R. Rautenbach et al., Treatment of severely contaminated waste water by a combination of RO, high-pressure RO and NF - potential and limits of the process, J MEMBR SCI, 174(2), 2000, pp. 231-241
High water recovery rates are essential for waste water treatment. Tn cases
where not scaling but the osmotic pressure limits the recovery rate, the o
peration of a high pressure reverse osmosis (RO) is feasible. But this stud
y shows that either the compaction of the presently available RO membranes
or costs limit the operating pressure to about 150 bar maximum.
The integration of a nanofiltration into a staged RO process can solve the
problem in cases where chlorides are the reason for high osmotic pressures
and scaling is due to calcium sulfates. For the treatment of dumpsite leach
ate, several large scale plants are operated since 1994 in Germany with an
average water recovery rate of 95%! (C) 2000 Elsevier Science B.V. All righ
ts reserved.