Clarifier Overflow Filtration
Waterex Upflo Filters
The Waterex range of Upflo Filters are designed for applications having high dirt holding demands. They are typically used where coarser materials may also be present in appreciable quantities.
Upflo filtration offers several advantages including in-depth filtration, graded filtration from coarse to fine in a continuous media grading plus a high service filtration velocity. Waterex Upflo Filters in several applications may be cleaned with the raw feed water. These features make the Upflo Filter the most robust media filter for onerous high load applications.
Providing a normal running capacity of 500m3/hr for 24 hours a day, the purpose of these filters is to strip 100mg/l from thickener overflow liquor. This total suspended solids (TSS) can rise up to 200mg/l under adverse conditions.
The design has the flexibility and capacity to increase the flow rate to 1000m3/hr peaking at 1400m3/hr or alternatively accept a peak dirt load of 500mg/l for short duration or even both.
The challenge of this project was to provide a filter plant that could handle the high amount of TSS while providing the required duty point of 500m3/hr. The plant was further required to fit in the limited amount of space provided. Being located in a remote area with limited supply support services it was also desirable to design a simple filtration system that is easy to operate. Double decker Waterex Upflo Filters were therefore the filters of choice.
The Waterex Approach
Waterex selected to use two Upflo Filters, each with two beds. This double decker array provides a compact footprint to filter 400-1000m3/hr capable of a peak flow of 1400m3/hr . The air scour feature with controlled backwash/backflush water cycles ensures the effective cleaning of the media through each layer of its stabilised beds, each bed being cleaned in sequence.
At the design flowrate a single train bed Upflo Filter reduced the raw feed TSS from 255 - 285 NTU (125-147mg/l) to 33 NTU (15mg/l) TSS.
The catalytic action of the media removes iron precipitates and ions from the process liquor. The effective air scour/backwash cycles indicates that the small amounts of excess polymer are being flushed to drain. The second twin bed Upflo Filter is therefore run as a 100% standby unit providing the intended maximum flexibility demanded of this critical process liquor recovery plant.