AWWA ACE56321

Because of high contents of microorganisms and pesticides in IJssel Lake water, N.V. PWN Water Supply Company North Holland (PWN) has decided to implement UV/H2O2-treatment at the surface water treatment plant at Andijk. In collimated beam experiments both Giardia muris and Cryptosporidium parvum proved to be very susceptible to ultraviolet (UV) radiation. UV doses as low as 20 mJ/cm2 resulted in a 2 and 3 log inactivation respectively. Both Bacillus subtilis endospores and MS2 phages were shown to be more resistant to UV. MS2 phages showed the greatest resistance, UV doses as high as 105 mJ/cm2 were needed for 3.5 log-unit inactivation. The results were confirmed by pilot plant data. At a dose of 105 mJ/cm2 there was no evidence of reactivation. However, there was evidence that Giardia muris cyst reactivation may occur at an UV-exposure lower than 25 mJ/cm2. The data demonstrate that medium pressure UV radiation effectively inactivated the microbial pathogens and indicator organisms for a UV dose of 105 mJ/cm2. UV photolysis showed a selective pesticide degradation. Conversion using an electric energy of 1 kWh/m3 varied from 18% for trichloroacetic acid to 70% for atrazine. UV/H2O2-treatment gave a much more aselective pesticide degradation. For a broad range of combination of electric energy (< 1 kWh/m3) and H2O2 dose (< 15 g/m3 H2O2) all pesticides can be degraded for more than 80%. This UV dose of 1 kWh/m3 (1200 mJ/cm2) is much higher than needed for disinfection. Formation of harmful byproducts proved to be insignificant. In the range of 0.1 - 2.5 kWh/m3 electric energy and 0 - 25 g/m3 H2O2 bromate formation was absent, while primary metabolite formation was insignificant. AOC-formation was found up to 140 ug/l. Therefore AOC and residual H2O2 must be removed. Granular Activated Carbon (GAC)-filtration showed very reliable results. In view of the very promising results, application of UV/H2O2-treatment will be implemented in the Andijk plant for both organic contaminant control and disinfection. Includes tables, figures.

Product Details

Edition:

Vol. - No.

Published:

06/16/2002

Number of Pages:

11

File Size:

1 file , 350 KB