Nitrification processes in stabilisation reservoirs have a major role
in improving water quality. Wastewater effluents which enter the reser
voir usually have a substantial concentration of ammonia. Oxidation of
ammonia to nitrates through nitrification processes increases the opt
ions of using the water for different purposes. The largest stabilisat
ion reservoir in Israel,. Maale Kishon reservoir, is used to store sec
ondary effluents of the Haifa treatment plant and during the summer th
e water flows into an operational reservoir which is used for irrigati
on. The operational reservoir contains large amounts of fish of differ
ent species which serve for both commercial and algal control purposes
. Thus, high ammonia concentrations in the stabilisation reservoir eff
luents may cause fish mortality in the receiving water body and are ha
rmful to the reclamation system. Laboratory experiments with the efflu
ents of the stabilisation reservoir were conducted in order to find ou
t the factors that affect nitrification processes in the reservoir and
to evaluate the reasons for the inhibition of these processes. It was
found that environmental factors have a decisive effect over nitrific
ation in the stabilisation reservoir. The most important factors are t
he temperature, solar radiation and mixing.