AMMONIA REMOVAL FROM ANAEROBICALLY TREATED PIGGERY MANURE BY ION-EXCHANGE IN COLUMNS PACKED WITH HOMOIONIC ZEOLITE

Piggery manure digested in an anaerobic fixed bed reactor was treated by ion exchange for ammonia removal using potassic zeolite (K-Zeo), ma gnesic zeolite (Mg-Zeo), sodic zeolite (Na-Zeo) and calcic zeolite (Ca -Zeo). The best results were obtained with the use of Na-Zeo. The exch ange K-NH4 was affected by the low mobility of K in the zeolite struct ure. The exchanges Ca-NH4 and Mg-NH4 were affected by the high concent ration of suspended solids and the viscosity of the influent, which le d to a low mobility of these cations in the liquid phase. The effect o f the flow rate was evaluated at bed heights of 6, 9, 18 and 27 cm for Na-Zeo. It was found that increasing the height improved the ammonia removal efficiency but the pressure drop was augmented. It was determi ned that the increase of the flow rate over 1.6 bed volumes per hour i ncreased the dispersion coefficient and reduced the exchange capacity of the bed. (C) 1997 Elsevier Science S.A.