Hidrológiai Közlöny 2006 (86. évfolyam)
3. szám - Kaposvári Kázmér: Effect of the intervening ozonizing and Biologie Activated Carbon treatmant to drinking water produced by water supply intake at the River Tisza Szolnok
28 HIDROLÓGIAI KÖZLÖNY 2006. 86. ÉVF. 3. SZ. 300 0 00 «jr .js* N<=r & N°r & & ^ ^ ^ & Fig 2 : The residual CODps content of the treated water after the sand filters and the active carbon filters As far as the water quality is concerned the performance of the activated carbon filters is decisive. For the Tisza water the primary requirements are the reduction of the taste and odor effects and securing the biological stability of the distribution network. The major parameters for the latter are the residual COD and the AOC. The activated carbon adsorbers are operating continuously with 72 hours cycle periods and air/water backwashing. The pouring density is almost stable and the retention time is 18-23 minutes when 5 filters are running. The combined specific load (m 3water/kg carbon), the total adsorbed organic matter concentration c (g COD/lkg carbon) and the active carbon status indicator iodine number J N o (mgj 2/l g carbon) do not show unambiguous interrelation with the residual COD and AOC. The iodine number fell below 500 mgJ 2/l g C from the initial value, while the residual COD P S did not rise significantly. Fig 3 shows the data of the 15 t h December, 1998 - 31 s t December, 2002 period which represent the results of the first five CHEMVIRON CARBON F 30 o adsorber charges. Total volum9tilc lood (m'waitr/lkgC) Fig 3: The variation of the total adsorbed organic matter (CODp) and the active carbon filters' adsorption capacity (Iodine number) in the function of the specific hydraulic load From the beginning of 2003 four additional, newly charged NORIT RON 0,8 SUPRA adsorbers have been commissioned. The total load on the F 30 0 adsorbers is 328 m 3 water/kg carbon and 118 g COD/kg carbon at the end of 2004. The function of the totalized adsorbed organic matter CODp S is linear. According to the status of the iodine number it should have been in a saturated stage a long time ago. The value of the iodine number, i.e. 350-380 mgj 2/g carbon implies around 70% saturation in the active micro-porous structure. However, this is neither reflected in the taste and odor detections nor in the values of the residual COD and AOC. Presumably, the microbiological decomposition processes in the biofilm got strength and contributed to the removal of the organic matter from the carbon charge. The chemico-physical sorption processes become de-emphasized. In this situation the COD P S (or TOC), acting as a group (surrogate) indicator, masked the processes which are the consequences of the selective adsorption, the displacement and competitive effects, being typical processes of the adsorption mechanism in the active carbon bed. The microbiological decomposition is based on adaptive „flora steady state" operation, which can work properly near to the conditions of the adaptation only. The ozonization applied upstream the activated carbon adsorption is a widely used method. Here the role of the ozonization is expressed in the GAC->BAC conversion and in the maintenance of the latter, which role is proved and supported by theoretical derivations as well. In the Szolnok water purification plant nine quick sand filters are being operated before the active carbon adsorbers. The synchronized operation of the sand filters and the active carbon units brings up several questions. The prevention of the active carbon from the residual ozone and the shaped elements, especially from the secondary disperse and disperse bonded organic matter loads formed during the ozonization is a positive contribution. The typical turbidity of the sand filtered water is Z < 0,2-0,3 NTU. 18-22 % of the total organic matter removed during the treatment stays back on the sand filters. On the other hand, t ~ 40 minutes retention time and abundant carbon source for the bacteriological processes are
