEKNOFANGHI Ltd, Milan, Italy.

Operating principlesback to top
This system is modular and is designed to optimise the filling and dewatering cycle of the filter bags. Once this cycle is over the full bags can be removed, sealed and stored in the open air for a further period of dehydration, reducing the weight and volume of the sludge cake. The special water repellent material of the sacks prevents rainwater from entering but allows dehydration of the contents by evaporation. The sacks are mounted on a special stainless steel frame, designed to distribute the sludge. The system is electronically controlled from a programmable control panel, ensuring correct process operation. Before dewatering the sludge should be conditioned with polyelectrolyte. After a few hours operation, dry solids content of 15 - 20% can be achieved, depending on the nature of the sludge. The volume of dewatered sludge is dependent on the solid content. For 1% dry solids, one machine can treat up to 20 m3 per day.
After the initial dewatering stage on the machine, the sacks are sealed and removed with a special sack trolley and stored in an open area (after 10-24 h). During the second phase, due to the special hydrophobic sack material, sludge weight and volume continue to reduce, regardless of weather conditions. After 2-3 months storage, a cake of 50-70% dry solids content is produced. As an example, 1500 kg of sludge at 1% solids content would give, after the first phase - weight of sludge 70-80 kg ( 20% dry solids), after two months, a cake of at least 50% dry solids content. This would weigh only 35 - 40 kg and represents almost a 50-fold reduction of the original weight.

Sludge conditioning with polyelectrolyte Draining
Sludge dewatered after 24 h Sacks stored in the open area

Structureback to top

Various models are available, with 2, 3, 6 and 12 sacks. Operation may be manual, with filtration taking place under gravity, or automatic with pressurised filtration. Multiple units may be installed, either in series or in parallel, to meet any requirements. The features of all models:

  • compactness and low space requirements,
  • an internal sludge distribution system with sack collars and clamps in stainless steel,
  • a drainage collection tray beneath the machine and sack positioned for easy handling,
  • filtrate collection tank.

Automatic operation

Automatic operation consists of: programming to optimise filtration cycles and maximise capacity, the ability to alter the operating cycle to handle sludges with varying characteristics, automatic operation of a sludge feed pump or valve to feed sludge to the unit as required, automatic finishing of the filtration cycle when the unit is full and the option of extending the pressurisation phase.

Pressure operation

Pressurisation using low pressure air (0.2 - 0.3 bar) almost doubles the capacity of the units. The sacks are mounted in stainless steel cages designed to allow rapid sack replacement.

Advantagesback to top
  • high efficiency, dewaters to 50 - 70% D.S.,
  • low operating and maintenance costs,
  • min. consumption of energy,
  • very small area of installation,
  • low costs of transport, sludge mass decreased up to 60 times,
  • use of normal means of transport for sludge disposal,
  • modular units - easy to increase capacity,
  • simple to install, without special construction work,
  • simple to operate by one person,
  • safe for environment,
  • highly effective and reliable operation throughout the year,
  • total costs reduction of sludge disposal.

Sludge dewatering in open area after 30 days

Technical databack to top
L x W x H [mm]
O2BM 2 1140x560x1500 manual
O3BM 3 1550x550x1700 manual
O3BCAVPK 3 1900x550x1920 automatic
O6BCAVPK 6 1900x1050x2000 automatic
12BCAVPK 12 3350x1100x2000 automatic
Sack - about 15 kg D.S. each

Referencesback to top
There are more than 5000 Draimad® installations in operation - mainly in Europe and USA. The system has been used in Poland for more than 700 municipal and industrial sewage plants. The DRAIMAD® system is made according to CE standards. It has been granted the approval of Polish Health Ministry and Technical Approval of Environmental Protection Institute in Warsaw (AT/97-08-0004). The DRAIMAD® system was awarded Golden Medal at International Environmental Fair POLEKO' 96 in Poznan.

For more information about locality and references, please contact us.