386
I. Licsko et al.
In our experiments we found significant differences in the types of organic
matters in raw sewages. The necessary coagulant dose for 60% CODer removal
was much higher in the case of NI, than in BI, but the difference was not so
significant in the total organics content. Concerning our experiments the minimum
dissolved organics removal in B 1 sewage varied between 10 and 25%. This is the
minimum rate, because settled samples were analyzed. The settled samples
contained about 10-30 mgr l suspended matter. This suspended matter consists of
mainly aluminum or iron(I1I)-hydroxides, but also some organics. The maximum
removal rate of dissolved organics should be a little higher than 20-25%. There are
no significant differences in the efficiency of aluminum and iron salts, taking the
molar doses into consideration.
In the case ofNI there was significant difference between the organics removal
efficiency of aluminum and iron(III) salts. Figs. 1 and 2 demonstrate that the total
organics and dissolved organics were removed much more effectively by using
aluminum salts (aluminum-sulfate rather than poly-aluminum salts) than iron(I1I)
compounds. The same effect is demonstrated in Fig. 3, where the remaining
dissolved organics (in percentage of raw sewage dissolved organic content) vs.
molar ratio of the aluminum and iron(I1I) compounds is presented.
Fig. 3 shows that dissolved organics removal could be achieved 60% by
aluminum sulfate, and 40% by feeding iron(I1I) compounds, while the remaining
CODer values were not less than 200 and 300 mgr l respectively. There is a
significant difference between the NI and B 1 cases. Figs. 2 and 3 well
demonstrate that the dissolved and total organics removal rates - provided by the
aluminum sulfate feeding - are close to each other. We have never found this high
organics removal rate concerning dissolved organics, either in international, or in
our experience previously. This fact shows that the quality of dissolved organics
plays a very important role in the removal processes.
In another experiment, the results of feeding aluminum compounds show much
poorer organics removal efficiency. Figs. 1 and 2 demonstrates that aluminum
feeding resulted in 25-40% organics removal, but the remaining CODer is not
higher than 150-200 mgrl. The molar ratio of the added aluminum compounds
varied between 1.0 and 0.6 mmolr l , while in the earlier experiment it was 2.2
mmolrl. There is no significant connection between the dose of aluminum
compounds and the removed organic content as percentage of raw sewage CODerConcerning the maximum removal rate results, the minimum remaining CODer
values are not less than 150-200 mgr l (Fig. 1). These CODer levels in chemically
treated sewage could be achieved by 40-60% organics removal efficiency. In the
case of NI the connection between the 60% removal rate and the necessary
feeding of aluminum and iron (III) compounds could be approached by linear
functions (Fig. 2).
I. Licsko et al.
In our experiments we found significant differences in the types of organic
matters in raw sewages. The necessary coagulant dose for 60% CODer removal
was much higher in the case of NI, than in BI, but the difference was not so
significant in the total organics content. Concerning our experiments the minimum
dissolved organics removal in B 1 sewage varied between 10 and 25%. This is the
minimum rate, because settled samples were analyzed. The settled samples
contained about 10-30 mgr l suspended matter. This suspended matter consists of
mainly aluminum or iron(I1I)-hydroxides, but also some organics. The maximum
removal rate of dissolved organics should be a little higher than 20-25%. There are
no significant differences in the efficiency of aluminum and iron salts, taking the
molar doses into consideration.
In the case ofNI there was significant difference between the organics removal
efficiency of aluminum and iron(III) salts. Figs. 1 and 2 demonstrate that the total
organics and dissolved organics were removed much more effectively by using
aluminum salts (aluminum-sulfate rather than poly-aluminum salts) than iron(I1I)
compounds. The same effect is demonstrated in Fig. 3, where the remaining
dissolved organics (in percentage of raw sewage dissolved organic content) vs.
molar ratio of the aluminum and iron(I1I) compounds is presented.
Fig. 3 shows that dissolved organics removal could be achieved 60% by
aluminum sulfate, and 40% by feeding iron(I1I) compounds, while the remaining
CODer values were not less than 200 and 300 mgr l respectively. There is a
significant difference between the NI and B 1 cases. Figs. 2 and 3 well
demonstrate that the dissolved and total organics removal rates - provided by the
aluminum sulfate feeding - are close to each other. We have never found this high
organics removal rate concerning dissolved organics, either in international, or in
our experience previously. This fact shows that the quality of dissolved organics
plays a very important role in the removal processes.
In another experiment, the results of feeding aluminum compounds show much
poorer organics removal efficiency. Figs. 1 and 2 demonstrates that aluminum
feeding resulted in 25-40% organics removal, but the remaining CODer is not
higher than 150-200 mgrl. The molar ratio of the added aluminum compounds
varied between 1.0 and 0.6 mmolr l , while in the earlier experiment it was 2.2
mmolrl. There is no significant connection between the dose of aluminum
compounds and the removed organic content as percentage of raw sewage CODerConcerning the maximum removal rate results, the minimum remaining CODer
values are not less than 150-200 mgr l (Fig. 1). These CODer levels in chemically
treated sewage could be achieved by 40-60% organics removal efficiency. In the
case of NI the connection between the 60% removal rate and the necessary
feeding of aluminum and iron (III) compounds could be approached by linear
functions (Fig. 2).