The Nile surface water is pre-treated using reverse osmosis with a total of 228 Lewabrane B400 FR elements and fully demineralized with Lewatit MonoPlus ion exchange resins.
COLOGNE, GERMANY: Lanxess’s ion exchange resins and membrane elements work effectively together in the new water treatment plant of Egypt’s leading fertiliser manufacturer Alexandria Fertilizers Co (Alexfert) in Alexandria.
The saline water is pre-treated using reverse osmosis (RO) with a total of 228 Lewabrane B400 FR elements and fully demineralized with Lewatit MonoPlus ion exchange resins. In addition to completing the required final demineralized water conductivity of below 0.08 μS/cm (microsiemens per centimetre) and 2 ppb SiO2 (silicon dioxide), combining the two technologies also provides a stable and reliable process.
The new brackish (saline) water reverse osmosis (BWRO) plant in Alexandria is fed with canal water from the Nile. The seasonally variable inorganic and organic TDS (total dissolved solids) content are between 300 and 550 milligrams per litre.
The water is pre-treated using precipitation and flocculation (coagulation), cold lime softening and filtration. During softening (decarbonization), the hardened calcium carbonate is precipitated through slurrying of calcium hydroxide in order to avoid scaling. Such deposits of particles on the membrane would otherwise block it and make it less effective.
The RO plant entails of two trains, each with a feed stream of 120 m³/h and a recovery rate of 74 percent. A single train is composed of two stages of a 13:6 array with six elements per vessel. The RO plant was installed in an existing water treatment plant to provide pre-treatment for full demineralization with Lewatit MonoPlus resins.
The Lewabrane RO elements verified their excellent salt rejection of up to 99.76 percent (at 20 °C) from the outset. This rejection results in an infuse conductivity in the order of 3 to 5 μS/cm, which meaningfully decreases the ionic load for the resins at the demineralization unit. While maintaining the required parameters of demineralized water, the cycle times of the demineralization trains are increased by up to four times (depending on the season and with the possibility of a further increase).
“The membrane elements from Lanxess exhibit an excellent level of performance with the difficult Nile surface water. The rejection measured even exceeds expectations,” said Alexander Scheffler, director membrane business at Lanxess’s liquid purification technologies (LPT) business unit.
“Using reverse osmosis for pre-treatment means we can reduce the consumption of specific chemicals for resin bed regeneration by around 60 percent,” added Ashraf Aly Mostafa, project manager at Alexfert.
© Worldofchemicals News