Screening...

Coarse screens or bar racks (< 2.5 inch openings) : (1) removes large objects, rags, debris ; (2) protects downstream pumps, valves, pipelines ; (3) cleaning may be accomplished manually or mechanically ; (4) mechanically cleaned bar racks (5/8 inch - 1-3/4 inch) typically used instead of coarse manually cleaned screens ; (5) bar rack is inclined to facilitate , cleaning ; (6) approach velocities should ensure self-cleaning, but not dislodge solids ; (7) typical design : maximum velocity of 2.5 ft/sec through bar rack opening.


SEKA - Dalaman Pulp and Pulpmill Wastewater Treatment Plant...
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Fine screens (as small as 1/32 inch openings) : (1) frequently used in municipal plants ; (2) used in industrial pre-treatment to remove suspended and settleable solids (e.g., wastewater from cannery and packing houses.

Shredding devices (communitor or grinder) : shreds material to 1/4 inch - 3/8 inch.

Headloss calculations determine the hydraulic head requirements for screen installation :

0.7 : empirical discharge coefficient to account for turbulence and eddy losses
V : velocity of flow through openings in rack (m/s)
v : approach velocity in upstream channel (m/s)
g : acceleration due to gravity (m/s2)


Note that headloss through clean screen is relatively insignificant, but increases during operation depending on solids characteristics and cleaning.


A Trade Mark : HUBER - ROTAMAT...

The ROTAMAT - Fine screen can be installed in a separate container as well as directly into the channel. The waste water flows through the open front side into the basket and its screen bars (see sketch) into the channel. The screen bars hold the polluted material. This blinding has the effect of an additional filter. At a certain height difference the rake arm positioned on a centric middle axle is switched on. Its tines clean the basket grasping completely through the screen bars, take out the whole screenings and throw it in vertical position (12°° o`clock position) into the centrically positioned trough with conveying screw. With the rotational movement of the conveying screw the screenings are transported out of the channel. For a better and complete cleaning of the tines the rake comb moves back into its upper position abt. 15°: the tines are additionally cleaned by a scraper.

During transport the screenings are compacted, washed and dewatered to a solids content of up to 40 % DR. To optimize the cleaning process, the integrated screenings washing contributes to optimize the relation of nitrogen/oxygen and additionally helps to save costs in screenings disposal. With the ROTAMAT principle it is possible to integrate the screenings washing directly into the trough or under the rising pipe. The soluble components are separated from the inert material. Here the faeces are nearly completely washed out, resulting in a considerable weight reduction.

High separation capacity : Due to the diversion in the basket the fibrous materials and the bar-shaped particles are considerably better retained than the particles flowing straightly to the rack screen.
Low head loss : Due to the drum shape and the 35° erection considerably more screening area is available for the cleaning than for instance at vertically or in an inclination installed screening systems. Consequence: a low head loss.
Completely made of stainless steel : The machine is completely made of stainless steel and pickled in the bath. Thus there are no maintenance works due to corrosion.
Automatic cleaning : By means of the circulating screening rake the complete screening area is totally cleaned, i.e. even at high pollution load the automatic cleaning ensures a constantly free screening area. Additionally, there is the guarantee that the screenings remain constantly inside the basket (mostly in front of the screening area), thus ensuring that the screenings are not taken out of the waste water and are not transported into the already cleaned waste water behind the screen during the cleaning process.
Several functions : The machine includes several functions in one system, i.e. screenings removal, transport, dewatering and compaction are included in one plant, thus saving place. By means of a bagging unit the whole plant is nearly odour-encased.
Outdoor installation : With a strip heater and additional insulation the ROTAMAT - Fine Screen can also be used for frost-proof outdoor installation.
Additional equipment : The ROTAMAT plants are designed in that way that additional modifications at the plant can be carried out afterwards, i.e. the machine can be re-built acc. to future requirements. Heating as well as integrated washing can be installed later, the bar spacing can also be reduced later.
Nearly maintenance-free machine : The plant has no lubrication point, maintenance is reduced to regular control and inspection tours.



The following table will enable you to determine the size (drum diameter in mm) of the fine screen due to the maximum flow rate. The figures mentioned are standard values. The maximum screenings amount which can be treated is decisive for dimensioning the plant (sudden washing peak). The influence of pollution load, channel geometry, and installation conditions has to be taken into account as well.

Size Maximum flow - rate Maximum level of impoundage (mm)
Bar spacing = 6 mm Bar spacing = 10 mm
L / s m3 / h L / s m3 / h
600 82 295 91 328 340
780 136 490 150 540 395
1000 218 785 239 860 515
1200 312 1,156 343 1,235 620
1400 435 1,566 478 1,721 780
1600 633 2,279 697 2,509 920
1800 852 3,067 927 3,373 1,040
2000 - - 1,145 4,122 1,190
2200 - - 1,375 4,950 1,290
2400 - - 1,752 6,307 1,400
2700 - - 2,227 8,017 1,550
3000 - - 2,757 9,925 1,700

Rotary Drum Fine Screen...

Rotary drum fine screens with high efficience for removing SS and economic cost. Rotary drum fine screen is made of stainless-steel and P.P screen cloths. Rude water is feed into drum, then the water is drained off from drumby liquid pressure difference. Meanwhile the filtration, washing cloth and discharge will be completed at one time. The 5-80 µm of particle can be filtrated by rotary drum fine screen. The maximum capacity of tereatment is 140 m3 / hr and the COD of BOD will be removed 40 % - 50 %.

"Definition Sketch for Drum Fine Screens - 1"...

"Definition Sketch for Drum Fine Screens - 2"...

Model Capacity ( m3 / hr ) W ( mm ) L ( mm ) H ( mm ) P1 P2 Power ( kW )
AS 20 5 - 20 800 1,000 800 4 4 1
AS 50 20 - 50 1,000 1,400 1,000 4 6 2
AS 90 50 - 90 1,200 1,600 1,200 6 6 x 2 3
AS 150 90 - 150 1,600 2,200 1,600 6 x 2 8 x 2 4.5