The Problem

The traditional approach to water treatment is to use a combination of treatment stages which could include coagulation, settlement, and filtration to remove contaminants, and then rely on disinfection, where required, to ensure the safety of the treated water.
However, coagulation and granular media filtration, are only partially effective in removing the contaminants, which places a heavy burden on the subsequent stages. Moreover, some contaminants such as Cryptosporidium are resistant to disinfectants.

Membranes offer a radically different approach to the issues of water quality, since the membrane provides an essentially complete barrier to even the smallest contaminant affecting water quality.

The Kalsep Approach   (back to top)

Since its inception as a specialist separations company, Kalsep has been dedicated to providing value engineered solutions to water treatment probLems. Our innovative
Fibrotex fibrous filters (which won the prestigious Hydro Award for Water Quality Improvement) are now installed world-wide with over 500 units in the UK alone. Similar accolades have been received for the development of a new range of high
performance membranes, specifically developed to address water treatment applications. Following awards under the DTI's ETIS and SMART schemes, Kalsep have introduced KALMEM and KALMEM LF membranes to a range of water treatment duties. By combining a breakthrough in membrane performance with reductions in manufacturing costs, Kalsep have breached a cost barrier which once seemed impenetrable.
But Kalsep doesn't just offer membranes. We offer membrane solutions reinforced by process guarantees, extensive trial facilities, and field experience.

Directflow Operation   (back to top)

After initial pre-treatment through a pre-filter, the feed water enters the bore side of hollow fibres in the membrone module. The particulates and macromolecules are retained, whilst the clarified water is allowed to pass as permeate through the membrone. Normally, aperoting in direct/low made, the high flow rote is maintained by a simple backflush using collected permeate. Periodically, a chemical is injected into the back flush to minimise the build-up of fouling contaminants such as scale or biofouling to restore the original flux.

The Technology   (back to top)

Membranes
A membrane is a semi-permeable barrier which enables components of a feedstream to be retained whilst allowing the carrier fluid to permeate through. The pore size of the membrane can be tailored such that the degree of separation can be preciseLy controlled. In water treatment applications, membranes in the ultrafiltration (UF) or microfiltration (MF) size ranges remove fine particulate contaminants.
Kalsep's membranes are made from the polymer polyethersulphone (PES), with pore
sizes throughout the UF and MF ranges. A special low fouling modification has been
used to create a unique series of membranes with remarkable properties. Not only are flux rates enhanced in comparison with conventional membranes, but these flux rates can be sustained even for highly fouling surface waters with cleaning requirements minimised.

Process Design
The most effective format of Kalsep's membrane technology is in the form of fine hollow fibres. By using an internal diameter of as low as 0.8mm, the membrane surface area can be maximised in the module whilst avoiding productivity constraints, due to excessive pressure drop.

Directflow
The advantage of the innovative direct/low process is that the bore side pressure drop is maintained at a low level, whilst high fluxes are sustained by use of a frequent backflush. During the forward flow cycle no retentate or waste stream is drawn from the outlet end of the module. Instead, the outlet is closed to form a dead end, so that any particulates rejected by the membrane become increasingly concentrated within the bores of the hollow fibres. The high permeate flowrate is maintained by a simple backflush using collected permeate for a short time once or twice per hour. During the backflush, any particulate fouling of the membrane surface is removed and, together with the concentrated reject, is flushed from the module. Transmembrane pressures (TMP) are extremely low in the directflow process, typically well below 1 bar.

The Benefits   (back to top)

Water Quality

• Treats feedstreams of widely differing quality to meet water industry targets for metal ion removal and turbidity reduction.
• Reduces Silt Density Index to meet pre-treatment requirements for reverse osmosis or nanofiltration.

Cold disinfection

• Removes viruses and bacteria using ultrafiltration membranes.
• Reduces chlorine demand, and hence contact tank requirements.
• Produces water free from pathogenic micro-organisms.

Chlorine Tolerance

• Can resist a continuous chlorine residual.
• Non bio-degradeable.

Low Backwash

• Minimises wastage of backwash water and reduces the need for ancillary tanks and pumps.

Environmental

• Minimises environmental impact and chemical consumption by eliminating the need for dosing chemicals and reducing expenditure on cleaning chemicals and waste treatment.
• Reduces energy costs by having directflow or low crossflow mode of operation.

Custom Design

• Customises the design of the water treatment system to meet specific needs.

High Performance

• Higher sustained flux, and hence smaller footprint.
• Compact & modular.

The Application   (back to top)

HYDRO-X provides cost effective, high performance filtration of feed water in process streams in a wide range of industries. These include:

• Water Utilities
• Desalination
• Engineering
• Micro-electronics
• Brewing

Major applications for HYDRO-X include:

• Mains water pre-treatment for colloid removal and SDI reduction
• Filtration of potable water supplies drawn from non-mains source i.e. borehole, surface water
• High removal of micro-organisms including crypto, bacteria & viruses
• Filtration of sea water prior to RO treatment

Hydro-X89
Photo by courtesy of Zetex