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Fish hatchery effluent control
Published in Richard W. Soderberg, Aquaculture Technology, 2017
Microscreen filters are available from several manufacturers and operate by passing water through a fine-mesh screen. In the case of a drum filter, the screen is in the form of a cylinder. A disc filter retains solids with a series of circular, vertical screens. Disc filters are preferred over drum filters for treating large water volumes, such as total system flows, due to their greater hydraulic capacities. Drum filters are usually selected for treatment of QZ or dual-drain tank waste, where smaller water volumes are involved. Water passes from the inside to the outside of the screen. When pores clog, as determined by a water level difference across the screen, the backwash mechanism deploys and solids are washed from the screen into a waste discharge line, that leads to an off-line settling basin for final treatment (Figure 10.2). During typical operation, the screen is washed from several hundred to several thousand times per day (Libey 1993; Summerfelt et al. 1999). Compared to other methods of suspended solids removal, microscreen filters have high hydraulic capacities, low space requirements, and small water loss to waste disposal. Summerfelt (1999) reported that microscreen backwash flows range from 0.2% to 1.5% of total system flows. Schematic diagrams of drum and disc filters are found in Timmons and Ebeling (2013).
Particle Characterization and Dynamics
Published in Wen-Ching Yang, Handbook of Fluidization and Fluid-Particle Systems, 2003
Rotary Disc Filters. Rotary disc filters are another kind of rotating filters, as shown in Fig. 5 (Svarovsky, 1990). This type of filter provides a much larger filter area per unit of floor area at lower cost than those of the rotary drum filter. Their applications are in coal preparation, ore dressing, and pulp or paper processing. The rotary disc filter is constructed by a number of discs (up to 12 or more) mounted on a horizontal hollow shaft. Each disc is equipped with interchangeable elements and has an individual slurry compartment. Submergence up to 50% of the filtering surface can be attained by a level control. The cake formed on the emergent sector of the disc is treated and removed by washing and scraper before reentering the trough. The filter area or filtering capacity can be adjusted by the change in the number of discs. Disc filters are available in filtering areas from 0.5 to 300m2. The disc filter is mostly used as a dewatering or thickening device. Owing to the vertical filtering surface, cake washing in the disc filter is not as efficient as in a drum filter. The rotary disc filter is particularly beneficial in cases of limited space and where cakes do not require washing.
Paste dewatering techniques and paste plant circuit design
Published in A.A. Balkema, Tailings and Mine Waste 2000, 2022
Various types of pressure filtration equipment are available. The most common types are the vertical chamber filter presses, the continuous belt horizontal chamber type and the type where a disk or ceramic disk filter is enclosed in a pressure vessel. Some pressure filters, of the vertical chamber type are in use for tailings dewatering for dry stacking purposes. Generally pressure filtration would be overkill for paste fill dewatering. There is a higher capital cost and unless there is another requirement such as cake washing of a cyanide containing gold tailings there normally would be no incentive to go beyond thickening and vacuum filtration or deep tank dewatering.
Advances in dewatering and drying in mineral processing
Published in Drying Technology, 2021
Benitta A. Chaedir, Jundika C. Kurnia, Agus P. Sasmito, Arun S. Mujumdar
Another possible option to the drum filter is the disk filter (Figure 4b), which operates on principles analogous to that of rotary drum filters but instead of one large drum, uses several disks installed vertically on a horizontal shaft, separated by about 30 cm, and suspended in a slurry container. This configuration increases the surface area for a given footprint by up to a 4 times with the consequence of making the cake washing virtually impossible.[23] Furthermore, careful level control is required for the operation of disk filters because they need to operate at high submergence. The disk filter consists of separate sectors (between 12 to 30 sectors) that are covered by cloths and connected to a filter valve. The disk rotates and lifts the solids cake that is produced to location above the surface of the slurry in the trough, where the cake is then dried by suction and removed. The cake discharge in conventional disk filters is usually performed by a scraper blade with pulsating air blow. High pressure sprays or tapered roll have also been used for cake discharge. The minimum cake thickness for discharge is usually higher for disk filters as compared to drum filters; about 10 mm and 3 mm, respectively. The rotation speed can go from a moderate 20 rpm to a high 180 rpm. The disk size ranges from 0.5 to 5.3 meters, with as many as 20 disks can be assembled on one shaft.[23]