Effect of salts on a partial nitrification reactor

摘要

Wastewaters with high salt concentrations are produced in anaerobic digesters as it is the case of some fish canning factories. In the present study a partial nitrification reactor has been evaluated as post-treatment of wastewater with similar features to effluents from anaerobic digester. The effect on biomass of different salt concentrations (NaCl, KCl and Na_2SO_4) was firstly evaluated by mean of batch respirometric assay. The results show that for each salt concentration evaluated the effects were similar. During the continuos operation of the reactor, the salt concentration (NaCl) was increased from 0 to 513 mM. An increase of the ammonia oxidation activity was observed when concentration of 85 mM was added, while higher salt concentrations provoked a small decrease of activity. An important effect of the adaptation of the biomass to the saline medium was observed. For salt concentrations of 342 mM the effect of different pH was evaluated. The pH was found as an accurate control parameter of the process in order to produce an effluent with an equimolar composition of ammonia and nitrite.