On September 8, 2000 the General Assembly of the United Nations resolved to support the Millennium Developments Goals (MGD) stating (amongst other goals) to halve by the year 2015 the number of people living without the access to safe drinking water. Without arguing about the right number the amount of people to be served will be over the 1 billion persons.

To fulfil this challenge small-scale systems should be available requiring simple operation, easy maintenance, robustness, and sustainability. Moreover, these systems should be appropriate to local conditions, such as small communities in developing countries without a centralised piping system or without well-protected water sources. New technologies, such as capillary nanofiltration, enter the water treatment market in order to produce potable water using lower quality sources as main feed stock.
 

The Norit Direct NanoFiltration system is an excellent 1-stage system for the small scale potable water production applying the patented semi dead-end process mode for nanofiltration. Due to its unique nature the capillary nanofiltration module requires a minimum of pre-treatment. During production the vertical placed membrane modules are operated in semi dead-end mode applying a small cross-flow in the closed looped system. During cleaning the loop is opened and purged effectively by the patented AirFlush® procedure as well as by a backflush. The product is potable water at low cost.
 

Norit Direct NanoFiltration systems are used for:

• suspended solids content up to 200 mg/l;
• decolouring (>95%); softening (40-80%); and complete bacteria and virus removal.

Main references for potable water production in remote areas are found in:

• small water supplies.
   

The Norit Direct NanoFiltration system uses X-Flow modules:

• 1.5 m long 8” PVC modules with CAPFIL 1.5 mm nanofiltration membranes;
• with unique composite, high flux, backflushable nanofiltration membranes combining the good cleaning hydraulics of capillary membranes with the separation characteristics of spiral wound composite membranes.
   

In a semi dead-end system all the feed supplied to the systems leaves as permeate. The capacity is controlled by adjusting the transmembrane pressure. At regular time intervals the system is subjected to an AirFlush® combined with a backflush to purge the feed side and to remove the retained components. Adsorbed substances can be removed by an "in situ" chemically enhanced cleaning.

Norit Direct NanoFiltration systems are available as standardised, modular plug-and-play skids. The modules are placed vertically resulting in very reliable and compact installations, easily to be placed in containers.

If desired customer-built systems can be supplied.