Research is being conducted on a pilot plant scale at the Amsterdam Waterworks. The purpose of the study is to demonstrate that reverse osmosis can make a fundamental contribution to the improvement of the quality of potable water obtained from surface water. The study focuses on the removal of natural and non-natural organic substances in the water, the removal of bacteriophages, cleaning and disinfection of the membranes and the type of pretreatment necessary to make the water as suitable for membrane filtration as possible.
The pilot plants achieved the expected water quality improvement, although, as a result of biological growth, the cleaning frequency is still higher than expected, despite the low content of organic material in the water supplied and the low colony number present in the inlet water.
It appears that the pretreatment with ozone and biologically activated carbon and/or the inhibitor stimulates biological growth on the membrane. The permeate resulting from the reverse osmosis process meets, and even surpasses, all bacteriological requirements that apply to potable water.
Evaluation of the integral additional costs for the expansion of the plant at Leiduin shows that employment of the reverse osmosis process does not mean extra costs for the consumer. The additional costs resulting from the RO process are recovered through savings on detergents and reduced maintenance of equipment resulting from a decreased water hardness.