Sludge treatment Systems:
Filter presses and Filtration is the most widely used technique in the treatment of sludge made by wastewater treatment. It can consist simply in drainage though sand beds or it can be mechanical underneath vacuum middle or high pressure conditions which need additional sophisticated equipment.
Filter presses operate applying terribly high pressures to the cake (from 5 to 15 bars and sometimes even a lot of).
Plate filter presses :
This pressing technique is the foremost widespread despite its intermittent operation and its high investment price.
Filter presses Description :
A filter contains a collection of vertical, juxtaposed recessed plates, presses against each other by hydraulic jacks at one finish of the set. The pressure applied to the joint face of each filtering plate should stand up to the chamber internal pressure developed by the sludge pumping system.
This vertical plate layout forms watertight filtration chambers allowing simple mechanisation for the discharge of cakes. Filter chlotes finely or tightly meshed are applied to the two groowed surfaces in these plates.
Orifices feed the sludge to be filtered below pressure within the filtration chamber. They are typically placed in the center of the plates permitting a proper distribution of flow, right pressure and better drainage of sludge among the chamber.
Solids sludge gradually accumulates within the filtration chamber until the final compacted cake is created. The filtrate is collected at the rear of the filtration support and over excited by internal ducts.
Filtration cycle :
The filter press is an intermittent dewatering process. Each press operation includes the subsequent steps:
1- Closing of the press: because the filter is totally empty, the moving head activated by the jacks calmps the plates. Closing pressure is self regulated through filtration.
2- Filling: During this short section chamber are crammed with sludge for filtration. Filling time depends on the flow of the feed pump. For sludge having good filterability it is best to fill the filter terribly quickly thus as to avoid the formation of a cake in the primary chamber before the last ones have been filled.
3- Filtration: Once the chamber have been filled continuous arrival of sludge to be dewatered provokes an increase in pressure thanks to the formation of an increasingly thick layer of filter sludge on the cloths.
This filtration phase can be stopped manually, by a timer or a lot of convenientely by a filtrate flow indicator which issues a stop alarm when the tip of filtration rate has been reached. When the filtration pump has stopped, the filtrate circuits and central duct, that continues to be crammed with liquid sludge, are purged by compressed air.
4- Filter gap: The moving head is drawn back to disengage the first filtration chamber. The cake falls features a result of his own weight. A mechanised system pulles out the plates individually. The speed of plate separation can be adjusted to account to the cake texture.
5- Washing: Whasing of clothes ought to be administrated every 15-thirty processing oprations. For mid- or massive units this occur on press using water sprayers at terribly high pressure (80-100 bar). Whasing is sincronized with separation of plates.
Filtration capacity :
The production capability of a filter press is somewhere between one.five and ten kg of solid per m2 of filtering surface. For each the filter press model the chamber volume and also the filtering surface depend on the number of plates within the filer.
In sensible terms pressing times are less then four hours.
Filtration time depends on:
- – cake thikness
- – sludge concentration
- – specific resistance
- – compressibility coefficient.
One of the benefits of the filer press is that it can accept sludge with average filterability. It is usually advantageous to optimally thicken sludge before filter press operations. Although sludge presenting a high filterability permits better production capacities, a filter press still accepts sludge with low conditioning precision.
This tolerance suggests that that the device offers larger owerall operational safety.
Filter presses Performance :
The filter press is appropriate for pretty much all sorts of sludge:
- Hydrophilic organic sludge: inorganic conditioning is usually suggested to enable satisfactory cake unharness thanks to minimal aderence to filter cloth.
- Hydrophilic inorganic sludge: the filer press usually requires the addition of lime only.
- Hydrophobic inorganic sludge: it is terribly dense and ideal for the filter press. It’s dewatered while not any preliminary conditioning.
- Oily sludge: the filter press can be used to treat sludge containing light oils, the presence of grease can sometimes impair the smooth running of the filter; clothes must be degreased at frequent intervals.