Use of Zeolite for Removal of Ammonium Nitrogen from Reject Water

Abstract

Research work on the possibilities of adsorption/ion exchange processes use for ammonium nitrogen removal form reject water was performed. The aim of the study was to evaluate the effectiveness of ammonium nitrogen removal from reject water separated after methane digestion. Zeolites were used from ammonium nitrogen removal. Reject water was taken from municipal wastewater treatment plant of PE over 100 000. They were sampled after mechanical dewatering of digested sewage sludge. High concentrations of biogens were stated in the reject water: nitrogen concentration was equal to 893.4 mg N-NH4 +/dm3, whereas phosphorus was equal to 40.8 mg P-PO4 3‒/dm3. COD value was 276 g O2/dm 3. Reject water had brown colour and alkaline pH (pH = 7.92). Turbidity of reject water was equal to 94.1 NTU. Removal of ammonium nitrogen was performed on zeolite bed of 50 cm high and with diameter of 3.4 cm. At first model reject water was introduced into the bed. Concentration of ammonium nitrogen in model reject water was equal to 100 mg N-NH4 +/dm3 (filtration velocity 5.0 m/h). Removal efficiency of ammonium nitrogen was in the range 80÷90%. Simultaneously increase in turbidity of treated model water was observed. Further experiment were performed with reject water taken from wastewater treatment plant. Filtration velocities were equal to 3.4 and 12.7 m/h. At higher filtration velocity ammonium nitrogen removal was in the range of 20 and 52%. For the last three samples removal efficiency has set at level of 30%, As filtration velocity was lower removal efficiency of ammonium nitrogen increased to 30÷70% in subsequent portions of filtrate. Stabile results were obtained for the fifth portion of filtrate. Removal of ammonium nitrogen from reject water on zeolite beds depends on filtration velocity. As filtration velocity decreases removal efficiency of ammonium nitrogen increases. Stabile results of ammonium nitrogen removal efficiency from reject water by zeolite beds water at level of 30%. It must be emphasised that parameters of reject water differed during the experiment. As concentration of ammonium nitrogen decreased alkalinity, pH and turbidity increased. Turbidity increase was especially visible at low filtration velocities. The same trend was observed in the case of COD.