Ammonia, iron and manganese removal from potable water using trickling filters

Pilot scale trickling filters were constructed and tested in order to study biological removal of ammonia, iron and manganese from potable water. The effect of the size of the support material on nitrification performance was studied extensively. The mean size of the gravel and hence, the specific surface area was found to be critical for optimal nitrification operation. A steady-state model developed in previous work was used to predict filter’s performance. The model was very accurate only for the gravel size for which maximum nitrification rates were observed. The effect of the operational conditions on the physico-chemical and combined physico-chemical and biological iron oxidation was also studied. It was found that the contribution of biological oxidation is significant, increasing filter’s efficiency by about 6% and reducing the required filter depth by about 40%. Manganese biological removal was studied using gravel with small mean diameter, thus providing high specific surface area. Feed concentrations up to 4.0 mg/l were treated sufficiently. Finally, experiments were performed to investigate the simultaneous removal of ammonia, iron and manganese. Experimental results showed that the combined, as well as the simultaneous removal of the aforementioned pollutants, can be achieved by single-step filtration.

Biological ammonia, iron and manganese removal using trickling filters, offers an alternative method to conventional water treatment plants. The main conclusions of this work are: • The high retention time of biomass in the filters enables high hydraulic and pollutant loadings. • The natural aeration of the filters minimizes the operational cost while achieving at the same time high removal efficiencies. • The size of the support material plays a key role for optimal ammonia removal rates. ORP Fe NH3 2.0 1.8 1.4 1.2 1.0 0.8 ORP (mV) Fe, NH3 concentration (mg/l) 1.6 0.6 0.4 0.2 0.0 Filter Depth (cm) Fig. 7. Concentrations profiles of iron and ammonia in the filter for volumetric flow rate 1000 ml/min and feed concentrations 1.1 and 1.9 mg/l, respectively.