Monitoring of biologically working trickling filters at pig fattening stables

In the present study, 154 test reports of biologically working trickling filters operating at pig fattening stables were evaluated in view of cleaning capacity and functional reliability. Basis of the evaluation were the test protocols which had been compiled with the county of Cloppenburg. Essential test criteria were ammonia reduction efficiency, removal of typical production odor and the usability of electronic logbooks (ELB). By means of these data runs of pH value and electric conductivity in the washing liquid and specific operation data as fresh water and energy consumption and elutriation rate as well were checked in view of plausibility. The results show that all trickling filters secure an ammonia separation efficiency of at least 70%. The mean separation efficiency was 93%. Raw gas typical smells in the outlet air were determined at four facilities only. 87% of the ELB was full usuable. The pH value was kept in the required range at 79% of the facilities. The electric conductivity was kept below 25 mS/cm at 90% of the facilities. Specific operation data, however, showed a wide range. The fresh water consumption varied between 0.12 and 10.41 m³ per animal place and year (m³/(AP a) and was 1.5 m³/(AP a) in mean; median = 1.1 m³/(AP a). The elutriation rate ranged between 0.07 and 2.19 m³/(AP a) and was 0.45 m³/(AP a) on average; median = 0.39 m³/(AP a). The single power consumption of the exhaust treatment system fluctuated between 1 and 51 kWh/(AP a) and was 17.6 kWh/(AP a) in mean; median = 15.4 kWh/(AP a). Compared with former investigations the cleaning capacity and the functional reliability of trickling filters have been further improved. For some facilities, there is a need for optimization in view of keeping the pH value in the required range and the general system operation as well. For example, this becomes apparent by too high fresh wate and power consumptions and elutriation rates as well. A surplus fresh water consumption may be caused by an inadequate droplet catcher function, for example. High energy consumptions is often due to inefficient circulation pumps or incorrectly dimensioned nozzles in the water distribution system. Surplus elutriation rates may result from a wrong working pH control, where the dosage of acid and base are working against each other.